Cheng Chunyue

Mutual coupling calibration algorithm of array antennas and its error estimation

Based on subspace principle and matrix perturbation theory, this paper presents a new mutual coupling calibration algorithm for uniform antenna array when azimuth of calibration source is in the presence of errors. By using one calibration signal source, the new approach can present the approximate estimation of mutual coupling matrix that has least error upper limit in the meaning of statistical average when the azimuth of the calibration source is inaccurate. Computer simulations are presented. The simulations show the validity of the new calibration algorithm.

Design and emissivity meterage of 3mm microwave blackbody

The configuration design and the meterage data of 3 mm microwave blackbody are presented. The blackbody can be used in 75 GHz to 110 GHz or higher frequency and its emissivity is more than 0.996. Because the emissivity of microwave blackbody is close to one, namely its reflectance almost equals zero, the directivity error of directional coupler and the antenna reflection will make it is difficult to measure the emissivity directly. Hence, we use the space reflection method of moving DUT to measure reflectance of microwave blackbody. In this method, the reflectance of measurement system is equivalent to a big stationary wave and the reflectance of black body is equivalent to a small stationary wave. By using moving blackbody, we can separate the two stationary waves. The emissivity of blackbody is given by friis formula including some near field parameters. The measurement results are presented in section 5.

Experimental study on emissivity measurement of 5mm blackbody

The emissivity measurement of 5 mm microwave black is presented. Because the emissivity of microwave blackbody is close to one, namely its reflectance almost equals zero, the directivity error of directional coupler will cause that is difficult to estimate the emissivity. Hence, we use the space reflection method of moving DUT to measure reflectance of microwave blackbody. In this method, the reflectance of measurement system is equivalent to a big standing wave and the reflectance of block body is equivalent to a small standing wave. By using moving block body within half wavelength, we can separate the two stationary waves. The emissivity of black body is given by Friis formula and some calibration parameters including phase center, gain calibration value, effective area of antenna. The measurement results are presented

Research on the Microwave Radiometer Signal Waveform Simulation

Microwave radiometer is a passive remote sensing instrument, which is used to measure thermal electromagnetic emission from material media. It has been widely used in atmosphere detection, ocean observation, earth observation and other domains. Computer simulation plays an important role in system analysis, design, research and performance testing. This paper firstly presents the radiometers framework and simulates the waveform from the antennas input noise signal to integrators output signal (before A/D convector), Then simulates the linearity of the whole model. The simulation result indicates that the linearity of the radiometer is very well, finally gives the calibration equation of the radiometer.

The computing model of radiation pattern for imperfect radome

In this paper a computed model for the radiation pattern of an imperfect radome is given. Based on the model a formula is derived and the computed results are given to explain the effects of an imperfection of the radome on the radiation pattern.

Microwave payload's Emissivity with an S-band conical corrugated lens antenna

According to the calibration desire of the radiometer space-borne microwave payload, an S band conical corrugated antenna is studied. An actual antenna was manufactured after analysis and simulation. Performance of the antenna is measured in the radio anechoic chamber of Aerospace EMC center. Especially, the Emissivity of the applied microwave blackbody source is discussed and measured with this corrugated horn. The consistency between the measurement data and the design outcome is very well.

An S-band conical corrugated lens antenna and Emissivity measurement

According to the calibration of radiometer spaceborne microwave payload desire, an S band conical corrugated antenna is studied. An actual antenna was manufactured after analysis and simulation. Performance of the antenna is measured in the radio anechoic chamber of Aerospace EMC center. Especially, the relationship between Emissivity and the brightness temperature of the applied microwave blackbody source is discussed and Emissivity measured. The consistency between the measurement data and the design outcome is very well.

Union Estimation Algorithm for DOA of CM Signal and Gain and Phase Errors of Array Antennas

A union estimation algorithm for direction of arrival (DOA) of constant module (CM) signal and gain-phase values of array antennas is presented. At first, the improved ILSP (iterative least squares projective) algorithm is presented to estimation the DOA of signals. Then a cost function based on nonlinear constraint is given to solute the gain and phase errors. By repeating iterative procedures above mentioned, new algorithm can give the DOAs estimation of CM signals and gain and phase coefficients of array antennas. The new algorithm does not need the assistant calibration sources that directions are known and may estimate direction of actual source online. Simulations show the validity of the new algorithm.

A calibration algorithm for gain and phase errors of array sensors based on a single nonlinear constraint

A new calibration algorithm needing one calibration source is presented to estimate the gains and phases of uniform circular array. Firstly, the data collection is done by laying assistant source in different direction. Then the cost function is present by using the signal subspace vector and noise subspace vector of data covariance matrix. Under the nonlinear constraint, the union estimation of DOA of assistant source and the gains and phases of uniform circular array are given by iterative operation. The algorithm does not need to know the direction of assistant source. Simulations show validity of the algorithm.

The analysis of radiation diagram and transmission efficiency for imperfect radome

In this paper, a study of the radiation diagram and transmission efficiency for an imperfect radome is presented. Based on the ray tracing method, the results of computer simulation show the changes of radiation diagrams and transmission efficiency caused by outside damage for two types of radomes.