Editing Circulator (section)

====Microstrip junction circulators====

[[File:Microstrip Circulator a.jpg|left|100px|thumb|Microstrip junction circulator.]]

[[File:Tr-module.jpg|thumb|500px|Transmit-Receive (T-R) module used in the [[Euroradar CAPTOR|CAPTOR-E]] [[Active electronically scanned array|active electronically scanned array (AESA)]] airborne radar.  The microstrip junction circulator is visible at the left end of the module.  The left port of the circulator connects to the antenna port of the module and ultimately to an element of the [[phased array]].  The top right circulator port connects to receiver and signal processing circuitry, and the lower right circulator port connects to the transmitter power amplifier near the center of the module.  In this instance, the circulator performs a [[Duplexer|duplexing]] function.]]

The microstrip junction circulator is another widely-used form of circulator<ref name="Fuller">{{Cite book|title=Ferrites at Microwave Frequencies|first=A. J.|last=Baden-Fuller|date=1987|publisher=Peter Peregrinus Ltd.|isbn=0-86341-064-2}}</ref> that utilizes the [[microstrip]] transmission line topology.  A microstrip circulator consists primarily of a circuit pattern on a ferrite substrate.  The circuit is typically formed using [[Thick film technology|thick-film]] or [[Thin film|thin-film]] metallization processes, often including [[photolithography]].  The ferrite substrate is sometimes bonded to a ferrous metal carrier, which serves to improve the efficiency of the magnetic circuit, increase the mechanical strength of the circulator, and protect the ferrite from [[thermal expansion]] mismatches between it and the surface to which the circulator is mounted.  A permanent magnet that is bonded to the circuit face of the ferrite substrate provides the static magnetic bias to the ferrite.  Microstrip circulators function in the same way as stripline junction circulators, and their basic theory of operation is the same.  In comparison with stripline circulators, electrical performance of microstrip circulators is somewhat reduced because of [[Electromagnetic radiation|radiation]] and [[Planar transmission line|dispersion]] effects.

The performance disadvantages of microstrip circulators  are offset by their relative ease of integration with other planar circuitry.  The electrical connections of these circulators to adjacent circuitry are typically made using [[Wire bonding|wire bonds]] or ribbon bonds.  Another advantage of microstrip circulators is their smaller size and correspondingly lower mass than stripline circulators.  Despite this advantage, microstrip circulators are often the largest components in microwave modules.<ref name="Palmer, Kirkwood, Gross, et al.">{{cite journal|title=A Bright Future for Integrated Magnetics|journal=IEEE Microwave Magazine|date=June 2016|issn=1527-3342|pages=36–50|volume=20|number=6|doi=10.1109/MMM.2019.2904381|first1=William|last1=Palmer|first2=David|last2=Kirkwood|s2cid=148572410 |display-authors=etal}}</ref>