JP2638474B2 - Automatic antenna switching device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic antenna switching device, and more particularly to an automatic antenna switching device for automatically switching two antennas connected to an on-board radio navigation device.

[0002]

2. Description of the Related Art Conventionally, various radio navigation systems have been known which enable automatic piloting of an aircraft by measuring a current position of the aircraft, a distance from a ground station, and the like. There have been proposed various navigation devices mounted on an aircraft which are applied to (for example, JP-A-4-240516, JP-A-4-24576 and others). Among them, the above-mentioned radio navigation system is characterized in that there are few malfunctions due to interference or the like, and that the measurement function of distance and azimuth is combined into one system, TACAN (Tactical air).
Navigation is currently widely used in various countries.

[0003] The Takan is composed of an onboard device mounted on an aircraft (hereinafter referred to as an onboard Takan device) and a ground station (hereinafter referred to as a ground Takan device). In the next radar system, distance measurement is performed by measuring the time required for a pulse to reciprocate between two points, a ground-based takan device and an on-board takan device. This is performed by measuring the phase between the modulation component and the azimuth reference signal.

[0004] When mounted on a large or highly maneuverable aircraft, the onboard Takan device is generally connected to transmitting and receiving antennas arranged at two places on the body, and these two antennas are often connected. Sometimes I switch manually,
In the case of automatic switching, an automatic antenna switching device having a configuration shown in FIG. 4 is conventionally used.

FIG. 4 is a block diagram showing an example of the above-described conventional automatic antenna switching apparatus. As shown in the figure, the automatic antenna switching device of the on-board TAKAN device has an antenna switching device 1 for selecting one of the received RF signals from two antennas A and B, and a reception device selected by the antenna switching device 1. RF
A receiving unit 2 for converting the signal a into a received video signal b; a azimuth and a distance measurement based on the received video signal b; outputting a measured value c thereof; and a measurement status signal indicating the measurement status at that time The azimuth / distance measuring unit 3 that outputs d and the antenna switching control unit 14 that generates and outputs an antenna switching signal e based on the measurement status signal d and controls switching of the antenna switch 1.

Next, the operation of the conventional automatic antenna switching device will be described. The receiving unit 2 receives the received RF signal a selected and taken out by the antenna switch 1, converts the frequency of the received RF signal a, detects the received RF signal a, and outputs a received video signal b. The azimuth / distance measuring unit 3 receives the received video signal b, calculates the azimuth and distance with respect to the ground takan device, and measures the measured value c indicating the calculation result.
And outputs a measurement status signal d indicating whether the calculation of the azimuth and the distance is performed normally.

[0007] The antenna switching control unit 14 outputs a measurement status signal d.
Is input, whereby the azimuth / distance measuring unit 3
When it is determined that the measurement of the azimuth and the distance is performed normally, the connection state of the antenna switch 1 is maintained, and when it is determined that the measurement is abnormal, the antenna that switches the antenna switch 1 is connected. The switching signal e is output. The antenna switching unit 1 receives the RF signal of the designated one of the antennas A and B according to the antenna switching signal e.
The signal is selected and output to the receiver 2.

Accordingly, when an abnormality occurs in the measurement by the azimuth / distance measuring unit 3 due to the reason that the reception electric field strength of the antenna selected by the antenna switch 1 is low, etc.
The other antenna will be selected.

[0009]

Generally, the level (reception electric field strength) of a takan signal received by each of two antennas A and B arranged at two different locations on the body of an aircraft depends on the attitude of the aircraft and the ground takan. Depending on the relative position with respect to the device, the level difference between the takan signals received at antennas A and B may be larger than a predetermined value, and the receiving level of the takan signal of the antenna which is not selected is selected. In some cases, the receiving level of the takan signal of the other antenna may be higher.

However, in the above-described conventional automatic antenna switching device, when the measurement of the azimuth and the distance is normally performed, the current antenna selection state is maintained, so that the non-selected side is selected. Even if the level of the Takan signal from the antenna is received stronger than that from the selected antenna, the azimuth of the signal from the selected antenna drops below a predetermined value. In addition, the antenna switching is not performed until the distance measurement is not normally performed, and the measurement result of the azimuth and the distance in this case may be unstable.

[0011] The present invention has been made in view of the above points,
An antenna automatic switching device that obtains stable azimuth and distance measurement results by switching to the antenna having a stronger received signal level among a plurality of antennas before azimuth and distance measurement is not normally performed. The purpose is to provide.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a 360 ° azimuth transmitted from a ground device.
Is the amplitude of the first sine wave in the first cycle of 1/15 second
The modulated first pulse train and the first pulse having a period of 1/135 second
A second pulse amplitude-modulated with a second sine wave having a period of 2
Represented by a composite wave with the train and transmitted in a specific direction
Receives RF signal containing azimuth reference signal at specified intervals
Connected to onboard equipment onboard the aircraft
An antenna , an antenna switch for selecting and outputting only a received RF signal from one antenna designated by an antenna switching signal among received RF signals from a plurality of antennas, and a receiving RF selected by the antenna switch A signal as an input signal, and the envelope has a first sine wave and a second positive
A pulse train that is amplitude-modulated with a synthetic wave with a sine wave, and a receiving unit that converts and detects a received video signal including an azimuth reference signal , and measures the azimuth and distance to the ground device based on the received video signal, A measuring unit for outputting a measurement status signal indicating whether or not the measurement has been normally performed; level detecting means for detecting a level of an azimuth reference signal included in the received video signal; and a plurality of antennas extracted from the level detecting means And a level comparator for comparing the level detection signals at the time of each selection, and selecting one of the plurality of antennas, and synchronizing with the azimuth reference signal included in the received video signal, among the plurality of antennas. Of non-selected antennas at a fixed period for a certain period of time, select the antenna with the highest received signal level based on the output comparison result of the level comparator, and When there is an abnormality in the measurement on the basis of the status signal is obtained by a configuration in which a control unit for generating output antenna switching signal for selecting the non-selected antenna.

In the present invention, the on-board device is an on-board takan device, and the azimuth reference signal is one of a main reference burst signal and a sub-reference burst signal included in the takan signal. It is preferable in that it is applied to one Takan of the radio navigation system.

According to the present invention, when applied to Takan, the azimuth reference signal is a sub-reference burst signal of the main reference burst signal and the sub-reference burst signal included in the Takan signal, and the level detecting means is a main reference burst signal. A position detector for predicting a generation timing of a sub-reference burst signal generated at an intermediate phase among a plurality of sub-reference burst signals periodically generated within one period of the reference burst signal, and an output timing of the position detector A point measurement unit that measures the level of the sub-reference burst signal included in the received video signal based on the signal can minimize the adverse effect on the onboard TAKAN device when switching to the non-selected antenna. Is preferred.

[0015]

According to the present invention, an unselected antenna among a plurality of antennas is selected by a control unit at a fixed period for a fixed period in synchronization with an azimuth reference signal included in a received video signal, and based on an output comparison result of a level comparator. Because the antenna with the highest received signal level is selected, even if the azimuth and distance measurement is performed normally, before the azimuth and distance measurement is not performed properly due to the decrease in the received signal level,
It is possible to automatically switch to a non-selected antenna having a high received signal level.

[0016]

Next, an embodiment of the present invention will be described. FIG. 1 is a block diagram showing an embodiment of the automatic antenna switching device according to the present invention. In the figure, the same components as those in FIG. 4 are denoted by the same reference numerals. As shown in FIG. 1, the present embodiment is installed at different positions on the fuselage of an aircraft and has two antennas A and B connected to an onboard takan device, and one of the RF signals received from these antennas A and B. And the reception R selected by the antenna switch 1.
A receiving unit 2 that converts the F signal a into a video signal b, an azimuth / distance measuring unit 3 that measures an azimuth and a distance based on the received video signal b, and outputs a measurement value c and a measurement status signal d, respectively; The ARB position detector 4 receives the received video signal b to detect and output the ARB timing signal f, and measures the level of the sub-reference burst signal (ARB) included in the received video signals from the antennas A and B, respectively. An ARB level measuring unit 5 that outputs level signals g and h of
The level comparator 6 which compares the ARB level signals g and h from the antennas A and B and outputs a level comparison result i, and receives the measurement status signal d, the ARB timing signal f and the ARB level comparison result i, respectively. And a multi-condition antenna switching control unit 7 for generating an antenna switching signal e corresponding to these.

Next, the operation of this embodiment shown in FIG. 1 will be described with reference to the waveform diagram of the received video signal in FIG. 2 and the timing chart in FIG. Now, in FIG. 1, the reception RF from the antenna A is
It is assumed that a signal is selected, supplied to the receiving unit 2, and subjected to frequency conversion and detection. At this time, antenna A is referred to as “selected antenna” and antenna B is referred to as “non-selected antenna”.

Here, the ground Takan device combines a pulse train amplitude-modulated in a 360 ° azimuth with a sine wave having a period of 1/15 second and a pulse train amplitude-modulated with a sine wave having a period of 1/135 second. A main reference burst (MRB: Ma) which is represented by a wave and transmitted in a specific direction to serve as a reference for direction measurement.
in Reference Burst signal and auxiliary reference burst (Auxiliary Reference)
Burst) signal at a specified interval (MRB = 1 time, ARB = 8 times per one cycle of 15 Hz).
The frequency is converted to the F band and the signal is always transmitted.

Therefore, the reception RF signal a received by the antenna A connected to the onboard airplane device and further selected by the antenna switch 1 is frequency-converted and detected by the reception unit 2, as shown in FIG. As shown, the envelope is 15H
A received video signal b which is an amplitude-modulated pulse train represented by a composite wave of a sine wave of z and a sine wave of 135 Hz, and in which the MRB signal M and the ARB signal A are respectively included at the above specified intervals. Is obtained. In addition, as shown in FIG.
One ARB signal is a burst signal composed of 12 pulses each having a pulse width of 3.5 μs and a pulse train output at a period of 12 μs.

The azimuth / distance measuring unit 3 detects the timing of the MRB signal M and the ARB signal A in the received video signal b, measures the phase relationship between these signals and the 15 Hz and 135 Hz modulated signals, Measure the bearing to the device. The azimuth / distance measuring unit 3 measures the reciprocating time of a pulse transmitted from the on-board Takan device and transmitted as a response from the ground Takan device, and measures the distance to the ground Takan device based on the measured time. The measurement results of these azimuths and distances are output as measurement values c. In addition, the azimuth / distance measuring unit 3 outputs a measurement status signal d indicating whether or not the measurement has been normally performed at the time of this measurement.

On the other hand, the ARB position detecting section 4 outputs an ARB signal (A in FIG. 2, FIG. 3 (A)) included in the received video signal b.
3 is detected, and one of the ARB timings (here, the fourth timing) existing eight times in one T of 1/15 second is predicted, and at this timing, the ARB timing signal f is set as the ARB timing signal f in FIG. Output as shown in (B).

The multiple condition antenna switching control unit 7 receives the ARB timing signal f as an input signal and
An antenna switching signal e for switching to an unselected antenna (here, B) is generated only during a period in which the ARB signal is received once every 2 T, and the antenna switching unit 1 and the ARB level measurement unit 5 Respectively. As shown in FIG. 3 (C), this antenna switching signal e is one in two cycles.
The signal is at a high level only during a period in which the ARB signal is received at a rate of times, and at a low level during other periods.

The ARB level measuring section 5 receives the above-mentioned received video signal b, antenna switching signal e and ARB timing signal f as input signals, and at the timing designated by the ARB timing signal f, the peak level of the received video signal b, ie, A peak level of the ARB signal is measured, and A is measured based on the level of the antenna switching signal e.
When it is determined that the peak level of the RB signal is included in the reception signal of the selected antenna A, the measured peak level is output as the antenna A level signal g.
The peak level of the measured ARB signal is unselected antenna B
, The measured peak level is output as the antenna B level signal h.

The level comparator 6 compares the level of the antenna A level signal g with the level of the antenna B level signal h at the timing specified by the ARB timing signal f, and compares the level comparison result i with the multiple condition antenna switching control section 7.
Output to

The multi-condition antenna switching control unit 7 calculates a measurement status signal d, an ARB timing signal f, and a level comparison result i.
Are received as input signals, and the time when the ratio of the peak level h of the ARB signal from the non-selected antenna B higher than the peak level g of the ARB signal from the selected antenna A increases for a certain time or more, The antenna switching signal e is changed to a high level so as to switch the selected antenna from the current A to B.

In some cases, the calculation of the azimuth and the distance may not be performed normally under conditions other than the reception level. When it is determined that the antenna is not obtained by normal calculation, the antenna switching signal e is changed to the high level so that the selected antenna is switched from the current A to the current antenna B. The antenna switching device 1 performs a switching operation such that the antenna A is selected when the antenna switching signal e is at a low level, and the antenna B is selected when the antenna switching signal e is at a high level.

As described above, according to this embodiment, when the ratio of the peak level of the received ARB signal of the selected antenna that is higher than the peak level of the received ARB signal of the non-selected antenna continues for a predetermined time or more, the azimuth / distance is determined. Even if the normal measurement is performed by the measuring unit 3, the switching operation is performed so as to select the non-selected antenna that can obtain the received signal having a higher level than the received signal at the present time. Measurement results can be obtained.

In the present invention, since the reception strength of the selected antenna and the reception strength of the non-selection antenna are respectively detected, it is necessary to periodically select the non-selection antenna to detect the reception strength of the non-selection antenna. Since there is a possibility that reception may not be possible when an antenna is selected, in order to reduce such an adverse effect as much as possible, in the above embodiment, 1
/ 15 seconds An ARB signal of period t (= 1/135 seconds) transmitted at a rate of 8 times in one cycle T is an unselected antenna only during a period in which an ARB signal is received once every two periods 2T. Is detected, and the peak level of the ARB signal at that time is detected.

However, the present invention is not limited to this. In order to detect the reception strength of an unselected antenna,
For example, it is also possible in principle to periodically select an unselected antenna at nT (where n is an integer of 2 or more) and detect the MRB signal level at that time. Further, the total number of antennas to be switched can be three or more.

[0030]

As described above, according to the present invention,
The control unit selects an unselected antenna among a plurality of antennas at a fixed period for a fixed period in synchronization with the azimuth reference signal included in the received video signal, and determines the antenna having the highest received signal level based on the output comparison result of the level comparator. By selecting, even if the azimuth and distance measurement is performed normally, before the azimuth and distance measurement is not performed properly due to the decrease in the received signal level, the unselected antenna with the higher received signal level is automatically , It is possible to obtain stable measurement results of the azimuth and the distance.

[Brief description of the drawings]

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

FIG. 2 is a waveform diagram of a received video signal.

FIG. 3 is a timing chart for explaining the operation of FIG. 1;

FIG. 4 is a block diagram of an example of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Antenna switch 2 Receiving part 3 Azimuth / distance measuring part 4 ARB position detecting part 5 ARB level measuring part 6 Level comparator 7 Multiple condition antenna switching control part

Claims (3)

(57) [Claims] 1. The 360 ° direction transmitted from the ground equipment
The first sine wave of the first period of 1/15 second
A width-modulated first pulse train and one cycle of 1/135 second
A second pulse amplitude-modulated with a second sine wave of a second period
And transmitted in a specific direction.
Received an RF signal containing the azimuth reference signal
Connected to the on-board equipment on board the aircraft
And antenna, of the received RF signals from the plurality of antennas, the receiving R from one antenna indicated by the antenna switching signal
An antenna switch for selecting and outputting only the F signal, receiving the received RF signal selected by the antenna switch as an input signal, and forming an envelope with the first sine wave and the second positive
A pulse train amplitude-modulated by a composite wave with a sine wave
A receiver for converting and detecting the incoming video signal comprising a serial orientation reference signals, the azimuth and distance measuring for said ground device based on the received video signal, the measurement condition signal indicating whether the measurement was successful And a level detector that detects the level of the azimuth reference signal included in the received video signal, and a level detection signal when each of the plurality of antennas extracted by the level detector is selected. A level comparator for comparing levels, selecting one of the plurality of antennas, and keeping a non-selected antenna among the plurality of antennas in synchronization with the azimuth reference signal included in the received video signal The antenna is selected for a predetermined period in a cycle, the antenna having the highest received signal level is selected based on the output comparison result of the level comparator, and the measurement state is selected. A control section for generating and outputting the antenna switching signal for selecting a non-selected antenna when it is determined that there is an abnormality in the measurement based on the status signal. 2. The on-board device is an on-board takan device,
2. The automatic antenna switching device according to claim 1, wherein the azimuth reference signal is one of a main reference burst signal and a sub-reference burst signal included in the takan signal. 3. The onboard device is an onboard takan device,
The azimuth reference signal is a sub-reference burst signal of the main reference burst signal and the sub-reference burst signal included in the Takan signal, and the level detection means periodically generates a plurality of signals in one cycle of the main reference burst signal. A position detector for predicting the generation timing of the sub-reference burst signal generated at an intermediate phase among the sub-reference burst signals to be generated, and a position detector included in the received video signal based on an output timing signal of the position detector. 2. The automatic antenna switching device according to claim 1, further comprising a level measurement unit that measures a level of the sub-reference burst signal.