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MINIATURIZED MODE TYPE ISOLATORS EMPLOYING RESISTIVE RESONATOR TERMINATIONS

IP.com Disclosure Number: IPCOM000005667D
Original Publication Date: 1987-Oct-01
Included in the Prior Art Database: 2001-Oct-24
Document File: 1 page(s) / 53K

Publishing Venue

Motorola

Related People

Joseph Staudinger: AUTHOR [+2]

Abstract

Mode type circulators/isolators are formed using a ferrite material which is magnetically biased to form a resonator. To this resonator, matching networks (usually quarter wave impedance transformers) are connected to transform the impedance to a nominal level (usually 50 ohms). To obtain a two-port isolator, the isolation port of the circulator is resistively terminated at the end of the matching network.

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MOlWROlA Technical Developments Volume 7 October 1987

MINIATURIZED MODE TYPE ISOLATORS EMPLOYING RESISTIVE RESONATOR TERMINATIONS

by Joseph Staudinger and Warren Seely

   Mode type circulators/isolators are formed using a ferrite material which is magnetically biased to form a resonator. To this resonator, matching networks (usually quarter wave impedance transformers) are connected to transform the impedance to a nominal level (usually 50 ohms). To obtain a two-port isolator, the isolation port of the circulator is resistively terminated at the end of the matching network.

   Ratherthan terminate the isolation port as mentioned above, the port can be resistively terminated direct- ly at the resonator and hence eliminate the need for an impedance transformer at this port. The concept is shown in the Figure where the isolated port is terminated on the disk resonator. The termination consists of a resistor formed by printing a resistive paste on the resonator. The paste is then fired and can later be trimmed for a precise resistance value.

Terminating the isolation port in this manner offers several advantages,

-The overall size of the isolator will be smaller due to elimination of the transformer on the isolated port.

-The resistive termination may provide a better match to the resonator impedance which then results in higher isolation. This is particularly evident when the resonator geometry and operating point are chosen such that the resonator impedance stays pri...