JP2012028918A - Receiver, program and method using under-sampling which eliminates image signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a receiver, a program and a method which can maintain a sampling frequency of an A/D converter at a low level by under-sampling and prevent waveform quality of input signals from being degraded by image signals generated by IQ mismatches.SOLUTION: The receiver has a quadrature demodulator converting a RF band signal into complex IF band signal, the A/D converter and a digital signal processor unit, and also has a switch unit controlled for passing each RF band signal. The digital signal processor unit extracts a desired signal and an image signal of the RF band signal, and calculates a correction coefficient of the image signal for each band signal. Then, the digital signal processor unit multiplies a complex conjugate signal in the image signal by the correction coefficient calculated for the other band signal corresponding to the image signal on a frequency axis of the desired signal, and substrates the multiplied signal from the desired signal of the RF band signal.

Description

  The present invention relates to a technique of a receiver using undersampling that simultaneously receives a plurality of RF (Radio Frequency) band signals.

  In recent years, with the development of wireless communication standards, communication capacity has been increased. In particular, according to IMT-Advanced, the goal is to achieve a transmission rate of 1 Gbps when stationary and several hundred Mbps even when moving. In order to achieve this goal, a frequency bandwidth of about 100 MHz is considered necessary. However, frequency resources are already tight, and it is very difficult to secure a continuous broadband at once.

  In order to solve this problem, there is a spectrum aggregation technique. “Spectrum aggregation” is a technique in which a plurality of bands whose frequency bands are separated from each other are bundled and transmitted simultaneously. According to this technique, a wide frequency band can be secured by using a plurality of bands simultaneously.

  Further, according to the field of cognitive radio technology, a technology for providing a user with a communication line in which a plurality of different communication systems are combined is being studied. In the case of this technology, the radio device needs to simultaneously receive a plurality of different RF band signals.

  In order to simultaneously receive a plurality of RF band signals, a receiving circuit is often provided for each RF band signal. In this case, there are problems that the cost increases and the circuit size increases. On the other hand, there is a technique in which a post-stage circuit of a quadrature demodulator of a receiver is shared and a plurality of RF band signals are received simultaneously (see, for example, Patent Document 1).

  FIG. 1 is a functional configuration diagram of a receiver in the prior art.

  FIG. 1 shows a receiver 1 that collectively samples three RF band signals (see, for example, Patent Document 1). Unnecessary frequency components are removed from each RF band signal received by the three antennas 10 by a band pass filter (BPF: Band Pass Filter) 11 for each system band. Next, the signal is amplified by a low noise amplifier (LNA) 12. The three amplified RF band signals are synthesized by the synthesizer 13. The synthesized RF band signal is input to the quadrature demodulator 14 as a frequency conversion function.

The quadrature demodulator (multiplier) 14 converts the RF band into an IF (Intermediate Frequency) band based on the local oscillation frequency f (sine wave) output from the single local frequency oscillator 140. The complex IF signal output from the quadrature demodulator 14 includes a signal having a frequency component of the sum and difference between the center frequency F _R1 of the first RF signal and the local oscillation frequency f, and the center frequency F of the second RF signal. A signal having a frequency component of the sum and difference between _R2 and the local oscillation frequency f, and a signal having a frequency component of the sum and difference between the center frequency F _R3 of the third RF signal and the local oscillation frequency f.

  The in-phase IF signal and the quadrature IF signal output from the quadrature demodulator 14 are respectively input to separate IF bandpass filters 15. The IF band pass filter 15 removes a signal having a sum frequency component from the IF signal. The IF signal in the predetermined pass band is input to the A / D converter 16. At this time, a band-pass filter can be used as the IF band-pass filter, and when there are a plurality of IF frequencies, a multi-band pass filter that passes signals of the plurality of IF frequencies is used. Remove signals outside the band.

  The A / D converter 16 performs frequency conversion collectively by undersampling. The sampling frequency Fs of the A / D converter 16 is output from the sampling clock generator 160. The sampling frequency Fs is based on an instruction from the processor unit (CPU) 17 and is appropriately selected so that the spectra of all desired signals after undersampling do not overlap each other. As a result, a Low-IF signal is output from the A / D converter 16. The Low-IF signal is input to the digital signal processor unit 18.

  “Undersampling” refers to a method of intentionally generating an aliasing image by sampling a received signal at a frequency lower than the Nyquist frequency and converting a high frequency carrier wave to a low frequency. Since the sampling frequency is low, the processing capability of the receiver can be relatively low, but a high-performance noise removal filter is required to reduce the influence of aliasing noise.

JP 2010-11376 A

Gye-Tae Gil, Young-Doo Kim, Lee, YH, KoreaTelecom, Daejeon, `` Non-Data-Aided Approach to I / Q Mismatch Compensation in Low-IF Receivers '', IEEE Transactions on signal processing, VOL. 55, NO. 7 , JULY2007, [online], [searched July 14, 2010], Internet <URL: http://ieeexplore.ieee.org/Xplore/login.jsp?url=http://ieeexplore.ieee.org/ iel5 / 78/4244638 / 04244676.pdf% 3Farnumber% 3D4244676 & authDecision = -203>

  FIG. 2 is an explanatory diagram showing an RF band signal and an image signal.

  FIG. 2A is an explanatory diagram when the sampling frequency of the A / D converter is increased. According to the functional configuration of the receiver in the prior art described above, it is preferable to keep the sampling frequency of the A / D converter low in order to save power in the A / D converter and the digital signal processing circuit. Here, when directly undersampling a plurality of RF band signals, it is necessary to set a sampling frequency as low as possible while preventing desired signals from overlapping on the frequency axis.

  According to FIG.2 (b), the signal after the frequency conversion by undersampling is set so that it may adjoin in the positive / negative area | region on a frequency axis. That is, the absolute value of the frequency of each signal after frequency conversion becomes equal in part or all. As a result, the sampling frequency can be kept low.

  However, there are cases where RF band signals interfere with each other due to an image signal generated by IQ mismatch of the receiving circuit. At this time, the waveform quality of the received signal is degraded.

  Therefore, the present invention provides a receiver, a program, and a method capable of suppressing the sampling frequency of the A / D converter to be low by undersampling and preventing deterioration of the waveform quality of the received signal due to an image signal caused by IQ mismatch. For the purpose.

According to the present invention, an antenna that simultaneously receives a plurality of RF (Radio Frequency) band signals, a combiner that combines a plurality of RF band signals, and a single unit that converts the combined RF band signals into complex IF band signals. In the receiver having the quadrature demodulator and the A / D converter that collectively undersamples the complex IF band signal at one sampling frequency Fs,
A switch unit that is switch-controlled to pass only one RF band signal between each antenna and the combiner;
A digital signal processor for extracting a desired signal from which an image signal has been removed from an IF band signal output from an A / D converter;
Digital signal processor
A quadrature demodulating means for extracting a desired signal and an image signal which is positive and negative on the frequency axis with respect to the desired signal;
Correction coefficient calculating means for calculating a correction coefficient of an image signal based on IQ mismatch for each band signal;
Complex conjugate arithmetic means for outputting a complex conjugate signal in the image signal;
Correction coefficient multiplication means for multiplying the complex conjugate signal by the correction coefficient calculated for the other band signal corresponding to the image signal on the frequency axis of the desired signal;
It is made to function as a subtraction means for subtracting a complex conjugate signal multiplied by a complex coefficient from a desired signal of an RF band signal.

  According to another embodiment of the receiver of the present invention, the digital signal processor unit further causes the desired signal and the image signal output from the quadrature demodulation unit to further function as a band pass filter unit that filters only a desired band. It is also preferable.

  According to another embodiment of the receiver of the present invention, before a plurality of RF band signals are received simultaneously, switching is sequentially controlled for each RF band signal with respect to the switch means, and a correction coefficient for each band signal is calculated. It is also preferred that

  According to another embodiment of the receiver of the present invention, the test signal switch for switching the input of the test signal provided in the previous stage of the switch means, and the test signal generator for supplying the test signal to the test signal switch are provided. It is also preferable to have it.

According to the present invention, an antenna that simultaneously receives a plurality of RF band signals, a combiner that combines the plurality of RF band signals, and a single quadrature demodulator that converts the combined RF band signal into a complex IF band signal. And a program for functioning a digital signal processor mounted on a receiver having an A / D converter that collectively undersamples a complex IF band signal at one sampling frequency Fs,
The receiver is switch-controlled to pass only one RF band signal between each antenna and the combiner,
The digital signal processor extracts the desired signal from which the image signal is removed from the IF band signal output from the A / D converter,
A quadrature demodulating means for extracting a desired signal and an image signal which is positive and negative on the frequency axis with respect to the desired signal;
Correction coefficient calculating means for calculating a correction coefficient of an image signal based on IQ mismatch for each band signal;
Complex conjugate arithmetic means for outputting a complex conjugate signal in the image signal;
Correction coefficient multiplication means for multiplying the complex conjugate signal by the correction coefficient calculated for the other band signal corresponding to the image signal on the frequency axis of the desired signal;
It is made to function as a subtraction means for subtracting a complex conjugate signal multiplied by a complex coefficient from a desired signal of an RF band signal.

  According to another embodiment of the program for the digital signal processor of the receiver of the present invention, it further functions as a band pass filter means for filtering only a desired band with respect to a desired signal and an image signal output from the quadrature demodulation means. It is also preferable that

  According to another embodiment of the program for the digital signal processor of the receiver of the present invention, before receiving a plurality of RF band signals at the same time, the switch means is sequentially switched and controlled for each RF band signal. It is also preferable that a correction coefficient for each signal is calculated.

According to the present invention, an antenna that simultaneously receives a plurality of RF band signals, a combiner that combines the plurality of RF band signals, and a single quadrature demodulator that converts the combined RF band signal into a complex IF band signal. And a digital signal processing method in a receiver having an A / D converter that collectively undersamples a complex IF band signal at one sampling frequency Fs,
The receiver is switch-controlled to pass only one RF band signal between each antenna and the combiner,
In order to extract the desired signal from which the image signal has been removed from the IF band signal output from the A / D converter,
A first step of extracting a desired signal and an image signal that is positive and negative on the frequency axis with respect to the desired signal;
A second step of calculating a correction coefficient of the image signal based on IQ mismatch for each band signal;
A third step of outputting a complex conjugate signal in the image signal;
A fourth step of multiplying the complex conjugate signal by a correction coefficient calculated for the other band signal corresponding to the image signal on the frequency axis of the desired signal;
And a fifth step of subtracting the complex conjugate signal multiplied by the complex coefficient from the desired signal of the RF band signal.

  According to the receiver, program, and method of the present invention, the sampling frequency of the A / D converter can be kept low by undersampling, and deterioration of the waveform quality of the received signal due to the image signal caused by IQ mismatch can be prevented.

It is a functional block diagram of the receiver in a prior art. It is explanatory drawing showing an RF band signal and an image signal. It is a functional block diagram in the receiver of this invention. It is explanatory drawing showing three RF band signals. It is a function block diagram inside DSP. It represents the complex signal sequence r _n in the case where only the first RF band signal is passed. It represents the complex signal sequence r _n in the case where only the second RF band signal is passed. It represents the complex signal sequence r _n in the case where only the third RF band signal is passed. It is a functional block diagram of the receiver using a test signal generator. It is explanatory drawing showing arrangement | positioning of RF band signal different from FIGS. It is a function block diagram inside DSP corresponding to FIG. It represents the complex signal sequence r _n in the case where only the first RF band signal is passed. It represents the complex signal sequence r _n in the case where only the second RF band signal is passed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 3 is a functional configuration diagram of the receiver according to the present invention.

  The receiver 1 of FIG. 3 is provided with a switch 21 between the low noise amplifier (LNA) 12 and the combiner 13 for each RF band signal, as compared with FIG. The switch 21 has two inputs and one output, and the first input is connected to the LNA 13 and the second input is terminated. The output of the switch 21 is connected to the combiner 13. Note that switching of the input port of the switch 21 is controlled by the processor 17. The RF band signals output from the three switches 21 are combined by the combiner 13 and input to the quadrature demodulator 14.

  The quadrature demodulator 14 converts the frequency of the RF band signal into an IF band signal. Among the frequency components generated by the quadrature demodulator 14 multiplying the local oscillation frequency, the sum frequency component is removed by the band pass filter 15. As a result, the A / D converter 16 receives the IF signal frequency-converted to the intermediate frequency of the difference between the carrier frequency of each band and the local oscillation frequency in the three band signals.

  According to FIG. 3, the processor 17 adjusts the local oscillation frequency of the local frequency oscillator 140 and the sampling frequency of the A / D converter 16. This adjusts the position on the frequency axis of the Low-IF band signal after frequency conversion in undersampling. The local oscillation frequency and the sampling frequency are the same as those set in the prior art in FIG.

  FIG. 4 is an explanatory diagram showing three RF band signals.

According to FIG. 4A, for example, it is assumed that the following carrier frequency and bandwidth are used as the RF band signal.
First RF band signal S ₁ : carrier frequency 1442.5 MHz, bandwidth 5 MHz
Second RF band signal S ₂ : carrier frequency 817.5 MHz, bandwidth 5 MHz
Third RF band signal S ₃ : carrier frequency 1930 MHz, bandwidth 10 MHz

Further, according to the configuration of FIG. 3 described above, it is assumed that the following settings are made.
Local oscillation frequency: 1375MHz
A / D converter sampling frequency: 20 MHz
Each band frequency in Low-IF band:
fIF1 = + 7.5MHz
fIF2 = + 2.5MHz
fIF3 = -5MHz

FIG. 4B shows an image signal of each band signal affected by IQ mismatch in the quadrature demodulator. The image signals of the first RF band signal S ₁ and the second RF band signal S ₂ interfere with the _third RF band signal S ₃ . The third image signal of the RF band signal _{S 3} of the interfering first to RF band signals S ₁ and the second RF band signal _{S 2.}

  FIG. 5 is a functional configuration diagram inside the DSP.

According to FIG. 5, the input sequence of the in-phase component from the A / D converter is r _I and the input sequence of the quadrature component from the A / D converter is r _Q. Here, the input sequence of the orthogonal component to the r _Q, multiplying the complex sequence j. Then, both the input sequence r _I and synthesizing the j × r _Q, to obtain a complex signal sequence r _n.
r _n = r _I + j × r _Q

Figure 6 shows the complex signal sequence r _n in the case where only the first RF band signal is passed.

Only the switch 21 for the first RF band signal is connected to the LNA side, and the switch 21 for the other band signal is connected to the termination side. This control is executed by the processor 17. Thus, complex signal sequence r _n only the first RF band signal has passed is input. Here, the complex signal sequence r _n, (see FIG. 6 (a)) including a first RF band signal S _1, and the image signal S ₁ '.

The first signal processing unit includes an orthogonal demodulation unit 183, a band pass filter 184, a correction coefficient calculation unit 185, a complex conjugate calculation unit 186, a correction coefficient multiplication unit 187, and a subtraction unit 188. and it outputs the data series S _1. These functional components are realized by executing a program for the digital signal processor.

The orthogonal demodulator 183 extracts a desired signal of the band signal and an image signal that is positive / negative on the frequency axis with respect to the desired signal. Desired signal is obtained by multiplying the e ^-J2paifIF1nT by the multiplier into a complex signal sequence r _n (T: inverse number of the sampling frequency 20 MHz, n: positive integer) (see Figure 6 (b)). The image signal is obtained by multiplying e ^J2paifIF1nT by the multiplier into a complex signal sequence r _n (see Figure 6 (c)).

The band pass filter 184 applies, for example, a low pass filter having a pass bandwidth of 5 MHz to each of the desired signal and the image signal output from the quadrature demodulation unit 183. Here, the pass bandwidth of the low-pass filter represents a bandwidth obtained by combining positive and negative frequencies. Looking only at the positive frequency region, it becomes a low-pass filter with a passband width of 2.5 MHz. The desired signal output from the band pass filter 184 is represented as X _1n and the image signal is represented as Z _1n .

The correction coefficient calculation unit 185 calculates the correction coefficient of the image signal based on the IQ mismatch for each RF band signal. The correction coefficient is calculated using X _1n and Z _1n . Many calculation methods have been proposed as existing technologies. For example, according to Prior Art Document 2, the correction coefficient α1 can be calculated as follows using N input sequences (n = 0, 1,..., N−1) of X _1n and Z _1n. it can. The calculated correction coefficient α ₁ is held.

  The complex conjugate calculation unit 186 outputs a complex conjugate signal in the image signal. Complex conjugation is the exchange of the sign of the imaginary part of a complex number.

The correction coefficient multiplication unit 187 multiplies the complex conjugate signal by the correction coefficient calculated for the other band signal corresponding to the image signal on the frequency axis of the desired signal. Here, for example, the image signal of the third RF band signal interferes on the frequency axis of the desired signal of the first RF band signal. Therefore, the complex conjugate signal is multiplied by the correction coefficient α _{3 of} the third RF band signal.

The subtracting unit 188 subtracts the complex conjugate signal of Z _1n multiplied by the complex coefficient from the desired signal X _1n of the RF band signal. The signal after the subtraction is the desired signal S1 in the _first RF band signal, and the image signal of the other RF band signal is removed.

Figure 7 represents a complex signal sequence r _n in the case where only the second RF band signal is passed.

Only the switch 21 for the second RF band signal is connected to the LNA side, and the switch 21 for the other band signal is connected to the termination side. Thus, complex signal sequence r _n only the second RF band signal has passed is input. Here, the complex signal sequence r _n, (see FIG. 7 (a)) including a second RF band signal _{S 2,} and the image signal _{S 2} '.

According to a second signal processing unit, the quadrature demodulator 183, the desired signal is obtained by multiplying the e ^-J2paifIF2nT the complex signal sequence r _n (see FIG. 7 (b)). The image signal is obtained by multiplying the e ^J2paifIF2nT the complex signal sequence r _n (see FIG. 7 (c)).

The band pass filter 184 applies, for example, a low pass filter having a pass bandwidth of 5 MHz to each of the desired signal and the image signal output from the quadrature demodulation unit 183. The desired signal output from the band pass filter 184 is represented as X _2n, and the image signal output from the band pass filter 184 is represented as Z _2n .

  The correction coefficient calculation unit 185 calculates the correction coefficient of the image signal based on the IQ mismatch in the second RF band signal.

The complex conjugate calculation unit 186 outputs a complex conjugate signal in the image signal. Here, for example, the image signal of the third RF band signal interferes on the frequency axis of the desired signal of the second RF band signal. Therefore, the correction coefficient multiplication unit 187 multiplies the complex conjugate signal by the correction coefficient α ₃ calculated for the third RF band signal corresponding to the image signal on the frequency axis of the desired signal. The subtracting unit 188 subtracts the complex conjugate signal of Z _2n multiplied by the complex coefficient from the desired signal X _2n of the RF band signal. The signal after the subtraction is the desired signal S2 in the _second RF band signal, and the image signal of the other RF band signal is removed.

Figure 8 represents a complex signal sequence r _n in the case where only the third RF band signal is passed.

Only the switch 21 for the third RF band signal is connected to the LNA side, and the switch 21 for the other band signal is connected to the termination side. Thus, complex signal sequence r _n that only the third RF band signal has passed is input. Here, the complex signal sequence r _n, (see FIG. 8 (a)) including a third RF band signal S _3, and the image signal S ₃ '.

According to a third signal processing unit, the quadrature demodulator 183, the desired signal is obtained by multiplying the e ^-J2paifIF3nT the complex signal sequence r _n (see FIG. 7 (b)). The image signal is obtained by multiplying the e ^J2paifIF3nT the complex signal sequence r _n (see FIG. 7 (c)).

The band pass filter 184 filters only the desired band for each of the desired signal and the image signal output from the quadrature demodulator 183. For example, a low pass filter with a pass bandwidth of 10 MHz is applied. The desired signal output from the band pass filter 184 is represented as X _3n, and the image signal output from the band pass filter 184 is represented as Z _3n .

  The correction coefficient calculation unit 185 calculates the correction coefficient of the image signal based on the IQ mismatch in the third RF band signal.

The image signals of the first and second RF band signals interfere on the frequency axis of the desired signal of the third RF band signal. Therefore, the following signal is subtracted from the desired signal X _3n of the third band signal.
(1) Complex frequency conversion is ^performed by multiplying the complex signal sequence r _n by e ^{−j2πfIF1nT} , and the signal X _{1n obtained} by applying a low-pass filter with a 5 MHz pass bandwidth is multiplied by e ^{−j2π (−fIF3−fIF1) nT} to be complex. A signal obtained by multiplying the complex conjugate signal of the frequency-converted signal by the correction coefficient α ₁ is subtracted.
(2) Complex signal sequence r _n is multiplied by e ^{−j2πfIF2nT} to perform complex frequency conversion, and signal X _2n having a low-pass filter with a pass bandwidth of 5 MHz is multiplied by e ^{−j2π (−fIF3−fIF2) nT} to be complex. A signal obtained by multiplying the complex conjugate signal of the frequency converted signal by the correction coefficient α ₂ is further subtracted.
The signal after the subtraction is the desired signal S ₃ in the _third RF band signal, and the image signal of the other RF band signal is removed.

As described above, the correction coefficients α ₁ , α ₂ , and α ₃ are calculated by sequentially controlling the switch unit 21 for each RF band signal. Thereafter, a plurality of RF band signals are received simultaneously, and the digital signal processor executes the first to third signal processing units in parallel, whereby the desired signals S ₁ , S ₂ , S ₃ from which the image signal has been removed are obtained. can get.

  FIG. 9 is a functional configuration diagram of a receiver using the test signal generator.

  According to FIG. 9, compared to FIG. 3, the test signal switch 23 that switches the input of the test signal, provided in the previous stage of the switch unit 21, and the test signal generator 22 that supplies the test signal to the test signal switch 23. It has further. By using a certain test signal as the RF band signal, an appropriate correction factor can be derived. The test signal switch 23 and the test signal generator 22 are controlled by the processor 17.

  FIG. 10 is an explanatory diagram showing the arrangement of RF band signals different from those in FIGS.

According to FIG. 10, for example, it is assumed that the following bandwidth is used as the RF band signal.
First RF band signal S ₁ : Bandwidth 15 MHz
Second RF band signal S ₂ : bandwidth 5 MHz
Each band frequency in Low-IF band:
fIF1 = -2.5MHz
fIF2 = + 7.5MHz
As shown in FIG. 10, the band signal after undersampling exists in both positive and negative regions on the frequency axis.

  FIG. 11 is a functional configuration diagram inside the DSP corresponding to FIG.

Figure 12 represents a complex signal sequence r _n in the case where only the first RF band signal is passed.

The first signal processing unit for the first RF band signal functions as follows.
(1) The complex signal sequence r _n is multiplied by e ^{−j2πfIF1nT} to perform complex frequency conversion, and a signal X _1n obtained by applying a low-pass filter with a pass bandwidth of 15 MHz is obtained. Further, the signal X _1n is multiplied by ^ej2πfIF1nT to perform complex frequency conversion. A signal obtained by multiplying the complex conjugate signal of the signal by the correction coefficient α ₁ is subtracted from the signal after the complex frequency conversion.
(2) Further, converts the complex frequency by multiplying e ^-J2paifIF2nT the complex signal sequence r _n, to obtain a signal X _2n multiplied by the low-pass filter passband width 5 MHz. The signal X _2n is multiplied by e ^−j2πf0nT to perform complex frequency conversion. A signal obtained by multiplying the complex conjugate signal of the signal after the complex frequency conversion by the correction coefficient α ₂ is subtracted. Note that f0 = 2.5 MHz.
The signal after the subtraction is the desired signal S1 in the _first RF band signal, and the image signal of the other RF band signal is removed.

13 denotes a complex signal sequence r _n in the case where only the second RF band signal is passed.

The second signal processing unit for the second RF band signal functions as follows.
(1) The complex signal sequence r _n is multiplied by e ^{−j2πfIF2nT} to perform complex frequency conversion, and a signal X _2n obtained by applying a low-pass filter with a pass bandwidth of 5 MHz is obtained.
(2) by multiplying e ^J2paifIF2nT the complex signal sequence r _n and the complex frequency conversion, and subtracts a signal obtained by multiplying the correction coefficient alpha ₁ to the complex conjugate signal of the signal Z _2n multiplied by the low-pass filter passband width 5 MHz.
The signal after the subtraction is the desired signal S2 in the _second RF band signal, and the image signal of the other RF band signal is removed.

  As described above in detail, according to the receiver, program and method of the present invention, the sampling frequency of the A / D converter is kept low by undersampling, and the waveform quality of the received signal due to the image signal caused by IQ mismatch. Can be prevented.

  Various changes, modifications, and omissions of the above-described various embodiments of the present invention can be easily made by those skilled in the art. The above description is merely an example, and is not intended to be restrictive. The invention is limited only as defined in the following claims and the equivalents thereto.

DESCRIPTION OF SYMBOLS 1 Receiver 10 Antenna 11 Band pass filter for RF band, RF-BPF
12 Low noise amplifier, LNA
13 Synthesizer 14 Quadrature Demodulator 140 Local Frequency Oscillator 15 Bandpass Filter for IF Band, IF-BPF
16 A / D converter 160 Sampling clock generator 17 Processor unit 18 DSP unit, digital signal processor unit 181 Multiplying unit 182 Combining unit 183 Orthogonal demodulating unit 184 Band pass filter 185 Correction coefficient calculation unit 186 Complex conjugate arithmetic unit 187 Correction coefficient multiplication Section 188 Subtraction section 21 Switch section 22 Test signal switch section 23 Test signal generator

Claims (8)

An antenna that simultaneously receives a plurality of RF (Radio Frequency) band signals, a synthesizer that synthesizes a plurality of RF band signals, a single quadrature demodulator that converts the synthesized RF band signals into complex IF band signals, In a receiver having an A / D converter that collectively undersamples the complex IF band signal at one sampling frequency Fs,
A switch unit that is switch-controlled to pass only one RF band signal between each antenna and the combiner;
A digital signal processor for extracting a desired signal from which an image signal has been removed from an IF band signal output from the A / D converter;
The digital signal processor unit is
Quadrature demodulation means for extracting the desired signal and an image signal that is positive and negative on the frequency axis with respect to the desired signal;
Correction coefficient calculating means for calculating a correction coefficient of an image signal based on IQ mismatch for each band signal;
Complex conjugate calculation means for outputting a complex conjugate signal in the image signal;
Correction coefficient multiplication means for multiplying the complex conjugate signal by the correction coefficient calculated for the other band signal corresponding to the image signal on the frequency axis of the desired signal;
A receiver which functions as subtraction means for subtracting a complex conjugate signal multiplied by a complex coefficient from a desired signal of the RF band signal.   The said digital signal processor part is further made to function as a bandpass filter means which filters only a desired band with respect to the said desired signal and the said image signal output from the said orthogonal demodulation means. Receiver.   3. The correction coefficient for each band signal is calculated by sequentially switching the RF signal for each RF band signal before receiving a plurality of RF band signals simultaneously. As described in the receiver. A test signal switch for switching the input of the test signal, provided in the previous stage of the switch means;
The receiver according to any one of claims 1 to 3, further comprising a test signal generator for supplying a test signal to the test signal switch. An antenna that simultaneously receives a plurality of RF band signals, a combiner that combines the plurality of RF band signals, a single quadrature demodulator that converts the combined RF band signal into a complex IF band signal, and the complex IF band In a program for functioning a digital signal processor mounted on a receiver having an A / D converter that undersamples signals at a single sampling frequency Fs at a time,
The receiver is switch-controlled to pass only one RF band signal between each antenna and the combiner,
The digital signal processor extracts a desired signal from which an image signal is removed from an IF band signal output from the A / D converter,
Quadrature demodulation means for extracting the desired signal and an image signal that is positive and negative on the frequency axis with respect to the desired signal;
Correction coefficient calculating means for calculating a correction coefficient of an image signal based on IQ mismatch for each band signal;
Complex conjugate calculation means for outputting a complex conjugate signal in the image signal;
Correction coefficient multiplication means for multiplying the complex conjugate signal by the correction coefficient calculated for the other band signal corresponding to the image signal on the frequency axis of the desired signal;
A program for a digital signal processor of a receiver, which functions as subtraction means for subtracting a complex conjugate signal multiplied by a complex coefficient from a desired signal of the RF band signal.   6. The digital signal processor of a receiver according to claim 5, wherein said desired signal and said image signal output from said quadrature demodulating means are further functioned as band pass filter means for filtering only a desired band. Program.   7. The correction coefficient for each band signal is calculated by sequentially controlling the switch means for each RF band signal before simultaneously receiving a plurality of RF band signals. A program for the digital signal processor of the receiver described in 1. An antenna that simultaneously receives a plurality of RF band signals, a combiner that combines the plurality of RF band signals, a single quadrature demodulator that converts the combined RF band signal into a complex IF band signal, and the complex IF band In a digital signal processing method in a receiver having an A / D converter that collectively undersamples a signal at one sampling frequency Fs,
The receiver is switch-controlled to pass only one RF band signal between each antenna and the combiner,
In order to extract the desired signal from which the image signal has been removed from the IF band signal output from the A / D converter,
A first step of extracting the desired signal and an image signal that is positive and negative on the frequency axis with respect to the desired signal;
A second step of calculating a correction coefficient of the image signal based on IQ mismatch for each band signal;
A third step of outputting a complex conjugate signal in the image signal;
A fourth step of multiplying the complex conjugate signal by the correction coefficient calculated for the other band signal corresponding to the image signal on the frequency axis of the desired signal;
And a fifth step of subtracting a complex conjugate signal multiplied by a complex coefficient from a desired signal of the RF band signal.

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