Study On Fast Measurement Of Antenna

In the near-field antenna measurement, the time required by the single probe mechanical scanning becomes prohibitively long. The near-field measurement system based on the modulation scattering technique can improve precision of measurement. In this paper, development of near-field antenna measurement and basic theory of modulated scatter near-field measurement are introduced. After researching on how to fast measure antenna, a method of fast measurement antenna is proposed. The fast measurement antenna system use probe array to mechanical scan, signals received by probes are modulated by microwave circuits, and modulated signals are sent to receiver.Dual-polarized printed dipole as the element of probe array. Printed dipole has the merits of simple structure and easy production. Dipole is used as received antenna in the measurement system, so it should have ultra wide band. This paper introduces the broadband technology of microstrip antenna and analyzes the single-polarized printed dipole. On this basis, a dual-polarization printed dipole is designed. Probe array is a linear array, which elements are four dual-polarized printed dipoles. The distance of dipole is optimized in order to reduce the impact of mutual coupling between elements.Probe array can receive many signals from each element. Microwave signals are modulated and sent to network analyzer in sequence. Modulated circuits use microwave switch chip, and TTL imported as modulation signal. Because many channel signals are imported to receiver, a one-eight Wilkinson power divider was used to connect circuits and analyzer. The power divider use microstrip line structure and impedance transformation line uses the form of arc. The form of arc can reduce the input VSWR, broaden the working band and decrease the impact of mutual coupling.