JPH02124478A - Circuit for detecting fault of rf switch - Google Patents

Abstract

PURPOSE:To make it possible to detect a fault even when a diode is opened by detecting currents flowing through an antenna system to be used and through other required antenna system in synchronization with timing when switch is conducted. CONSTITUTION:A signal from a circuit DET 1 which detects a current flowing through an antenna A in a first system and a switching signal ISLS 1 are inputted into an AND gate 11. A signal associated with an antenna B in a second system is inputted in an AND gate 12 by the same way. The outputs of the gates 11 and 12 are inputted into an OR gate 13. When a switch remains intact on the side of the antenna A due to the short circuit of a diode, transmitting pulses which should be transmitted from the antenna B are transmitted from the antenna A. Therefore, the output of the gate 12 is always L, and the signal ISLS 1 and the signal DET 1 are H. Thus the output of the gate becomes H. Namely, since the output of the gate 13 becomes H when the switch is faulty, the fault can be detected by detecting the output of the gate 13.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a failure detection circuit for a switch that switches between a plurality of antenna systems.

(Prior Art) As an antenna system in which a plurality of antenna systems are switched and used by switching, there is, for example, an antenna system for an interrogator of an ally identification device (IFF) mounted on an aircraft.

The interrogation pulse group emitted by the interrogator is a series of three pulses emitted at predetermined time intervals as shown in FIG. If an aircraft that receives this pulse group responds, the inquiring aircraft will be overloaded with information, making judgments extremely complicated, and may even lead to erroneous judgments. For this reason, the interrogator has two antenna systems with different beam directions, and by switching a switch, the first and third pulses of the interrogation pulse group are directed to the first beam direction (Σ pattern), and the second pulse is directed to the first beam direction (Σ pattern). A second beam direction (Δ pattern) having a pattern on both sides of the first beam direction except for the first beam direction is emitted, and the receiving machine is configured such that the incoming electric field strength of the first and third pulses is smaller than that of the second pulse, e.g. Only when the intensity is 9 dB or more, a response will be made, assuming that the aircraft is located in front of the interrogating aircraft, that is, it is a threat aircraft.

However, if the switch that switches between the two antenna systems mentioned above fails, the direction of the emitted radio waves will be only the first beam direction or the second beam direction.
There is no difference in the incoming electric field strength between the third pulse and the second pulse, and the receiver does not recognize it as a threat aircraft, so the receiver side does not respond and the system does not function properly, which is extremely dangerous.

For this reason, it is necessary to monitor the state of the antenna changeover switch, and conventionally the following circuit has been used.

FIG. 8 shows a conventional two-system antenna switching circuit using diodes and a circuit for detecting a failure of the circuit.

In the figure, l is the antenna of the first system, and capacitor 2.
3 and λ/4 transmission line 4 to a transmitter (not shown). Diode 5 is connected between capacitors 2 and 3.
, a coil 6 and a diode 7 are connected in parallel, and the coil 6 is provided with two systems of 0 or more to which a current detection section 8 is connected.

The operation in the figure is as follows. That is, when a bias current is applied to the coil 6, a current flows to the diode 5.7, which makes the diode conductive.As a result, the impedance of the circuit as seen from the transmitter becomes ■, and the antenna of the first system as seen from the transmitter. No high frequency signal flows into the antenna switch, and as a result, the antenna switch is turned off.

At this time, if we decide not to apply a bias current to the coil 9 of the second system, the impedance seen from the transmitter side becomes 0, contrary to the first system, and a high-frequency current flows to the antenna of the second system, and the antenna switch becomes ON. By changing both bias currents, the two antenna systems are switched.

Therefore, the bias current of the circuit, that is, the current flowing through the coil 6.9, is detected by the current detection section, and an abnormality in the switching circuit is detected based on the presence or absence of the current.

However, the conventional failure detection circuit described above cannot detect an abnormality in the following cases. In other words, if a diode is short-circuited, the current continues to flow, and it is known that there is an abnormality, but if one of the diodes is open. Even if
If the other diodes are normal, current will flow, making it impossible to detect a failure.

(Object of the Invention) The present invention was made in order to eliminate the drawbacks of the conventional RF switch failure detection circuit as described above, and it is an object of the present invention to provide a circuit that can detect a failure even when a diode opens. purpose.

(Summary of the Invention) In order to achieve the above object, the present invention is configured as follows. That is, in an antenna system that uses a plurality of antenna systems by switching them with a changeover switch, the current flowing through the antenna system to be used and other required antenna systems is detected in synchronization with the timing at which the switch conducts, and the current flows into the current. An abnormality in the changeover switch is detected based on the

(Example) The present invention will be described in detail below based on the illustrated example.

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

In the same figure, 11 is an AND gate, one of which receives a signal from a circuit DETI that detects the current flowing to the first system antenna (not shown), and the other input receives a switching signal ISLS 1. input. 12 is A
It is an ND gate, and like AND gate 11, DET2
Input the signal from A and the switching signal l5LS2, and then
The outputs of the ND gates 11 and 12 are input to the OR gate 13.

Further, FIGS. 2 to 4 are time charts showing waveforms of various parts of the circuit of FIG. 1.

First, the operation when the changeover switch is normal will be explained using FIG. 2.

The operation of the RF switch switching circuit is the same as that of the conventional circuit described above, and only when the switching signal is H, the antenna system is switched from 0FFL to another system.

First, when the first pulse P1 is sent out from the transmitter, DE
TI detects this and sends a signal to AND gate 11.

A switching signal l5LSI is also input to the AND gate 11 at the same time. Here, since the switching signal l5LSI is L, the output of the AND gate 11 is L. At this time DET
Since no signal is sent from gate 2, the output of AND gate 2 becomes L, and as a result, the output of OR gate 13 becomes L.

When pulse P2 is then sent out, DET2 detects it and sends a signal to AND gate 12. AND gate 12
At the same time, a switching signal l5LS2 is also input to the terminal. Here, since the switching signal l5LS2 is active, the output of the AND gate 12 becomes L. At this time, since no signal is sent from DET1, the output of AND gate 11 becomes L, and as a result, the output of OR gate 13 becomes L.

Finally, when P3 is sent out, the same operation as when P1 is sent out is performed, and since the l5LSI is YES, the output of the OR gate 13 is similarly low.

As described above, as long as the RF switch switching circuit operates normally, the output from the OR gate 13 is maintained.

Next, the operation in the case where the changeover switch fails due to a diode short circuit or the like and remains on the first system antenna side will be described with reference to FIG.

In this case, pulses PI, P2, and P3 will all be sent out from the antenna of the first system, and will not be sent out from the antenna of the second system. Since no signal is detected from DE T 2, the AND gate 12 output is always L
It is. However, when P2 is sent out, AND gate 11
Since the switching signals ISl and Sl are at H, and the DETI signal is also at H, the output of the AND gate 11 becomes I-■ while P2 is sent out, and as a result, the output of the OR gate 13 becomes H during that time. become.

On the other hand, when the antenna remains on the side of the second system antenna, the dynamic f is as shown in FIG.

In the same figure, contrary to what was described in mf, the output of the AND gate 11 becomes H when Pl and P3 are sent out, and the output of the OR gate 13 becomes H.
The output becomes H.

In this way, as long as the changeover switch is normal, the output of the OR gate 13 is on, and if it fails, it becomes H, so by detecting the output of the OR gate 1~, the output of the OR gate 13 is maintained.
A failure of the F changeover switch can be detected.

The case where there are two systems has been described above, but when there are three or more systems, the number of AND gates may be increased according to the number of systems, as shown in FIG. 5, and all the outputs of each AND gate may be input to the OR gate.

In addition, in this example, a method of detecting an abnormality when a current flows in a system that should not be used was shown, but conversely, a case where no current flows in a system that should be used is detected as an abnormality. It may be detected as In this case, the switching signal input to the AND gate is inverted and input. By doing so, the output of the OR gate becomes 11 every time a transmission pulse is sent out if there is no abnormality, and remains at L if there is an abnormality.

Furthermore, by inputting the output of the OR gate 13 of the present invention to the CLR of the frisible flop 14 as shown in FIG. Since the information can be held until the information is input, the detection process becomes easier.

(Effects of the Invention) Since the present invention is configured and operates as described above, it is possible to detect failures of the RF changeover switch, including when the diode is open, and this is effective in maintaining the safety of the aircraft. It has a significant effect.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Figs. 2 to 4 are time charts showing waveforms of each part of the circuit in Fig. 1, and Fig. 5 is an example of a circuit when there are three or more systems. , Figure 6 is an example of a circuit that uses a flip frontor to facilitate abnormality detection, Figure 7 is a group of interrogation pulses emitted by an interrogator, and Figure 8 is a switch circuit that switches between two antenna systems without using conventional diodes. and a circuit for detecting a failure of the circuit. 11.12...AND gate 13...
...○R game) ~

Claims (1)

[Claims] In an antenna system that uses a plurality of antenna systems by switching them with a changeover switch, the current flowing through the antenna system to be used and other required antenna systems is detected in synchronization with the timing at which the switch conducts, and the current flowing through the antenna system to be used and other required antenna systems is detected based on the current. A circuit that detects abnormalities in the changeover switch.