Design of a novel compact microstrip diplexer with low insertion loss

Abstract

In this article, a microstrip diplexer is implemented based on a novel combination of the coupled lines and spiral structures in order to reduce the circuit size as well as insertion losses. This diplexer with an elliptic function frequency response operates at 2.4/2.79 GHz for wireless applications. Several transmission zeros on the both sides of two passbands are realized, which improve the selectivity. A theory method is presented that helps to miniaturization, control the resonance frequency, improve the insertion loss, and external quality factor simultaneously. The proposed diplexer has a compact size of 0.3λg × 0.25λg with low insertion losses of 0.18/0.39 dB at 2.4/2.79 GHz. The isolation between the two channels (S23) is better than 20.5 dB from DC up to 6 GHz. The designed diplexer is fabricated and measured. There is a good agreement between the simulated and measured results.

Design and Fabrication of a Novel Compact Low-loss Microstrip Diplexer for WCDMA and WiMAX Applications

“…However, it has large insertion loss and small return loss at both channels. Large common port return losses and large implementation areas are achieved in [7], [9] and [14]- [17]. The proposed diplexers in [9] and [14]- [17] have large insertion losses higher than 1.5 dB.…”

“…Based on the above discussion, it is clear that the proposed diplexer is well miniaturized while it has low losses. The external Q factor of the first and second channels Q1 and Q2 are calculated in accordance with the formulas in [7] as follows: The group delay of diplexers usually is more than the group delay in filters, because the design of filters is easier than design of diplexers. Accordingly, many of published diplexers did not pay attention to this issue.…”

A six-channel microstrip diplexer for multi-service wireless communication systems

“…In [14], two quadchannel bandpass filters have been designed based on a novel circular multi-mode resonator. In this paper, a compact six-channel diplexer is introduced, which operates at the resonance frequencies of 0.75/0.85/1/1.25/1.60/1.8 GHz for frequency division duplex (FDD) scheme [15][16] and multi-band wireless applications. It consists of new stub-loaded U-shape resonators, which are integrated by the coupled lines.…”

Compact unequal filtering power divider operating in two bands with controllable characteristic impedances

“…According to Equations (2.8), (2.10), and (2.11), the input impedance viewed from ports 1 to 2 can be obtained. 10 When impedance matching is reached well for all ports, the power splitting ratio can be calculated as:…”