HK1119497B

HK1119497B - Multi-frequency antenna array, rf transceiver and rf transmitter

Info

Publication number: HK1119497B
Application number: HK08110862.6A
Authority: HK
Inventors: 阿玛德雷兹．罗弗戈兰
Original assignee: 美国博通公司
Priority date: 2006-09-28
Filing date: 2008-09-30
Publication date: 2012-12-28

Description

Multi-frequency antenna array, radio frequency transceiver and radio frequency transmitter

Technical Field

The present invention relates to wireless communication systems, and more particularly to antenna structures used by Radio Frequency (RF) transceivers within such wireless communication systems.

Background

Communication systems are used to support wireless and wired communications between wireless and/or wired communication devices. Such communication systems include national and/or international cellular telephone systems to the internet, point-to-point, internal wireless network to radio frequency identification (RDIF) systems. Each type of communication system is constructed and operates in accordance with one or more communication standards. For example, a wireless communication system may operate in accordance with one or more standards including, but not limited to, Radio Frequency Identification (RFID), IEEE 802.11, Bluetooth, Advanced Mobile Phone Service (AMPS), digital AMPS, Global System for Mobile communications (GSM), Code Division Multiple Access (CDMA), Local Multipoint Distribution System (LMDS), Multi-channel multipoint distribution System (MMDS), and/or variations thereof.

Depending on the type of wireless communication system, wireless communication devices, such as cellular phones, walkie talkies, Personal Digital Assistants (PDAs), Personal Computers (PCs), laptops, home entertainment equipment, RDIF readers, RDIF tags, etc., communicate directly or indirectly with other wireless communication devices. For direct communication (also referred to as point-to-point communication), the participating wireless communication devices tune their receivers and transmitters to the same channel or channels (e.g., one of a plurality of Radio Frequency (RF) carriers of the wireless communication system) and communicate over the channel. For indirect wireless communication systems, each wireless communication device communicates directly with an associated base station (e.g., for a cellular telephone) and/or an associated access point (e.g., for an indoor or in-building wireless network) over a designated channel. To complete a communication connection between wireless communication devices, the associated base stations and/or associated access points communicate directly with each other through a system controller, a public switched telephone network, the internet, and/or some other wide area network.

For each wireless communication device participating in wireless communication, it includes a built-in radio transceiver (i.e., receiver and transmitter) or is connected to an associated radio transceiver (e.g., a station of an indoor and/or in-building wireless communication network, an RF modem, etc.). As is known, the receiver is connected to an antenna and comprises a low noise amplifier, one or more intermediate frequency stages, a filtering stage, and a data recovery stage. The low noise amplifier receives the inbound RF signal through the antenna and then amplifies it. The one or more intermediate frequency stages mix the amplified RF signals with one or more local oscillations, thereby converting the amplified RF signals to baseband signals or Intermediate Frequency (IF) signals. The filtering stage filters the baseband signals or the intermediate frequency signals to attenuate undesired out-of-band signals to generate filtered signals. The data recovery stage recovers the original data from the filtered signal in accordance with a particular wireless communication standard.

As is well known, a transmitter includes a data modulation stage, one or more intermediate frequency stages, and a power amplifier. The data modulation stage converts the raw data to a baseband signal according to a particular wireless communication standard. The one or more intermediate frequency stages mix the baseband signal with one or more local oscillations, thereby generating an RF signal. The power amplifier amplifies the RF signal before transmission through the antenna.

As the wireless part of the wireless communication starts and ends at the antenna, a properly designed antenna structure is an important part of the wireless communication device. As is known, the antenna structure is designed to have a desired impedance at the operating frequency (e.g., 50Ohm), a desired bandwidth centered at the desired operating frequency, and a desired wavelength (e.g., 1/4 wavelengths for the operating frequency for a monopole antenna). As is also known, the antenna structure may include one or more monopoles and/or dipoles having diversity antenna structures, the same polarization, different polarizations, and/or any number of other electromagnetic characteristics.

When the antenna structure comprises more than one antenna, the radiation characteristics of the antennas overlap at least to some extent. In the region of overlap, null may occur, where the RF signal transmitted by one antenna is 180 ° out of phase with the same RF signal transmitted by the other antenna, thus completely reducing the signal strength of the RF signal. If the intended receiver is located at the null point, its ability to accurately recover data from the RF signal is diminished.

Therefore, there is a need for an antenna structure that reduces the occurrence of nulls.

Disclosure of Invention

The apparatus and method of operation of the present invention are further described in the following brief description of the drawings, detailed description of the invention, and in the claims.

According to one aspect of the invention, a multi-frequency antenna array comprises:

a first antenna circuit having a first radiation characteristic and tuned to a first carrier frequency, wherein the first antenna circuit transmits a first representation of a Radio Frequency (RF) signal at the first carrier frequency, wherein the first carrier frequency corresponds to a carrier frequency of the RF signal and a first frequency offset; and

a second antenna circuit having a second radiation characteristic and tuned to a second carrier frequency, wherein the second antenna circuit transmits a second representation of a Radio Frequency (RF) signal at the second carrier frequency, wherein the second carrier frequency corresponds to a carrier frequency of the RF signal and a second frequency offset.

Preferably, each of the first and second antenna circuits comprises:

an antenna having a resistive portion, an inductive portion, and a capacitive portion, wherein the values of the resistive portion, the inductive portion, and the capacitive portion provide a resonant frequency corresponding to the first or second carrier frequency and provide a quality factor of a predetermined level of spectral overlap between the first and second antenna circuits.

Preferably, each of the first and second antenna circuits comprises at least one of:

a resistor connected to the antenna to provide a resistance of the first or second antenna circuit together with a resistive portion of the antenna;

a capacitor connected to the antenna and providing a capacitance of the first or second antenna circuit together with a capacitive part of the antenna;

an inductor connected to the antenna, providing, together with an inductive part of the antenna, an inductance of the first or second antenna circuit; wherein at least one of the resistance, capacitance, and inductance, together with the resistive, inductive, and capacitive portions, provides a resonant frequency corresponding to the first or second carrier frequency and provides a quality factor at a predetermined level of spectral overlap between the first and second antenna circuits.

an adjustable resistor connected to the antenna and providing, together with the resistive part of the antenna, the resistance of the first or second antenna circuit;

an adjustable capacitance connected to the antenna, providing, together with a capacitive part of the antenna, the capacitance of the first or second antenna circuit;

an adjustable inductance connected to the antenna, which together with the inductive part of the antenna provides the inductance of the first or second antenna circuit; wherein at least one of the adjustable resistance, the adjustable capacitance, and the adjustable inductance, together with the resistive portion, the inductive portion, and the capacitive portion, provides a resonant frequency corresponding to the first or second carrier frequency and provides a quality factor at a predetermined level of spectral overlap between the first and second antenna circuits.

Preferably, each of the first and second antenna circuits comprises:

an impedance matching circuit connected to the antenna, wherein the impedance matching circuit is tuned to provide a desired impedance at the first and second carrier frequencies.

Preferably, the multi-frequency antenna array comprises:

the antenna of the first antenna circuit is spaced from the antenna of the second antenna circuit by a distance of about 1/2 wavelengths of the carrier frequency.

Preferably, each of the first and second antenna circuits comprises at least one of: a monopole antenna; a dipole antenna; a directive reflective antenna; and a helical antenna.

Preferably, the multi-frequency antenna array comprises:

a third antenna circuit having a third radiation characteristic and tuned to a third carrier frequency, wherein the third antenna circuit transmits a third representation of an RF signal at the third carrier frequency, wherein the third carrier frequency corresponds to the carrier frequency of the RF signal and a third frequency offset; and

a fourth antenna circuit having a fourth radiation characteristic and tuned to a fourth carrier frequency, wherein the fourth antenna circuit transmits a fourth representation of the RF signal at the fourth carrier frequency, wherein the fourth carrier frequency corresponds to the carrier frequency of the RF signal and a fourth frequency offset.

Preferably, the multi-frequency antenna array comprises:

a third antenna circuit having a third radiation characteristic and tuned to a first carrier frequency, wherein said third antenna circuit transmits a third representation of an RF signal at said first carrier frequency, an

A fourth antenna circuit having a fourth radiation characteristic and tuned to a second carrier frequency, wherein the fourth antenna circuit transmits a fourth representation of the RF signal at the second carrier frequency.

According to an aspect of the present invention, a Radio Frequency (RF) transceiver includes:

a power amplifier module to:

generating a first representation of an outbound RF signal at a first transmit carrier frequency, wherein the first transmit carrier frequency corresponds to a carrier frequency of the outbound RF signal and a first transmit frequency offset; and

generating a second representation of the outbound RF signal at a second transmit carrier frequency, wherein the second transmit carrier frequency corresponds to the carrier frequency of the outbound RF signal and a second transmit frequency offset; a low noise amplifier module to:

receiving a first representation of an inbound RF signal at a first receive carrier frequency, wherein the first receive carrier frequency corresponds to a carrier frequency of the inbound RF signal and a first receive frequency offset;

receiving a second representation of an inbound RF signal at a second receive carrier frequency, wherein the second receive carrier frequency corresponds to a carrier frequency of the inbound RF signal and a second receive frequency offset; and is

Generating an inbound RF signal based on the first and second representations of the inbound RF signal; and a down conversion module for converting the inbound RF signal to an inbound signal.

Preferably, the RF transceiver further comprises:

an antenna for connecting a power amplifier module to a multi-frequency antenna array, wherein the multi-frequency antenna array comprises:

a first antenna circuit having a first radiation characteristic and tuned to a first transmit carrier frequency, wherein the first antenna circuit transmits a first representation of an outbound RF signal; and

a second antenna circuit having a second radiation characteristic and tuned to a second transmit carrier frequency, wherein the second antenna circuit transmits a second representation of the outbound RF signal.

Preferably, the RF transceiver further comprises:

an antenna for connecting a low noise amplifier module to a multi-frequency antenna array, wherein the multi-frequency antenna array comprises:

a first antenna circuit having a first radiation characteristic and tuned to a first receive carrier frequency, wherein the first antenna circuit receives a first representation of an inbound RF signal; and

a second antenna circuit having a second radiation characteristic and tuned to a second receive carrier frequency, wherein the second antenna circuit receives a second representation of an inbound RF signal.

Preferably, the first transmit carrier frequency is substantially equal to the first receive carrier frequency and the second transmit carrier frequency is substantially equal to the second receive carrier frequency.

Preferably, the RF transceiver further comprises:

a multi-frequency antenna array comprising:

Preferably, the multi-frequency antenna array comprises:

Preferably, the power amplifier module includes:

a power amplifier circuit for amplifying the outbound RF signal to generate an amplified outbound RF signal;

a first mixer to mix the amplified outbound RF signal with a first transmit frequency offset to generate a first representation of the outbound RF signal; and

a second mixer mixes the amplified outbound RF signal with a second transmit frequency offset to generate a second representation of the outbound RF signal.

Preferably, the power amplifier module includes:

a first impedance matching circuit connected to an output of the first mixer, wherein the first impedance matching circuit is tuned to provide a desired impedance at a first transmit carrier frequency; and

a second impedance matching circuit connected to an output of the second mixer, wherein the second impedance matching circuit is tuned to provide a desired impedance at the second transmit carrier frequency.

Preferably, the power amplifier module includes:

a first mixer to mix the outbound RF signal with a first transmit frequency offset to generate a first mixed representation of the outbound RF signal;

a second mixer that mixes the outbound RF signal with a second transmit frequency offset to generate a second mixed representation of the outbound RF signal;

a first power amplification circuit for amplifying the first mixed representation of the outbound RF signal to generate a first representation of the outbound RF signal; and

a second power amplification circuit to amplify the second mixed representation of the outbound RF signal to generate a second representation of the outbound RF signal.

Preferably, the power amplifier module includes:

a mixer for mixing the outbound RF signal with the first transmit frequency offset to generate a first mixed representation of the outbound RF signal and a second mixed representation of the outbound RF signal, wherein the first mixed representation corresponds to the upper sideband and the second mixed representation corresponds to the lower sideband;

According to an aspect of the present invention, a Radio Frequency (RF) transmitter includes:

an up-conversion module for converting the outbound signal into an outbound RF signal; and

a power amplifier module to:

generating a second representation of the outbound RF signal at a second transmit carrier frequency, wherein the second transmit carrier frequency corresponds to the carrier frequency of the outbound RF signal and a second transmit frequency offset. Preferably, the RF transmitter further comprises:

Preferably, the RF transmitter further comprises:

a multi-frequency antenna array comprising:

Preferably, the power amplifier module includes:

Other features and advantages of the present invention will become apparent from the following detailed description of the invention which refers to the accompanying drawings.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

fig. 1 is a schematic block diagram of a wireless communication system according to the present invention;

fig. 2 is a schematic block diagram of a wireless communication system according to the present invention;

figure 3 is a schematic diagram of an embodiment of a multi-frequency antenna array according to the present invention;

FIG. 4 is a frequency domain plot of the response of the multi-frequency antenna array of FIG. 3;

figure 5 is a schematic block diagram of another embodiment of a multi-frequency antenna array in accordance with the present invention;

fig. 6 is a schematic block diagram of an equivalent circuit of an antenna embodiment of a multi-frequency antenna array in accordance with the present invention;

figure 7 is a schematic diagram of another embodiment of a multi-frequency antenna array in accordance with the present invention;

FIG. 8 is a frequency domain plot of the response of one embodiment of the multi-frequency antenna array of FIG. 7;

FIG. 9 is a frequency domain graph of a response of another embodiment of the multi-frequency antenna array of FIG. 7;

fig. 10 is a schematic block diagram of an embodiment of a power amplifier module according to the present invention;

fig. 11 is a schematic block diagram of another embodiment of a power amplifier module in accordance with the present invention;

fig. 12 is a schematic block diagram of another embodiment of a power amplifier module in accordance with the present invention;

fig. 13 is a schematic block diagram of another embodiment of a power amplifier module in accordance with the present invention;

fig. 14 is a schematic block diagram of another embodiment of a power amplifier module in accordance with the present invention;

fig. 15 is a schematic block diagram of another embodiment of a power amplifier module according to the present invention.

Detailed Description

Fig. 1 is a schematic block diagram of a communication system 10 in accordance with the present invention, the communication system 10 including a plurality of base stations and/or access points 12-16, a plurality of wireless communication devices 18-32, and a network hardware component 34. The wireless communication devices 18-32 may be laptop host computers 18 and 26, personal digital assistant hosts 20 and 30, personal computer hosts 24 and 32, and/or cellular telephone hosts 22 and 28. The details of the wireless communication device will be described in more detail with reference to fig. 2.

The base station or access point 12 is connected to the network hardware 34 by local area network connections 36, 38 and 40. Network hardware 34, which may be a router, switch, bridge, modem, system controller, etc., provides wide area network connection 42 for communication system 10. Each base station or access point 12-16 has an associated antenna or antenna array for communicating with wireless communication devices within its area. Generally, wireless communication devices register with a particular base station or access point 12-14 to receive service from the communication system 10. For direct connection (i.e., point-to-point communication), the wireless communication devices communicate directly over the assigned channel.

Typically base stations are used for cellular telephone systems and similar systems, while access points are used for indoor or in-building wireless networks. Regardless of the particular type of communication system, each wireless communication device includes a built-in radio and/or is connected to a radio. The radio includes a high linearity amplifier and/or a programmable multi-stage amplifier, as disclosed herein, for enhanced performance, reduced cost, reduced size, and/or enhanced broadband applications.

Fig. 2 is a schematic block diagram of a wireless communication device including hosts 18-32 and an associated radio 60. For a cellular telephone host, the radio 60 is a built-in component. For a personal digital assistant host, a laptop host, and/or a personal computer host, the radio 60 is a built-in or externally connected component. Those skilled in the art will appreciate that the radio 60 may be a stand-alone device (i.e., independent of the host) and/or used in a number of other applications to transceive RF signals.

As shown, host devices 18-32 include a processing module 50, a memory 52, a radio interface 54, an input interface 58, and an output interface 56. The processing modules 50 and 52 execute corresponding instructions typically performed by a host. For example, for a cellular telephone host, the processing module 50 performs the corresponding communication functions according to a particular cellular telephone standard.

The radio interface 54 allows data to be received from and transmitted to the radio 60. For data received from radio 60 (e.g., inbound data), radio interface 54 provides the data to processing module 50 for further processing and/or routing to output interface 56. The output interface 56 may be connected to an output display device, such as a display, monitor, speaker, etc., to display received data. The radio interface 54 also provides data from the processing module 50 to the radio 60. The processing module 50 may receive inbound data from an input device (e.g., keyboard, keypad, microphone, etc.) or generate data itself via the input interface 58. For data received through input interface 58, processing module 50 may perform a corresponding host function on the data and/or route it to radio 60 through radio interface 54.

The radio 60 includes a host interface 62, a digital receiver processing module 64, a digital-to-analog conversion module 66, a filtering/gain module 68, a down-conversion module 70, a low noise amplifier module 72, a local oscillation module 74, a memory 73, a digital transmission processing module 76, a digital-to-analog converter 78, a filtering/gain module 80, an up-conversion module 82, a power amplifier module 84, and a multi-frequency antenna array 75, which will be described in more detail with reference to one or more of fig. 3-9. It is noted that down conversion module 70, low noise amplifier module 72, local oscillation module 74, up conversion module 82, and power amplifier module 84 may all be collectively referred to as an RF transceiver 90.

The digital receiver processing module 64 and the digital transmit processing module 76, in conjunction with operating instructions stored in the memory 73 and/or internally, perform digital receiver functions and digital transmitter functions, respectively. Digital receiver functions include, but are not limited to, digital intermediate frequency to baseband conversion, demodulation, constellation demapping, decoding, and/or descrambling. Digital transmitter functions include, but are not limited to, scrambling, encoding, constellation mapping, modulation, and/or digital baseband to IF conversion. The digital receiver and transmitter processing modules 64 and 76 may be implemented using a shared processing device, a single processing device, or multiple processing devices. Such a processing device may be a microprocessor, microcontroller, digital signal processor, microcomputer, central processing unit, field programmable gate array, programmable logic device, state machine, logic circuitry, analog circuitry, digital circuitry, and/or any device that processes (analog and/or digital) signals in accordance with operational instructions. The memory 73 may be a single memory device or a plurality of memory devices. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, and/or any device that stores digital information. It is noted that when the processing module 64 and/or 76 implements one or more of its functions via a state machine, analog circuitry, digital circuitry, and/or logic circuitry, the memory storing the corresponding operational instructions is embedded within the circuitry comprising the state machine, analog circuitry, digital circuitry, and/or logic circuitry.

In operation, the radio 60 receives outbound data 94 from the host device through the host interface 62. Host interface 62 routes outbound data 94 to digital transmission processing module 76, and transmission processing module 76 processes outbound data 94 in accordance with a particular wireless communication standard (e.g., IEEE 802.11a, IEEE 802.11b, Bluetooth, etc.) to generate data 96 in a digital transmission format. The data 96 in the digital transmission format may be a digital baseband signal or a digital low intermediate frequency signal, wherein the digital low intermediate frequency is in the frequency range of zero to several megahertz.

The digital-to-analog conversion module 78 includes one or more digital-to-analog converters that convert the data 96 in a digital transmission format from the digital domain to the analog domain. The filtering/gain module 80 filters and/or adjusts the gain of the analog signal before providing the analog signal to the up-conversion module 82. The up-conversion module 82 converts the analog baseband or low intermediate frequency signal directly to an RF signal based on a transmitter local oscillation 83 provided by the local oscillation module 74. The power amplifier module 84, which will be described in greater detail with reference to fig. 10-13, amplifies the RF signal to generate an outbound RF signal 98. The multi-frequency antenna array 75 transmits the outbound RF signal 98 to a destination device, such as a base station, an access point, and/or another wireless communication device.

The radio 60 also receives an inbound RF signal 88 through the multi-frequency antenna array 75, where the inbound RF signal 88 is transmitted by a base station, access point, or another wireless communication device. The multi-frequency antenna array 75 provides the inbound RF signal 88 to the low noise amplifier module 72, and the low noise amplifier module 72 may include one or more low noise amplifiers to amplify the inbound RF signal 88 to generate an amplified inbound RF signal. The low noise amplifier module 72 provides the amplified inbound RF signal to the down conversion module 70, and the down conversion module 70 directly converts the amplified inbound RF signal to an inbound low intermediate frequency signal based on a receiver local oscillation 81 provided by the local oscillation module 74. The down conversion module 70 provides the inbound low intermediate frequency signal to the filter/gain module 68, and the filter/gain module 68 filters and/or adjusts the gain of the signal before providing the signal to the analog-to-digital converter module 66.

The analog-to-digital conversion module 66 includes one or more digital-to-analog converters that convert the filtered inbound low intermediate frequency signals from the analog domain to the digital domain to generate data 90 in a digital receive format. The digital receiver processing module 64 decodes, descrambles, demaps, and/or demodulates the data 90 in the digital reception format to reacquire the inbound data 92 in accordance with the particular wireless communication standard implemented by the radio. The host interface 62 provides the retrieved inbound data 92 to the host devices 18-32 over the radio interface 54.

Those skilled in the art will appreciate that the radio 60 may be implemented by one or more integrated circuits. For example, the entire radio 60 may be integrated on one IC, including the multi-frequency antenna array 75. In another example, the radio 60 may be implemented on one IC without the multi-frequency antenna array 75, with the multi-frequency antenna array 75 implemented on another IC or printed circuit board, and/or as a free structure. As another example, the RF transceiver is implemented on one IC and the remainder of the radio 60 (except for the multi-frequency antenna array 75) may be implemented on another IC. As another example, the digital receiver and transmitter processing modules 64 and 76 may be located on one IC, while the remaining modules of the radio 60, except for the multi-frequency antenna array 75, are located on another IC.

Fig. 3 is a schematic diagram of an embodiment of a multi-frequency antenna array 75, the multi-frequency antenna array 75 comprising a first antenna circuit 100 and a second antenna circuit 102. The first antenna circuit 100 has a first radiation characteristic (pattern)100 that depends on the type of antenna and the polarized antenna. In this example, the antenna may be a monopole antenna, a dipole antenna, a directive reflector antenna, or a helical antenna, as disclosed in co-pending patent applications having serial No. 11/386,247, application date 21/3/2006, entitled "PLANER HELICAL ANTENNA," and serial No. 11/451,752, application date 12/6/2006, entitled "planet antenna.

The first antenna 100 is tuned to a first carrier frequency that depends on the carrier frequency of the RF signal (e.g., the inbound RF signal 88 and/or the outbound RF signal 98) and the first frequency offset 112. The value of the first frequency offset 112 changes the frequency of the RF signal by a relatively small amount so that it remains within the bandwidth of the RF transceiver 90. For example, referring to FIG. 4, the RF signals 88 or 98 are located within a 900MHz frequency band, the inbound RF signal 96 has a carrier frequency of 880MHz, and/or the outbound RF signal 98 has a carrier frequency of 920 MHz. The frequency offset may be up to a few percent of the carrier frequency (e.g., up to 27MHz) such that the carrier frequency of the RF signal 88 or 98 is at the first carrier frequency (i.e., the carrier frequency of the RF signal 88 or 98 plus or minus the first frequency offset (Δ fl) 112).

The second antenna circuit 102 is spaced from the first antenna circuit 1001/2 by a wavelength (λ) and has a second radiation characteristic 110, the second radiation characteristic 110 depending on the type of antenna and the polarized antenna. In this example, the antenna may be a monopole, dipole, directive reflector, or helical antenna, as disclosed in co-pending patent applications having serial No. 11/386,247, application date 21/3/2006, entitled "PLANER HELICALANTENNA," and serial No. 11/451,752, application date 12/6/2006, entitled "PLANER ANTENNA STRUCTURE.

The second antenna circuit 102 is tuned to a first carrier frequency that depends on the carrier frequency of the RF signal (e.g., the inbound RF signal 88 and/or the outbound RF signal 98) and the second frequency offset 114. The value of the second frequency offset 114 changes the frequency of the RF signal by a relatively small amount so that it remains within the bandwidth of the RF transceiver 90. For example, referring to FIG. 4, the RF signals 88 or 98 are located within a 900MHz frequency band, the inbound RF signal 96 has a carrier frequency of 880MHz, and/or the outbound RF signal 98 has a carrier frequency of 920 MHz. The second frequency offset 114 may be up to a few percent of the carrier frequency (e.g., up to 27MHz), but is different from the first frequency offset such that the carrier frequency of the RF signal 88 or 98 is at the second carrier frequency (i.e., the carrier frequency of the RF signal 88 or 98 plus or minus the second frequency offset (Δ f2) 114).

Referring to fig. 3 and 4, the response 118 of the first antenna circuit 100 and the response 120 of the second antenna circuit 102 depend on the characteristics of the antenna circuits 100 and 102. Furthermore, an acceptable level of spectral overlap factor 116 is involved in the design of the antenna circuit. For example, the quality factor of the antenna circuit affects the selectivity (i.e., bandwidth and replication (roll off)) of the antenna responses 118 and 120. The quality factor (Q) of the antenna circuits 100 and 102 is determined by its inductive, resistive and capacitive characteristics. For example, in a series resonant circuit₀L＝1/ω₀C, therefore Q ═ ω₀L/R or Q1/omega₀CR; for parallel resonant circuits, ω₀＝√(1/LC)*√(1-1/Q²) And the half-power point corresponds to dv-v 0Q/2, where v0 is the resonant frequency and dv is the half-power frequency offset from v 0. In this way, the antenna circuits 100 and 102 may be tuned to a desired frequency and selectivity to achieve a frequency spectrum as shown in fig. 4.

Fig. 5 is a schematic diagram of another embodiment of a multi-frequency antenna array 75, the multi-frequency antenna array 75 comprising a first antenna circuit 100 and a second antenna circuit 102. In this embodiment, each of the first and second antenna circuits 100 and 102 includes an antenna 132 and 130 and an impedance matching circuit 136 and 134, respectively. The antennas 130 and 132 may be monopole antennas, dipole antennas, directive reflector antennas, or helical antennas, as disclosed in co-pending patent applications having serial No. 11/386,247, application date 21/3/2006, entitled "PLANERHELICAL ANTENNA," and serial No. 11/451,752, application date 12/6/2006, entitled "PLANER ANTENNA structrue.

Impedance matching circuits 134 and 136 are used to match the impedance of the corresponding antennas 130 and 132 to the power amplifier module 84 and/or the low noise amplifier module 72, each of the impedance matching circuits 134 and 136 including a balun, a capacitor, and/or an inductor in series and/or parallel with the antennas 130 and 132 to achieve a desired inductive matching at a desired operating frequency.

Fig. 6 is a schematic block diagram of an equivalent circuit of an antenna 130 or 132 embodiment of a multi-frequency antenna array 75 according to the present invention, the multi-frequency antenna array 75 being connected to a signal source (e.g., the first and second representations 104 or 106 of the RF signals 88 or 98). In this example, the antenna is a dipole antenna (e.g., 1/2 having an overall length corresponding to the wavelength of the frequency of the signal it receives) and includes a resistive portion (R), an inductive portion (L), and a capacitive portion (C). As mentioned previously, the response of an antenna is based on its quality factor (Q), which is based on inductive, resistive and capacitive characteristics. In this way, by controlling R, L, and/or C of the antenna, a desired response may be obtained. In one embodiment, the antenna 130 or 132 natural R, L, and/or C, may be controlled, which achieves a desired response. In another embodiment, outer portions R, L, and/or C are connected in series and/or parallel with antenna 130 or 132 to provide a desired response. In another embodiment, the outer portion R, L, and/or C, may be adjusted to precisely tune the antenna response 118 or 120.

Thus, by transmitting an RF signal through multiple antennas, each antenna having a different response and transmitting a different representation of the RF signal (e.g., transmitting the RF signal using a carrier frequency that corresponds to the carrier frequency of the RF signal plus or minus a frequency offset), the nulls created by transmitting the signal through the multiple antennas using the same carrier frequency are reduced. Furthermore, by selecting a relatively small frequency offset, the channel bandwidth of the transceiver need not be changed.

Figure 7 is a schematic diagram of another embodiment of a multi-frequency antenna array 75 in accordance with the present invention; the multi-frequency antenna array 75 includes a first antenna circuit 100, a second antenna circuit 102, a third antenna circuit 146, and a fourth antenna circuit 144. Each of the antenna circuits 100, 102, 144, and 146 has a corresponding radiation characteristic 108, 110, 148, and 150 that results from beamforming and/or different antenna polarization. The distance between antenna circuits 100, 102, 144, and 146 is approximately 1/2 wavelengths, or other portions of the wavelength of the transmitted RF signal. It is noted that the third and fourth antenna circuits 146 and 144 have similar structures as the first and second antenna circuits 100 and 102, but have different radiation characteristics 148 and 150.

In an embodiment, the third antenna circuit 146 transmits the third representation 140 of the RF signal (e.g., the inbound RF signal 88 or the outbound RF signal 98) at a third carrier frequency that corresponds to the carrier frequency of the RF signal and a third frequency offset. The fourth antenna circuit 144 transmits a fourth representation 142 of the RF signal at a fourth carrier frequency corresponding to the carrier frequency of the RF signal and a fourth frequency offset. A frequency domain plot of this embodiment is shown in fig. 9, where each of the four representations 104, 106, 140 and 142 is offset in frequency by a different frequency offset 112, 114, 160 and 162 of the carrier frequency of the RF signal 88 or 98.

Returning again to the discussion of fig. 7 and the alternative embodiment, the third antenna circuit 146 is tuned to the first carrier frequency. Thus, the third antenna circuit 146 transmits the third representation 140 of the RF signal at the first carrier frequency. The fourth antenna circuit 144 is tuned to the second carrier frequency. Thus, the fourth antenna circuit 144 transmits the fourth representation 142 of the RF signal at the second carrier frequency. In this example, the resulting nulls are minimal since the radiation characteristic of the third antenna circuit is generally opposite to the radiation characteristic of the first antenna circuit and minimal airborne signals will be combined, and the second and fourth antenna structures are similarly applied. A frequency domain diagram of this antenna array 75 is shown in fig. 8.

Fig. 10 is a schematic block diagram of an embodiment of a power amplifier module 84, the power amplifier module 84 including a power amplifier circuit 170 (which may be a power amplifier or a pre-amplifier), mixers 174 and 176, and frequency offset signal sources 172 and 178. The power amplifier 170 amplifies the outbound RF signal 98 to generate an amplified RF signal. The first signal source 172 generates a first frequency offset (Δ f1)112 and the second signal source generates a second frequency offset (Δ f2) 114. It is noted that the first and second frequency offsets 112 and 114 may be sinusoidal signals having a desired frequency.

The first mixer 174 mixes the amplified RF signal with the first frequency offset 112 to generate the first representation 104 of the RF signal 98. The second mixer 176 mixes the amplified RF signal with the second frequency offset 114 to generate the second representation 106 of the RF signal 98. It is noted that the antenna circuits 100 and 102 have the desired quality factor and half power factor and the other sideband generated by the multiplication of the two sinusoidal signals is outside the frequency band of the antenna and therefore can be ignored. Optionally, the antenna circuit and/or the power amplifier module may include filtering to further attenuate the other sideband. It is also noted that the antenna circuits 100 and 102 may be tuned to the sidebands generated by the mixers 174 or 176, one antenna circuit may be tuned to the upper sideband and the other antenna circuit may be tuned to the lower sideband. It is further noted that the first and second frequency offsets may have the same frequency, wherein one representation of the RF signal corresponds to the lower sideband and the other representation of the RF signal corresponds to the upper sideband. In the latter alternative, the power amplifier module 84 may include only one mixer and one signal source to generate the first and second representations 104 and 106 of the RF signal 98.

Fig. 11 is a schematic block diagram of another embodiment of a power amplifier module 84, the power amplifier module 84 including a power amplifier circuit 170, mixers 174 and 176, frequency offset signal sources 172 and 178, and impedance matching circuits 180 and 182. The power amplifier circuit 170 amplifies the outbound RF signal 98 to generate an amplified RF signal. The first signal source 172 generates a first frequency offset (Δ fl)112 and the second signal source generates a second frequency offset (Δ f2) 114. It is noted that the first and second frequency offsets 112 and 114 may be sinusoidal signals having a desired frequency and/or the same frequency.

The first mixer 174 mixes the amplified RF signal with the first frequency offset 112 to generate the first representation 104 of the RF signal 98. The second mixer 176 mixes the amplified RF signal with the second frequency offset 114 to generate the second representation 106 of the RF signal 98. The first impedance matching circuit 180 includes a balun, a capacitor, and/or an inductor that provides the first representation 104 of the RF signal 98 to the antenna array 75. The second impedance matching circuit 182, which includes a balun, a capacitor, and/or an inductor, provides the second representation 106 of the RF signal 98 to the antenna array 75.

Fig. 12 is a schematic block diagram of another embodiment of a power amplifier module 84, the power amplifier module 84 including first and second power amplification circuits 190 and 192 (each of which may be a power amplifier or a pre-amplifier), mixers 174 and 176, and frequency offset signal sources 172 and 178. The power amplification circuits 190 and 192 amplify the outbound RF signal 98 to generate two amplified RF signals. The first signal source 172 generates a first frequency offset (Δ f1)112 and the second signal source generates a second frequency offset (Δ f2) 114. It is noted that the first and second frequency offsets 112 and 114 may be sinusoidal signals having a desired frequency.

The first mixer 174 mixes a first of the two amplified RF signals with the first frequency offset 112 to generate the first representation 104 of the RF signal 98. The second mixer 176 mixes a second of the two amplified RF signals with the second frequency offset 114 to generate a second representation 106 of the RF signal 98.

Fig. 13 is a schematic block diagram of another embodiment of a power amplifier module including first and second power amplification circuits 190 and 192 (each of which may be a power amplifier or a pre-amplifier), mixers 174 and 176, and frequency offset signal sources 172 and 178. The power amplification circuits 190 and 192 amplify the outbound RF signal 98 to generate two amplified RF signals. The first signal source 172 generates a first frequency offset (Δ f1)112 and the second signal source generates a second frequency offset (Δ f2) 114. It is noted that the first and second frequency offsets 112 and 114 may be sinusoidal signals having a desired frequency.

Fig. 14 is a schematic block diagram of another embodiment of a power amplifier module including first and second power amplification circuits 190 and 192 (each of which may be a power amplifier or a pre-amplifier), mixers 174 and 176, and frequency offset signal sources 172 and 178. The first mixer 174 mixes the outbound RF signal 98 with the first frequency offset 112 to generate a first mixed representation of the RF signal 98. The second mixer 176 mixes the outbound RF signal with the second frequency offset 114 to generate a second mixed representation of the RF signal 98. The power amplifier circuit 190 amplifies the first mixed representation of the RF signal 98 to generate a first representation 104 of the RF signal 98, and the power amplifier circuit 192 amplifies the second mixed representation of the RF signal 98 to generate a second representation 106 of the outbound RF signal 98.

Fig. 15 is a schematic block diagram of another embodiment of a power amplifier module 84, the power amplifier module 84 including first and second power amplification circuits 190 and 192 (each of which may be a power amplifier or a pre-amplifier), a mixer 174, and a frequency offset signal source 172. The mixer 174 mixes the outbound RF signal 98 with the first frequency offset 112 to generate a first mixed representation and a second mixed representation of the RF signal 98. In this embodiment, the first mix represents the corresponding upper sideband 105 and the second mix represents the corresponding lower sideband 107. The power amplifier circuit 190 amplifies the first mixed representation of the RF signal 98 to generate a first representation 104 of the RF signal 98, and the power amplifier circuit 192 amplifies the second mixed representation of the RF signal 98 to generate a second representation 106 of the outbound RF signal 98.

As used herein, the term "substantially" or "approximately" provides an industry-accepted tolerance to the corresponding term and/or relationship between the terms. Such an industry-accepted tolerance ranges from less than 1% to 50% and corresponds to, but is not limited to, component values, integrated circuit process fluctuations, temperature fluctuations, rise and fall times, and/or thermal noise. These relationships between terms range from a few percent difference to a very large difference. As may be used herein, the term "operably coupled" includes both direct and indirect connections (terms including, but not limited to, components, elements, circuits, and/or modules) between which the intervening term(s) does not alter the information of a signal but may adjust its current level, voltage level, and/or power level. As further used herein, inferred coupling (i.e., where one element is coupled to another element by inference) includes direct and indirect coupling between two elements in the same manner as "coupled". As further used herein, the term "available to" is meant to include one or more power connections, inputs, outputs, etc. to perform one or more corresponding functions, as well as to include inferred connections to one or more other terms. As further used herein, the term "and". . . Related includes terms that are directly or indirectly connected or separated and/or that one term is embedded in another. As further used herein, the term "compares favorably", indicates that a comparison between two or more elements, items, signals, etc., provides a desired relationship. For example, when the desired relationship is that signal 1 has a greater amplitude than signal 2, favorable comparison results may be obtained when the amplitude of signal 1 is greater than the amplitude of signal 2 or the amplitude of signal 2 is less than the amplitude of signal 1.

The invention has been described above with the aid of method steps illustrating the execution of specific functions and relationships thereof. The boundaries of these functional building blocks and method steps have been defined herein specifically for the convenience of the description. Selective boundaries and sequences may also be appropriately implemented so long as the specific functions and relationships are appropriately performed. Any such selective boundaries and sequences are within the scope and spirit of the present invention.

The invention has also been described above with the aid of functional blocks illustrating some important functions. For convenience of description, the boundaries of these functional building blocks have been defined specifically herein. Selective boundaries can also be defined so long as the essential functions are appropriately performed. Similarly, flow diagram blocks may be specifically defined herein to illustrate certain important functions, and the boundaries and sequence of the flow diagram blocks may be otherwise defined for general application so long as the important functions are still achieved. Variations in the boundaries and sequence of the above described functional blocks, flowchart functional blocks, and steps may be considered within the scope of the following claims. Those skilled in the art will also appreciate that the functional blocks described herein, and other illustrative blocks, modules, and components, may be implemented as discrete components, special purpose integrated circuits, processors with appropriate software, and the like.

Claims

1. A multi-frequency antenna array, comprising:

a first antenna circuit having a first radiation characteristic and tuned to a first carrier frequency, wherein the first antenna circuit transmits a first representation of a radio frequency signal at the first carrier frequency, wherein the first carrier frequency corresponds to a carrier frequency of the radio frequency signal and a first frequency offset; and

a second antenna circuit having a second radiation characteristic and tuned to a second carrier frequency, wherein the second antenna circuit transmits a second representation of the radio frequency signal at the second carrier frequency, wherein the second carrier frequency corresponds to the carrier frequency of the radio frequency signal and a second frequency offset; or the multi-frequency antenna array further comprises:

a third antenna circuit having a third radiation characteristic in an opposite direction to the first radiation characteristic and tuned to the first carrier frequency, wherein the third antenna circuit transmits a third representation of radio frequency signals at the first carrier frequency; and

a fourth antenna circuit having a fourth radiation characteristic in an opposite direction to the second radiation characteristic and tuned to the second carrier frequency, wherein the fourth antenna circuit transmits a fourth representation of a radio frequency signal at the second carrier frequency.

2. The multi-frequency antenna array of claim 1, wherein the first and second antenna circuits, or each of the first, second, third and fourth antenna circuits, comprise:

3. The multi-frequency antenna array of claim 2, wherein the first and second antenna circuits, or each of the first, second, third and fourth antenna circuits, comprise at least one of:

4. The multi-frequency antenna array of claim 2, wherein the first and second antenna circuits, or each of the first, second, third and fourth antenna circuits, comprise at least one of: