Rectangular Waveguide Filters With Meandered Topology

Abstract

In this paper, a new topology for rectangular waveguide band-pass and low-pass filters is presented. A simple, accurate and robust design technique for these novel meandered waveguide filters is provided. The proposed filters employ a concatenation of ±90º E-plane mitered bends (±90ºEMBs) with different heights and lengths whose dimensions are consecutively and independently calculated. Each ±90ºEMB satisfies a local target reflection coefficient along the device so that they can be calculated separately. The novel structures allow to drastically reduce the total length of the filters and to embed bends if desired, or even to provide routing capabilities. Furthermore, the new meandered topology allows the introduction of transmission zeros above the passband of the low-pass filter, which can be controlled by the free parameters of the ±90ºEMBs. A band-pass and a low-pass filter with meandered topology have been designed following the proposed novel technique. Measurements of the manufactured prototypes are also included to validate the novel topology and design technique, achieving excellent agreement with the simulated results.

Robust Tolerance Design of Bandpass Filter With Improved Frequency Response for Q-Band Satellite Applications

“…Firstly, the order of the filter, N, the type of frequency response (all-pole), and the return loss in the passband (between the lower cut-off frequency, f1, and the upper cut-off frequency, f2) must be specified. These frequencies correspond to electrical lengths of the commensurate-lines of − and + , respectively, whereas is the electrical length at the central frequency of the passband, fπ, and can be calculated using (1) as it was explained in [7]:…”

“…where c is the speed of light in vacuum and fπ is the central frequency of the passband calculated as in [7]. In order to avoid glitches in the passband due to resonant higher-order modes in the larger cavities generated by manufacture imperfections and to obtain a gap easily fabricated with standard CNC milling in the smaller ones, the mapping of with the physical dimensions of the waveguide sections must be done applying the following sequence: if Zi < Zi+1 then bi < bi+1 and ai > ai+1 whereas if Zi > Zi+1 then bi > bi+1 and ai < ai+1.…”

“…After the calculation of the heights bi and widths ai of each section, their initial lengths = /2 must be modified to compensate for the phase variation produced by the effect of the higher-order modes at the consecutive section junctions. In order to do it, the phase conditions for the S11 and S21 parameters must be satisfied and the length of each section will be modified to restore them as detailed in [7]. A final optimization might be done, if needed, to adjust the return loss parameter.…”

“…Afterwards, the height values of the other sections are obtained using (2), employing amin for the larger waveguide sections and amax for the smaller ones. Finally, the lengths are adjusted to satisfy the S11 and S21 phase conditions given in [7]. In order to fabricate the filter by CNC milling, rounded corners with a radio equal to 0.3 mm have been included in the structure and the dimensions have been slightly optimized to compensate the effects (final dimensions considering rounded corners shown in Table II).…”

An X-band waveguide bandpass filter with enhanced stopband using offset resonators

“…Waveguide bandpass filters (BPFs), featuring the merits of low insertion loss and high-power capacity, are widely used in modern wireless communication and radar systems [1,2,3,4]. However, the spurious resonances deteriorate the filter's stopband performance.…”