JPS5920693Y2 - Radar noise figure measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved radar noise figure measuring instrument.

A block diagram of a conventional radar is shown in FIG.

FIG. 2 is an operational waveform diagram of each part of FIG. 1.

In FIG. 1, a radar is shown centered around a noise figure meter that measures the noise figure of a radar receiver 1 during radar operation, that is, while receiving radar echoes.

The noise source 2 is a noise diode that generates noise when a noise source control pulse is applied by the noise source drive circuit 3.

Noise generated from the noise source 2 becomes an input signal Si to the radar receiver 1 via the coupler 4.

If the noise other than the noise source 2 to the receiver 1 is Ni, then
101 og(Si/Ni) is determined by noise source 2,
excess noise ratio
(hereinafter abbreviated as ENR) For example, when ENR is 30 dB and KTB = -114 dBm, the signal level is:
-114dBm + 30dB = -84dBm.

However, K is the Boltzmann constant, T is the equivalent input end noise temperature, and B is within the band of the receiver 1.

Note that when the coupling degree of the coupler 2 is 15 dB, the signal level is -84 dBm - 15 dB = -99 dBm.

However, it is OdBm-1mW.

Next, during the period when the radar is inactive, the noise source 2 is alternately generated and stopped, and the intermediate frequency output of the receiver 1 at that time is constantly monitored.
Find the ratio with o and have the meter 5 indicate the noise figure.

At this time, the intermediate frequency amplifier with AGC 6 receives the intermediate frequency output of the receiver 1 and amplifies the noise of the noise source 2 when the signal is stopped.

The detector 7 detects the output of the AGC frequency amplifier 6.

Next, the data 1 to the pulse generator 8 are connected to the main data generator Ri.
In response, the noise source drive circuit 3 is controlled by M;IJ, the noise gate I pulse is sent, the sample gate I~ pulse is sent to the intermediate frequency amplifier with AGC 6, and the sample hole toggle 1~ pulse is sent to the sample 0 hole 1 circuit 9. and AG to AGC gate 10
Generates Cge I pulse.

The sample hold 9 samples and holds the output of the detector 7 at a predetermined period using the sample hold gate pulse.

The repetition period of the sample hold gate pulse is:
+ of the repetition period of the noise gate pulse and is synchronized with the noise gate pulse.

For this purpose, the sample and hold circuit 9 alternately samples and holds the output of the detector 7 when the noise source 2 is generating noise and when the noise source 2 is stopped.

By the AGC gate I pulse, the AGC gate 10 transmits only the output when the noise source 2 is stopped out of the outputs of the sample and hold circuit to the next stage low-pass filter 11.

The output of the low-pass filter 11 is amplified by the AGC DC amplifier 12 and applied as an AGC control signal to the intermediate frequency amplifier 6 with AGC.

Therefore, the amplification degree of the intermediate frequency amplifier with AGC 6 is controlled by the output of the sample and hold circuit 9 when the noise source 2 is stopped, and therefore the output of the sample and hold circuit 9 when the noise source 2 is stopped is approximately a predetermined value. is maintained.

Next, the differential amplifier 13 amplifies the difference between the sample output of the sample and hold circuit 9 when the noise source 2 is generating noise and the sample output when the noise source 2 is stopped, and then It is transmitted to the low-pass filter 14 of the stage.

Next, the meter drive circuit 15 receives the output of the low-pass filter 14 and drives the logarithmic scale meter 5.

Since the meter 5 is calibrated (101o101o/Ni) at the time of CAL, the noise figure is displayed on the meter 5.

Next, as described above, FIG. 2 is an operational waveform diagram of each part of FIG. 1, in which the horizontal axis represents time and the vertical axis represents voltage.

FIG. 2A shows the radar main l/riga Ri, and FIG. 2B shows the transmitter pulses.

In FIGS. 2A and 2B, T1 is a rest period, T2 is a transmission period, and T3 is a reception period.

Next, FIG. 2C shows a noise source gate pulse, and noise is generated in the noise source 2 when the noise source gate pulse is at a high level.

Furthermore, the second diagram shows the intermediate frequency output of receiver 1, and the second diagram shows the intermediate frequency output of receiver 1.
Figure E shows the pulse to sample day 1, Figure 2 F shows the output of the detector 7, Figure 2 G shows the sample hold gate pulse, Figure 2 H shows the output of the sample hold circuit 9, In FIG. 2H, El is the sample-and-hold voltage when the noise source 2 is generating noise, and E2 is the sample-and-hold voltage when the noise source 2 is stopped.

Next, Fig. 2 shows the output of the differential amplifier 13, Fig. 2 J shows the AGC gate pulse, Fig. 2 shows the output of the AGC gate 10, and K 3 E 2 shows the AGC gate pulse. −
This is the output when the pulse to 1 is at a high level.

However, the conventional example shown in FIG. 1 has the following drawbacks.

In other words, if interference waves enter the receiver 1 from an external radar or the like in the same transmission frequency band via the antenna 16 and coincidentally coincide with each other at the time of sampling and holding the noise figure, the true value of the noise figure of the receiver 1 The meter 5 will show a different value.

In this case, if interference waves mix in while noise source 2 is generating noise, the value of the noise figure will be shown to be smaller than the true value, and conversely, if interference waves mix in while noise source 2 is stopped, The value of the noise figure is shown to be larger than the true value.

The object of the present invention is to eliminate the above-mentioned drawbacks, eliminate the influence of interference waves, and provide a radar noise figure measuring instrument that can always display the true noise figure.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 3 is a block diagram of an embodiment of the present invention, and FIG. 4 is an operational waveform diagram of each part of FIG.

In FIG. 3, a gate pulse generator 21 receives a radar main trigger Ri and generates gate pulses used in each circuit synchronized with the radar trigger.

The noise source 22 has a nozzle generating diode, and generates a predetermined RF noise using a noise source control pulse from the noise source driving circuit 23 having a cycle twice as long as the radar trigger.

This RF noise is supplied to the radar receiver 25 through the directional coupler 24, and the receiver 25 outputs an intermediate frequency output or 'A'.
It is supplied to an intermediate frequency amplifier 26 with GC.

The noise ratio at the input of the receiver 25 when the noise source 22 is operating and when it is stopped is the above-mentioned 10 log (Si/Ni), and the ENR of the noise source 22 is different from the noise source 22 when the receiver 25 is in operation.
is equal to the input minus the loss.

The intermediate frequency amplifier with AGC 26 is connected to the gate pulse generator 2
Controlled by a sample gate pulse from 1, a noise source 22 alternately samples the noise of the intermediate frequency output from the receiver 25 during activation and deactivation.

Further, the intermediate frequency amplifier with AGC 26 is set to a predetermined gain by the AGC signal.

Even if the level of the intermediate frequency output of the receiver 25 fluctuates within the range in which this AGC is possible, there will be no problem in measuring the noise figure.

The AGC signal is obtained by detecting and holding a sample of the noise when the noise source 22 is stopped, that is, the system noise of the receiver 25.

(The frequency characteristics of this intermediate frequency amplifier with AGC 26 match the intermediate frequency of the radar.

) Noise passing through the intermediate frequency amplifier 26 with AGC is detected by a detector 27, and the output of the detector 27 is applied to sample-and-hold amplifiers 28, 29, 30, and 31.

These sample and hold amplifiers 28, 29, 30.3
1 receives a sample hold gate pulse having a cycle four times that of the radar trigger from the gate pulse generator 21;
The signal is held at the timing of each gate I pulse.

The sample and hold amplifiers 28 and 29 perform sample and hold when the noise source 22 is in operation.

Further, the sample-and-hold amplifier 28 and the sample-and-hold amplifier 29 operate alternately.

The outputs of the sample and hold amplifiers 28 and 29 are compared by a comparator 32.

Further, the output of the sample and hold amplifier 28 is supplied to a selector 34 via a buffer amplifier 33.

Further, the output of the sample and hold amplifier 29 is supplied to a selector 34 via a buffer amplifier 35.

On the other hand, the respective outputs of the sample and hold amplifiers 28 and 29 are compared in level with each other by a comparator 32, and based on this, a sorting control circuit 36 controls the sorting device 34.
Among the outputs of the sample-and-hold amplifiers 28 and 29, the smaller one is used as the output of the selector 32.

The sample and hold amplifiers 30.31 perform sample and hold when the noise source 22 is stopped. Each output of the sample and hold amplifiers 30.31 is compared in magnitude by a comparator 37.

Furthermore, the output of the sample and hold amplifier 30 is supplied to a selector 39 via a buffer amplifier 38, while the output of the sample amplifier 31 is supplied to a selector 39 via a buffer amplifier 40.

Next, the sorting control circuit 41 is controlled by the output of the comparator 37, and controls the sorting device 39 so that the smaller of the outputs of the sample-and-hold amplifiers 30 and 31 is set as the output of the sorting device 39.

Next, the differential amplifier 42 connects the output of the selector 34 with the output of the selector 3.
For example, the difference between the values corresponding to the logarithm of the surface output is amplified.

The output of the differential amplifier 42 is supplied to a low-pass filter 43, and the output of the low-pass filter 43 is supplied to a meter drive circuit 44, which drives the digital display meter 4.
Drive 5.

By doing this, 101 og (Si/Ni
) is calibrated in advance during CAL, and the output of the differential amplifier 42 is 10 l og (So/No) during AUTO.
By indicating this on the meter 45, the noise figure of the receiver can be measured.

Next, the output of the selector 39 is supplied to a low-pass filter 46, the output of the low-pass filter 46 is supplied to a DC amplifier 47, and the output of the DC amplifier 47 is used as an AGC signal to determine the amplification degree of the intermediate frequency amplifier 26 with AGC. Control.

By CAL adjustment, this AGC signal is
Set Olog(Si/Ni).

Next, in FIG. 4, FIG. 4A shows radar main 1 to Riga R.
Figure 4B shows the noise source GaI pulse.

Note that the transmitter pulses are the same as those in FIG. 2B, and will therefore be omitted.

FIG. 4C shows the received intermediate frequency output. In FIG. 4C, the X part shows the interference wave component received by the antenna 48 when the noise source 21 is in operation, and the Y part shows the interference wave component received by the antenna 48 when the noise source 21 is stopped.

Figure 4 shows the sample gate pulse that controls the intermediate frequency amplifier with AGC 26, Figure 4E shows the output of the detector 27, and Figure 4F shows the sample and hold gate pulse that controls the sample and hold amplifier 28. , FIG. 4G shows the output EIO of the sample-and-hold amplifier 28;
Figure H shows the sample-and-hold gate pulse that controls the sample-and-hold amplifier 29, Figure 4 I shows the output of the sample-and-hold amplifier 29, and Elf in Figure 4
indicates the voltage increased by the interference wave component X.

Next, FIG. 4J shows the output of the selector 43.

In this case E 1o < E 11.

Next, FIG. 4 shows the sample-and-hold gate pulse that controls the sample-and-hold amplifier 30, the fourth diagram shows the output E12 of the sample-and-hold amplifier 30, and FIG.
shows the sample-and-hold gate pulse that controls the sample-and-hold amplifier 31, and FIG. 4N shows the output of the sample-and-hold amplifier 31, and in FIG. 4N, E13 shows the voltage increased by the interference wave component Y.

FIG. 4O shows 2E12 at the output of the selector 39.

In this case, E1°<E13.

FIG. 4 P shows the output of the differential amplifier 42 as 3 (K, E 1
0-K2E, 2), FIG. 4Q shows 4 (KIEIOK2E12) at the output of the meter drive circuit 44, and FIG. 4R shows 5E12 at the AGC signal.

Note that 1. 2. 4. and 5 each indicate a predetermined value.

As described above, according to the present invention, received interference wave components are divided into comparators 32, 37, screening control circuits 36, 41 . Since the filters 34 and 39 completely eliminate interference waves, even if interference waves enter the receiver, the true noise figure of the radar can be measured.

Therefore, the true noise figure of the radar can be measured without being hindered by the interference even when the radar is actually installed in a place where there are many interference waves.

Therefore, the practical effects of the present invention are extremely large.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the conventional example, FIG. 2 is an operation waveform diagram of each part of FIG. 1, FIG. 3 is a block diagram of an embodiment of the present invention, and FIG. FIG. 21... Gate pulse generator, 22...
・Noise source, 23...Noise source drive circuit, 24...
...Coupler, 25...Receiver, 26...
...Intermediate frequency amplifier with AGC, 27...Detector, 28.29, 30.31...Sample and hold amplifier, 32°37...Comparator, 33,
35, 38, 40...Buffer amplifier, 3
4.39... Sorter, 36.41...
Selection control circuit, 42...Differential amplifier, 43...
...Low pass filter, 44, Meter drive circuit, 45...Meter, 46...Low pass filter, 47...DC amplifier, 48・・・・・・
··antenna.

Claims (1)

[Scope of utility model registration request] a receiver that receives reflected waves from the target of radar transmitted waves;
An amplifier that amplifies the output signal of this receiver, a detector that detects the output signal of this amplifier, and a detector that operates during the radar idle period and alternately repeats generation and stop of noise at a predetermined period and detects the generated noise. noise generating means for supplying to the receiver; and a gate pulse signal generating circuit that generates the Gate I pulse signal of the predetermined period and supplies the Gate pulse signal to the amplifier in synchronization with the noise generation timing. , each connected to the detector and having the predetermined cycle interval and sampling the detected output at different times.
A plurality of sample 0 hole 1 circuits are used to sample and hold the output signals of the plurality of sample and hold circuits, and the signals obtained by sampling and holding the detection output when the noise occurs are compared with each other, and a signal with a low level is selected and output. a first means, and a second means for comparing the signals obtained by sampling and holding the detection output when the noise stops among the output signals of the plurality of sample and hold circuits, and selecting and outputting a signal with a lower level; , means for indicating a noise figure to which the output signal of the second means and the output signal of the first means are supplied.