JPH0771021B2 - Synchronous circuit - Google Patents

Description

TECHNICAL FIELD The present invention relates to a synchronizing circuit, and more particularly to a synchronizing circuit for a receiver using a spread spectrum modulation method in the field of wireless communication.

[Conventional technology]

FIG. 6 shows a block diagram of a conventional system of a synchronizing circuit of a spread spectrum receiver.

This synchronizing circuit has a spread spectrum signal input terminal 1,
Correlation detector 1 for detecting a correlation value between local spread signal 106 and input signal 101, spread signal generator 5 for generating local spread signal 106, clock generator 6 for supplying clock 105 to spread signal generator 5, correlation Maximum value detection circuit 4, which receives the output 102 of the detector 2 and detects the maximum value of the phase value in one cycle of the local spread signal 106 while controlling the phase of the clock of the clock generator 6 by the phase control signal 104, maximum value detection The synchronization determination circuit 3 receives the maximum value detection end signal 103 from the circuit 4 and determines the synchronization state of the output 102 of the correlation detector 2 at the maximum correlation value. The operation of this circuit will be described below.

The output 102 of the correlation detector 2 with respect to the phase difference ψ between the input signal 101 and the locally spread signal 106 is shown in FIG. M is the repeating cycle of the output. The synchronization circuit of the spread spectrum receiver controls the phase of the local spread signal so that the phase value ψ ₀ that maximizes the correlation value between the input signal and the local spread signal.

The maximum value detection circuit 4 shifts the phase of the clock generator 6 by the phase control signal 104 at regular time intervals. The output of the spread signal generator 5 driven by the clock 105 output from the clock generator 6 also shifts its phase at regular time intervals according to the phase shift of the clock. The maximum value detection circuit shifts its phase at regular time intervals according to the phase shift. The maximum value detection circuit 4 observes the output 102 of the correlation detector 2 for each phase shift, and performs this operation on the spread signal 1
The phase ψmax at the maximum correlation value in this section is detected by performing only the section M of FIG. 2 which is a cycle.
This is shown in FIG.

3A shows the output waveform of the correlation detector 2, and FIG. 3B shows the waveform of the phase control signal 104. When the maximum detection is completed, the phase of the spread signal generator 5 is set to ψmax, and then the synchronization determination circuit 3
The maximum value detection end signal 103 is output to. Synchronization determination circuit 3
Then, upon receipt of this end signal 103, the synchronization state when ψmax is determined. If the result of determination is that it is in an asynchronous state, maximum value detection is performed again. In the case of the synchronized state, the operation of this synchronizing circuit ends. When the operation of the synchronizing circuit is completed by the above operation, the synchronized state in the spread spectrum receiver, that is, the state of ψ ₀ in FIG. 2 is obtained.

[Problems to be Solved by the Invention]

In the conventional synchronous circuit described above, when an input signal comes in from a certain ψ ₁ during the maximum value detection as shown in FIG. 4, ψ max becomes the phase of ψ max in the same figure. If the S / N of the output 102 of the correlation detector 2 is low, this ψ
In max, sufficient S / N is not obtained and it is judged as asynchronous by the synchronous judgment circuit 3, and the maximum value is detected again, so that ψ in FIG.
_{Although 0} is obtained, if the S / N is high, the synchronization determination circuit 3 does not determine this as a synchronization state, so that there is a disadvantage that the synchronization circuit ends the operation in an incorrect phase.

An object of the present invention is to solve the above-mentioned drawbacks and to provide a synchronizing circuit which can always obtain a correct synchronizing state even when a signal comes in during the maximum value detection.

[Means for Solving the Problems]

The circuit of the present invention includes a correlation detector that receives a spread spectrum signal and detects a correlation value with a local spread signal, a spread signal generator that generates a local spread signal, and a clock generator that supplies a clock to the spread signal generator. A maximum value detection circuit for detecting the maximum correlation value in one cycle of the spread signal by controlling the phase of the clock generator by receiving the output of the correlation detector, and the maximum value receiving circuit for receiving the signal from the correlation detector. In a synchronization circuit of a spread spectrum receiving device having a period determination circuit for determining the period state in the correlation value,
The maximum value detection circuit receives a synchronization determination signal from the synchronization determination circuit, and is again provided with a synchronization control circuit for detecting the maximum correlation value only once.

〔Example〕

 Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. The embodiment shown in FIG. 1 has, in addition to the conventional circuit shown in FIG. 6, a synchronization control circuit 7 for receiving the synchronization determination signal 107 from the synchronization determination circuit 3 and operating the maximum value detection circuit 4. Next, the operation will be described.

FIG. 5 shows the output 102 of the correlation detector 2.
The section M ₁ is a part in which the maximum value is detected, and the input signal comes in from ψ ₁ on the way. In this case, the phase at the maximum correlation value is ψmax ₁ , and in the next section D, the synchronization determination is performed with this phase ψmax ₁ . As a result of the synchronization determination, when the synchronization determination circuit 3 determines the synchronization state, the synchronization determination signal 107
Is output and the synchronous control circuit again detects the maximum value, the command signal 108 is output to the gravity 5 to operate the maximum value detection circuit only once. Since the section M _{2 in} FIG. 5 is the part where the maximum value is detected and the input signal is input from the beginning, the phase ψ max ₂ of the maximum correlation value obtained here is the second value.
Since it corresponds to ψ ₀ in the figure, a correct synchronization state can be obtained.

〔The invention's effect〕

As described above, the synchronization circuit of the present invention has the control circuit that performs the maximum value detection again after the synchronization determination, so that even in the case of signal input during the maximum value detection in which the correct synchronization state cannot be obtained, This has the effect of always obtaining the correct synchronization state.

[Brief description of drawings]

1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is an output waveform diagram of a correlation detector 2 with respect to a phase difference between an input signal and a locally spread signal, and FIG. 3 is a conventional synchronizing circuit. FIG. 4 is an explanatory diagram of the operation, FIG. 4 is an explanatory diagram when the conventional synchronous circuit does not operate correctly, FIG. 5 is an explanatory diagram of the operation of the synchronous circuit of FIG. 1, and FIG. It is a block diagram. 1 ... Input terminal, 2 ... Correlation detector, 3 ... Sync decision circuit, 4 ... Maximum value detection circuit, 5 ... Spread signal generator, 6
...... Clock generator, 7 …… Synchronous control circuit.

Claims (1)

[Claims] 1. A correlation detector for receiving a spread spectrum signal and detecting a correlation value with the local spread signal, a spread signal generator for generating the local spread signal, and a clock generator for supplying a clock to the spread signal generator. And a maximum value detection circuit that receives the output of the correlation detector and detects the maximum correlation value in one cycle of the spread signal by controlling the phase of the clock generator, and the maximum correlation circuit that receives the signal from the correlation detector. In a synchronizing circuit of a spread spectrum receiving apparatus having a period judging circuit for judging a periodic state of a value, the maximum value detecting circuit receives the synchronization judging signal from the synchronizing judgment circuit and detects the maximum correlation value only once. A synchronous circuit comprising a synchronous control circuit.