Browse Prior Art Database

MMIC BROADBAND QUADRATURE COUPLER/BANK REJECT FILTER

IP.com Disclosure Number: IPCOM000006463D
Original Publication Date: 1992-May-01
Included in the Prior Art Database: 2002-Jan-07
Document File: 2 page(s) / 101K

Publishing Venue

Motorola

Related People

Lyle Fajen: AUTHOR

Abstract

This publication describes a broadband quadrature coupler which is appropriate for microwave monolithic integrated circuit (MMIC) applications, especially at mil- limeter wavelengths above 26 GigaHertz. It is useful with ordinary microstrip MMIC contigurations or with copla- nar MMIC designs.

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MOTOROLA INC. Technical Developments Volume 15 May 1992

MMIC BROADBAND QUADRATURE

COUPLER/BANK REJECT FILTER

by Lyle Fajen

  This publication describes a broadband quadrature coupler which is appropriate for microwave monolithic integrated circuit (MMIC) applications, especially at mil- limeter wavelengths above 26 GigaHertz. It is useful with ordinary microstrip MMIC contigurations or with copla- nar MMIC designs.

  The most commonly used coupler is a branch line coupler, which is simple to design and fabricate. F'rob- lems with ordinary branch line couplers used in MMIC applications include narrow bandwidth, limited imped- ance range, structural complexity, unwanted parasitic effects and poor size match to MMIC applications.

  A second type of coupler is the Lange coupler, which has broad bandwidth but which requires narrow gap dimensions and metallized interconnections exhibiting unwanted parasitic effects at milliieter wavelengths.

  A solution to the problems mentioned above is offered by a new coupler as shown schematically in Fig- ure 1. This device is fabricated on the first metal layer of a MMIC chip. It uses dimensions which are compatible with other MMIC devices. Figure 1 corresponds to a design which employed 50 Ohm transmission lines, shown as wide lines in Figure 1, together with 75 Ohm transmission lines, shown as narrow lines in Figure 1. The dielectric substrate is typically 100 micrometers thick. The design shown in Figure 1 requires 500 microme- ters of overall length for operation at 100 GigaHertz. Typical MMIC ships are 1.5 by 3.5 milliieters, provid- ing area for several such couplers in a MMIC structure. Other impedances can be employed by scaliig the lie widths or the thickness of the dielectric substrate. The frequency of operation is scaled by adjusting the line lengths (shorter line lengths correspond to higher fre- quencies). Figure 2 depicts a serpentine configuration which conserves MMIC chip area.

  The design of Figure 1 corresponds to 50 Ohm input and output impedances for a 3 dB quadrature coupler which functions similarly to a branch line coupler but which uses multiple sections. The individual sections

B Motorola. 1°C. 1992

act to provide performance at the upper frequencies of intere...