The Development Of A Software About Radiation Pattern Transformation In Different Coordinates

Antenna whose quality directly affects the performance of entire system plays an important role on a wireless communication device.And then,antenna measurements which are the most positive way to test the quality of an antenna are getting plenty of attention.Spherical near-field measurement is relatively effective method in near field way which is one of the important means of testing antenna. This paper which is discussed within the context of Spherical near-field test(SNFT) and relying on actual projects presents a computer program so that we can deal with the transformation of radiation pattern between the measurement coordinate(MC) and the antenna coordinate(AC).Detailedly,this program is used for processing the data which are sampled during SNFT and then transformed from near-field to far-field when MC and AC are not uniform.In this paper,begin with the spherical wave expansion, the spherical wave function and antenna scattering matrix are described.And then,the transmission formula which expresses the complex signal received by the probe as a function of probe position and orientation relative to the transmitting antenna is derived.The formula is central for SNFT and will be used to determine the test antenna transmitting coefficients from samples of received probe signal.Considering about the disunity between AC and MC,the paper gives out the transformation formula which obtained by a sequence of mathematical deduce.Finally,a reliable and user-friendly program designed by MATLAB is published.Based on the actual antenna under test for example, using pattern coordinate transformation algorithm that HFSS built-in, the calculation program are verified.At the same time, according to the data offered by the antenna under the condition of spherical near-field measurement, the result and status of the program after calculating has been displayed.