JP2518136B2 - BIT circuit of on-board TACAN / DME device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to on-board TACAN (ta
critical air navigation sys
tem) / DME (distance measure)
BIT (build) of the ng equipment device
in test) circuit, and more particularly to gate control of a receiver during BIT.

[0002]

2. Description of the Related Art B of a conventional on-board TACAN / DME device
As shown in FIG. 2, the IT circuit includes an RF switch 2 for switching between an external RF signal received by the antenna 1 and a noise signal for BIT check, a noise generator 9 for generating a noise signal for BIT check, and a BIT check. It has a BIT control circuit 10 for controlling. Filter 3, mixer 4, IF video amplifier 5, decoder 6, AG of FIG.
The C7 and local signal generator 8 form a receiver.

When the BIT check is started, the RF switch 2 is switched by the start signal from the BIT control circuit, and the noise signal from the noise generator 9 is input to the receiver through the filter 3. The noise signal is converted into noise video by the IF video amplifier 5 through the mixer 4 and input to the decoder 6. The decoder 6 decodes noise of the pulse interval of 12 μs (in X mode) which is the pulse interval of TACAN or DME in the input noise video, and the decoded pulses are equal to or more than the specified number at the BIT check determination timing. If there is, it is determined to be normal.

[0004]

In the conventional BIT circuit, the noise signal during BIT check and the normal operation (BI
RF for switching external RF signals (when not T check)
Since the switch isolation is only about 30 dB, the external RF signal is mixed into the receiver during the BIT check, and if the input level of this RF signal is high, the BIT check is performed by the external RF signal instead of the noise signal. Become.

At this time, when the level of the external RF signal suddenly changes due to a change in the position of the antenna (movement of an aircraft equipped with the TACAN / DME device), A of the receiver
There is a problem that the gain control of the GC cannot follow up completely and the noise video signal disappears momentarily. If this timing and the timing of the BIT check match, the decoded pulse cannot be detected and it is judged as abnormal. .

An object of the present invention is to provide a BIT circuit of an on-board TACAN / DME device which can perform BIT check without being affected by disturbance regardless of a change in the level of an external RF signal.

[0007]

The BIT circuit of the present invention comprises:
The BIT control circuit that controls the BIT check of the on-board TACAN / DME device, the gain control signal generator that inputs the start signal from the BIT control circuit and outputs the fixed gain control signal, and the AGC signal from the AGC. A switch for switching the fixed gain control signal and inputting it to the IF video amplifier.

[0008]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the BIT circuit of the present invention. The BIT circuit includes an RF switch 2 for switching an external RF signal received by the antenna 1 and a noise signal at the time of BIT check, a noise generator 9 for generating a noise signal at the time of BIT, and a BIT control circuit 10 for controlling the BIT check. And BI at the time of BIT check
According to the start signal from the T control circuit 10, the I
The fixed gain control signal generator 11 that outputs a fixed gain control signal for setting the gain of the F video amplifier 5 to a constant value, and the fixed gain control signal and the AGC signal from the AGC 7 are switched to perform fixed gain control. And a selector switch 12 for inputting a signal to the IF video amplifier 5.

When the BIT check is started, the RF switch 2 is switched by the start signal from the BIT control circuit 10, and the noise signal from the noise generator 9 is filtered by the filter 3.
Is input to the receiver through. At the same time, the fixed gain control signal generator 11 generates a gain control signal for making the gain of the IF video amplifier 5 constant by the start signal, and the changeover switch 12 switches between the AGC signal and the fixed gain control signal. It is input to the amplifier 5. The noise signal is input to the IF video amplifier 5 through the mixer 4. IF video amplifier 5
Is controlled so that the gain is fixed at a predetermined value, so it outputs a noise video with a constant level,
It is input to the decoder 6. In the decoder 6, as in the conventional case, TACAN or DM of the input noise video is input.
Noise having a pulse interval of 12 μs (in the X mode), which is the pulse interval of E, is decoded, and if the number of decoded pulses is equal to or more than a specified number at the BIT check determination timing, it is determined to be normal.

[0011]

As described above, according to the present invention, the gain of the IF video amplifier is fixed to a constant value during the BIT check, so that the influence of the disturbance can be prevented regardless of the change in the level of the external RF signal. The effect is that you can check the BIT without receiving it.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a conventional BIT circuit.

[Explanation of symbols]

 1 Antenna 2 RF Switch 3 Filter 4 Mixer 5 IF Video Amplifier 6 Decoder 7 AGC 8 Local Signal Generator 9 Noise Generator 10 BIT Control Circuit 11 Fixed Gain Control Signal Generator 12 Changeover Switch

Claims (2)

(57) [Claims] 1. A BIT control circuit for controlling a BIT check of an on-board TACAN / DME device, a gain control signal generator for inputting a start signal from the BIT control circuit and outputting a fixed gain control signal, and an AGC. An on-board TACAN / DME, comprising a switch for switching between the AGC signal from the input terminal and the fixed gain control signal and inputting it to an IF video amplifier.
BIT circuit of the device. 2. A fixed gate control signal generator for outputting a fixed gate control signal for setting a gain of an IF video amplifier of a receiver to a constant value according to a start signal from a BIT control circuit during BIT check, and the fixed gate control signal generator. The BIT circuit of the on-board TACAN / DME device, comprising: a changeover switch for switching between the gate control signal and the AGC signal of (1) and inputting a fixed gate control signal to the IF video amplifier.