Wideband 0-dB branch-line directional couplers

Abstract

Enlarging the operating frequency band of 0-dB directional couplers by using branch-line structures of a special type is discussed. Analysis of the basic configuration by the even-odd mode decomposition technique is performed. An experimental verification is presented. INTRODUCTIONRealization of crossovers is a particular problem in the design of microwave integrated circuits. In many cases, when a high isolation between crossing strips is required in a rather large frequency band, it is preferable to avoid a trivial separation of the strips by a dielectric layer. Moreover, it cannot be sometimes realized due to technological reasons. For example, the technological process of fabrication of hightemperature superconducting planar circuits does not provide layered structures, such as superconductor-dielectric-superconductor .It is well known that a single-layer analog of the crossover is the 0-dB forward-coupled directional coupler @C) [l], [2]. The branch-line configurations are of main practical interest for this purpose. Different versions of 0-dB branch-line DC are known. The three-branch DC ( Fig.1-a)

Ultra-Compact Electromagnetic Metamaterial Transmission Line and Its Application in Miniaturized Butler Matrix

“…In order to realize the miniaturization of branch-line coupler and crossover by using the proposed EM-MTM TL structure, the key procedure is to design 50.0, 35.3 and 25.5 ohm EM-MTM TL sections with specified phase shift, typically as 90-degree respectively, and then assemble them in integrated circuits to form the miniaturized branch-line coupler and crossover. According to [25], we know that the impedance of the proposed structure depends on the width of feed lines, and the widths of the designed 50.0, 35.3 and 25.5 ohm EM-MTM TL sections are 1.6 mm, 2.5 mm and 4.0 mm. As shown in Figure 5, the simulated S-parameters and phase of these three sections are shown, indicating that these sections obviously operate at 0.86 GHz with exact 90-degree phase shift.…”

Analysis and design of double-ring crossover junction with arbitrary diagonal port impedances

“…Recently, many papers on the use or design of novel crossover circuits have been presented [1][2][3][4][5][6][7][8][9][10][11]. In a fully planar circuit, when two signal traces cross over each other, the most intuitive way to have good isolation is to use three-dimensional structure such as via, wire-bond and air-bridge [1][2][3].…”

“…To reduce the design complexity, a series of multi-port planar couplers with crossover applications have been presented in [4][5][6][7][8][9][10]. An ideal four-port crossover can provide 0-dB insertion loss to diagonal ports and perfect isolation to adjacent ports.…”

“…The "window"-design circuits are composed of several branchline couplers connected in two dimensions. Such circuits may have an improved bandwidth if the characteristic impedances of the constitution branches can be properly designed [8].…”

Design of Compact Symmetric Four-Port Crossover Junction

“…In [7], a novel planar configuration of 0 dB directional coupler is presented as a single-layer crossover in microwave integrated circuits. The "window"-shape circuits in [8] are composed of several branch-line couplers connected in two dimensions. Such circuits may have an improved bandwidth if the characteristic impedances of the constitution branches can be properly designed.…”