Scattering-Matrix-Based Parametric Characterization of a Two-Port Bridged-T Network for Microstrip Filter Applications
Provides a parametric characterization of a Bridged-T network for microstrip filter design, but the results are incremental and simulation-based without experimental validation.
This study characterizes a two-port Bridged-T network using scattering matrices and derives parametric expressions for S11 and S21. The network is designed as a high-pass filter with a corner frequency of 1 GHz, achieving sharp roll-off ratios of -30 dB/GHz for S11 and -32 dB/GHz for S21 in simulations.
The purpose of this study is to characterize a two-port Bridged-T network using transmission (T) and scattering (S) matrices. Using mathematical derivations, scattering parameters including S11, S12, S21, and S22 have been derived from the T and S matrices to permit a detailed investigation of the network's performance. As two of the most relevant parameters in the design of microstrip filters, both the magnitude and phase of S11 and S21 have been parametrically calculated after normalizing the frequency. Furthermore, when the inductors L1 and L2 are identical, all even coefficients of the numerator polynomial in the S11 transfer function are eliminated, leaving only the odd coefficients behind. Based on this feature, the bridged-T circuit is designed to operate as a high-pass filter. Therefore, the magnitude and phase of both S11 and S21 have been simulated for the designed filter with a corner frequency of 1 GHz. Simulation results performed by Keysight ADS show that S11 and S21 for the high-pass filter built upon the bridged-T network have sharp roll-off ratios of -30dB/GHz and -32dB/GHz respectively.