JP2001274714A - Software receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a receiver that applies reception processing to wireless signals in wireless frequency bands, at the same time that uses a single local oscillation frequency for simplifying the structure. SOLUTION: IN the receiver applying reception processing to each wave of 60 MHz and 150 MHz bands at the same time, frequency mixers 409, 414 of reception sections 101, 102 simultaneously use an oscillated frequency from a local oscillator 408. An adder 403 sums both outputs via band pass filters 410, 103 respectively, an analog/digital converter 404 samples the sum, and a digital processing means 405 separates the sampled signal into demodulation signals A, B. When applying analog/digital conversion to the input signal, a relation between the local oscillation frequency and the sampling frequency is selected and set, so that the frequency spectra of each digital signal that is generated do not mutually overlap.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a software receiver for simultaneously receiving and processing a plurality of radio signals in a plurality of radio frequency bands.

2. Description of the Related Art In recent years, a software receiver has been proposed as a powerful means for receiving a plurality of radio signals in a radio wave format having different frequency bands, modulation methods, and bandwidths with a single receiver. This means that a radio signal received by a receiver is once digitized by an A / D converter, and the digitized signal is converted to a DS signal.
Processing such as filtering and demodulation is performed collectively using digital processing means such as P. By doing so, it is possible to receive and process various types of radio signals by changing programs (software) incorporated in digital processing means such as a DSP, so that high functions and multiple functions can be achieved. It is well known that various types of software receivers have been studied and proposed as being responsible for next-generation receivers.

FIG. 4 is a block diagram showing an example of the configuration of a conventional software receiver. The software receiver shown in FIG. 4 is a receiver for simultaneously receiving and processing radio signals in two reception bands of a 60 MHz band and a 150 MHz band, and converts a radio signal of a predetermined band of a 60 MHz band into a predetermined intermediate frequency. Receiver 401 for outputting, 150 MH
a receiving unit 402 for converting a radio signal of a predetermined band of the z band into a predetermined intermediate frequency; an output of the receiving unit 401 and the receiving unit 40
And an A / D converter 404 for converting a combined output from the adder 403 into a digital signal.
And a digital processing means 405 for processing and demodulating the digital signal from the A / D converter 404.

The receiving section 401 includes an antenna 406 for receiving a radio signal of a predetermined band of a 60 MHz band, a band-pass filter 407 for selecting only a predetermined band from the high-frequency signals received and output by the antenna 406, and a fixed frequency of 20 MHz.
a local oscillator 408 oscillating and outputting a local oscillation signal of z, a high-frequency signal from the band-pass filter 407 and the local oscillator 4
A frequency mixer 409 for mixing the local oscillation signal from the converter 08 into a 40 MHz band intermediate frequency signal, and a band pass filter 410 for selecting only a predetermined band of the 40 MHz band intermediate frequency signal from the frequency mixer 409. ing. Further, the receiving unit 402 is provided with an antenna 411 for receiving a radio signal of a predetermined band of 150 MHz band, and a band-pass filter for selecting only a predetermined band among high-frequency signals received and output by the antenna 411.
412, a local oscillator 413 that oscillates and outputs a local signal of a fixed frequency of 100 MHz, and a high frequency signal from the band-pass filter 412 and a local signal from the local oscillator 413 are mixed and converted into a 50 MHz band intermediate frequency signal. Frequency mixer
414, and a band-pass filter 410 for selecting only a predetermined band of the 50 MHz intermediate frequency signal from the frequency mixer 414.
And

FIG. 5 is a diagram showing the frequency spectrum of signals input to and output from each component block in the conventional embodiment shown in FIG. 4. In FIG.
(2) and (3) show the antenna 406 and the antenna 411, respectively.
And the frequency spectrum of the radio signal received by
The frequency spectrum of the input signal of the D converter and the A /
The frequency spectrum after frequency sampling by the D converter 404 is shown.

The operation of the conventional example shown in the figure will be described below. First, the antenna 406 has a size of 60 to 60 shown in FIG.
The radio signal A having a frequency band of 70 MHz (corresponding to the spectrum of A) is received, and the antenna 411 receives the radio signal B having a frequency band of 150 to 160 MHz (corresponding to the spectrum of B) shown in FIG. I do. After the radio signal A from the antenna 406 passes through the bandpass filter 407, the local signal of the local oscillator 408 (oscillation frequency 2)
0 MHz), passes through the band-pass filter 410, is converted into an intermediate frequency signal A 'of 40 to 50 MHz and input to the adder 410. Similarly, the radio signal B from the antenna 411 passes through the band-pass
At 14 the local oscillator signal of the local oscillator 413 (oscillation frequency 100 MH
50) when mixed with z) and passed through bandpass filter 415.
Is converted into an intermediate frequency signal B 'of .about.
Entered as 0. The adder 403 outputs the intermediate frequency signal A '.
And the intermediate frequency signal B ', the intermediate frequency multiplexed signal having the frequency spectrum shown in FIG.
Output to

When the A / D converter 404 samples the intermediate frequency multiplexed signal at a predetermined sampling clock (here, the sampling frequency fs = 40 MHz), the A / D converter 404 outputs the intermediate frequency signal A as shown in FIG. ′,
A frequency spectrum obtained by repeating a frequency spectrum having exactly the same shape as the frequency spectrum of B 'is obtained. This is because the intermediate frequency signals A 'and B', which are the frequency components of the intermediate frequency multiplexed signal, are sampled (multiplied) by a sampling clock of 40 MHz, and the frequency component of the sampling clock is an integral multiple of fs = 40 MHz. The intermediate frequency signals A 'and B' are multiplied, respectively. If the frequencies of the intermediate frequency signals A 'and B' are fA and fB, respectively, | fA ± nfs | and | fB ± nfs
| (N = 0, 1, 2, 3,...) Is obtained. Therefore, | fA ± nfs
.. Corresponding to n = 0, 1, 2,... Of fA, fA-fs, fA-2fs, fA-3fs,. Each frequency component and each frequency component of fA + fs, fA + 2fs, fA + 3fs,... Are obtained. Similarly, in correspondence with | fB ± nfs |, each frequency component of fB, fB-fs, fB-2fs, fB-3fs,.
Each frequency component of fB + fs, fB + 2fs, fB + 3fs,... is obtained.

Therefore, the A / D converter 404 is arranged as shown in FIG.
A digital signal corresponding to the frequency spectrum shown in (3) is sent to the digital processing means 405. The digital processing means 405 processes the digital signal and generates a frequency component in a band of 0 to 10 MHz in FIG.
And demodulated signals A and B are output. Here, the demodulated signals A and B are demodulated signals corresponding to the radio signals A and B, respectively.

[0008]

However, the conventional software receiver as described above has the following problems. That is, in a conventional software receiver, two radio signals A and B are converted into intermediate frequency signals A 'and B', respectively, and can be sampled by an A / D converter. As shown, the frequencies of the intermediate frequency signals A 'and B' are 40 to 50, respectively.
MHz and 50 to 60 MHz. For this reason, it is necessary to convert the two radio signals A and B in different radio frequency bands into adjacent intermediate frequencies of substantially the same frequency, and the oscillation frequency is 20 MHz.
And two local oscillators having different frequencies of 100 MHz. In addition, high frequency 100M
Hz local oscillators are more expensive than 20 MHz local oscillators, which has been a problem in reducing costs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and requires only one local oscillator. Therefore, a software receiving apparatus capable of reducing the mounting space and reducing the cost is provided. The purpose is to provide a machine.

[0010]

In order to solve the above-mentioned object, a software receiver according to the present invention according to claim 1 of the present invention receives radio signals in a plurality of radio frequency bands, and transmits the radio signals in the same manner. Synthesizing means for synthesizing the intermediate frequency radio signal with the local transmission frequency of the above, an A / D converter for converting the output of the synthesizing means into a digital signal, and digital processing means for processing the digital signal and outputting a demodulated signal. A software receiver comprising: the local oscillation frequency and the sampling frequency of an A / D converter so that the frequency spectrum of each digital signal does not overlap each other when the intermediate frequency radio signal is converted into a digital signal. Is set to a predetermined value. The invention according to claim 2 of the software receiver according to the present invention sets the local oscillation frequency to a frequency value closest to a radio frequency band exhibiting a lowest frequency among the plurality of radio frequency bands. The sampling frequency of the / D converter is kept low.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on illustrated embodiments. FIG. 1 is a block diagram showing an embodiment of a software receiver according to the present invention.
The software receiver shown in this example has 60 MHz band and 15 MHz band.
A receiver for simultaneously receiving and processing radio signals in two reception bands of a 0 MHz band, and converting a radio signal of a predetermined band of a 60 MHz band into a predetermined intermediate frequency and outputting the converted signal.
A receiving unit 102 for converting a radio signal in a predetermined band of a 150 MHz band into a predetermined intermediate frequency;
A local oscillator 408 that oscillates and outputs a local oscillation signal of the same, and an adder that combines the output of the receiver 101 and the output of the receiver 102
403, an A / D converter 404 for converting a combined output from the adder 403 into a digital signal, and a digital processing means 405 for processing and demodulating the digital signal from the A / D converter 404.
And

The receiving section 401 includes an antenna 406 for receiving a radio signal in a predetermined band of a 60 MHz band, a band-pass filter 407 for selecting only a predetermined band from high-frequency signals received and output by the antenna 406, A frequency mixer 409 for mixing a high-frequency signal from the filter 407 and a local signal from the local oscillator 408 and converting the mixed signal into an intermediate frequency signal in a 40 MHz band;
a band-pass filter 410 for selecting only a predetermined band of the z-band intermediate frequency signal. Further, the receiving unit 402
Antenna 41 for receiving a radio signal of a predetermined band of 0 MHz band
1, a band-pass filter 412 that selects only a predetermined band from high-frequency signals received and output by the antenna 411, a high-frequency signal from the band-pass filter 412, and the local oscillator 4.
A frequency mixer 414 for mixing the local oscillation signal from the second mixer 08 and converting it into an intermediate frequency signal of a 130 MHz band;
And a band-pass filter 103 for selecting only a predetermined band from the intermediate frequency signal in the 130 MHz band.

FIG. 2 shows a frequency spectrum of a signal input / output to / from each block in the embodiment shown in FIG. 1. FIG. 2 shows a frequency spectrum of a radio signal received by the antennas 406 and 411. 2 shows a frequency spectrum of an input signal of the A / D converter and a frequency spectrum after frequency sampling by the A / D converter 404.

The software receiver shown in this example operates as follows. First, the antenna 406 is connected to the antenna 6 shown in FIG.
Radio signal A having a frequency band of 0 to 70 MHz (corresponding to the spectrum of A) is received,
The radio signal B (corresponding to the spectrum of B) having the frequency band of 150 to 160 MHz shown in (1) is received. The radio signal A from the antenna 406 passes through a bandpass filter 407 and is mixed with a local oscillation signal (oscillation frequency: 20 MHz) of a local oscillator 408 by a frequency mixer 409 and an intermediate frequency signal of 40 to 50 MHz when passing through a bandpass filter 410 It is converted to A 'and input to the adder 410. Similarly, the antenna 411
After passing through the band-pass filter 412, the radio signal B from the local oscillator 408 (oscillation frequency 2)
0 MHz), passes through the band-pass filter 103, is converted into an intermediate frequency signal B 'of 130 to 140 MHz and input to the adder 410. When the adder 403 adds the intermediate frequency signal A 'and the intermediate frequency signal B', FIG.
The intermediate frequency multiplexed signal of the frequency spectrum shown in A / D
Output to converter 404.

When the A / D converter 404 samples the intermediate frequency multiplexed signal with a predetermined sampling clock (here, sampling frequency fs = 40 MHz), the A / D converter 404 performs the same operation as in the example shown in FIG. As shown in (3), a spectrum obtained by repeating a spectrum having exactly the same shape as the spectrum of the intermediate frequency signals A 'and B' is obtained. This is because when the intermediate frequency signals A 'and B', which are the frequency components of the intermediate frequency multiplexed signal, are sampled (multiplied) by a sampling clock of 40 MHz, similarly to the above-described conventional embodiment, the intermediate frequency signals A 'and A' are sampled.
If the frequencies of B 'are fA and fB, respectively, | fA ± nf
s | and | fB ± nfs | (n = 0, 1, 2, 3,...
..) Are obtained. Therefore,
.. Corresponding to n = 0, 1, 2,... Of | fA ± nfs |, as shown in FIG. 1 (3), fA, fA-fs, fA-2fs, fA-3fs,.
・ ・ ・ ・ ・ Frequency components and fA + fs, fA + 2fs, fA + 3fs, ・ ・ ・ ・ ・ ・ ・ ・ ・ ・
Are obtained. Similarly, | fB ± nf
In response to s |, each frequency component of fB, fB-fs, fB-2fs, fB-3fs,..., and fB + fs, fB + 2fs, fB + 3fs,. .. Are obtained.

Here, it should be noted that the frequency spectrum after sampling shown in FIG. 2 (3) is exactly the same as that in FIG. 5 (3). Regarding the intermediate frequency signal B ', although the frequency fB is different between the conventional example and the present invention, as a result of sampling, the frequency spectrum is completely the same. This is because the frequency fB of the intermediate frequency signal B 'and the sampling frequency fs
Is optimized so as to satisfy the numerical relationship described below. That is, assuming that the frequency which is an integral multiple of the sampling frequency fs and does not exceed the frequency fB of the intermediate signal and which is closest is mfs, fB-mf
If s has the same value, the spectrum after sampling has the same shape. For example, for the conventional example, fB = 5
0-60MHz, mfs = 1 * 40MHz = 40MH
z, fB-mfs = 50-60 MHz-40 MHz = 1
0 to 20 MHz, and fB =
130-140MHz, mfs = 3 * 40MHz = 12
0 MHz, fB-mfs = 130 to 140 MHz-12
0 MHz = 10 to 20 MHz, and both the conventional example and the present invention match at fB-mfs = 10 to 20 MHz. If fB-mFs = 10-20 MHz is satisfied, fB other than the above (for example, 10-20 MHz, 90-10
0 MHz, 170-180 MHz, etc.).

Further, similarly to the above-mentioned conventional example, the A /
The D converter 404 sends a digital signal corresponding to the frequency spectrum shown in FIG. The digital processing means 405 processes the digital signal, separates and demodulates the frequency components of the band of 0 to 10 MHz and the frequency components of the band of 10 to 20 MHz in FIG. 1 (3), and outputs a demodulated signal A and a demodulated signal B. . Here, the demodulated signals A and B are demodulated signals corresponding to the radio signals A and B, respectively.

As described above, in a software receiver having two receiving units, conventionally, the receiving units are individually provided with local oscillators so that the output frequencies of the receiving units are substantially the same. In the present invention, since only one local oscillator is provided in the present invention, the hardware configuration can be simplified, and the size and cost can be reduced.

In the embodiment of the present invention described above,
Although the frequency of the local oscillator is set to 20 MHz, the present invention is not limited to this. For example, the frequency of the local oscillator may be set to 60 MHz. In this case, as shown in FIG. The frequency of the intermediate frequency signal B is 0 to 10 MHz and 90 to 100 MHz, respectively. When these are sampled by the A / D converter, the frequency spectrum after sampling is as shown in FIG.
The same spectrum as in FIG. 2 (3) can be obtained.
Therefore, the frequency of the local oscillator is increased from 20 MHz to 60 MHz.
By making z, the frequency input to the A / D converter can be lowered, so that an inexpensive A / D converter having a frequency characteristic of 100 MH or less can be used, so that the cost can be further reduced. Becomes possible.

[0020]

As described above, according to the present invention, in a software receiver having two receivers capable of simultaneously receiving two different radio frequency band radio signals, a radio signal received by the two receivers is transmitted. Instead of requiring two local oscillators to convert to an intermediate frequency signal, a configuration with only one local oscillator has been adopted.This makes it possible to simplify the hardware configuration and reduce the size and cost. The effect is great.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a software receiver according to the present invention.

FIG. 2 is a frequency spectrum diagram at the input and output of each block of the software receiver according to the present invention.

FIG. 3 is a frequency spectrum diagram of input and output of each block in a modified example of the software receiver according to the present invention.

FIG. 4 is a block diagram showing an embodiment of a conventional software receiver.

FIG. 5 is a frequency spectrum diagram at the input and output of each block of a conventional software receiver.

[Explanation of symbols]

 101, 102, 401, 402 ... receiving units 103, 407, 410, 412 ... band-pass filters 403 ... adders 404 ... A / D converters 405 ... digital processing means 406, 411 ... Antenna 408, 413 ... Local oscillator

Claims (2)

[Claims] 1. A synthesizing means for receiving radio signals in a plurality of radio frequency bands and synthesizing the radio signals with an intermediate frequency radio signal using the same local oscillation frequency, and converting an output of the synthesizing means into a digital signal. A software receiver comprising an A / D converter and digital processing means for processing the digital signal and outputting a demodulated signal, wherein each of the digital signals is converted when the intermediate frequency radio signal is converted to a digital signal. A software receiver, wherein the local oscillation frequency and the sampling frequency of the A / D converter are set to predetermined values so that frequency spectra do not overlap each other. 2. The sampling frequency of an A / D converter is kept low by setting the local oscillation frequency to a frequency value closest to a radio frequency band exhibiting the lowest frequency among the plurality of radio frequency bands. The software receiver according to claim 1, wherein: