JPH02272910A - Automatic 1/4 period phase shifting circuit - Google Patents

Abstract

PURPOSE:To save labor for check and adjustment by loading feedback to a phase shifter and automatically holding phase difference for a 1/4 period, namely, for pi/2. CONSTITUTION:For an integration circuit 3 and phase shifter 2, the phase difference of the pi/2 is applied between respective signals when a voltage corresponding to an integral constant is applied to the phase shifter 2 at the time of initial setting. At such a time, when the phase difference between the both signals is deviated from the pi/2, a direct current component corresponding to phase quantity deviated from the pi/2, namely, the phase difference to appear between respective output terminals 7 and 8 is automatically set to the pi/2 and even when fluctuation is generated, correction is automatically executed. Thus, the labor is saved for executing the check and adjustment.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a phase shift circuit used in general analog circuits for communication equipment, and in particular to a 4-phase PSK system, 16 or 64
The present invention relates to a 174-cycle phase shift circuit used when performing a QAM method such as QAM.

[Prior Art] FIG. 3 is a diagram showing a circuit configuration of a conventional phase shifter of this kind.

The signal output from the oscillator (OSC) 30 is transmitted to the resistor 31.
After passing through, it is branched and outputted from the first output terminal 41 and the second output terminal 42.

Resistors 38 and 39 are provided in series between the resistor 31 serving as one signal line and the first output terminal 41, and a resistor 40 is provided between the connection point of these resistors 38 and 39 and the ground. ing. In addition, the resistor 31 which becomes the other signal line and the second
A coil 31 and a resistor 37 are connected in series with the output terminal, and capacitors 33 and 3 are connected in parallel with the ground.
4. A resistor 36 and a T-variable capacitor 32 are provided.

Conventionally, creating a phase difference between the signals appearing at the first output terminal 41 and the second output terminal 42 is achieved by using the variable capacitor 32.
This is done by manually changing the capacitance of the coil 31, and changing the transfer characteristics and phase characteristics determined by the inductance of the coil 31, the capacitance of each capacitor, and the resistance value of each resistor. The user uses the second output terminal 4
Adjust the capacitance of the variable capacitor 32 while looking at the measuring device (such as a peltol portometer) so that the signal appearing at the first output terminal 41 has a phase difference of 174 cycles (π/2) with respect to the signal appearing at the first output terminal 41. I was adjusting.

[Problems to be Solved by the Invention] The conventional phase shifter described above is configured to manually adjust the capacitance F11 of the variable capacitor. For this reason, the user must make adjustments while visually observing the phase difference appearing between each output terminal using a measuring instrument or the like, which has the disadvantage of being time-consuming. Further, even if the temperature has been adjusted by -degrees, if the characteristics change due to temperature changes, disturbances, etc., the adjustment must be made again, which is troublesome.

In the present invention, the phase difference appearing between each output terminal is automatically reduced to 1
It is an object of the present invention to provide an automatic 174-cycle phase shifter that has 74 cycles (π/2) and is automatically corrected even when fluctuation occurs.

[Means for solving the problem] A first signal output terminal and a second signal output terminal that output a signal sent out from an oscillator, and a signal sent out from the oscillator to the first and second signal output terminals. a first transmission line and a second transmission line that transmit data, and a first transmission line and a second transmission line provided on either one of the first and second transmission lines,
a phase shifter that changes its capacitance in accordance with a control voltage applied from the outside, and adjusts the phase difference between each signal appearing at the first and second signal output terminals by the change in the capacitance; A mixer that manually inputs each signal appearing at the signal output terminal, and a mixer that manually inputs the output of the mixer and indicates whether the phase difference is larger or smaller than π/2 using a DC component. It has a low-pass filter for passing the low-pass filter, an amplifier for amplifying the low-pass filter output, and an integrating circuit that inputs the output of the amplifier and sends an output voltage obtained by integrating this value to the phase shifter as a control voltage.

[Operation] As the above-mentioned integrating circuit and phase shifter, one is used that provides a phase difference of π/2 between each signal when a voltage corresponding to the integration constant is applied to the phase shifter in the initial state. do. After this, if the phase difference between the two signals deviates from π/2 due to temperature changes or disturbances, a DC component voltage corresponding to the phase amount deviating from π/2 is output from the low-pass filter, and the integrator circuit is this voltage if the phase difference between both signals is π/
Continue for 1 minute until it reaches 2. Therefore, the phase difference between both signals is automatically maintained at π/2.

[Example] Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit block diagram showing the configuration of an embodiment of the present invention.

This embodiment includes an oscillator 1, a phase shifter 2, an integrator 3, and an amplifier 4.
, a low-pass filter 5, a mixer 6, a 111th output terminal 7, and a second output terminal 8.The signal output from the oscillator 1 is split into two and output from the first output terminal 7 and the second output terminal 8. and gives a phase difference of I74 periods (π/2) between the signals appearing at each of these output terminals.

Among the branched outputs of the oscillator 1, one is transmitted to the first output terminal 7, and the other is at an order of I74 period (π/2) with respect to the output transmitted to the first output terminal 7. Phase shift′ provided to provide a phase difference? The signal after passing through S2 is transmitted to the second output terminal 8. Note that this phase shifter 2 is capable of controlling the phase shift j1t.

The mixer 6 inputs the signals transmitted to the first output terminal 7 and the second output terminal 8, and outputs a voltage according to the phase difference between them.
After passing through an amplifier 4 and an integrator 3, it is applied to a phase shifter 2, and the phase shifter 2 adjusts the phase amount according to the output.

FIG. 2 is a circuit diagram showing a specific configuration of the embodiment shown in FIG. 1.

The output of the oscillator 1 is branched after passing through a capacitor 15 and a resistor 28. -Resistor 28 serving as a force signal line
A resistor 27.25 and a capacitor 20 are provided in series between and the first output terminal 7, and a resistor 26 is provided between the connection point of these resistors 27.25 and the ground. There is.

Also, a resistor 28 serving as the other signal line and a second output terminal 8
A coil 13, a resistor 24, and a capacitor 19 are sequentially provided in series between the resistor 28 and the coil 13, and the resistor 28 and the coil 13 are grounded via the capacitor 16. The coil 13 and the resistor 24 are connected to ground via a capacitor 17 and a resistor 21, respectively, which are provided in parallel, and further connected to the anode of a varactor diode 12 for adjusting the phase difference. The mixer 6 inputs the voltage between the resistors 27 and 25 and the voltage between the coil 13 and the resistor 24, and outputs a mixture of these. The operational amplifier 10 is provided between the mixer 6 and the varactor diode 12, and its negative input terminal receives the output of the mixer 6 via a resistor 23, and its positive input terminal is grounded. A capacitor 18 is connected in parallel between the negative input terminal and output terminal of the operational amplifier 10.
and a resistor 22, the output of which is applied to the cathode of the varactor diode 12 via the coil 14.

The resistance value of each resistor, the capacitance of each capacitor, and the inductance of the coil are selected so as to be locked when the phase difference between the signals appearing at the first output terminal 7 and the second output terminal 8 is π/2. ing.

The low-pass filter 5, amplifier 4, and integrator 3 shown in FIG. 1 are replaced with an active filter using an operational amplifier 10. The varactor diode 12, which corresponds to the phase shifter 2, changes its capacity according to the voltage difference between its anode and cathode.The output of the operational amplifier 10 changes the capacity of the varactor diode 12, changing the transfer characteristics. things will be done.

Next, the operation of this embodiment will be explained.

The signal appearing at the first output terminal 7 which is input to the mixer 6 is designated as As1nω, and the signal appearing at the second output terminal 8 is designated as Bs1.
Let n(ωL+φ). [However, ω is the angular velocity and φ is the phase difference] The output of the mixer 6 is As1n ωt x Bs1n (ω+φ) = π/
2 A B (cosφ−cos(2ωL+φ)). Next, this output passes through the low-pass filter 5 and is expressed as 1/2 A B (cosφ−cos(2ωt, +φ)
) = 1/2cA Bosφ. When this is passed through an integrator 3 with a time constant of τ, 1/2 AC (Is φdL= π/2 Ac
os φ・τ+α. α is an integral constant, and the phase difference when this circuit is locked is φ = π/2, so
The operational amplifier lO outputs a voltage equal to this integral constant α.

In the initial state, the varactor diode 12 has a capacitance that causes a phase difference of π/2 between the signals appearing at each of the first output terminal 7 and the second output terminal 8 when the two integral constants α are added. Become.

In this way, the output of the mixer 6 is passed through the low-pass filter 5 to become a DC component, and further passed through the integrator 3, where it is converged toward the integral constant α.

Regarding the operation of each part of this circuit configured as above,
Indicate voltage fluctuations as positive and negative to adults.

Table 1 As mentioned in Table 1, the integrator 3 installed after the amplifier 4 integrates a constant voltage until the phase difference between each signal appearing at the first output terminal 7 and the second output terminal 8 reaches π/2. However, when the phase difference reaches π/2, that voltage is held.

After that, due to temperature fluctuations, disturbances, etc., the phase difference
If it deviates from 2, the above operation is repeated.

[Effects of the Invention] As explained above, the present invention provides feedback to the phase shifter to automatically maintain a phase difference of 1/4 period, that is, π/2, thereby facilitating inspection and adjustment. This has the effect of saving time and effort and making it possible to achieve maintenance-free operation thereafter. The circuit according to the present invention is very simple and does not require a large number of parts, and the frequency band can be increased as high as the mixer allows, so it has a wide range of applications.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a circuit diagram showing the specific configuration of FIG. 1, and FIG. 3 is a diagram showing the configuration of a conventional example. 1... Oscillator, 2... Phase shifter, 3...
Integrator, 4... Amplifier, 5... Low pass filter, 6... Mixer, 7... First output terminal, 8...
...second output terminal, 10-... operational amplifier, 13.
14--Coil, 15-20--Capacitor, 21-28--Resistance. Figure 1 Figure 3 Figure 2

Claims (1)

[Claims] 1. a first signal output terminal and a second signal output terminal that output the signal sent out from the oscillator; and a first transmission that transmits the signal sent out from the oscillator to the first and second signal output terminals, respectively. line, a second transmission line, and one of the first and second transmission lines, the capacitance of which is changed according to a control voltage applied from the outside, and the capacitance of the first and second transmission lines is changed by the change in capacitance. a phase shifter that adjusts the phase difference of each signal appearing at the second signal output terminal; a mixer that inputs each signal that appears at the first and second signal output terminals; a low-pass filter that passes only a DC component indicating whether the phase difference is larger or smaller than π/2; an amplifier that amplifies the output of the low-pass filter; and an amplifier that amplifies the output of the amplifier. an automatic 1/4 period phase shift circuit comprising: an integration circuit that inputs an output voltage and integrates this value and sends an output voltage to the phase shifter as the control voltage.