Backscattering modulators with flexible impedance loading for radiation pattern measurement of small, broadband antennas

A novel, broadband backscattering modulator based on integrated single-pole double through (SPDT) switches is analyzed in this paper. The modulator can be attached to small, single-ended antennas for their radiation pattern measurement based on backscattering methods. A particular bistatic arrangement is considered, with both antenna under test (AUT) and interrogation antenna held in stationary positions, while a receiving antenna turns around AUT. Constant coupling between interrogation antenna and AUT is therefore provided for accurate measurements. A high flexibility for choosing the reflection coefficients for the modulators is obtained for single-ended antennas. Errors from RF or DC feeding cables are reduced through biasing the modulator from a single, low profile, button cell battery. Average change in differential radar cross section of 0.004 dB/day confirms very accurate, long lasting measurement sessions.