JPH05199206A - Spread spectrum receiver - Google Patents

Abstract

PURPOSE:To prevent characteristics from being degraded in the case of bus diversity by removing noise components caused by the irregular correlation influence of correlative waveforms. CONSTITUTION:The output of a correlation equipment 7 at a PDI direct spread/ spread spectrum receiver is delayed and detected by a delay detection part 6, the output is branched and inputted to a transmission line detection part 17 with compensation circuit and the fluctuation of the correlative waveforms in irregular correlation is removed so as to detect the positions of preceding waves and delayed waves. While using the result, the output of the delay detection part 6 is weighted by a multiplier 9, and the multiplied result is integrated by an integrator 4 and judged by a data judging equipment 5.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art FIG. 3 shows a PDI (Post Decoder) which is a kind of path diversity disclosed in, for example, "Spread Spectrum Communication System" by Mitsuo Yokoyama, Science and Technology Publishing Company (1988).
cisionIntegrator) 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 1 symbol time TS
Delay circuit for delaying the correlator output only by 3, delay circuit 2
The multiplier 4 which multiplies the output of the correlator 1 and the output of the correlator 1 delayed by 4 is the time when the delayed wave exists (delay spread)
An integrator that integrates the output of the multiplier 3 by TM and a data determiner 5 that determines the output of the integrator 4.

Next, the operation will be described. PDI in Figure 3
The direct spread / spread spectrum receiver receives the direct spread / spread spectrum signal, performs frequency conversion, band limitation, etc., and then inputs the received signal to the correlator 1. The correlator 1 uses the received signal and the same spreading code used for spread spectrum on the transmitter side to perform direct spread / despread of the spread spectrum signal (correlation processing). An example of the correlation waveform after despreading is shown in FIGS. 4 (a) and 4 (b). Here, FIG. 4A is a diagram showing an example of a correlation waveform in the absence of a delayed wave due to multiple propagation paths (multipaths), and FIG. 4B is a diagram of the correlation waveform in the presence of a delayed wave. It is a figure which shows an example.

In FIG. 4A, 101 and 102 represent the correlation peaks of the preceding wave, and the horizontal axis 103 is the time axis and 10
Reference numerals 4 and 105 denote a real number axis and an imaginary number axis that represent the phase of the received signal. The above correlation peak interval is one information symbol time T
It is S. Further, 106 and 107 in FIG. 4B are correlation peaks of the delayed wave of the preceding wave 101 generated by the multiple propagation paths (multipaths). Similarly, 108 and 109 are correlation peaks of the delayed wave due to the preceding wave 102. Let TM be the time from the correlation peak of the preceding wave to the correlation peak of the delayed wave having the longest delay. The phase difference between the correlation waveforms 106 and 108 of the delayed wave and similar 107 and 109 is substantially equal to the phase difference between the correlation peaks 101 and 102 of the preceding wave.

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 and the correlation waveform delayed by TS by the delay circuit 2. (Delayed detection). As a result, at the output of the multiplier 3, a signal corresponding to the phase difference between two correlation waveforms that differ by one information symbol time is obtained. 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 receiving apparatus that performs only differential detection without using ordinary PDI, the correlation peaks 101, 10 of the preceding wave are generated.
Data determination is performed by the data determiner 5 using the phase difference of 2.

In the integrator 4, by integrating the output of the multiplier for the time TM, the signal corresponding to the phase difference between the preceding waves 101 and 102 temporally dispersed by the delay spread due to the multiple propagation paths, and the preceding wave Signals corresponding to the phase difference between the delayed waves 106 and 108 and 107 and 109 having a delay time of TM or less are integrated (synthesized). The output of this integrator 4 is judged by the data judging device 5, and the judgment result is output.
As a result, 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), whereas in PDI, a plurality of correlation waveforms ( Since the phase difference between the correlation waveform of the preceding wave and the delayed wave) is integrated (combined), and the judgment is made using the combined result,
Diversity gain is obtained when a delayed wave is present.

The influence of the odd correlation in the conventional direct spread spectrum / spread spectrum receiver constructed as above will be described below. For example, a 7-chip PN sequence (-1, -1, + 1, + 1, + 1, -1, + 1) is used as the spreading code of the direct spread / spread spectrum communication system, and after the differential coding, For transmission information 1, this spreading code is transmitted as is,
With respect to the transmission information 0 after differential encoding, it is assumed that the spread spectrum is performed by inverting and transmitting +1 and -1 of this spreading code (when performing differential detection on the receiving side, normally,
Differential encoding is performed on the transmission side). When the transmission information of 1, 1, 1 is spread-modulated using the above PN sequence,
The transmitted 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, +) as that used on the transmitting side is received.
The correlation waveform when the correlation processing is performed in 1) is shown in FIG. In the figure, 110, 111 and 112 are peaks (correlation peaks) of the correlation waveform, and the positive / negative of the peak value corresponds to 1, 0 of the transmission information. On the other hand, when 1,0,1 is used as the transmission information, the spread-modulated transmission signal becomes (-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,
Spreading code (-1, -1, + 1, + 1,
The correlation waveform when the correlation processing is performed with + 1, -1, + 1) is shown in FIG. 5B. In the latter case, the correlation waveform has points 113, 114, other than the peaks 110, 111, 112,
It can be seen that there are large fluctuations at 115 and 116. This variation is the effect of odd correlation, the shape and magnitude of this variation is unique to each spreading sequence, and
This variation may or may not occur depending on the transmitted information.

[0009]

In the conventional direct-spread / spread-spectrum receiver configured as described above, the correlation waveform has the original preceding wave and delayed wave due to the influence of the odd correlation of the correlator output. It fluctuates except the time. This fluctuation 1
13, 114, 115 and 116 can be regarded as equivalent to noise in the direct spread / spread spectrum communication system. PDI
In the receiver, since the integrator 4 integrates (combines) the phase difference of the correlation waveform that is equivalent to such noise and the phase difference other than the peak of the correlation waveform that can be regarded as equivalent to the noise, the correlation waveform There was a problem that the diversity gain deteriorates compared to the ideal diversity that combines only the phase difference of the peak of.

The present invention has been made to solve the above problems, and even when the phase difference of the correlation waveform due to the odd correlation fluctuates, the fluctuation of the correlation waveform due to the odd correlation is removed by the canceller, and reception is performed. It is an object of the present invention to obtain a direct spread / spread spectrum receiver that prevents deterioration of characteristics.

[0011]

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 output of the correlator. And a multiplier that multiplies the output of the delay circuit and the correlator, a propagation path detection unit that detects a preceding wave and a delayed wave from the output of the multiplier, and a preceding wave and a delayed wave that are detected by the propagation path detection unit. In a direct spread spectrum spread spectrum receiver having a circuit for removing the noise component of the multiplier output and an integrator for integrating the output, and configured to perform path diversity, the determination result of the receiver is used. ,
This is provided with an odd correlation canceller that cancels the influence of the odd correlation component of the correlator output.

[0012]

In the direct spread / spread spectrum receiver configured as described above, it is detected whether or not the correlation waveform is changed due to the influence of the odd correlation by using the determination result, and if it is changed, By removing the fluctuation of the correlation waveform and using the correlation waveform from which the fluctuation is removed, it is possible to prevent the deterioration of the diversity gain due to the influence of the odd correlation.

[0013]

EXAMPLES Example 1. 1 is a block diagram showing the configuration of a direct spread / spread spectrum receiver according to a first embodiment of the present invention. In the figure, 7 is a correlator for despreading the received signal,
Reference numerals 6a and 6b denote in-phase and quadrature channel differential detection units, and differential detection unit outputs 10 and 11 are input to a propagation path detection unit 17 with a compensation circuit. The output 18 of the propagation path detecting unit with a compensation circuit is input to the multipliers 9a and 9b and 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 determiner 5. The determination result is also input to the propagation path detection unit 17 with a compensation circuit. In this embodiment, the modulation method is QP.
Since the case where quadrature modulation such as SK is used is described as an example, the correlator 7 is for a quadrature modulation / demodulation system.
The differential detection units 6a and 6b, the integrators 4a and 4b, and the like use two systems for the in-phase channel and the quadrature channel.

FIG. 2 is a block diagram showing an internal configuration of the propagation path detecting unit 17 with a compensation circuit shown in FIG. In the figure, 13a and 13b are squarers for squaring the output signals of the differential detection units 6a and 6b, 14 is an adder for adding the outputs of the in-phase channel and quadrature channel squarers 13a and 13b, and 20.
Is a delay circuit that delays the output of the adder 14, and 21 is an odd correlation canceller that cancels 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 is a cyclic adder, and 16 is a determination circuit that outputs 1 when the cyclic addition result of 15 exceeds a predetermined threshold value, and outputs 0 otherwise.

The operation of the direct spread / spread spectrum receiver configured as above will be described. The received signal is subjected to despreading (correlation processing) by the correlator 7 and delay-detected by the delay detection units 6a and 6b. As a result, signals corresponding to the phase difference of the correlation waveform of the time difference of 1 symbol are obtained at the outputs of the differential detection units 6a and 6b. further,
From the outputs of the delay detectors 6a and 6b, the squarer 13
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 calculated by the delay circuit 20 by the integrators 4a and 4a.
b and a time corresponding to the processing time of the data determiner 5 are delayed.

In the odd correlation canceller 21, the data determiner 5
From the determination result of the transmission information obtained in step 1, it is estimated whether or not the correlation waveform is changed due to the odd correlation. Since the presence / absence of a change in the correlation waveform due to the odd correlation is determined by the transmission information, the presence / absence of a 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 of the preceding wave and the delayed wave is used by using the position information of the preceding wave and the delayed wave obtained by the determination circuit 16. Cancel. The shape of the fluctuation 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 in which the influence of the odd correlation is canceled by the odd correlation canceller 21 is cyclically added by the cyclic adder 15, the peak of the correlation waveform is emphasized, and noise components other than the phase difference of the peak of the correlation waveform are suppressed.

The determination circuit 16 detects the position of the delayed wave by determining whether or not the cyclic addition result exceeds a preset threshold value, and when the delayed wave exists, 1 is used as a weighting coefficient. Is output, and 0 is output otherwise. By multiplying the outputs of the differential detection units 6a and 6b by the multipliers 9a and 9b by this weighting coefficient, only the phase difference components of the correlation waveforms of the preceding wave and the delayed wave are integrators 4a and 4b.
To the integrator 4 and the other noise components are not supplied to the integrator 4. As a result, in the integrators 4a and 4b, only the phase difference between the peaks (correlation peaks) of the correlation waveform is integrated (synthesized), and the noise component such as the variation of the correlation waveform due to the influence of the odd correlation is not integrated, so that the diversity gain is deteriorated. Can be prevented.

In the direct-spread / spread-spectrum receiver configured as described above, the variation of the correlation waveform due to the influence of the odd correlation is removed by the odd correlation canceller. Therefore, it is possible to prevent the variation of the correlation waveform due to the influence of the odd correlation from being integrated, and it is possible to prevent the deterioration of the diversity gain.

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

In the first embodiment, 1 and 0 are used as the weighting coefficients, but other coefficients may be used.

Further, although the cyclic adder is used for suppressing the noise component in the first embodiment, the same applies when a moving average is used instead.

The same effect can be obtained even when the positions of the preceding wave and the delayed wave are detected without using noise suppressing means such as cyclic addition and moving average.

Further, the delay circuit 20 is used for compensating the processing delay of the integrator 4, the data judging device 5, etc. If this processing delay is compensated, it is delayed 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. The propagation path detection unit with the compensation circuit removes the variation of the phase difference of the correlation waveform due to the odd correlation, so that the propagation path can be accurately detected, and the deterioration of the diversity gain can be prevented. Can be obtained.

[Brief description of drawings]

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

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

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 correlation waveforms for explaining the operation of a conventional PDI direct spread / spread spectrum receiver.

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

[Explanation of symbols]

 1 Correlator 2 Delay circuit 3 Multiplier 4 Integrator 5 Data decision device 6a, 6b Delay detection part 7 Quadrature modulation correlator 9a, 9b Multiplier 10 In-phase channel signal path 11 Quadrature 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 Variation 114 Variation of correlation waveform due to odd correlation 115 Odd phase Fluctuation of correlation waveform due to function 116 Fluctuation of correlation waveform due to odd correlation

Claims (1)

[Claims] 1. A correlator for despreading a received signal, a delay circuit for delaying the output of the correlator, a multiplier for multiplying the output of the delay circuit by the output of the correlator, and a preceding wave from the output of the multiplier. A path diversity unit that has a propagation path detection unit that detects delayed waves, a circuit that removes the noise component of the multiplier output by using the preceding wave and the delayed wave detected by the propagation path detection unit, and an integrator that integrates the output In a direct spread / spread spectrum receiver configured to perform the above, a spread spectrum receiver including an odd correlation canceller that cancels the influence of an odd correlation component of the correlator output by using the determination result of the receiver. ..