JPH02309286A - Measuring method of radiation and radiometer - Google Patents

Abstract

PURPOSE:To attain stabilization of a sufficiently high gain by a method wherein a noise wave radiated from an object is received by an antenna, a reception signal thus obtained is converted into an intermediate frequency signal and then amplified, further this signal is converted into a low frequency signal and then a compensation processing is applied to the low frequency signal on the basis of the temperature of an amplifier element. CONSTITUTION:A temperature compensation signal is generated on the basis of a temperature detection signal outputted from a temperature sensor 10 fitted to the casing of an IF amplifier 4. Besides, a circuit 11 for generating a compen sation signal to be supplied to a divider 7 is provided. When a gain of the IF amplifier 4 has a variation coefficient of (1-alphat) (where alpha denotes a tempera ture coefficient and (t) a surface temperature of the casing of the IF amplifier 4), for instance, a function of m(1-alphat) (where (m) denotes an arbitrary constant) is set beforehand for said compensation signal generating circuit 11, and it outputs the temperature compensation signal of m(1-alphati) on the basis of a detected temperature (ti).

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a radiation ti#1 method and a radiometer, and more specifically, it simplifies the configuration of the part that processes high-frequency signals and enables stable object detection. The present invention relates to a novel radiation measurement method and radiation core 1 that can obtain signals.

<Prior art and problems to be solved by the invention> It has been known that objects emit noise radio waves with an intensity determined based on their own emissivity and physical temperature. 2. Description of the Related Art Radiometers have been provided that detect the presence or absence of a target object by receiving radiated noise radio waves with an antenna, supplying the received signal to a receiver, performing amplification processing, etc., and eliminating the output signal.

In this case a, the output signal P has the Boltzmann constant, 1 receiver gain 61, receiver band 81, receiver internal noise temperature TS, and target object noise temperature T)l. P-1c-〇 (TM + Ts ) B.

FIG. 5 is a block diagram showing a conventional example of a radiometer, in which a reference noise source (
The reference noise signal output from the RF switch (23)
4) selectively supplies the signal to the mixer (25) and mixes it with the local oscillation signal output from the local oscillator (2G). Then, the mixed signal is sent to an IF amplifier (27
) for amplification, then supplied to a detector (28) to extract the low frequency signal, reduce fluctuations with an integrator (29), amplify it with a DC amplifier (30), and send it to a signal processing system (
31) to detect the presence or absence of a target object. Further, the gain of the IF amplifier (27) is feedback-controlled by supplying a feedback signal output from the signal processing system (31) to the IF amplifier (27) through the AGC circuit (32).

If the radiometer has the above configuration, the signal processing system (31)
By monitoring the level fluctuations of the signal supplied to r
Gain fluctuations of the F amplifier (27) can be detected, and when gain fluctuations are detected, a feedback signal for compensating for the gain fluctuations is output, so the gain of the 1F amplifier (27) can be maintained constant. Therefore, if the gain of the IF amplifier (27) is maintained constant in this way and the received signal is selected by the RF switch (24), the target object will be detected based on the signal output from the DC amplifier (30). It is possible to detect the presence or absence of

(However, in the radiometer with the above configuration, it is assumed that the reference noise signal does not fluctuate, so the drive circuit (22)
It is also necessary to stabilize the reference noise source (23) with high precision, and in order to satisfy this requirement, it is necessary to house the drive circuit (22) and reference noise source (23) in a thermostatic chamber. As a result, the entire /ik shooting system became larger,
The scope of applicability is limited to large and middle schools. Further, the RF switch (24) selects one of two types of high frequency signals, the reference noise source (23) outputs the reference noise signal, and the AGC
Since the circuit (32) supplies a gain control signal to the IF amplifier (27), it is necessary to use a large number of components that can be used in high frequency bands, which not only increases the size of the radiometer as a whole but also makes it expensive. Become.

<Object of the invention> This invention was made in view of the above problems,
Significantly reduces the required number of components that can be used in the
Moreover, it is an object of the present invention to provide a radiometer j1 method and a radiometer that can achieve sufficiently high gain stabilization.

Means for Solving the Problems> Radiation needle fl1 of the present invention for achieving the above objects
One method is to convert the received signal No. 13 obtained by receiving the noise radio waves radiated from the target object with an antenna into an intermediate frequency signal, amplify it, further convert it into a low frequency signal, and then change it to the temperature of the amplification part. This method performs compensation processing on low frequency signals based on the

Emissions of this invention to achieve the above objects: 1.
an antenna that receives noise radio waves radiated from a target object; a first signal converter that generates an intermediate frequency signal based on a received signal output from the antenna and a predetermined local oscillation signal; and a first signal converter that amplifies the intermediate frequency signal. an amplification means; a second signal conversion means for generating a low frequency signal based on the amplified intermediate frequency signal; a compensation signal generation means for generating a temperature compensation signal based on the temperature of the amplification means; and compensation means for temperature-compensating the low frequency signal to obtain an object detection signal.

With the above radiation measurement method, the received signal obtained by receiving the noise radio waves emitted from the target object with an antenna is converted into an intermediate frequency signal, amplified, and then converted into a low frequency signal. However, rather than controlling the amplification factor for the intermediate frequency signal, a compensation signal is obtained based on the temperature of the amplifier section, and the low frequency signal is determined based on the compensation signal obtained. By performing compensation processing on this, it is possible to obtain a measurement signal similar to that obtained when the amplification factor is controlled to be constant.

A radiometer with the above configuration generates and amplifies an intermediate frequency signal based on the received signal output from the antenna and a predetermined local oscillation signal, then converts it to a low frequency signal, and then performs temperature compensation. Therefore, the number of components that process high frequency signals can be reduced, and moreover, highly accurate object detection can be performed.

To explain in more detail, as a result of investigating the fluctuation of the output of the radiometer with the AGC circuit removed, the inventor of the present invention found that as time passes after starting the radiometer, as shown in Figure 6. It has been found that the output signal level decreases. Assuming that the IF amplifier gain fluctuation has the greatest influence among the various causes that may cause the output signal level to fluctuate, we investigated the gain-temperature characteristics of the IF amplifier and found that the seventh As shown in the figure, it was found that the gain decreased linearly as the temperature rose, although there was some variation. That is, after the IF amplifier starts to be energized, the temperature rises due to the heat generated by the IF amplifier itself, and the gain decreases due to this temperature rise.

This invention was made based on the above knowledge,
Rather than controlling the gain of the IF amplifier as in the conventional example, the temperature of the IF amplifier is detected to obtain the gain change rate, and the final signal is compensated based on the obtained gain change rate. Therefore, the number of components that handle high frequency signals can be reduced, and the radiometer as a whole can be made smaller.

<Example> Hereinafter, embodiments will be described in detail with reference to the accompanying drawings showing embodiments.

FIG. 1 is a block diagram showing an embodiment of the radiometer of the present invention. A mixing signal outputted from the mixer C3) is supplied to an IF amplifier (4) as an amplifying means, and the amplified mixing signal is sent to a detector (3) as a second signal converting means. 5). And the detection 'J! The low frequency signal output from A(!b) is supplied to an integrator (6) to reduce fluctuations, and is supplied to a divider (7) as a compensation means.
) is amplified by a DC amplifier (8) and supplied to a signal processing system (9). In addition, a temperature sensor (10) attached to the casing of the IF amplifier (4)
) is provided with a compensation signal generation circuit (11) that generates a temperature compensation signal based on the temperature detection signal output from the circuit and supplies it to the divider (7). This compensation signal generation circuit (11
), for example, the gain of the IF amplifier (4) is (1-α1
) (where α is the temperature coefficient and t is the surface temperature of the casing of the IF amplifier (4)),
A function of m(1-αt) (where m is an arbitrary constant) is set in advance, and m(1-αt) is calculated based on the detected temperature t1.
i) outputs a temperature compensation signal.

The operation of the radiometer with the above configuration is as follows.

However, in the following explanation, the gain GIP of the IF amplifier (4) is G IF"-G O (1-α1) (however, G
O is a constant), the coefficient that combines the gains and conversion coefficients of components other than the IF amplifier (4) is A, the human noise temperature is T%, and the casing surface temperature of the IF amplifier (4) is tl.
It is assumed that

Therefore, if the compensation signal generation circuit (11) is not considered at all, mixing processing by mixer G), amplification by F amplifier (4), detection by detector (5), and integrator (
By performing the fluctuation reduction by 6) and the amplification by the DC amplifier (8), an output signal expressed as VO'-A-GIF·T-A-GO-(1-αtl)·T is obtained.

However, in the above embodiment, since the compensation signal generation circuit (11) in which the function m(]-αt) is preset is provided, the casing surface of the IF amplifier (4) detected by the temperature sensor 00) By supplying the temperature t1 to the compensation signal generation circuit (11), a temperature compensation signal m(1-αti) is supplied as a divisor to the divider (7). As a result, the signal vO output from the DC amplifier 3)
is VO-VO'/m (1-a t i )-(A
-GO/m)T, and a constant signal can be obtained regardless of the temperature change of the IF amplifier (4). That is, since the signal level changes depending only on the human noise temperature T, it is possible to reliably detect the presence or absence of a target object based on the signal level.

Figure 2 is a diagram showing the results of continuous measurement of a specific object kept at a constant temperature using the radiometer configured as shown in Figure 1.
It can be seen that a stable output signal is obtained regardless of the temperature fluctuation of the F amplifier (4).

FIG. 3 is an electric circuit diagram showing a specific example of the compensation signal generation circuit (11), in which the output current i (
However, i-βt) is supplied to the current-voltage conversion circuit (12), the output voltage v2 from the current-voltage conversion circuit (12) is supplied to the variable gain amplifier (13), and the gain ri1 t
The output voltage v3 from the amplifier (13) is supplied to the variable offset amplifier (14). Note that a predetermined voltage Vt is applied to the other input terminal of the current-voltage conversion circuit (12), and a variable voltage v5 is applied to the other input terminal of the variable offset amplifier (14). In addition, the current-voltage conversion circuit (12), variable gain amplifier (13), and variable offset amplifier (4) have large resistances R1, R3, and R5, respectively, and the variable gain amplifier (ia) , the input resistances of the variable offset amplifier (14) are R2 and R4, respectively, and only the resistance R3 is a variable resistance.

Therefore, if the temperature sensor 00) outputs a current i that changes in proportion to the temperature, the current-voltage conversion circuit (12
) outputs the voltage v2 of V2-Vl-i-R1, the variable gain amplifier (13) outputs the voltage v3 of V3 - (-R3/R2) V2, and the variable offset amplifier (14) outputs the voltage v3 of V4- A voltage v4 of (-R5/R4) V3 + (1+R5/R4) V5 is output.

Therefore, the voltage v4 finally output from the compensation signal generation circuit (11) is V4- (-RI R3R5/R2R4)βt+(R3
R5/R2R4) Vl + (1+R5/R4) V5, and Augly (R3R5/R2R4) Vl + (1+R5/R4) V5 B-(-RI R3R5/R2R4) β, then V4-A-Bt. . However, since the values of both A and B can be changed, Htlt can be adapted to the changing characteristics of the IF amplifier (4).

FIG. 4 is an electric circuit diagram showing a specific example of the integrator (6), the divider (7), and the DC amplifier (8).
As 6), a variable time constant is used, and the average value of the input signal is equal to the average value of the output signal by simply reducing the fluctuation of the output VD from the detector (5).

In addition, since an analog divider is used as the divider (7), and both input terminals are VD and V4, when the voltage V7 is applied to one output terminal, it is not supplied to the DC amplifier (8). The output voltage ■6 is VO-(VD/
V4) becomes V7. Further, as the DC amplifier S), a configuration in which a variable offset amplifier and a variable gain amplifier are connected in series is adopted.

Therefore, the output voltage VD from the detector (5) is VD
If it has the temperature dependence represented by -At -Blt, then VO-((At-Bit)/(A-Bt))V
7= [1+t (AI −A) + (Bl −B)
tl/(A-Bt)·]V7. As is clear from this equation, if At -A and BL -B are obtained by changing R3 and v5, the influence of temperature t can be completely eliminated.

Further, as is clear from the above description, since the signal for temperature compensation may be of low frequency, it is easy to downsize the components, and by extension, the radiometer as a whole can be easily downsized. Therefore, it can be easily incorporated into a small flying object or the like.

It should be noted that the present invention is not limited to the above-mentioned embodiments. For example, the temperature compensation pattern is stored in the rth memory, and the temperature detection f-th signal is digitized and the temperature compensation pattern is digitized from the memory based on the digital No. 1i. In addition to being able to read the compensation value, it is also possible to make various changes to the setting d1 without changing the gist of the invention.

<Effects of the Invention> As described above, the first invention performs compensation processing on low frequency signals based on the temperature of the amplification means, so compared to conventional methods, the part that requires high frequency signal processing is greatly reduced. It has the unique effect of being able to greatly reduce the width and also to perform highly accurate radiometer Δ-1.

The second invention omits the RF switch, reference noise source, and AGC circuit that handle high frequency signals, and is equipped with compensation signal generation means and compensation means that handle only low frequency signals, so it is expensive and large. The number of high-frequency components can be greatly reduced, the radiometer can be made smaller and more compact, and it has the unique effect of being able to perform highly accurate radiation measurements.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing an embodiment of this invention. Figure 2 is the result of continuous measurement of a specific object kept at a constant temperature using the radiometer with the configuration shown in Figure 1. Figure 3 is an electrical circuit diagram showing a specific example of a compensation signal generation circuit, Figure 4 is an electrical circuit diagram showing a specific example of an integrator, divider, and DC amplifier, and Figure 5 is a conventional radiometer diagram. FIG. 6 is a block diagram showing an example; FIG. 6 is a diagram showing changes in output characteristics of a radiometer; FIG. 7 is a diagram showing gain-temperature characteristics of an IF amplifier.

Claims (1)

[Claims] 1. An antenna (1) that transmits noise radio waves radiated from a target object.
After converting the received signal obtained by receiving the signal into an intermediate frequency signal, amplifying it, and further converting it into a low frequency signal, compensation processing is performed on the low frequency signal based on the temperature of the amplifying section (4). Characteristic radiation measurement method. 2. An antenna (1) that receives noise radio waves radiated from a target object, and a first signal conversion means that generates an intermediate frequency signal based on the received signal output from the antenna (1) and a predetermined local oscillation signal. (3), an amplifying means (4) for amplifying the intermediate frequency signal, and a second signal converting means (5) for generating a low frequency signal based on the amplified intermediate frequency signal.
, a compensation signal generation means (11) that generates a temperature compensation signal based on the temperature of the amplification means (4), and a compensation means (11) that performs temperature compensation on the low frequency signal based on the temperature compensation signal to obtain an object detection signal. 7) A radiometer comprising: