An Implementation of Compact Quarter-Wave-Like- Transformers Using Multi-section Transmission Lines

Abstract

This paper proposes a novel miniaturization technique of quarter-wave transformers (QWTs), implemented using multi-section transmission lines (MSTLs), based on the quarter-wave-like transformer (QWLT) theory. Multi-section QWLT characteristics are derived analytically and solved via appropriate optimization algorithms for associated transmission-line parameters. For an illustration purpose, two-and three-section QWLT prototypes with 50% physical size reduction from the corresponding QWT size operating at 2.4 GHz are fabricated using microstrips and tested. It is found that these prototypes yield acceptable return loss at 2.4 GHz without significant bandwidth reduction, comparing to the QWT result.

Design of Reactance-to-Reactance Impedance Transformers Based on Conjugately Characteristic-Impedance Transmission Lines (CCITLs) and Meta-Smith Charts (MSCs)

“…Moreover, the RRTs using CCITLs will be implemented using microstrips to verify the proposed technique. In order to implement these, Z c  in ( 8) can be written in terms of the ABCD parameters as [15][16][17] ± c 2 2 j 4 ( )…”

“…where the ABCD parameters in ( 16) are associated with the implemented RRT circuit using CCITLs. In addition, θ c in ( 14) can be written in terms of the ABCD parameters as [15][16][17] c cos . 2…”

“…Note that ( 16) and ( 17) are the main equations to design associated RRT circuit parameters to obtain the desired CCITL parameters (Z c  and θ c ). For example, multisection TLs can be applied to implement CCITLs as discussed in details in [15]. In the next section, results of some case studies and the RRT prototype implemented using CCITLs are presented with discussions.…”

“…This paper proposes the novel method to reduce size of reactance-to-reactance transformers (RRTs) by using conjugately characteristic-impedance transmission lines (CCITLs). Note that CCITLs have been first proposed in 2004 [10] and widely applied later [11][12][13][14][15][16][17]. CCITLs are lossless transmission lines (TLs) with conjugate characteristic impedances for forward (Z c + ) and backward (Z c -) propagation directions.…”

“…CCITLs are lossless transmission lines (TLs) with conjugate characteristic impedances for forward (Z c + ) and backward (Z c -) propagation directions. Interestingly, CCITLs can be applied to miniaturize microwave components [14][15][16]. To intuitively and effectively design CCITLs, Meta-Smith charts (MSCs) can be applied [17].…”