JPS5951786B2 - timing signal detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a timing signal detection circuit used in a pulse communication system, and more particularly to a circuit for detecting a timing signal from a pulse amplitude modulated signal using a phase synchronization circuit.

Pulse Amplitude In mackerel, information is transmitted in the form of the amplitude or polarity of pulses occurring at a constant gmM.

In order to correctly identify the original 1* signal from this signal on the receiving side, information regarding the pulse repetition frequency of the transmitted pulse, that is, a timing signal is required.

Generally, a method is used to detect this timing signal from the received signal.

One of the conventionally widely used detection methods is to differentiate the received signal, double-wave rectify the result, then use a narrow band filter to extract the timing signal component and remove noise. This is a method to obtain a timing signal by keeping the amplitude constant.

Another recently proposed method is to use a band-pass filter whose center frequency is one half of the pulse repetition frequency instead of the differentiation in the above method.

The latter method is said to reduce the phase jitter of the detected timing signal compared to the former method.

However, both of these imaging methods require a double-wave rectifier circuit as an essential element.

Generally, double-wave rectifier circuits are realized using diodes, but since parasitic reactance is unavoidable in the elements and circuits when realizing the circuit, a phase shift in the output occurs depending on the level of the input signal.

, this phase shift causes jitter in the detected timing signal, which is preferable and not necessary.

Particularly when the received signal is a multilevel pulse amplitude modulation signal, the range of variation in the level of the input signal to the double wave rectifier circuit is wide and the problem is serious.

In the above-mentioned two prior art technologies, there is also a prior art technology that uses a phase synchronized circuit instead of the narrow band filter and limiter that function to remove noise and stabilize the amplitude.

The ÷ method is superior to the method using a narrow band filter and limiter in that it is technically easy to narrow the band and the effect of constant amplitude is ideal, but on the other hand, the circuit The disadvantage is that it becomes complicated.

An object of the present invention is to provide a timing signal detection circuit that solves these problems.

, the timing signal output circuit of the present invention is intended for a pulse oscillation tone signal structure with a pulse repetition frequency fO, and includes a bandpass filter with a center frequency fO/2 and a nonlinear element having third-order nonlinearity. a nonlinear circuit having first and second high frequency signal terminals and a low frequency signal terminal coupled to the element, and a voltage controlled oscillator operating in a frequency domain centered on a frequency fo, The amplitude modulated signal is passed through the bandpass filter to the first one of the nonlinear circuit.
the output of the voltage controlled oscillator is also connected to a second high frequency signal terminal, and the signal obtained from the low frequency signal terminal of the nonlinear circuit is connected to the voltage controlled oscillator to control its frequency. It is characterized in that the output of the voltage controlled oscillator is extracted as a timing signal.

By using the present invention, it is possible to obtain a timing signal detection circuit that has little phase change due to level changes in a received signal and has little phase jitter.

Furthermore, a phase-locked circuit type timing signal detection circuit having a simple structure and having a nonlinear circuit in which the functions of a double-wave rectifier circuit and a phase comparator are integrated can be obtained.

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a conventional timing signal detection circuit.

A pulse amplitude modulated signal with a pulse repetition frequency fo applied from an input terminal 1 passes through a bandpass filter 2 with a center frequency of fo/2, and the positive and negative signals are folded back by a double-wave rectifier circuit 3, thereby generating a component with a frequency fO.

This component of fo is applied to the product type phase detector 4, where the phase difference between it and the output of the voltage controlled oscillator 5 having the center frequency fo is detected.

This detected phase error signal is subjected to noise removal by a low-pass filter 6, and is fed back to control the frequency of the voltage controlled oscillator in a direction that reduces the phase error.

The output of the voltage controlled oscillator is obtained from the output terminal 7 as a timing signal.

As mentioned above, in this conventional example, the phase shift characteristic depending on the input level of the double-wave rectifier circuit adversely affects the output multi-timing jitter, and the disadvantage is that the circuit is relatively complicated.

□FIG. 2 is a block diagram showing an embodiment of the present invention.

Component 1. 2. 5. 6. and 7 are the same as the conventional fiI: in FIG.

1 Reference numeral 800 is a nonlinear circuit including a nonlinear element having third-order nonlinearity: first and second high-frequency signal terminals 801 and 802, a low-frequency signal I-terminal 808, and a nonlinear element. It includes certain diodes 804 and 805.

Diode 804. The parallel circuits 805 and 805 exhibit third-order nonlinearity as shown by the voltage-current characteristic curve 9 in FIG. 3, where the horizontal axis represents the voltage and the vertical axis represents the current.

Reference numeral 803 is a duplexer that serves to couple a signal at a frequency near fo/2 at terminal 801 and a signal at frequency fo at terminal 802 to diodes 804 and 805.

Also resistor 806. Capacitor 807 is diode 804
．． The low frequency signal generated at both ends of 805 has a frequency f.

and a low-pass filter for separating the high-frequency signal near fO/2 and extracting it from the low-frequency signal terminal 808.

The operation of the timing signal detection circuit of this invention can be explained as follows.

Now, if the signal at terminal 801 is υ1 and the signal at terminal 802 is υ2, the element exhibiting third-order nonlinearity has υ1.
A voltage of 19□ is applied.

At this time, the current flowing through the nonlinear element is (υ1 +υ2)3=
υY +3υ〒υ2+3υ1υi+υContains the bud component.

That is, υ1 contains the fo/2 component, and υ2 is the output of the voltage controlled oscillator 5, so it contains the fO acid component.

Then, in each term after expanding (υ10υ2)3, the first term υt contains the (3fo/2) component, the second term 3υ υ2 contains the (fo±fo) component □, Third
The term 3υ, ・υ contains the (fo/2±2fo) component,
The fourth term, υ, includes a 3fo component.

Therefore, the term that includes low frequency components in this current is the second term.
It is easy to see that there are only terms υ and υb.

A low frequency voltage proportional to this current is obtained from terminal 808.

This term υ〒・υ2 is obviously equal to the product of the square of the output υ1 of the bandpass filter 2 (in other words, double-wave rectification) and the voltage-controlled oscillator output υ2, so the nonlinear circuit 800 It can be seen that the circuit functions as a combination of the double-wave rectifier circuit 3 and the multiplication phase detection circuit 4 in the Sakaki example of FIG. 1.

That is, from the terminal 808, a signal indicating the phase error between the signal obtained by squaring the signal at the terminal 801 and the signal at the terminal 802 is obtained, and a phase synchronization circuit is constructed as in the conventional example shown in FIG.

As described above, in the present invention, double-wave rectification and multiplicative phase detection are performed by one component, so the circuit configuration is simplified.

In addition, the voltage controlled oscillator output applied to the terminal 802 is connected to the terminal 80.
1, the effect of parasitic actance on the diodes 804 and 805 is averaged out, and the phase change depending on the input level can be suppressed to a sufficiently small value.

FIG. 4 is a circuit diagram showing another embodiment of the nonlinear circuit.

Components 801, 802, 804, 805, 806, 8
07,808 are the same as those in FIG.

In this embodiment, resistors 809, 810 are used instead of the duplexer 803 in the embodiment of FIG.
A circuit consisting of an amplifier 811 and an amplifier 812 is used.

This circuit is a well-known synthesis circuit in which the sum of signals applied to terminals 801 and 802 is connected to diode 804 .
The points added to 805 are completely the same as those in the previous embodiment, and it is clear that the present invention can be constructed using such a coupling means.

As explained above, by using the present invention, it is possible to obtain a timing signal detection circuit with a simple configuration and less jitter.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the prior art, FIG. 2 is a block diagram showing an embodiment of the present invention, FIG. 3 is a voltage-current characteristic diagram of the nonlinear element in the embodiment of FIG. 2, and FIG. is a circuit diagram showing another embodiment of the nonlinear circuit. In FIG. 2, 1 is an input terminal, 2 is a band pass filter having a center frequency of fo/2, 800 is a nonlinear circuit, 5 is a voltage controlled oscillator, 6 is a low pass filter, and 7 is an output terminal.

Claims (1)

[Claims] 1 A bandpass filter with a center frequency fo/2, which targets a pulse amplitude modulation signal with a pulse repetition frequency fo, and 3
a non-coconut circuit comprising a non-linear element having the following non-linearity and coupled to the element, first and second almond-frequency signal terminals and a low-frequency signal terminal; a voltage controlled oscillator operating in the frequency band, the pulse amplitude modulated signal being connected to a first high frequency signal terminal of the aphonic circuit through the bandpass filter, and the output of the voltage controlled oscillator also: A signal obtained from the low frequency signal terminal of the nonlinear circuit is connected to a second high frequency signal terminal, and a signal obtained from the low frequency signal terminal of the nonlinear circuit is connected to a voltage controlled oscillator for frequency control, and the middle power of the voltage controlled oscillator is extracted as an timing signal. Timing signal detection circuit with special punishment.