JPS63144280A - Transponder - Google Patents

Abstract

PURPOSE:To obtain a sent wave which has an excellent S/N, optional pulse width, and an optional delay time by storing the intermediate frequency signal of a received radar wave temporarily in a RAM as a binary level waveform, and reading it properly and regenerating a sent wave. CONSTITUTION:A half-wave part of an input intermediate frequency signal is shaped by a waveform shaping circuit 20 into a binary signal waveform, which is further divided by (n) through a frequency divider 21 and inputted which is further divided by (n) through a frequency divider 21 and inputted to a RAM 22. The waveform is written in the RAM 22 by sampling the output waveform of the frequency divider 21 with a prescribed write clock signal and synchronizing a sampling frequency with addresses. Then a read mode is entered with a control signal sent from a controller 12 after the waveform corresponding to the intermediate frequench of the received wave is stored in the RAM 22, and respective addresses are read out with the same clock signal as that of writing to regenerate the same signal waveform, which is multiplied by (n) through a mutiplier 23 to obtain the original intermediate frequency. This intermediate frequench signal is passed through a mixer to regenerate and transmit the same sent wave as the received signal.

Description

[Detailed Description of the Invention] [Summary] In a transponder system applied to radar buoys, etc.,
In the conventional method, an analog delay line was used in the memory loop that stores the received radar waves, so it was difficult to vary the return time of the transmitted wave, and if the return time was increased, the S/N would be reduced.
was deteriorating.

The present invention was made to solve this problem.
The received radar waves are down-converted, binarized, and temporarily stored in a RAM, and the signals from the RAM are read out to reproduce the transmitted waves of the required time width.

[Industrial application field]

This invention is applied to radar buoys and the like. The present invention relates to improvements in transponders, and particularly to digital transponders that use RAM as a memory loop circuit for storing received radar waves and reproducing transmitted waves.

[Conventional technology]

Traditionally, radar buoys have been used to confirm the position of dropping fishing nets in deep-sea fishing and as markers for marine construction. This radar buoy has a so-called transponder configuration that has the function of sending back radio waves of the same or different frequency in response to reception of radar transmission waves from a radar device.

FIG. 3 is a block diagram showing the circuit configuration of a conventional transponder applied to such a radar buoy. Radar waves from a transmitting/receiving antenna 1 are passed through a circulator 2, a limiter 3, and a receiving amplifier 4 to a first mixer for down-conversion. Enter 5.

This first mixer 5 is connected to a local oscillator 6 to a directional coupler 7.
Since the local frequency is given through the input radar wave, an intermediate frequency corresponding to the difference between the frequency of the input radar wave and the local frequency can be obtained. Then, this intermediate frequency signal is passed through a directional coupler 8, and one side is input into a memory loop circuit 9.
The other signal is given to the memory loop circuit 9 as a control signal via an amplitude detector 10, an amplifier 11, and a controller 12.

Here, the memory loop circuit 9 has conventionally had a configuration as shown in FIG. 4. That is, a loop switch 92 is provided at an input end 91 of the intermediate frequency signal, and an amplifier 93 and a delay line 94 constitute a memory loop. A directional coupler 95 is provided in a part of the loop, and the output switch 1
3, the output can be taken out as appropriate. Thus, the delay time of the delay line 94 is set to a time corresponding to the pulse width of the input radar wave, and the input radar wave is If the time loop switch 92 corresponding to the pulse width of is connected to the input ■ side, and the connected switch is connected to the loop ■ side after the end of the pulse, the same frequency will be input into the loop following the duration of the input intermediate frequency. can be used to create a circular memory.

Returning to FIG. 3 again, when the output switch 13 is closed by a control signal from the controller 12, the intermediate frequency signal stored in the memory loop is output during that time.

After this output intermediate frequency signal is mixed with the local frequency from the local oscillator 6 by the second mixer 14 and up-converted to the same frequency as the high-power radar wave, it is passed from the transmitting amplifier 15 to the circulator 2 and antenna 1 to the radar equipment side (not shown). to fire.

Conventional radar buoys generally have the above configuration, but when trying to set the width of the returned pulse to several times the width of the receiving radar, the signal repeatedly passes through the loop consisting of the amplifier 93 and the delay line 94. Therefore, there is a problem that the signal-to-noise ratio (S/N) gradually decreases. Since the analog delay line for storing the voice signal is actually constructed using a long coaxial line as it is, there is a problem that the overall construction becomes unnecessarily large. Furthermore, if you want to vary the emission timing and time width of the return wave for each pulse of the received radar wave in order to characterize the display form on the radar scope, it is necessary to attach multiple intermediate taps to the delay line to switch the delay time. There is a problem in that the configuration and control method become extremely complicated.

[Problem that the invention seeks to solve]

Therefore, this invention is compact as a whole and has good S/N.
Therefore, it is an object of the present invention to provide a transponder that can obtain a transmission wave with an arbitrary pulse width and an arbitrary delay time.

[Means for solving problems]

Briefly stated, this invention, in order to achieve the above objectives, down-converts the received radar waves, binarizes them, stores them in RAM, and up-converts the signals read from this RAM and transmits them. It features a so-called digital memory loop circuit that reproduces waves.

[Effect]

In this invention, the intermediate frequency signal of the received radar wave is temporarily stored in the RAM as a binary level waveform, and the transmitted wave is reproduced by reading it as appropriate, so the S/N
No deterioration occurs at all.

Furthermore, the transmission pulse width and transmission delay time can be arbitrarily set by selecting the readout time.

〔Example〕

Preferred embodiments of the present invention will be described in more detail below with reference to the drawings.

FIG. 1 is a block diagram showing the basic configuration of main parts of a transponder according to the present invention, and shows the configuration of a characteristic part of the present invention newly adopted in place of the memory loop circuit 9 of FIG. 3. The half-wave part of the input intermediate frequency signal is shaped into a binary level signal waveform by a waveform shaping circuit 20 for binarization, and the frequency is further divided by 1/n by a frequency divider 21, followed by a RAM as a memory circuit. (random access memory) 22. To write a waveform to the RAM 22, the output waveform of the frequency divider 21 is sampled using a predetermined write clock signal, and the waveform level at each sample time is sequentially stored in each address as a digital signal of "1" or "0". It turns out. In other words, writing is performed by synchronizing the sampling frequency with the RAM address. Therefore, in this case, the frequency divider 21 has the function of compressing the band of the input intermediate frequency to the extent that it can be traced by the clock signal and converting it into a form that can be easily stored in the RAM, but of course it is limited to the extent that the intermediate frequency signal can be directly sampled and stored. If the frequency is sufficiently low, the frequency divider can be omitted.

After the waveform corresponding to the intermediate frequency of the received radar wave is thus stored in the RAM for a time corresponding to the pulse width of the received radar wave, the RAM is switched to the read mode by a control signal from the controller 12. If each address is sequentially read from the RAM 22 using the same clock signal as when writing, the same signal waveform can be reproduced, and when this signal is multiplied by n by the multiplier 23, it becomes the original intermediate frequency. Therefore, by passing this output intermediate frequency through the second mixer 14 described above with reference to FIG. 3, it is possible to reproduce and transmit the same transmission wave as the reception wave. Generally, when trying to store ultra-high frequencies such as radar waves using RAM, there is a limit to the frequency band that can be stored, which causes a problem, but in this invention, by combining a frequency divider and a multiplier, the intermediate frequency frequency It is also unique in that it can cover a wide range of bands.

Figure 2 is a waveform diagram for explaining the operation.
Furthermore, a waveform shaped into a binary level is shown. Also the second
Figure (b) shows a write time control signal to the RAM 22, and figure (c) shows a read time control signal. After a writing time corresponding to the pulse width τ of the received radar wave,
By appropriately setting the readout time t, it is possible to obtain an output intermediate frequency signal as shown in FIG. 3D corresponding to the readout time t.

Note that it is advantageous to provide a code modulator 24 attached to the controller 12 to modulate the output intermediate frequency with an identification code signal, in order to facilitate the identification of individual radar buoys on the radar equipment side. be.

〔effect〕

Now, as is clear from the above explanation, in short, the transponder of the present invention uses a memory circuit such as a RAM instead of a conventional analog delay line as a delay circuit for storing received radar waves. is small, lightweight, and inexpensive, and the pulse width and delay time of the transmitted wave to be sent back can be arbitrarily set to S/N reduction - ft L. Therefore, since the transmitted signal has less noise and can be easily transmitted with a specific code, the identification function is significantly improved.

Therefore, this invention exhibits great effects when applied to radar buoys and the like.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of main parts of a transponder according to the present invention, and FIG. 2 is a waveform diagram for explaining an example of operation, where (al is a binary intermediate frequency of a received radar wave). waveform, (bl is the write time signal waveform to the RAM, (C1 is the read time signal waveform, (d>output intermediate frequency signal waveform), and FIG. 3 is a block diagram showing the general configuration of a conventional radar buoy. Figure 4 is a block diagram showing the configuration of the same conventional memory loop circuit. In the figure, 1 is a transmitting and receiving antenna, 9 is a memory loop circuit, 12 is a controller, 93 is an amplifier, 94 is an analog delay line, 20 is a waveform shaping circuit for binarization, 21 is a frequency divider, 2
2 is a RAM, 23 is a multiplier, and 24 is a code modulator. Book 1ai4r:j5 L'F>Suak? “Q Hibiki (p7r
:h So 7m Fig. 1 7pflFJFlq-Weight 74 F ft9FfFfI
, Jεf-synth J Fig. 2

Claims (1)

[Claims] A transponder that emits required radio waves in response to reception of radar waves from a radar device, the transponder comprising a delay circuit that stores the received radar waves for a predetermined period of time and sends them back; a waveform shaper that binarizes the intermediate frequency signal; a frequency divider that divides the frequency of the binarized intermediate frequency signal; and a memory circuit that stores the frequency-divided signal from the frequency divider at a predetermined sampling period. comprising a controller that controls a write/read operation of the memory circuit in response to an amplitude detection signal of the received radar wave, and a multiplier that multiplies a signal waveform reproduced from the read signal of the memory circuit;
A transponder characterized in that a transmitted wave is regenerated from the output of the multiplier and sent back.