E-plane Filter Design for Space Applications with Advanced and Stringent Performance Requirements
Goussetis, G1; Hong, J.-S.1; Lopez-Villaroya, R1; Kosmopoulos, S.2
1Heriot-Watt University; 2Space Engineering SpA
Various E-plane configurations that imply size reduction, transmission zeros at pre-selected finite frequencies, improved stopband performance and reduced dispersion are proposed to be candidate for IMUX and filtering realization and/or IF filters introduced within adequate Up- and/or Down-Converters. The proposed topologies produce advanced performance characteristics maintaining the low-cost fabrication features of split-block housing all-metal insert E-plane technology.
E-plane triplet filters, can produce transmission zeros at finite frequencies. The concept is based on simultaneous series and parallel coupling of the resonators in a triplet. The resonators are implemented in asymmetric ridge waveguide and printed on an all-metal E-plane insert. A single triplet has been demonstrated by numerical and experimental results to produce a finite transmission zero, which can be employed for sharp roll-off. The selective location of the transmission zero below or above the passband is demonstrated. Numerical simulations reveal the nature of the resonant effects that produce the transmission zero. Larger order filters are proposed to be fabricated as series cascade of triplets.
Furthermore, E-plane filters with slow-wave periodically loaded resonators have also been produced. Following a proof of concept filter with two resonators, a 5-resonator prototype filter has been successfully designed, fabricated and measured. The main aspects of the various full-wave numerical techniques, being custom developed for the design of this type of filter, will be outlined accompanied by a qualitative comparison among simulation and measurement performance evaluation results.
Another topology proposes the implementation of Stepped Impedance Resonators (SIR) in E-plane technology. Variation in the impedance is achieved by stepped change of the ridge waveguide gap within the resonator. The E-plane SIR produces minaturisation as well as improvement in the stopband performance. Numerical and experimental results will be demonstrated for validation.
Lowpass E-plane filters can be produced by cascading ridge waveguides of different gaps. The analysis of the infinite structure has been based on the application of the Floquet theorem and the band diagram has been extracted. This has revealed that the periodic stepped ridge waveguide has a low-pass performance and that transmission zeros are introduced due to the resonance of the periodic ridge waveguide loads. Matching of the infinite structure can be achieved by tapering. The structure is readily integrated with bandbpass E-plane configurations and has been employed to suppress unwanted spurious resonances. Numerical and experimental results will be presented.
1D periodic E-plane structures have been demonstrated to reduce the inherent dispersion of hollow waveguides. This can reduce the unwanted broadening of the time-domain profile of short pulses during transmission along a finite length of the waveguide. A study on the trade-off between the levels of dispersion linearization vs. the group delay has been carried out. Transverse resonance analysis of the structure allows a deterministic synthesis of the E-plane circuit. The improvement is demonstrated by means of an example involving an x-band waveguide.
In the herewith forecasted paper our recent advances in E-plane filters activities will be presented, with emphasis on obtained performance characteristics being suitably associated to dedicated space applications.