JP3244101B2 - Spread spectrum communication receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for receiving a spread spectrum signal. In particular, the present invention relates to a receiver for providing a time window for removing noise from a signal subjected to spectrum despreading and performing demodulation using a signal passing through the time window.
More specifically, the present invention relates to synchronization acquisition and synchronization maintenance of a spreading code.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing a conventional spread spectrum communication receiver for diversity receiving and demodulating a spread spectrum signal by a plurality of antennas.
This receiver comprises receiving devices 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. And an envelope detector 8 a, a peak position detector 9, a changeover switch 10, and an averager 1 for acquiring and maintaining synchronization of a spread code.
6. Time window center position memory 13, peak position comparator 1
1 and an up-down counter 12.

[0003] Receiving apparatuses 2a and 2b perform quadrature detection on a received signal in a carrier band and output an I signal and a Q signal in a baseband. The passive correlators 3a and 3b receive the output signals of the receiving devices 2a and 2b, respectively, and output a correlation value with a spreading code. Time window controllers 4a, 4b
Receives the output signals of the passive correlators 3a and 3b and outputs a signal that has passed through a time window. Delay detectors 5a, 5b
Receives the output signals of the time window controllers 4a and 4b and performs delay detection for each period of the spread code. The diversity combiner 6 performs diversity combining by using the detection signals of the delay detectors 5a and 5b as inputs. Demodulator 7 demodulates the output of diversity combiner 6.

[0004] The output signal of the passive correlator 3a is also branched and input to the envelope detector 8a, where it is subjected to envelope detection.
The peak position detector 9 receives the output signal of the envelope detector 8a as an input, and detects a peak position that is maximum 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 performs averaging over a plurality of periods of the spreading code for the peak position output from the peak position detector 9, and stores the result 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.

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

On the other hand, the changeover switch 10 outputs an 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 outputs a value corresponding to the comparison result to an up / down counter. 12 is sent. The up / down counter 12 adds the output value of the peak position comparator 11 and, when the counter value exceeds a threshold value, sends a shift signal instructing a shift of the phase of the sampling clock to the m frequency divider 14 and ,
Reset the counter value. The m frequency divider 14 temporarily changes the frequency division number according to the shift signal from the up / down counter 12, and shifts the phase of the sampling clock.

As described above, this spread spectrum communication receiver operates in an initial mode and a steady mode, 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 to be set as the initial value is detected, and the time window is set in the time window controllers 4a and 4b. In the stationary mode, the envelope detector 8a, the peak position detector 9, the averager 16, the time window center position memory 13, and the peak position comparator 1
1 and the up / down counter 12 such that the difference between the peak position (output of the peak position detector 9) and the center position of the time window (the value stored in the time window center position memory 13) within one cycle of the spread code is minimized. Control. At this time, the time window is not controlled by the time window controllers 4a and 4b until the synchronization acquisition is completed, and after the synchronization acquisition is completed, the time window controllers 4a and 4b are operated to use the time window. Perform control.

That is, the peak position comparator 11 outputs “+1” when the peak position within one period of the spread code is larger than the center position of the time window, and outputs “−1” when the peak position is smaller than the center position of the time window.
, And the up / down counter 12 sequentially adds this. Here, when the count value of the up / down counter 12 exceeds the threshold value, the phase of the sampling clock is shifted by transmitting a shift signal for instructing the shift of the phase of the sampling clock to the m frequency divider 14. The synchronization is acquired and the synchronization is maintained.

[0009]

However, in a conventional spread spectrum communication receiver, synchronization acquisition and synchronization are performed using a signal obtained from one antenna, and therefore, the reception signal is changed due to fluctuations in the reception signal power. As the power decreases, an error may occur between the value of the peak position detector 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 the synchronization. Further, even in the steady mode, an error occurs in the peak position comparator, and a phase error occurs in the sampling clock in the m frequency divider, so that it may be difficult to acquire and maintain synchronization.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a spread spectrum communication receiver capable of easily acquiring and maintaining synchronization.

[0011]

SUMMARY OF THE INVENTION A spread spectrum communication receiver according to the present invention comprises a plurality of n receiving means for diversity receiving spread spectrum signals by different antennas, and a receiving output of each of the receiving means. Means for performing spectrum despreading with a sampling clock having a predetermined period, time window means for providing a time window through which the spectrum despread n-sequence signals can pass, and passing the time window Demodulating means for performing demodulation using the obtained signal, and synchronizing means for controlling the phase of the sampling clock with respect to the center position of the time window, wherein the synchronizing means detects the envelope of the despread spectrum signal. And a peak position detector for detecting a maximum peak position within one cycle of the spread code from an output signal of the detection means. A 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. It is characterized by including n provided envelope detectors 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, or the signals passing through the time window may be input.

[0013]

A signal obtained from n integer antennas of 2 or more is input to n separate envelope detectors, and the output signals of these envelope detectors are added by an adder. A correlation peak position is detected from the output signal by a peak position detector. Therefore, as compared with the case where the synchronization acquisition and the synchronization holding are performed by the signal obtained from one antenna, even if 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. This embodiment combines the spread spectrum signals into separate antennas 1a,
1b, a plurality of n (n = 2 in this embodiment) receiving apparatuses 2a and 2b for diversity reception, and respective reception outputs of the receiving apparatuses 2a and 2b are spectrum despread by a sampling clock having a predetermined cycle. A passive correlator 3a, 3b, a time window controller 4a, 4b for providing a time window through which the spectrum despread n-sequence signal can pass, and a signal passing through the time window. Delay detectors 5a, 5b, diversity synthesizer 6, and demodulator 7 for performing demodulation using
In addition, in order to control the phase of the sampling clock with respect to the center position of the time window, envelope detectors 8a and 8b and an adder 17 as detection means for performing envelope detection of the spectrum-spread signal are provided. A peak position detector 9 for detecting the maximum peak position within one cycle of the spread code from the output signal of the detection means, and a sampling clock for minimizing the difference between this peak position and the center position of the time window. A peak position comparator 11 and an up / down counter 12 for shifting the phase of the signal. Also,
An oscillator 15 and an m frequency divider 14 are provided to generate a sampling clock, and an averager 16 and a time window center position memory 13 are provided to initialize the center position of the time window.

The feature of this embodiment is that n
That is, the number of envelope detectors 8a and 8b is provided for each of the n-sequence signals, and an adder 17 that adds the outputs of the n number of envelope detectors 8a and 8b is provided. Also,
In this embodiment, signals that have passed through a time window are input to the envelope detectors 8a and 8b, respectively.

The receivers 2a and 2b to which the antennas 1a and 1b are connected respectively convert the frequency band of the received signal from the carrier band to the baseband. Receiving devices 2a, 2
b output to the passive correlators 3a and 3b, respectively.
Outputs a correlation value with the spreading code. Passive correlators 3a, 3
The output signal b is input to the time window controllers 4a and 4b, respectively, and the signal is 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 the delay detectors 5a and 5b perform delay detection for each one cycle of the spreading code. The output signals of the delay detectors 5a and 5b are input to the diversity combiner 6, and are subjected to diversity combining. The output signal of the diversity synthesizer 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 the 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 period of the spreading code is detected. The output signal of the peak position detector 9 is provided by a changeover switch 1 whose output destination is switched between an initial mode and a steady mode.
0 is supplied.

When communication is started, the changeover switch 10 is set to the initial mode. In the initial mode, the 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 time window center position is set.

Thereafter, the changeover switch 10 is switched 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, and when the output signal of the peak position detector 9 is larger than the center position of the time window, “+”
1 is output, and if it is smaller, "-1" is output. The output signal of the peak position comparator 11 is added by the up / down counter 12. When the up / down counter 12 exceeds the threshold value, the up / down counter 12 sends a shift signal instructing a 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 despread signal.

The output of the oscillator 15 having an oscillation frequency that is m times the chip frequency of the spread code is supplied to an m frequency divider 14. The output of the m frequency divider 14 is supplied as a sampling clock to each of 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. The m frequency divider 14 also temporarily changes the frequency division number according to 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 a 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 the signals subjected to spectrum despreading before passing through the time window.

The receiving devices 2a and 2b to which the antennas 1a and 1b are connected respectively convert the frequency band of the received signal from the carrier band to the baseband. Receiving devices 2a, 2
b output to the passive correlators 3a and 3b, respectively.
Outputs a correlation value with the spreading code. Passive correlators 3a, 3
The output signal b is input to the time window controllers 4a and 4b, respectively, and the signal is 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 the delay detectors 5a and 5b perform delay detection for each one cycle of the spreading code. The output signals of the delay detectors 5a and 5b are input to the diversity combiner 6, and are subjected to diversity combining. The output signal of the diversity synthesizer 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 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 peak which is the maximum in one cycle of the spread code is detected. An output signal of the peak position detector 9 is changed by a changeover switch 10 for switching an output destination between an initial mode and a steady mode.
Supplied to

When communication is started, the changeover switch 10 is set to the initial mode. In the initial mode, the 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 time window center position is set.

Thereafter, the changeover switch 10 is switched 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, and when the output signal of the peak position detector 9 is larger than the center position of the time window, “+”
1 is output, and if it is smaller, "-1" is output. The output signal of the peak position comparator 11 is added by the up / down counter 12. When the up / down counter 12 exceeds the threshold value, the up / down counter 12 sends a shift signal instructing a 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 despread signal.

The output of the oscillator 15 having an oscillation frequency that is m times the chip frequency of the spreading code is supplied to the m frequency divider 14. The output of the m frequency divider 14 is supplied as a sampling clock to each of 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.

In the above embodiment, the passive correlator 3a,
As 3b, a matched filter may be used, or a convolver may be used. Further, in the above embodiment, the case where n = 2 is shown, but the present invention can be similarly carried out when n ≧ 3.

[0028]

As described above, the spread spectrum communication receiver of the present invention performs envelope detection on signals obtained from n or more integer n antennas and adds them to each other.
The correlation peak position is detected from the added output. As a result, compared to the case where a signal obtained from one antenna is used,
Even when the received signal power is small due to the fluctuation of the received signal power, synchronization acquisition and synchronization holding can be easily performed.

[Brief description of the 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 Demodulator 8a, 8b Envelope detector 9 Peak position detector 10 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

Continuation of front page (56) References JP-A-6-69907 (JP, A) JP-A-6-77948 (JP, A) JP-A-6-104834 (JP, A) JP-A-6-13988 (JP) , A) Yasuo Suzuki et al., B-427 After detection, Characteristic study of code synchronization supplementation experiment using RAKE reception time window control loop (TWCL), Proceedings of IEICE Spring Conference 1994, Japan , IEICE, March 10, 1994, 2-427 Yasuo Suzuki et al., B-355 DPSK K-detection code synchronization scheme for RAKE receivers, 1993 IEICE Autumn Meeting Proceedings 2, The Institute of Electronics, Information and Communication Engineers, Japan, August 15, 1993, 2-355 (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 7/08 H04B 1/707

Claims (2)

(57) [Claims] 1. A plurality of n receiving means for diversity receiving spread spectrum signals by different antennas, and means for spectrum despreading each reception output of the receiving means with a sampling clock having a predetermined cycle. Time window means for providing a time window through which signals can pass through the n-sequence signal despread spectrum; demodulation means for performing demodulation using the signal passed through the time window; Synchronizing means for controlling the phase of the sampling clock with respect to the center position of the window, wherein the synchronizing means comprises: detecting means for performing envelope detection on the spectrum-despread signal; and a spreading code from the output signal of the detecting means. A peak position detector for detecting a peak position which is maximum in one cycle of the above, and the peak position and the center position of the time window And a means for shifting the phase of the sampling clock so that the difference between the two signals is minimized. The detecting means comprises n envelopes provided for the n-sequence signal, respectively. A spread spectrum communication receiver comprising: a line detector; and an adder for adding outputs of the n envelope detectors. 2. The spread spectrum communication receiver according to claim 1, wherein n-sequence signals passing through a time window are input to said n envelope detectors.