Wideband arbitrary phase‐difference coupled‐line coupler with tight coupling coefficient and small phase variation

Abstract

In this study, a planar arbitrary phase‐difference coupled‐line coupler having wide bandwidth, tight coupling coefficient, and small phase variation are proposed. The proposed coupler consists of two quarter‐wavelength coupled‐line sections connected with two different transmission lines. Moreover, the interconnection transmission line can be designed as a small phase variation phase shifter with the introduction of a shorted stub. The detailed theoretical analysis is provided to illustrate the design concept. The circuit parameters of this novel arbitrary phase‐difference coupler can be easily determined by the derived closed‐form equations. For verification, two 3 dB couplers with 45°/135° and 60°/120° phase differences are fabricated and measured. The 45°/135° coupler achieves 34.2% fractional bandwidth for 45° phase difference with 2° phase variation and 36.3% fractional bandwidth for 135° phase difference with 3.4° phase variation. Moreover, the 60°/120° coupler achieves 30% fractional bandwidth for 60° phase difference with 0.9° phase variation and 32.9% fractional bandwidth for 120° phase difference with 1.5° phase variation.

Multi‐section broadband couplers with arbitrary phase differences and power‐dividing ratios

“…6 Thereafter, the co-designed couplers were developed towards arbitrary power-dividing ratio outputs, [7][8][9] compact size, 10,11 dual-band 12 and broadband operation. [13][14][15][16][17][18] The couplers with arbitrary phase differences include patch couplers, 8 coupled-line couplers, 13,14 and branch-line couplers. [15][16][17][18] By using tight-coupling coupled lines, the bandwidth of coupled-line couplers 13,14 can be extended at the cost of interspersed input/output ports.…”

“…[13][14][15][16][17][18] The couplers with arbitrary phase differences include patch couplers, 8 coupled-line couplers, 13,14 and branch-line couplers. [15][16][17][18] By using tight-coupling coupled lines, the bandwidth of coupled-line couplers 13,14 can be extended at the cost of interspersed input/output ports. Comparing with coupled-line couplers, the output ports of branch-line couplers are located at the same side, which will benefit the practical circuit layout.…”

Coupled‐line rat‐racecouplers with smoothin‐phaseandout‐of‐phaseperformances

“…In 2018, Gao et al presented a method to enhance the phase performance by implementing a shorted stub. 13 A new coupled-line structure has been proposed to achieve tight coupling. 14 In this paper, a novel structure of rat-race coupler based on coupled-lines is proposed.…”

Design of wideband directional coupler based on secondary stage coupled structure

“…In previous designs, directional coupler was designed using multilayer structures, [3][4][5][6] which provide tight broadside coupling across wideband. Furthermore, parallel coupledline couplers [7][8][9][10][11][12][13] are widely utilized in many wireless and microwave applications. Although it has the characteristics of wideband and strong coupling, the coupler is difficult to achieve the desired performance.…”