Study Of Near-Field Measurement Based On Modulated Scatterer Technique

In the process of antennas design , it is necessary to measure the far-field character of antennas . Measurements in the very near-field provide a tool to design and check antennas , and also yield information for research . But at the present time the near-field measurement of antennas is too time-consuming to restricting the spread and application of the antennas near-field measurement . Modulated Scatterer Approach is used to overcome the drawback.With using probe array , the way of scan is transformed from mechanically to electrically . The drawback of time-consuming will be overcame , and the efficiency of near-field measurement will be improved . Modulated Scatterer Technique (MST) is the key to realize the method . Every sampling point of the under-test field is corresponded to a element of the array . If the element were connected to a microwave switch , it would produce crosstalk between channels which could be hard to overcome . The solution of the problem is that the probe worked as a scatterer , and a low-frequency signal fed to it . The probe is modulated by the low-frequency signal which is produced by a LF multiplexer . The modulated signal is collected and separated by means of coherent detection techniques . The conclusion that the modulated signal produced by the probe is directly proportional to the under-test electric field can be proved by the scattering matrix and reciprocity formulation.The probe element and the form of array are very important to the measurement system . This paper focuses on the measurement system's element and array in the fourth and the fifth chapters . The system's errors are analyzed in the last.