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Coplanar branch-line and rat-race couplers for W-band applications

Koplanare Branchline- und Ratrace-Koppler für W-Band-Anwendungen
 

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Institution of Electrical Engineers -IEE-, London; IEEE Microwave Theory and Techniques Society; International Union of Radio Science -URSI-:
26th European Microwave Conference 1996. Proceedings
Swanley: Nexus, 1996
pp.602-606
European Microwave Conference (EuMC) <26, 1996, Prag>
German
Conference Paper
Fraunhofer IAF ()
branch line coupler; Branchline-Koppler; coplanar; koplanar; microwave; Mikrowelle; millimeter wave; Millimeterwelle; rat-race coupler; Ratrace-Koppler

Abstract
In this paper, we report on coplanar branch-line and rat-race couplers on GaAs for use in balanced mixers, investigated theoretically and experimentally over the frequency range from DC to 120 GHz. For optimum spurious response suppression at the IF-port of a balanced mixer, a coupler must provide the required phase delay at its ports feeding the non-linear devices. Whereas in microstrip (MS) technology these types of couplers have been extensively investigated in the past, coplanar waveguide (CPW) technology is still lacking similar broadband models, making millimetre-wave circuit design difficult. For the characteristic impedance levels 30,50 and 67 Ohm, a model library was developed for transmission lines and line elements like air bridges and corners, and implemented into HP-MDS. On the basis of these models, we designed a branch-line coupler, a capacitively loaded branch-line coupler and a rat-race coupler for W-band applications. For the analysis of the phase relation between the different ports of these hybrids, 2-port test structures were designed and processed. The 'on-wafer' measured S- parameters of the couplers show excellent agreement with the simulated data in both amplitude and phase over the entire frequency range.

: http://publica.fraunhofer.de/documents/PX-8682.html