JPH0865202A - Spread spectrum signal receiver - Google Patents

Abstract

(57) [Abstract] [Purpose] To enable stable demodulation of data even when the amplitude of the differential detection signal waveform changes due to fluctuations in the received electric field strength. A correlator 2 despreads a spread spectrum modulation signal and outputs a correlation signal, and a delay detection means composed of a delay line 3 and a multiplier 4 delays and detects a signal from the correlator 2 and a low-pass filter 5 The differential detection signal output through the absolute value circuit 7 that outputs the absolute value, the peak value hold circuit 8 that detects and outputs the peak value for the input from the absolute value circuit 7, and the peak value. A threshold level generator 6 including an arithmetic circuit 9 that calculates a predetermined level and outputs a signal with respect to the input from the hold circuit 8.
Is provided to input the signal from the threshold level generation unit 6 to the data demodulation unit 10 so that the signal input by the data demodulation unit 10 is used as the threshold level to determine the delayed detection signal and demodulate and output the data. I am configuring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum signal receiver, and more particularly to a data demodulation circuit of a spread spectrum signal receiver for receiving a spread spectrum signal using a direct spread method.

[0002]

2. Description of the Related Art In a conventional data demodulation circuit of a spread spectrum signal receiving apparatus, as shown in FIG. 3, a spread spectrum signal obtained by extracting a signal band component of a signal received by a receiving section and converting it into an intermediate frequency signal. The modulation signal (SS input signal) is input to the input terminal 1, and the correlator 2 despreads the spread spectrum modulation signal input via the input terminal 1 to output a correlation signal, and the multiplier 4 performs correlation. The signal input from the correlator 2 and the signal input from the correlator 2 via the delay line 3 are multiplied and output as a differential detection signal as shown by the waveform a in FIG. 2, and the low pass filter (LPF) 5
Then, the high frequency components were removed and output. Hereinafter, the correlation signal waveform of the waveform a is shown as a triangular shape with its shape omitted. Further, the differential detection signal from the low-pass filter (LPF) 5 is input to the data demodulation unit 15, and the data demodulation unit 15 makes a determination based on a threshold level L0 of a predetermined level set in advance as shown by a waveform h in FIG. I was trying to demodulate the data.

[0003]

However, when the received electric field strength is weakened, the amplitude of the differential detection signal waveform is also shown in FIG.
Since it becomes smaller than the threshold level L0 as shown by the waveform i, there is a problem that the data cannot be demodulated at the threshold level L0 fixed to a predetermined level. According to the present invention, even if the received electric field strength fluctuates due to fading or the like, and the amplitude of the differential detection signal waveform changes, the threshold level is changed according to this change, so that data can be demodulated stably. It is an object of the present invention to provide a spread spectrum signal reception device that can be used.

[0004]

A spread spectrum signal receiving apparatus according to a first aspect of the present invention includes a correlating means for despreading a received spread spectrum modulated signal and outputting a correlation signal, and a signal from the correlating means. A delay detection means for multiplying the delayed signal with the delayed detection signal to output, and a delay detection signal output from this delay detection means through a low-pass filter is judged at a predetermined threshold level to demodulate data. In a spread spectrum receiving device comprising a data demodulating means for outputting, a threshold level generating section for outputting a signal in accordance with the amplitude level of the differential detection signal output through the low pass filter is provided, and from this threshold level generating section Signal is input to the data demodulation means, and the signal input by the data demodulation means is input to the threshold Characterized by delay detection signal discriminated to demodulate the data output as Le.

Further, in the spread spectrum signal receiving apparatus of the second invention of the present application, the threshold level generating section is
With respect to the differential detection output input through the low-pass filter, an absolute value circuit that takes an absolute value and outputs it, and a peak value hold circuit that detects and outputs a peak value for the input from this absolute value circuit, An arithmetic circuit for arithmetically operating a predetermined level with respect to the input from the peak value hold circuit and outputting a signal is provided. Further, the spread spectrum signal receiving apparatus of the third invention of the present application is characterized in that the arithmetic circuit calculates one half of the peak value inputted from the peak value holding circuit and outputs the signal. .

[0006]

As described above, the present invention has an absolute value circuit that outputs an absolute value of a differential detection signal output through a low-pass filter, and a peak of the signal amplitude with respect to the input from this absolute value circuit. A threshold level generation unit is provided that includes a peak value hold circuit that detects and outputs a value and an operation circuit that calculates a predetermined level for the input from this peak value hold circuit and outputs a signal. The signal from the circuit is input to the data demodulation means, and the signal input by the data demodulation means is used as the threshold level to discriminate the delayed detection signal and demodulate the data. Even if fluctuations occur and the amplitude of the differential detection signal waveform decreases,
Since the threshold level can be changed according to the peak value of the amplitude, the data can be demodulated stably.

[0007]

1 is a block diagram showing an embodiment of a spread spectrum signal receiving apparatus of the present invention. In the figure, the same parts as those shown in FIG. 3 are designated by the same reference numerals. FIG. 2 is a waveform diagram for explaining the operation of each part of FIG. 1, and an embodiment will be described below with reference to FIGS. 1 and 2. A spread spectrum modulation signal (SS input signal) obtained by extracting the signal band component of the signal received by the receiving unit and converting it into an intermediate frequency signal is input to the input terminal 1, and the correlator 2 is input via the input terminal 1. Entered in. For example, a SAW matched filter is used as the correlator 2, and when the spread spectrum modulation signal input matches the phase pattern preset in the SAW matched filter, the correlation detection signal having a peak for each data period is generated by the correlator 2 Is output from. Further, the spread spectrum modulation signal is obtained by subjecting digital data, which is an information signal, to two-phase phase modulation, and the peak phase of the correlation detection signal is inverted and output according to the phase of the digital data.

The correlation detection signal from the correlator 2 is branched and one of them is input to the multiplier 4 as it is, and the other is input to the delay line 3 by 1
The data is delayed and input to the multiplier 4, and both inputs are differentially detected by the multiplier 4. When the phases of the peak parts of both inputs are different, there is a peak on the negative side, and the peak part of both inputs If the phases are the same, the differential detection signal waveform a having a peak on the plus side is output from the multiplier 4. The waveform a is a signal corresponding to the digital signal [0101], and hereinafter, the correlation signal waveform of the waveform a is shown as a triangular shape with its shape omitted. A low-pass filter (LPF) 5 removes a high-frequency component from the output of the multiplier 4 and branches the output so that one is input to the threshold level generation unit 6 and the other is input to the data demodulation unit 10.

In the threshold level generator 6, the absolute value circuit 7 inverts the negative side peak signal to the positive side peak signal with respect to the input differential detection output and outputs it to the positive side. Only the waveform is converted into a waveform having a peak signal and input to the peak value hold circuit 8. The peak value hold circuit 8 detects and outputs the peak value in response to the input from the absolute value circuit 7 and inputs the peak value to the arithmetic circuit 9. In the arithmetic circuit 9, for example, the peak value 1 is calculated from the input peak value. The DC level signal (threshold level L1) shown in the waveform c which becomes / 2 is output and input to the data demodulation unit 10. In the data demodulation unit 10, as shown by the waveform e, the threshold level L is set with respect to the peak of the differential detection signal input from the low-pass filter (LPF) 5.
By making a judgment in 1, the [010
The data of the digital signal 1) can be demodulated and output.

For example, even if the received electric field strength fluctuates due to fading or the like, and the amplitude of the differential detection signal waveform becomes small, the arithmetic circuit 9 calculates a peak value from the input peak value as shown by the waveform d and obtains a peak Output a DC level signal (threshold level L2) that is half the value,
Data is input to the data demodulation unit 10, and the data demodulation unit 10 determines at the threshold level L2 with respect to the peak of the differential detection signal input from the low-pass filter (LPF) 5, as shown by the waveform f. Due to
Data can be demodulated and output as shown in the waveform g. Therefore, even if the amplitude of the differential detection signal waveform changes,
Since the threshold level generated by the threshold level generator 6 can be changed according to this change,
It is possible to stably demodulate the data.

[0011]

As described above, according to the present invention,
For the differential detection signal, the threshold level generator detects the peak value of the amplitude of the differential detection signal, changes the threshold level according to the peak value, and inputs it to the data demodulator. It becomes possible to distinguish the delay detection signal by changing the threshold level according to the peak value of the amplitude of the detection signal, and therefore, the fluctuation of the received electric field strength occurs and even if the amplitude of the delay detection signal waveform becomes small, A spread spectrum signal receiving device capable of stably demodulating data can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a spread spectrum signal receiving apparatus of the present invention.

FIG. 2 is a waveform diagram for explaining the operation of each unit in FIG.

FIG. 3 is a block diagram showing a conventional spread spectrum signal receiving apparatus.

FIG. 4 is a waveform diagram for explaining an operation of conventional data demodulation.

[Explanation of symbols]

 1 Input Terminal 2 Correlator 3 Delay Line 4 Multiplier 5 Low Pass Filter 6 Threshold Level Generator 7 Absolute Value Circuit 8 Peak Value Hold Circuit 9 Arithmetic Circuit 10 Data Demodulator 11 Output Terminal

Claims (3)

[Claims] 1. A differential detector that multiplies a signal from the correlator and a signal obtained by delaying the received signal by despreading the received spread spectrum modulation signal and outputting a correlated signal, and performs delayed detection to output the delayed signal. And a data demodulating means for demodulating and outputting data by judging at a predetermined threshold level with respect to the differential detection signal output from the differential detection means through the low-pass filter, and the low-pass filter A threshold level generation unit that outputs a signal according to the amplitude level of the differential detection signal output via is provided, and the signal from the threshold level generation unit is input to the data demodulation means, and the data demodulation means The feature is that the input signal is used as the threshold level to discriminate the differential detection signal, demodulate the data and output. Spread spectrum signal receiver. 2. An absolute value circuit for the threshold level generation unit to output an absolute value with respect to the differential detection output input through the low pass filter, and a peak value for the input from the absolute value circuit. 2. The spread spectrum signal receiving apparatus according to claim 1, comprising a peak value hold circuit for detecting and outputting the signal and an operation circuit for calculating a predetermined level and outputting a signal with respect to the input from the peak value hold circuit. 3. The spread spectrum signal receiving apparatus according to claim 2, wherein said arithmetic circuit calculates one half of the peak value input from said peak value holding circuit and outputs a signal.