JPH0644255U - Compensation filter circuit and spread spectrum transmitter / receiver - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve the C / N of the receiver by setting the total transmission power to the standard value with the SS signal of the DS system, and to increase the transmission distance between the transmitter and the receiver. Receiver and D
Suppression of large-amplitude interference that occurs when using the ISM band in an AB receiver. [Structure] A plurality of narrow band filters 22 are provided for the SS signal band.
, And the center frequencies f1, ..., f as shown in FIG.
Configure N subbands. Taking the fN channel shown in FIG. 1 (B) as an example, the output of the fN channel (22-N) demultiplexed by the narrow band filter 22 is the input signal of the input signal by the narrow band limiter 23 as shown in FIG. 1 (C). Amplitude VS (Fig. 1
When (D)) exceeds ± ER, it is saturated and a constant amplitude is output (FIG. 1 (E)). Similarly, the outputs of the other channels are also limited in amplitude by each narrow band limiter 23, combined by the adder 24 and output to the amplifier 17. Since this output is limited by each narrow band limiter 23, the power density distribution becomes flat.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a direct sequence spread spectrum transmission / reception system.

[0002]

[Prior art]

 FIG. 9 is a block diagram showing the basic configuration of a spread spectrum (hereinafter referred to as SS) transmission / reception system. In FIG. 9, 100 "indicates a DS system SS transmission system, and 200" indicates a DS system SS reception system. Then, 1 is an information signal and most are data signals. Reference numeral 2 is a modulator, which uses a frequency modulator (FM) or a digital phase modulator (PSK). 2'is a carrier wave generator, 3 is a multiplier or a polar modulator (PSK), 4 is a pseudo noise generator (PNG), 5 is a band filter, 6 is a transmitting antenna, 7 is a receiving antenna, 8 is a band pass amplifier. , 9 is a frequency converter, 10 is a local frequency oscillator, 11 is a correlator (SAW convolver, etc.), 12 is a polar modulator (PSK), 13 is a carrier wave, and 14 is a pseudo noise generator (PNG). The amplitude (envelope) of the output of the modulator 2 is constant. Further, the carrier wave generator 2 ′ is not indispensable and may be used as needed depending on the type of the modulator 2.

The information signal 1 is modulated by a modulator 2, added to a multiplier (or a polarity modulator) 3, frequency-spread modulated at the output of PNG 4, and output from a transmission antenna 6 via a bandpass filter 5 (amplifier). To do.

A received signal received by the receiving antenna 7 is amplified by a bandpass amplifier 8 and converted by the outputs (carrier frequency) of the frequency converter 9 and the local frequency oscillator 10 into an appropriate frequency by the correlator 11. On the other hand, the PNG 14 generates pseudo noise having the same pattern as the PNG 4, modulates the carrier wave (the same frequency as the output of the frequency converter 9) 13 with the PSK 12, adds it to the correlator 11, and takes out the correlation output 11 ′ of the correlator 11. .

FIG. 10 is a frequency distribution diagram of an SS signal of a direct spread system (hereinafter referred to as a DS system). For example, an SS signal in the ISM band (2.45 GHz) has a band of B = 26 MHz. The voltage distribution is a (sinx / x) type that is convex upward with respect to f ₀ . Therefore, the power density distribution is of the (sin ² x / x ² ) type. The power density of SS signals regulated by law is limited per Δf = 1 MHz.

In the DS method of FIG. 10, as shown in the measurement result diagram of the radio wave density of the SS signal of FIG. 11, the value of Δf = 1 MHz centering on f ₀ is the maximum value, and the transmission output is at this maximum value. To be suppressed. If the maximum power density is constant over the band B, the limit power density distribution shown by the broken line 101 in FIG. 10 is obtained. The density ρ in the case of the DS method is about 40% of the limit power density according to the following mathematical formula. ρ = (1 / π) ∫sin ² x / x ² (however, the integration range is 0 to π)

[0007]

[Problems to be solved by the device]

 <First problem to be solved> When performing SS communication in the ISM band, there is a strong band interference wave (which may be 100 times the value of the SS signal) that occurs when a microwave oven or the like is used. There is. FIG. 5 is a diagram showing the existence spectrum of a wideband modulated wave and a large-amplitude interfering wave. FIG. 5 (a) is a frequency distribution when an SS signal component 51 has an interfering wave (NcosωNt) 52 of frequency fN. . When this is viewed on the time axis, it becomes as shown in FIG. 6 (a) showing an example of coexistence of a large amplitude interfering wave and a small amplitude modulated wave, and FIG. 6 (b) is an enlarged view of that portion. When such a large-amplitude interfering wave is present, when the necessary processing in the SS receiver is performed, in which the amplified received signal is frequency-converted and added to the correlator, the SS signal component is It easily disappears.

FIG. 7 shows an example in which a received signal is passed through an amplitude limiter (limiter), but if the amplitude of the interference wave Ncosω Nt is large, the waveform will be close to that of FIG. Except for this, the signal component disappears, and there is the drawback that signal restoration by the correlator tends to be impossible.

In order to solve this, there is a system using an AIS (Adaptive Interface Suppresion) filter. In the method using the AIS filter, the frequency fN of the narrow-band large-amplitude interference wave in (a) of FIG. 5 is detected, and the frequency distribution shown in (c) of FIG. Then add it to the correlator. In this method, since the filter is controlled after detecting the frequency, the control becomes complicated, and when the frequency fN fluctuates, there is a problem that the detection of the frequency fN and the control of the filter may not correspond to each other.

On the other hand, the satellite broadcasting of the DAB (Digital Audio Broadcasting) system is permitted at 2.5 GHz in Japan, and in this case also, there is a strong interference wave related to IS. FIG. 5B is a frequency demultiplexer in the case where a narrow-band large-amplitude interfering wave of frequency fN exists in the received carrier wave of DAB. DAB is also aiming for frequency diversity effect as a received carrier wave. FIG. 5D shows the case where the subband of the interference wave Ncosω Nt in FIG. 5B is set to zero, and in this case also the information is correctly restored. However, the method of changing from (b) of FIG. 5 to (d) of FIG. 5 is not disclosed at this time. Therefore, in the case of (b) of FIG. 5, it is expected that the signal component will be lacking due to the limiter effect as shown in FIG. 7 in the large-amplitude interfering wave NcosωNt as in the case of the SS signal.

<Second Problem to Be Solved> Further, in the SS signal of the DS system, unlike other SS signals, if the power density is constant, the power becomes about 40% of the limit total power, and the C / N of the received signal is There was a problem that it deteriorated and the reaching distance decreased.

The present invention has been made in view of the above problem to be solved, and a first object of the present invention is to improve the C / N of a receiver by setting the total transmission power to the standard value with the SS signal of the DS system to improve the transmission. The second purpose is to increase the transmission distance between the receiver and the receiver. The second purpose is the band that matches the ISM band, and the SS receiver and DAB receiver are used for industrial, scientific, medical, etc. ISM purposes. It is to suppress large-amplitude interference that can occur when using bands and to perform reliable information restoration.

[0013]

[Means for Solving the Problems]

 In order to achieve the first object, the compensating circuit according to the first invention outputs a predetermined wideband input signal subjected to frequency spread processing to a plurality of channels via a plurality of narrowband characteristic filters having different center frequencies. The narrow band filter means for synthesizing the plurality of channel outputs having a constant amplitude and the amplitude suppressing means for obtaining a plurality of channel outputs having a constant amplitude suppressed to the level when the plurality of channel outputs are equal to or higher than a predetermined level. And a synthesis processing means.

In order to achieve the second object, a spread spectrum transmission / reception apparatus according to a second aspect of the present invention is a transmission system for performing frequency spread processing on a modulated predetermined information signal with a predetermined pseudo noise signal and outputting it as a transmission signal. A receiving system that receives a transmission signal, converts the reception signal to a frequency necessary for correlation processing, and then performs correlation processing with a modulation signal that is a signal substantially equivalent to a pseudo noise signal and a predetermined carrier signal to obtain a correlation output. In a direct-spectrum spread spectrum transmission / reception device consisting of, the transmission system includes a transmission-side compensation filter unit that flattens and outputs the power density distribution of the signal that has been frequency-spread by the pseudo noise signal, and the reception system Includes a receiving side compensating filter section for outputting a received signal via a sinx / x type characteristic filter that reduces the amplitude level.

According to a third aspect of the present invention, in the spread spectrum transmitter / receiver according to the second aspect, the transmitting side compensating filter section comprises the compensating filter circuit according to the first aspect, and the receiving side compensating filter section has sinx / x type characteristics. It is characterized in that the compensation filter circuit according to the first invention is provided in the preceding stage of the filter.

According to a fourth aspect, in the spread spectrum transmitter / receiver according to the second aspect, the transmitting side compensating filter section comprises an x / sinx type characteristic filter and the receiving side compensating filter section comprises a sinx / x type characteristic filter. It is characterized by

[0017]

[Action]

 With the above configuration, the compensating circuit according to the first aspect outputs a predetermined wideband input signal, which has been frequency-spread by the narrowband filter means, to a plurality of channels via a plurality of narrowband characteristic filters having different center frequencies, When the plurality of channel outputs are equal to or higher than a predetermined level by the amplitude suppressing means, the plurality of channel outputs of constant amplitude suppressed to the level are obtained, and the plurality of channel outputs of constant amplitude are combined by the combining processing means. .

In the spread spectrum transmitter / receiver according to the second invention, the transmission system flattens and outputs the power density distribution of the signal subjected to the frequency spread processing by the pseudo noise signal by the transmission compensation filter unit, and the reception system The reception side compensating filter section outputs the reception signal through a sinx / x type characteristic filter that reduces the amplitude level, and flattens the maximum power density distribution of the transmission output.

[0019]

【Example】

Hereinafter, the first device will be described as a first embodiment and the second device will be described as an embodiment 2-1 and an embodiment 2-2. The power density distribution of the DS SS signal of FIG. 10 is a distribution of (sinx / x) ² , but this is a rectangular characteristic indicated by a broken line 101 within the band (x = −π to + π). In the second invention, in Example 2-1, a narrow band demultiplexer with a limiter is provided on the output side of the DS system in the second invention, and in Example 2-2, the transmission is performed. On the system side, a voltage (x / sinx) type compensation filter is provided at the output of the DS system.

<Embodiment 1> FIG. 1B is an explanatory diagram of a configuration of a duplexer with a limiter as an embodiment of a compensation filter circuit based on the first invention. The duplexer with a limiter is a narrow band filter 22 ( 22-1, ..., 22-N), limiters 23-1, ..., 23-N provided corresponding to the narrow band filters 22-1, ..., 22-N and an adder 24. . The limiter 23 corresponds to amplitude suppressing means, and the adder 24 corresponds to combining processing means.

In FIG. 1, the band of the output (SS signal) from the amplifier is divided by a plurality of narrow band filters 22-1, ..., 22-N, and the center frequencies f1, ..., As shown in FIG. Construct f N subbands. Next, regarding each subband, taking the fN channel shown in FIG. 3B as an example, the output of the fN channel (22-N) demultiplexed by the narrowband filter 22 is amplitude-limited by the narrowband limiter 23-N. It The characteristic distribution of the limiter 23 -N is as shown in FIG. 1C, when the input signal amplitude VS (see FIG. 1D) exceeds ± ER, in other words, VS> + ER or VS <−ER. Saturated and outputs a constant amplitude. The square waveform shown by the solid line in FIG. 1 (E) is the waveform of the output signal (subband) whose amplitude is limited by the limiter 23-N, and is shown by the broken line in FIG. 1 (E) when the limiter 23-N is not provided. It has a waveform (same as in FIG. 1D).

The outputs of the other channels f1, ..., FN-1 are similarly limited in amplitude by the limiters 23-1, ..., Limiter 23-N. Then, the outputs of the limiters 23-1, ..., Limiter 23-N are combined by the adder 24 and output to the amplifier 17.

Since the output of the branching filter with limiter thus obtained is limited by the limiters 23-1, ..., Limiter 23-N, the power density distribution is flat as shown by the broken line 101 in FIG. Becomes Although the duplexer with limiter in FIG. 1 may be configured by an individual circuit, an equivalent circuit of a magnetostatic wave (MSW) filter made of YIG (Ytrium Iron Garmet) as shown in FIG. 12 is shown in FIG. Since the branching filter with limiter is used, if the MSW filter is used instead of the branching filter with limiter, the power density distribution of the output signal can be flattened like the broken line 101 shown in FIG. For the MSW filter shown in Fig. 12, refer to the literature (Shunsuke Nomoto, "SN Enhancer Using Two MSSW Filters and Their Applications," IEICE Technical Report Vol.MW 90-99 P15-P21 1991. ).

By using a duplexer with a limiter as shown in FIG. 1 as a compensation circuit in a receiver of SS communication or DAB system satellite broadcasting, a large amplitude as shown in FIG. The interfering wave (NcosωNt) 52 can be removed to obtain the waveform as shown in FIG. 5 (c), or the residual interfering wave can be made small enough not to affect the subsequent processing as shown in FIG. 5 (d). be able to. For example, when a waveform having an interfering wave as shown in FIGS. 5A and 5B is added to the duplexer 16 with a limiter shown in FIG. 1, only a band having a large-amplitude spectrum is limited in amplitude. The waveforms shown in (a) and (b) can be obtained, and the signal of the hatched partial subband N becomes small.

FIG. 13 shows an example in which the duplexer with a limiter (or MSW filter) described above (FIG. 1) is applied to a satellite communication receiver of SS communication or DAB system. In FIG. 13, the reception input from the antenna 107 is high-frequency amplified by the amplifier 108 so that at least the interfering wave NcosωNt is sufficiently saturated by the duplexer with a limiter (or MSW filter) 118 to be band-limited. To do. As a result, the frequency distributions of (a) and (b) in Fig. 5 become the frequency distributions of Fig. 8 (a) and (b), and the amplitude of the interfering wave NcosωNt becomes equal to the amplitudes of the other subbands. It is possible to sufficiently detect the subsequent signal in the receiver of the satellite broadcasting of the DAB system or the DAB system. In this case, since both SS communication and DAB system have a frequency diversity effect on a wide band signal, even if the narrow band component of the wide band signal is lost, it is restored by the demodulation circuit (including the effect of error correction). Even if a saturated subband is generated by a compensating filter circuit such as a demultiplexer with limiter or MSW filter, it does not affect the information restoration.

<Embodiment 2-1> FIG. 2 is a block diagram showing a configuration example of a spread spectrum (hereinafter referred to as SS) transmission / reception system based on the second invention, and is equivalent to the symbol shown in FIG. The structure and operation of the symbol part are the same as those of the corresponding part in FIG. In FIG. 2, 100 is a DS SS transmission system, and 200 is a DS SS reception system. Further, 15 is an amplifier, 16 and 18 are demultiplexers with limiters (or MSW filters), 17 is an amplifier, 19 is a limiter, and 21 is a (sin x / x) type filter. In FIG. 2, the amplifier 15, the demultiplexer with limiter (or MSW filter) 16 are the transmission side compensating filter units, the demultiplexer with limiter (or MSW filter) 18, the (sin x / x) type filter 21, The amplifier 19 constitutes a reception side compensation filter section.

(B) [SS Transmission System 100] The SS transmission / reception system shown in FIG. 2 has an amplifier 15 and a demultiplexer with a limiter at the output side of the bandpass filter 5 of the SS transmission system 100 ″ of the DS system shown in FIG. The device (or MSW filter) 16 and the amplifier 17 are provided in series to form a DS type SS transmission system, and the attenuation in the demultiplexer with limiter 16 is amplified by the amplifier 17 and radiated from the antenna 6. As described above (see FIG. 1), since the output of the demultiplexer with limiter 16 is limited by the limiters 23-1, ..., Limiter 23-N, the power density distribution is as shown by the broken line 101 in FIG. Becomes flat.

(B) [SS receiving system 200] Between the output side of the bandpass amplifier 8 of the SS receiving system 200 ″ shown in FIG. 9 and the frequency converter 9, a duplexer with a limiter (or MSW filter) is provided. 18, a (sin x / x) type filter 21 and a limiter 19 are provided in series to form an SS reception system 200.

In the SS receiving system 200, the received signal received by the receiving antenna 7 is amplified by the bandpass amplifier 8 and the branching filter with limiter (or MSW filter) 18 is used to show the power density distribution of the broken line 101 shown in FIG. A flat signal as shown in FIG. 2 is output to the frequency converter 9 via the (sin x / x) type filter 21 and the limiter 19. The frequency converter 9 outputs the local frequency oscillator 10 to the correlator 11 at an appropriate frequency. Convert to. On the other hand, the PNG 14 generates pseudo noise having the same pattern as that of the PNG 4, modulates the carrier wave (the same frequency as the output of the frequency converter 9) 13 with the PSK 12, adds it to the correlator 11, and extracts the correlation output of the correlator 11.

In the embodiment, the demultiplexer with a limiter (or MSW filter) 18 is used for the received input signal amplified by the bandpass amplifier 8. It is provided for suppressing the interference wave in the first embodiment) and is not essential as the basic configuration of the present invention, and thus may be omitted.

The configuration of the demultiplexer with limiter 18 is the same as that of the demultiplexer with limiter 16 shown in FIG. 1, and the output from the demultiplexer with limiter 18 is the upward direction indicated by the broken line in FIG. The limiter 19 is a (sin x / x) type filter 21 having a convex distribution characteristic, and the output of the DS SS signal is essentially constant in amplitude. It is used to As described above, a magnetostatic wave (MSW) filter using YIG shown in FIG. 12 as a material may be used in place of the duplexers 16 and 18 with limiters in FIG.

<Embodiment 1-2> FIG. 3 is a block diagram showing another configuration example of the SS transmission / reception system based on the second invention, and the configuration of the part of the symbols equal to the symbols shown in FIGS. 2 and 9. 2 and FIG. 9 are the same as those of the corresponding parts of the configuration, and 20 is an (x / sinx) type filter shown by the solid line in FIG. 4 and showing a downward convex distribution characteristic. is there.

The SS transmission / reception system shown in FIG. 3 is of the (x / sin x) type instead of the output-side amplifier 15 of the bandpass filter 5 of the DS SS transmission system 100 shown in FIG. The SS transmission system 100 ′ is configured by providing the filter 20, and the (sinx / x) type filter 21 is provided between the output side of the antenna 7 and the bandpass amplifier 8 of the SS reception system 200 ″ shown in FIG. 3, a (x / sin x) type filter 20 and an amplifier 17 are included in the transmission side compensation filter section, and a (sin x / x) type filter 21 is included in the reception side compensation filter section. Equivalent to.

FIG. 4 shows the characteristic distribution of the (x / sinx) type filter 20 by a solid line (dB display). In this case, the gain is infinite at both ends (x = ± π) of the frequency distribution band in FIG. However, since the band-pass filter 5 is provided, the compensation range of the (x / sinx) type filter 20 is up to f ₀ ± (B ′ / 2). However, B ′ is the band of the bandpass filter 5. The electric wave transmitted from the antenna 6 in FIG. 3 has a flat power density number distribution in the range of maximum f ₀ ± (B ′ / 2). The output of the receiving antenna 7 of the SS receiving system 200 'is attenuated by the (sinx / x) type filter 21.

With the above configuration, the noise power of the receiving system 200 'is reduced to about 40% (see the mathematical expression (1)), so that the C / N is improved in the processing of the bandpass amplifier 8 and below.

[0036]

[Effect of device]

 As described above, according to the first invention, the effective transmission power is increased by flattening the frequency characteristic of the power density on the transmission side of the DS system, and the (sinx / x) type filter is used on the reception side. It is possible to reduce reception noise and increase the transmission distance between the transmitter and the receiver. Also, by applying the compensation filter of the second device to a receiver for SS communication or DAB satellite broadcasting in which the input signal is wide band and large-amplitude narrow-band interference coexists, large-amplitude interference is suppressed. Then, it becomes possible to demodulate the received signals of SS communication and DAB satellite broadcasting.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a duplexer with a limiter based on a second invention.

FIG. 2 is a block diagram of a configuration example of a spread spectrum transmission / reception system based on the first invention.

FIG. 3 is a block diagram of another configuration example of the spread spectrum transmission / reception system based on the first invention.

FIG. 4 is a characteristic distribution diagram of an (x / sinx) type filter and a (sinx / x) type filter.

FIG. 5 is a diagram showing existence spectra of a wide band modulated wave and a large amplitude interference wave.

FIG. 6 is a diagram showing an example of coexistence of a large amplitude interfering wave and a small amplitude modulating wave.

FIG. 7 is a limiter output example of a coexisting wave of a large amplitude interfering wave and a small amplitude modulating wave.

FIG. 8 is a spectrum of processing by a narrow band limiter.

FIG. 9 is a block diagram of a principle configuration of a conventional spread spectrum transceiver.

FIG. 10 is a frequency distribution diagram of a direct spread SS signal.

FIG. 11 is a diagram showing a measurement result of a radio wave density of an SS signal.

FIG. 12 is an explanatory diagram of a structure of an MSW filter.

13 is an example in which the duplexer with limiter (or MSW filter) of FIG. 3 is applied.

[Explanation of symbols]

16, 18 Divider with limiter (compensation filter) 20 (x / sinx) type filter (compensation filter section on transmission side) 21 (sinx / x) type filter (compensation filter section on reception side) 22 Narrow band filter (narrow band filter) 23) Limiter (amplitude suppressing means) 24 Adder (combining processing means) 100, 100 ', 100 "DS system SS transmission system 200, 200', 200" DS system SS reception system

Claims (4)

[Scope of utility model registration request] 1. A narrow band filter means for outputting a predetermined wide band input signal subjected to frequency spread processing through a plurality of narrow band characteristic filters having different center frequencies, and a plurality of channel outputs having a predetermined level. In the above case, the compensating filter circuit comprises: an amplitude suppressing means for obtaining a plurality of constant-amplitude channel outputs suppressed to the level; and a combining processing means for combining a plurality of constant-amplitude channel outputs. . 2. A transmission system for frequency-spreading a modulated predetermined information signal with a predetermined pseudo-noise signal and outputting it as a transmission signal, and a transmission system for receiving the transmission signal and performing correlation processing on the reception signal. A direct spread spectrum spread spectrum transmitter / receiver comprising: a reception system that obtains a correlation output by performing a correlation process with a modulated signal of a signal substantially equivalent to the pseudo noise signal and a predetermined carrier signal after conversion into a frequency. Includes a transmission-side compensation filter unit that flattens and outputs a power density distribution of a signal that has been frequency-spread with the pseudo noise signal, and the reception system reduces the amplitude level of the received signal by sinx / x. A spread spectrum transmission / reception device comprising a reception side compensation filter unit for outputting via a mold characteristic filter. 3. The spread spectrum transmitter / receiver according to claim 2, wherein the transmitting side compensating filter section comprises the compensating filter circuit according to claim 1, and the receiving side compensating filter section is si.
A spread spectrum transmission / reception apparatus comprising the compensation filter circuit according to claim 1 before the nx / x type characteristic filter. 4. The spread spectrum transmitter / receiver according to claim 2, wherein the transmitting side compensating filter section comprises an x / sinx type characteristic filter, and the receiving side compensating filter section comprises sinx /
A spread spectrum transmission / reception device comprising an x-type characteristic filter.