A Novel Compact Dual-Frequency Coupled-Line Transformer With Simple Analytical Design Equations for Frequency-Dependent Complex Load Impedance

Abstract

Abstract-In order to perfectly match arbitrary frequency-dependent complex load impedances at two uncorrelated frequencies, a novel coupled-line impedance transformer without transmission-line stubs is proposed in this paper. This transformer mainly features small size, wide bandwidth, simple analytical design method, and easy planar implementation. The transformer simply consists of a coupledline section and an additional transmission-line section. Due to the usage of a coupled-line section, the theoretical synthesis of the proposed transformer becomes very simple when compared with previous transformers and the total size of the planar circuit without deterioration of operating bandwidth becomes small. Furthermore, several numerical examples are presented to demonstrate the flexible dual-frequency matching performance. Finally, the profile of matching frequency-dependent complex load impedance at two arbitrary frequencies has been examined by simulation and measurement of two microstrip generalized T -junction power dividers. Good agreement between the calculated results and measured ones justifies this proposed transformer and the design theory.

An analytical design method for a novel dual‐band filtering DC‐block impedance transformer

“…[7][8][9][10][11][12] Accordingly, dual-band impedance transformers have been presented in Refs. [13][14][15][16][17][18][19][20][21]. In 2003, an extension of the two-section transformer was proposed in Ref.…”

“…Furthermore, using coupled lines, arbitrary dual-band transformers for matching arbitrary frequency-dependent complex load impedances are developed in Refs. [16][17][18][19]. Due to the coupling structure, DC-block function is also achieved inherently in Ref.…”

A Tri-Band Impedance Transformer Using Stubbed Coupling Line

“…Furthermore, it can be seen that Z 0 should be larger than Z L in solution Equation (12) and smaller than Z L in solution Equation (27), which means different structures for different cases.…”

“…However, it can only design to match purely imaginary loads. In recent years, researchers further focus on the areas of increasing the operating bandwidth and matching a complex impedance load [26][27][28][29].…”

A T-Section Dual-Band Matching Network for Frequency-Dependent Complex Loads Incorporating Coupled Line With Dc-Block Property Suitable for Dual-Band Transistor Amplifiers

“…Usually lumped component based matching networks [22] are simpler, but fabrication of lumped component is difficult at higher frequencies and maintaining their value over a wide frequency range is extremely difficult [23]. Furthermore, few coupled line based dual-band impedance transformers exhibiting good performance have been reported and in general they may or may not provide inherently DC blocking [24][25][26].…”