JP2946610B2 - Device failure detection method for intermediate frequency band equalizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] Amplitude equalization and reception output level which are inserted into an intermediate frequency signal circuit before a demodulator of a microwave radio receiving apparatus and correct a change in amplitude frequency characteristics due to fading. With regard to the detection method of the equipment failure of the equalizer that performs the AGC control that keeps the constant, the failure of the equalizer of the intermediate frequency itself is distinguished from the abnormality due to the fading of the radio path, and the purpose is to provide a detection method capable of detecting the failure. Immediately before the equalizer, a notch circuit for artificially attenuating the amplitude of the output signal and changing the frequency characteristic, a switch for turning on / off the notch circuit for an intermediate frequency signal circuit, and a switch for connecting the notch circuit comprises a comparator for comparing the output iF ₂ of the equalizer when not inserted into the output iF ₁ and the circuit of the equalizer when inserted into the circuit of the intermediate frequency signal, the output of the comparator is the switch No change with on / off If substantially the same, the equalizer is normal, the equalizer if there is a change is configured to determine that the malfunction.

[Industrial applications]

The present invention relates to a digital microwave radio apparatus, and more particularly to a system for detecting a failure of an equalizer provided in an intermediate frequency circuit of a receiving apparatus before demodulation.

In a digital microwave radio apparatus, when the capacity of a transmission signal increases, transmission distortion of a reception signal increases. For this reason, an equalizer for equalizing transmission distortion of a received signal has become important.

[Conventional technology]

A conventional equalizer for equalizing transmission distortion of a received signal is a third equalizer.
As shown in the figure, the signal is inserted into the circuit of the intermediate frequency signal IF at the preceding stage of the demodulation board 20 of the receiving device, and the amplitude equalization for correcting the change in the frequency characteristic of the amplitude due to fading and the AGC control for keeping the level of the reception output constant Had gone.

[Annotations to be solved by the invention]

However, an abnormality in the output of the equalizer 10 (hereinafter abbreviated as an IF band equalizer) of the intermediate frequency inserted into the circuit of the intermediate frequency IF may be caused by the failure of the equalizer 10 itself or by the equalizer 10. There has been a problem that it is difficult to find out whether the cause is fading of the previous radio path.

SUMMARY OF THE INVENTION An object of the present invention is to provide a detection method capable of detecting only a failure of an intermediate frequency equalizer itself, distinguishing from an abnormality due to fading of a radio path.

[Means for solving the problem]

As shown in FIG. 1, a notch circuit 1 that attenuates the amplitude of an output signal and creates fading that changes the frequency characteristic of the amplitude, just before the equalizer 10 in the IF band, as shown in FIG.
A switch 2 for turning on / off the notch circuit to / from an intermediate frequency IF circuit, an output IF ₁ of the equalizer 10 when the notch circuit 1 is inserted into the intermediate frequency IF circuit by the switch 2, and insertion into the circuit Comparator 3 for comparing with the output IF ₂ of the equalizer 10 when not performed
If the output of the comparator 3 is substantially the same without any change when the switch 2 is turned on / off, the equalizer 10 is determined to be normal, and if there is a change, the equalizer 10 is determined to be faulty. It is solved by the present invention.

In the principle diagram of FIG. 1 showing the basic configuration of a device failure detection system for an equalizer in an intermediate frequency band according to the present invention, reference numeral 1 denotes a pseudorandom detector provided immediately before an equalizer 10 in an intermediate frequency band of a receiving apparatus. A notch circuit which attenuates the amplitude of the output signal from a specified value and changes the frequency characteristic of the amplitude to create fading.

Reference numeral 2 denotes a switch for turning on / off the notch circuit to / from the intermediate frequency IF circuit.

Reference numeral 3 denotes an output IF ₁ of the IF band equalizer 10 when the notch circuit 1 is inserted into the intermediate frequency IF circuit by the switch 2 and an output IF ₂ of the IF band equalizer 10 when the notch circuit 1 is not inserted into the circuit. This is a comparator for comparison.

[Action]

In the present invention, the equalizer 10 is normal if the output of the comparator 3 is substantially the same without any change when the switch 2 is turned on and off, and if there is a change, the IF band equalizer 10 is faulty. Judge. Therefore, the problem can be solved because the failure of the equalizer itself in the intermediate frequency band can be detected in distinction from the abnormality due to the fading of the radio path.

〔Example〕

The principle diagram of FIG. 1 shows the configuration of a system for detecting a device failure of an equalizer in the intermediate frequency band according to an embodiment of the present invention, and has already been described in detail. Figure 2 is a characteristic diagram for explaining the operation of the embodiment of the present invention, (1) in the figure is a case of a failure of the amplitude equalizer 10 _first IF equalizer 10, of FIG. (2) is a case of failure of the AGC amplifier 10 _{and second} IF equalizer.

Notch circuit 1 of the embodiment of the present invention, the amplitude equalizer 1 ₁ changing the amplitude of the frequency characteristic of the output signal, simple to be made using the attenuator 1 ₂ for attenuating the amplitude over the entire frequency band The circuit is placed immediately before the IF equalizer 10. The on / off of the notch circuit 1 to / from the intermediate frequency circuit can be easily performed by a switch 2 having a switching contact or by mounting by soldering or the like. By the insertion of the notch circuit 1, forms the amplitude frequency characteristic 11 of the output of the IF equalizer 10, as in FIG. 2 (1), the amplitude frequency characteristic of the amplitude equalizer 1 ₁ notch circuit 1 remained if 11 _1, determines that the amplitude equalization unit 10 ₁ of the iF equalizer 10 is faulty, as the FIG. 2 (2), the amplitude characteristic of the attenuator 1 ₂ notch circuit 1 if the form 11 ₂ attenuated at all frequencies, it is determined that the AGC amplifier 10 _{and second} iF equalizer 10 is faulty.

Therefore, the embodiment of the present invention shown in FIG. 2 has no problem because the failure of the equalizer itself in the intermediate frequency band is detected separately from the abnormality due to the fading of the radio path.

In actual use, although not shown, after switching the working line of the main line to the protection line, the IF of the working line is switched.
It is sufficient to confirm whether or not the equalizer has a device failure.

〔The invention's effect〕

As described above, the notch circuit of the present invention is periodically
By inserting the IF equalizer immediately before the equalizer and confirming whether there is a failure in the IF equalizer itself, there is an effect that the transmission quality of the line can be easily kept good.

[Brief description of the drawings]

FIG. 1 is a principle diagram showing a basic configuration of a device failure detection system for an equalizer in an intermediate frequency band according to the present invention, FIG. 2 is a characteristic diagram for explaining the operation of an embodiment of the present invention, and FIG. It is a block diagram of the equalizer of the conventional intermediate frequency band. In the figure, 1 is a notch circuit, 2 is a switch, 3 is a comparator, 10 is an equalizer, and 20 is a demodulator.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-55-140167 (JP, A) JP-A-55-117401 (JP, A) JP-A-48-77750 (JP, A) 90952 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04B 7/005 H04B 3/04-3/18 H03H 15/00-21/00 H04B 17/00-17/02

Claims (1)

(57) [Claims] 1. An equalizer which is inserted into a circuit of an intermediate frequency signal before demodulation of a radio receiving apparatus and which performs amplitude equalization for correcting a change in frequency characteristics of amplitude due to fading and AGC control for making a level of a reception output constant. In a method for detecting a device failure of a device (10), a notch circuit (1) for attenuating the amplitude of an output signal and changing a frequency characteristic in a pseudo manner immediately before the equalizer; Switch for turning on / off the circuit (2)
And comparing the output of the equalizer (IF ₁ ) when the notch circuit is inserted into the circuit of the intermediate frequency signal with the switch and the output (IF ₂ ) of the equalizer when the notch circuit is not inserted into the circuit. Tableware (3)
If the output of the comparator is substantially the same without any change when the switch is turned on / off, the equalizer is determined to be normal, and if there is a change, the equalizer is determined to be faulty. An equipment failure detection method for an equalizer in the intermediate frequency band.