JPH06258420A - Radio wave altimeter - Google Patents

Abstract

PURPOSE:To provide a radio wave altimeter for aircrafts, etc., in which there occurs no malfunction even when other radio altimeters exist nearby. CONSTITUTION:In a radio wave altimeter which transmits a pulse wave and receives the sending reflected wave from the earth surface in order to measure the time lag of the pulse between the transmitted wave and the received wave, it is provided with a timing pulse generating means 15 for changing the frequency of the transmitted pulse and a received pulse selecting means 16 for selecting only the pulse out of the received wave to be synthesized with the transmitted pulse. Then, the sending wave cycle is changed at every time by the means 15 and further only the pulse out of the received waves to be synthesized with the sending wave is selected by the means 16 so that the influence of disturbing waves may be eliminated, then the selected output is compared with the sending wave to found out the time difference between the both, thereby calculating the attitude based on the time difference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio altimeter mounted on an aircraft.

[0002]

2. Description of the Related Art A conventional radio altimeter will be described with reference to FIG.

The radio altimeter comprises a transmitter 1 and a receiver 2. The transmitter 1 includes a timing pulse generator 3, a transmitter 4,
The transmitting unit 5 is provided, and the receiving unit 2 is provided with a receiving antenna 6, a receiver 7, a computing unit 8 and an altitude indicator 9. In FIG. 3, 10 is the ground surface.

Next, it is assumed that the radio altimeter is mounted on the helicopter 11 as shown in FIG.
The altitude measurement in 1 will be described.

The timing pulse generator 3 generates a high frequency pulse having a constant period, for example, a high frequency pulse of 4.3 GHz, and inputs the high frequency pulse to the transmitter 4 and the arithmetic unit 8. The transmitter 4 amplifies this pulse into a high frequency pulse of, for example, 4.3 GHz. The amplified high frequency pulse is transmitted from the transmitting antenna 5 to the ground surface as a transmission wave.

The transmission wave transmitted from the helicopter 11 is
It reaches the surface 10 through the route of the solid line α in the figure, and further the surface 1
It is reflected at 0 and becomes a transmitted reflected wave. The receiving antenna 6 receives the transmitted reflected wave, the receiver 7 amplifies the transmitted reflected wave received by the receiving antenna 6, and inputs it to the calculator 8 as a received wave. The arithmetic unit 8 is, as shown in FIG.
The received wave and the reference pulse directly input from the timing pulse generator 3 are compared, the time difference ht between the pulse of the received wave and the reference pulse is obtained, and the distance is calculated from the time difference ht, and the receiver 2 indicate.

Incidentally, the transmitting antenna 5 and the receiving antenna 6
Has a wide directivity of ± 45 ° so that it can operate with respect to the pitch and roll of the aircraft.

[0008]

The above-described conventional radio altimeter does not cause any problem if there is no aircraft nearby, but as shown in FIG. 4, another helicopter 1 is installed near the helicopter 11.
When 2 is flying, there is a possibility of malfunction as described below.

The other helicopter 12 is also the helicopter 11 described above.
Similar to, high frequency pulse is emitted for altitude measurement. Further, as described above, since the directivity of the transmitting antenna 5 and the receiving antenna 6 is wide, the high frequency pulse generated by the other helicopter 12 is reflected on the ground surface 10 via the route β and further received by the helicopter 11.

The relationship between the pulses at this time and the operation for measuring the time difference will be described with reference to FIG.

The transmitted wave from the helicopter 11 has a constant time h
After t, the transmitted reflected wave is received and the pulse from the helicopter 12 is received as an interfering wave. As a result, the received wave is the sum of the transmitted reflected wave and the interfering wave. At this time, the calculator 8 cannot distinguish between the transmitted reflected wave and the interfering wave. Therefore, the time differences h1, h2, h3, h4 are measured, and the time differences h1, h2
Different altitudes are calculated and displayed based on 2, h3 and h4.

As described above, the conventional radio altimeter has a drawback that it malfunctions when another radio altimeter is nearby.

In view of the above situation, the present invention is to provide a radio altimeter capable of always performing accurate altimeter measurement even if another radio altimeter is nearby.

[0014]

The present invention is a radio altimeter that emits a pulse wave, receives a transmitted reflected wave from the surface of the earth, and measures the time difference between the pulse of the transmitted wave and the pulse of the received wave. Is provided with a timing pulse generating means for changing the frequency and a reception pulse selecting means for selecting a pulse synchronized with the transmission pulse from the received wave.

[0015]

The transmission pulse cycle is changed each time by the timing pulse generating means, and only the pulse synchronized with the transmission wave among the reception waves is selected by the reception pulse selecting means, and the selected output is compared with the transmission wave. The time difference between the two is obtained, and the altitude is calculated from this time difference. Therefore, even if the received wave contains an interfering wave, the obtained result has no effect of the interfering wave.
Be accurate.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, the same parts as those shown in FIG. 3 are designated by the same reference numerals.

The transmission unit 13 includes a timing pulse generator 1
5, a transmitter 4, and a transmission antenna 5, and the reception unit 14 includes a reception antenna 6, a receiver 7, a reception pulse selection circuit 16,
It is composed of a computing unit 8 and an altitude display 9.

The timing pulse generator 15 emits a transmission wave at a different cycle every time, and the transmission wave is input to the transmitter 4 and the arithmetic unit 8 and the reception pulse selection circuit 16. The transmission wave input to the transmitter 4 is amplified and emitted to the ground surface 10 from the transmission antenna 5. The transmitted reflected wave reflected by the surface of the earth 10 is received by the receiving antenna 6, amplified by the receiver 7, and input to the received pulse selecting circuit 16 as a received wave. The received pulse selection circuit 16 compares the reference pulse input from the timing pulse generator 15 with the received wave, selects a pulse that is synchronized with the reference pulse from among the pulses of the received wave, and selects the arithmetic unit 8 To enter.

The calculator 8 compares the received wave with the reference pulse directly input from the timing pulse generator 15 to obtain the time difference ht between the received wave pulse and the reference pulse,
Further, the altitude is calculated from the time difference ht and displayed on the receiving unit 14.

Next, the operation when another helicopter 12 is flying nearby as shown in FIG. 4 will be described with reference to FIG.

The receiving antenna 6 simultaneously receives an interfering wave in addition to the transmitted reflected wave, and the received wave is a combination of the transmitted reflected wave and the interfering wave. As described above, the received pulse selection circuit 16 selects and outputs only the received wave that is synchronized with the reference wave. Then, the arithmetic unit 8 compares the selected output with the reference pulse and calculates the time difference ht.
Then, the altitude is calculated from the time difference ht.

Therefore, in the present embodiment, it is possible to distinguish the transmitted reflected wave of the own device and the interfering wave from the other device and always measure the correct altitude.

[0024]

As described above, according to the present invention, it is possible to eliminate the influence from other radio altimeters in the vicinity, and it is possible to always perform accurate altitude measurement without malfunction. .

[Brief description of drawings]

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

FIG. 2 is a timing diagram showing an operation in the embodiment.

FIG. 3 is a block diagram showing a conventional example.

FIG. 4 is an explanatory diagram of altitude measurement by a radio altimeter.

FIG. 5 is a timing diagram showing the operation of the conventional example when there is no interfering wave.

FIG. 6 is a timing diagram showing the operation of the conventional example when there is an interfering wave.

[Explanation of symbols]

 4 transmitter 5 transmitting antenna 6 receiving antenna 7 receiver 8 computing unit 9 altitude display 10 ground surface 13 transmitting unit 14 receiving unit 15 timing pulse generator 16 receiving pulse selection circuit

Claims (1)

[Claims] 1. A radio altimeter that emits a pulse wave, receives a transmitted reflected wave from the surface of the earth, and measures the time difference between the pulse of the transmitted wave and the pulse of the received wave. Timing pulse generation for changing the frequency of the transmitted pulse. A radio altimeter comprising: means and a reception pulse selection means for selecting a pulse that is synchronized with a transmission pulse from a reception wave.