CN1777073B - Device for realizing multi-carrier receiving signal strength indication - Google Patents

Abstract

The disclosed device includes first radio frequency filter, low noise amplifier, second frequency filter, down converter, intermediate frequency amplifier, variable gain controller, anti aliasing filter, A/D converter, and signal processor. Through gains of VGC and AGC, the disclosed device obtains value of RSSI so as to avoid complex calculation, save resource. Modifying parameters of part of devices, the invention is available to detect multicarrier RSSI indifferent system formats. Advantages are: better compatibility, lowered cost and capable of indicating signal of each carrier.

Description

Device for Realizing Multi-carrier Received Signal Strength Indication

technical field

The invention relates to a device for realizing multi-carrier received signal strength indicator RSSI (Received Signal Strength Indicator received signal strength indicator), more specifically, it is a relatively novel, simple and easy-to-implement device.

Background technique

With the rapid development of mobile communication technology today, people's demand for mobile communication systems is also increasing. Under limited resources, multi-carrier receivers are the development trend of mobile communication systems, and multi-carrier Received Signal Strength Indicator (RSSI) is important Its relative accuracy has a great relationship with the capacity of the system.

There are two main ways to implement RSSI at present: intermediate frequency and baseband. As shown in Figure 1, the specific process of RSSI in the intermediate frequency IF unit is: firstly, the received RF signal is filtered, amplified, and mixed, and then the mixed IF signal is coupled and amplified, and then sent to the modulus through the detector The converter is finally sent to DSP (Digital Signal Processing) for processing. The disadvantages of the method and device are that the circuit is complex, the degree of integration is not high, and the precision is not very ideal. In addition, the dynamic range of the detector is also limited.

As shown in Figure 2, the specific process of implementing RSSI in the IF baseband unit is: filter, amplify, and mix the received RF signal to obtain a low IF signal. The digital I/Q signal is squared. The disadvantage of this method and device is that the calculation is complicated and the consumption of hardware resources is relatively large, resulting in high hardware cost.

For a multi-carrier receiver, it is very complicated to use the method and device in Fig. 1 and Fig. 2 to perform RSSI detection. RSSI detection is the total energy of multi-carrier signals, and cannot indicate the energy of each carrier signal, because multiple Only one RF unit can distinguish each carrier signal, which is too expensive. Besides, too many analog circuit units will reduce the detection accuracy, so it is necessary to find new methods and devices to meet new requirements.

Contents of the invention

The technical problem solved by the present invention is to provide a device for realizing simple multi-carrier received signal strength indication, and realize the energy detection of each carrier signal.

In order to achieve the above-mentioned object, the present invention just adopts software radio technology to realize the detection of multi-carrier received signal strength indicating RSSI, because in receiving signal processing part RSP (Receive Signal Processing) realizes multi-carrier RSSI detection, can indicate the signal of each carrier like this Strength, so RSSI must be implemented after channel filtering and before AGC.

The structural block diagram of the device of the present invention is shown in Figure 3, comprising: a first radio frequency filter, a low noise amplifier, a second radio frequency filter, a down converter, an intermediate frequency amplifier, a variable gain controller, an anti-aliasing filter, an analog Digital converter and receiving signal processor; the radio frequency signal is filtered by the first radio frequency filter to filter out-of-band spurs, amplified by the low noise amplifier, and the second radio frequency filter is used to filter out the noise interference of the mixer mirror phase, and then reaches the down converter Perform down-conversion processing and convert it into an intermediate frequency signal. After passing through the intermediate frequency amplifier and variable gain controller, it is sent to the analog-to-digital converter through the anti-aliasing filter for analog-to-digital conversion into digital signals. Finally, the receiving signal processor These digital signals are digitally demodulated, extracted, and filtered to obtain an indication of the received signal strength of each carrier.

Using the device of the present invention, the value of RSSI can be obtained through the gain of VGC and AGC, thus avoiding many complex calculations, saving resources, and can indicate the signal of each carrier, so it has good compatibility, for multi-carrier RSSI of different systems For detection, it is only necessary to modify some device parameters of the device, which effectively reduces the cost. The above-mentioned device is simple to implement and has high detection accuracy, which can overcome the complexity of existing RSSI detection, realize signal energy detection per carrier, improve detection accuracy, reduce radio frequency links, improve stability, and be suitable for large-scale production, etc., to ensure multi-carrier The maximum number of access users of the frequency receiver is increased, the cost is reduced, the efficiency is improved, and the market demand of fierce competition is met.

Description of drawings

Figure 1 is a structural block diagram of RSSI detection at the IF using a detection method.

Fig. 2 is a structural block diagram of realizing RSSI detection at the baseband.

Fig. 3 is a structural block diagram of multi-carrier received signal strength indication using software radio according to the present invention.

Fig. 4 is a table of actual test results as an indication of the received signal strength of two carriers implemented in the present invention.

FIG. 5 is a diagram of the actual detection relationship of multi-carrier received signal strength indication as the embodiment of the present invention.

Fig. 6 is a relationship diagram of the absolute accuracy of the 2-carrier received signal strength indication as the device of the present invention.

Fig. 7 is a relational diagram of the relative accuracy of received signal strength indication of two carriers as the device of the present invention.

Detailed ways

In a multi-carrier receiver system, RSSI indicates the total energy of multiple carriers. If the energy of each carrier is to be indicated, multiple RF links are required. Factors such as the discrete nature of analog components and the small dynamic range of detector tubes will cause the accuracy of RSSI detection to decrease, which will bring a lot of inconvenience to design and debugging, and is not conducive to mass production.

In view of the current device level, the multi-carrier receiver can be implemented in the form of software radio, and the RSSI indicates the signal energy of each carrier, which is beneficial to system design and performance improvement. Fig. 3 is a structural block diagram of multi-carrier received signal strength indication using software radio according to the present invention.

In the following, the method and device for broadband multi-carrier frequency received signal strength indication are concretely constructed by using existing devices. The feasibility of the method and device of the present invention is illustrated by taking the realization of Node B 2 carrier received signal strength indication as an example. Among them, the first RF filter in Figure 3 is a duplexer, mainly to filter out-of-band spurs; the low-noise amplifier LNA uses SGA-4586; the second RF filter uses LE18A; the down-converter uses SME1400B-17; The intermediate frequency amplifier adopts SGA-6486; the variable gain controller adopts AA113-310; the anti-aliasing filter adopts IF SAW filter LE88F; the analog-to-digital converter ADC adopts AD80101; the receiving signal processor adopts ISL5416.

For the example of using a digital intermediate frequency structure to realize a 2-carrier receiver system, it is critical to determine the frequency and sampling frequency of the IF SAW filter. According to the Nyquist sampling criterion, the relationship between the IF frequency and the sampling frequency can be known as $f_{\mathrm{IF}}=\frac{(2\mathrm{no}+1)}{4}{f}_S.$ Through combined interference analysis and calculation, the intermediate frequency f _IF is selected as 172.8MHz, and the sampling rate f _S is 61.44MHz. Since the two carrier signals before the ADC coexist, in order not to saturate the ADC and affect the detection accuracy, it is necessary to select a reasonable spurious-free dynamic range SFDR.

In order to detect the RSSI value of each carrier, it is necessary to detect the RSSI after the digital NCO and channel filtering and before the AGC. According to the corresponding relationship between the AGC function and the input power, it is known that the RSSI detection value is the sum of the AGC gain, the gain of the digitally controlled attenuator VGC and the reference power, see equation (1).

P _RSSI =k×(G _AGC -G _REF )+P _REF +G _VGC (1)

Among them, G _AGC is the gain of AGC, G _VGC is the gain of the variable controller, P _REF , k, and G _REF are constants.

From equation (1) above, it can be seen that the absolute accuracy of RSSI detection is a function of the AGC gain and the variable controller VGC. According to the 3GPP standard, the range of RSSI detection is -103dBm～-73dBm. In the device of the present invention, the variable gain controller is a numerically controlled attenuator, and its purpose is mainly to attenuate when these large signals are blocked in adjacent channels, and to pass through in other situations, and the attenuation control value is 0dB. Therefore, within the scope of the 3GPP standard, the RSSI detection value is only an AGC gain function.

P _RSSI =k×(G _AGC -G _REF )+P _REF (2)

Fig. 4 is a table of actual test results of the present invention implementing 2-carrier received signal strength indication. Fig. 5 is a relationship diagram of the actual detection of multi-carrier received signal strength indication in implementation 2 of the present invention. The RSSI detection accuracy includes absolute accuracy and relative accuracy, the relative accuracy is ±4dB, and the absolute accuracy is ±0.5dB. In order to embody the advantages of the RSSI detection method and device of the present invention, it is necessary to analyze from absolute accuracy and relative accuracy.

First, analyze the absolute accuracy of RSSI. FIG. 6 is a relationship diagram of the absolute accuracy of the received signal strength indication of the two carriers of the device of the present invention. It can be known from equation (2) that the absolute accuracy of RSSI is only related to the AGC gain, but the receiver's operating bandwidth range is 60MHz, and the operating ambient temperature is -5°C to 55°C. The frequency response of many analog devices in the 60MHz bandwidth is inconsistent. For the same input power, there are differences in the detected values. In order to overcome this shortcoming and improve the reporting accuracy, the device of the present invention can be calibrated by frequency scanning, with 200kHz as the step size , Write down the difference between the detection and reference value in the range of 60MHz, and then store it in FLSH. Similar to the principle of frequency response, within the temperature range, the gain of the channel analog device changes greatly, resulting in a large error in RSSI detection. In order to reduce the impact of temperature changes on its accuracy, it is also necessary to scan the temperature, the step size 0.5°C or 1°C can be selected, and the corresponding data of the temperature and the detection difference are stored in the FLASH, and the difference between the frequency response and the temperature change needs to be compensated for each reported value, which can improve the absolute accuracy.

Next, analyze the relative accuracy of RSSI. The relative accuracy refers to the difference between the change of the input signal and the change of the detection value. FIG. 7 is a relationship diagram of the relative accuracy of the 2-carrier received signal strength indication of the device of the present invention. Assuming that the input signal power changes at a certain moment as ΔP, according to equation (2), it is known that the difference of RSSI detection values is k×ΔG _AGC , then the relative accuracy of RSSI is ΔP-k×ΔG _AGC . Since ΔP and k are constants, the relative accuracy of RSSI is only related to ΔG _AGC , that is to say, the relative accuracy of RSSI is only related to the AGC algorithm. To improve the relative accuracy, it means that the AGC linearity needs to be improved. In order to meet the requirements of linearity, the superior CORDIC algorithm is used to realize the I/Q amplitude operation and avoid the I ² /Q ² operation. This is conducive to the improvement of computing efficiency and the saving of chip hardware resources, and the CORDIC algorithm operation uses 8 clock cycles, so the accuracy calculated by the AGC gain can be 0.00013dB, which fully meets the accuracy requirements.

Finally, this detection device can also be used to detect multi-carrier receiver ACS (Adjacent Channel Selection), because RSSI indicates the power value of each carrier, and the ACS performance can be mapped through parameter changes, saving instruments and improving efficiency for future mass production.

Claims (4)

1. realize the device of multi-carrier receiving signal strength indication, it is characterized in that this device comprises: first radio-frequency filter, low noise amplifier, second radio-frequency filter, low-converter, intermediate frequency amplifier, variable gain controller, frequency overlapped-resistable filter, analog to digital converter and received signal processor; After radiofrequency signal is spuious outside the first radio-frequency filter filtering band, low noise amplifier amplifies, disturb by the second radio-frequency filter filtering frequency mixer mirror phase noise, the arrival low-converter carries out down-converted and converts intermediate-freuqncy signal to, after intermediate frequency amplifier, variable gain controller, deliver to through frequency overlapped-resistable filter and to carry out analog to digital conversion in the described A-D converter and become digital signal, at last, the received signal processor carries out digital demodulation, extraction, filtering to these digital signals and draws each carrier wave received signal intensity indication; Described received signal processor is by formula P _RSSI=k * (G _AGC-G _REF)+P _REF+ G _VGCObtain described each carrier wave received signal intensity indication; Wherein, G _AGCBe the gain of automatic gain control AGC, G _VGCBe the gain of variable controller, P _REF, k, G _REFBe constant.

2. device as claimed in claim 1 is characterized in that, described variable gain controller adopts numerical-control attenuator, occurs decay during at neighboring trace signal and block signal, and other situation following time is straight-through, and the decay controlling value is 0dB.

3. device as claimed in claim 1 or 2 is characterized in that, first radio-frequency filter adopts duplexer, low noise amplifier adopts SGA-4586, second radio-frequency filter adopts LE18A, and low-converter adopts SME1400B-17, and intermediate frequency amplifier adopts SGA-6486; The variable gain controller adopts AA113-310, and the anti-filter that mixes repeatedly adopts IF Surface Acoustic Wave Filter LE88F, and analog to digital converter adopts AD80101, received signal processor adopting ISL5416.

4. device as claimed in claim 3 is characterized in that, the IF-FRE f of described IF Surface Acoustic Wave Filter _IFBe 172.8MHz, sampling rate F _SBe 61.44MHz.

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