JP2737508B2 - Spread spectrum receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the improvement of reception characteristics of a direct spread spectrum / spread spectrum receiver under multiple propagation paths (multipath).

[0002]

2. Description of the Related Art FIG. 3 is a diagram illustrating a PDI (Post Demultiplexer) which is a kind of path diversity disclosed in, for example, "Spread Spectrum Communication System" Science and Technology Publishing Company (1988) by Mitsuo Yokoyama.
cisionIntegrator) is a configuration of a direct spread / spread spectrum receiver. In the figure, 1 is a matched filter or S
Correlator using AW element etc., 2 is one symbol time TS
Delay circuit for delaying the correlator output only by 3
A multiplier for multiplying the output of the correlator 1 by the output of the correlator and the output of the correlator 1 is a time (delay spread) in which a delayed wave exists.
An integrator that integrates the output of the multiplier 3 by T M, and 5 is a data determiner that determines the output of the integrator 4.

Next, the operation will be described. PDI of FIG.
The direct spread / spread spectrum receiver receives the direct spread / spread spectrum signal, performs frequency conversion, band limitation, and the like, and inputs the received signal to the correlator 1. The correlator 1 performs direct spreading / despreading of the spread spectrum signal (correlation processing) using the received signal and the same spread code used for spread spectrum on the transmitter side. 4A and 4B show an example of the correlation waveform after despreading. Here, FIG. 4A is a diagram showing an example of a correlation waveform in the case where there is no delay wave due to a multiplex propagation path (multipath), and FIG. 4B is a diagram showing the correlation waveform in the case where a delay wave exists. It is a figure showing an example.

[0004] In FIG. 4A, reference numerals 101 and 102 denote correlation peaks of a preceding wave, and a horizontal axis 103 denotes a time axis;
Reference numerals 4 and 105 are a real axis and an imaginary axis representing the phase of the received signal. The interval between the correlation peaks is one information symbol time T
S. Further, reference numerals 106 and 107 in FIG. 4B denote correlation peaks of the delayed wave of the preceding wave 101 generated by the multipath (multipath). Similarly, 108 and 109 are correlation peaks of the delayed wave due to the preceding wave 102. The time from the correlation peak of the preceding wave to the correlation peak of the delayed wave having the longest delay is defined as TM. It should be noted that the phase difference between the correlation waveforms 106 and 108 of the delayed wave, and the similar 107 and 109, is substantially equal to the phase difference between the correlation peaks 101 and 102 of the preceding wave.

[0005] The delay circuit 2 delays the signal from the correlator 1 by one information symbol time TS, and the multiplier 3 multiplies the output (correlation waveform) of the correlator 1 by the delay circuit 2 by the correlation waveform delayed by TS. (Delay detection). As a result, a signal corresponding to the phase difference between two correlation waveforms different by one information symbol time is obtained at the output of the multiplier 3. For example, when the correlation waveform is as shown in FIG. 4A, a signal corresponding to the phase difference between the correlation peaks 101 and 102 is obtained at the output of the multiplier 3. In a spread spectrum receiver that performs only differential detection without using ordinary PDI, the correlation peaks 101 and 10 of the preceding wave are used.
The data is determined by the data determiner 5 using the phase difference of 2.

The integrator 4 integrates the output of the multiplier by the time T M to obtain a signal corresponding to the phase difference between the preceding waves 101 and 102, which are temporally dispersed by the delay spread due to the multiple propagation paths, and Signals corresponding to the phase differences between the delayed waves 106 and 108 and 107 and 109 whose delay time is equal to or less than TM are integrated (combined) with the waves. The output of the integrator 4 is determined by the data determiner 5, and the result of the determination is output.
As a result of the above, when PDI is not used, data determination is performed using only the phase difference of the peak of one correlation waveform (correlation waveform of the preceding wave). Since the phase difference between the preceding wave and the delayed wave) is integrated (synthesized) and the judgment is made using the synthesized result,
When a delayed wave is present, diversity gain is obtained.

Hereinafter, the influence of the odd correlation in the conventional direct spread spectrum / spread spectrum receiver configured as described above will be described. For example, a 7-chip PN sequence (-1, -1, + 1, + 1, + 1, -1, + 1) is used as a spreading code of the direct spread / spread spectrum communication system, For the transmission information 1, this spreading code is transmitted as it is,
For transmission information 0 after differential encoding, it is assumed that the spectrum is spread by inverting and transmitting +1 and −1 of this spreading code (when performing delay detection on the receiving side, usually,
Differential coding is performed on the transmitting side). When the transmission information of 1,1,1 is spread-modulated using the above PN sequence,
The transmission signal is (-1, -1, + 1, + 1, + 1, -1, + 1, -1, -1, + 1, + 1, + 1,-
1, + 1, -1, -1, + 1, + 1, + 1, -1, + 1).

Next, the above transmission signal is received, and the same spreading code (-1, -1, + 1, + 1, + 1, + 1, -1, + 2) as that used on the transmission side is received.
FIG. 5A shows a correlation waveform when the correlation processing is performed in 1). In the figure, reference numerals 110, 111, and 112 denote peaks (correlation peaks) of the correlation waveform, and the sign of the peak value corresponds to 1,0 of the transmission information. On the other hand, if 1, 0, 1 is used as the transmission information, the spread modulated transmission signal is (-1, -1, + 1, + 1, + 1, -1, + 1, + 1, + 1). , -1, -1, -1, + 1, -1, -1,-
1, + 1, + 1, + 1, -1, + 1), and receives the above transmission signal,
The same spreading code (-1, -1, + 1, + 1, + 1,
FIG. 5B shows a correlation waveform when the correlation processing is performed at (+1, +1). In the latter case, the correlation waveforms are points 113, 114, other than peaks 110, 111, 112.
It can be seen that there is a large fluctuation at 115 and 116. This variation is the effect of the odd correlation, the shape and magnitude of this variation is specific to each spreading sequence,
This variation may or may not occur depending on the transmission information.

[0009]

To achieve the above object, according to the Invention The spread spectrum receiver according to the present invention, spectrum
A correlator for despreading the received signal that has been
A delay detector for delay-detecting the output of the correlator;
The final signal of the output signal and the data
And the output of the road as input, and correlate from the output of the final data
Judgment is made as to whether there is a change in the waveform due to odd correlation and there is a change
If the delay detection output is used for processing required for final data
Odd correlation between preceding and delayed waves
And cancel the fluctuations caused by the
A propagation path detector with a compensating circuit that outputs
Weighting coefficient output by the channel detector with compensation circuit
A multiplier for multiplying the output of the delay detection section, and an output of the
An integrator that adds the force for a specified time and performs diversity
Data judgment to judge the output of the integrator and output the final data
Equipped with a measuring instrument.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem. Even when a phase difference of a correlation waveform due to an odd correlation occurs, the variation of the correlation waveform due to the odd correlation is removed by a canceller, and reception is performed. It is an object of the present invention to obtain a direct spread / spread spectrum receiving apparatus in which deterioration of characteristics is prevented.

[0011]

In order to achieve the above object, a direct spread / spread spectrum receiver according to the present invention comprises a correlator for despreading a received signal and a delay circuit for delaying the correlator output. And a multiplier for multiplying the output of the delay circuit and the output of the correlator, a propagation path detecting unit for detecting a preceding wave and a delayed wave from the multiplier output, and using the preceding wave and the delayed wave detected by the propagation path detecting unit. A direct-spread / spread-spectrum receiver configured to perform path diversity by including a circuit that removes a noise component from the multiplier output and an integrator that integrates the output of the multiplier, using a determination result of the receiver; ,
An odd-correlation canceller for canceling the influence of the odd-correlation component of the correlator output is provided.

[0012]

The direct-spread / spread-spectrum receiver configured as described above detects whether or not the correlation waveform fluctuates due to the influence of the odd correlation by using the determination result. By using the correlation waveform from which the variation of the correlation waveform has been removed, and using the correlation waveform from which the variation has been removed, it is possible to prevent the diversity gain from deteriorating due to the influence of the odd correlation.

[0013]

[Embodiment 1] FIG. 1 is a block diagram showing the configuration of a first embodiment of a direct spread spectrum / spread spectrum receiver according to the present invention. In the figure, 7 is a correlator for despreading a received signal,
Reference numerals 6a and 6b denote delay detectors of the in-phase and quadrature channels, respectively. Delay detector outputs 10 and 11 are input to a propagation path detector 17 having a compensation circuit. The output 18 of the propagation path detector with compensation circuit is input to the multipliers 9a and 9b, and is multiplied with the outputs of the differential detection circuits 6a and 6b, respectively. The multiplication result is integrated by the integrator 4, and the integration result is determined and output by the data determination unit 5. The determination result is also input to the propagation path detection unit 17 with a compensation circuit. In this embodiment, QP is used as the modulation method.
Since the case where orthogonal modulation such as SK is used is described as an example, the correlator 7 is for a quadrature modulation and demodulation method.
The delay detectors 6a and 6b, the integrators 4a and 4b, etc. use two systems for the in-phase channel and the quadrature channel.

FIG. 2 is a block diagram showing the internal configuration of the propagation path detecting unit 17 with a compensation circuit shown in FIG. In the figure, reference numerals 13a and 13b denote squarers for squaring the output signals of the delay detection units 6a and 6b, 14 an adder for adding the outputs of the in-phase channel and quadrature channel squarers 13a and 13b, and 20
Reference numeral denotes a delay circuit for delaying the output of the adder 14, and reference numeral 21 denotes an odd correlation canceller for canceling the influence of the odd correlation by using the determination result of the output of the determiner 5 and the output of the determination circuit 16. Reference numeral 15 denotes a cyclic adder. Reference numeral 16 denotes a determination circuit that outputs 1 when the result of the cyclic addition of 15 exceeds a predetermined threshold value, and outputs 0 otherwise.

The operation of the direct spreading / spread spectrum receiving apparatus configured as described above will be described. The received signal is subjected to despreading (correlation processing) by the correlator 7 and differentially detected by each of the differential detection units 6a and 6b. As a result, a signal corresponding to the phase difference of the correlation waveform of the time difference of one symbol is obtained at the outputs of the delay detection units 6a and 6b. further,
From the outputs of the differential detectors 6a and 6b,
The square of the absolute value of the phase difference of the correlation waveform is obtained by the adder 14 via a and 13b. The square of the absolute value of the phase difference of the correlation waveform is determined by the delay circuit 20 by the integrators 4a and 4a.
b and the time corresponding to the processing time of the data decision unit 5 is delayed.

In the odd correlation canceller 21, the data decision unit 5
From the determination result of the transmission information obtained in (1), it is estimated whether or not the fluctuation of the correlation waveform occurs due to the odd correlation. Since the presence or absence of a change in the correlation waveform due to the odd correlation is determined by the transmission information, the presence or absence of the change in the correlation waveform due to the odd correlation can be estimated from the determination result of the received signal. If the correlation waveform fluctuates due to the influence of the odd correlation, only the fluctuation of the correlation waveform due to the odd correlation between each of the preceding wave and the delayed wave is obtained by using the position information of the preceding wave and the delayed wave obtained by the determination circuit 16. Counteract. The form of the variation of the correlation waveform due to the odd correlation is uniquely determined by the spreading code, so if the positions of the preceding wave and the delayed wave are known,
The fluctuation of the correlation waveform due to the odd correlation at a certain time can be estimated. The signal from which the influence of the odd correlation is canceled by the odd correlation canceller 21 is cyclically added by the cyclic adder 15 to emphasize the peak of the correlation waveform and suppress noise components other than the phase difference between the peaks of the correlation waveform.

[0017] In the judging circuit 16, a cyclic addition result, by determining whether more than a preset threshold value, to detect the position of the preceding wave and a delayed wave, when the preceding wave and the delayed wave is present Outputs 1 as a weighting factor,
Otherwise, 0 is output. By multiplying the outputs of the delay detectors 6a and 6b with the weighting coefficients by the multipliers 9a and 9b, only the phase difference components of the correlation waveforms caused by the preceding wave and the delayed wave are supplied to the integrators 4a and 4b. The other noise components are not supplied to the integrator 4. As a result, the integrators 4a, 4
In b, only the phase difference between the correlation waveform peaks (correlation peaks) is integrated (combined), and noise components such as fluctuations in the correlation waveform due to the influence of the odd correlation are not integrated, so that it is possible to prevent the diversity gain from deteriorating.

In the direct spreading / spread spectrum receiving apparatus configured as described above, the odd correlation canceller removes the fluctuation of the correlation waveform due to the influence of the odd correlation. Therefore, it is possible to prevent integration of the correlation waveform fluctuation due to the influence of the odd correlation, and to prevent deterioration of the diversity gain.

In the first embodiment, the squarers 13a, 13
Although b is used, a circuit for obtaining an absolute value may be used instead of the squarer.

In the first embodiment, 1,0 is used as a weighting coefficient, but other coefficients may be used.

In the first embodiment, a cyclic adder is used to suppress noise components. However, the same applies when a moving average is used instead.

Similar effects can be obtained even when the positions of the preceding wave and the delayed wave are detected without using noise suppression means such as cyclic addition and moving average.

The delay circuit 20 is used for compensating for processing delays of the integrator 4, the data judging unit 5 and the like. If the processing delay is compensated, the delay circuit is moved to another position in the block diagram. The same applies when the circuit 20 is installed.

[0024]

Since the present invention is configured as described above, it has the following effects. Direct spread / spread spectrum receiving apparatus capable of accurately detecting a propagation path and preventing deterioration of diversity gain by removing a variation in a phase difference of a correlation waveform due to an odd correlation in a propagation path detection unit with a compensation circuit. Can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a direct spread / spread spectrum receiving apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing an internal configuration of a propagation path detecting unit with a compensation circuit shown in FIG. 1;

FIG. 3 is a configuration block diagram of a conventional PDI direct spread / spread spectrum receiver.

FIG. 4 is a diagram showing an example of a correlation waveform for explaining the operation of a conventional PDI direct spread / spread spectrum receiver.

FIG. 5 is a diagram illustrating an example of a variation in a correlation waveform due to an odd correlation in a conventional PDI direct spread / spread spectrum receiver.

[Explanation of symbols]

 Reference Signs List 1 correlator 2 delay circuit 3 multiplier 4 integrator 5 data determiner 6a, 6b delay detector 7 quadrature modulation correlator 9a, 9b multiplier 10 in-phase channel signal path 11 orthogonal channel signal path 13a, 13b Squarer 14 Adder 15 Cyclic adder 16 Judgment circuit 17 Propagation path detector with compensation circuit 18 Path of weighting coefficient 19 Path of data judgment result 20 Delay circuit 21 Odd correlation canceller 101 Correlation peak of preceding wave 102 Correlation of preceding wave Peak 103 Time axis 104 Real number axis 105 Imaginary axis 106 Delayed wave correlation peak 107 Delayed wave correlation peak 108 Delayed wave correlation peak 109 Delayed wave correlation peak 110 Correlation peak 111 Correlation peak 112 Correlation peak 113 Correlation waveform due to odd correlation Fluctuation 114 Fluctuation of correlation waveform due to odd correlation 115 Odd phase Variation of correlation waveform due to Seki 116 Variation of correlation waveform due to odd correlation

Claims (1)

(57) [Claims] Despreading of a spread spectrum received signal.
A delay detector for delay-detecting the output of the correlator, and the final data of the delay-detected signal and the data discriminator output.
Data and the output of the determination circuit as inputs, and
Judge from the output whether the correlation waveform has fluctuation due to odd correlation
If there is a fluctuation, the delayed detection output is
From the one delayed by the processing time required for
Leading and delayed waves canceling out fluctuations caused by odd correlation of delayed waves
With a compensation circuit that determines the position of the
Carrier path detector and weighting coefficient output by the propagation path detector with compensation circuit
With the output of the delay detection unit, and the output of the multiplier is added for a specified time to perform diversity.
An integrator and data for judging an output of the integrator and outputting final data.
And a spread spectrum receiving apparatus comprising: