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A waffle-iron filter is a type of waveguide filter used at microwave frequencies for signal filtering. It is a variation of the corrugated-waveguide filter but with longitudinal slots cut through the corrugations resulting in an internal structure that has the appearance of a waffle-iron. Waffle-iron filters are particularly suitable where both a wide passband, and a wide stopband free of spurious transmission modes, are required. They also have a high power-handling capability. Applications include suppressing the harmonic output of transmitters and the design of wide-band diplexers. They are also used in industrial microwave manufacturing processes to prevent the escape of microwave radiation from the microwave chamber. Filters with an analogous design are now appearing in photonics, but, due to the higher frequency, at a much smaller scale. This small size allows them to be incorporated into integrated circuits. Design techniques for waffle-iron filters include image-parameter methods, network synthesis methods and numerical analysis methods. Network synthesis is a more advanced method than image-parameter techniques but the latter can still be used where a simple repeated-pattern design is desired. Numerical methods can be used to analyse either design. ==Description== The waffle-iron filter was invented by Seymour B. Cohn at Stanford Research Institute in 1957.〔Young, p.10〕 The basis for the filter is the corrugated-waveguide filter. This consists of a series of ridges, or corrugations, across the width of the filter. There are corrugations inside the waveguide on both the top and bottom surfaces. The rising and descending ridges are aligned with each other but do not meet in the middle; there is a gap in between. In the waffle-iron filter there are, in addition, slots cut through the ridges down the length of the waveguide. This leaves a matrix of square islands, or teeth, on the top and bottom surfaces.〔Matthaei ''et al.'', p.390〕 Waffle-iron filters are, in essence, low-pass filters but like all waveguide devices will not transmit anything below the waveguide cutoff frequency. Waffle-iron filters are used where both a wide passband with low insertion loss, and a wide (sometimes very wide) stopband are needed. They are particularly good where suppression of spurious modes is required.〔Levy, pp.526, 527 Manuilov and Kobrin, 2005, p.93 Manuilov ''et al.'', 2009, p.526 Matthaei ''et al.'', p.390〕 Waffle-iron filters have been built with a wide stopband and attenuation.〔Bingham, p.29〕 Even wider stopbands are possible with a relaxed attenuation specification.〔Matthaei ''et al.'', p.393〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Waffle-iron filter」の詳細全文を読む スポンサード リンク
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