JPH0457408A - Variable phase circuit - Google Patents

Abstract

PURPOSE:To facilitate phase adjustment and to vary the phase continuously and considerably by comparing an integration signal of an input signal with a variable reference voltage being an external control signal and inputting the comparison output to a flip-flop circuit having set and reset terminals. CONSTITUTION:The variable phase shift circuit consists of an integrating circuit 1 integrating an input signal linearly, two variable reference voltage sources (control voltage sources) V1, V2, a comparator 2 comparing an integration output (b) with the reference voltage V1 and outputting an output signal (c), a comparator 3 comparing the integration output (b) with the reference voltage V2 and outputting an output signal (d), and a flip-flop 4 having set and reset terminals receiving the result of comparison. The delay in the output signal (c) is small when the external control voltage V1 is small and the delay in the output signal (c) is large when the external control voltage V1 is large, then the phase is varied in a range of 90-180 deg.. The phase of an output signal (d) is shifted by just 180 deg. with respect to the output signal (c) by selecting the external control voltage V2 to be V2+-V1. Then the signals c, d generated from both the comparators 2, 3 are inputted respectively to a set terminal S and a reset terminal R of the flip-flop 4, and the result is outputted from points e, f.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a variable phase circuit, and particularly to a variable phase circuit that can continuously and arbitrarily vary the phase of a clock signal or the like by an external control signal.

[Prior Art] As a method of changing or adjusting the phase of a signal,
It is common to use a phase shift circuit composed of passive elements such as resistors, capacitors, or inductances. For example, as shown in Fig. 6, a phase shift circuit composed of resistor R and capacitor CI, and resistor R2 and capacitor C2 is used. The two integrating circuits are connected in series, and in response to a 45° input applied to the connection point, a phase-shifted waveform is obtained from the output of each integrating circuit.

Further, a phase shift circuit (variable phase circuit) using an active element generally changes the phase by changing the impedance.

There is also a method of changing using a delay line. This is done by using distributed constant lines such as strip lines and changing their lengths (FIG. 7). Similarly, by changing the lengths of coaxial cables, the phase can also be changed.

Furthermore, in the case of a digital signal, by passing the signal through a gate circuit or the like, the phase of the input signal can be delayed by that amount by utilizing the propagation delay time of the gate circuit. Therefore, by changing the number of connected gate circuits, the delay time, that is, the phase can be changed (FIG. 8).

[Problems to be Solved by the Invention] However, in the case of a phase shift circuit using passive elements such as capacitors and inductances as shown in Fig. 6, in order to change the phase, it is necessary to change the value of each passive element. It is necessary to change. The only way to do this is to replace the element with one with a different constant, or to adjust it using a variable element (volume, etc.), which is not only difficult to adjust, but also difficult to vary over a wide range. . Furthermore, capacitors and inductances are not suitable for use in ICs to meet the demand for miniaturization.

Next, phase shift circuits using active elements have the disadvantage that they cannot be applied to circuits that do not like changes in impedance because they change the impedance, and that the linearity of the amount of phase shift is poor.

Furthermore, with the method of adjusting the phase by changing the length of a distributed constant line such as a stripline or coaxial cable, it is difficult to continuously change the amount of phase shift, and if a large amount of shift cannot be obtained, , requires that much length,
Difficult to downsize.

Further, since only absolute time delays are possible, for example, if you want to shift the phase by 10', you have to calculate the delay time for each signal frequency and change the length, which is a hassle. Furthermore, the amount of phase shift cannot be controlled by an external signal.

In the method shown in Figure 8, in which the phase is shifted by the propagation delay time of the gate circuit, the amount of shift can only be changed in steps. Due to variations in
There is a drawback that the amount of phase shift changes.

An object of the present invention is to provide a novel variable phase circuit that eliminates the drawbacks of the conventional phase shift or phase variable techniques described above, and that allows the phase to be varied continuously and significantly, and furthermore, the amount can be controlled by an external signal. The goal is to offer.

[Means for Solving the Problems] The variable phase circuit of the present invention includes an integrator circuit that linearly integrates an input signal, and first and second integrator circuits that compare the integrated output of the integrator circuit with a reference voltage and output an output signal. a comparator, and a flip-flop having a set and reset terminal that uses this output signal as a set and reset signal, and controls the amount of phase shift of the output of the flip-flop circuit by adjusting one of the reference voltages. belongs to.

The integration circuit may be constructed so that the time constant of the integration circuit is changed by using a diode junction capacitance or a varicap as the capacitance forming the integration circuit.

Furthermore, the other reference voltage of the comparator may be adjusted to control the duty ratio of the output of the flip-flop circuit.

[Operation] The variable phase circuit of the present invention changes the phase, compares a signal obtained by integrating the input signal with a variable reference voltage that is an external control signal, and inputs the output to a flip-flop circuit having set and reset terminals. . Since it is a variable phase circuit in which the amount of phase shift can be controlled by an external control signal and furthermore the duty of the output can be arbitrarily controlled, phase adjustment is easy and the amount of phase change can be greatly improved.

In addition, the propagation delay time of the comparator and flip-flop circuit is
Added to the phase as absolute time. Phase change range is 90~1
Although the angle is 80°, if the rise and fall times are long, it will not work near 90° or 180°.

[Example] An example of the present invention is shown in FIG. This variable phase circuit is
Basically, it is constructed using active elements such as transistors.

This variable phase circuit consists of an integrating circuit 1 that linearly integrates an input signal, and two variable reference voltage sources (control u4 voltage sources) Vl, V
2, a comparator 2 that compares the integral output of the integrator #Il with this reference voltage v1 to obtain an output signal C, and a comparator 3 that also compares the integral output S with the reference voltage v2 to obtain an output signal d.
and a flip-flop 4 having a set/reset terminal for receiving the comparison result. The output signal C of the comparator 2 is used as a set signal for the flip-flop 4, and the output signal d of the comparator 3 is used as a reset signal.

The integrator 1 is composed of an operational amplifier A, resistors RS, Rf, and a capacitor Cf. This time constant is determined by Cf and Rf, and becomes f=1/2πCf Rf.

The outputs of the integrator 1 are input to the non-inverting input terminals (+ side terminals) of the comparators 2 and 3, respectively.

Each comparator 2.3 determines the control voltage V1. V2 is compared with the output signal of the integrator, and the result is input to the set terminal S and reset terminal R of the flip-flop 4.

Flip-flop 4 is a D-type mask slave.
It is a flip-flop and operates according to the logic shown in FIG. 2, and the results appear as outputs e and f from the Q and Q terminals.

Next, the operation will be explained.

FIG. 3 shows waveforms at various parts when a square wave is input as an input signal to the variable phase circuit (FIG. 1). (a>
is a square wave signal input to input terminal a of the variable phase circuit,
(b) is the integrated voltage waveform appearing at point b of the variable phase circuit, (
c) (d) shows the output waveform of the comparator 2.3, and (e) shows the waveform of the Q output e of the flip 70 tube 4.

The amplitude (peak-to-peak value) of the triangular wave generated at the output of the integrator 1 is set to 2Vo, and the reference for the control voltage VIV2 is set to the center of the amplitude of this triangular wave, that is, the average value of the triangular wave.

First, the integrated voltage appearing at point b (FIG. 3(b)), that is, the comparator 1. The non-inverting input (+ side input) of the comparator 2 is a square wave signal input to the input terminal a of the variable phase circuit (see Fig. 3).
It becomes an undistorted triangular wave synchronized with a)). By making it a triangular wave without distortion, external control tX] voltages Vl, V2
Comparison control becomes possible.

Of these two comparators 2 and 3, the rising edge of the output of one comparator 2 (Fig. 3 (C)) is 90° + 90° x ( V
l/Vo) to be far behind. That is, when the external control voltage v1 is small, the amount of delay is small, and when the external control voltage is large, the amount of delay is large. That is, the phase can be varied from 90° to 180°.

In the other comparator 3, the external control voltage V2 is set to V2
= -Vl, the output C is 18 degrees
A signal d shifted by 0° is obtained (FIG. 3(d)).

Therefore, by inputting the signals C and d generated in both comparators 2.3 to the set terminal S and reset terminal R of the 7-lip-flop, the results are output from points e and f according to the truth shown in Fig. 2. . The output result at point e is shown in FIG. 3(e).

Although the phase is already delayed at the output of the 0 point, the duty ratio of the signal changes depending on the phase. Therefore,
In order to obtain a signal whose duty ratio does not change even if the phase is delayed, as shown in FIG.
The duty ratio is adjusted by controlling the voltage. When Vl = -V2, the duty ratio is 50%.

The amount of phase change can be varied within the range of o<vi<vo, and therefore can be varied from about 90' to 18o. Therefore, by connecting this circuit in four or more stages, O°~3
Phase adjustment of 60° is also possible.

Integrator 1 shown in FIG. 1 above. Comparator 2.3 can also be constituted by a differential amplifier circuit.

This is shown in Figure 4.

Further, the capacitor Cf in FIGS. 1 and 4 may have a structure in which the capacitance is varied by using the junction capacitance of a diode as shown in FIG. 5 and controlling the voltage applied to the diode. A similar effect can also be obtained by using a varicap. In this way, the time constant can be optimally controlled over a wide range of frequencies using an external voltage. Therefore, the integrator, comparator, and flip-flop can be made into a monolithic IC.

[Effects of the Invention] As described above, according to the present invention, it is possible to continuously change the amount of phase shift, which cannot be achieved with a phase shift circuit using passive elements or active elements, and to change the amount of phase shift over a wide input frequency range. They have the same phase variable width and can easily control the phase shift amount from the outside.

Further, the circuit can be easily made into a monolithic IC, and can be significantly miniaturized compared to conventional phase shifters, and a variable phase circuit can be realized that has less variation in response to power supply voltage fluctuations and IC process fluctuations.

Therefore, this variable phase circuit is suitable for adjusting the phase of clock and data for optical communication, for example.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the variable phase circuit according to the present invention, FIG. 2 is a diagram showing the true structure of the D-type master-slave flip-flop, and FIG. 3 is a diagram showing an embodiment of the variable phase circuit according to the present invention. 4 is a diagram showing another embodiment of the present invention, FIG. 5 is an example of diode junction capacitance, and FIG. 6 is a diagram showing a conventional passive element. FIG. 7 is a diagram of the phase shift circuit used, FIG. 7 is a diagram of a phase shift circuit using a conventional delay line, and FIG. 8 is a diagram showing a phase delay method using a conventional gate circuit. In the figure, 1 is an integrator, 2.3 is a comparator, and 4 is a flip-flop. Patent Applicant Hitachi Cable Co., Ltd. Patent Attorney Nobuo Kinutani Figure 1 Separator Comparator Comparator Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] 1. An integrating circuit that linearly integrates an input signal, first and second comparators that compare the integrated output of this integrating circuit with a reference voltage and output an output signal, and A variable phase shifter comprising: a flip-flop having a set terminal, a set terminal for a reset signal, and a reset terminal, and the amount of phase shift of the output of the flip-flop circuit is controlled by adjusting one of the reference voltages. circuit. 2. The variable phase circuit according to claim 1, wherein the time constant of the integrating circuit is changed by using a diode junction capacitance or a varicap as the capacitor constituting the integrating circuit. 3. The variable phase circuit according to claim 1, wherein the duty ratio of the output of the flip-flop circuit is controlled by adjusting the other of the reference voltages.