JP4863307B2 - Receiver, program and method using undersampling - Google Patents

Description

  The present invention relates to a receiver, a program, and a method using undersampling that collectively samples a plurality of system bands.

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

  FIG. 1A shows a receiver 1 that samples two system bands together (see, for example, Patent Document 1). Unnecessary frequency components are removed from each RF (Radio Frequency) signal received by the two antennas 101 by a band pass filter (BPF) 102 for each system band. Next, the signal is amplified by a low noise amplifier (LNA) 103. The two amplified RF signals are added by an adder and input to the A / D converter 104. The A / D converter 104 performs frequency conversion collectively by undersampling. The sampling frequency Fs of the A / D converter 104 is output from the sampling clock generation unit 105. The sampling frequency Fs is based on an instruction from the processor unit (CPU) 100, and is appropriately selected so that the spectra of all desired signals after undersampling do not overlap each other. The digital signal output from the A / D converter 104 may be demodulated by, for example, FFT (Fast Fourier Transform).

  According to FIG. 1 (b), another embodiment in the prior art is represented by a broken line. According to this embodiment, for each RF band amplified by the low noise amplifier 103, Low-IF (Intermediate Frequency, Low Frequency) whose frequency is suppressed by the mixer 112 in accordance with the local oscillation frequency output from the local frequency oscillator 111. Intermediate frequency) band. Here, by setting different local oscillation frequencies for each desired signal in the system band, the desired signals are prevented from overlapping each other. Unnecessary frequency components are removed by the low-pass filter 113 for the low-IF band signal including the low-frequency desired signal and the low-IF band signal for the low-IF band signal including the high-frequency desired signal by the band-pass filter 114. The The signals in the two IF bands are added by an adder, and then oversampled collectively by an A / D converter.

  “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 (see Non-Patent Document 1, for example). ). 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. Conversely, “oversampling” refers to a method of sampling a received signal at a frequency higher than the Nyquist frequency. Since the sampling frequency is high, the design of a filter for noise removal can be simplified, but a high processing capability is required for the receiver.

  FIG. 2 is an image diagram of frequency components when undersampling is used.

  According to FIG. 2, the horizontal axis represents the frequency. By sampling using the undersampling frequency Fs, aliasing occurs in a low frequency band below the frequency Fs / 2.

The following function is defined, and the following baseband signal F _BB is derived with respect to the sampling frequency Fs at the time of undersampling.
N = fix (Fc / (Fs / 2))
N = fix (a): Function that rounds off the decimal part of a
rem (a, b): a function for obtaining a remainder obtained by dividing a by b When N is an even number, F _BB = rem (Fc, Fs)
= Fc-N * (Fs / 2)
When N is an odd number, F _BB = Fs−rem (Fc, Fs)
= (N + 1) * Fs / 2-Fc

  FIG. 2A shows that the folding of the frequency signal occurs every half of the sampling frequency (Fs / 2). Here, the number of times of folding is six. The number N of times that the center frequency Fc of the system band is turned back is calculated by Fc / (Fs / 2) by the above formula. The calculated value is truncated by fix (). The position of the image in the aliasing system band varies depending on the even / odd value N obtained by the above equation. The orientation of the aliasing system band image can also be changed by the local oscillation frequency. For example, when the pass band of the band pass filter is narrow, there is a possibility that even if the number of times of folding is increased only once, there is a possibility that the band pass filter will deviate from the pass band of the filter. Need to be changed.

  FIG. 2B shows an aliasing system band that is folded back to Fs / 2 or less when the number of times of folding N is an even number.

  FIG. 2C shows an aliasing system band that is folded back to Fs / 2 or less when the number of times of folding N is an odd number.

  As a technique using undersampling, there is a sampling frequency search method and program technique capable of searching for the lowest possible sampling frequency when sampling a plurality of wireless system bands for each system band (for example, Patent Document 2). And Patent Document 3). According to this technique, the lowest possible sampling frequency Fs can be searched, so that a high-speed A / D converter is not required, the amount of data for digital signal processing can be reduced, and power consumption is further reduced. Bring.

  There is also a technique for calculating a sampling frequency range in which a plurality of RF signals received simultaneously are not overlapped with each other after sampling by using undersampling (see, for example, Non-Patent Document 2). In this technique, cases are classified according to the positional relationship of folding caused by sampling of each RF signal, and an available sampling frequency is calculated from the number of undersampling and the frequency of the RF signal.

JP 2001-274714 A JP 2001-335914 A JP 2006-180373 A Dennis M. Akos, Michael Stockmaster, JamesB. Y. Tsui and Joe Caschera "Direct Bandpass Sampling of Multiple Distinct RF Signals", IEEE Transactions on communications, vol.47, No.7, July 1999, pp.983-988 Ching-Hsiang Tseng and Sun-Chung Chou, "DirectDownconversion of Multiband RF Signals Using BandpassSampling," IEEE Trans.Commun., Vol.5, no.1, Jan. 2006.

According to the technique described in Patent Document 1, the RF signal is directly undersampled. Therefore, when the frequency band of the desired signal is high, the noise figure degradation or the influence of sampling jitter becomes significant. The noise figure is a decibel notation of the ratio between the input signal SNRin and the output signal SNRout, and is represented by NF = ₁₀ log ₁₀ (SNRin / SNRout). The greater the difference in SNR between the input signal and the output signal (the greater the influence of noise), the more the noise figure NF degrades (the NF value increases).

  Further, depending on the frequency arrangement of the desired signal, it is necessary to set the sampling frequency Fs high, and the power consumption in the A / D converter increases.

  Further, according to the technique described in Patent Document 2, a band-pass filter that removes unnecessary frequency components is required for the converted signal in the Low-IF band. It is difficult to realize a steep band-pass filter that can attenuate unnecessary components in a low frequency band.

  Therefore, the present invention reduces the influence of noise figure degradation or sampling jitter, facilitates the design of a band-pass filter, and uses a receiver using undersampling that can set the sampling frequency Fs low, The purpose is to provide a program and method.

According to the present invention, a receiver having an antenna for receiving an RF (Radio Frequency) signal including two system bands,
A first RF band included in the RF signal is converted into a first IF (Intermediate Frequency) band F _IF1 by using the first local oscillation frequency F _LO1 output from the first local frequency oscillator. Frequency conversion means,
Second frequency converting means for converting the second RF band included in the RF signal into the second IF band F _IF2 by using the second local oscillation frequency F _LO2 output from the second local frequency oscillator. When,
A / D conversion that outputs a BB (Base Band) signal obtained by sampling the IF signal obtained by adding the first IF band F _IF1 and the second IF band F _IF2 at one sampling frequency Fs by undersampling. And
Based on the sampling frequency Fs, the first local oscillation frequency F _LO1 and the second local oscillation frequency F _LO2 calculated so that the system bands or desired signals do not interfere with each other in the frequency domain are respectively used as the first local frequency oscillator. and it possesses a processor means for instructing the second local frequency oscillator,
The processor means is
The center frequency F _R1 and bandwidth B ₁ of the first RF band or desired signal and the center frequency F _R2 and bandwidth B _{2 of} the second RF band or desired signal are set as initial values, and the system bands or desired signals are set as initial values. The first BB band or the center frequency F _BB1 of the desired signal, the second BB band or the center frequency F _{BB2 of the} desired signal, and the sampling frequency Fs are arbitrarily selected so that they do not interfere with each other in the frequency domain ,
The local oscillating frequency of the local frequency oscillator is controlled by defining the first BB band or desired signal folding number N ₁ and the second BB band or desired signal folding number N _{2 in} undersampling. By
F _L01 = F _R1 ± {(N ₁ +1) / 2 × Fs−F _BB1 } (N ₁ mod 2 ≠ 0)
_{F R1 ± {N 1/2} × Fs + F BB1} (N 1 mod 2 = 0)
F _L02 = F _R2 ± {(N ₂ +1) / 2 × Fs−F _BB2 } (N ₂ mod 2 ≠ 0)
_{F R2 ± {N 2/2} × Fs + F BB2} (N 2 mod 2 = 0)
To calculate the first local oscillation frequency _FL01 and the second local oscillation frequency _FL02 .

According to another embodiment in the receiver of the invention, the processor means is
The center frequency F _R1 and bandwidth B ₁ of the first RF band and the center frequency F _R2 and bandwidth B _{2 of} the second RF band are set as initial values,
F _BB1 -B _1/2> 0
_{F BB1 + B 1/2 <} F BB2 -B 2/2
_{F BB2 + B 2/2 <} Fs / 2
Or F _BB2 -B _2/2> 0
_{F BB2 + B 2/2 <} F BB1 -B 1/2
_{F BB1 + B 1/2 <} Fs / 2
It is also preferable to arbitrarily select the center frequency F _BB1 of the first BB band, the center frequency F _BB2 of the second BB band, and the sampling frequency Fs that satisfy the above condition value.

According to another embodiment in the receiver of the invention, the processor means is
The center frequency F _Rch1 and bandwidth B _ch1 of the first RF desired signal and the center frequency F _Rch2 and bandwidth B _{ch2 of} the second RF desired signal are set as initial values.
_{Fs / 2- (F BBch1 + B} ch1 / 2)> (F BBch1 + B 1/2) -Fs / 2
_{(F BBch1 -B ch1 / 2)} > - (F BB1 -B 1/2)
_{Fs / 2- (F BBch2 + B} ch2 / 2)> (F BBch2 + B 2/2) -Fs / 2
_{(F BBch2 -B ch2 / 2)} > - (F BB2 -B 2/2)
_{| F BBch2 -F BB1 | <B} ch2 / 2 + B 1/2
_{| F BBch1 -F BB2 | <B} ch1 / 2 + B 2/2
It is also preferable to arbitrarily select the center frequency F _BB1 of the first BB band, the center frequency F _BB2 of the second BB band, and the sampling frequency Fs that satisfy the above condition value.

According to another embodiment of the receiver of the present invention, the processor means comprises a frequency between the center frequency F _IF1 of the desired signal in the first IF band and the center frequency F _IF2 of the desired signal in the second IF band. It is also preferable to select the interval to be smaller than the frequency interval between the center frequency F _R1 of the desired signal in the first RF band and the center frequency F _R2 of the desired signal in the second RF band.

According to another embodiment of the receiver of the present invention,
The first frequency conversion means is
A first RF band pass filter for extracting a first RF band F _R1 included in the RF signal;
A first mixer for converting the first RF band F _R1 into a first IF signal using the first local oscillation frequency F _LO1 output from the first local frequency oscillator;
A first IF band pass filter for extracting a first IF band F _IF1 from the first IF signal;
The second frequency conversion means is
A second RF band pass filter for extracting a second RF band F _R2 included in the RF signal;
A second mixer for converting the second RF band F _R2 into a second IF signal using the second local oscillation frequency F _LO2 output from the second local frequency oscillator;
It is also preferable to have a second IF bandpass filter that extracts the second IF band _IF2 from the second IF signal.

According to the present invention,
An antenna for receiving an RF signal including two system bands;
First frequency converting means for converting the first RF band included in the RF signal into the first IF band F _IF1 by using the first local oscillation frequency F _LO1 output from the first local frequency oscillator. When,
Second frequency converting means for converting the second RF band included in the RF signal into the second IF band F _IF2 by using the second local oscillation frequency F _LO2 output from the second local frequency oscillator. When,
An A / D converter that outputs a BB signal obtained by sampling the IF signal obtained by adding the first IF band F _IF1 and the second IF band F _IF2 at one sampling frequency Fs by undersampling; A program for causing a computer installed in a receiver to function,
A first step in which the center frequency F _R1 and bandwidth B ₁ of the first RF band or desired signal and the center frequency F _R2 and bandwidth B _{2 of} the second RF band or desired signal are initial values;
The first BB band or the center frequency F _BB1 of the desired signal, the second BB band or the center frequency F _{BB2 of the} desired signal, and the sampling frequency Fs are arbitrarily set so that the system bands or the desired signals do not interfere with each other in the frequency domain. A second step of selecting;
The local oscillating frequency of the local frequency oscillator is controlled by defining the first BB band or desired signal folding number N ₁ and the second BB band or desired signal folding number N _{2 in} undersampling. By
F _L01 = F _R1 ± {(N ₁ +1) / 2 × Fs−F _BB1 } (N ₁ mod 2 ≠ 0)
_{F R1 ± {N 1/2} × Fs + F BB1} (N 1 mod 2 = 0)
F _L02 = F _R2 ± {(N ₂ +1) / 2 × Fs−F _BB2 } (N ₂ mod 2 ≠ 0)
_{F R2 ± {N 2/2} × Fs + F BB2} (N 2 mod 2 = 0)
To calculate the first local oscillation frequency F _L01 and the second local oscillation frequency F _L02 , and the first local oscillation frequency F _LO1 and the second local oscillation frequency F _LO2 , respectively. The computer is executed as a fourth step for instructing the frequency oscillator and the second local frequency oscillator.

According to the present invention,
An antenna for receiving an RF signal including two system bands;
First frequency converting means for converting the first RF band included in the RF signal into the first IF band F _IF1 by using the first local oscillation frequency F _LO1 output from the first local frequency oscillator. When,
Second frequency converting means for converting the second RF band included in the RF signal into the second IF band F _IF2 by using the second local oscillation frequency F _LO2 output from the second local frequency oscillator. When,
An A / D converter that outputs a BB signal obtained by sampling the IF signal obtained by adding the first IF band F _IF1 and the second IF band F _IF2 at one sampling frequency Fs by undersampling; An undersampling method in a receiver,
A first step in which the center frequency F _R1 and bandwidth B ₁ of the first RF band or desired signal and the center frequency F _R2 and bandwidth B _{2 of} the second RF band or desired signal are initial values;
The first BB band or the center frequency F _BB1 of the desired signal, the second BB band or the center frequency F _{BB2 of the} desired signal, and the sampling frequency Fs are arbitrarily set so that the system bands or the desired signals do not interfere with each other in the frequency domain. A second step of selecting;
The local oscillating frequency of the local frequency oscillator is controlled by defining the first BB band or desired signal folding number N ₁ and the second BB band or desired signal folding number N _{2 in} undersampling. By
F _L01 = F _R1 ± {(N ₁ +1) / 2 × Fs−F _BB1 } (N ₁ mod 2 ≠ 0)
_{F R1 ± {N 1/2} × Fs + F BB1} (N 1 mod 2 = 0)
F _L02 = F _R2 ± {(N ₂ +1) / 2 × Fs−F _BB2 } (N ₂ mod 2 ≠ 0)
_{F R2 ± {N 2/2} × Fs + F BB2} (N 2 mod 2 = 0)
To calculate the first local oscillation frequency F _L01 and the second local oscillation frequency F _L02 , and the first local oscillation frequency F _LO1 and the second local oscillation frequency F _LO2 , respectively. And a fourth step for instructing the frequency oscillator and the second local frequency oscillator.

  According to the receiver, program, and method of the present invention, the frequency band of the RF band is converted to the IF band, and the IF band is undersampled, thereby reducing the noise figure degradation or the influence of sampling jitter and reducing the IF band. The design of the band pass filter for the signal becomes easy. Further, by controlling the local oscillation frequency at the time of frequency conversion to the IF band, it is possible to derive a low sampling frequency Fs in which a plurality of desired signals after undersampling do not overlap each other.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

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

  According to FIG. 3, it has the 1st frequency conversion part 210 and the 2nd frequency conversion part 220 compared with Fig.1 (a). The first frequency conversion unit 210 and the second frequency conversion unit 220 perform frequency conversion from the RF band to the IF band, and change the local oscillation frequency based on control from the processor unit 200.

The first frequency converter 210 converts the first RF band included in the RF signal into the first IF band F _IF1 by using the first local oscillation frequency F _LO1 output from the first local frequency oscillator. Convert to Here, the first frequency converter 210 includes a first local frequency oscillator 211 for outputting a first local oscillator frequency F _LO1, using a first local oscillator frequency F _LO1, first RF band F _A first mixer 212 that converts _R1 into a first IF signal, and a first IF bandpass filter 213 that extracts a first IF band _FIF1 from the first IF signal.

The second frequency converter 220 uses the second local oscillation frequency F _LO2 output from the second local frequency oscillator to convert the second RF band included in the RF signal into the second IF band F _IF2. Convert to Here, the second frequency converting unit 220 includes a second local frequency oscillator 221 for outputting a second local oscillation frequency F _LO2, with the second local oscillation frequency F _LO2, the second RF band F _A second mixer 222 that converts _R2 into a second IF signal and a second IF bandpass filter 223 that extracts a second IF band _IF2 from the second IF signal are included.

The A / D converter 104 samples a baseband signal obtained by sampling the IF signal obtained by adding the first IF band F _IF1 and the second IF band F _IF2 at one sampling frequency Fs by undersampling. Output.

The processor unit 200 uses the first local oscillation frequency F _LO1 and the second local oscillation frequency F _LO2 calculated according to the desired signal in the system band based on the sampling frequency Fs, respectively, as the first local frequency oscillator and the first local frequency oscillator. Direct to 2 local frequency oscillators. Here, the processor unit 200 sets the first local oscillation frequency F _LO1 and the second local oscillation frequency F _LO2 to different values so that the baseband signals after undersampling do not overlap each other. That is, according to the present invention, in order to prevent the baseband signals after undersampling from overlapping each other, the local oscillation frequencies _FLO1 and _FLO2 are changed instead of changing the sampling frequency Fs.

  FIG. 4 is a transition diagram of the BB band in which system bands or desired signals do not overlap each other.

FIG. 4A is a transition diagram of the BB band that prevents the system bands from overlapping each other. The first BB band and the second BB band are represented in the baseband band obtained by undersampling. Here, in order for the two BB bands to be accommodated so as not to overlap each other, the following conditions must be satisfied.
F _BB1 -B _1/2> 0
_{F BB1 + B 1/2 <} F BB2 -B 2/2
_{F BB2 + B 2/2 <} Fs / 2
Or F _BB2 -B _2/2> 0
_{F BB2 + B 2/2 <} F BB1 -B 1/2
_{F BB1 + B 1/2 <} Fs / 2
F _BB1 : Center frequency of the first BB band F _BB2 : Center frequency of the second BB band Fs: Sampling frequency According to this condition value, the two system bands are accommodated between 0 and Fs / 2, and Two system bands do not overlap each other. Here, the center frequency F _BB1 of the first BB band that satisfies this condition value, the center frequency F _BB2 of the second BB band, and the sampling frequency Fs are arbitrarily selected.

4B to 4D are transition diagrams of the BB band in which desired signals are not overlapped with each other. FIG. 4B shows that the folded signal in the system band at the frequency Fs / 2 does not interfere with the desired signal. FIG. 4C shows that the system band loopback signal at frequency 0 does not interfere with the desired signal. FIG. 4D shows that the first system band does not interfere with the second desired signal.
_{Fs / 2- (F BBch1 + B} ch1 / 2)> (F BBch1 + B 1/2) -Fs / 2
_{(F BBch1 -B ch1 / 2)} > - (F BB1 -B 1/2)
_{Fs / 2- (F BBch2 + B} ch2 / 2)> (F BBch2 + B 2/2) -Fs / 2
_{(F BBch2 -B ch2 / 2)} > - (F BB2 -B 2/2)
_{| F BBch2 -F BB1 | <B} ch2 / 2 + B 1/2
_{| F BBch1 -F BB2 | <B} ch1 / 2 + B 2/2
F _BBch1 : Center frequency of the first BB desired signal F _BBch2 : Center frequency of the second BB desired signal Fs: Sampling frequency Center frequency F _BB1 of the first BB band satisfying these condition values, second BB band The center frequency _FBB2 and the sampling frequency Fs are arbitrarily selected.

  FIG. 5 is a transition diagram of frequency components in the present invention.

According to FIG. 5A, the first RF band and the desired signal and the second RF band and the desired signal are represented in the high frequency band. Here, as an initial value, the center frequency and bandwidth for each desired signal are defined as follows.
[default value]
F _R1 : Center frequency of the first RF band B ₁ : Bandwidth of the first RF band F _R2 : Center frequency of the second RF band B ₂ : Bandwidth of the second RF band

Next, according to FIG. 5A, the following relationship is established between the first local oscillation frequency F _LO1 and the second local oscillation frequency F _LO2 by the above-described initial value and the condition value of FIG. To do.
F _IF1 = | F _R1 -F _LO1 |
F _R1 −F _LO1 = ± F _IF1
F _LO1 = F _R1 ± F _IF1
= F _R1 ± {(N ₁ +1) / 2 × Fs−F _BB1 } (N ₁ mod 2 ≠ 0)
_{F R1 ± {N 1/2} × Fs + F BB1} (N 1 mod 2 = 0)
F _IF2 = | F _R2 -F _LO2 |
F _R2 −F _LO2 = ± F _IF2
F _LO2 = F _R2 ± F _IF2
= F _R2 ± {(N ₂ +1) / 2 × Fs−F _BB2 } (N ₂ mod 2 ≠ 0)
_{F R2 ± {N 2/2} × Fs + F BB2} (N 2 mod 2 = 0)
F _IF1 : Center frequency of the first IF band F _IF2 : Center frequency of the second IF band

Finally, undersampling is performed on the IF band all at once. The IF band signal is folded a plurality of times by undersampling and frequency-converted to a baseband band signal. Here, the under-sampling, defines a folded number N ₁ of the first desired signal and a folding number N ₂ of the second desired signal.

Here, when the IF band is folded an odd number of times and converted into a desired signal in the baseband band, F _IF1 is calculated by the following equation.
F _IF1 = (N ₁ +1) / 2 × Fs−F _BB1 (N ₁ mod 2 ≠ 0)
Further, when the IF band is folded even times and converted into a desired signal in the baseband band, F _IF1 is calculated by the following equation.
_{F IF1 = N 1/2 ×} Fs + F BB1 (N 1 mod 2 = 0)

For F _IF2 , F _BB2, and N ₂ , the same relationship as the above two formulas is established.
F _IF2 = (N ₂ +1) / 2 × Fs−F _BB2 (N ₂ mod 2 ≠ 0)
_{F IF2 = N 2/2 ×} Fs + F BB2 (N 2 mod 2 = 0)

The local oscillation frequencies F _LO1 and F _LO2 define the first BB band or desired signal folding number N _{1 in} undersampling and the second BB band or desired signal folding number N ₂ according to the above-described equation. Or by controlling the local oscillation frequency of the local frequency oscillator.
F _L01 = F _R1 ± {(N ₁ +1) / 2 × Fs−F _BB1 } (N ₁ mod 2 ≠ 0)
_{F R1 ± {N 1/2} × Fs + F BB1} (N 1 mod 2 = 0)
F _L02 = F _R2 ± {(N ₂ +1) / 2 × Fs−F _BB1 } (N ₂ mod 2 ≠ 0)
_{F R2 ± {N 2/2} × Fs + F BB2} (N 2 mod 2 = 0)

According to these equations, F _LO1 and F _LO2 are uniquely calculated by setting F _R1 , F _R2 , F _BB1 , F _BB2 , Fs, N ₁ , and N ₂ . The F _LO1 and F _LO2 can be converted into a baseband signal so that a plurality of desired signals in the RF band do not overlap each other.

According to FIG. 5B, the first RF band and the desired signal, and the second RF band and the desired signal are represented in the high frequency band. Here, as an initial value, the center frequency and bandwidth for each desired signal are defined as follows.
[default value]
F _R1 : Center frequency of the first RF band B ₁ : Bandwidth of the first RF band F _R2 : Center frequency of the second RF band B ₂ : Bandwidth of the second RF band F _Rch1 : First Center frequency of RF desired signal B _ch1 : Bandwidth of first RF desired signal F _Rch2 : Center frequency of second RF desired signal B _ch2 : Bandwidth of second RF desired signal

Next, according to FIG. 5B, the following relationship is established between the first local oscillation frequency F _LO1 and the second local oscillation frequency F _LO2 by the above-described initial value and the condition value of FIG. To do.
F _IF1 = | F _R1 −F _LO1 |
F _IF2 = | F _R2 -F _LO2 |
F _IF1 : Center frequency of the first IF band F _IF2 : Center frequency of the second IF band

Finally, undersampling is performed on the IF desired signal at once. Similar to the equation in FIG. 5A described above, the local oscillation frequencies F _LO1 and F _LO2 can be determined as follows.
F _L01 = F _R1 ± F _BB1 − (N ₁ +1) / 2 × Fs (N ₁ mod 2 ≠ 0)
_{F R1 ± F BB1 -N 1/} 2 × Fs (N 1 mod 2 = 0)
F _L02 = F _R2 ± F _BB2 − (N ₂ +1) / 2 × Fs (N ₂ mod 2 ≠ 0)
_{F R2 ± F BB2 -N 2/} 2 × Fs (N 2 mod 2 = 0)

According to the above formula, F _LO1 and F _LO2 are uniquely calculated by setting F _R1 , F _R2 , F _BB1 , F _BB2 , Fs, N ₁ , and N ₂ . The F _LO1 and F _LO2 can be converted into a baseband signal so that a plurality of RF desired signals do not overlap each other. In addition, since the direction of the spectrum can be controlled by the sign of “±” in the above equation, the arrangement of the spectrum can be freely controlled according to the position of the desired signal so that the desired signals do not overlap each other.

When the local oscillation frequency is controlled so that the desired channels do not overlap each other, the system center frequency (F _BB1 , F _BB2 , F _IF1 F _IF2 ) is used as a reference. Since the positional relationship between the center frequency of the system and the center frequency of the desired channel does not always change, if the center frequency of the system is determined, the center frequency of the desired channel is also automatically determined. Further, by using the center frequency of the system as a reference, it is possible to change the number of loopbacks and the sign of the local oscillation frequency and change the direction of the spectrum.

  FIG. 6 is a flowchart of the processor according to the present invention.

The center frequency F _R1 and bandwidth B ₁ of the desired signal in the first RF band and the center frequency F _R2 and bandwidth B ₂ of the desired signal in the second RF band are set as initial values. FIG. 6 shows only the processing steps in the embodiment of FIG.

(S601) For example, the center frequency F _BB1 of the desired signal in the first BB band, the center frequency F _BB2 of the desired signal in the second BB band, and the sampling frequency Fs that satisfy the condition values described above with reference to FIG. 4 are arbitrarily selected. .
F _BB1 -B _1/2> 0
_{F BB1 + B 1/2 <} F BB2 -B 2/2
_{F BB2 + B 2/2 <} Fs / 2
Or F _BB2 -B _2/2> 0
_{F BB2 + B 2/2 <} F BB1 -B 1/2
_{F BB1 + B 1/2 <} Fs / 2
(S602) By defining the number of times N ₁ of folding the desired signal in the first BB band and the number of times N ₂ of folding the desired signal in the second BB band in undersampling, for example, as described above with reference to FIG. First local oscillation frequency _FL01 and second local oscillation frequency _FL02 are calculated.
F _L01 = F _R1 ± {(N ₁ +1) / 2 × Fs−F _BB1 } (N ₁ mod 2 ≠ 0)
_{F R1 ± {N 1/2} × Fs + F BB1} (N 1 mod 2 = 0)
F _L02 = F _R2 ± {(N ₂ +1) / 2 × Fs−F _BB2 } (N ₂ mod 2 ≠ 0)
_{F R2 ± {N 2/2} × Fs + F BB2} (N 2 mod 2 = 0)
(S603) The first local oscillation frequency F _LO1 and the second local oscillation frequency F _LO2 are instructed to the first local frequency oscillator and the second local frequency oscillator, respectively.

  In addition, according to the above-described embodiment, the undersampling for two system bands or desired signals has been described. Of course, even if the number of bands or signals to be simultaneously sampled is three or more, by increasing the frequency conversion unit, of course. Applicable.

  As described above in detail, according to the receiver, the program, and the method of the present invention, the frequency band is converted into the IF band, and the IF band is undersampled. In addition to reducing the influence, it is easy to design a band pass filter for an IF band signal. Further, by controlling the local oscillation frequency at the time of frequency conversion to the IF band, it is possible to derive a low sampling frequency Fs in which a plurality of desired signals after undersampling do not overlap each other.

  Currently, CDMA2000 1x and CDMA2000 1xEV-DO are widely used as mobile communication systems. On the other hand, the spread of LTE (Long Term Evolution) and UMB (Ultra Mobile Broadband) as 3.9G wireless systems is expected in the future. By using the receiver of the present invention, it is possible to simultaneously execute, for example, the reception processing of the EV-DO and UMB wireless systems. Also, in the 4G wireless system, it is assumed that a transmission band having a maximum width of 100 MHz is used. However, it may be difficult to secure a continuous wide band depending on the frequency allocation state. In such a case, a system that realizes broadband communication by simultaneously using channels that are not used by the existing system in a plurality of bands assigned to the cellular system or the like can be considered. The receiver of the present invention can also be applied to this system.

  In the various embodiments of the present invention described above, various changes, modifications, and omissions in the scope of the technical idea and the viewpoint 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.

It is a functional block diagram of the receiver in a prior art. It is an image figure of the frequency component in the case of using undersampling. It is a functional block diagram of the receiver in this invention. It is a BB band transition diagram in which system bands or desired signals do not overlap. It is a transition figure of the frequency component in this invention. It is a flowchart of the processor in this invention.

Explanation of symbols

1 Receiver 100 Processor unit, CPU
101 antenna 102 band pass filter, BPF
103 Low noise amplifier, LNA
104 A / D converter 105 Sampling clock generator 111 Local frequency oscillator 112 Mixer 113 Low-pass filter 114 Band-pass filter 200 Processor unit, CPU
210 First frequency conversion unit 220 Second frequency conversion unit 211, 221 Local frequency oscillator 212, 222 Mixer 213, 223 Band pass filter

Claims (7)

A receiver having an antenna for receiving an RF (Radio Frequency) signal including two system bands,
A first RF band included in the RF signal is converted into a first IF (Intermediate Frequency) band F _IF1 by using a first local oscillation frequency F _LO1 output from a first local frequency oscillator. 1 frequency conversion means;
Second frequency conversion for converting the second RF band included in the RF signal into the second IF band F _IF2 by using the second local oscillation frequency F _LO2 output from the second local frequency oscillator. Means,
A / D conversion that outputs a BB (Base Band) signal obtained by sampling the IF signal obtained by adding the first IF band F _IF1 and the second IF band F _IF2 at one sampling frequency Fs by undersampling. And
Based on the sampling frequency Fs, the first local oscillation frequency F _LO1 and the second local oscillation frequency F _LO2 calculated so that the system bands or desired signals do not interfere with each other in the frequency domain are respectively set as the first local frequency. have a processor unit that instructs the oscillator and the second local frequency oscillator,
The processor means includes
The center frequency F _R1 and bandwidth B ₁ of the first RF band or desired signal and the center frequency F _R2 and bandwidth B _{2 of} the second RF band or desired signal are set as initial values, and the system bands or desired signals are set as initial values. The first BB band or the center frequency F _BB1 of the desired signal, the second BB band or the center frequency F _{BB2 of the} desired signal, and the sampling frequency Fs are arbitrarily selected so that they do not interfere with each other in the frequency domain ,
By controlling the first BB band or desired signal folding number N ₁ and the second BB band or desired signal folding number N _{2 in} undersampling , or controlling the local oscillation frequency of the local frequency oscillator By,
F _L01 = F _R1 ± {(N ₁ +1) / 2 × Fs−F _BB1 } (N ₁ mod 2 ≠ 0)
_{F R1 ± {N 1/2} × Fs + F BB1} (N 1 mod 2 = 0)
F _L02 = F _R2 ± {(N ₂ +1) / 2 × Fs−F _BB2 } (N ₂ mod 2 ≠ 0)
_{F R2 ± {N 2/2} × Fs + F BB2} (N 2 mod 2 = 0)
The first local oscillation frequency _FL01 and the second local oscillation frequency _FL02 are calculated by the following . The processor means includes
The center frequency F _R1 and bandwidth B ₁ of the first RF band and the center frequency F _R2 and bandwidth B _{2 of} the second RF band are set as initial values,
F _BB1 -B _1/2> 0
_{F BB1 + B 1/2 <} F BB2 -B 2/2
_{F BB2 + B 2/2 <} Fs / 2
Or F _BB2 -B _2/2> 0
_{F BB2 + B 2/2 <} F BB1 -B 1/2
_{F BB1 + B 1/2 <} Fs / 2
2. The receiver according to claim 1 , wherein the center frequency F _BB1 of the first BB band, the center frequency F _BB2 of the second BB band, and the sampling frequency Fs that satisfy the condition value are arbitrarily selected. The processor means includes
The center frequency F _Rch1 and bandwidth B _ch1 of the first RF desired signal and the center frequency F _Rch2 and bandwidth B _{ch2 of} the second RF desired signal are set as initial values.
_{Fs / 2- (F BBch1 + B} ch1 / 2)> (F BBch1 + B 1/2) -Fs / 2
_{(F BBch1 -B ch1 / 2)} > - (F BB1 -B 1/2)
_{Fs / 2- (F BBch2 + B} ch2 / 2)> (F BBch2 + B 2/2) -Fs / 2
_{(F BBch2 -B ch2 / 2)} > - (F BB2 -B 2/2)
_{| F BBch2 -F BB1 | <B} ch2 / 2 + B 1/2
_{| F BBch1 -F BB2 | <B} ch1 / 2 + B 2/2
2. The receiver according to claim 1 , wherein the center frequency F _BB1 of the first BB band, the center frequency F _BB2 of the second BB band, and the sampling frequency Fs that satisfy the condition value are arbitrarily selected. The processor means is _{arranged such} that the frequency interval between the center frequency F _IF1 of the desired signal in the first IF band and the center frequency F _IF2 of the desired signal in the second IF band is the center of the desired signal in the first RF band. receiving according to any one of claims 1 to 3, characterized in that selected to be smaller than the frequency interval between the frequency F _R1 and the center frequency F _R2 of the second RF band of the desired signal Machine. The first frequency conversion means is
A first RF band pass filter for extracting a first RF band F _R1 included in the RF signal;
A first mixer for converting the first RF band F _R1 into a first IF signal using the first local oscillation frequency F _LO1 output from the first local frequency oscillator;
A first IF band pass filter for extracting a first IF band F _IF1 from the first IF signal;
The second frequency conversion means is
A second RF band pass filter for extracting a second RF band F _R2 included in the RF signal;
A second mixer for converting the second RF band F _R2 into a second IF signal using the second local oscillation frequency F _LO2 output from the second local frequency oscillator;
From the second IF signal receiver according to claim 1, any one of 4, characterized in that it comprises a second IF band-pass filter for extracting a second IF band _IF2. An antenna for receiving an RF signal including two system bands;
A first frequency conversion for converting a first RF band included in the RF signal into a first IF band F _IF1 using a first local oscillation frequency F _LO1 output from a first local frequency oscillator. Means,
Second frequency conversion for converting the second RF band included in the RF signal into the second IF band F _IF2 by using the second local oscillation frequency F _LO2 output from the second local frequency oscillator. Means,
An A / D converter that outputs a BB signal obtained by sampling the IF signal obtained by adding the first IF band F _IF1 and the second IF band F _IF2 at one sampling frequency Fs by undersampling; A program for causing a computer installed in a receiver to function,
A first step in which the center frequency F _R1 and bandwidth B ₁ of the first RF band or desired signal and the center frequency F _R2 and bandwidth B _{2 of} the second RF band or desired signal are initial values;
The first BB band or the center frequency F _BB1 of the desired signal, the second BB band or the center frequency F _{BB2 of the} desired signal, and the sampling frequency Fs are arbitrarily set so that the system bands or the desired signals do not interfere with each other in the frequency domain. A second step of selecting;
By controlling the first BB band or desired signal folding number N ₁ and the second BB band or desired signal folding number N _{2 in} undersampling, or controlling the local oscillation frequency of the local frequency oscillator By,
F _L01 = F _R1 ± {(N ₁ +1) / 2 × Fs−F _BB1 } (N ₁ mod 2 ≠ 0)
_{F R1 ± {N 1/2} × Fs + F BB1} (N 1 mod 2 = 0)
F _L02 = F _R2 ± {(N ₂ +1) / 2 × Fs−F _BB2 } (N ₂ mod 2 ≠ 0)
_{F R2 ± {N 2/2} × Fs + F BB2} (N 2 mod 2 = 0)
To calculate the first local oscillation frequency F _L01 and the second local oscillation frequency F _L02 , and the first local oscillation frequency F _LO1 and the second local oscillation frequency F _LO2 , respectively. A program for a receiver, which causes a computer to be executed as a fourth step for instructing a frequency oscillator and a second local frequency oscillator. An antenna for receiving an RF signal including two system bands;
A first frequency conversion for converting a first RF band included in the RF signal into a first IF band F _IF1 using a first local oscillation frequency F _LO1 output from a first local frequency oscillator. Means,
Second frequency conversion for converting the second RF band included in the RF signal into the second IF band F _IF2 by using the second local oscillation frequency F _LO2 output from the second local frequency oscillator. Means,
An A / D converter that outputs a BB signal obtained by sampling the IF signal obtained by adding the first IF band F _IF1 and the second IF band F _IF2 at one sampling frequency Fs by undersampling; An undersampling method in a receiver,
A first step in which the center frequency F _R1 and bandwidth B ₁ of the first RF band or desired signal and the center frequency F _R2 and bandwidth B _{2 of} the second RF band or desired signal are initial values;
The first BB band or the center frequency F _BB1 of the desired signal, the second BB band or the center frequency F _{BB2 of the} desired signal, and the sampling frequency Fs are arbitrarily set so that the system bands or the desired signals do not interfere with each other in the frequency domain. A second step of selecting;
By controlling the first BB band or desired signal folding number N ₁ and the second BB band or desired signal folding number N _{2 in} undersampling, or controlling the local oscillation frequency of the local frequency oscillator By,
F _L01 = F _R1 ± {(N ₁ +1) / 2 × Fs−F _BB1 } (N ₁ mod 2 ≠ 0)
_{F R1 ± {N 1/2} × Fs + F BB1} (N 1 mod 2 = 0)
F _L02 = F _R2 ± {(N ₂ +1) / 2 × Fs−F _BB2 } (N ₂ mod 2 ≠ 0)
_{F R2 ± {N 2/2} × Fs + F BB2} (N 2 mod 2 = 0)
To calculate the first local oscillation frequency F _L01 and the second local oscillation frequency F _L02 , and the first local oscillation frequency F _LO1 and the second local oscillation frequency F _LO2 , respectively. And a fourth step of instructing the frequency oscillator and the second local frequency oscillator.

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