The Effect of Impedance Mismatch on Phase Linearity of GCPW Loaded Transmission Lines and Shunt Stubs

Abstract

-This paper presents a study on the effect of impedance mismatch on phase linearity (group delay variations) in grounded coplanar waveguide (GCPW) structures. Two 400 ps GCPW delay lines were designed using a short circuited stub and a transmission line. The structures were simulated over a wide frequency range (0.1 GHz-5 GHz) using both ADS circuit model and CST electromagnetic simulation tool. Based on mathematical analysis and simulation results, impedance mismatch appears to have a large effect on group delay variations in stubs when compared to transmission lines. The simulated time delay of the short circuited stub shows a maximum delay deviation of ±0.75% and ±7.4% for 1.6% and 5.8% impedance mismatch values, respectively. On the other hand, the transmission delay line simulation results show only ±0.1% and ±1.5% for the same impedance mismatch. For the electromagnetic simulation, the presented results indicate even larger variation of time delay for GCPW short stub as it reaches ±3.75% and ±7.5% at 2 GHz and 4.5 GHz for 1.6% impedance mismatch, respectively.

Investigation of Phase Delay Dispersion of the Meander Lines using Hybrid Technique

“…However, at lower frequencies, the dielectric constant changes in a very small range and can not cause such a large increase in phase delay. Initially, it has been suggested that such deviations caused by the specifics of the resonance technique and the periodic nature of the meander line structure, however, similar deviations were found in other works, where other methods of measurement and over slow-wave structure were used [10]- [13].…”

“…4) is calculated using S-matrix technique [15]. The matter of the technique is based on the calculation of final meander DL S-matrix, conversion it to A, B, C, D matrix and finding of phase delay frequency response according to formulas (8)- (10). Final meander DL S-matrix is determining from detailed meander DL S-matrix which is build filling the main and two adjacent diagonals by primitive four elements S-sub matrices.…”