JPH0677948A - Synchronizing device for spread spectrum communication - Google Patents

Abstract

PURPOSE:To speedily acquire synchronism in an initial mode by detecting a correlative peak position from the sum of outputs from an envelope detector and defining it as the initial value of a time window center position. CONSTITUTION:In the initial mode, the sum of outputs from an envelope detector 6 at respective sampling points is calculated for the plural times of spread code cycles by using an adder 15 and a memory 16. Next, the output of the memory 16 to store this sum is inputted to a peak position detector 17, and the maximum value of sampling points is detected. The output of this detector 17 is stored in a time window center position memory 11 as the first position of the time window center position. For the output signal of the time window center position memory 11, an initial value for the center position of a time window is set by a time window controller 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to spread spectrum communication in which a despread signal is provided with a time window, delay detection is performed only on a signal that has passed through the time window, and demodulation is performed after the delay detection. The present invention relates to a receiver, and more particularly to a synchronizer that determines an initial value of the center position of the time window.

[0002]

2. Description of the Related Art FIG. 2 is a diagram for explaining spread spectrum communication. In FIG. 1A, 21 is a frequency spectrum of a transmission signal, 22 is a frequency spectrum after spreading, 23 is a spreader, 24 is a transmitter, 25 is a transmitting antenna, 26 is a receiving antenna, 27 is a receiver, and 28 is Despreader, 29 is the frequency spectrum of the received signal, and 30 is the frequency spectrum of the received signal after despreading.

In the spread spectrum communication, as shown in FIG. 1, a signal to be transmitted is spread on the transmitting side by spreading the frequency band with a spreading code, and the receiving side uses the same spreading code as the transmitting side to reverse the signal. It is a communication method that spreads and demodulates data.

Since the spread spectrum communication system adopts such a configuration, it has characteristics such as strong noise resistance and confidentiality, but on the other hand, it is difficult to establish synchronization on the receiving side. There is also a disadvantage.

On the other hand, in the mobile communication system, since the propagation path is generally a multipath propagation path, signals arrive at the receiver with different delay times. When a matched filter is used for despreading in a propagation path in which such a delayed wave exists, the output of the matched filter becomes as shown in FIG. 2 (b).

FIG. 3 is a diagram showing an example of the configuration of a conventional receiver for spread spectrum communication. 1 is a passive correlator, 2 is a time window controller, 3 is a delay detector, 4 is a diversity combiner, 5 is a decoder, 6 is an envelope detector, 7 is a peak position counter, 8 is a changeover switch, 9 is a peak position comparator, 10 is an up / down counter, 11 is a time window center position memory, and 12 is frequency division by n. , 13 is an oscillator, and 14 is an averager.

The operation will be described below with reference to FIG. The orthogonal I signal and Q signal are input to the passive correlator 1, and the correlation value with the spreading code is output from the passive correlator 1. The output signal of the passive correlator 1 is output only while the time window is open in the time window controller 2.

The output signal of the time window controller 2 is subjected to delay detection in the delay detector 3 for each spreading period,
The diversity combiner 4 performs diversity combining on the output signal of the differential detector 3. The output signal of the diversity combiner 4 is input to the decoder 5 and decoded.

On the other hand, the output of the passive correlator 1 is also input to the envelope detector 6 and, after envelope detection is performed,
The output signal of the envelope detector 6 is the peak position counter 7
The position of the maximum peak in the cycle of the spread code is detected. The output signal of the peak position counter 7 is connected to the switch 8 for switching to the initial mode or the steady mode. Then, first, when the communication is started, the changeover switch 8 is set to the initial mode.

In the initial mode, the averaging unit 14 averages the output signal of the peak position counter 7. The output signal of the averager 14 is stored in the time window center position memory 11 as the first position of the time window center position. The output signal of the time window center position memory 11 is input to the time window controller 2 and the initial value of the center position of the time window is set. Next, the changeover switch 8 is changed over to the steady mode.

In the steady mode, the peak position comparator 9 compares the output signal of the peak position counter 7 with the center position of the time window, and the output signal of the peak position counter 7 is larger than the center position of the time window. If +1
If it is smaller, -1 is output. The output signal of the peak position comparator 9 is input to the up / down counter 10 and added.

When the count value of the up / down counter 10 exceeds the threshold value, a shift signal instructing the phase shift of the sampling clock is sent to the n frequency divider 12 and the up / down counter 10 The counter value of is reset.

The output signal of the oscillator 13 having a frequency n times the frequency of the spread code is supplied to the n frequency divider 12, and the output of the n frequency divider 12 is the passive correlator 1 and the time window controller 2. The timings of the differential detection wave 3, the diversity combiner 4, the envelope wave detector 6, and the peak position counter 7 are controlled.

[0014]

In the conventional receiver for spread spectrum communication as described above, since the averager 14 averages the positions where the output of the envelope detector is maximum within the period of the spread code, noise is generated. Below, an error easily occurs between the initial value of the time window center position memory 11 and the actual correlation peak position. Therefore, there is a drawback that it takes time to establish synchronization.

The present invention has been made in order to solve such a conventional problem, and an object thereof is to provide an apparatus capable of quickly establishing synchronization in the initial mode.

[0016]

According to the present invention, as described in the claims, a time window is provided for a despread signal, and post-detection demodulation is performed only for a signal passing through the time window. In a receiver for spread spectrum communication, an adder for inputting a signal obtained by envelope detection of a signal after despreading and adding the input and the contents of the memory, and a memory connected to the adder and storing the addition result A peak position detector that detects a sampling point having a maximum value from the output signal of the memory, a time window center position memory that stores the output of the peak position detector, and the contents of the time window center position memory. It is a synchronizer for spread spectrum communication, which comprises a path for transmitting to a means for controlling a time window as an initial value of a center position of the window.

[0017]

In the present invention, in the initial mode, the output of the envelope detector is added for each sampling position during the spread code period, and the correlation peak position is detected from the sum of the outputs of the envelope detector for each sampling position. Since the initial value of the center position of the time window is used as the initial value, an accurate initial value of the center position of the time window can be obtained. Hereinafter, the operation and the like of the present invention will be described in detail based on Examples.

[0018]

FIG. 1 is a diagram showing an embodiment of the present invention. In the figure, the same parts as those in FIG. 3 described above are designated by the same reference numerals. In addition, 15 is an adder, 16 is a memory, and 17 is a peak position detector.

In the figure, orthogonal I and Q signals are input to the passive correlator 1, and the correlation value with the spreading code is output from the passive correlator 1. The output signal of the passive correlator 1 is input to the time window controller 2, and the signal is output from the time window controller 2 only while the time window is open. The output signal of the time window controller 2 is subjected to delay detection in the delay detector 3 for each spreading period, and the output signal of the delay detector 3 is subjected to diversity combining in the diversity combiner 4. The output signal of the diversity combiner 4 is input to the decoder 5 and decoded.

On the other hand, the output of the passive correlator 1 is also input to the envelope detector 6, and the output signal of the envelope detector 6 is connected to the switch 8 for switching to the initial mode or the steady mode. . First, when communication is started, the changeover switch 8 is set to the initial mode, the initial values of the memory 16 are all 0, and the pointer indicating the address is 0. In the initial mode, the output of the envelope detector 6 is input to the adder 15 for each sampling point during one spreading code period.

In the adder 15, the output of the envelope detector 6 and the contents of the memory 16 are summed and stored in the same memory, and the pointer of the memory 16 is incremented by 1. Then, the pointer of the memory 16 is returned to 0 when one spread code period has passed. By performing this operation for a plurality of cycles, the sum for each sampling point of the envelope detector 6 can be obtained from the output of the memory 16.

The output of the memory 16 is input to the peak position detector 17 to detect the maximum value of the sampling points.
The output of the peak position detector 17 is stored in the time window center position memory 11 as the first position of the time window center position.
The output signal of the time window center position memory 11 is input to the time window controller 2 and the initial value of the center position of the time window is set.

Next, the changeover switch 8 is changed over to the steady mode. In the steady mode, the output signal of the envelope detector 6 is input to the peak position counter 7 and the position of the maximum peak in the code period is detected. The peak position comparator 9 compares the output signal of the peak position counter 7 with the center position of the time window. If the output signal of the peak position counter 7 is larger than the center position of the time window, +1 is obtained. Is output.

The output signal of the peak position comparator 9 is input to the up / down counter 10 and added. When the count value of the up / down counter 10 exceeds the threshold value, a shift signal instructing the phase shift of the sampling clock is sent to the n frequency divider 12 and the count value of the up / down counter 10 Is reset.

The output of the oscillator 13 having a frequency n times the frequency of the spread code is input to the n frequency divider 12 and its n
The output of the frequency divider 12 is the passive correlator 1, the time window controller 2, the delay detector 3, the diversity combiner 4, the envelope detector 6, the peak position counter 7,
The adder 15 and the memory 16 are connected as a sampling clock. The passive correlator 1 may be a matched filter or a convolver.

[0026]

As described above, according to the present invention,
In the initial mode, the adder 15 and the memory 16 are used to obtain the sum over the output of each sampling point of the envelope detector over a plurality of cycles of the spread code, and from this, the correlation peak position is detected and the time window Since the initial value of the center position is set, there is an advantage that the error between the initial value of the time window center position and the actual correlation peak position is narrowed and the synchronization can be established quickly.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating spread spectrum communication.

FIG. 3 is a diagram showing an example of a configuration of a conventional spread spectrum communication receiver.

[Explanation of symbols]

 1 Passive correlator 2 Time window controller 3 Delay detector 4 Diversity combiner 5 Decoder 6 Envelope detector 7 Peak position counter 8 Changeover switch 9 Peak position comparator 10 Up / Down counter 11 Time window center position memory 12 n Frequency divider 13 Oscillator 14 Averager 15 Adder 16 Memory 17 Peak position detector

Claims (1)

[Claims] 1. A receiver for spread spectrum communication, wherein a time window is provided for a despread signal, and demodulation is performed after detection only for a signal that has passed through the time window. Envelope detection is performed on the despread signal. An input signal to add the input and the contents of the memory, a memory connected to the adder for storing the addition result, and a peak for detecting a sampling point having the maximum value from the output signal of the memory A position detector, a time window center position memory for storing the output of the peak position detector, and a path for transmitting the contents of the time window center position memory to a means for controlling the time window as an initial value of the center position of the time window. A synchronizer for spread spectrum communication, comprising: