JPS6049855B2 - microwave radiometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to improvements in microwave radiometers.

2. Description of the Related Art Conventionally, there is a microwave radiometer as shown in FIG. 1, which receives microwave noise radio waves emitted from an object and observes the brightness temperature of the object.

In FIG. 1, 1 is an antenna, 2 is a low noise receiver, and 3 is an integrator. Microwave noise radio waves radiated from an object are received by an antenna 1.

This received radio wave is amplified and detected by the low-noise receiver 2, and then integrated by the integrator 3 to become the final output signal. It represents the average brightness temperature of the object. In this case, the temperature resolution ΔT representing the minimum reception sensitivity of this microwave radiometer is given by the following equation. In the first equation, TA is a constant determined by the configuration of the low noise receiver 2, and TA is the antenna 1.
The antenna temperature of the microwave noise radio wave received at TR
is the receiver noise temperature of the low-noise receiver 2, and B is the bandwidth of the low-noise receiver 2.

T is the integration time of the integrator 3.

As is clear from the first equation, the temperature resolution ΔT of this microwave radiometer can be reduced by increasing the integration time. However, when using this type of microwave radiometer onboard a satellite, for example, the integration time must be large, as shown in Figure 2. The footprint becomes larger, and a larger footprint means that the distance resolution of this microwave radiometer deteriorates. Therefore, this conventional microwave radiometer has the disadvantage that when trying to increase the temperature resolution, the distance resolution deteriorates, and when trying to increase the distance resolution, the distance resolution deteriorates. Therefore, in the present invention, by providing a plurality of low-noise receivers, the above-mentioned drawbacks of the conventional method are eliminated.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 3, 1a to 1n are antennas, 2a to 2n are low noise receivers, 3a to 3n are integrators, and 4 is a signal processor. Microwave noise radio waves radiated from an object are received by a total of N antennas from antennas 1a to 1n.

The radio waves received by each antenna are amplified and detected by low noise receivers 2a to 2n connected to each antenna, and then integrated by integrators 3a to 3n. These integrated signals are combined within the signal processor 3 and become the final output signal. It is assumed that the antennas 1a to 1n and the low noise receivers 2a to 2n have the same performance, and the minutes of each integrator 3a to 3n are the same and τ is the temperature resolution ΔT of the microwave radiometer in this case. can be expressed as: In equation (2), N represents the number of low-noise receivers, etc., and the meanings of the other symbols are the same as in equation (1).

Therefore, for example, if the microwave radiometer of the present invention is mounted on an artificial satellite and the directions of the antennas are adjusted so that the beams of each antenna illuminate the same point, the conventional microwave radiation Since the integration time of each integrator can be reduced to 1/N compared to the total time, the footprint on the earth's surface becomes smaller as shown in Figure 4.
As a result, high distance resolution can be obtained.

Further, even though the integration time of each integrator is short, by composing them, the apparent integration time can be lengthened, so that high temperature resolution can be obtained. As described above, the microwave radiometer of the present invention has the advantage that high distance resolution can be obtained without deteriorating temperature resolution.

[Brief explanation of drawings]

1 and 2 are diagrams for explaining a conventional microwave radiometer, and FIGS. 3 and 4 are diagrams for explaining a microwave radiometer of the present invention. 3 is an integrator, and 4 is a signal processor. Note that the same or corresponding parts in the figures are indicated by the same reference numerals.

Claims (1)

[Claims] 1 Frequency band and polarization used for the purpose of improving the temperature resolution and distance resolution of a microwave radiometer in a microwave radiometer that receives microwave noise radio waves emitted from an object and observes the brightness temperature of the object. A microwave radiometer characterized by having a plurality of low-noise receivers with the same noise.