JPS61209362A - Multichannel microwave radiometer - Google Patents

Abstract

PURPOSE:To reduce the outer shape dimension, wt. and power consumption of a radiometer, by using a multichannel comparing noise source in the correction of the high temp. side of a multichannel microwave radiometer and making it possible to use said noise source in common to each channels. CONSTITUTION:When the switch SW8 of a channel chB is connected to a (3)-side, the noise temp. of a multichannel comparing noise source B is guided to a receiver 10 and voltage V0 is generated in the receiver 10. Next, the switch SW8 of the channel chB is changed over from the (3)-side to a (2)-side and, when the switch SW7 of a channel chA is in the (3)-side, correction temp. T1 is guided to the receiver from a dummy load 11 and, when in the (2)-side, the temp. TA of an antenna 1 is guided to the receiver 10 to respectively generate voltages V1, V. Temp. sensors are attached to the noise source 13 and the dummy load 11 to obtain respective input temp. T0 and T1 of the receiver 10. The temp. TA can be calculated from a predetermined formula by using temps. T0, T1 and voltages V0, V1, V. As mentioned above, the noise source 13 is used in a high temp. side correction source to reduce the standard noise source and correction source change-over switch of each channel and, because the noise source 13 is used in common to each channel, one comparing noise can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement of a multi-channel microwave radiometer that is mounted on a flying object such as an artificial satellite and performs remote sensing.

[Conventional technology]

First, a two-channel microwave radiometer among conventional multi-channel microwave radiometers of this type will be described.

Figure 2 is a block diagram showing a conventional two-channel microwave radiometer. In Figure 2, (1) is a receiving antenna, (2) is a skyhorn which is a low temperature side noise source, and 13.
1 and 141 are branching filters A, respectively.

B, 15+ is a standard noise source which is a high temperature side noise source, (6
1 is the comparison noise source, +71, (8), +91
ti switches A and B, respectively.

C and αQ are receivers. Note that each channel from the branching filters A and B of 131 and 141 to the receiver of α has the same configuration.
Let's call it channel B.

Next, regarding the operating principle, only channel A will be described for convenience of explanation.

Generally, objects in the natural world emit electromagnetic waves, and the intensity of the radiation is closely related to the brightness temperature of the object. The antenna temperature T received by the receiving antenna in Fig. 2 (11)
A is the distribution of brightness temperature TB (Ω) of the object surrounding the receiving antenna (ll'i) and the gain function G of the receiving antenna (11).
(Ω) using.

It is expressed as Here Ω is the solid angle.

When the switch A (7) is connected to the ■ side, the received antenna temperature TA goes to the switch (8). Switch B (8) is connected to the ■ side at a certain moment.

In the next moment, the operation connected to the ■ side is repeated at several hundred Hz. In addition, a comparison noise source (6) that generates noise at a relatively high temperature and a constant temperature To is connected to the ■ side of the switch B (8), and a receiver αQ that is synchronized with this switch switching operation is connected.
The temperature To of the comparison noise source (6) is measured through the synchronous detector in
It is a necessary condition to know the antenna temperature TAO value.
This value can be found by using the output voltage v'6 generated by the receiver +1 (1 yen) and going through the following procedure.

First, switch the connection of switch A (7) from the ■ side to the ■ side. Sky horn (2) when switch C (9) is on side
When the antenna temperature T1 from the center is on the side (■), the noise temperature T2 of the standard noise source (5) is guided to the receiver a1.

A voltage v proportional to the temperature difference with the comparative noise source (61)
1 and v2 occur within the receiver ao. If the skyhorn (2) is always directed toward the cooling space of space, its brightness temperature is a known quantity as a function of frequency, and at the same time, the gain function of the skyhorn (2) itself is also known. Therefore, the input temperature T+ of the receiver αG for these seven wires is
On the other hand, the noise temperature of the standard noise source (5) can also be determined by attaching a temperature sensor to the standard noise source (5) and monitoring it to determine the input temperature T2 in the receiver aI.
t-can be known. Note that TI < T2 < To a
There is a relationship of Vt>V>Vz) a Tl e T2
If sv+ * ”2 and V are known, the antenna temperature T
A can be found from the following equation.

In the above description, for convenience of explanation, it is assumed that there is no loss in the RF circuit such as a switch.

[Problem that the invention seeks to solve]

As is clear from the above explanation, the skyhorn (2) and the standard noise source (31 is a calibration noise source used to determine the antenna temperature TA) are used to generate microwaves using these two calibration noise sources. The radiometer is being calibrated.

However, in this conventional multi-channel microwave radiometer, a standard noise source (5) and a comparative noise source (6) are used for each channel.

A switch (8) is required to switch between the skyhorn (2) and the standard noise source (5), which increases weight and external dimensions and increases power consumption. There was a problem in that the mounting position on the satellite was very limited because it had to be placed facing the space cooling space where it would not be exposed to heat.

The present invention has been made to solve these problems by improving the calibration source of a multi-channel microwave radiometer.

The purpose of this project is to obtain a multichannel microwave radiometer with low power consumption and a low-temperature calibration source that can be installed anywhere on the satellite.

[Means for solving problems]

The multi-channel microwave radiometer according to the present invention eliminates the standard noise source, uses a multi-channel comparison noise source for high-temperature side calibration, and has a configuration in which this multi-channel comparison noise source can be used commonly for each channel. Adashi, furthermore,
A radiation-cooled dummy load covered with a thermal insulator is used as the low-temperature side calibration source.

[Operation] In the present invention, by using a multi-channel comparison noise source signal as the high temperature side calibration source, it is possible to reduce the number of switches for switching between the standard noise source and the calibration source for each channel by one.

Furthermore, since the multi-channel comparison noise source is commonly used for each channel, the number of comparison noises can be reduced by one.

Furthermore, by using a dummy load that performs radiation cooling, it is possible to generate a low-temperature side calibration signal that corresponds to the space cooling space.

〔Example〕

FIG. 1 is a block diagram of a two-channel microwave radiometer showing an embodiment of the present invention. fil to σO are exactly the same as the conventional device described above. αυ is a radiation cooling dummy load, α3 is a radiation cooling dummy load,
A thermal insulator that prevents heat from the earth, (T3 is a multi-channel comparison m sound source, (14) u duplexer C.

Next, regarding the operating principle, only the channel person will be described for convenience of explanation.

First, when switch B (8) is connected to the ■ side, the noise temperature To of the multi-channel comparison noise source αυ becomes +
A voltage VQ is generated in the receiver (lcI).

Next, switch all connections of switch B (8) from the ■ side to the ■ side. Dummy load αυ when switch person (7) is on ■ side
When the calibration temperature T1 from 1 is on the side (2), the antenna temperature - is introduced to the receiver, and voltages v1 and V are generated, respectively.

Here, by attaching temperature sensors to the multi-channel comparison noise source α3 and the dummy load αυ, the input temperature 'r(1 and 'r+Th) of each receiver αυ can be known.In addition, TI < TA < To −V
t>V>T.

relationship?) e TO* T1 * vos Vl
and V, the antenna temperature TA can be found from the following equation.

Thus, it is clear that the multi-channel microwave radiometer of this invention has the same performance as the conventional multi-channel microwave radiometer using two calibration noise sources.

〔Effect of the invention〕

As explained above, the multi-channel microwave radiometer of the present invention does not require a standard noise source for each channel compared to conventional multi-channel microwave radiometers, and has a configuration with t fewer switches for each channel. It has become.

Furthermore, since one multi-channel comparison noise source is commonly used for each channel, weight, external dimensions, and power consumption are reduced.

Furthermore, since a radiation-cooled dummy load and a thermal insulator are used, the low-temperature side calibration source can be mounted anywhere on the satellite.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a block diagram of a conventional multi-channel microwave radiometer. In the figure, (1) is the antenna, T2) is the skyhorn, and 13
1Fi duplexer A, +41 is duplexer B, +51 is standard noise source, (6) is comparison noise source, +71, +8
1, (91 is switch A, respectively. B, C, (IIH receiver, (111i Tammy CI -
)', (13ut-multi insulator, αj is a multi-channel comparison noise source, +141 is a duplexer C.

Claims (1)

[Claims] An antenna mounted on a flying object such as an artificial satellite to receive an observation signal, a duplexer that distributes the observation signal from the antenna to multiple channels, a radiation-cooled dummy load used as a low-temperature side calibration source, and the dummy load mentioned above. a thermal insulator that covers the dummy load, a duplexer that distributes the low-temperature calibration signal from the dummy load to multiple channels, a switch that switches between the antenna and the dummy load, and a multi-channel comparison noise source that is used as the high-temperature side calibration source. , a duplexer that distributes the high temperature calibration signal from the multi-channel comparison noise source to a plurality of channels, a switch that switches between the antenna or dummy load and the comparison noise source, and a receiver that amplifies and detects the observation signal. A multi-channel microwave radiometer characterized by: