HK1201385B - Systems and methods related to improved isolation between transmit and receive radio-frequency signals - Google Patents

Description

Systems and methods relating to improved isolation between transmit and receive radio frequency signals

Cross Reference to Related Applications

Priority of U.S. provisional application No.61/623, 434, filed on 12.4.2012 of the present application and entitled "SYSTEMS AND METHODS RELATED to improved assembly and rotation method TRANSMIT AND RECEIVE RADIO-FREQUENCY SIGNALS," the entire contents of which are expressly incorporated herein by reference.

Technical Field

The present disclosure relates generally to systems and methods for improving isolation between transmit and receive Radio Frequency (RF) signals.

Background

Radio Frequency (RF) devices, such as wireless devices, typically include a transmitter and a receiver for generating Tx signals and processing Rx signals, respectively. Isolation of such signals on their respective paths to and from one or more antennas is an important performance consideration. For example, isolation between Tx and Rx signals may help improve or optimize the radio communication link.

Disclosure of Invention

In some embodiments, the present disclosure relates to a system for isolating Radio Frequency (RF) signals during Tx and Rx operations. The system includes a transmit path configured to communicate a first RF signal. The system also includes a first filter disposed along the transmit path and configured to filter the first RF signal. The system also includes a first antenna connected to the transmit path and configured to transmit the first RF signal. The system also includes a second antenna connected to the receive path and configured to receive a second RF signal. The first and second antennas are spaced apart from each other to create a desired level of isolation between the transmit and receive paths.

In some embodiments, the system may further include a second filter disposed along the receive path and configured to filter the second RF signal for processing by the receiver circuit. The receive path may comprise a diversity receive path. Each of the first and second filters may include relaxed filtering requirements at least in part because of the separate first and second antennas. Relaxed filtering requirements may allow for a reduction in insertion loss for both the transmit and receive paths. The relaxed filtering requirements may include relaxed out-of-band attenuation requirements.

In some embodiments, each of the first and second filters may comprise a Band Pass Filter (BPF).

In some embodiments, the transmit path may include a power amplifier with multiple intermediate stages (intervals). In some embodiments, the first filter may be arranged at an intermediate stage and before the output stage of the power amplifier. The intermediate stage may include a variable gain stage configured to compensate for variations in insertion loss at the first filter. The variation in insertion loss may include a variation in insertion loss due to a change in frequency or temperature.

In some embodiments, the system may further include a duplexer path configured to facilitate a duplexer mode for performing both transmit and receive operations with the first antenna. In some embodiments, the system may further include a duplexer bypass and one or more switches to allow switching between a duplexer mode and a duplexer bypass mode using both the first and second antennas. The duplexer bypass mode can be used to bypass the duplexer over a selected area of dynamic range to optimize performance. In some embodiments, each of the transmit path, the receive path, and the duplexer path may include a plurality of channels for facilitating multi-band operation. In some embodiments, the multi-band operation may include quad-band (quad-band) for 3GPP communication standards.

In some embodiments, the system may further include a detection system configured to detect a condition for switching between the duplexer mode and the duplexer bypass mode. The condition may represent an antenna isolation environment. The antenna isolation environmental condition may be detected by Rx diversity measurement (measurement) analysis, forward and reflected coupled power measurement (forward and reflected coupled power measurement), direct measurement of the transmitted first RF signal, or comparison with one or more calibrated reference values.

In some embodiments, Tx and Rx operations may be performed substantially simultaneously.

According to various embodiments, the present disclosure is directed to a Radio Frequency (RF) module including a package substrate configured to house a plurality of components. The module also includes circuitry configured to provide isolation of the RF signals during Tx and Rx operations. The circuit includes a transmit path configured to pass a first RF signal, a first filter disposed along the transmit path and configured to filter the first RF signal, and a transmit node for connection to a first antenna to transmit the first RF signal. The circuit also includes a receive path configured to receive a second RF signal from the second antenna. The transmit path and the receive path are configured to produce a desired level of isolation therebetween. The module also includes a plurality of connectors configured to provide electrical connections between the circuit and the package substrate.

In various embodiments, the present disclosure relates to a Radio Frequency (RF) device including a transceiver configured to process RF signals. The RF device also includes first and second antennas in communication with the transceiver to facilitate transmission and reception of RF signals. The RF device also includes circuitry configured to provide isolation of RF signals during Tx and Rx operations. The circuit includes a transmit path configured to pass a first RF signal, a first filter disposed along the transmit path and configured to filter the first RF signal, and a transmit node for connection to a first antenna to transmit the first RF signal. The circuit also includes a receive path configured to receive a second RF signal from a second antenna. The transmit path and the receive path are configured to produce a desired level of isolation therebetween.

According to some embodiments, the present disclosure relates to a method for isolating Radio Frequency (RF) signals during Tx and Rx operations. The method includes communicating a first RF signal through a transmit path. The method also includes filtering the first RF signal along a transmit path. The method also includes communicating the first RF signal to a first antenna to transmit the first RF signal. The method also includes receiving a second RF signal via a second antenna. The method also includes passing a second RF signal through the receive path. The first and second antennas are spaced apart from each other to create a desired level of isolation between the transmit and receive paths.

In some embodiments, the present disclosure relates to methods for manufacturing devices with isolated circuits. The method includes forming or providing a transmit path. The method also includes forming or providing a filter along the transmit path. The method also includes forming or providing a connection between the transmit path and the first antenna to allow transmission of the first RF signal. The method also includes forming or providing a receive path connected to the second antenna such that the transmit and receive paths are isolated to a desired level.

For the purposes of summarizing the disclosure, certain aspects, advantages and novel features of the invention have been described herein. It is to be understood that not necessarily all such advantages may be achieved in accordance with any particular embodiment of the invention. Thus, it is to be understood that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.

Drawings

Fig. 1 schematically shows an isolation circuit.

Fig. 2 shows that the isolation circuit of fig. 1 may be implemented in a filtering configuration.

Figure 3 illustrates an example duplexer configured to provide Tx-Rx isolation, Tx-antenna isolation, and antenna-Rx isolation.

Fig. 4 illustrates a process that may be implemented to provide antenna-to-antenna isolation for a Radio Frequency (RF) system having first and second antennas.

Fig. 5A illustrates a process that may be implemented to implement the transmit portion of the RF system of fig. 4.

Fig. 5B illustrates a process that may be implemented to implement the receive portion of the RF system of fig. 4.

Fig. 6 shows an example RF system with separate Tx and Rx antennas in communication with Tx and Rx paths, respectively, where each path includes a filter such as a bandpass filter.

Fig. 7 illustrates a process that may be implemented to filter a partially amplified RF signal to be transmitted.

Fig. 8 shows an example RF system with separate Tx and Rx antennas in communication with Tx and Rx paths, respectively, where the Tx path has a power amplifier chain and a bandpass filter in the power amplifier chain.

Fig. 9 illustrates a process that may be implemented to enable the reception of RF signals via multiple antennas.

Fig. 10 illustrates a process that may be implemented to select a reception mode among the reception modes of fig. 9.

FIG. 11 illustrates a process that may be implemented to implement the changes associated with the selection process of FIG. 10.

Fig. 12 illustrates an example RF system having multiple antennas and configured to facilitate various functions related to the processes of fig. 9-11.

Fig. 13 illustrates an example multi-band RF system configured to implement one or more features of the present disclosure.

Fig. 14 schematically illustrates that an isolation circuit having one or more features of the present disclosure may be implemented in one or more modules.

Fig. 15 schematically illustrates that an isolation circuit having one or more features of the present disclosure may be implemented in an RF device.

Fig. 16 schematically illustrates an example wireless device having one or more features of this disclosure.

Detailed Description

The headings, if any, are provided herein for convenience only and do not necessarily affect the scope or meaning of the claimed invention.

Disclosed herein are systems and methods relating to improved isolation between Radio Frequency (RF) signals. Fig. 1 shows an isolation circuit 10 configured to receive and output a first RF signal (RF1)12 (e.g., a transmit signal), and also to receive and output a second RF signal (RF2)14 (e.g., a receive signal). For purposes of illustration herein, RF1 and RF2 will be described in the context of transmitting and receiving signals, respectively. However, it should be understood that one or more features of the present disclosure may also be implemented in other RF signal isolation scenarios.

Fig. 2 illustrates that in some embodiments, the isolation circuit 10 of fig. 1 may be implemented in a filtering arrangement 20. Such a configuration is shown as providing for the communication of a transmit (Tx) signal 22 and a receive (Rx) signal 24. Various non-limiting examples of the filtering arrangement 20 described herein may provide improved isolation between the Tx and Rx signals 22, 24.

Isolation between Tx and Rx signals may facilitate improvement or optimization of radio communication links, such as those involving significant out-of-band noise and spurious (spurious) filtering. As an example, a Frequency Division Duplex (FDD) system may include transmit (Tx) and receive (Rx) circuitry operating simultaneously but at different frequency bands in the same radio. Interference of the transmitted transmitter carrier power along with the transmitter's noise and spurious out-of-band signals can compromise the receiver's ability to accurately demodulate the desired incoming signals, especially when they are at low power and near the sensitivity limit at which Rx can resolve them.

Fig. 3 illustrates an example duplex filtering configuration 50 that may be implemented to isolate these effects of the transmitter from the sensitive input of the receive chain. A transmit signal from a Tx circuit (not shown) may be received at input node 52 for amplification by amplifier 54. The amplified transmit signal is shown passing through duplexer 56 to be transmitted via antenna 60. The same antenna 60 may receive an incoming signal that passes through the duplexer 56 and is routed to Rx circuitry (not shown) via node 58.

The duplexer filter 56 depicted in fig. 3 may provide a variety of functions. On the transmit side, out-of-band noise and spurious signals may be attenuated en route to the antenna, for example to avoid radiation violations that are compliant with the requirements of cell planning and standards bodies. On the receive side, similar filtering of out-of-band noise and spurious signals of the Rx band may be attenuated from the antenna, e.g., to avoid or reduce performance degradation in the Rx circuitry. The duplex filter 56 may be configured such that coupling the Tx and Rx filters together can enhance the isolation characteristics directly between the Tx and Rx, and further isolate the Rx directly from the Tx carrier and noise.

The disadvantages associated with the duplexer filter configuration of fig. 3 may include, for example, relatively large size and increased electronics solution area. Duplexer filter configurations may also significantly increase the cost of a given application frequency band, and such duplexer filtering is typically associated with each frequency band using FDD operation. Thus, the cost problem may be amplified by the number of frequency bands in the whole radio device. Furthermore, such a configuration may be lossy in the passband of Tx (resulting in transmitting higher power to overcome Tx filter insertion loss) and lossy in the passband of Rx (resulting in further degradation of the noise floor of the receiver).

To achieve some or all of the limitations of one or more isolation performance design parameters of a duplex filter, the passband of Tx and the passband of Rx can typically be made more lossy than if the filters were separate Tx and Rx filters. The coupling, loading, and matching associated with the tuning of the 3-terminal duplexer (Tx, Rx, and Ant) may increase losses that are greater than or beyond the losses of the filters when they are separated; and even more so in some cases of large isolation requirements.

In some embodiments, the Tx and Rx circuits may be isolated by removing the duplexer and replacing it with a separate Tx filter and a separate Rx filter instead. Furthermore, the Tx and Rx paths may be connected to separate dedicated Tx and Rx antennas. Fig. 4 shows a process 100 that may be implemented to achieve such an isolation configuration provided with first and second antennas. Fig. 5A and 5B illustrate processes 110, 120 that may be implemented to implement separate filtering of signals associated with Tx and Rx circuits. Fig. 6 shows an example configuration 200 in which such separate filters may be implemented with separate antennas to provide isolation between Tx and Rx circuitry.

Process 100 of fig. 4 shows that in block 102, a first path for transmitting with a first antenna may be formed. In block 104, a second path for reception with a second antenna may be formed to provide antenna-to-antenna isolation. In some embodiments, the first antenna may be a dedicated transmit antenna configured to facilitate transmission of one or more frequency bands of transmit RF signals.

The process 110 of fig. 5A shows that in block 112, the RF signal to be transmitted may be amplified. In block 114, the amplified RF signal may be filtered by a first filter. In block 116, the filtered RF signal may be provided to a transmit antenna.

Process 120 of fig. 5B shows that in block 122, the RF signal received from the receive antenna may be filtered by a second filter. In some embodiments, the second filter may be a separate filter from the first filter that filters the RF signal to be transmitted. In block 124, the filtered RF signal may be provided to a receiver circuit.

Fig. 6 shows a configuration 200 that may be an example of the isolation circuit 10 of fig. 1. The example configuration 200 is shown to include separate antennas 208, 218, where one (208) is used for transmission and the other (218) is used for reception. The transmit antenna 208 is shown receiving a filtered RF signal from the filter 206 (e.g., a band pass filter). Filter 206 is shown receiving an amplified RF signal from amplifier 204, which in turn receives an RF signal to be transmitted from a Tx circuit (not shown) through input node 202. For purposes of illustration, the example power amplifier 204 may include multiple stages (e.g., input, intermediate and output stages 220, 222, 224, 226, 228, 230, 232).

The receive antenna 218 of the example configuration 200 is shown providing a received RF signal to the filter 216 (e.g., a band pass filter). The filtered received RF signal is shown as being passed to Rx circuitry (not shown) through Rx node 212.

In some embodiments, separate antennas 208, 218 may be used to further isolate the Tx and Rx paths. In some embodiments, for a particular level of antenna isolation, the Tx carrier and noise power may be suppressed to at least approximately the same level as the duplexer-based configuration described herein with reference to fig. 3. The example configuration 200 may have less in-line insertion loss on both the Tx and Rx portions because the configuration may experience less DC current consumption and transmit power, and less insertion loss and noise figure degradation on the Rx path.

Exemplary benefits in the context of filter insertion loss provided by the configuration of fig. 6 may include: the benefits associated with a SAW (surface Acoustic wave) filter based duplexer designed for Tx operating bands in the range of approximately 1850 MHz-1910 MHz, where the worst case Tx filter in-band insertion loss is approximately 3dB, while the attenuation of out-of-band Tx noise at Rx frequencies (approximately 1930 MHz-1990 MHz) can be as large as approximately 50 dB. If the same bandpass filter is not limited with large isolation requirements, it can reach a worst case loss of about 2dB and an isolation of about 30dB in the Rx band. Similarly, the Rx performance of the duplexer may produce a worst-case insertion loss of about 3.5dB from antenna to Rx, and attenuation of the Tx carrier frequency as large as about 55 dB. If the same bandpass Rx filter is not constrained with large isolation requirements, it can reach a worst case insertion loss of about 2dB and an isolation of about 30dB in the Tx band.

In some embodiments, the isolation of the antenna may be made about 20dB (considering switching and implementation losses) for a separate filter that provides approximately equal Tx to Rx isolation as the example duplexer performance, and then the system may be limited by the Tx carrier isolation of Rx filtering. In some configurations, saving 1dB of Tx filter loss in this example can translate into reducing DC current by at least 20% at maximum power in the transmitter, mainly because the Power Amplifier (PA) outputs 1dB less power before the filter. According to other de-sensitization from Tx carrier power and Rx linearity characteristics, the Rx noise figure can be reduced by up to 1dB because the front-end insertion loss of the path is reduced by 1 dB.

In some embodiments, the desired characteristics of lower post-PA Tx insertion loss and maintaining duplex spacing isolation performance may be achieved by the circuit 400 shown in fig. 8. Such circuitry may operate through the process 300 shown in fig. 7. In block 302, the RF signal to be transmitted may be partially amplified. In block 304, the portion of the amplified RF signal may be filtered. In block 306, the filtered RF signal may be further amplified to produce an output RF signal. In block 308, the output RF signal may be provided to a transmit antenna.

In the example isolation circuit 400 of fig. 8, a Power Amplifier (PA)404 is shown to include a plurality of intermediate stages and an output stage (e.g., 420, 422, 424, 426, 428, 430, 432, 434). The input node 402 may receive an RF signal to be amplified, and the amplified RF signal may be provided to the Tx antenna 208. The receive antenna 218 of the example configuration 400 is shown providing a received RF signal to the filter 216 (e.g., a band pass filter). The filtered received RF signal is shown as being passed through the Rx node 212 to Rx circuitry (not shown).

In the example configuration 400, the Tx Band Pass Filter (BPF) after the PA 404 (e.g., such as in the example shown in fig. 6) may be removed, and the BPF 40 may instead be placed in an intermediate stage before the output stage. In the example shown, the BPF 406 is placed between the second intermediate stage and the output stage. In some embodiments, the output stage may dominate the current consumption, since in the previous examples a strong dependence of the DC current on the output power is demonstrated. To further remove losses after the PA, the filter can be moved to an intermediate stage to provide the desired impact on current and noise performance.

In some embodiments, placing filter 406 before output stage 432 may have a significant effect. For example, the power into the filter may be at least 10 times lower, allowing for relaxation of production requirements and possibly smaller sizes for lower power handling ratings (power handling). Furthermore, the efficiency impact (efficiency impact) can be greatly reduced on the output stage and remain substantially the same for the driver stage.

In some embodiments, because the isolation constraint is relaxed, the filter 406 itself may be improved to obtain lower insertion loss, and the noise contribution of everything before the last stage of the PA 404 may be largely filtered out, so that only the last stage effectively contributes noise to the PA output. By inserting the BPF 406 filter into the PA array (lineup) for the specific example shown in tables 1A-1D, the noise at the output of the PA drops from approximately-135 dBm/Hz to-149 dBm/Hz. Table 1A corresponds to stage 1 of the configuration where the BPF is located after the PA output to produce a post-PA Tx DPX insertion loss of 3dB (where Vcc ═ 3.4V). Table 1B corresponds to stage 2 of the configuration of table 1A, where the total Icc is about 404.61 mA. Table 1C corresponds to stage 1 of the configuration that provides an intermediate stage BPF to produce 2dB of intermediate stage filtering before the output stage of the PA. Table 1D corresponds to stage 2 of the configuration of table 1C, where the total Icc is about 212.59 mA. For the intermediate stage BPF of table 1C, the fTx component has an attenuation of about 2dB when combined with stage 1 to produce a net gain of about 14 and a net power of about 13 dBm. For the fRx component, the intermediate stage BPF has an attenuation of about 30dB, a net gain of about 14, and a net noise of about-172.54 when combined with stage 1.

	Gain 1(dB)	NF1	Noise 1	Pout1(dBm)	Eff1	Icc1(mA)
							fTx	16			16	35	33.45
fRx	16	10	-148

TABLE 1A

	Gain 2(dB)	NF2	Noise 2	Pout2(dBm)	Eff2	Icc2(mA)
							fTx	12			28	50	371.15
fRx	12	12	-135.83

TABLE 1B

	Gain 1(dB)	NF1	Noise 1	Pout1(dBm)	Eff1	Icc1(mA)
							fTx	16			15	35	26.57
fRx	16	10	-148

TABLE 1C

	Gain 2(dB)	NF2	Noise 2	Pout2(dBm)	Eff2	Icc2(mA)
							fTx	12			25	50	186.02
fRx	12	12	-149.633

TABLE 1D

Given the duplexer Tx to Rx isolation of the standard architecture in the range of about 50dB, the noise back to the Rx input for this standard approach would be about-185 dBm/Hz. To achieve the same noise power level as the example configuration of fig. 8, the antenna isolation must be up to 31dB (including the Insertion Loss (IL) of the front end components on both the Tx and Rx paths before reaching the Rx input pin). This can be challenging and typically needs to be maintained under conditions of antenna loading and other operating variables; this is believed to be achievable and should improve with the development of orthogonal antenna designs and further isolation innovations.

Also of interest in the examples of tables 1A-1D is the actual amount of DC current saved by implementing the BPF in the PA and saving 2dB of loss after the PA. For the particular example shown, the standard method (tables 1A and 1B) would consume approximately 405mA, while the new method (tables 1C and 1D) would only consume approximately 213mA, saving approximately 192mA at maximum power.

Equivalent intrinsic PA efficiencies are also calculated in tables 1A-1D, which standard PAs would require to have approximately 87% PAE in their output stages to reach this 213mA value for an output power of 28 dBm. Such PAEs are a significant technical improvement over current technology. In some embodiments, such improvements may be achieved by implementing architectural configurations having one or more of the features described herein.

Another significant feature of the example configuration 400 of fig. 8 is that it may enable the input stage (e.g., 422) of the PA 404 to adjust in a manner that its gain and output power compensate for any roll-off in the intermediate stage BPF 406. The roll-off of this filter may be less at the band edges than a standard duplexer filter, but the adjustment of the gain of the first stage (by a variety of techniques including, but not limited to, digital control words to control biases from the serial digital interface, etc.) may be compensated without disturbing the subtle balance of non-linear gain reduction and expansion that allows subsequent stages to meet efficiency and linearity objectives. It can also compensate for the known temperature behavior of roll-off and filter insertion loss at the band edges by this method. These compensations may be more difficult if the limits on the PA output stage are given for maximum power and back-off from saturation; therefore, after the last stage of the PA, it is desirable to have smaller losses, also for this reason.

In some implementations, one or more features associated with the example configuration 400 of fig. 8 may be combined with one or more features associated with the example configuration 50 of fig. 3. Fig. 12 shows a configuration 600 that may be an example of such a combination. Fig. 9 illustrates a process 500 that may be implemented to form such a configuration. Fig. 10 illustrates a process 510 that may be implemented to determine in which mode to operate and to switch between multiple modes associated with the configuration 600. Fig. 11 shows a process 520 that may be implemented to determine conditions for performing a handover of the example process 510 of fig. 10.

In block 502 of the process 500 of fig. 9, a duplexer path may be provided or formed for transmitting and receiving RF signals via the first antenna. In block 504, a diversity receive path may be provided or formed for receiving the RF signal through the second antenna. Examples of such different paths and their corresponding antennas will be described in more detail with reference to fig. 12.

In block 512 of process 510 of fig. 10, a determination may be made as to whether to operate in duplexer mode or diversity receive mode. In block 514, one or more switching operations may be performed to facilitate the selected mode of operation. Examples of such different modes and switching operations will be described in more detail with reference to fig. 12.

In block 522 of process 520 of fig. 11, a condition for triggering a change in operating mode may be detected. In block 524, a signal may be generated to perform one or more switching operations to change the mode of operation. An example of such detection and switching operations will be described in more detail with reference to fig. 12.

In some cases (e.g., given limitations in antenna isolation performance or only the number of antennas available), antennas for Tx only may not be allocated and it may become necessary to maintain a standard duplexer path after the PA (404), as shown in fig. 12. However, even in this case, one or more features associated with the configuration 400 described with reference to fig. 8 may be implemented to benefit from performance improvements, for example, on current consumption and Rx noise.

In the example configuration 600 of fig. 12, the PA 404 is described as similar to the example described with reference to fig. 8. However, it should be understood that other PA configurations may also be used in the configuration 600 of fig. 12.

The PA 404 is depicted as receiving an RF signal through its input node 602 and filtering the signal before the output stage as described with reference to fig. 8. When operating in duplexer mode, the output of PA 404 may then be routed to duplexer path 610, through duplexer 612, and then to transmit antenna 608. When in duplexer mode, RF signals received through antenna 608 may be routed through duplexer 612 and then to receive node 614. To facilitate the duplexer mode of operation, a switch 634 (e.g., SP2T) may be set to form a connection between the PA 404 and the duplexer 612, and a switch 636 (e.g., SP2T) may be set to form a connection between the antenna 608 and the duplexer 612.

When in a mode in which it is desired to bypass duplexer 612 (e.g., for diversity Rx mode as described herein), switch 634 may be set to break the path between PA 404 and duplexer 612 and form a connection between PA 404 and a duplexer bypass, where the duplexer bypass is shown as being connected to one throw of switch 636. Switch 636 may be set to shunt the duplexer to antenna 608 to allow transmission of filtered and amplified RF signals from PA 404, and to disconnect the path between antenna 608 and duplexer 612 to disable (disable) the receive function of duplexer 612.

In such a mode (e.g., diversity mode), a separate Rx antenna 218 is shown providing the received RF signal to a diversity Rx path 620. Such a path may include a filter 216 (e.g., BPF) to allow filtering of the received signal and providing the filtered signal to the receiving node 212 in a manner similar to that described with reference to fig. 8.

In some embodiments, the configuration shown in fig. 12 may be used to facilitate, for example, emerging communication standards in which increased use of diversity may include the addition of additional Rx paths. The separate antenna connections are typically configured to be sufficiently separated in distance to be considered different RF environments and paths so that the received RF signal can then be correlated with the main path Rx to obtain a signal-to-noise ratio (SNR) advantage. The SNR may be improved by a relatively large amount (e.g., 3dB or more) if the two signals are substantially orthogonal and received at substantially the same power level. The driving for such performance may include a desire for better Rx sensitivity, and the benefits of separation and having a level of isolation between antennas may also benefit some or all of the goals associated with the example configuration 600 of fig. 12.

In some embodiments, when the diversity Rx path 620 is not used to enhance SNR at reduced or lowest signal levels, the diversity Rx path 620 may be used to facilitate separate Tx and Rx antennas as described herein. The diversity path 620 may be used as a stand-alone (lone) Rx path with antenna 218 and the other antenna 608 may be used for Tx only. Similar to the example of fig. 8, the configuration of fig. 12 may include a "duplexer bypass" path as described herein, which may be switchably selected to eliminate the loss of the post-PA duplexer and to reduce the overall PA output noise using a PA with an intermediate stage embedded BPF before the final stage. Furthermore, there is a challenge with noise level with reduced post-PA filtering, and there is a limit at antenna isolation of, for example, about 31dB, as described herein. However, the exemplary 3dB savings in post-PA losses may reduce the DC consumption of the PA by approximately 50%.

In some embodiments, the isolation of the switches (634, 636) on either end of the duplexer bypass path may be configured such that their sum is greater than the isolation of the duplexers Tx-Ant themselves, or the overall performance of the duplexer 612 may degrade when the duplexer 612 is actively used. In some embodiments, these relatively high isolation switching requirements can be traded off against insertion loss on the blades of those switches and the large DC current savings to be obtained, and can be achieved at a worst case of about 30-35dB, for example.

In some embodiments, the architecture of fig. 12 may be configured such that it may be used at different points throughout the dynamic range. For example, starting at the maximum power at which Tx carrier attenuation and noise may be most severe, one may trade off the usability of the duplexer when necessary or desirable to meet the noise requirements. Where the noise requirements can be relaxed for self-desensitization and the system can have a margin of back-off power relative to the requirements, the duplexer can be bypassed to obtain a large current saving there. Such methods may have less benefit for maximum power DC currents (where they are at their maximum), but may still have significant benefit when used. As an example, and in the statistical context, the WCDMA (wideband code division multiple access) standard is one example where the majority of the time Tx operation is significantly backed off from maximum power, so that the advantages of the foregoing approach can make a substantial difference. Such an advantage may be less important for LTE in current cell planning construction; but with capacity driven pico-cells (pico-cells) and smaller cell coverage areas (small cell footprints), the transmit power may drop in mature systems, making this example solution more chance to gain advantage.

In some embodiments, the architecture of fig. 12 may be configured to accommodate situations where antenna isolation is important to system performance and varies operationally depending on load. As illustrated in fig. 12, the system detects the degree of antenna coupling (e.g., through diversity reception and SNR analysis, forward and reflected coupler measurements on the antenna feed (feed), direct probing of Tx arriving through the diversity path relative to an initial calibration reference value, or other such similar techniques) and can feed back this information to set the control of the duplexer bypass path to be used or not used depending on knowledge of the antenna environment. The foregoing system is schematically illustrated in fig. 12 as 630, and the use and non-use of duplexer bypass may be implemented, for example, by a switch controller 632 that controls the state of switches 634, 636 based on information provided by the system 630. In some embodiments, such a system and/or bypass controller may be implemented by a baseband driven front end serial digital interface or transceiver from controlling the PA, switches, and other active (active) circuitry of the front end.

Fig. 13 shows an architecture 700 that is similar to the example of fig. 12, but is configured to accommodate multiple frequency bands. The example architecture 700 is described in the context of an example 3GPP quad-band configuration. However, it should be understood that the number of frequency bands may be more or less than four. Additionally, one or more features associated with the multi-band example 700 may be implemented in other wireless standards.

In the example configuration 700, the PA 704 is shown receiving an RF signal to be transmitted through the input node 702 and amplifying the signal at different stages (750, 752, 754, 756, 758, 764, 766, 768). As with the example described with reference to fig. 12, filtering may be performed before the output stage of the PA. In the illustrated example, the filter bank 706 is shown with multiple filters to accommodate different frequency bands. Filter 760a (e.g., BPF) is shown to provide filtering for band B1, filter 760B (e.g., BPF) is shown to provide filtering for band B2, and filter 760c (e.g., BPF) is shown to provide filtering for bands B3 and B4. It should be understood that the filter bank 706 may be configured differently with a different number of filters. A given signal may be routed to a selected one of such filters via a switch 762 (e.g., an SP3T switch) to produce a desired filtered signal.

Similar to the example of fig. 12, the filtered and amplified signal output from the PA 704 may be routed to a duplexer path (collectively denoted as 710) or a duplex bypass path 740. The duplexer path 710 is shown to include separate duplexers (712a, 712B, 712c, 712d) for four example frequency bands B1, B2, B3, B4. On the PA side, each duplexer is shown as being connectable to the PA output through a switch 734 (e.g., an SP5T switch). On the transmit antenna side, each duplexer is shown as being connectable to a first antenna 708 through a switch 736 (e.g., an SP5T switch). On the receive side, each duplexer is shown connected to a respective Rx node 714. It should be understood that the duplexer path 710 may be configured differently to have a different number of frequency bands.

Similar to the example of fig. 12, when duplexer operation is not desired, the output of the PA (of the selected frequency band) may be routed to duplexer bypass 740 through appropriate settings of switches 734, 736 to pass the signal to the first antenna for transmission. For Rx signals, multiple band channels and their corresponding Rx paths 720 (e.g., diversity Rx paths) may be provided. In the example shown, the second antenna 718 is shown as being connectable to a different filter (e.g., BPF) of the filter bank 724 through a switch 728 (e.g., SP3T switch) to provide for selection of a frequency band. Three example filters 726a, 726B, 726c are shown as accommodating three example channels (B1+ B4, B2, B3), and signals from such channels may be routed to their respective Rx nodes 722. It should be understood that the Rx path 720 and its corresponding filters may be configured differently with different numbers of bands and filters.

In some embodiments, the four example frequency bands B1-B4 depicted in the example architecture 700 of fig. 13 may include the 3GPP frequency bands listed in table 2. The various values listed in table 2 are approximate.

Frequency band	Tx	Rx
			B1	1920-1980MHz	2110-2170MHz
B2	1850-1910MHz	1930-1990MHz
			B3	1710-1785MHz	1805-1880MHz
B4	1710-1755MHz	2110-2155MHz

TABLE 2

Note that for this example embodiment, the Tx bands of B3 and B4 substantially overlap, and the Rx bands of B1 and B4 substantially overlap, enabling some merging of the filters and their respective paths. Such incorporation is described by way of example with reference to fig. 13.

In some embodiments, the merging may also be implemented for the functionality provided by the duplexer. For example, the divided duplexer shown in fig. 13 may be replaced as follows. The B1 and B4 duplexers may be replaced by triplexers (triplexers) of B1Tx/B4Tx/B1B4Rx, and/or the B3 and B4 duplexers may be replaced by triplexers of B3B4Tx/B3Rx/B4 Rx. In another example, the merging may be further extended, where the B1, B3, and B4 duplexers may be replaced by quadplexers (quadplexers) of B1Tx/B3B4Tx/B3Rx/B1B4 Rx. In some cases, the incorporation of the aforementioned filters may increase the insertion loss of the filter, thereby making the bypass characteristic more attractive.

In some embodiments, the use of duplexer bypass over dynamic range may result in additional complexity associated with many modern communication systems that require precise power steps in response to requests from node bs or base stations. To maintain consistent gain stepping while making such significant changes in the output impedance presented to the PA and Tx path insertion loss, careful calibration and/or real-time corrections can be implemented to manage the accuracy of gain changes with, for example, power, frequency, VSWR, and/or temperature.

In some embodiments, the overall system cost, size, and/or performance overhead of the duplexer bypass features described herein may be implemented to be manageable. Such embodiments may include additional one or more poles (poles) on one or more switches and desired isolation performance on such switches and between antennas, as well as additional one or more BPF filters and one or more switches embedded in the intermediate stage of the PA. In some embodiments, the increase in cost and size of the PA due to such implementations may be weighed against the potential benefits of improved DC power consumption and efficiency.

Fig. 14 illustrates that in some embodiments, an isolation circuit 10 having one or more of the features described herein can be part of a packaged module 800. The module 800 may also include a packaging substrate, such as a laminate substrate, configured to house a plurality of components. The module 800 may also include one or more connections that facilitate providing signals to and from the isolation circuit 10. The module 800 may also include various packaging structures 804. For example, an over mold structure (over mold structure) may be formed on the isolation circuit 10 to provide protection against external elements.

In some embodiments, one or more features of the present disclosure may be implemented in one or more modules. For example, some or all of the functionality associated with the isolation circuit 10 may be implemented in a PA module, a front end module, or some combination thereof.

In some embodiments, the isolation circuit 10 as part of the module 800 may be implemented on one or more semiconductor die. In some embodiments, module 800 may include a front end module configured for use in an RF device, such as a wireless device.

Fig. 15 shows that in some embodiments, a module 800 with isolation circuitry 10 may be included in an RF device 810, such as a wireless device. Such wireless devices may include, for example, cellular telephones, smart phones, and the like. In some embodiments, the isolation circuit 10 may be implemented in a packaged module such as the example of fig. 14. RF device 810 is depicted as including other common components such as transceiver circuitry 812. In some embodiments, RF device 810 may include multiple antennas 814 to facilitate the antenna-to-antenna isolation functions described herein.

In some implementations, architectures, devices, and/or circuits having one or more of the features described herein can be included in an RF device, such as a wireless device. Such architectures, devices, and/or circuits may be implemented directly in a wireless device, in one or more modular forms as described herein, or in some combination thereof. In some embodiments, such wireless devices may include, for example, cellular phones, smart phones, handheld wireless devices with or without phone functionality, wireless tablets, wireless routers, wireless access points, wireless base stations, and the like.

Fig. 16 schematically illustrates an example wireless device 900 having one or more advantageous features described herein. In some embodiments, such advantageous features may be implemented in the PA module 912, may be implemented in the Front End (FE) module 914, may be implemented with one or more antennas 916, or may be implemented in some combination thereof.

The PAs in PA module 912 may receive their respective RF signals from transceiver 910 and process the received signals, where the transceiver 910 may be configured and operated in a known manner to produce RF signals to be amplified and transmitted. A transceiver 910 is shown interacting with the baseband subsystem 908, wherein the baseband subsystem 908 is configured to provide conversion between data and/or voice signals appropriate for a user and RF signals appropriate for the transceiver 910. The transceiver 910 is also shown connected to a power management component 906, the power management component 906 configured to manage power for operation of the wireless device 900. Such power management may also control the operation of the baseband subsystem 908 and other components of the wireless device 900.

The baseband subsystem 908 is shown connected to the user interface 902 to facilitate various inputs and outputs of voice and/or data provided to and received from the user. The baseband subsystem 908 may also be connected to memory 904 that is configured to store data and/or instructions to facilitate operation of the wireless device and/or to provide information storage for a user.

In the example wireless apparatus 900, the output of the PA module 912 is shown as being provided to the FE module 914. Functions such as band selection may be implemented in the FE module 914. In fig. 16, the received signal is shown routed from the FE module to one or more Low Noise Amplifiers (LNAs) 918. The amplified signal from LNA 918 is shown routed to transceiver 910.

Many other wireless device configurations may use one or more of the features described herein. For example, the wireless device need not be a multi-band device. In another example, the wireless device may include additional antennas, such as diversity antennas, and additional connectivity features, such as Wi-Fi, bluetooth, and GPS.

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is, it is to be interpreted in the meaning of "including, but not limited to". As generally used herein, the term "coupled" refers to two or more elements that may be connected directly or through one or more intermediate elements. Moreover, as used in this application, the words "herein," "above," "below," and words of similar import shall refer to this application as a whole and not to any particular portions of this application. Words in the above detailed description using the singular or plural number may also include the plural or singular number, respectively, as the context permits. The word "or" when referring to a list of two or more items covers all of the following interpretations of the word: any item in the list, all items in the list, and any combination of items in the list.

The above detailed description of embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise form disclosed above. While specific embodiments of, and examples for, the invention are described above for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. For example, while processes or blocks are presented in a given order, alternative embodiments may perform routines having steps, or employ systems having blocks, in a different order, and some processes or blocks may be deleted, moved, added, subdivided, combined, and/or modified. Each of these processes or blocks may be implemented in a number of different ways. Further, while processes or blocks are sometimes shown as being performed in series, these processes or blocks may alternatively be performed in parallel, or may be performed at different times.

The teachings of the invention provided herein may be applied to other systems, not necessarily the systems described above. The elements and acts of the various embodiments described above can be combined to provide further embodiments.

While certain embodiments of the present invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the present disclosure. Indeed, the novel methods and systems described herein may be embodied in various other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the disclosure. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosure.

Claims (18)

1. A system for isolating radio frequency signals during transmit and receive operations, the system comprising:

a transmit path configured to convey a first radio frequency signal, the transmit path including a power amplifier having a plurality of intermediate stages;

a first filter arranged at an intermediate stage and before the output stage of the power amplifier and configured to filter the first radio frequency signal;

one or more switches;

a first antenna connected to the transmit path and configured to transmit the first radio frequency signal via the one or more switches;

a second antenna connected to the receive path and configured to receive a second radio frequency signal, the first and second antennas being spaced apart from each other to provide isolation between the transmit and receive paths; and

a duplexer path configured to facilitate a duplexer mode that performs both transmit and receive operations with the first antenna, and a duplexer bypass, the one or more switches configured to allow switching between the duplexer mode and the duplexer bypass mode using both the first and second antennas.

2. The system of claim 1, further comprising: a second filter disposed along the receive path and configured to filter the second radio frequency signal for processing by the receiver circuit.

3. The system of claim 2, wherein the receive path comprises a diversity receive path.

4. The system of claim 2, wherein each of the first and second filters includes relaxed filtering requirements due at least in part to the separate first and second antennas, the relaxed filtering requirements allowing for a reduction in insertion loss for both transmit and receive paths.

5. The system of claim 4, wherein the relaxed filtering requirements include relaxed out-of-band attenuation requirements.

6. The system of claim 2, wherein each of the first and second filters comprises a Band Pass Filter (BPF).

7. The system of claim 1, wherein the intermediate stage comprises a variable gain stage configured to compensate for variations in insertion loss at the first filter.

8. The system of claim 7, wherein the change in insertion loss comprises a change in insertion loss due to a change in frequency or temperature.

9. The system of claim 1, wherein the duplexer bypass mode is used to bypass the duplexer over a selected region of dynamic range to optimize performance.

10. The system of claim 9, wherein each of the transmit path, receive path, and duplexer path includes a plurality of channels for facilitating multi-band operation.

11. The system of claim 10, wherein the multi-band operation comprises a quad-band for a 3GPP communication standard.

12. The system of claim 1, further comprising: a detection system configured to detect a condition for switching between a duplexer mode and a duplexer bypass mode.

13. The system of claim 12, wherein the condition represents an antenna isolation environment.

14. The system of claim 13, wherein the antenna isolation environment condition is detected by receive diversity measurement analysis, forward and reflected coupled power measurements, direct measurement of the transmitted first radio frequency signal, or comparison to one or more calibrated reference values.

15. A radio frequency device, comprising:

a transceiver configured to process a radio frequency signal;

first and second antennas in communication with the transceiver to facilitate transmission and reception of the radio frequency signal; and

circuitry configured to provide isolation of the radio frequency signal during transmit and receive operations, the circuitry comprising a transmit path including a power amplifier having a plurality of intermediate stages and configured to pass a first radio frequency signal, a first filter disposed at one of the intermediate stages and before an output stage of the power amplifier and configured to filter the first radio frequency signal, and one or more switches connecting the transmit path to a first antenna, the circuit also includes a receive path configured to receive a second radio frequency signal from the second antenna, the circuit also includes a duplexer path configured to facilitate a duplexer mode for performing both transmit and receive operations with the first antenna, and a duplexer bypass, the one or more switches are configured to allow switching between a duplexer mode and a duplexer bypass mode using both the first and second antennas.

16. A method for isolating radio frequency signals during transmit and receive operations, the method comprising:

passing a first radio frequency signal through a transmit path, the transmit path including a power amplifier having a plurality of intermediate stages;

filtering the first radio frequency signal at an intermediate stage and before the output stage of the power amplifier;

passing the first radio frequency signal through one or more switches to a first antenna to transmit the first radio frequency signal;

receiving a second radio frequency signal through a second antenna;

passing the second radio frequency signal through a receive path, the first and second antennas being spaced apart from each other to provide isolation between the transmit and receive paths; and

controlling a state of the one or more switches to control switching between a duplexer mode in which both transmit and receive operations are performed with the first antenna and a duplexer bypass mode in which both the first and second antennas are used.

17. A radio frequency module, comprising:

a package substrate configured to accommodate a plurality of components;

circuitry configured to provide isolation of the radio frequency signal during transmit and receive operations, the circuitry comprising a transmit path including a power amplifier having a plurality of intermediate stages and configured to pass a first radio frequency signal, a first filter disposed at one of the intermediate stages and before an output stage of the power amplifier and configured to filter the first radio frequency signal, and one or more switches connecting the transmit path to a first antenna, the circuit also includes a receive path configured to receive a second radio frequency signal from the second antenna, the circuit also includes a duplexer path configured to facilitate a duplexer mode for performing both transmit and receive operations with the first antenna, and a duplexer bypass, the one or more switches are configured to allow switching between a duplexer mode and a duplexer bypass mode using both the first and second antennas; and

a plurality of connectors configured to provide electrical connection between the circuit and the package substrate.

18. A method for manufacturing a device having an isolation circuit, the method comprising:

forming or providing a transmit path comprising a power amplifier having a plurality of intermediate stages;

forming or providing a filter at an intermediate stage and before the output stage of the power amplifier;

forming or providing one or more switches between the transmit path and the first antenna to allow transmission of the first radio frequency signal; and

forming or providing a receive path connected to the second antenna such that the transmit and receive paths are isolated,

the one or more switches allow switching between a duplexer mode in which both transmit and receive operations are performed with the first antenna and a duplexer bypass mode in which both the first and second antennas are used.