JPH10107688A - Spread spectrum communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the spread spectrum communication equipment by which a level of a spread signal subject to spread spectrum processing by a received spread code is easily obtained thereby eliminating a narrow band disturbing wave with a higher level than that of the spread signal and included in the spread signal. SOLUTION: Part of a received spread signal is extracted by a distributer 6, and spread again by a mixer 7 by using a spread code different from that is used to spread the spread signal generated by a spread code generator 8 and received by the mixer 7, a level of the spread signal again is detected by a band pass filter 9 and a detector 10, the level is used for a level of the spread signal and an amplification factor variable amplifier 11 and a magnetostatic wave filter 12 eliminate a narrow band disturbing wave whose level is higher than a level of the spread signal. Thus, the level of the spread signal is obtained by using the single band pass filter and the detector without taking a frequency of the narrow band disturbing wave into account and then the narrow band disturbing wave whose level is higher than that of the spread signal and included in the spread signal is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum communication apparatus, and more particularly to a spread spectrum communication apparatus suitable for removing narrow band interference waves at the time of reception.

[0002]

2. Description of the Related Art FIG. 6 shows an example of a level detection circuit of a spread signal which is spread by a spread code and is a part of a narrow band interference wave removing means in a conventional spread spectrum communication apparatus. 6, the level detection circuit 100 includes three band-pass filters 101, 102, and 103, a level comparison circuit 104, a changeover switch 105, and a detector 10
6, an input terminal 107 and an output terminal 108. The changeover switch 105 has a control terminal 105a. The input sides of the three band-pass filters 101, 102 and 103 are combined into one and connected to the input terminal 107, and the output sides are respectively divided into two and connected to the level comparison circuit 104 and the changeover switch 105, respectively. . The output of the level comparison circuit 104 is a switch 1
The output of the changeover switch 105 is connected to the output terminal 108 via the detector 106.

FIG. 7 shows the relationship between the spectrum of a spread signal and three band-pass filters 101, 102 and 103.
In FIG. 7, 100s represents the spread signal, 101w, 10
2w and 103w each have three bandpass filters 10
1, 102, and 103 are shown. As shown in FIG. 7, the passbands 101w, 102w, and 103w of the three bandpass filters 101, 102, and 103 are set near the center of the frequency band of the spread signal so as not to overlap with each other.

In FIG. 6, a spread signal input from an input terminal 107 is divided into three and input to three band-pass filters 101, 102 and 103. Since the spread signal is distributed almost uniformly in the frequency band,
As shown in FIG. 7, each band-pass filter 101, 10
The spread signals passing through 2, 103 have almost the same level. However, when a narrow band interfering wave is added to the spread signal, the output of the band pass filter that includes the frequency of the narrow band interfering wave in the pass band becomes higher than the output of the other band pass filters. Therefore, the outputs of the three band-pass filters 101, 102 and 103 are compared with the level comparison circuit 104.
The changeover switch 105 is controlled so as to pass the signal in the pass band in which the signal with the lowest level is detected. The changeover switch 105 is connected to the level comparison circuit 10
According to the control of 4, three band-pass filters 101,
The signal having the lowest level among the signals passed through 102 and 103 is passed as the level of the spread signal, and the detector 106
To enter. The detector 106 detects the level of the input signal and outputs it to the output terminal 108. In this way, the level of the spread signal is detected, and based on the detected level, a narrow band interference wave having a higher level than the spread signal is removed.

In the level detection circuit of FIG. 6, three bandpass filters are used. However, as the number of bandpass filters is increased and the passband is narrowed, the accuracy of detecting the level of the spread signal is increased.

[0006]

However, in the above-described level detection circuit, a large number of band-pass filters are required to detect the level of the spread signal, and a circuit for comparing the levels is required. It was complicated.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and it is possible to obtain the level of a spread signal with a simple circuit and to remove narrow-band interference waves having a higher level than the spread signal. A spread spectrum communication device is provided.

[0008]

In order to achieve the above object, a spread spectrum communication apparatus according to the present invention comprises a signal receiving means for receiving a spread signal which has been spread by a spread code, and a narrow band included in the spread signal. In a spread spectrum communication apparatus having at least a narrow-band interference wave removing circuit for removing an interference wave, the narrow-band interference wave removing circuit includes a part of the spread signal, the spread signal being different from the spread code obtained by spreading the spread signal. A re-spreading circuit for re-spreading with a code, a level detecting circuit for detecting the level of the re-spread spread signal, and a level higher on the frequency axis than the spread signal included in the spread signal according to the level detect circuit. It is characterized by comprising a narrow band interference wave limiting circuit for limiting the level of the narrow band interference wave.

Further, in the spread spectrum communication apparatus according to the present invention, the narrow band interference wave limiting circuit includes an amplification factor variable amplifier for changing an amplification factor according to the level detection circuit.
It is characterized by comprising a magnetostatic wave filter which operates as a limiter for limiting a level on a frequency axis.

Further, in the spread spectrum communication apparatus according to the present invention, the narrow band interference wave limiting circuit includes a frequency / time conversion circuit for converting a spectrum of the spread signal into a time signal, and the frequency / time converted spread signal. An amplitude limiting circuit for limiting the amplitude of the spread signal on the time axis in accordance with the level detection circuit, and a time / frequency converting circuit for returning the spread signal subjected to the frequency / time conversion and the amplitude limitation to a spectrum. .

[0011]

FIG. 1 shows an embodiment of a spread spectrum communication apparatus according to the present invention. In FIG. 1, a spread spectrum communication apparatus 1 includes an antenna 2 serving as a signal receiving unit for receiving a spread signal that is spread by a spread code.
Band-pass filter 3, amplifier 4, narrow-band interference wave removing circuit 5, local oscillator 13, mixer 14, band-pass filter 15, amplifier 16, matched filter 17, amplifier 1
8, low-pass filter 19, demodulator 20, output terminal 21
It consists of. The narrow-band interference wave removing circuit 5 includes a distributor 6, a mixer 7, a spread code generator 8, a band-pass filter 9, a detector 10, a variable amplification factor amplifier 11, and a magnetostatic wave filter 12.

The antenna 2 is connected to a narrow band interference wave removing circuit 5 via a band pass filter 3 and an amplifier 4 in this order.
The output of the narrow-band interference wave removing circuit 5 is connected to a mixer 14, and the local oscillator 13 is also connected to the mixer 14. The output of the mixer 14 is connected to an output terminal 21 via a band-pass filter 15, an amplifier 16, a matched filter 17, an amplifier 18, a low-pass filter 19, and a demodulator 20 in that order.

In the narrow band interference wave removing circuit 5,
The input side is connected to the distributor 6, and two outputs of the distributor 6 are connected to the mixer 7 and the variable gain amplifier 11. A spreading code generator 8 is also connected to the mixer 7. The output of the mixer 7 is connected to a variable gain amplifier 11 via a band pass filter 9 and a detector 10. The output of the variable gain amplifier 11 is connected to the output side via a magnetostatic wave filter 12.

In the spread spectrum communication apparatus 1 configured as described above, unnecessary signals are removed from the signal received by the antenna 2 by the band pass filter 3, amplified by the amplifier 4, and the narrow band interference wave removing circuit 5 is provided. Is input to

The signal input to the narrow band interference wave removing circuit 5 is divided into two by a distributor 6, one of which is input to a mixer 7, and the other is input to a variable gain amplifier 11. The spread code generator 8 generates a spread code different from the spread code obtained by spreading the received spread signal or a spread code having a different chip rate. The spread signal input to the mixer 7 is re-spread by a different spread code from the spread code generator 8.

FIG. 2 shows the spectra of the signal input to the mixer 7 and the signal output from the mixer 7. FIG.
(A) is a spectrum of a signal input to the mixer 7 and shows a state in which the narrow band interference wave b1 is included in the frequency band of the spread signal a1. FIG. 2B shows the spectrum of the signal output from the mixer 7. The spread signal a1 is further spread to become a spread signal a2, and at the same time, the narrow band interference wave b
1 is also spread to become a narrow band interference wave b2, and a spread signal a2
Are superimposed entirely. Here, since the level of the spread signal a2 is a signal in which the original spread signal a1 has already been spread, there is no great difference from the level of the spread signal a1. On the other hand, the narrow-band interference wave b1 is averaged over the entire frequency band by spreading, so that the level of the narrow-band interference wave b2 is sufficiently low. As a result, the level of the signal on which the spread signal a2 and the narrow band interference wave b2 are superimposed does not have a great difference from the level of the original spread signal a1. In the mixer 7, the power of the spread code input from the spread signal generator 8 is also added to the spread signal, but this can be considered in advance.

The re-spread signal is supplied to a band-pass filter 9.
Is input to In FIG. 2B, c represents the pass band of the band pass filter 9. From the spread signal, a signal unnecessary for level detection is removed by a band-pass filter 9, input to a detector 10, its level is detected, and input to a variable gain amplifier 11 as a gain control signal. As described above, since the levels of the spread signal a1 and the signal in which the narrow band interference wave b2 is superimposed on the spread signal a2 are almost the same, the level of the signal detected by the detector 10 is equal to the level of the spread signal. It can be seen that they almost match. In this way, the level of the spread signal can be detected with a single filter and detector without considering the frequency of the narrow band interference wave.

On the other hand, the spread signal input to the amplification factor variable amplifier 11 is amplified according to the signal from the detector 10, the signal having a certain level or higher on the frequency axis is limited by the magnetostatic wave filter 12, and is output. .

FIG. 3 shows the spectrum (a) of the signal input to the variable gain amplifier 11, the spectrum (b) of the output signal, and the spectrum (c) of the signal output from the magnetostatic wave filter 12. In FIG. 3A, the spread signal d1 includes a narrow band interference wave e1. Also r
Indicates the saturation level of the magnetostatic wave filter 12. As described above, at the stage of input to the variable gain amplifier 11, the level of the spread signal d 1 is the saturation level r of the magnetostatic wave filter 12.
Does not match. The amplification factor variable amplifier 11 amplifies according to the signal from the detector 10 such that the level of the spread signal d1 matches the saturation level r of the magnetostatic wave filter 12. As a result, as shown in FIG.
2 and the narrow-band interference wave e2 are amplified so that the level of the spread signal d2 and the saturation level r of the magnetostatic wave filter 12 match. In the magnetostatic wave filter 12, signals having a level higher than the saturation level r on the frequency axis are limited. Therefore, as shown in FIG. 3C, the level of the narrow band interference wave e3 is limited to the same level as the level of the spread signal d3.
In this way, narrow band interference waves having a higher level than the spread signal are removed.

The signal from which the narrow-band interference wave has been removed is frequency-converted by a mixer 14, unnecessary signals are removed by a band-pass filter 15, amplified by an amplifier 16 and input to a matched filter 17. And matched filter 1
The signal is despread by 7, amplified by an amplifier 18, and unnecessary signals are removed by a low-pass filter 19, demodulated by a demodulator 20, and output from an output terminal 21.

FIG. 4 shows another embodiment of the spread spectrum communication apparatus according to the present invention. In FIG. 4, the same or equivalent parts as those in the embodiment of FIG. 1 are denoted by the same reference numerals, and description of the configuration and operation is basically omitted. In FIG. 4, the narrow band interference wave removing circuit 31 of the spread spectrum communication apparatus 30 includes a distributor 6, a mixer 7, a spread code generator 8, a band pass filter 9, a detector 10, a frequency / time conversion circuit 32, an amplitude limiter. The circuit 33 includes a time / frequency conversion circuit 34.

In the narrow-band interference wave removing circuit 31, the input side is connected to the distributor 6, and two outputs of the distributor 6 are connected to the mixer 7 and the frequency / time conversion circuit 32. A spreading code generator 8 is also connected to the mixer 7. The output of the mixer 7 is connected to the amplitude limiting circuit 33 via the band pass filter 9 and the detector 10. On the other hand, the frequency / time conversion circuit 3
2 is connected to the amplitude limiting circuit 33, and the output of the amplitude limiting circuit 33 is connected to the output side via the time / frequency conversion circuit 34.

The signal input to the narrow-band interference wave removing circuit 31 is divided into two by the distributor 6, one of which is input to the mixer 7, and the other is input to the frequency / time conversion circuit 32. The spread code generator 8 generates a spread code different from the spread code obtained by spreading the received spread signal or a spread code having a different chip rate. The spread signal input to the mixer 7 is spread again by a different spread code from the spread code generator 8. The re-spreading is the same as that described in the embodiment shown in FIG.

On the other hand, the signal input to the frequency / time conversion circuit 32 is frequency / time converted, becomes a signal whose amplitude changes on the time axis, and is input to the amplitude limiting circuit 33. The amplitude is limited by the amplitude limiting circuit 33 in accordance with the signal from the detector 10, and is returned and output by the time / frequency conversion circuit 34.

FIG. 5 shows the spectrum (a) of the signal input to the frequency / time conversion circuit 32 and the waveform (b) of the output signal, and the waveform (c) of the signal output from the amplitude limiting circuit 33 and the time. The spectrum (d) of the signal output from the frequency conversion circuit 34 is shown. In FIG. 5A,
The spread signal f1 includes the narrow band interference wave g1. This signal is frequency / time converted by the frequency / time conversion circuit 32, becomes a signal whose amplitude changes on the time axis, and is input to the amplitude limiting circuit 33. The waveform of this signal is shown in FIG. In FIG. 5B, f2 is a spread signal, and g2 is a narrow band interference wave. The amplitude limiting circuit 33 limits the amplitude of the narrow band interference wave g2 according to the signal from the detector 10 so as to match the amplitude of the spread signal f2. As a result, as shown in FIG. 3C, the narrow band interference wave g3 becomes the spread signal f3.
It is limited to the same amplitude as. The output of the amplitude limiting circuit 33 is time-frequency converted by the time-frequency conversion circuit 34 and output. FIG. 5D shows the spectrum of the time-frequency converted signal. The narrow-band interference wave g4 has dropped to the same level as the level of the spread signal f4. In this way, narrow band interference waves having a higher level than the spread signal are removed.

[0026]

According to the spread spectrum communication apparatus of the present invention, a part of the spread signal is re-spread with a spread code different from the spread code obtained by spreading the spread signal, and the level of the re-spread signal is detected. Thus, the level of the spread signal can be detected with a single filter and detector without considering the frequency of the narrow-band interference wave.

Also, by utilizing the level of the detected spread signal, the spread signal is reduced by a combination of a variable amplification factor amplifier and a magnetostatic wave filter or a combination of a frequency / time conversion circuit, an amplitude limiting circuit, and a time / frequency conversion circuit. High-level narrow-band interference waves can be removed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a spread spectrum communication apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram of the spread spectrum communication apparatus shown in FIG.
FIG. 7A is a diagram illustrating a state of respreading of a spread signal, in which FIG. 7A illustrates a spectrum of a spread signal before respread, and FIG. 7B illustrates a spectrum of a spread signal after respread.

FIG. 3 shows a spread spectrum communication apparatus shown in FIG.
FIGS. 7A and 7B are diagrams showing a state of removing a narrow band interference wave, wherein FIG. 7A shows a spectrum of a signal input to a variable gain amplifier, FIG.
(C) shows the spectrum of the signal output from the magnetostatic wave filter.

FIG. 4 is a block diagram illustrating a configuration of a spread spectrum communication apparatus according to another embodiment of the present invention.

FIG. 5 is a diagram showing a state of removing a narrow-band interference wave in the narrow-band interference wave removal circuit of the spread spectrum communication apparatus shown in FIG. 4, wherein (a) shows a spectrum of a signal input to a frequency / time conversion circuit; (B) is the waveform of the signal output from the frequency / time conversion circuit, (c) is the waveform of the signal output from the amplitude limiting circuit, and (d) is the signal output from the time / frequency conversion circuit. FIG. 4 is a diagram showing a spectrum of FIG.

FIG. 6 is a block diagram showing a configuration of a circuit for detecting a level of a spread signal in a conventional spread spectrum communication apparatus.

FIG. 7 is a block diagram of the spread spectrum communication apparatus shown in FIG.
FIG. 3 is a diagram illustrating a relationship between a spread signal and a bandpass filter.

[Explanation of Codes] 1 ... Spread spectrum communication apparatus 2 ... Antenna 3, 9, 15 ... Bandpass filter 4, 16, 18 ... Amplifier 5 ... Narrow band interference wave removing circuit 6 ... Distributor 7, 14 ... Mixer 8 ... Spread Code generator 10 Detector 11 Variable gain amplifier 12 Magnetostatic wave filter 13 Local signal source 17 Matched filter 19 Low-pass filter 20 Demodulator 21 Output terminal

Claims (3)

[Claims] 1. A spread spectrum communication apparatus comprising at least signal receiving means for receiving a spread signal spread spectrum by a spreading code, and a narrow band interference wave removing circuit for removing a narrow band interference wave included in the spread signal. A narrow-band interference wave removing circuit for re-spreading a part of the spread signal with the spreading code different from the spreading code obtained by spreading the spread signal; and detecting a level of the re-spread spread signal. And a narrow band interference wave limiting circuit for limiting the level of a narrow band interference wave having a higher level on the frequency axis than the spread signal included in the spread signal according to the level detection circuit. Spread spectrum communication equipment. 2. The narrow-band interfering wave limiting circuit includes an amplification factor variable amplifier that changes an amplification factor according to the level detection circuit, and a magnetostatic wave filter that operates as a limiter that limits a level on a frequency axis. The spread spectrum communication apparatus according to claim 1, wherein: 3. The narrow-band interfering wave limiting circuit includes a frequency-time converting circuit that converts a spectrum of the spread signal into a time signal, and an amplitude of the frequency-time converted spread signal according to the level detecting circuit. 2. The spread spectrum apparatus according to claim 1, comprising an amplitude limiting circuit for limiting on a time axis, and a time / frequency converting circuit for returning the spread signal subjected to frequency / time conversion and amplitude limited to a spectrum. Communication device.