Optimum Design of Modified Schiffman Multi-Section Wide Band Differential Phase Shifter With Impedance Matching

Abstract

In this paper, a new circuit configuration composed of two main and reference paths is proposed for the modified multisection Schiffman phase shifter, which improves its bandwidth. The method of least squares (MLS) is developed for its design, based on a circuit model including dispersion relations and dissipation effects. The differential phase shift and reflection coefficients from the input ports are obtained by conversions among the impedance, admittance, ABCD and scattering matrices of the circuit model. Then, an error function is constructed, whose minimization is performed by the combination of genetic algorithm and conjugate gradient method, which gives the optimum values of the physical dimensions of the metallic strips. The impedance matching function of the proposed phase shifter circuit makes it a dual action device, leading to some circuit miniaturization. Three phase shifter circuits with single, double and quadruple sections are designed and one prototype model is fabricated and measured. The MLS, full-wave simulation softwares and measurement results agree very well, which validate the proposed circuit configuration and MLS design procedure. The multi-section phase shifters have actually increased the frequency bandwidth.

Electronically Reconfigurable Two-Stage Schiffman Phase Shifter for Ku Band Beam Steering Applications

“…Many modified Schiffman phase shifters were proposed for different purposes, such as bandwidth enhancement, and circuit miniaturization [5]. Many researches suggest many structures such as the double-coupled lines [6,7], cascaded coupled lines, parallel coupled lines [4], and multi-section coupled lines structures [8]. In our proposed design, the original Schiffman phase shifter is amended to develop an accordable phase shifter, having coupled lines charged by varactor diodes without reference line.…”

“…One of the most appealing types of differential phase shifters is the Schiffman structure [4][5][6][7][8] due to its simple topology and wideband characteristic. For this configuration, the differential phase shift is provided by a parallel-coupled microstrip lines section as illustrated in Fig.1(a).…”

Hybrid type of broad-band microwave phase shifter using schiffman lines

“…Many authors have used different techniques to reduce phase error over narrow band. Some of the methods used for designing phase shifter include loaded transmission lines with and without using T shaped stepped impedance open stub [1], [2], [3], two coupled sections together with uniform lines [4] and multi-sections Schiffman lines with impedance matching [5], [6]. Bandwidth of multi-octaves can be achieved by employing multi-sections Schiffinan lines but controlling coupling factors in many coupled lines is difficult.…”

A Modified Coupled-Line Schiffman Phase Shifter With Short Reference Line

“…In order to cancel the influence of the even-odd phase velocity, a novel method is put forward in [13] by choosing the characteristic impedance and electrical length of the linking line between the coupled lines. In addition, there are many methods to improve the bandwidth of the Schiffman phase shifter, such as multi-section cascading connection [14,15], utilizing the unique frequency-independent quadrature property of symmetric couplers [16], and using two 90 • parallel coupled lines [17]. Besides, there are other phase shifter structures, such as a broadband phase shifter which employs loaded λ/4 transmission line [18], single-layer ultra wideband 90 • differential phase shifter whose main line consists of a multi-section radial TL in the middle [19], etc.…”