Purpose
This paper aims to describe a new microwave radiometer designed for sensing natural mediums to solve various applied scientific problems. The research findings enable to make assertions about high efficiency of the described microwave radiometer being a part of mobile sensor systems with self-contained power supplies.
Design/methodology/approach
A new microwave radiometer is based on the modification of the null method. Modification of the null method has been implemented by using two reference noise generators. The first reference noise generator is passive and its implementation is based on the matched load. A low-noise amplifier is used as the second reference noise generator. The use of the low-noise amplifier as the reference noise generator is based on the noise wave generation effect at its input whereby the waves form low-temperature noise.
Findings
The use of the low-noise amplifier as the reference noise generator in the modified microwave radiometer has made it possible to simplify the device design at the system level while reducing the weight and power consumption and increasing sensitivity.
Originality/value
The novelty of the modified radiometer lies in the modification of the null method and the removal of high-temperature reference noise generators based on avalanche transit-time diodes. Further, the novelty lies in the invariance of measurement results toward changes in the receiver’s own noise and transmission factor while the design of the device has been simplified.
This paper describes an achieved result in designing of the four-receiver microwave hyperspectrometer based on zero measurement method and the multi-receiver concept of realization. The block diagrams of the microwave front-end with operating frequency band from 18 to 26.5 GHz, the radiometric receiver, and the frequency transmission module are shown. The technical implementation of every described blocks of the microwave hyperspectrometer are described. Presented technical implementation includes a list of modern components are used to designing of laboratory model of hyperspectrometer. The detailed block diagram of the microwave front-end is presented. Description of main technical characteristics of parts of the microwave front-end is also presented. The analysis of a technical characteristics influence to measurement errors is shown. The mathematical model of a measurement error calculation in hyperspectral modeis described. The influence of the active reference noise generator temperature accuracy, the directional coupler insertion loss and the passive reference noise generator temperature accuracy to a measurement errors are described. A numerical experimental results of designed mathematical model are presented. The dependence of the minimum value of measurement errors form the temperature of passive noise generator is presented.
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