JPH02174345A - Orthogonal detector - Google Patents

Abstract

PURPOSE:To improve the accuracy of orthogonal detection by detecting a phase difference of two carrier signals given to each phase detector and controlling the phase shift of a variable phase shifter in response to the phase difference. CONSTITUTION:A carrier signal is given to a variable phase shifter 11, from which 1st and 2nd carrier signals are respectively formed and given to corresponding 1st and 2nd phase detectors 3, 4, where modulated signal and the 1st and 2nd carrier signals are subject to detection processing. The phase difference of the 1st and 2nd carrier signals given to the phase difference detectors 3, 4 is to be a reference phase difference of pi/2. The phase difference of the 1st and 2nd carrier signals is detected by a phase comparator 10 and given to the variable phase shifter 11 as a phase shift control signal to form a feedback control loop thereby making the phase difference of the 1st and 2nd carrier signals to be the reference phase difference of pi/2 independently of the change in the carrier frequency. Thus, the detection accuracy is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a quadrature detector, and is used, for example, in so-called FDMA (Frequency Detection) where the carrier frequency is frequently switched.
cy Division)
Access) (Applicable to a five-speed system receiving device.

[Conventional technology] Targeting digital data! ” ?) As a modulation method for MA transmission, 4 is a form of orthogonal modulation method.
Phase 5hirt Keyin
g) Some use a modulation method. Therefore, in such a transmission system, there is a 4-phase r-) on the receiving device side.
It is necessary to provide an SK demodulator. Figure 2 shows a conventional 4-phase PSK1. An example of a Q adjuster is shown (supervised by Moriji Kuwabara, [
Digital Microwave Communication J, published by Kikaku Center Co., Ltd., May 1980, 1) l) 111-114).

In Fig. 2, the received 4-phase P S
K modulated signals are input, and this modulated signal is branched into two identical modulated signals via a branch circuit 2, which are applied to corresponding first and second phase detectors 3 and 4, respectively.

On the other hand, a carrier wave signal having a predetermined frequency is input to the input terminal 5. This input carrier wave signal is transmitted to the branch circuit 6
is given to the same carrier wave signal, and the same two carrier wave signals are branched and outputted. One of the branched carrier wave signals (first carrier wave 1
3) is directly sent to the first (Il) phase detector 3. The other branched carrier wave 1J (second carrier signal) is obtained via the π/2 phase shifter 7. After being phase-shifted by π/2, it is applied to the second phase detector 4.

In this way, the first and second
The phases of the carrier wave signals differ by a reference phase difference π/2.

Each phase detector 3.4 is, for example, a so-called ring phase detector 2g. Each phase detector 3.4 multiplies the input modulated signal and the first or second carrier wave 13 inches to obtain a phase detection output No. 13 and outputs it to the corresponding output terminal 8.9. do.

In this way, the four-phase)) S K modulated signal is detected and the logic level is determined by the phase state at each point in time.
Obtain bit digital data, i.e. 4 phase 1) S
A K demodulated signal is obtained and output.

[Problem to be solved by the invention] As mentioned above, four-phase 1. ) In a quadrature detector such as a S K demodulator, the phase differs by the reference phase difference π/2.
A carrier wave signal is required, and in the case of many quadrature detectors, as mentioned above, the 1117 it carrier wave signal is split to form two carrier wave signals, one of which is phase-shifted by π/2. By doing so, two orthogonal carrier signals were formed.

It is used to form two orthogonal carrier signals.

As the π/2 phase shifter, a delay circuit, a π/2 branchler incoupler, or the like is used.

π formed by such delay circuits and branch line couplers, etc.
In the /2 phase shifter, the amount of phase shift generally varies from the reference amount of phase shift π/2 due to changes in carrier frequency.

For example, when applying the above-mentioned quadrature detector to a receiving device for FDMA transmission, it is necessary to vary the carrier frequency in response to channel changes. A phase shifter that shifts the phase by a phase shift amount π/2 is applied. If this transfer device is formed of a delay line such as a coaxial cable, the delay line attempts to achieve the same delay time in the range of change in carrier frequency. The phase shift amount for the channel carrier wave No. 13 is the reference phase shift amount π/2
It deviates from the Now, if the carrier frequency is changed by about 10 times from the carrier frequency of the center channel, the phase shift error caused by the π/2 phase shifter is (π/'2) x (1
, 1.

The present invention has been made in consideration of the following points:
．． The present invention aims to provide a quadrature detector that can improve detection accuracy by suppressing phase shift errors caused by a phase shifter provided to form two carrier signals that differ by a reference phase difference of π/2. be.

[Means for solving the problem 1] In order to solve the problem, in the present invention, the modulated signal is branched and applied to the first and second phase detectors, and the modulated signal is branched and applied to the first and second phase detectors.
A quadrature detector that detects the phase of the modulated signal using the first single-shell transmitted signal in the phase detector and detects the phase of the modulated signal using the second carrier signal in the second phase detector has the following configuration. Each part is provided.

That is, the phase comparator detects the phase difference between the first and second carrier signals, and the phase comparator detects the phase difference between the first and second carrier signals so that the reference phase difference is π/2. A variable shifter (11 detectors) is provided to shift the phase of the first and/or second one-shell transmission signal according to the phase difference obtained and output the shifted signal to the first and/or second phase detector.

[Operation] By passing the carrier wave signal through the variable phase shifter, the first and second carrier waves 18 are formed, and the corresponding first carrier wave 18 is formed.
and a second phase detector, and the modulated signal and the first and second carrier signals are subjected to detection processing in the first and second phase detectors, respectively.

It is desirable that the phase difference between the first and second carrier signals given to the first and second phase detectors be a reference phase difference of π/2. Therefore, a phase comparator detects the phase difference between these first and second carrier wave signals and provides it to the variable phase shifter as a phase shift amount control signal to form a feedback control loop, regardless of changes in the carrier wave frequency. The phase difference between the first and second carrier signals was always set to a reference value (+'f, phase difference π/2).

Embodiment] Hereinafter, the application of the present invention to a 1411 PSK demodulator will be described in detail with reference to the drawings.

Here, FIG. 1 does not show the Jt, +4 configuration of this example;
772, and the corresponding parts with Fig. 2 are marked with the same = - sign 5.
). Also, is Fig. 3 a phase comparison of this embodiment? FIG. 4 is a characteristic curve diagram showing the input/output characteristics of the phase shifter ii of this embodiment.

As shown in Fig. 1, the 4-phase 1'' SK converter A1 of this embodiment also basically transmits the 4-phase PSK modulated signal input via the input terminal 1 to the branch circuit 2. two fours by
1111' S K modulated signal is branched to the first
or to the second phase detector 3.4, in which the four-phase r'SK modulated signal and the first and second carrier signals having phases different from each other by π/2 are is subjected to detection processing, and the obtained detection output signals are outputted as 4-phase PSK demodulated signals from the corresponding output terminals 8.9.

In this embodiment, the first. A configuration is provided for controlling the phase difference between the second carrier wave and the second carrier wave to always be equal to the reference phase difference π/2.

That is, the first and second carrier signals given to the first and second phase detectors 3 and 4 are input j7,
and a phase comparator 1 that detects the phase difference between the second carrier signal and the second carrier signal.
0 is set. This phase ratio axis shifter 10 outputs a voltage signal according to the phase difference.

FIG. 3 shows the phase delay (phase difference) of the second carrier signal with respect to the first carrier signal detected by the phase comparator 10;
3 is a characteristic curve diagram showing a relationship with a voltage signal output by a phase comparator 10. FIG. As is clear from FIG. 3, when the phase difference is the reference phase difference π/2, the phase comparator 10
When the phase difference is smaller than the reference phase difference π/2, it outputs a voltage signal that increases positively along the cosine wave shape as the phase difference decreases, and the phase difference is based on π/2.
(When the phase difference is larger than π/2, a voltage signal that increases negatively along the cosine wave shape as the phase difference increases is output. In addition, in Fig. 3, the field sound whose phase difference is larger than π is also output. However, in practice, such a reference phase error π/
A phase difference with a large difference from 2 rarely poses a problem.

The voltage signal output from the phase comparator 10 in this manner is used as a signal for controlling the phase of the second carrier signal.

In the case of this embodiment, the second carrier signal is one of the carrier waves branched by the branch circuit 6 (the +i signal is transferred to the variable shifter 1
1 by approximately π/2. The variable phase shifter 11 receives the voltage signal output from the phase comparator 10 as a shift amount control signal via a loop filter circuit 12 having a low-pass filter circuit configuration. Change the amount of transfer depending on the situation.

That is, as shown in FIG. 4, the variable phase shifter 11 sets the reference phase shift amount π/2 as the phase shift amount when the voltage signal from the loop filter circuit 12 is 0, and sets the reference phase shift amount π/2 as the phase shift amount when the voltage signal from the loop filter circuit 12 is positive. As the value increases, the phase shift amount is made larger than the standard phase shift amount π/2, and when the voltage signal is negative, as the value decreases, the phase shift amount is made smaller than the standard phase shift amount π/2. .

Note that the reason why the voltage signal from the phase comparator 10 is not directly given to the variable phase shifter 11 but is given to the variable phase shifter 11 via the loop filter circuit 12 is because the voltage signal generated by the phase comparator 10 is In addition to removing unnecessary spectra and mixed noise through this loop filter circuit 12, the feedback loose control speed for controlling the phase difference between the first and second carrier signals is This is to provide a response at an appropriate speed, rather than a sudden response or a slow response.

In the above configuration, the first. for the carrier signal of
carrier wave signal has a phase difference φ larger than the reference phase difference π/2
1a.3 In this case, the phase ratio '
The l'x unit LO outputs a voltage signal of page value -vla corresponding to the phase difference φ1a according to the characteristic curve shown in FIG. This voltage signal (v 1 . a ) is filtered through the loop filter circuit 12 and then sent to the variable phase shifter 11 . At this time, variable phase shifter 11
is the input voltage chair number (-vLb; -vlb is -v
1. The amount of transfer is determined according to the filtered value of a). (1 phase shift point is smaller than π/2 (not shown in Figure 4)
1b.

Thus, when the phase difference between the first and second carrier signals is larger than the reference phase difference π/2, the variable phase shifter 11
A value smaller than #: quasi-phase shift ILπ/2 is set as the amount of phase shift, and the feedback system is applied so that the reference phase difference is π/2.

Moreover, the second carrier wave signal with respect to the first carrier wave signal is
Assume that the phase difference φ2a is smaller than the reference phase difference π/2. At this time, the phase comparator 10 outputs a voltage signal of positive M v 2 a corresponding to the phase difference φ2a according to the characteristic curve shown in FIG. This voltage signal (
v 2 a) is the roof.

After being filtered through the filter circuit 12, it is applied to the variable phase shifter 11. At this time, variable phase shifter 11
varies the phase shift amount to a value φ2b shown in FIG. 4, which is larger than the reference phase shift amount π/2, in accordance with the input voltage signal (V2+; v2b is the filtered value of v2a).

Thus, when the phase difference between the first and second carrier signals is smaller than the reference phase difference π/2, the variable phase shifter 11
A value larger than the reference phase shift amount π/2 is set as the phase shift amount, and feedback control is performed so that the reference phase difference becomes π/2.

Therefore, according to the above-described embodiment, the phase difference between the first and second carrier signals can be controlled to the reference phase difference π/2 at all times, and the detection accuracy can be improved from this point of view.

Furthermore, even if this embodiment is applied to an FDMA transmission system in which the carrier frequency changes frequently as the transmission channel changes, 1) since the phase difference control loop functions, the phase difference will be maintained despite fluctuations in the carrier frequency. The phase difference can be controlled to the reference phase difference π/2, and detection accuracy can be improved.

Note that in the above embodiment, the second
Although the variable phase shifter 11 is shown as being provided to form the first carrier signal, the variable phase shifter may be provided in order to form the first carrier signal on the phase leading side. Alternatively, two variable phase shifters may be provided to form one word of the first and second carrier waves. In short,
The present invention can be applied to a configuration in which a phase shifter is interposed so that two carrier wave signals whose phase difference satisfies the reference phase difference π/2 can be formed.

In addition, in the above-mentioned embodiment, the present invention is applied to a four-phase psK1
Although the present invention has been shown to be applied to an R modulator, it is of course applicable to other quadrature detectors.

Further, although the present invention is particularly effective when applied to a receiving device in which the carrier wave frequency is switched according to changes in the transmission channel, it can also be applied to a receiving device in which the channel is fixed, that is, the carrier wave frequency is fixed. Can be done.

[Effects of the Invention] As described above, according to the present invention, a variable phase shifter is applied as a phase shifter used to form at least one carrier wave signal, and two carrier wave signals given to each phase detector are Since the phase difference between the two carrier signals is detected and the phase shift amount of the variable phase shifter is controlled according to the phase difference, the phase difference between the two carrier signals can be adjusted to the reference phase difference π/2, which is always determined. Feedback control can be performed so that the quadrature detection can be performed, and the degree of orthogonal detection can be increased compared to the conventional method.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a block diagram showing an embodiment of a quadrature detector according to the present invention, FIG. 2 is a block diagram showing a conventional quadrature detector,
FIG. 3 is a characteristic curve diagram showing the input/output characteristics of the phase comparator 10 of the above embodiment, and FIG. 4 is a characteristic curve diagram showing the input/output 1, ν characteristics of the variable phase shifter 11 of the above embodiment. It is a v outer curve diagram. 1... Modulated signal input terminal, 2.6... Branch circuit,
3. 4... Phase detector, 5... Carrier wave signal input terminal, 8.9... Detection signal output terminal, 10... Phase ratio 1 articulator, output voltage signal 1... Variable phase shifter.

Claims (1)

[Claims] The modulated signal is branched and given to first and second phase detectors, and the first phase detector splits the modulated signal into a first phase detector.
detecting the phase difference between the first and second carrier signals; and a phase comparator in which the phase difference between the first and second carrier signals is a reference phase difference π
/2, the first and/or second carrier signals are phase-shifted according to the phase difference detected by the phase comparator and output to the first and/or second phase detector. A quadrature detector comprising a variable phase shifter.