JPH01173918A - C/n detector - Google Patents

Abstract

PURPOSE:To always monitor a C/N(carrier-to-noise ratio) with simple constitution by measuring relation between the size of the phase difference of a PSK (phase shift keying) signal and its generating frequency, and deciding the C/N based on the relation. CONSTITUTION:A phase difference signal that is the phase difference between the phase of the PSK signal 1 and that of a VCO2 is detected at a phase comparing circuit 3, and a DC voltage equivalent to the long time means value of the phase difference signal is extracted by a loop filter 4, and the oscillation phase of the VCO2 is controlled by the DC voltage. And since the logic of a symbol is decided by the phase difference that is the output of the circuit 3, the detection of the C/N can be performed by inputting the output of the phase comparator 3 to a C/N detecting circuit 5. In such a way, it is possible to obtain a C/N detector to always detect the C/N of the PSK signal.

Description

[Detailed description of the invention] [Industrial application field] This invention is based on PSK (phase 5hift k
The present invention relates to a C/N (carrier power-to-noise power ratio) detection device in an eyeing) signal.

1. Prior Art] In PSK communication, etc., it is desirable to constantly monitor the C/N of the signal in order to guarantee the quality of the signal after transmission.

However, a C/N detection device suitable for this purpose; ξ
did not previously exist.

Conventionally, in order to measure C/N'z-, a constant device such as a spectrum analyzer was required, or a C/N detection device was realized with a complicated circuit configuration.

[Problems to be Solved by the Invention] An object of the present invention is to construct a device that can constantly monitor the C/N with a simple circuit configuration.

[Means for Solving the Problems] In the present invention, the relationship between the magnitude of the phase difference of the PSK signal and its frequency of occurrence is measured, and the C/N is determined based on this relationship.

[Effect] For a given C/H, the relationship between the magnitude of the phase difference and its occurrence probability is determined, so the magnitude of the phase difference and its occurrence corresponding to various C, /N values are It is easy to store the correspondence with probabilities as a C/N table and compare the 3(11 constant results) with this C/N table to determine the C/N.

[Examples] Examples of the present invention will be described below with reference to the drawings. 1st
The figure is a block diagram showing an embodiment of the present invention. In the figure, (1) is a PSK signal, (2) is a VCO (voltage controlled oscillator), (3) is a phase comparison circuit, (4A is a loop filter, ( 5) is a C/N detection circuit, (6) is a PSK signal input terminal, and (7) is a C/N output terminal.

FIG. 2 is a block diagram showing an example of the configuration of the C/N detection circuit (5), in which 50) is an area discriminator, (51) is a timer, and (50) is a region discriminator.
2), (53), and (54) are counters provided for each area, (55) is a comparator, and (56) is a C/
In the N table, (57) is a terminal connected to the output of the phase comparator (3), and (7) indicates the same terminal as (7) in FIG.

The VCO (2), phase comparison circuit (3), and loop filter (4) in FIG.
A phase difference signal that is a phase difference with the phase of CO (2) is detected by a phase comparison circuit (3), and a DC voltage corresponding to a long-term average value of this phase difference signal is extracted by a loop filter (4). This DC voltage constitutes a phase-locked loop that controls the oscillation phase of VCO (2). The symbol theory is determined by the phase difference that is the output of the phase comparison circuit (3).

The output of this phase comparison circuit (3) is sent to the C/N detection circuit (5).
to detect the C/N.

Figure 3 is a diagram showing the phase distribution of the two-phase PSK signal. The range indicated by A in Figure 3 is determined to be a signal that does not contain noise, and the range to which batching is applied in the figure is determined to be a signal that includes noise. For example, this range is divided into two regions, and the region where the influence of noise is small is designated as B, and the region where the influence of noise is large is designated as C. Phase comparison circuit (
3) outputs a phase difference signal for each symbol of the PsI signal <i>, and the region discriminator (50) classifies each phase difference signal into three regions A, B, and C depending on the magnitude of the phase difference. , one pulse is output for each phase difference (for each bait) from the area to which the phase difference signal belongs.
It is counted by a B counter (53) and a C counter (54), and the counted value for a predetermined time is stored, respectively. The timer (51) determines the counting time for each counter (the same time for each counter), and when counting is finished, controls such as moving the counted value of each counter to the storage area, resetting each counter, and starting the next measurement. I do.

The comparator (55) reads the data from the storage area that stores the count value of each counter, organizes it, normalizes the frequency of occurrence corresponding to each area, and stores the data in the C/N table (55).
The data should be in a format suitable for comparison with the data in 6). The count value of each counter is gradually updated as time passes, and the data sorted by the comparator 55) is accordingly updated gradually. In this series of data processing, the area discriminator (50), timer (51), and each counter (5
The operations of 2) to (54) and the comparator (55) are program-controlled by a computer (not shown).

By the way, noise has a normal distribution, so when a C/N value is given and a signal with that C/N is phase-detected, the probability of generating a signal with a certain amount of phase difference is It can be calculated from the size. Therefore, using C/N as a parameter, the probability of occurrence of signals in areas A, B, and C (-
In terms of boat fishing, the relationship between the size of the phase difference represented by the phase difference signal and its probability of occurrence is determined, and this determined relationship is called C/N.
It is stored in the table (56). C/N table (56)
is composed of, for example, a ROM (read-only memory).

After completing the data processing of the data from each counter, the comparator <55) calculates the data pattern of the processed data,
That is, the numerical values obtained by normalizing the count values of the A, B, and C counters are compared with the data pattern of the C/N table (56), and the C/N of the pattern with the highest degree of similarity is calculated as PS.
It is output from the terminal (7) as the C/N of the K signal (1).

For example, A, B.

C/N table (5
6) If the data patterns stored in the table of medium C/N = i are ai, bi, ci, then (ai
The data pattern that minimizes the value of -ax)2+(bi-bx)2+(ci-cx)2 is defined as the data pattern with the highest degree of similarity.

In the above embodiment, the magnitude of the phase difference represented by the phase difference signal is A
, B, and C. However, the number of regions may be further increased and the data patterns may be compared. However, it is necessary to have counters equal to the number of regions and to prepare C/N tables corresponding to the regions.

Furthermore, although the above embodiments have been described with respect to two-phase PSK signals, the present invention can be applied to PSK signals with any number of phases.

[Effects of the Invention] As described above, according to the present invention, by adding a simple device, the C/N of a PSK signal can be constantly detected.
This has the effect that a detection device can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing an example of the C/N detection circuit shown in FIG. 1, and FIG. 3 is a diagram showing the phase distribution of a two-phase PSK signal. . (1) is a PSK signal, (2) is a VCO1, (3) is a phase comparison circuit, (4) is a loop filter, (5) is a C/N detection circuit, (50) is a region discriminator, (52) to ( 54) is a counter, (55) is a comparator, and (56) is a C/N.
table. In addition, the same symbols in each figure indicate the same parts.

Claims (1)

[Claims] A phase comparison circuit which inputs a baseband signal of a PSK (phase shift keying) signal, compares it with the output phase of a VCO (voltage controlled oscillator) for each symbol phase of the input signal, and outputs a phase difference signal; A loop filter that inputs the output of the comparator circuit and outputs a DC voltage proportional to the long-term average value of the phase difference signal, a phase-locked loop that controls the oscillation phase of the VCO by the output of the loop filter, and the phase difference signal. A region discriminator that classifies the phase difference signal into a plurality of regions according to the magnitude of the phase difference represented by and outputs one pulse from the region to which the phase difference signal belongs for each phase difference signal; Each counter is provided for each region and counts the pulses output from the corresponding region, a timer that controls the counting time of each counter, and a C/N (
A C/N table that stores the correspondence between the magnitude of the phase difference represented by the phase difference signal and the probability of its occurrence, with the carrier wave power to noise power ratio (carrier wave power to noise power ratio) as a parameter, and the number of pulses in each region counted by each of the above counters within a predetermined time. From this, determine the relationship between the magnitude of the phase difference represented by the phase difference signal and its frequency of occurrence, compare this determined relationship with the correspondence between the magnitude of the phase difference and its probability of occurrence in the C/N table above, and find the best one. Similar C/
A C/N detection device comprising: a comparator that outputs a C/N value of the N table as a C/N value of the PSK signal.