JPH0226746B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting a phase difference between two bridge channels of a distributed constant circuit. Conventionally, as a method for detecting a phase difference between two channels using a bridge of a distributed constant circuit, for example, phase modulation is applied to the electrical signal of one channel, the synthesis of both signals, and the magnitude of the phase modulation frequency amplitude in the detection output and the phase difference are performed. There is a method that uses the relationship between the detection output and the phase difference, but when using this method over a wide range of frequencies above microwave, it is difficult to suppress the asymmetric component of amplitude modulation that parasiticizes phase modulation. The disadvantage is that the relationship depends on the amplitude ratio of both signals.

An object of the present invention is to provide a device that does not depend on the amplitude ratio of two channels of sine wave signals of a bridge circuit and detects the phase difference between both signals over a wide band.

The present invention will be explained below based on illustrated embodiments.

FIG. 1 shows that in the output signal from the oscillator 1,
This is an embodiment in which the phase difference between both signals passing through channel 3 and channel 4 is detected.

In this embodiment, the oscillator 1 is equipped with a low frequency oscillator 2 which performs frequency modulation of the output signal with a small frequency deviation using an output sine wave with a period T, and the channel 4 is connected to the output signal of the oscillator 1. A resonator 5 resonating at the center frequency is installed, and a detector 6 is provided on the output side where channels 3 and 4 join, and a synchronous detector 7 is connected to the detector 6.

In the above configuration, the output signal of the oscillator 1 is frequency modulated by the output sine wave of the low frequency oscillator 2 and sent to channels 3 and 4. A signal (vector 8) from the channel 3 and a signal (vector 9) from the channel 4 through the resonator 5 are input to the detector 6, where they are combined and detected.

Here, the frequency dependencies of the propagation characteristics in the signal path of vector 8 and the signal path of vector 9 are very different in the vicinity of the center frequency. In other words, the one related to vector 8 has a slow frequency versus phase characteristic such as the line of channel 3, whereas the one related to vector 9 has a steep frequency versus phase characteristic near the resonance frequency (=near the center frequency) due to the resonator 5. have characteristics. Therefore, when the output frequency of the oscillator 1 is frequency-modulated by a sine wave with a period T as described above, the phase of the vector 9 changes rapidly compared to the phase of the vector 8. Therefore, when vector 8 is used as a reference, vector 9 changes as shown by the dotted line in the vector diagram of FIG.

In the vector diagram above, θ is equal to the resonant frequency of the oscillator (in the example of Fig. 2, t
= T/4 or 3T/4), vectors 8, 9
FIG. 2a shows the situation when θ≠0 degrees, and FIG. 2b shows the situation when θ=0 degrees.

By the way, the output of the wave detector 6 depends only on the amplitude of the composite vector of the vectors 8 and 9, but the output waveforms are different in FIGS. 2a and 2b. That is, in the case of Fig. 2a, the vector 9 changes with respect to the vector 8 during the period T as shown in the vector diagram, so the output period of the detector 6 becomes T as shown in Fig. 2a. .

On the other hand, when θ=0 degrees, as shown in the vector diagram, the vector 9 changes symmetrically with respect to the vector 8 during the period T, so the detector 6
The output period is T/2 as shown in FIG. 2b. That is, in FIG. 2b, the modulation frequency component (period T) disappears. This relationship holds true regardless of the magnitude of vectors 8 and 9, and a similar relationship holds true for θ=180 degrees.

Therefore, by observing 0 of the modulation frequency component (period T) in the output component of the detector 6 with the synchronous detector 7, it is possible to detect θ=0 degrees or 180 degrees.

That is, according to the present invention, a phase difference θ=0 degrees or 180 degrees can be detected by observing the modulation frequency component regardless of the amplitude ratio of both signals of channels 3 and 4.

Examples will be sequentially described below. FIG. 3 shows an embodiment using a reaction type resonator, in which the circulator 13 and the reaction type resonator 14 form the resonator 5 of FIG. In this embodiment, the frequency of the oscillator 1 is also controlled by utilizing the pass characteristics and frequency modulation of the resonator.In this embodiment, the amount of phase shift between the standard phase shifter 16 and the phase shifter 17 to be measured is compared.
FIG. 4 shows an example of an attenuation measuring device using homodyne detection. When measuring attenuation, always use phase shifter 1 to set the phase difference between the two channels to 0 degrees or 180 degrees.
You need to use 6 to match. In this embodiment, a resonator 5 is used, a synchronous detector 7 detects the presence or absence of a modulated frequency component, a motor 25 is used, and a standard phase shifter 1 is used.
6 will be automatically adjusted.

FIG. 5 shows an example of an apparatus for simultaneously measuring attenuation and phase shift. In this device, the configuration of the high frequency circuit is the same as that shown in FIG. 4. When the amplitude of the electrical signal of the channel of the device under test 28 is |E|, and the phase difference between both channels is θ, |E|cosθ and |E|sinθ However, in this embodiment, the frequency component of frequency modulation is proportional to |E|sinθ, and the frequency component of amplitude modulation by the amplitude modulation oscillator 23 is proportional to |E|cosθb. are doing. FIG. 6 shows a circuit for measuring the amplitude and phase of the reflection coefficient using a Magic T.

As described above, the present invention is a device that uses frequency modulation and a resonator to detect the phase difference between two channels of a bridge circuit of a distributed constant circuit.
Since the phase difference can be detected without depending on the amplitude ratio of two electrical signals, and the resonator can also be easily used for frequency control, this invention makes it easy to detect the phase difference, especially in microwave and millimeter waves. The effect of being able to perform this over a wide range of time and over a wide band is extremely large.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the circuit configuration, Figure 2 a and b is a diagram of the vector relationship between two signals and the detector output waveform, Figure 3 is an application diagram for phase shifter measurement, and Figure 4 is for attenuation measurement. FIG. 5 is an application diagram of attenuation and phase shift measurement, and FIG. 6 is a magic circuit diagram. In the figure, 1 is an oscillator, 2 is a low frequency oscillator, 3, 4
is a branch line (channel), 5 is a resonator, 6 is a wave detector, 7 is a synchronous detector, 8 is a signal vector of channel 3, 9 is a signal vector of channel 4, 12 is a matching unidirectional tube, 13 is a circulator , 14 is a reaction type resonator, 15 is a matching attenuator, 16 is a standard phase shifter, 17 is a phase shifter to be measured, 19 is a narrow band amplifier (center frequency is the same as 2), 21 is a narrow band amplifier ( 23 is a low frequency oscillator for amplitude modulation, 24 is an attenuator to be measured, 25 is a motor for driving a phase shifter, 26 is a low frequency attenuation measurement device, 27 is an amplitude modulator, 28 is a 29 is an amplitude phase display device (such as an XY recorder); 30 is a magic T; and 31 is a reflector to be measured.

Claims (1)

[Claims] 1. A device for detecting the phase difference between the channels using a bridge of a distributed constant circuit having two channels for a power supply signal, comprising means for frequency modulating the power supply signal with a periodic function signal,
Further, a resonator that resonates at the center frequency of the power signal is installed in one of the channels, and a detector that combines and detects the signals of both channels and detects the modulated frequency component in the output of the detector. A phase difference detection device characterized by comprising a synchronous detector.