JPS61208345A - Synchronous supervisory device - Google Patents

Abstract

PURPOSE:To transmit the synchronizing state of a reference carrier surely even under high noise level by constituting the titled device with the 1st detecting means outputting a detection signal when a detection output is received near a normal signal position, the 2nd detection means at a position other than the vicinity of signal position and a comparision means comparing a means value of output of each means. CONSTITUTION:When a 4-phase PSK signal enters two supervisory devices and a reference carrier is synchronized, the relation of means output values is the 1st supervisory device 3 > 2nd supervisory device 3' regardless of the quantity of input noise. On the other hand, since four signal points are turned around the origin at the asynchronizing state of the reference carrier, the mean output value is expressed as 1st supervisory device = 2nd supervisory device independingly of the quantity of input noise similarly. Each means output is obtained from lowpass filters 4, 4'. The synchronization of the carrier is identi fied by the quantity of means output of the two supervisory devices.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a technique for monitoring the synchronization of a phase modulated wave, an amplitude phase, and a reference carrier wave necessary for coherent detection demodulation of a modulated wave.

(Conventional technology and gap between them) Two-phase and four-phase phase keying (PSK) have been used for a long time for carrier band digital transmission, and in recent years, they have become widely used mainly in terrestrial microwave bands. Quadrature Amplitude Modulation
Modulation (QAM). For these demodulations, a synchronous detection method is used because it has excellent noise characteristics.

The synchronous detection method requires a reference carrier to be synchronized with the transmitting carrier. Only when the synchronization of the same carrier waves is established, the receiving side can observe the same transmitted code as the transmitting side, and if there is a difference in the same wave number of Δf (Hz) between the transmitting and receiving carrier waves, the reception On the other hand, a transmitted code space that rotates at a speed of Δf per second is observed. Therefore, if the noise is not very noticeable, the synchronization state can be detected relatively easily by checking whether the demodulated signal point after coherent detection is observed at the correct position. Publicly known examples of these are 1975 1
Materials published by the President of Electronic Communications and Communication Methods Study Group (October 290) (
C875-12) [Seen in hybrid modulation/demodulation device 1 for satellite communication.

A block diagram of an embodiment of a conventional synchronization monitoring device is shown in FIG. The carrier band input signal is sent from the terminal 90 to the synchronous detector 1.
The in-phase and quadrature components are respectively digitized by analog-to-digital converters 20.21 and sent to terminals 100.101.
be sent to Here, the synchronous detector 1 includes a multiplier 12, 13, a low-pass filter 14, 15, a half-tilt phase shifter 11, and an oscillator 10 that generates a reference carrier wave. 3 is a read-only memory (ROM),
Recognizes the two-dimensional code space using the digitized in-phase and rectangular coordinates from terminals 100 and 101, and outputs [1] when an address corresponding to the vicinity of a regular signal point is applied, and at other times. It outputs zero. Example of contents of read-only memory for 4-phase phase modulated wave Figure 3 (a)
.

Shown in (b).

The four shaded areas in FIGS. 3(a) and (b) are the four signal points exp(i7L/4) and exp(j3) of the 4-phase PSK.
x/4), exp(j5x/4), expθ7/
4) Covers. This memory works as a monitoring device to monitor the synchronization status of the synchronous detector. The output of the memory 3 is smoothed by a low-pass filter 4, and applied to a comparator 5. When an output of a certain value or more is obtained from the low-pass filter 4, it is recognized as a synchronized state, and the output terminal 91 outputs a judgment value. Output.

In this case, as the noise increases, the distribution of received signal points increases, and even in the synchronized state, as shown in Fig. 3(a),
From the sloped line part in (b), no reception signal is received, making it very difficult to distinguish it from an asynchronous state.

(Object of the Invention) An object of the present invention is to provide a synchronization monitoring device that reliably transmits the synchronization state of a reference carrier wave even under a high noise level.

(Structure of the Invention) According to the present invention, there is provided a synchronous monitoring device to which a synchronous detection output of an amplitude phase modulated wave is supplied, wherein (a) detection is performed when the detection output is received near a regular signal point position; a first detection means for outputting a signal; (b) a second detection means for outputting a detection signal when the detection output is received at a position other than the vicinity of the regular signal point position; (c) the first detection means; and comparing means for comparing the average value of the output of the second detection means with the average value of the output of the second detection means.

(Detailed Description of Configuration) Next, the present invention will be described in detail with reference to the drawings. The main reason why the conventional embodiment loses accurate discrimination ability as the input noise level increases is that the threshold of comparator 5 in FIG. 2 is fixed. In other words, the received signal point distribution increases as the input noise increases, and as a result, the probability that memory 3 outputs 1 decreases, but there is no structure to lower the comparator threshold in response to this. be. However, if the threshold value of this comparator is lowered too much, a state in which this threshold value is exceeded will occur even in an asynchronous state, and it can be said that effective synchronous monitoring cannot be performed after all. In order to overcome this drawback, the present invention provides two types of monitoring devices and performs synchronous monitoring based on the relative levels of the two outputs of the devices.

(Embodiment) FIGS. 1(a), (b), and (c) are block diagrams of an embodiment of the present invention. In the figure, the synchronous detector 1, the monitoring device 3, and the 4°4' low-pass filter are the same as those in FIG. Furthermore, although the threshold value setting of comparator 5 is different,
It is the same as that in Figure 2. 3' monitoring device Figure 1 (c
) shows the contents of the monitoring device in Figure 3 (b) rotated by 90 degrees. When a 4-phase PSK signal enters two monitoring devices, if the reference carrier waves are synchronized, its average output value will be the same as that of the first monitoring device 3, regardless of the magnitude of input noise.
〉Second monitoring device 3''...(1).On the other hand, in the asynchronous state of the reference carrier, the four signal points rotate around the origin, so similarly, regardless of the magnitude of input noise, First, the average output value is the first monitoring device - the second monitoring device (2).The respective average outputs are obtained from the low-pass filters 4 and 4.Synchronization of carrier waves, Since asynchrony can be identified by the magnitude of the average output of two monitoring devices, this embodiment shows a method in which the average output of the second monitoring device is divided by the average output of the first monitoring device.The divider 6 is This operation is performed.Another method is to take the difference between the two.During synchronization, the output of the divider 6 is smaller than 1 from equation (1), and when asynchronous, from equation (2), the output is less than 1.
takes the value of Therefore, by setting the threshold of comparator 5 after division G6 to a value smaller than 1, for example 0.9, comparator input≧0.9−asynchronous state comparator input<0.9− It can be identified as a synchronous state. The accuracy of this identification is improved by narrowing the 4,4' low pass filter band. It can be seen that block 7 in the figure works as a synchronous/asynchronous discriminator.

(Effects of the Invention) As described above, according to the present invention, it is possible to accurately identify whether the reference carrier is synchronized or unsynchronized in a synchronous detector of a demodulator operating under a high noise level.

Note that (C) in Figure 1 is a 90' rotation of (b), but for the general amplitude phase modulation method (b)
) and (C) must be selected so that the shaded portions do not overlap as much as possible in order to improve identification accuracy.

[Brief explanation of the drawing]

FIGS. 1(a), (b), and (c) are block diagrams of an embodiment of the present invention, FIG. 2 is a block diagram of a conventional synchronization monitoring device, and FIGS. 3(a) and (b) are monitoring devices. FIG. 2 is a diagram showing an example of a read-only memory for use in a computer. In the figure, 3 indicates a first monitoring device 3, a first monitoring device 7, and a discriminator, respectively. 71-1 Figure 1' (b) (c) 7I-2 side 71'3 Figure

Claims (1)

[Scope of Claims] A synchronous monitoring device to which a synchronous detection output of an amplitude phase modulated wave is supplied, comprising: (a) a synchronous monitoring device that outputs a detection signal when the detection output is received near a regular signal point position; (b) a second detection means that outputs a detection signal when the detection output is received at a position other than the vicinity of the regular signal point position; (c) an output of the first detection means; A synchronous monitoring device comprising: comparison means for comparing the average value with the average value of the output of the second detection means.