JPH0343819B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an autonomous testing method for a multi-frequency signal receiver that detects the presence or absence of a signal using a discrete Fourier transform (hereinafter referred to as DFT).

Traditionally, DFT circuits are tested by inputting a sine wave.
This is done by comparing the output of the DFT with an arbitrary threshold, but it is possible that the phase of the DFT nucleus and the phase of the input sine wave are asynchronous, or even if they are synchronized, the phase of both is π/2 radian. If it was an integer multiple of , even if there was a fault in either the circuit for calculating the real part of the DFT circuit or the circuit for calculating the imaginary part, the failure could not be detected.

The purpose of the present invention is to solve such problems and to
An object of the present invention is to provide an autonomous testing method for a multi-frequency signal receiver, which allows simultaneous testing of both a circuit for determining the real part of the circuit and a circuit for determining the imaginary part of the circuit.

The autonomous test method of the multi-frequency signal receiver of the present invention is as follows:
In a multi-frequency signal receiver that detects the presence or absence of a signal by DFT, a sine wave whose phase differs from the DFT core sine wave and cosine wave by a value that is not an integral multiple of π/2 radians is input to the DFT circuit, A value smaller than the absolute value of the DFT of the input sine wave and larger than the real and imaginary parts of the DFT of the input sine wave is set as a threshold, and the output of the DFT circuit when the sine wave is input is compared with the threshold. Features.

In addition, the autonomous test method for a multifrequency signal receiver of the present invention is such that in a multifrequency signal receiver that detects the presence or absence of a signal by the square of the DFT, π/2 radian is applied to the core sine wave and cosine wave of the DFT. A sine wave whose phase differs by a value that is not an integer multiple of is input to a circuit that obtains the square of the DFT, and the value is smaller than the square of the DFT of the input sine wave and larger than the square of the real part and the square of the imaginary part of the input sine wave. is a threshold value, and the output of a circuit that obtains the square of the DFT when the sine wave is input is compared with the threshold value.

In either method, DFT output (or
DFT squared) is smaller than the threshold, it is known that the receiver is at fault.

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a multi-frequency signal receiver to which the present invention is applied. This receiver is based on DFT, and an input signal from an input terminal 1 is input to a circuit 2 for calculating the real part of DFT and a circuit 3 for calculating the imaginary part of DFT. The DFT real part output 4 and the DFT imaginary part output 5 from the DFT real part determining circuit 2 are input to the absolute value determining circuit 6, and the DFT absolute value output 7 is output. The absolute value output 7 and the threshold value 8 are compared in a comparator circuit 9, and the comparison result is outputted to an output terminal 10.

Circuits 2 and 3 each consist of a multiplier, an adder, and a shift register (or memory), and circuit 2 is given the core sine wave of the DFT, and circuit 3 is
The core cosine wave of the DFT is given. Further, the circuit 6 includes two multipliers for squaring the real part output 4 and the imaginary part output 5, an adder for adding these squared results, and a square root value whose input data is stored in advance as an address. It is equipped with a ROM that outputs.

In FIG. 1, the circuit configuration itself is well known, but depending on the waveform input from input terminal 1, even if there is a fault in circuits 2 and 3, it may be impossible to detect it. be.

Therefore, in the system of the present application, failures in the receiver can be detected correctly by specifying the conditions of the waveform input to the signal receiver during an autonomous test of the signal receiver.

Next, the test method of the present invention will be explained with reference to FIGS. 1 and 2.

Figure 2 shows the values of the real part 4, imaginary part 5, and absolute value 7 of the DFT when a sine wave whose phase differs by θ from the core sine wave of the DFT is input to input terminal 1 in Figure 1. It is a diagram in which the vertical axis represents the phase θ and the horizontal axis represents the phase θ.

First, if the circuit 2 for calculating the real part of DFT and the circuit 3 for calculating the imaginary part are operating normally, the output of the circuit 6 for calculating the absolute value will be 7 in Fig. 2,
It is constant regardless of the phase θ. However, there is a failure in circuit 2 that calculates the real part of DFT, and its output 4
When becomes zero, the output of the circuit 6 that calculates the absolute value is
It becomes the same as the imaginary part output 5 of the DFT, and if there is a failure in the circuit 3 for calculating the imaginary part of the DFT and its output becomes zero, the output of the circuit 6 for calculating the absolute value will be the same as the real part 4. Therefore, the relationship between the threshold value 8 and the phase θ is expressed as
If it is selected within the shaded area 11 in the figure, the output 7 of the circuit 6 for calculating the absolute value will be equal to or higher than the threshold value 8 under normal conditions, and the circuit 2 for calculating the real part of DFT and the circuit 3 for calculating the imaginary part will be selected. In the event of a failure, the failure can be detected when the threshold value is equal to or less than 8.

As described above, an example of a means for creating a sine wave whose phase differs from the waveform input during the autonomous test of the present method, that is, the sine wave and cosine wave of the DFT core by a value that is not an integral multiple of π/2 radians. explain.

For example, a waveform generation circuit 11 as shown in FIG.
The waveform created by is input to the receiver. The circuit 11 includes three N-ary counters 12 to 14, a selector 15 that selects and outputs the outputs of these counters in a time-division manner, and a sine wave ROM 16 that uses the output of the selector 15 as an address input and outputs the stored contents.
, three latch circuits 18-20 that latch and output the output of the ROM 16, and a timing controller 17 that controls the operation timing of the selector 15 and the latch circuits 18-20. The contents of the sine wave ROM 16 are as shown in FIG.
~N-1, amplitude values -1 to 1 are encoded and stored. In this configuration, the counter 12,
The initial values of 13 and 14 are respectively A (corresponding to 0 radian), B (corresponding to π/4 radian), and C (π/4 radian) in Figure 4.
2 radians), and when the output of the counter 12 is selected by the selector 15, the output of the sine wave ROM 16 is latched only by the latch circuit 18, and the sine wave A of the core of the DFT in FIG. The timing controller 17 controls the selector 15 and latch circuit 18 to input the signal to the receiver.
~20 controls. timing controller 17
Under the control of
One of the zeros latches the output of ROM16. That is, the output read from the ROM 16 by the counter B is latched by the latch circuit 19 and inputted to the input terminal 1 of FIG. 1 as the test input wave B for detecting a fault during the autonomous test according to the present invention. Further, the output read from the ROM 16 by the counter C is latched by the latch circuit 20 and inputted to the signal receiver as the core cosine wave C of the DFT in FIG. In addition, in the explanation of FIG. 4, the test input sine wave B has a phase difference of π/4 radians from the sine wave A, but this phase shift is not limited to this value, and must be an integral multiple of π/2. If so, the effects of the present invention can be achieved.

In the above embodiment, a multi-frequency signal receiver that detects the presence or absence of a signal by comparing the real and imaginary part outputs of DFT with a threshold value has been described. Similar results can be obtained by using the circuit for calculating the imaginary part as a circuit for calculating the square of the imaginary part, and the circuit 6 for calculating the absolute value as an adding circuit.

As explained above, the present invention uses an input sine wave and
By setting the relationship between the phase of the DFT nucleus and the threshold, even if there is a fault in either the circuit that calculates the real part or the circuit that calculates the imaginary part of the DFT, it can be detected with the same amount of hardware as in the conventional test method. It is effective in detecting

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention;
Figure 2 is a diagram showing the relationship between the outputs of each part in Figure 1, Figure 3 is an example of a circuit that creates the waveform input to the receiver in Figure 1, and Figure 4 is the diagram shown in Figure 3. It is a figure explaining operation. 1: Input terminal, 2: Circuit for calculating the real part of the discrete Fourier transform, 3: Circuit for calculating the imaginary part of the discrete Fourier transform, 4: Output of circuit 2, 5: Output of circuit 3, 6: Absolute value Circuit for obtaining absolute value, 7: Output of circuit for obtaining absolute value, 8: Threshold value, 9: Comparison circuit, 10:
Output terminal.

Claims (1)

[Claims] 1. In a multi-frequency signal receiver that detects the presence or absence of a signal by discrete Fourier transform, π/2
Sine waves whose phases differ by a value that is not an integer multiple of radians are input to a discrete Fourier transform circuit, and the real and imaginary parts of the discrete Fourier transform of the input sine wave are smaller than the absolute value of the discrete Fourier transform of the input sine wave. A value larger than the threshold is set as a threshold, and an output of the discrete Fourier transform circuit when the sine wave is input is compared with the threshold, and if the output is smaller than the threshold, the receiver is determined to be at fault. An autonomous test method for multi-frequency signal receivers. 2. In a multi-frequency signal receiver that detects the presence or absence of a signal by the square of the discrete Fourier transform, for the core sine wave and cosine wave of the discrete Fourier transform,
A sine wave whose phase differs by a value that is not an integer multiple of π/2 radians is input to a circuit that obtains the square of the discrete Fourier transform, and is smaller than the square of the discrete Fourier transform of the input sine wave, and whose phase differs by a value that is not an integer multiple of π/2 radians. A value larger than the square of the real part and the square of the imaginary part of the Fourier transform is set as a threshold, and the output of a circuit that obtains the square of the discrete Fourier transform when the sine wave is input is compared with the threshold, and the output is determined to be the threshold. An autonomous test method for a multi-frequency signal receiver, characterized in that a failure of the receiver is determined when the signal is smaller than that of the receiver.