JPS5837130Y2 - phase detector - Google Patents

Description

[Detailed Description of the Invention] Conventionally, a balanced demodulator is used as a phase detector, and an example thereof is shown in FIG.

To explain this, la and lb are the input terminals of the signal to be phase-detected, that is, the signal to be detected Ea, 2 a and 2
b is an input terminal for a reference signal Eb having a reference phase; 3a;
and 3b, 4a and 4b, and 5a and 5b are transistor pairs forming a differential amplifier, 6 is a constant current source, 7 is a DC power supply, and 8a and 8b are output terminals for the detected signal. .

However, by passing the output of the lever through a low-pass filter (not shown), a detected signal can be obtained at the load.

However, as shown in FIG. 2A and B, the test wave signal Ea
When the reference signal Eb and the reference signal Eb are applied to the terminals 1a, lb and 2a2b, the output shown in FIG. (duty) will be different.

So-called phase detection is performed.

However, it is well known that in this case, the detectable range of the detected wave signal Ea is between +1 to 1 with respect to the reference signal Eb.

That is, as shown in FIGS. 2 and 3, when the detected wave signal Ea is out of phase with respect to the reference signal Eb (shown as orthogonal axis B in FIG. 3).

(hereinafter explained as a reference axis) is set to θ20, and in this state, the detection output Ee is set to 0 as shown in FIG. The output Ee is taken out based on the delay.

Therefore, as is clear from FIG. 4, the detection range is within the range of 11 to 0 to 10.

The present invention aims to further widen this conventional detection range, and an example of the phase detector according to the present invention will be described below with reference to FIG.

In the figure, 9 is an input terminal for the test wave signal Ea, and 10 is an input terminal for the reference signal Eb.

In the present invention, the reference signal Eb is supplied to a shift circuit, that is, a delay circuit 11, which shifts the phase by 7 lengths, and a phase change signal Ec is obtained at its output side.
and the test wave signal Ea are supplied to a mixing circuit 12, and a mixed signal Ed obtained by vectorial addition of both signals is obtained at the output side of the mixing circuit 12.

Furthermore, this mixed signal Ed is passed through a limiter 13, and its output is supplied to a phase comparator 14 for phase comparison, and an output is obtained from an output terminal 15.

In this case, the phase comparator 14 shown in FIG. 1 can be used.

According to this configuration, the mixed signal Ed obtained by vectorially adding the phase-shifted (for example, delayed) signal Ec and the test wave signal Ea for the length of the reference signal Eb is the vector shown in FIG. It is shown in the figure.

In this diagram, the signals Ec and Ea are shown with equal magnitudes.

However, θ in this case is the phase difference of the test wave signal Ea with respect to the reference axis B.

As is clear from this, the mixed signal Ed takes a phase angle φ with respect to the reference axis B, and when the magnitudes of the signals Ea and Ec are equal to each other, that is, when ECk=1 Ea, ψ=end. becomes.

Figure 7 shows the relationship between the phase angle θ and the detection output EC in this case, and it is clear from the introduction that detection is possible within the phase angle range of 11 to 0 to +T with respect to φ. Since it is clear that becomes.

In addition, FIG. 7 also shows the cases of k=0.0.5.2.

Figure 8 shows a case in which the present invention is applied to FM detection called a phase-locked loop used in magnetic recording and reproducing equipment (VTR), etc., and parts corresponding to those in Figure 5 are given the same reference numerals. Therefore, the explanation will be omitted.

In this example, the output from the oscillator 16 whose oscillation frequency is controlled by voltage is used as the reference signal Eb, and the frequency of the oscillator 16 is controlled by the output voltage obtained by passing the detection output through the low-pass filter 7.

18 is a variable attenuator. When this circuit is used in a VTR, an FM signal reproduced from a magnetic tape is applied to the terminal 9, and an oscillator 16 supplies a reference signal with a frequency equal to the carrier frequency of this FM signal.

Conventionally, the reproduced FM signal is directly supplied to the phase comparator circuit 14 and compared with the reference signal from the oscillator 16, and therefore the shift circuit 11. Although the variable attenuator 18, the mixing circuit 12 that performs vector addition processing, the limiter 3, etc. are not required, according to this, when broadband transmission is performed using a relatively low frequency carrier, the input terminal of the oscillator 16 Since a low-pass filter 17, that is, a time constant circuit, is inserted in the signal generator, if the original signal has many high-frequency components, a false signal is likely to be generated in the frequency band outside the detectable range (detection range) mentioned above. be.

However, according to the circuit shown in FIG. 8, the detection range is about twice as wide as that of the conventional one, so even if many high-frequency components are included as described above, there is no possibility of generating a false signal.

According to the present invention explained above, since the detection range can be widened, in other words, the degree of modulation can be increased when performing phase modulation, and the present invention has the characteristics of being able to perform demodulation with good linearity. It is something that you have.

[Brief explanation of the drawing]

Figure 1 is a connection diagram showing an example of a balanced demodulator used in conventional phase detection, Figure 2 is a waveform diagram of each part, Figure 3 is a vector diagram, and Figure 4 shows the relationship between phase θ and output. FIG. 5 is a block diagram showing an example of the phase detector according to the present invention, FIG. 6 is a vector diagram for explaining the same, and FIG. 7 is a curve diagram showing the relationship.
The figure is a curve diagram showing the relationship between the phase θ and the output, and FIG. 8 is a block diagram of another embodiment. Reference numeral 9 represents an input terminal for a test wave signal, and reference numeral 10 represents an input terminal for a reference signal.

Claims (1)

[Scope of utility model registration request] In a circuit that obtains a phase detection signal by comparing the phases of a test signal to be phase-detected and a reference signal having a reference phase, the phase of the reference signal is shifted by a predetermined amount, and this phase shift is A phase detector configured to compare the phases of a mixed signal obtained by mixing the detected signal and the detected wave signal with substantially equal amplitudes and vectorwise addition using the reference signal.