JPH0643746Y2 - Radar transponder - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a radar transponder that prevents transient operation that occurs when power is turned on to activate a search / rescue radar transponder. .

[Conventional technology]

In recent years, targeting 9 GHz band radar mounted on ships and aircraft, search and rescue radar transponders equipped on ships and lifeboats and life rafts mounted on ships have come into practical use. For the first time in the world, floating transponders have been approved as a commercialization testing station, and some fishing boats are equipped with them.

This usefulness has been recognized by the IMO (International Maritime Organization) and already
MO Performance standard (Resolution A. ***) MSC
53/24, Annex8 ・ COM 31 / WP.1.Annex5, radar transponders for living boats (hereinafter referred to as SART
Abbreviated. ) Performance requirements have been resolved.

This is a CCIR (International Radiocommunication Advisory Committee) recommendation [628]
By [TECHNICAL CHARACTERISTICS FOR S EARCH A ND
The main criteria for RESCUE R ADAR T RANSPONDERS] are those requirements should be provided on the operation is added.

Here, in order to help understanding of the present invention, a document describing the contents of the SART of the practical use test station will be introduced, and an example of the SART system will be described. The most recent one is 1985/85 of the monthly magazine “Shipbuilding Technology”.
1, vol.18 no.11 P44 to P51 have the description.

Currently, P48-P51 is approved as a commercialization testing station.
The former one is also functionally equivalent, and will be approved after some revision.

First of all, an example of the conventional SART system is shown in Fig. 2,
This will be described with reference to the waveform chart of each main part in FIG.

Conventionally, when a radar pulsed radio wave (a) is emitted as shown in FIG. 3, it delays by the time of its relative distance, and further attenuates as shown in FIG. 3 (b) to reach SART. The pulsed radio wave in FIG. 3 (a) is emitted by hundreds to thousands per second, but FIG. 3 shows only two of them.

SART is amplified to obtain the system trigger (c) with the leading edge as a reference, regardless of the pulse width of the pulsed radio wave (a).

Since SART targets horizontal polarization such as radar for ships, all antennas transmit and receive with the same polarization. Moreover, this directivity is non-directional in the horizontal plane, and a characteristic of 25 degrees or more is required in the vertical plane. That is, it is determined that the SART itself or a life raft or lifeboat equipped with the SART must always be directed to the radar even when exposed to the waves.

There is no special tuning circuit in the receiving part of the SART until the system trigger (c) is obtained, and it has a wide broadband property of approximately 9300 to 9500 MHz.

Therefore, if the arrival level of the radar wave (b) exceeds a certain value, all the radar waves in this frequency band can be received. Since there is a concern about a time delay mainly due to the frequency bandwidth of the video amplifier from the reception of the radar radio wave (b) to the derivation of the system trigger (c), this also has a wide band characteristic. ing.

The system trigger (c) is a transmission / reception switching circuit (2-input NAND, AND
Gate, etc.) and is added to a pulse train generation circuit for creating a time reference for frequency sweep.

This pulse train generation circuit is a combination of two sets of monostable multivibrators, one for setting the pulse width and the other for setting the interval between comb-shaped pulses. By examining the temperature coefficient of the integrated circuit for the monostable multivibrator, the resistor for setting the time constant and the capacitor, it is possible to obtain the one that is comparable to the stability of the crystal oscillator. There is also a method of using a crystal oscillator as a time reference, but because of the principle of the piezoelectric phenomenon of the crystal oscillator, it should be difficult to start it in the low temperature range of -20 ° C or lower, so reliability is the first priority.
It is wise to refrain from adopting SART, which must be emphasized.

The comb-shaped pulse (d) created here is divided by a counter to create a basic pulse (e) for response transmission having a pulse width of 100 μs.

The value of 100 μs is constant, and it does not change even if it is irradiated by radar radio waves with different pulse repetition frequencies. The upper limit is limited by this width, but if there are multiple radars in the same direction, it will change from the remaining time. It is possible to interrupt about 110 μs each. Also, about 8700 for one radar
It can be used for radars with pps (pulse repetition period of 115 μs or more) or less.

However, the pulse repetition frequency of the target radar is in the range of 300 to 3000 pps, which is almost equal to the audible frequency band of telephone grade, and even if many radars are viewed from SART, the azimuths are rarely the same, and Since there is no synchronization, no practical inconvenience occurs.

There is also a type that this basic pulse is also added to the low frequency power amplifier to drive the round speaker for the acoustic monitor, such as life raft and lifeboat, which is equipped with SART in advance and can be boarded by the victim, this acoustic pulse The monitor works effectively.

That is, each time the radar radio wave is irradiated, the sound of the pulse repetition frequency indicates the approaching condition of the ship or aircraft. (For example, when two types of radar are radiated, the radar antenna is rotating, so two tones are heard every few seconds, and at the same time a response radio wave as described later is emitted.) If it is high, it means that the pulse repetition frequency is high, so it is likely that you are searching for a short distance.If the sound continues for a relatively long time, side lobes other than the beam width of the radar antenna, minor lobes, etc. will also irradiate. Since it means that it is in a close range, it will be a chance to launch the signal red flame.

This information may also help encourage victims.

The basic pulse for response transmission (e) is slightly delayed by a pulse delay circuit and replaced with the pulse for response transmission (g).
This is because the pulse trailing edge expansion circuit output (f) in FIG.
As can be seen by looking at the time relationship with the response radio wave (j) of the SART, the time during which the response radio wave (j) is emitted is to break the loop with the reception system in terms of time.

Further, if the start of rising of the frequency-modulated signal (h) corresponding to the retrace time is included in the response radio wave (j), an unnecessary spectrum is likely to occur in addition to the occupied frequency bandwidth, and this is also for prevention. This response transmission pulse (g) is converted into power by an electronic switch (transistor for high speed switch),
Drives a microwave FM oscillator.

On the other hand, for the comb-shaped pulse train (d), the frequency modulation signal (h) is obtained by the sawtooth wave generation circuit of the charge / discharge time constant circuit, and pulse / frequency simultaneous modulation is performed on the microwave FM oscillator.

A microwave FM oscillator is an electronic tuning oscillator that uses a micro strip line for the resonance circuit, uses a varactor diode for frequency modulation, and uses a GaAs-FET for an oscillation element. Since the frequency modulation characteristic of the varactor diode is non-linear with respect to the applied voltage, pre-distortion (pre-emphasis) is given as shown in the waveform (h) of FIG. 3 in order to linearize the frequency sweep. This output is radiated from the transmitting antenna in all directions as response radio waves (j) and (k). (This radio wave emits a response radio wave of 9300 to 9500 MHz within a predetermined frequency range as shown in this figure, no matter which frequency the radar radio wave is irradiated.) When the radar catches this response radio wave, The video output (m) appears as a pulse train as shown in FIG. 3, and the equivalent pulse width τe of this pulse is as follows.

τe = B · t / Δf ∴B: Radar receiver pass bandwidth (Hz) t: Frequency sweep time (sec) per unit, 5 μs (5 × 10 ⁻⁶ sec) in this SART Δf: Frequency sweep In the range (Hz), this SART has 200 MHz (200
X 10 ⁶ Hz) For example, if the passband width of the radar receiver is 10MHz, the equivalent pulse width τe is 0.25μs, and 5μs in the PPI distance direction.
(Approximately 0.4 nautical miles) Twenty bright spot rows are displayed. In this case, the wider the passband width of the radar receiver, the larger the bright spot and the easier it is to find.

As can be seen from (k ') in Fig. 3, the time when the video output (m) appears depends on the operating frequency of the radar.
It varies within the range of μs.

That is, taking SART, which sweeps frequency from higher frequency to lower frequency, as shown in Fig. 3, the higher the operating frequency of the radar, the smaller the distance error of the bright spot appearing at the beginning of the pulse train, and the vicinity of 9300MHz. On the radar of, it will be reflected about 0.4 nautical miles behind the distance where SART exists.

This radar has a receiver pass band width of 3MHz, and the image frequency described later is also received. This is the image rejection filter (or SSB Mixe) in the microwave system of the radar receiver.
If r) is not inserted, it means that two waves can be received depending on the operating frequency, and the image will be 40 bright point sequences instead of 20 bright point sequences.

For example, the radar transmission / reception frequency was 9375 MHz, the intermediate frequency was 30 MHz, and the local oscillation frequency was set to the higher one.
If it is 405 MHz, the image frequency will be 9435 MHz, and two bright wave trains of 9375 MHz and 9435 MHz will appear alternately in the distance direction.

In any case, if such a large number of bright spot sequences are found, it means that a marine accident has occurred in the direction of the distance and the rescue is requested.

As the radar-equipped ship approaches its target,
The PPI image with a large number of bright spots spreads in a fan shape for the same reason as described for the acoustic monitor, and reaches almost 36 at a close range.
It will appear at 0 degrees all around. (On the SART side, the sound continues for a long time, or in the case of the floating type, the blinking type indicator light becomes almost continuous lighting state.) If this is the case, the direction of the SART is likely to be unknown on the radar side, so adjust the gain of the radar receiver. If you narrow down and reconfirm the azimuth, SART should be discovered right in front of you.

The IMO performance requirements require that the radar with a repetition frequency of 1000 pps have a response transmission capacity of 8 hours or more in a row after the device has been in a receiving state for 4 consecutive days after being activated.

Therefore, as the SART-dedicated battery, a lithium-based battery tends to be used in consideration of low-temperature characteristics and long-term storability. Lithium batteries are roughly divided into two systems, one of which has an elementary voltage of 3.6v.
Is a thionyl chloride system, and the other is a manganese dioxide system with an elementary voltage of 3.0v.

The former is superior in all respects such as power density, low temperature characteristics, long-term storability, etc., but if the container breaks, there is a concern that a lethal amount of toxic gas will be generated, so the operating environment, handlers, etc. For unclear SARTs, manganese dioxide lithium batteries are recommended.

As the power switch, a lead switch is often used for liferafts and lifeboats, and a mercury switch is often used for a floating type. A mercury switch attempts to open and close an electrode sealed in a container by moving mercury particles.

The flashing flashing indicator light for floating type shown in FIG. 2 is for putting an incandescent lamp, which is placed in a transparent lens and has a horizontal plane luminosity of about 1 candela, to blink. Therefore, in the daytime, it detects sunlight and turns it off, and it automatically blinks as the sun goes down.
However, when the radar radio wave is emitted, it interrupts according to the pulse regardless of whether it is day or night, and it is approaching continuous lighting. The container that encloses these is a completely waterproof type that also serves as a radome, but it also has a moisture absorption indicator lamp that gives an alarm when the relative humidity inside rises abnormally as a guide for regular inspection.

[Problems to be solved by the invention]

From the above literature and the description so far, it will be understood that there are many ways of thinking and methods even with this kind of simple device. All of the explanations so far have been made regarding a single operation after the SART is activated, and a case where one SART is irradiated with a large number of radar radio waves.

However, like a passenger ship, a large number of life rafts are installed, each SART is equipped with this, and a large number of SA
There is no discussion about the situations in which RTs (life rafts) are dropped and that they are in close range, and what happens when they respond to radar.

First, one SART was dropped and started up, then the second,
It is also necessary to consider the situation where SART starts up one after another on the third unit. Now, suppose that two SARTs are dropped, and the SARTs are dropped in a short distance one after another and activated (powered on) to the places where they are in the standby state for reception.

In the SART shown in Fig. 2, the monostable multivibrator of the pulse train generation circuit operates for only one shot without trigger (this phenomenon constitutes a monostable multivibrator that makes the current in standby zero). It must be devised so that the operating voltage rises exponentially with time.) Therefore, each one derives one transmission basic pulse (e) in FIG. 3 above. And radiate in all directions from the transmitting antenna.

Then, since the SART existing in the sea surface within a short distance of several tens of meters has a sufficient reception sensitivity, it is excited by these radio waves and reacts with each other to cause a chain reaction phenomenon. After 100 μs, the response operation is forcibly suppressed to about 105 μs by the pulse trailing edge expansion circuit, and since 5 μs reaches 750 m in distance, no problem occurs.

Further, even if a large number of SARTs are present in the above-mentioned close range, the response transmission pulses are in a synchronous relationship with each other even when receiving pulsed radio waves from many radars, and the pulse trailing edge expansion circuit is It works, so there is no problem.

This invention aims at preventing the above-mentioned "chain reaction phenomenon" and enabling simultaneous operation of a large number of units.

[Means for solving problems]

The radar transponder according to the present invention uses an antenna for receiving the radio wave of a pulse radar, a detector for detecting the microwave received by the antenna, a video amplifier for amplifying the output of the detector, and the amplified output. A pulse generation circuit that generates a predetermined pulse train signal, a frequency divider that divides the output of this pulse generation circuit to generate a basic pulse for response transmission, and a delay pulse for the basic pulse for response transmission by this frequency divider. Pulse delay circuit that generates a response transmission pulse, an electronic switch circuit that generates a drive pulse when the response transmission pulse is supplied, and a pulse train signal from the pulse generation circuit that supplies a sawtooth wave. A sawtooth wave generation circuit that generates a voltage and a drive pulse from the electronic switch circuit are input, and a position based on the sawtooth wave voltage is input. A microwave oscillator that performs frequency sweep in a frequency range, an antenna that emits a response radio wave signal swept by the microwave oscillator into space as the response radio wave, and is provided in the preceding stage of the electronic switch circuit, and from the pulse delay circuit. And a delay unit that delays the response transmission pulse by a predetermined time.

Further, in the radar transponder according to the present invention, the delay means and the electronic switch circuit are provided on the first NAND gate to which the response transmission pulse is input, and on the output side of the first NAND gate. The output of the delay circuit and the output of the delay circuit is supplied to one input side, and the output at the connection point of the resistor connected to the power supply side and the capacitor connected to this resistor is supplied to the other input side. And a second NAND gate to which is supplied.

[Action]

In this radar transponder, the transient operation prevention circuit can be realized with a simple circuit configuration in view of the need to simplify the configuration of the entire SART as much as possible.
If S ICs are used, the current consumption is negligibly small, and generally, even in MSI, four sets of the same ICs are enclosed in one package, so it can be said that there is almost no adverse effect on the entire SART.

[Example of device]

An embodiment of the present invention will be described in detail below with reference to FIG.

In FIG. 1, (1), (2) and (3) are resistors,
(4), (5), (6) are capacitors, (7), (8)
Is a shift type two-input NAND gate IC, and (9) is the high speed switch transistor PNP type.

(10) is a stabilizing circuit power supply, to which a voltage of about 5v to 6v is supplied. (11) is an input terminal for the response transmission basic pulse (e) in FIG. 2, and (12) is an output terminal for supplying a drive pulse to the microwave FM oscillator in FIG.

The IC of (7) acts for logic inversion, and the resistor (1) and the capacitor (4) form a pulse delay circuit between the input terminals of the IC (8). This delay time is as short as 100 ns or less.

When voltage is applied to the power supply terminal of (10) (supplied when SART is started), the resistor (2), the capacitor (5) and
The voltage at the connection point of the input terminal of the IC (8) rises to the exponential time with the time constant of the resistor (2) and the capacitor (4) once the voltage at the connection point of the IC (8) has risen to 0v. After the state of the logic H exceeding the "threshold value", it comes to function normally.

The output of the IC (8) is delayed from the waveform of the input terminal of (11) by the above-mentioned delay time, and the base of the transistor (9) is controlled by the pulse whose polarity is inverted to drive the microwave FM oscillator drive pulse (g). It can be obtained at the output terminal (12). The resistor (6) is for controlling the base current of the transistor (9), and the capacitor (3) is for improving the rise time of the pulse waveform.

Therefore, the above resistor (2), capacitor (5), IC
Since (8) causes the microwave FM oscillator drive pulse (g) to be temporarily stopped when SART is started,
As described above, even if the pulse train generation circuit operates for one shot when the power is turned on, it is cut off here.

The time for delaying the start-up does not have to be strictly determined, and if it is selected to an arbitrary value of about 0.1 second to 1 second, no practical problem will occur.

[Effect of device]

As described above, according to the present invention, it is possible to reliably prevent the "chain reaction malfunction phenomenon" that tends to occur when multiple SARTs operate simultaneously, and the circuit configuration is simplified, so the certainty required for SART It is of great practical value as it does not interfere with ensuring reliability or miniaturization.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a system diagram of an example of a conventional search / rescue radar transponder, and FIG. 3 is an operation of each part of the system diagram of FIG. It is a main part waveform diagram for explaining. In FIG. 1, reference numeral (2) is a resistor, (5) is a capacitor, and (8) is a two-input dummy NAND gate IC. In these drawings, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Scope of utility model registration request] 1. A radar transponder which receives a pulse radar radio wave and radiates a response radio wave into a space in a reception standby state, detects an antenna receiving the pulse radar radio wave, and a microwave received by the antenna. A detector and a video amplifier that amplifies the output of this detector,
A pulse generation circuit for generating a predetermined pulse train signal by the amplified output, a frequency divider for frequency-dividing the output of the pulse generation circuit to generate a basic pulse for response transmission, and the response transmission by the frequency divider. A pulse delay circuit that delays the credit basic pulse to generate a response transmission pulse, an electronic switch circuit that generates a drive pulse when the response transmission pulse is supplied, and a pulse train signal from the pulse generation circuit. When supplied with a sawtooth wave generation circuit that generates a sawtooth wave voltage and a drive pulse from the electronic switch circuit, a microwave oscillator that performs frequency sweep in a predetermined frequency range based on the sawtooth wave voltage. And the antenna that radiates the response radio wave signal swept by this microwave oscillator into the space as the response radio wave, and is installed in the preceding stage of the electronic switch circuit. It is, radar transponder, characterized in that a delay means for delaying the response transmission pulse from the pulse delay circuit by a predetermined time. 2. The delay means and the electronic switch circuit include one of a first NAND gate to which the response transmission pulse is input, a delay circuit provided on the output side of the first NAND gate, and The output of the delay circuit is supplied to the input side, and the output at the connection point of the resistor connected to the power supply side and the capacitor connected to the resistor is supplied to the other input side. The radar transponder according to claim 1, wherein the radar transponder is provided with a NAND gate.