microwave filter

microwave filter

[′mī·krə‚wāv ‚fil·tər]
(electromagnetism)
A device which passes microwaves of certain frequencies in a transmission line or waveguide while rejecting or absorbing other frequencies; consists of resonant cavity sections or other elements.

Microwave filter

A two-port component used to provide frequency selectivity in satellite and mobile communications, radar, electronic warfare, metrology, and remote-sensing systems operating at microwave frequencies (1 GHz and above). Microwave filters perform the same function as electric filters at lower frequencies, but differ in their implementation because circuit dimensions are on the order of the electrical wavelength at microwave frequencies. Thus, in the microwave regime, distributed circuit elements such as transmission lines must be used in place of the lumped-element inductors and capacitors used at lower frequencies. This can make microwave filter design more difficult, but it also introduces a variety of useful coupling and transmission effects that are not possible at lower frequencies.

The majority of modern microwave filters are designed by using the insertion-loss method, whereby the amplitude response of the filter is approximated by using network synthesis techniques that have been extended to accommodate microwave distributed circuit elements. A general four-step procedure is followed: determination of filter specifications, design of a low-pass prototype filter, scaling and transforming the filter, and implementation (conversion of lumped elements to distributed elements).

Microwave filters are implemented in many ways. Waveguide cavity band-pass filters have very low insertion loss, making them preferred for frequency multiplexing in satellite communication systems. Coaxial low-pass filters, made with sections of coaxial line with varying diameters, are compact and inexpensive. Planar filters in microstrip or stripline form (see illus.) are important for integration with hybrid or monolithic microwave integrated circuits. While planar filters are usually more cost effective than waveguide versions, their insertion loss is usually greater. Computer-aided design procedures are used in the synthesis of more sophisticated amplitude and phase responses, and active microwave devices (field-effect transistors) are used to provide filters with gain or tunable response characteristics. See Coaxial cable, Computer-aided design and manufacturing, Microwave solid-state devices

References in periodicals archive ?
Neural network inverse modeling and applications to microwave filter design, IEEE Microwave Theory and Techniques 56(4): 867-879.
The book can be used for an advanced graduate course in miniaturized RF and microwave filters, and can be used to supplement traditional courses in microwave filter design.
In a separate announcement, Smiths said it had acquired US firm Lorch Microwave - adding microwave filter technology to its electronic components and subsystems Interconnect business -in a deal valued at pounds 14.
The microwave filter uses a silicon carbide fiber that converts microwave energy to heat, allowing the filter to operate at high enough temperatures either while running or during unavoidable cold starts.
API Technologies' ISO 9001-2008-certified Rancho Cordova facility designs and manufactures space-grade and high-reliability microwave filter products for satellites and wireless communication and defense applications.
9, 2014 /PRNewswire-iReach/ -- Gowanda Holdings, LLC, an Addison Capital portfolio company, announced today that it has acquired the business of specialty RF and Microwave Filter manufacturer, TTE, Inc.
This volume describes microwave filter design and applications for communications systems for senior level undergraduate or graduate students, researchers, communications and systems designers and planners, and experienced filter designers.
CBU's products are a natural complement and extension to our existing frequency control product offerings which already include microwave synthesizers, multiple channel filter banks and preselectors, GPS low noise amplifiers, and numerous RF and microwave filter components.
In 1984, he joined Microwave Filter Company (MFC), an aerospace, military, satellite and cable communications product development company in Syracuse, N.
CDNX:UBS) to provide leading edge microwave filter technology equipment that address the emerging satellite digital audio radio service (SDARS) market.
Bowler applauded the contributions of other Alliance partners -- Andrew Corporation and Microwave Filter -- in assisting in the successful field tests and planning the commercial trial launch.
Each chapter concerning the design of a microwave filter starts with a characterization of the elements in the microwave structure.

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