JPH09167981A - Spread spectrum receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform the initial synchronous acquisition of a spreading code for performing an inverse spread spectrum at the time of starting a reception without using other means. SOLUTION: The synchronization of reception signals is taken with a local oscillator 12 which is necessary for performing a synchronous detection in a phase locked loop PLL. A delay locked loop 20 takes the synchronization of the spreading codes which are necessary for performing an inverse spread spectrum. When the spread spectrum signal enters from a non-reception state, a state is the one that the synchronization of the delay locked loop 20 is not taken at first. Because an inverse spreading is not rightly performed for received data in the inverse spreading device 13 of the reception signal, received data can not be rightly reproduced. The delay locked loop 20 takes the difference of the outputs of a phase advancing correlation device 21 and a phase delay correlation device 29 by a subtracter 27 via absolute value circuits 23 and 26. Thus, because the fluctuation by received data is eliminated without preforming an inverse modulation for the polarity of the phase deviation information on the spreading code for inverse spreading generated in a spreading code generator 33 by using received data, the delay locked loop 20 can be normally operated in a state that received data is not reproduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum receiver for receiving a spread spectrum received signal.

[0002]

2. Description of the Related Art An example of a delay locked loop used on the receiver side of a conventional spread spectrum communication is shown in FIG.
This will be described. FIG. 4 is described in the proceedings of the lecture number B-407 at the "1995 IEICE General Conference". The blocks in the figure are denoted by the reference numerals as shown in FIG. 4, which will be described below.

In FIG. 4, the spread spectrum received signal is subjected to frequency conversion by a frequency converter composed of a quadrature type detector 11 and a local oscillator 12, and becomes a baseband signal. In the delay lock rope 20 in the next stage, based on this baseband signal, a spread code for despreading, which is synchronized with the spread code that spreads the received signal, is generated, and the correlator 13 is used using this spread code. The received signal converted into the baseband signal is despread and the received data is taken out by the data detector 19.

Here, the received baseband signal input to the delay locked loop 20 is the spread spectrum of the received data, so that the received data appears after passing through the correlator for despreading. become. Therefore, the phase shift information of the despread spreading code generated by subtracting the output of the phase delay correlator 21 from the phase delay correlator 24 in the delay lock loop 20 by the subtractor 27 has a polarity depending on the received data included therein. Will fluctuate. This cannot be used as it is for the phase control of the spreading code generator 103 for generating the spreading code for despreading.

Therefore, in the delay locked loop 20 used in the receiver of the conventional spread spectrum apparatus shown in FIG.
The output of the subtractor 27 is re-modulated by the inverse modulator 101 using the reception data output from the data detector 19, thereby removing the reception data component. This prevents the polarity of the phase shift information of the despreading spreading code output from the subtractor 27 from varying depending on the received data included therein, and generates the despreading spreading code by the spreading code generator 1.
It becomes possible to use it for 03 phase control.

As described above, in the conventional spread spectrum receiver shown in FIG. 4, in order to properly operate the delay lock loop used in the receiver, the data detector for reproducing the received data operates properly. You must be present.

However, the conventional spread spectrum receiver shown in FIG. 4 has the following drawbacks. When the received signal starts to be input from the state where there is no received signal, the delay lock loop of the receiver is not in the initial state of synchronization acquisition. Then, since the received signal cannot be subjected to spectrum despreading, the data detector 19 cannot reproduce the received data. If the reception data cannot be reproduced, the polarity of the phase shift information of the despreading spreading code cannot be prevented from changing by the reception data component in the inverse modulator 101 in the delay lock loop, so that the delay lock loop is normally operated. Will not work. For this reason, the spread code cannot be synchronized and the spectrum cannot be despread over time.

As described above, in the conventional spread spectrum receiver, it is difficult to acquire the initial synchronization of the spread code for performing the inverse spread spectrum at the start of reception only by the delay lock loop of the receiver, and some other means. There is a problem that the structure becomes complicated by that much because it is necessary to establish the initial synchronization by using.

[0009]

As described above, in the conventional spread spectrum receiver, the initial synchronization acquisition of the spread code for performing the inverse spread spectrum at the start of reception is
There is a problem that the delay lock loop of the receiver alone is difficult, and some other means must be used to establish the initial synchronization, which complicates the structure.

According to the present invention, the delay lock loop alone enables the initial synchronization acquisition of the spread code for performing the inverse spread spectrum at the start of reception.

[0011]

In order to solve the above problems, in the spread spectrum receiver of the present invention, the outputs of the phase lead correlator and the phase delay correlator are respectively output in the delay locked loop used in the receiver. By subtracting after passing through the absolute value circuit, the polarity of the phase shift information of the despreading spreading code is not inversely modulated by using the received data, and the fluctuation due to the received data is eliminated. Is.

By such means, the delay locked loop operates normally regardless of the received data, so that even when the received data is not reproduced, as when the received signal starts being input from the state where there is no received signal, Delay lock loop Operates normally and can perform synchronization acquisition. Therefore, the initial synchronization acquisition of the spread code for performing the inverse spread spectrum at the start of reception does not need to establish the initial synchronization by using other means, and the structure of the spread spectrum receiver can be simplified accordingly.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a circuit configuration diagram for explaining a first embodiment of the present invention. In FIG. 1, 10 is an antenna, 11 is a down converter, 12 is a local oscillator, 13 is a despreader, 14
Is a filter, 15 is a phase detector, and 16 is a loop filter. For performing synchronous detection by a phase-locked loop including the down converter 11, the local oscillator 12, the filter 14, the phase detector 15, and the loop filter 16. The required local oscillator 12 and the received signal are synchronized.
Reference numeral 20 is a delay lock loop for synchronizing the spread codes necessary for performing the spectrum despreading.

Now, considering the case where a spread spectrum received signal enters from the antenna 10 when there is no received signal, the delay locked loop 20 is initially out of synchronization. Therefore, the received data is not properly despread by the despreader 13 of the received signal, so that the received data cannot be reproduced.

However, in this embodiment, the delay locked loop 20 causes the outputs of the phase lead correlator 21 and the phase delay correlator 24 to pass through the absolute value circuits 23 and 26 via the filters 22 and 25, respectively. Then, the subtractor 27 is configured to take the difference. As a result, the spread code generator 33
Since the polarity of the phase shift information of the despreading spreading code generated in 1 is eliminated by the received data without being inversely modulated, the delay lock loop 20 operates normally even when the received data is not reproduced. To do. Therefore, it is possible to perform synchronization acquisition for spectrum despreading. Then, if the synchronization of the spread code for spectrum despreading can be acquired, the received data can be correctly despread by the despreader 13 for the received data, so that the data can be correctly reproduced.

As described above, in the first embodiment, even when the received data is not reproduced as in the case where the received signal starts to be input from the state where there is no received signal, the synchronization of the spread code for the inverse spread spectrum is performed. Therefore, it is possible to realize a spread spectrum receiving apparatus that does not need to acquire the initial synchronization of the spread code for performing the inverse spread spectrum at the start of reception by using another means.

FIG. 2 is a circuit configuration diagram for explaining the second embodiment of the present invention. The same components as those of the embodiment shown in FIG. 1 will be described with the same reference numerals. In FIG.
10 is an antenna, 11 is a down converter, 12 is a local oscillator, 13 is a despreader, 14 is a filter, 15 is a phase detector, 16 is a loop filter, and the down converter 11, the local oscillator 12, the filter 14, the phase detection Bowl 1
5, the phase-locked loop including the loop filter 16 synchronizes the local oscillator 12 required for synchronous detection with the received signal. Reference numeral 20 is a delay lock loop for synchronizing the spread codes necessary for performing the spectrum despreading. Further, in this embodiment, the delay lock loop 20 is provided with the output, the spread code whose phase is advanced from the spread code generator 33, and the spread code whose phase is delayed, and the multipliers 42 and 43. Then, the products are respectively taken and input to the phase lead correlator 21 and the phase delay correlator 24.

Therefore, in the outputs of the phase lead correlator 21 and the phase lag correlator 24, a signal whose polarity fluctuates due to the signal of the signal generator 41 appears. However, this change in polarity can be regarded as equivalent to the change in polarity due to the received data component included in the received signal for the operation of the delay locked loop. Therefore, also in this embodiment, the basic operation is the same as that of the embodiment shown in FIG. 1, and therefore the description thereof is omitted.

This embodiment has the following features as compared with the embodiment of the present invention shown in FIG. That is, when the spectrum-spread signal is despread, the signal before the spread is reproduced, but the signal contains a DC component in principle. Therefore, in principle, the circuit block after despreading in the delay locked loop must be a DC direct connection circuit that allows a signal to pass through to a DC component. However, in an actual DC direct connection circuit, there is always a DC offset, although there is a slight difference. Therefore, for applications such as receivers where a very small level of signal must be greatly amplified, if a DC direct connection circuit is used, the generated DC offset is greatly amplified together with the signal, and the output allowable range of the circuit is increased. In reality, it is impossible to realize the receiver circuit by DC direct connection.

In the embodiment of the present invention, received data is output to the signal generator at the output of the phase advance correlator 21 and the phase delay correlator 24 in which the signals after despreading appear in the delay lock loop 20. Since it is output in a state where it is modulated with the signal output from 41, if the signal generated by the signal generator 41 does not contain a DC component, the phase lead correlation that the signal after despreading appears It is possible to remove the DC component of the signal flowing through the paths from the outputs of the detector 21 and the phase delay correlator 24 to the inputs of the detectors 23 and 26. As a result, the path from the output of the phase lead correlator 21 and the phase delay correlator 24 to the input of the detectors 23 and 26 can have a circuit configuration in which the DC component is cut, and thus D
The required amplification factor can be set without worrying about the C offset. As described above, by using the embodiment of the present invention shown in FIG. 2, the spread spectrum receiver can be realized with a realistic circuit configuration in which the DC component is cut.

FIG. 3 illustrates a third embodiment of the present invention. In this embodiment as well, parts having the same functions as those of the first and second embodiments are designated by the same reference numerals and described.

In this embodiment, the delay locked loop 2
A signal generator 41 is provided in 0, and the output and the received signal are multiplied by a multiplier 44 and then input to the phase advance correlator 21 and the phase delay correlator 24. Therefore, the number of multipliers is reduced by one as compared with the configuration of the embodiment shown in FIG.

As a result, the circuit scale can be reduced by that amount, and the spread code generator 33 can also lead the phase advance correlator 21.
Since an extra circuit block does not enter between the phase-lag correlator 24 and the phase-lag correlator 24, the skew occurring between the spread codes input from the spread-code generator 33 to each of the phase-lead correlator 21 and the phase-lag correlator 24 is reduced. Therefore, there is an advantage that the accuracy of synchronous tracking can be improved by that amount.

The basic operation is the same as that of the embodiment of the present invention shown in FIG. 1, and therefore its explanation is omitted. Even in the case of the configuration shown in FIG. 3, as in the case of the second embodiment shown in FIG. 2, the polarities of the outputs of the phase lead correlator 21 and the phase delay correlator 24 are changed by the signal of the signal generator 41. The signal to do appears. Therefore, the signal generator 41
If a signal that does not include a DC component is selected as the signal generated in step 2, the phase lead correlator 21 and the phase delay correlator 24 from which the despread signal appears will be generated as in the case of the embodiment of FIG.
It is possible to remove the DC component of the signal flowing through the path from the output to the input of the detectors 23 and 26.

As described above, in this embodiment, the path from the outputs of the phase-leading correlator 21 and the phase-lagging correlator 24 to the inputs of the detectors 23 and 26 has a circuit configuration in which the DC component is cut. Therefore, the required amplification factor can be set without worrying about the DC offset, and the spread spectrum receiver can be realized with a realistic circuit configuration.

[0026]

As described above, according to the spread spectrum receiver of the present invention, even when the received data is not reproduced as in the case where the received signal starts to be input from the state where there is no received signal, the delay locked loop is obtained. Can operate normally to perform synchronization acquisition, without using any other means for initial synchronization acquisition that causes an increase in circuit scale.
It is possible to capture the initial synchronization of the spread code for despreading the spectrum at the start of reception.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram for explaining a first embodiment of the present invention.

FIG. 2 is a circuit configuration diagram for explaining a second embodiment of the present invention.

FIG. 3 is a circuit configuration diagram for explaining a third embodiment of the present invention.

FIG. 4 is a circuit configuration diagram for explaining a conventional spread spectrum receiver.

[Explanation of symbols]

10 ... Antenna, 11 ... Down converter, 12 ... Local oscillator, 13 ... Despreader, 14 ... Filter, 15 ... Phase detector, 16 ... Loop filter, PLL ... Phase locked loop, 20 ... Delay locked loop, 21 ... Phase Lead correlator, 24 ... Phase delay correlator, 22, 25 ... Filter,
23, 26 ... Absolute value circuit, 27 ... Subtractor, 33 ... Spread code generator, 41 ... Signal generator, 42, 43, 44 ... Multiplier.

Claims (3)

[Claims] 1. A spread spectrum signal is received,
In a spread spectrum receiver including a delay lock loop that performs synchronous tracking of a spread code for despreading the received signal based on a signal obtained by converting the received signal into a baseband signal, A spread spectrum characterized in that absolute value detection is performed before subtracting and combining the outputs of the phase-leading and phase-lagging correlators, and the information signal component that interferes with the synchronous tracking operation is removed from the received signal. Receiver. 2. Receiving a spread spectrum signal,
A desired signal is generated in a spread spectrum receiver including a delay lock loop that performs synchronous tracking of a spread code for despreading the received signal based on a signal obtained by converting the received signal into a baseband signal. A signal generator, a spreading code generator for generating the spreading code for despreading, a spreading code with an advanced phase and a spreading code with a delayed phase output from the spreading code generator, and the signal generator From the first and second correlators that output the output from which the DC component has been removed by correlating with the received signal by inputting them to the phase lead and phase lag correlators respectively. A spread spectrum receiving device characterized by: 3. Receiving a spread spectrum signal,
A desired signal is generated in a spread spectrum receiver including a delay lock loop that performs synchronous tracking of a spread code for despreading the received signal based on a signal obtained by converting the received signal into a baseband signal. A signal generator, a spreading code generator for generating the spreading code for despreading, a product of the output signals from the signal generator and the received signal, and then output from the spreading code generator. Spread-spectrum reception characterized by comprising a phase-advanced and phase-delayed correlator that correlates with each of the spread code with advanced phase and the spread code with delayed phase, and outputs the output from which the DC component is removed. apparatus.