JPH0865224A - Spread spectrum communication receiver - Google Patents

Abstract

PURPOSE: To facilitate synchronization acquisition and synchronization maintenance even when the reception signal power is small due to fluctuation by giving signals obtained from n-sets of antennas to n-sets of envelope detectors and summing outputs of the detectors so as to detect a correlation peak position. CONSTITUTION: The receiver is provided with receivers 2a, 2b receiving a signal subjected, to spread spectrum processing by antennas 1a, 1b through diversity, passive correlator 3a, 3b applying inverse spread spectrum processing to each output based on a sampling clock of a prescribed period, time window controllers 4a, 4b used to provide a time window through which a signal subjected to inverse spread processing passes, delay detectors 5a, 5b using the signal passing through the time window for demodulation, a diversity synthesizer 6 and a demodulator 7, and also with envelope detectors 8a, 8b respectively and an adder 17 adding the outputs of them. That is, the signal obtained from the antennas 1a, 1b are subjected to envelope detection and summed and a correlation peak position is detected from the sum output.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is used for receiving spread spectrum signals. In particular, the present invention relates to a receiver which is provided with a time window for removing noise from a spectrum despread signal and demodulates using a signal that has passed through the time window.
More specifically, it relates to synchronization acquisition and synchronization of spreading codes.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing a conventional spread spectrum communication receiver for diversity receiving a spread spectrum signal by a plurality of antennas and demodulating it.
This receiver includes receivers 2a and 2b to which antennas 1a and 1b are respectively connected, passive correlators 3a and 3b, time window controllers 4a and 4b, delay detectors 5a and 5b, a diversity combiner 6 and a demodulator 7. In addition, the envelope detector 8a, the peak position detector 9, the changeover switch 10, and the averaging device 1 are provided for the synchronization acquisition and the synchronization retention of the spread code.
6, time window center position memory 13, peak position comparator 1
1, and up / down counter 12.

Receiving devices 2a and 2b respectively perform quadrature detection on the received signal in the carrier band and output I and Q signals in the base band. The passive correlators 3a and 3b receive the output signals of the receiving devices 2a and 2b, respectively, and output the correlation value with the spread code. Time window controller 4a, 4b
Receives the output signals of the passive correlators 3a and 3b and outputs a signal that has passed through the time window. Delay detector 5a, 5b
Receives the output signals of the time window controllers 4a and 4b as input, and performs delay detection for each cycle of the spread code. The diversity combiner 6 receives the detection signals of the delay detectors 5a and 5b as input and performs diversity combining. The demodulator 7 demodulates the output of the diversity combiner 6.

The output signal of the passive correlator 3a is also branched and input to the envelope detector 8a for envelope detection.
The peak position detector 9 receives the output signal of the envelope detector 8a as an input, and detects the maximum peak position within one cycle of the spread code. The changeover switch 10 sends the output signal of the peak position detector 9 to the averager 16 in the initial mode. The averaging unit 16 averages the peak positions output from the peak position detector 9 over a plurality of cycles of the spread code, and stores them in the time window center position memory 13 as the first center position of the time window. The time window controllers 4a and 4b set the time window center position stored in the time window center position memory 13 as an initial value.

The oscillator 15 supplies the m frequency divider 14 with a signal having a frequency m times (m is an integer of 2 or more) the chip frequency of the spreading code (clock frequency of the code used for frequency spreading the data). To do. The m divider 14 generates a sampling clock by dividing the output signal of the oscillator 15 by m, and the passive correlators 3a and 3b and the time window controllers 4a and 4 are used.
b, the delay detectors 5a and 5b, and the peak position detector 9
Supply to.

On the other hand, the change-over switch 10 outputs the output signal of the peak position detector 9 to the peak position comparator 11 in the steady mode. The peak position comparator 11 compares the peak position output from the peak position detector 9 with the time window center position stored in the time window center position memory 13, and up / down counters a value according to the comparison result. Send to 12. The up / down counter 12 adds the output values of the peak position comparator 11, and when the counter value exceeds the threshold value, sends out a shift signal for instructing the shift of the phase of the sampling clock to the m frequency divider 14. ,
Reset the counter value. The m frequency divider 14 temporarily changes the frequency division number in accordance with the shift signal from the up / down counter 12 and shifts the phase of the sampling clock.

As described above, the spread spectrum communication receiver has an initial mode and a steady mode in its operation, and operates differently. In the initial mode,
Since no time window is set in the time window controllers 4a and 4b, control using the time window is not performed. At this time, in the envelope detector 8a, the peak position detector 9, the averaging device 16 and the time window center position memory 13, the time window controllers 4a and 4b.
The center position of the time window set as the initial value is detected and the time windows are set in the time window controllers 4a and 4b. In the steady mode, the envelope detector 8a, the peak position detector 9, the averaging device 16, the time window center position memory 13, the peak position comparator 1
1 and the up / down counter 12 minimize the difference between the peak position (output of the peak position detector 9) and the center position of the time window (stored value in the time window center position memory 13) within one cycle of the spread code. Control. At this time, the time window controller 4a, 4b does not control the time window until the synchronization acquisition is completed, and after the synchronization acquisition is completed, the time window controller 4a, 4b is operated to use the time window. Take control.

That is, the peak position comparator 11 outputs "+1" when the peak position within one cycle of the spreading code is larger than the center position of the time window, and outputs "-1" when it is smaller.
Is output, and the up / down counter 12 sequentially adds it. Here, when the count value of the up / down counter 12 exceeds the threshold value, the phase of the sampling clock is shifted by sending a shift signal instructing the deviation of the phase of the sampling clock to the m divider 14. The synchronization is acquired and the synchronization is held.

[0009]

However, in the conventional spread spectrum communication receiver, since the synchronization acquisition and the synchronization holding are performed using the signal obtained by one antenna, the received signal power may fluctuate due to the fluctuation of the received signal power. As the power decreases, an error may occur between the peak position detector value and the actual correlation peak position. Since this error causes an error in the value stored in the time window center position memory in the initial mode, it may be difficult to acquire synchronization. Further, even in the steady mode, an error occurs in the peak position comparator, and a phase error of the sampling clock in the m frequency divider occurs, so that it may be difficult to capture and hold the synchronization.

An object of the present invention is to solve the above problems and to provide a spread spectrum communication receiver which can easily perform synchronization acquisition and synchronization holding.

[0011]

A spread spectrum communication receiver according to the present invention is provided with a plurality of n receiving means for diversity receiving spread spectrum signals by different antennas, and a reception output of each of these receiving means in advance. A means for despreading the spectrum with a sampling clock of a predetermined period, a time window means for providing a time window through which these signals can pass for the despread spectrum of the n-series signal, and a means for passing the time window Demodulation means for demodulating using the generated signal, and synchronization means for controlling the phase of the sampling clock with respect to the center position of the time window, the synchronization means being a detection means for performing envelope detection of the spectrum despread signal. And a peak position detector for detecting the maximum peak position within one cycle of the spread code from the output signal of the detecting means. In the spread spectrum communication receiver including means for shifting the phase of the sampling clock so that the difference between the peak position and the center position of the time window is minimized, the detection means respectively detects n series signals. It is characterized by including n envelope detectors provided and an adder for adding the outputs of the n envelope detectors.

The signals before passing through the time window may be input to the n envelope detectors, but the signals after passing the time window may be input.

[0013]

The signals obtained from n antennas with integers of 2 or more are input to n separate envelope detectors, the output signals of these envelope detectors are added by the adder, and the adders of the adders are added. The peak position detector detects the correlation peak position from the output signal. Therefore, as compared with the case of performing the synchronization acquisition and the synchronization holding by the signal obtained from one antenna, even when the received signal power fluctuates and the power is small, the synchronization acquisition and the synchronization holding can be easily performed. .

[0014]

1 is a block diagram showing a spread spectrum communication receiver according to a first embodiment of the present invention. In this embodiment, the spread spectrum signals are separated into separate antennas 1a,
A plurality of n (n = 2 in this embodiment) receivers 2a and 2b for diversity reception by 1b and the respective reception outputs of the receivers 2a and 2b are subjected to spectrum despreading with a sampling clock having a predetermined cycle. The passive correlators 3a and 3b, the time window controllers 4a and 4b provided with time windows through which the signals of the n-sequential spectrum despread signals can pass, and the signals passed through these time windows Delay detectors 5a and 5b for performing demodulation using the diversity combiner 6 and demodulator 7
Further, in order to control the phase of the sampling clock with respect to the center position of the time window, the envelope detectors 8a and 8b and the adder 17 as envelope detecting means for envelope-detecting the spectrum despread signal. , A peak position detector 9 for detecting the maximum peak position within one cycle of the spread code from the output signal of the detecting means, and a sampling clock so that the difference between the peak position and the center position of the time window is minimized. A peak position comparator 11 and an up / down counter 12 for shifting the phase of Also,
An oscillator 15 and an m divider 14 are provided to generate a sampling clock, and an averaging unit 16 and a time window center position memory 13 are provided to initialize the center position of the time window.

The characteristic feature of this embodiment is that n
The number of envelope detectors 8a and 8b is provided for each of the n series of signals, and the adder 17 that adds the outputs of the n number of envelope detectors 8a and 8b is provided. Also,
In this embodiment, the envelope detectors 8a and 8b are respectively supplied with the signals that have passed through the time windows.

The receiving devices 2a and 2b, to which the antennas 1a and 1b are respectively connected, convert the frequency band of the received signal from the carrier band to the base band band. Receiving devices 2a, 2
The mutually orthogonal signals output by b are supplied to the passive correlators 3a and 3b, respectively.
Outputs the correlation value with the spread code. Passive correlators 3a, 3
The output signals of b are input to the time window controllers 4a and 4b, respectively, and the signals are output only while the time windows of the time window controllers 4a and 4b are open. The output signals of the time window controllers 4a and 4b are input to the delay detectors 5a and 5b, and these delay detectors 5a and 5b perform delay detection for each cycle of the spread code. The output signals of the delay detectors 5a and 5b are input to the diversity combiner 6 and are diversity combined. The output signal of the diversity combiner 6 is input to the demodulator 7 and demodulated.

The outputs of the time window controllers 4a and 4b are also branched and input to envelope detectors 8a and 8b, respectively.
The output signal is input to the adder 17 and added. The output signal of the adder 17 is input to the peak position detector 9,
The position of the maximum peak in one cycle of the spread code is detected. The output signal of the peak position detector 9 is a switch 1 whose output destination is switched between the initial mode and the steady mode.
0 is supplied.

When communication is started, the changeover switch 10 is set to the initial mode. In the initial mode, control by the time window controllers 4a and 4b is not performed, and the averaging unit 16 averages the output signal of the peak position detector 9 for a plurality of spreading code periods. The output of the averager 16 is stored in the time window center position memory 13 as the first position of the time window center position. The output signal of the time window center position memory 13 of the time window center position memory 13 is supplied to the time window controllers 4a and 4b, and the initial value of the center position of the time window is set.

After that, the changeover switch 10 is changed over to the steady mode. In the steady mode, the output of the peak position detector 9 is supplied to the peak position comparator 11. The peak position comparator 11 compares the output signal of the peak position detector 9 with the center position of the time window. If the output signal of the peak position detector 9 is larger than the center position of the time window, “+” is displayed.
1 ", and if smaller, outputs" -1 ". The output signals of the peak position comparator 11 are added by the up / down counter 12. When the counter value exceeds the threshold value, the up-down counter 12 sends a shift signal instructing the phase shift of the sampling clock to the m-frequency divider 14 and resets the counter value. m
The frequency divider 14 controls the phase of the sampling clock based on the output of the up / down counter 12 to minimize the difference between the center position of the time window and the peak position of the signal after despreading.

The output of the oscillator 15 having an oscillation frequency m times the chip frequency of the spread code is supplied to the m frequency divider 14. The output of the m-frequency divider 14 is supplied to the passive correlators 3a and 3b, the time window controllers 4a and 4b, the delay detectors 5a and 5b, and the peak position detector 9 as sampling clocks. The m frequency divider 14 also temporarily changes the frequency division number in accordance with the shift signal from the up / down counter 12 and shifts the phase of the sampling clock.

FIG. 2 is a block diagram showing a spread spectrum communication receiver according to the second embodiment of the present invention. This embodiment differs from the first embodiment in that the signals input to the envelope detectors 8a and 8b are spectrum despread signals before passing through the time window.

The receiving devices 2a and 2b, to which the antennas 1a and 1b are respectively connected, convert the frequency band of the received signal from the carrier band to the base band. Receiving devices 2a, 2
The mutually orthogonal signals output by b are supplied to the passive correlators 3a and 3b, respectively.
Outputs the correlation value with the spread code. Passive correlators 3a, 3
The output signals of b are input to the time window controllers 4a and 4b, respectively, and the signals are output only while the time windows of the time window controllers 4a and 4b are open. The output signals of the time window controllers 4a and 4b are input to the delay detectors 5a and 5b, and these delay detectors 5a and 5b perform delay detection for each cycle of the spread code. The output signals of the delay detectors 5a and 5b are input to the diversity combiner 6 and are diversity combined. The output signal of the diversity combiner 6 is input to the demodulator 7 and demodulated.

The outputs of the passive correlators 3a and 3b are also branched and input to the envelope detectors 8a and 8b, respectively, and the output signals thereof are input to the adder 17 and added. The output signal of the adder 17 is input to the peak position detector 9, and the position of the maximum peak in one cycle of the spread code is detected. The output signal of the peak position detector 9 is a changeover switch 10 whose output destination is switched between the initial mode and the steady mode.
Is supplied to.

When the communication is started, the changeover switch 10 is set to the initial mode. In the initial mode, control by the time window controllers 4a and 4b is not performed, and the averaging unit 16 averages the output signal of the peak position detector 9 for a plurality of spreading code periods. The output of the averager 16 is stored in the time window center position memory 13 as the first position of the time window center position. The output signal of the time window center position memory 13 of the time window center position memory 13 is supplied to the time window controllers 4a and 4b, and the initial value of the center position of the time window is set.

After that, the changeover switch 10 is changed over to the steady mode. In the steady mode, the output of the peak position detector 9 is supplied to the peak position comparator 11. The peak position comparator 11 compares the output signal of the peak position detector 9 with the center position of the time window. If the output signal of the peak position detector 9 is larger than the center position of the time window, “+” is displayed.
1 ", and if smaller, outputs" -1 ". The output signals of the peak position comparator 11 are added by the up / down counter 12. When the counter value exceeds the threshold value, the up / down counter 12 sends a shift signal instructing the shift of the phase of the sampling clock to the m frequency divider 14 and resets the counter value. m
The frequency divider 14 controls the phase of the sampling clock based on the output of the up / down counter 12 to minimize the difference between the center position of the time window and the peak position of the signal after despreading.

The output of the oscillator 15 having an oscillation frequency m times the chip frequency of the spread code is supplied to the m frequency divider 14. The output of the m-frequency divider 14 is supplied to the passive correlators 3a and 3b, the time window controllers 4a and 4b, the delay detectors 5a and 5b, and the peak position detector 9 as sampling clocks.

In the above embodiment, the passive correlators 3a,
A matched filter or a convolver may be used as 3b. Further, although the case where n = 2 is shown in the above embodiment, the present invention can be similarly implemented when n ≧ 3.

[0028]

As described above, the spread spectrum communication receiver of the present invention envelope-detects signals obtained from antennas of integer n of 2 or more and adds them together,
The correlation peak position is detected from the added output. As a result, compared to the case of using the signal obtained from one antenna,
Even if the received signal power is low due to fluctuations in the received signal power, synchronization acquisition and synchronization holding can be easily performed.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a spread spectrum communication receiver according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a conventional spread spectrum communication receiver.

[Explanation of symbols]

 1a, 1b Antenna 2a, 2b Receiver 3a, 3b Passive correlator 4a, 4b Time window controller 5a, 5b Delay detector 6 Diversity combiner 7 Demodulators 8a, 8b Envelope detector 9 Peak position detector 10 Changeover switch 11 peak position comparator 12 up / down counter 13 time window center position memory 14 m frequency divider 15 oscillator 16 averager 17 adder

Claims (2)

[Claims] 1. A plurality of n receiving means for diversity receiving spread spectrum signals by different antennas, and means for despreading the spectrum of each reception output of the receiving means with a sampling clock of a predetermined cycle. A time window means for providing a time window through which the despread spectrum despread signals can pass, a demodulation means for performing demodulation using the signal passing through the time window, and the time Synchronization means for controlling the phase of the sampling clock with respect to the center position of the window, wherein the synchronization means is a detection means for performing envelope detection of the spectrum despread signal, and a spreading code from the output signal of the detection means. A peak position detector for detecting the maximum peak position within one cycle of, and the peak position and the center position of the time window In a spread spectrum communication receiver including means for shifting the phase of the sampling clock so as to minimize the difference with the above, the detection means includes n envelopes respectively provided for the n series of signals. A spread spectrum communication receiver including a line detector and an adder for adding the outputs of the n envelope detectors. 2. The spread spectrum communication receiver according to claim 1, wherein the n envelope detectors are respectively input with n-series signals that have passed through a time window.