JPH07321699A - Spread spectrum signal receiver - Google Patents

Abstract

PURPOSE:To reduce an error rate of communication data by allowing a data demodulation circuit of the spread spectrum signal receiver to eliminate noise included in the signal. CONSTITUTION:Comparators 7, 9 compare present positive and negative reference levels with a delay detection output and the comparison result is gate- processed to generate a clock signal and a multivibrator 12 generates a pulse signal with a width slightly smaller than a 1-bit data period of the clock signal. A multivibrator 13 generates a data discrimination pulse signal by which data are discriminated based on the pulse signal and the discrimination pulse signal is given to a flip-flop circuit 16, which discriminates the pulse signal from the comparator circuit 9 and latches the signal to provide an output of reproduction data from which noise is eliminated. Then a multivibrator 14 generates recovered data clock having a pulse width being a half of the 1-bit data period based on the pulse signal for data discrimination.

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 is 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 the correlation signal, and the multiplier 4 , The signal input from the correlator 2 and the signal input from the correlator 2 via the delay line 3 are multiplied, differentially detected and output, and a low pass filter (LPF) 5 removes high frequency components and an amplifier It is input to the comparator circuits 7 and 9 via 6.

FIG. 2 is an explanatory view showing signal waveforms of respective parts according to the prior art and the present invention. Letting a signal waveform output from the correlator 2 be a, the delay line 3 shows a spread spectrum modulated signal. Since it is delayed by one data period, the output waveform becomes b, and the comparator circuits 7 and 9
The signal waveform of the differentially detected signal input to is c, and the comparator circuit 7 compares the preset reference voltage VA input via the input terminal 8 with the input signal (waveform c) and exceeds the reference voltage VA. The signal (waveform d) corresponding to the period is output. Similarly, the comparator circuit 9 compares the preset reference voltage VB input via the input terminal 10 with the input signal (waveform c), and outputs the reference voltage VB. A signal (waveform e) corresponding to the following period is output. Gate circuit 11
Then, the output signals of the comparator circuits 7 and 9 are NORed, the reproduced data clock as shown in the waveform f is output from the output terminal 25, and the output (waveform e) from the comparator circuit 9 is input to the flip-flop circuit 26. Then, the input from the comparator circuit 9 is latched by the H level signal applied to the J and K input pins of the flip-flop circuit 26, and the reproduced data is output from the output terminal 27.

[0004]

However, if the received electric field strength is lowered due to an increase in communication distance or fading, or if an interfering radio wave is mixed, the CN is used.
The ratio decreases, and noise is mixed in the signals input to the comparator circuits 7 and 9 as shown by the waveform c, and the gate circuit 11 takes the NOR from the outputs from the comparator circuits 7 and 9 to generate the reproduction data clock. Therefore, the reproduced data clock containing noise is output as shown in the waveform f, and the flip-flop circuit 26
There is a problem in that noise is mixed in the reproduced data from, and therefore errors are frequently caused by noise and communication is hindered. It is an object of the present invention to eliminate noise mixed in a signal in a data demodulation circuit of a spread spectrum signal receiving device and reduce an error rate for communication data.

[0005]

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 by a delay detection signal and outputting the result, and a comparison means for comparing a signal input from the delay detection means through a low-pass filter with preset positive and negative reference levels. A gate circuit for gating the comparison results of the positive and negative reference levels of the comparing means and outputting a data clock; and a flip-flop for latching the comparison result of one of the reference levels of the comparing means and outputting reproduced data. In a spread spectrum receiver comprising a circuit, a pulse signal generating means for generating a pulse signal for data discrimination from the data clock. Provided, characterized in that allowed to output to input reproduced data into the flip-flop circuit a pulse signal generated by the pulse signal generating means as a latch enable signal. A spread spectrum signal receiving apparatus according to a second invention of the present application is the first multivibrator circuit which is non-retriggerable, in which the pulse signal generating means removes an erroneous clock included in a data clock input from the gate circuit. And a second multivibrator circuit for generating a pulse signal for data discrimination by an input from the first multivibrator circuit.

In the spread spectrum signal receiving apparatus of the third invention of the present application, the output pulse width of the first multivibrator circuit is set to be slightly smaller than the 1-bit data period, and the output pulse of the second multivibrator circuit is set. The width is characterized in that the pulse signal generated as a result of comparison with one of the reference levels of the comparison means has a pulse width of a size capable of latching. A spread spectrum signal receiving apparatus according to a fourth invention of the present application is provided with a third multivibrator circuit for generating a pulse signal having a pulse width half that of a 1-bit data period, and the third multivibrator circuit is provided with the second multivibrator circuit. It is characterized in that the pulse signal of the multivibrator circuit is inputted and the reproduced data clock is outputted from the third multivibrator circuit.

[0007]

As described above, the present invention compares the positive and negative reference levels preset by the comparison means with the differential detection output inputted through the low pass filter, and gates the comparison result to obtain the clock signal. The clock signal is generated and input to the first multivibrator, and the first multivibrator generates a pulse signal having a width slightly smaller than the 1-bit data period of the clock signal. The pulse signal is input to the multivibrator, and a pulse signal having a data discriminating period having a minimum width and a size capable of discriminating data by the second multivibrator is generated and input to the flip-flop circuit. In this flip-flop circuit, Generated according to the result of comparison with one of the reference levels of the comparison means during the data discrimination period of the input pulse signal. And so as to determine the pulse signal and outputs the latches, therefore, it is possible to output the reproduced data to remove noise. Furthermore, the second
The pulse signal from the multi-vibrator of is input to the third multi-vibrator, and the third multi-vibrator outputs 1
A pulse signal having a pulse width that is half the bit data period is generated, and by outputting this pulse signal as a reproduction data clock, a stable reproduction data clock without noise can be output. Therefore, the reproduced data and the reproduced data clock without noise can be output, and the error rate for the communication data can be reduced.

[0008]

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 an explanatory diagram showing signal waveforms of respective parts according to the related art and the present invention. Examples 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 for the correlator 2,
When the spread spectrum modulation signal input matches the phase pattern preset in the SAW matched filter,
As shown by the waveform a in FIG. 2, a correlation detection signal having a peak for each data period is output from the correlator 2. 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 (waveform a) from the correlator 2 is branched, one of which is input to the multiplier 4 as it is, and the other of which is delayed by the delay line 3 for one data period to form the waveform b of the multiplier 4.
When the phases of the peak portions of the waveform a and the waveform b are different, the peaks are on the negative side, and the phases of the peak portions of the waveform a and the waveform b are input. , The differential detection signal having a peak on the plus side is output from the multiplier 4. The output from the multiplier 4 has its high-frequency component removed by a low-pass filter (LPF) 5, amplified by an amplifier 6, and then input to the comparator circuits 7 and 9 as a waveform c. The comparator circuit 7 compares the preset reference voltage VA input via the input terminal 8 with the input signal (waveform c) to obtain the reference voltage VA.
A signal (waveform d) corresponding to the period exceeding the output voltage. Similarly, in the comparator circuit 9, the preset reference voltage VB input through the input terminal 10 and the input signal (waveform c) are output.
Are compared with each other, and a signal (waveform e) corresponding to a period equal to or lower than the reference voltage VB is output.

When the received electric field strength is lowered due to an increase in communication distance or fading, or when an interfering radio wave is mixed, the CN ratio is lowered, and when the received signal contains noise, the waveform d and the The waveform e is also demodulated with noise components mixed therein. The outputs from the comparator circuits 7 and 9 are input to the gate circuit 11, and the gate circuit 11 takes the NOR of both inputs and inverts and outputs it, thereby outputting a clock signal as shown in the waveform f and outputting the multivibrator 12 Are typing in. As the multivibrator 12, a monostable multivibrator that cannot be re-triggered is used, and it is triggered at the falling edge of the clock signal (waveform f) to
A pulse signal (waveform g) having a maximum (slightly smaller) pulse width in a range smaller than the data period is generated.

Since the multivibrator 12 cannot be re-triggered, it can be triggered only by the clock signal of the waveform f and is not triggered by noise, so that a pulse signal containing no noise is generated as shown in the waveform g. be able to. The pulse signal (waveform g) generated by the multivibrator 12 is input to the multivibrator 13, and the multivibrator 13 also uses a monostable multivibrator, and is triggered by the trailing edge of the pulse signal (waveform g). The JK flip-flop circuit 16 is generated by generating a pulse signal (waveform h) that has a pulse width that is as small as possible and that can be discriminated.
It is input to the J and K input pins as a latch enable signal.

Cp of the JK type flip-flop circuit 16
The signal (waveform e) from the comparator circuit 9 is input to the input pin.
Is input, the falling edge of the signal (waveform e) is latched during the H level period of the pulse signal (waveform h) input to the J and K input pins, and the waveform i is output as reproduction data.
It outputs from 7. The flip-flop circuit 16 toggles only during the data determination period (H level period) of the pulse signal (waveform h), and the pulse signal (waveform h)
Is held at the L level, and the signal (waveform e) from the comparator circuit 9 is input, the flip-flop circuit when the phase of the spread spectrum modulation signal is inverted. A signal is output from 16.

In the waveform i, the L level period corresponds to "0" of the digital signal and the H level period corresponds to "1" of the digital signal. Therefore, it is possible to remove the noise included in the portion other than the data discrimination period (H level period) and output the reproduced data, and it is possible to remove the noise mixed in the spread spectrum signal. When an up-edge operation type JK flip-flop circuit 16 is used, a pulse signal (waveform h) having a data determination period (H level period) that allows the rising edge of the signal (waveform e) to be latched. May be output from the multivibrator 13.

The pulse signal (waveform h) generated by the multivibrator 13 is input to the multivibrator 14, and the multivibrator 14 uses a monostable multivibrator that generates a pulse width of half of one data period. The multi-vibrator 14 generates a reproduction data clock (waveform j) by triggering at the trailing edge of the signal (waveform h) and outputs it from the output terminal 15. Since the pulse signal (waveform h) does not contain noise, a stable reproduced data clock (waveform j) without noise is output from the output terminal 15. Therefore, by processing the reproduction data output from the output terminal 17 using this reproduction data clock (waveform j), the error rate for the communication data can be reduced.

[0015]

As described above, according to the present invention,
A pulse signal for data discrimination that does not contain noise is generated by the clock signal generated based on the differential detection output, and the data of the spread spectrum signal generated by the comparison means is discriminated during the data discrimination period of this pulse signal. Therefore, it becomes possible to output the reproduction data from which the noise mixed in the spread spectrum signal is removed, and the reproduction data clock is generated by the multivibrator based on the pulse signal for data discrimination. Therefore, it is possible to output a stable recovered data clock without noise, remove the noise mixed in the demodulated signal, and provide a spread spectrum signal receiver that can reduce the error rate for communication data. be able to.

[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 an explanatory diagram showing a signal waveform of each part according to the related art and the present invention.

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

[Explanation of symbols]

 1 Input Terminal 2 Correlator 3 Delay Line 4 Multiplier 5 Low Pass Filter 6 Amplifier 7 Comparator Circuit 8 Input Terminal 9 Comparator Circuit 10 Input Terminal 11 Gate Circuit 12 Multivibrator 13 Multivibrator 14 Multivibrator 15 Output Terminal 16 Flip-Flop Circuit 17 Output Terminal

Claims (4)

[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. Means, comparing means for comparing a signal input from the differential detection means through a low-pass filter with preset positive and negative reference levels, and gate processing of comparison results of the positive and negative reference levels of the comparing means. In a spread spectrum receiving device including a gate circuit for outputting a data clock and a flip-flop circuit for latching the comparison result of one of the reference levels of the comparing means and outputting the reproduced data, a data discriminating device from the data clock is used. Pulse signal generating means for generating the pulse signal of the pulse signal is generated, and the pulse signal generated by the pulse signal generating means is latched. A spread spectrum signal receiving apparatus, wherein the spread signal is inputted as a cable signal to the flip-flop circuit to output reproduced data. 2. A first multivibrator circuit, in which the pulse signal generating means does not allow retrigger to remove an erroneous clock included in a data clock input from the gate circuit, and the first multivibrator circuit. Second, which generates pulse signal for data discrimination by input from
2. The spread spectrum signal receiving apparatus according to claim 1, which comprises the multivibrator circuit according to claim 1. 3. The output pulse width of the first multivibrator circuit is set to be slightly smaller than the 1-bit data period, and the output pulse width of the second multivibrator circuit is set to one reference level of the comparison means. The spread spectrum signal receiving apparatus according to claim 1 or 2, wherein the pulse signal generated by the comparison result with (1) has a pulse width of a latchable size. 4. A third multivibrator circuit for generating a pulse signal having a pulse width half the 1-bit data period is provided, and the third multivibrator circuit is provided with the second multivibrator circuit.
4. The spread spectrum signal receiving apparatus according to claim 1, wherein the pulse signal of the multivibrator circuit is input and the reproduced data clock is output from the third multivibrator circuit.