Rat-race coupler

About: Rat-race coupler is a research topic. Over the lifetime, 1546 publications have been published within this topic receiving 19557 citations. The topic is also known as: hybrid ring coupler.

An out-of-plane grating coupler for efficient butt-coupling between compact planar waveguides and single-mode fibers

Abstract: We have designed and fabricated an out-of-plane coupler for butt-coupling from fiber to compact planar waveguides. The coupler is based on a short second-order grating or photonic crystal, etched in a waveguide with a low-index oxide cladding. The coupler is optimized using mode expansion-based simulations. Simulations using a 2-D model show that up to 74% coupling efficiency between single-mode fiber and a 240-nm-thick GaAs-AlO/sub x/ waveguide is possible. We have measured 19% coupling efficiency on test structures.

A novel composite right-/left-handed coupled-line directional coupler with arbitrary coupling level and broad bandwidth

Abstract: A novel composite right-/left-handed (CRLH) backward-wave coupled-line directional coupler with arbitrary coupling level and broad bandwidth is presented, explained by even/odd-mode analysis, validated by full-wave simulations, and demonstrated by experiments. First, the CRLH-transmission-line (CRLH TL) theory is given, and a microstrip implementation of a CRLH TL is described. A simple circuit model is then proposed both for the understanding and design of the coupler. The coupler exhibits very unusual characteristics, such as zero electrical length, imaginary even/odd-mode characteristic impedances, and coupling dependence on even/odd attenuation length (instead of propagation length). Both a quasi-0and 3-dB coupler are demonstrated experimentally. The 3-dB coupler exhibits amplitude balance of /spl plusmn/2 dB over a huge bandwidth of 50% (3.5-5.8 GHz), phase balance of 90/spl deg//spl plusmn/5/spl deg/ from 3.0 to 4.0 GHz and directivity of 20 dB.

A novel approach to the design and implementation of dual-band compact planar 90/spl deg/ branch-line coupler

Abstract: This paper presents the design of a novel branch-line coupler that can operate at two arbitrary frequencies. The proposed circuit also features compact size and planar structure. Explicit design formulas of the proposed dual-band coupler are analytically derived. Moreover, practical issues such as the realization of branch-line impedance and optimum choice of circuit topologies are addressed. For verification purposes, both simulated and measured results of a microstrip branch-line coupler operating at 900/2000 MHz are included.

Half Mode Substrate Integrated Waveguide (HMSIW) 3-dB Coupler

Abstract: In the microwave band, substrate integrated waveguide (SIW) couplers take the advantages of low profile, low insertion loss, low interference etc., but suffer from the big size. In this letter, a novel half mode substrate integrated waveguide (HMSIW) 3-dB coupler is proposed, which keeps the good performance of the SIW coupler with nearly a half reduction in size. Simulated results are in agreement with the measured data

Miniaturized fractal rat-race, branch-line, and coupled-line hybrids

Abstract: In this paper, space-filling curves have been used to realize a family of miniaturized hybrids. The large surface area occupied by a conventional structure has been significantly reduced through the use of space-filling curves having the same electrical characteristics. Several space-filling curves have been studied and implemented in different designs. The second-iteration Moore rat-race coupler occupies only 12.6% of the conventional coupler's area, while the area of the second-iteration Sierpinski branch-line coupler is 24.7% of the conventional case. On the other hand, a nine-section Minkowski coupled-line balun is confined in 60% of the conventional balun's area. However, the effective size reduction depends on the used space-filling curve, compression ratio, and associated coupling between segments. The performance of the proposed space-filling hybrids is as good as that of the corresponding conventional structures, and even better in some cases. The design and simulation of the proposed space-filling hybrids have been performed using a moment-method-based full-wave electromagnetic simulator. Measurements of one fabricated coupler prototype are in good agreement with simulation results.