Broadband and Highly Accurate X-Band Vector-Sum Phase Shifter Using LC-Type Power Splitter

In recent years, for the realization of the low-cost and multi-band AP AA (Active Phased Array Antenna) system, broadband and highly accurate vector-sum phase shifter has attracted the attention. To realize such a vector-sum phase shifter, one of the difficulty arises from the trade-off between a bandwidth and an insertion loss of the PPF (Poly Phase Filter) which is deployed at the first stage inside the phase shifter and generates quadrature signals from a differential signal. In order to ease the trade-off of PPF, we propose the PPF using inductor and capacitor (LC-type) power splitter implemented in front of it. Simulation results with the proposed technique show the improvement of 2.7dB in the insertion loss, without degradation of the bandwidth. As a proof of concept, vector-sum phase shifter with the proposed PPF technique was fabricated using 0.18um SiGe BiCMOS process. Measurement results showed the 3dB gain bandwidth of 64% at X-band and the RMS phase error of less than 2.1°. This broadband and highly accurate results show that the proposed PPF technique is effective to realize multi-band AP AA system in the near future.