Waffle-iron Filters Research Articles

Design of a high-power harmonic waveguide filter for radar transmitter

In this article, we present the research results on the designing and manufacturing method of a high-power harmonic filter applied in the X-band transmitter system. The harmonic filter utilizes Waffle-iron filters and quarter-wavelength converters on the waveguide. As a result, the loss and ripple within the passband are improved, while meeting the requirements of cutting off high-order harmonics. Based on the application of microwave theory and simulation software tools, the research team have calculated, designed and manufactured a harmonic filter that meets all the requested specifications for application in X-band transmitter systems: Loss ≤ 0,12dB@8,9-9,6GHz; Reflection coefficient ≤ -20dB@8,9-9,6GHz; Frequency selectivity ≤ -40dB@2nd harmonic, 3rd harmonic, 4th harmonic.

Design Procedure for New Compact Waffle-Iron Filters With Transmission Zeros

In this paper, a novel waffle-iron filter with transmission zeros at multiple frequencies, along with its design procedure, is presented. The proposed filter features a high-power behavior and a wide rejected band in a single compact structure by means of a set of transmission zeros that can also be placed close to the passband. Its design method rests on a divide-and-rule strategy, where the physical dimensions of the constituent design entities can be easily computed in a very short time. A novel high-power compact waffle-iron filter with transmission zeros at multiple frequencies has been designed as well as several classical waffle-iron filters with transmission zeros at one frequency only, using a detailed step-by-step procedure which avoids the brute-force optimizations needed until now. Multipactor and corona simulations have been conducted proving a high-power handling capability of 1.8 kW and 78.6 W, respectively. A prototype of the novel filter has been fabricated, obtaining a remarkable accordance between the simulated and measured results.

Waffle-Iron Harmonic Suppression Filter (Correspondence)

Essentially, waffle-iron filters are waveguide low-pass filters with wide stop bands above their pass bands. The L-band waffle-iron filter discussed in this correspondence was originally developed at the Stanford Research Institute, Menlo Park, CA, USA. Subsequent reports and modifications have been presented by Young and Schiffman [1963]. This correspondence serves to supplement the existing information on waffle-iron filters, particularly as to their high power characteristics and the modifications required to achieve the high power characteristics.

Postscript to Two Papers on Waffle-Iron Filters(Correspondence)

Waffle-iron filters are waveguide "low-pass" filters, that is, they have a wide stop band above their pass band. They are useful for both low-power and high-power applications. A brief history of the development of this filter at Stanford Research Institute is given by Young and Schiffman. A new design principle which makes it possible to extend the pass band from, (typically) about 10 percent to about 40 per cent is also described; the pass band of that filter covers almost the whole of the recommended waveguide band, while its stop band extends from the second to the fourth harmonic, inclusive.

A High-Power Wide-Band Waffle-Iron Filter

This paper describes the design and measured performance of an L-band model of a high-power wide-band low-pass waffle-iron filter. Three different waffle-iron filters with staggered stop bands are connected in series to give a combined stop band that extends from 2.2 Gc to 13.7 Gc. where the attenuation is 60 db or greater. The waffle-iron filter attenuates all propagating waveguide modes which can propagate at frequencies in the above stop band. In the pass band the waffle-iron filters are matched to full size L-band waveguide using quarter-wavelength stepped transformers. The pulsed power-handling capacity without breakdown is measured to be over 1.4 Mw peak power with air at atmospheric pressure filling the filter.

New and improved types of waffle-iron filters

Waffle-iron filters are waveguide low-pass filters with wide stop-bands. The waffle-iron filter was first described in 1957 in a report of the Stanford Research Institute, and upon this all subsequent designs have been based. The pass-band fractional bandwidths were generally in the order of 10–20%, and the unpressurized pulse power-handling capacity was about 1.5 MW at the L-band. The stop-band attenuation was typically more than 60 dB from below the second harmonic to beyond the fourth harmonic frequency. New filters have recently been developed with pass-band fractional bandwidths of over 40% (covering almost the whole recommended frequency band of a standard waveguide) and pulse power-handling capacity, without pressurization, of up to about 8 MW at the L-band, while the stop-band attenuation and bandwidth remain as good as before.