High isolation 4‐port diplexer based on double‐sided parallel‐strip lines

Abstract

A high isolation 4‐port diplexer implemented using double‐sided parallel‐strip lines (DSPSLs) is presented in this letter. Two back‐to‐back 3‐port diplexers and a 180° phase shifter are employed to construct the proposed device. The DSPSL structure enables a compact phase shifter without incurring any extra circuit footprint. The 4‐port circuit topology suppresses the leakage between the 2 channels by signal cancellation, resulting in significantly improved channel isolation. For demonstration, a 4‐port diplexer with operating frequencies of 1.85 and 2.1 GHz is designed, fabricated and measured. The experimental results show that the 4‐port diplexer has good in‐band performance and high isolation of 50 and 51 dB. This is an improvement of over 23 dB compared with the conventional 3‐port diplexer.

Novel planar diplexer using branch‐line coupler

“…Planar diplexers are important component in modern wireless communication systems . The conventional approach to realize a diplexer is to use two filters that are combined with a three‐port impedance matching network .…”

“…Planar diplexers are important component in modern wireless communication systems. 1 The conventional approach to realize a diplexer is to use two filters that are combined with a three-port impedance matching network. 2 Other techniques, such as the common resonator technology, 3 balun diplexer, 4 and others are proposed.…”

“…Required power combination for this method is such that 85% of radiating power lies in TE 11 and 15% lies in TM 11 mode. 1 The TE 11 and TM 11 modes being in phase on the aperture is a condition that sets a limitation on the bandwidth of antenna in terms of cross-polarization performance. The difference in phase velocities of the TE 11 and TM 11 modes is a function of frequency in a way that for a particular waveguide, increasing in frequency decreases the absolute difference between the phase velocities of these 2 modes and vice versa.…”

“…Using corrugated horns is another technique to reduce the cross-polarization level. 1,3 Corrugations change the boundary condition on the wall of the horn and cause the phase velocities of the TE 11 and TM 11 modes to become the…”