JPH01302178A - Microwave radiation meter - Google Patents

Abstract

PURPOSE:To improve temperature resolutions, by dividing a primary radiator array of a switching antenna of a microwave radiation meter into parts which are provided with receiving sections to secure a fixed distance resolutions. CONSTITUTION:An array 2 composed of a plurality of primary radiators are divided into several sets, each of which is provided with an RF circuit section 4, a receiving section 5 and a calibration source. For example, when the primary radiator array 2 is equally divided into (n) sets, ground speed and others are made the same as those before the division. Thus, a scanning range by one set of array attains 1/n of the original scanning range. As a result, the time requiring the integration of the same beam spot with a receiver increases (n) times thereby allowing temperature resolutions T to be improved by n<-1/2> times.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a microwave radiometer mounted on, for example, an artificial satellite.

[Conventional technology]

Fig. 2 is a diagram showing the configuration of a conventional microwave radiometer. In Fig. 2, (1) is a reflecting mirror, f41FiR? The circuit section, (5) is a receiving section, (6) is a signal processing section, (7) is a horn antenna called a skyhorn, (8) is a standard noise source, and an f91a primary radiator.

Next, the operation buttons will be explained. The input noise radio wave received by the primary radiator (9) via the reflector fil is passed through the RF circuit section (4), then amplified and 2-frequency V-converted and detected at the receiving section (5) before being input. Nine voltages VM are obtained corresponding to the noise temperature TM of the noise radio waves. This relationship can be expressed as Formula (1)% Formula% (
1) Here: Proportionality constant B: Band G: Receiver gain Cd: Detection sensitivity TM Two-person force In equation (1), the measured noise temperature - the noise radio wave at the known noise temperature By calibrating the voltage vM by giving Therefore, for normal calibration, two-point calibration is performed by switching the skyhorn (7) whose noise temperature is known and the standard noise source (8) using a room temperature dummy at the R7 circuit section (4). . Then, the obtained observation and calibration voltages are A/D converted by a signal processing section (6) and transmitted to the ground.

By the way, in an actual radiometer, it is necessary to scan the ground, so as one scanning method, as shown in Figure 3, multiple elements (8 elements in the figure) with different beam directions are placed opposite 2 reflecting mirrors + 11. ) by arranging the array 01 of primary radiators and connecting the switch (3) to each primary radiator.
A switching antenna may be used that scans the ground by changing the beam direction by switching the primary radiator connected to the circuit section (4).

Generally, the temperature resolution ΔT of a microwave radiometer is
) is expressed by the formula.

TA 10TR (2) ΔT=x ・□ − “7” − Here, TA two-person noise temperature TR: Radiometer total noise temperature including the antenna feed system B: Frequency band τ: Integration by the integrator inside the receiver Time
) In the equation, TR has constraints such as the noise figure of the semiconductor element used in the receiver, and B has constraints on the guard band determined by the frequency used.

Therefore, in order to improve the turbidity resolution, it is necessary to lengthen the integration time T.

However, in a microwave radiometer mounted on an artificial satellite, the ground speed vg remains constant depending on the orbit conditions, so the fourth
As shown in the figure, the footprint of the antenna beam on the ground (length in the scanning direction Xti3X length in the traveling direction y
a2) If Δya4 overlaps K in the traveling direction, it is expressed by a general equation in which the scanning period τ is constant when the scanning range tan is constant.

Length: Distance between beam centers in the traveling direction αe y: Length of the beam spot in the traveling direction α2 Δy: Weight of the beam spot in the traveling direction O is expressed by the formula (4) where B: Distance between beam centers in the scanning direction αη = scanning range an T: scanning period Here, since the scanning range ta11 and the scanning period T are constant, the integration time τ is made long (then the distance between the beam centers in the scanning direction B(lη is long) (11 Eventually, the beam Spot underlapping occurs and the distance resolution of the radiation needle deteriorates.

For this reason, there is a problem that m-variance resolution and distance resolution conflict with each other.
One thought.

This invention was made to solve the above-mentioned problems, and the purpose is to obtain a microwave radiometer that can improve the temperature resolution (integration time) while keeping the distance resolution (scanning direction beam center distance BQη constant). shall be.

[Means to solve the problem]

In the microwave radiometer according to this invention, an array consisting of a plurality of primary radiators is divided into several sets.

Each set is provided with an R7 circuit section (4), a receiving section (51), and a calibration source.

[Effect]

In the microwave radiometer of the present invention, for example, the primary radiator array (2) is equally divided into n groups.

Ground speed and other conditions shall be the same as before division. The scanning range scanned by one set of arrays is > of the original scanning range. As a result, the time for the receiver to integrate the same beam spot is increased by n times, and the m-variable resolution ΔT is improved by 1/β times.

〔Example〕

An embodiment of the present invention will be explained below with reference to the drawings. Here, as an example, in the switching antenna type radiometer shown in Fig. 3, the primary radiator array 0I (8 elements) is divided into two equal parts of 4 elements each. The object is shown in Figure 1.

In Figure 1, (1) is a reflector, (2) is a divided primary radiator array, (3) is a changeover switch, (4) is an RF circuit section, (5) is a receiver section, (6) is a is the signal processing section, (
7) is a skyhorn, and (8) is a standard noise source.

Other satellite ground speed vg antenna beam width.

The conditions for the scanning range 1, etc. are the same for both the radiometer according to the present invention and the conventional radiometer. At this time, in the microwave radiometer of this invention, the primary radiator array (8 elements) is divided into two, each with 4 elements, so the beam spot on the ground corresponding to each array is 4 on the right in Figure 4. 1 and left 4
divided into.

Because the satellite ground speed Vg and beam width are one foot.

When using this radiometer, the scanning period is the same as the conventional one. On the other hand, the scanning range is / of the conventional scanning range lαυ for one divided primary radiator array. In the configuration of the radiation needle of this invention, one receiving section (integrator) 5) is connected to each divided primary radiator array, so each receiving section (
The integration time τ' of the integrator (5) is expressed by the following equation.

1/2 From this, the integration time for one beam spot in the case of nine divisions is twice that of the conventional one. As a result, by using this invention, the temperature resolution ΔT′ ￥ith equation (2) 1 equation %
is improved by 1/f'2 compared to conventional radiometers.

Although this example shows the case of dividing into two equal parts, if the array is divided into n equal parts and n systems of receivers (integrators) are used, the temperature resolution is 1/F/''n times that of the conventional one. only improved.

Furthermore, even if the array is not divided equally but divided at an appropriate ratio, a corresponding improvement in temperature resolution can be obtained overall.

Furthermore, even if the antenna is a switching antenna (if the scanning range can be divided with a similar configuration, the same improvement effect can be obtained by connecting a receiving section (PR divider) to each of the divided antennas.

〔Effect of the invention〕

As described above, according to the present invention, the primary radiator array of the switching antenna of the microwave radiometer is divided, and a receiving section (integrator) is provided in each of them to ensure a certain distance resolution. This has the effect of improving temperature resolution.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a microwave radiometer according to a first embodiment of the present invention, Fig. 2 is a block diagram of a conventional microwave radiometer, and Fig. 3 is a block diagram of a switching antenna type microwave radiometer. . FIG. 4 is an explanatory diagram of the footprint of the microwave radiometer on the ground. In the figure, (1) is a reflector, (2) is a divided primary radiator array, +31Fi changeover switch, (4) is an RF circuit section, (5) is a receiver, f6 is a signal processing section, (7) ) is Skyhorn. +81 #'ii quasi-noise source, (9+H primary radiation B, 0
1 is the primary radiator array, αυ is the scanning range t, a'aFi
The length of the beam spot in the scanning direction is y, ai is the length of the beam spot in the scanning direction The distance A between the spot centers and Qη indicate the distance B between the boom spot centers in the scanning direction. In the drawings, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] a reflector, a plurality of primary radiator arrays installed opposite to the reflector, a switch connected to the primary radiator for switching the primary radiators to perform antenna beam scanning, and an output of the switch. An RF circuit section connected to the end, a receiving section that obtains a voltage value corresponding to the noise temperature of the noise radio waves acquired via the RF circuit section, and A/D conversion and data processing of the output voltage of the receiving section. The microwave radiometer is characterized in that the primary radiator array and the switch are divided into several sets, and each set is provided with the RF circuit section and the receiving section. Microwave radiometer.