JPH09172390A - Costas circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate a costas circuit, to suppress cost and to miniaturize the circuit in a non coherent type spread spectrum communication system. SOLUTION: A PN signal from a PN signal synchronization circuit 1 and a local oscillation signal from a voltage control oscillator 7 are multiplied in a multiplier 10. A multiplier 11 multiplies the local oscillation signal and a PN synchronizing signal, whose phases differ by 90 degrees. The output signals of the multipliers 10 and 11 are correlated by correlation units 3 and 4, are multiplied by a multiplier 5 and are taken out from a low pass filter 6. An inverse spread processing is executed by making the outputs pass through the correlation units 3 and 4. At the same time, the phase difference of the carrier of a reception signal and the local oscillation signal can be detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Costas circuit, and more particularly to a Costas circuit used for phase synchronization control in demodulating a synchronous spread spectrum modulated wave.

[0002]

2. Description of the Related Art FIG. 11 is a block diagram of a receiving system in a conventional spread spectrum communication system.
Reference numeral 01 is a PN (pseudo noise) signal synchronizing circuit, 102 is a phase synchronizing circuit, 110 is a despreading circuit, and 111 is a primary demodulation circuit. Since modulation and secondary modulation using a random pulse train called a PN signal are performed and transmitted, the PN signal and the carrier must be synchronized on the receiving side. In the case of this method, the PN signal is reproduced from the received signal in the PN signal synchronizing circuit 101, and the carrier is demodulated in the phase synchronizing circuit 102.

As described above, in the conventional method, the circuit is complicated because the PN signal synchronization, despreading, and data demodulation processes are performed separately. In order to eliminate such circuit complexity in spread spectrum communication, a conventional solution is, for example, Japanese Patent Laid-Open No.
As disclosed in Japanese Patent Publication No. 199205, there is a coherent spread spectrum communication system that simplifies a primary demodulation system and a secondary demodulation system to realize simplification of the above circuit. Since signals are transmitted in synchronization, there is an advantage that only one synchronization system is required on the receiving side.

[0004]

However, the above-mentioned Japanese Patent Application Laid-Open
Also in the invention of Japanese Patent Laid-Open No. 199205, there is a problem in the initial synchronization such that it is difficult to establish the initial synchronization. Claim 1
The invention of claim 2 is intended to simplify the circuit by combining the despreading circuit and the phase synchronization circuit of the carrier into one circuit. The invention of claim 2 performs the process of shifting the phase of the local oscillation circuit. This is a further simplification of the circuit after the PN signal is multiplied, and the invention of claim 3 further comprises a PN signal synchronizing circuit, a despreading circuit, and a carrier phase synchronizing circuit in one circuit. The present invention of claims 4 and 5 makes it possible to apply the invention of claim 1 to a delay locked loop which is a conventional PN signal synchronizing circuit, and the invention of claim 6 realizes a conventionally known PN. For the modified code tracking loop, which is a signal synchronization circuit,
The invention of claim 3 can be applied, and the inventions of claim 7, 8 and 9 apply the invention of claim 2 to a pseudo noise signal synchronizing circuit, thereby performing spread spectrum communication with a simple circuit. It is something that can be done.

[0005]

According to a first aspect of the present invention, in a non-coherent spread spectrum communication system, a received reference signal is obtained by multiplying a synchronized reference PN signal (pseudo noise signal) and a local oscillation signal. The first signal obtained by multiplying the low frequency component is multiplied by the reference PN signal and the signal obtained by shifting the phase of the local oscillation signal by 90 degrees, and the received signal is multiplied to obtain the low frequency component. By adopting a Costas circuit that extracts a phase error signal from the extracted second signal, despreading processing in spread spectrum communication is performed in this Costas circuit, thus simplifying the circuit and reducing costs. Hold down
This is a miniaturization of the circuit.

According to a second aspect of the present invention, in spread spectrum communication, a first signal obtained by multiplying a synchronized reference PN signal (pseudo noise signal) and a local oscillation signal, and 90 degrees in phase with the first signal. The position of the phase shifter required in the Costas circuit is different from that of the invention of claim 1 by multiplying each of the different second signals by the received signal and extracting the phase error signal from each low frequency component. To reduce the number of multipliers and further simplify the circuit.

The invention of claim 3 is an on-time (On Tim)
In the PN signal synchronization circuit using the first correlation signal obtained by up-converting the reference PN signal of e) to the intermediate frequency and extracting the correlation with the received signal, the phase of the intermediate frequency component of the first correlation signal is 90. The local oscillation of the PN signal synchronization circuit required for spread spectrum communication is performed by extracting the second correlation signals having different degrees and extracting the phase error signal from the first correlation signal and the second correlation signal. A signal from a voltage controlled oscillator of a Costas circuit is used as an oscillation source of the signal, and the circuit is further simplified as compared with claim 1, and cost reduction and circuit miniaturization are realized. is there.

According to a fourth aspect of the present invention, a delay locked loop is used as a PN signal synchronizing circuit, and the present invention is applied to a conventionally known delay locked loop. This is to make the realization easier.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the local oscillation signal for placing the PN signal of the delay locked loop on the intermediate frequency and the signal whose phase differs from the local oscillation signal by 90 degrees are turned on. By multiplying the time PN signal and extracting the phase error signal from the correlation value between these two signals and the received signal, the control signal of the voltage controlled oscillator for generating the local oscillation signal of the delay locked loop is produced. The signal from the voltage controlled oscillator of the Costas circuit is used as the oscillation source of the local oscillation signal used in the delay locked loop to further simplify the circuit.

According to a sixth aspect of the present invention, in the second aspect of the invention, the PN signal synchronizing circuit includes a modified code tracking loop (Modified Code Tracking Loo).
By using p; MCTL), the invention of claim 3 can be applied to a conventionally known PN signal synchronizing circuit, a defined code tracking loop.

According to a seventh aspect of the present invention, in the second aspect, the first correlation signal from the on-time NRZ code PN signal and the received signal, and the on-time Manchester code PN signal and the received signal are used. PN for inputting the low frequency component thereof as the control clock of the voltage control clock which is the clock source of the PN signal.
By using a signal synchronization circuit, the present invention is applied to a pseudo noise signal synchronization circuit, and spread spectrum communication can be performed with a simple circuit.

According to an eighth aspect of the present invention, in the second aspect of the present invention, the first signal obtained by multiplying the on-time PN signal, the local oscillation signal, and the received signal is multiplied, and the first signal is multiplied by the clock signal. By using a PN signal synchronizing circuit that multiplies the combined second signal and inputs the low frequency component as a control clock of a voltage control clock that is a clock source of the PN signal, a pseudo noise signal synchronizing circuit The present invention is applied to another embodiment of
This is a device that enables spread spectrum communication with a simple circuit.

According to a ninth aspect of the present invention, in the eighth aspect of the present invention, two signals having a phase difference of 90 degrees from the local oscillation signal are generated from a signal obtained by multiplying the on-time PN signal and the local oscillation signal. By extracting the phase error signal from the correlation signal between each of the signals and the received signal, the invention of claim 2 is applied to the circuit of claim 8, and the circuit can be further simplified. It is the one.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

(Invention of Claim 1) FIG. 1 is a block diagram for explaining an embodiment of the invention described in Claim 1. In FIG.
Reference numeral 1 is a PN signal synchronizing circuit, and a square 2 surrounded by a dotted line is a portion forming a Costas circuit. The Costas circuit 2 shown in FIG. 1 is a circuit for demodulating a BPSK-modulated signal, 3 and 4 are correlators, 5 and 10 and 11 are multipliers,
Reference numeral 6 is a loop filter, 7 is a voltage controlled oscillator, 8 is a phase shifter for delaying the phase by 45 degrees, and 9 is a phase shifter for delaying the phase by 45 degrees.

Next, the operation will be described. The PN signal synchronizing circuit 1 reproduces the PN signal from the received signal and transfers it to the Costas circuit 2. In the Costas circuit 2, the PN signal from the PN signal synchronizing circuit 1 and the local oscillation signal from the voltage controlled oscillator 7 are
The phase shifter 8 having a phase shift of 45 degrees and the phase shifter 9 having a phase shift of +45 degrees generate local oscillation signals different from each other by 90 degrees. Normally, the Costas circuit 2 employs a method of detecting a phase difference by multiplying a local oscillation signal having a 90-degree phase difference and a reception signal. The present invention differs from the conventional method in that the local oscillation signals having different phases by 90 degrees are multiplied by the PN signal and then by the received signal. Multipliers 10 and 11 take the product of the PN signal and two local oscillation signals having 90 ° different phases.

On the other hand, as the received signal, the received signal which has been spectrum-spread is input to the Costas circuit 2. P
The two local oscillation signals multiplied by the N signal are correlated with the received signal by correlators 3 and 4. This correlator can be configured by, for example, a multiplier that multiplies the received signal and the local oscillation signal, and a filter that extracts the low frequency component of the multiplied signal. here,
Since the PN signal from the PN signal synchronizing circuit is synchronized, despreading is performed by passing through the correlators 3 and 4, and at the same time, the phase difference between the carrier of the received signal and the local oscillation signal is detected. be able to. Here, B
In order to demodulate the PSK-modulated signal, the output signals of the correlators 3 and 4 are multiplied by the multiplier 5, and the low frequency component is input to the voltage controlled oscillator 7 through the loop filter 6 to form a Costas circuit. can do.

(Invention of Claim 2) FIG. 2 is a block diagram for explaining the invention described in Claim 2. In the figure, 20 is a multiplier, other than the embodiment shown in FIG. The same reference numerals as in the case of FIG. Thus, in this embodiment, the product of the local oscillation signal and the PN signal is taken by the multiplier 20 and then the phase of the local oscillation signal is shifted, thereby reducing the number of multipliers by one and further simplifying the circuit. It is a thing. That is, in the embodiment of FIG. 2, the local oscillation signal from the voltage controlled oscillator 7 and P
The reference PN signal from the N-synchronous circuit 1 is multiplied by the multiplier 20, and then the phase shifters 8 and 9 obtain signals in which the phases of the local oscillation signals differ by 90 degrees.

(Invention of Claim 3) FIG. 3 is a block diagram for explaining the invention described in Claim 3, and in FIG.
0 and 31 are multipliers, 32 and 33 are low-pass filters, 3
Reference numeral 4 is a phase difference detection circuit for the PN signal, 35 is a loop filter for the PN signal synchronizing circuit, 36 is a voltage control clock, 37 is a PN signal generator, and other parts that perform the same operations as those of the embodiment shown in FIG. Are given the same reference numerals as in FIG. Thus, this embodiment is an on-time PN.
In a PN signal synchronizing circuit for synchronizing using a signal, the circuit can be further simplified.

Next, the operation will be described. Generally, in the PN signal synchronizing circuit, when the correlation between the reference PN signal and the received signal is obtained, a method of putting the reference PN signal on the intermediate frequency and then obtaining the correlation with the received signal is used. In this case, the circuit can be simplified by using the voltage controlled oscillator of the Costas circuit for the local oscillation circuit that produces this intermediate frequency. In FIG. 3, the PN signal generator 37 generates a PN signal by the clock signal from the voltage control clock 36. The PN signal generator 37 has a PN signal on the signal line b necessary for synchronizing the PN signal in addition to the on-time PN signal represented by the signal line a in FIG.
Generates early and late signals in the delay locked loop. The PN signal generated by the PN signal synchronizing circuit 37 is added to the intermediate frequency by the local oscillation signal from the phase shifter 9 of the Costas circuit 2.

Here, the on-time signal is also multiplied by the local oscillation signal from the phase shifter 8 in the multiplier 11. As a result, the on-time PN signal becomes two local oscillation signals that are 90 degrees out of phase with each other, and are multiplied by the received signals by the transposition devices 30 and 31, respectively, and are correlated by passing through the low-pass filters 32 and 33. 2
The phase error signal is extracted by multiplying the two correlation signals by the multiplier 5, and is fed back to the voltage controlled oscillator 7 to form a Costas circuit. Also, one of the two correlation signals of the on-time PN signal and the received signal
One is input to the phase difference detection circuit 34 of the PN signal, the phase difference signal of the PN signal is taken out, and the control signal of the voltage control clock 36 is generated by passing through the loop filter 35. Configure.

Also in the embodiment shown in FIG. 3, as shown in FIG. 4, a method of shifting the phase of the local oscillation signal after multiplying the PN signal by the local oscillation signal can be considered. FIG.
In the figure, the same numbers are attached to the circuit portions that play the same role as in FIGS. That is, in FIG. 4, as in FIG. 2, the product of the PN signal from the PN signal generator 37 and the local oscillation signal from the voltage controlled oscillator 7 is taken by the multiplier 20, and this is locally oscillated by the phase shifters 8 and 9. Signals with different 90-degree phases are obtained.

(Invention of Claim 4) FIG. 5 is a block diagram for explaining the invention of Claim 4. In this embodiment, a delay locked loop is used as a PN signal synchronizing circuit used in Claim 1. In FIG. 5, 50 is a subtractor, 51 is a local oscillation circuit, 52, 53, 54 and 55 are multipliers, 56 and 57 are band pass filters, 58 and 59 are envelope detection circuits, and others. The blocks having the same functions as those in FIGS. 1 and 2 are given the same numbers.

In FIG. 5, a dotted square 2 is a Costas circuit, and a dotted square 1 is a PN signal synchronizing circuit when a delay lock loop is used. PN in the dotted square 1
From the signal generation circuit 37, an on-time PN signal a, an early signal b whose phase is advanced by 1 / 2π with respect to the on-time signal, and a phase 1 / with respect to the on-time signal
Each of the late signals c delayed by 2π is generated. The late signal and the early signal are respectively multiplied by 5
2, 53 put on the intermediate frequency. Then, the multiplier 55, the bandpass filter 56, the envelope detection circuit 5
8 correlates the early signal and the received signal, and the multiplier 54, the band pass filter 57, and the envelope detection circuit 59 correlate the late signal and the received signal. By subtracting the difference between these two correlation signals with the subtractor 50, the phase error signal of the PN signal can be obtained. By inputting it as the control signal of the voltage control clock 36 through the loop filter 35, the phase synchronization circuit of the PN signal Make up. When synchronized with this delay locked loop, the PN signal a is a signal with synchronized phases. By inputting this on-time PN signal to the Costas circuit 2, the same operation as in claim 1 is achieved.

FIG. 6 is a block diagram for explaining the invention described in claim 5. In FIG. 6, reference numerals 61 and 62 denote low-pass filters, and other functions similar to those shown in FIGS. Regarding the circuit portion to be fulfilled, FIG. 1, FIG. 3, FIG.
The same number is attached.

In FIG. 6, the on-time signal a, the early signal b, and the late signal c generated by the PN signal generator 37 are generated.
Is used as the local oscillation signal from the voltage controlled oscillator 7 of the Costas circuit. In this case, the correlation signal between the early signal and the received signal,
Further, since the correlation signal between the late signal and the received signal has a frequency near the base band, the band pass filters 56 and 57 in FIG. 5 are the low pass filters 61 and 6 in FIG.
Replace with 2. Thereby, the multiplier 55, the low-pass filter 61, and the envelope detection circuit 58 obtain the correlation between the received signal and the early signal, and the multiplier 54, the low-pass filter 62, and the envelope detection circuit 59 obtain the received signal and the late signal. Correlation is taken. A phase difference signal is generated from the two correlation signals by the subtractor 50 and is fed back to the voltage controlled oscillator 36 through the loop filter 35.

On the other hand, the on-time PN signal is multiplied by the signals from the phase shifters 8 and 9 and then correlated with the received signal by the multiplier 30 and the correlator using the low-pass filter 32, and the multiplier 31 and the low-pass filter. Correlation is obtained by the correlator of the filter 33, and the phase difference signal of the local oscillation signal is produced by the product 5 of these two correlation signals and fed back to the voltage controlled oscillator 7. Even in a delay locked loop,
As in the second aspect, the number of multipliers can be reduced by multiplying the PN signal and the local oscillation signal and then shifting the phase of the local oscillation signal. Also, the delay locked loop does not affect the phase of the local oscillator signal. Therefore, FIG.
, The phase shifter 9 is applied to the early signal b and the late signal c.
What is multiplied by the local oscillation signal from the above may be added to the intermediate frequency by the local oscillation signal from the voltage controlled oscillator 7.

(Invention of Claim 6) FIG. 7 is a block diagram for explaining an embodiment of the invention described in Claim 6. In FIG. 7, 70 is a subtractor, 71 is a multiplier, and 72 is a low-pass filter. In the filter, the other circuit parts having the same functions as those in FIGS. 1, 3 and 6 are denoted by the same reference numerals. Thus, the present invention provides a modified code tracking loop (Modified Cod) as an example of the PN signal synchronizing circuit using the on-time PN signal.
eTrackin Loop; MCTL).

In FIG. 7, in the MCTL, a subtracter 70 subtracts a product of an early signal and a received signal and a product of a late signal and a received signal at an intermediate frequency, and then a signal passed through a filter 72 is turned on by a multiplier 71. Detection is performed by multiplying the time PN signal and the correlation signal of the received signal. Therefore, the correlation signal between the on-time PN signal used in the PN synchronization circuit and the received signal is obtained, and in addition to the multiplier 31 and the low-pass filter 33, the multiplier 30 and the low-pass filter 3 are also provided.
A phase error signal of the Costas circuit can be made by preparing No. 2 and making a correlation signal of the received signal and the signal in which the phase of the intermediate frequency differs from the on-time signal by 90 degrees.

(Invention of Claim 7) FIG. 8 is a block diagram for explaining the invention described in claim 7, in which 81 is a low-pass filter, 82 and 83 are multipliers, and FIG. The same numbers are given to the circuit parts that play the same role as in FIGS. In this embodiment, the pseudo noise signal synchronizing circuit is used as the PN signal synchronizing circuit which uses the on-time PN signal.

In the PN signal generator 37 of the PN signal synchronizing circuit shown in FIG. 8, NRZ which is a code format usually used.
Code PN signal a and PN called Manchester code
Generate signal d. Therefore, the PN signal a of the NRZ code a
Is multiplied by an intermediate frequency with local oscillation signals having different 90-degree phases from the phase shifters 8 and 9, and the phase error signal of the Costas circuit can be obtained by correlating each signal with the received signal. Since the PN signal d of the Manchester code is added to the local oscillation signal from the phase shifter 9, the correlation signal between the PN signal of the Manchester code and the received signal and the NRZ added to the intermediate frequency by the local signal of the phase shifter 9 are added. The phase error signal of the PN signal synchronizing circuit can be obtained by the product of the sign PN signal and the correlation signal.

(Invention of Claim 8) Further, in the pseudo noise signal synchronizing circuit, there are some other methods for constructing the synchronizing circuit of the PN signal. An embodiment using one of them is shown in FIG. In FIG. 9, reference numeral 91 is a multiplier, and the circuit parts having the same functions as those in FIGS. 1, 3, 7, and 8 are given the same numbers as in FIGS. 1, 3, 7, and 8. . In the case of the embodiment of FIG. 9, the on-time P
Only N signals are generated. Therefore, this signal may be multiplied by the local oscillation signal from the phase shifters 8 and 9. Thereby, the output from the correlator by the multiplier 30 and the low-pass filter 32, the multiplier 31 and the low-pass filter 33.
The phase error signal of the Costas circuit can be obtained from the output signal from the correlator. Further, since the output signal of the multiplier 31 is also multiplied by the voltage control clock and then input to the low pass filter 81, the output signal of the low pass filter 81 becomes a correlation signal of the reception signal, the PN signal and the clock signal. This signal and the low pass filter 3
The phase error signal of the PN signal synchronizing circuit can be obtained by multiplying the correlation signal from 3 by the multiplier 71.

(Invention of Claim 9) FIG. 10 is a block diagram showing an embodiment of the invention described in Claim 9, which is further simplified by using the method of Claim 2 in the embodiment of FIG. It is a thing. That is, FIG. 1, FIG. 2, FIG. 3, FIG.
The same numbers are given to the circuit portions that play the same role as in FIGS. 8 and 9. As shown in FIG. 10, after the local oscillation signal is multiplied by the PN signal by the multiplier 20, the phase shifters 8 and 9 can generate the PN signal in which the phases of the local oscillation signals are different by 90 degrees.

[0033]

According to the invention of claim 1, in the spread spectrum communication, a synchronized reference PN signal (pseudo noise signal) is obtained.
And a local oscillation signal are multiplied to obtain a reception signal, and the first signal obtained by extracting the low frequency component thereof is multiplied by the reference PN signal and a signal obtained by shifting the phase of the local oscillation signal by 90 degrees. It is characterized in that a phase error signal is extracted from the second signal obtained by multiplying the received signal and extracting the low frequency component thereof.
In the non-coherent spread spectrum communication system, a Costas circuit is adopted as a carrier synchronization circuit of the primary demodulation system, and despread processing in spread spectrum communication is performed in this Costas circuit to simplify the circuit and reduce costs. It is possible to reduce the size of the circuit by suppressing.

According to a second aspect of the present invention, in spread spectrum communication, a first signal obtained by multiplying a synchronized reference PN signal (pseudo noise signal) and a local oscillation signal, and 90 degrees in phase with the first signal. Each of the different second signals is multiplied by the received signal, and the phase error signal is extracted from each low frequency component.
The position of the phase shifter required in the Costas circuit can be changed to reduce the number of multipliers, and the circuit can be further simplified.

The invention of claim 3 is the on-time (On Tim)
In the PN signal synchronization circuit using the first correlation signal obtained by up-converting the reference PN signal of e) to the intermediate frequency and extracting the correlation with the received signal, the phase of the intermediate frequency component of the first correlation signal is 90. It is characterized in that a second correlation signal different in degree is taken out, and a phase error signal is taken out from the first correlation signal and the second correlation signal, whereby a PN necessary for spread spectrum communication is obtained.
The signal from the voltage controlled oscillator of the Costas circuit is used as the oscillation source of the local oscillation signal of the signal synchronization circuit, and the circuit is further simplified, the cost is reduced and the circuit is downsized, compared to the first aspect. realizable.

The invention of claim 4 is characterized in that a delay locked loop is used as a PN signal synchronizing circuit, whereby the present invention is applied to a conventionally known delay locked loop. By applying, the present invention can be realized more easily.

According to a fifth aspect of the present invention, in the first aspect of the present invention, a local oscillation signal for placing the PN signal of the delay locked loop on an intermediate frequency and a phase of 90 degrees with the local oscillation signal.
A control signal of a voltage controlled oscillator for generating a local oscillation signal of the delay locked loop by multiplying each of the different signals by an on-time PN signal, extracting a phase error signal from the correlation value between these two signals and the received signal. By this, the signal from the voltage controlled oscillator of the Costas circuit is used as the oscillation source of the local oscillation signal used in the delay locked loop, and the circuit can be further simplified.

According to a sixth aspect of the present invention, in the second aspect of the invention, the PN signal synchronizing circuit includes a modified code tracking loop (Modified Code Tracking Loo).
p; MCTL) is used, whereby the invention of claim 3 can be applied to a defined code tracking loop which is a conventionally known PN signal synchronizing circuit.

According to the invention of claim 7, in the invention of claim 2, the first correlation signal from the PN signal of the on-time NRZ code and the received signal and the PN signal of the on-time Manchester code and the received signal are used. PN for inputting the low frequency component thereof as the control clock of the voltage control clock which is the clock source of the PN signal.
It is characterized by using a signal synchronization circuit,
As a result, the present invention is applied to the pseudo noise signal synchronization circuit, and the spread spectrum communication can be performed with a simple circuit.

According to an eighth aspect of the present invention, in the second aspect, the first signal obtained by multiplying the on-time PN signal, the local oscillation signal, and the received signal, and the first signal by the clock signal are multiplied. It is characterized in that a PN signal synchronizing circuit is used which multiplies the combined second signal and inputs the low frequency component as a control clock of a voltage control clock serving as a clock source of the PN signal. ,
The present invention is applied to another embodiment of the pseudo noise signal synchronization circuit, and spread spectrum communication can be performed with a simple circuit.

According to a ninth aspect of the present invention, in the eighth aspect of the present invention, two signals, in which the phase of the local oscillation signal is different by 90 degrees, are generated from the signal obtained by multiplying the on-time PN signal and the local oscillation signal. The phase error signal is extracted from the correlation signal between each of the signals and the received signal, whereby the invention of claim 2 is applied to the circuit of claim 8, and the circuit is further modified. It can be simplified.

[Brief description of the drawings]

FIG. 1 is a block diagram for explaining an embodiment of the invention described in claim 1.

FIG. 2 is a block diagram for explaining an embodiment of the invention described in claim 2.

FIG. 3 is a block diagram for explaining an embodiment of the invention described in claim 3.

FIG. 4 is a block diagram for explaining another embodiment of the invention described in claim 3;

FIG. 5 is a block diagram for explaining an embodiment of the invention described in claim 4.

FIG. 6 is a block diagram for explaining an embodiment of the invention described in claim 5;

FIG. 7 is a block diagram for explaining an embodiment of the invention described in claim 6;

FIG. 8 is a block diagram for explaining an embodiment of the invention described in claim 7.

FIG. 9 is a block diagram for explaining an embodiment of the invention described in claim 8.

FIG. 10 is a block diagram for explaining an embodiment of the invention described in claim 9.

FIG. 11 is a block diagram of a main part of a reception system in a conventional spread spectrum communication system.

[Explanation of symbols]

1 ... PN signal synchronizing circuit, 2 ... Costas circuit, 3, 4 ... Correlator, 5, 10, 11 ... Multiplier, 6 ... Loop filter,
7 ... Voltage controlled oscillator, 8, 9 ... Phase shifter, 20, 3
0, 31 ... Multiplier, 32, 33 ... Low-pass filter, 3
4 ... Phase difference detection circuit, 35 ... Loop filter, 36 ... Voltage control clock, 37 ... PN signal generator, 50 ... Subtractor, 51 ... Local oscillation circuit, 52, 53, 54, 55 ... Multiplier, 56, 57 … Bandpass filters, 58, 59…
Envelope detection circuit, 61, 62 ... Low-pass filter, 70
... Subtractor, 71 ... Multiplier, 72 ... Low-pass filter, 8
1 ... Low-pass filter, 82, 83 ... Multiplier, 101 ...
PN (pseudo noise) signal synchronization circuit, 102 ... Phase synchronization circuit, 110 ... Despreading circuit, 111 ... Primary demodulation circuit.

Claims (9)

[Claims] 1. In spread spectrum communication, a synchronized reference PN signal and a local oscillation signal are multiplied together to obtain a received signal, and a low frequency component is extracted from the first signal and the reference PN signal. A Costas circuit, wherein a phase error signal is extracted from a second signal obtained by multiplying the received signal by multiplying a signal obtained by shifting the phase of the local oscillation signal by 90 degrees, and a second signal obtained by extracting a low frequency component thereof. 2. In spread spectrum communication, each of a first signal obtained by multiplying a synchronized reference PN signal and a local oscillation signal and a second signal having a phase difference of 90 degrees from that of the first signal are received signals. The Costas circuit is characterized by multiplying with and extracting the phase error signal from each low frequency component. 3. A PN signal synchronizing circuit which up-converts an on-time reference PN signal to an intermediate frequency and uses a first correlation signal which is obtained by extracting a correlation with a received signal,
A Costas circuit, wherein a second correlation signal in which the phase of the intermediate frequency component of the first correlation signal is different by 90 degrees is extracted, and a phase error signal is extracted from the first correlation signal and the second correlation signal. . 4. The Costas circuit according to claim 1, wherein a delay locked loop is used as a PN signal synchronizing circuit. 5. A local oscillation signal for placing a PN signal of a delay locked loop on an intermediate frequency and a signal whose phase is different from the local oscillation signal by 90 degrees are multiplied by an on-time PN signal, and these two signals are obtained. 2. The Costas circuit according to claim 1, wherein a phase error signal is extracted from a correlation value between the received signal and a received signal to generate a control signal of a voltage controlled oscillator that generates a local oscillation signal of the delay locked loop. 6. The Costas circuit according to claim 2, wherein a modified code tracking loop is used in the PN signal synchronizing circuit. 7. The PN signal of the on-time NRZ code and the first correlation signal from the received signal, and the PN signal of the on-time Manchester code and the second correlation signal from the received signal are multiplied, The Costas circuit according to claim 2, wherein a PN signal synchronizing circuit is used which inputs a frequency component as a control clock of a voltage control clock which is a clock source of the PN signal. 8. A first signal obtained by multiplying an on-time PN signal, a local oscillation signal, and a received signal, and a second signal obtained by multiplying a first signal by a clock signal, the low signal of which is multiplied. The Costas circuit according to claim 2, wherein a PN signal synchronizing circuit is used which inputs a frequency component as a control clock of a voltage control clock which is a clock source of the PN signal. 9. A signal obtained by multiplying an on-time PN signal and a local oscillation signal by generating two signals having a phase of the local oscillation signal different by 90 degrees, and a phase is obtained from a correlation signal between each of these two signals and a reception signal. 9. The Costas circuit according to claim 8, wherein an error signal is extracted.