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Title: Design of high-performance millimeter wave and sub-millimeter wave quasi-optical isolators and circulators
Authors: Hunter, Robert Iain
Robertson, Duncan Alexander
Goy, P
Smith, Graham Murray
Keywords: Faraday rotator
Millimeter waves
Sub-millimeter waves
Ferrite reflection circulator
Complex permittivity
Faraday rotators
QC Physics
Issue Date: May-2007
Citation: Hunter , R I , Robertson , D A , Goy , P & Smith , G M 2007 , ' Design of high-performance millimeter wave and sub-millimeter wave quasi-optical isolators and circulators ' IEEE Microwave Theory and Techniques , vol 55 , no. 5 , pp. 890-898 . , 10.1109/TMTT.2007.895152
Abstract: Faraday rotators using permanently magnetized ferrite materials are used to make quasi-optical isolators and circulators at millimeter wave and sub-millimeter wave frequencies that have far higher performance than their waveguide equivalents. This paper demonstrates state-of-the-art performance for four-port quasi-optical circulators with 60-dB isolation, 0.2-dB insertion loss, and better than 80-dB return loss for devices centered at 94 GHz. A method is presented for the accurate characterization of the complex permeability and permittivity of permanently magnetized ferrites via a series of frequency and polarization dependent transmission and reflection measurements. The dielectric and magnetic parameters for the sample are determined by fitting theoretical curves to the measured data. These fitted parameters are then used in a model for a complete quasi-optical Faraday rotator, including matching layers, allowing the accurate design and fabrication of these devices for any specific operational frequency band in the millimeter wave and sub-millimeter wave regime. Examples are given showing typical results and demonstrating how temperature cycling can significantly improve the temperature stability of these devices, while allowing fine tuning of the center frequency. We also indicate the performance possible at higher frequencies to above 1 THz and outline performance of truly planar isolators where lossy polarizer material is built into the Faraday rotator matching structure.
Version: Publisher PDF
Status: Peer reviewed
ISSN: 0018-9480
Type: Journal article
Rights: (c) 2007 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.
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Physics & Astronomy Research

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