Reconfigurable Bandstop and Bandpass Filters With Wideband Balun Using IPD Technology for Frequency Agile Applications

A tunable bandstop filter (BSF) with a wideband balun using integrated passive devices (IPDs) technology for multichip module is proposed. The compact tunable BSF uses barium strontium titanate (BST) varactors demonstrating a tuning range of 55% from 1.3 to 2.3 GHz with a 20-dB rejection level. The performance of the filter is optimized by applying asynchronous biases to the BST varactors, leading to bandwidth and rejection level improvement. High-power test results show that the filter exhibits a third-order input intercept point of more than 40 dBm. An IPD wideband balun (0.5-2.5 GHz with ±1 dB amplitude imbalance and 180° ± 20°) using a wideband phase inverter is also presented. The design considerations of the wideband phase inverter (1.5-8 GHz) are addressed in this paper. Design and measured results are also presented for a fixed IPD bandpass filter, and an IPD bandpass filter with a tunable transmission zero to demonstrate the reconfigurability in frequency agile applications.