JPH0543260B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention measures the brightness temperature of the earth's surface and its vicinity, processes the data, and transmits it to a ground station in order to observe physical phenomena on and near the earth's surface. This relates to microwave radiometers mounted on spacecraft, etc.

[Conventional technology and its problems]

Conventionally, in order to improve the spatial separation ability of this type of microwave radiometer, the configuration of the antenna section must be such that the half-width of the radiation beam can be narrowed. It uses a reflective mirror. Such conventional microwave radiometers scan a mechanical reflector to receive microwave (sometimes millimeter wave) band noise of a specific width (scanning width or observation width: Swafh) on the Earth's surface, and then detect this noise. The power value is measured by a single receiver system that connects the antenna to the power feeding section. An example of its configuration is shown in FIG.

This conventional microwave radiometer has the following drawbacks.

(1) Since the mechanical reflector scans vertically and horizontally, a disturbance torque is generated on the spacecraft that mechanically interfaces with this radiometer, which deteriorates the attitude control system of the spacecraft.

(2) This reduces the observation accuracy and spatial resolution of other observation instruments, especially optical sensors.

(3) Also, for the same reason, scanning cannot be constrained, so the instantaneous field of view of the antenna beam on the earth's surface cannot be narrowed.

(4) Furthermore, for the same reason, scanning cannot be done in stages, so the instantaneous field of view moves only during the predetermined integration time when noise is detected, so the spatial resolution is limited to the beam half-value angle. It is considerably lower than .

One way to alleviate these drawbacks is to change the configuration of the antenna from a mechanical scanning type to an electronic scanning type. That is, this is a method in which the amplitude and phase of the signals fed to each element of the array antenna are controlled and the antenna radiation beam is scanned by an electronic circuit. However, with this method, the efficiency of the array antenna is often inferior to that of a mechanical antenna, which is an obstacle to improving the temperature resolution (sensitivity) of the microwave radiometer.

[Means for solving problems]

In order to solve these drawbacks, the microwave radiometer of the present invention uses an array antenna with multiple beams, and connects an independent receiver to each feed point of the antenna to improve sensitivity. be.

[Effect]

One way to improve the performance of temperature resolution is to lengthen the integration time in the integrator of the detection output. If the composite beams of the array are multiplied and multiple receivers are connected in parallel, the number of steps in one sweep will be reduced to 1/n ₂ (n ₂ : number of receiver systems).
Therefore, the integration time becomes n ₂ times. Therefore, by adopting the multi-beam method, it is possible to improve the performance of temperature resolution.

〔Example〕

Next, the present invention will be explained with reference to the drawings. FIG. 1 is a comprehensive functional system diagram of an embodiment of the present invention.

Array antenna 1 is array antenna feeding circuit 2
The feeder circuit 2 forms a multi-beam, and outputs n ₂ systems (n ₂ = 4 in FIG. 1) of received microwave noise outputs from among the outputs. These output noises are supplied to the receiver (RF/frequency conversion sections 13-16, IF/detection sections 17-20) via switches 3-6. Note that the local oscillator circuit can be shared in each receiver. The detection output of the receiver is connected to a data processing system 21. Switches 3 to 6 switch between the output noise of the power supply circuit 2 and the noise correction line. The noise source for soft correction is composed of a skyhorn 10, a comparison noise source 11, and a standard noise source 12. These are distributed/switched by the hybrid 9 and switches 7 and 8.

The radiometer configured as shown in Figure 1 has a multi-beam antenna, which allows effective use of the antenna aperture, and allows multiple receivers to be connected in parallel, so the observation temperature resolution of the microwave radiometer ( The integration time after detection of the received microwave noise power, which determines the sensitivity (sensitivity), can be made n ₂ times (4 times in the embodiment) longer than when configured with only one receiver. Therefore, using the sensitivity calculation formula below, it is possible to achieve a sensitivity improvement of _√2 times.

△T(K)=k(T _R +T _A )/√τ・B where △T: Sensitivity k: Value determined by reception method T _R : Receiver noise temperature T _A : Antenna noise temperature τ: Integration time B: Receiver Noise Bandwidth To convert the array into a multi-beam array and perform detection and integration in parallel using multiple receivers, there is a method of using a BFN (Beam Forming Network) circuit as part of the feeder circuit 2. There are four examples.

1. As shown in Fig. 3, a system in which a lens or Butler matrix is used to form a number of composite beams equal to the number of scanning steps, and these are switched to each receiver using a switch matrix.

2. As shown in FIG. 4, a number of composite beams equal to the number of receiver systems are formed using lenses or a Butler matrix, and these are connected to each receiver. Further, each combined beam scans the scanning range in a stepwise manner by a phase shifter.

3 As shown in Fig. 5 and the details of the BFN in Fig. 5 in Fig. 6, the output of each antenna element is divided into n ₂ ,
A scanning method in which a phase shifter is provided individually for each receiver system.

4 As shown in Fig. 5 and the details of the BFN in Fig. 5, the antenna element is divided into the number of receiver systems, and each network circuit forms a composite multi-beam to each receiver. Connection method.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain a microwave radiometer that can effectively utilize the aperture of the antenna and has improved observation temperature resolution (sensitivity).

[Brief explanation of the drawing]

Fig. 1 is a comprehensive functional system diagram of the present invention, Fig. 2 is a comprehensive functional system diagram of a conventional microwave radiometer, and Fig. 3 is a comprehensive functional system diagram of the conventional microwave radiometer.
4 and 5 are block diagrams of the array antenna feeding circuit of the present invention, and FIGS.
FIG. 2 is a block diagram showing internal details of the BFN circuit shown in the figure. DESCRIPTION OF SYMBOLS 1...Array antenna element, 2...Array antenna feeding circuit, 3-8...Switching switch, 9...
...Mixer, 10...Skyhorn antenna, 11
... Comparison noise source, 12 ... Standard noise source, 13-1
6...RF/frequency conversion section, 17-20...IF/
Detection section, 21... Data processing system, 22... Parabolic antenna, 23... Antenna drive mechanism section, 24
...Low noise amplifier, 25...Fixed phase shifter, 26...
...BFN circuit, 27...Switch matrix, 2
8... variable phase shifter, 29... distributor, 30... network circuit.

Claims (1)

[Claims] 1. An electronic scanning array antenna with directivity, a beam forming circuit that converts the antenna beam of the array antenna into a multi-beam, and noise in a signal that is selectively coupled and input to the array antenna via the beam forming circuit. A high-precision microwave radiometer including a plurality of noise temperature detection receivers that detect temperatures, and a signal processing circuit that processes the outputs of the receivers and scans and controls the array antenna.