Alignment and Adjustment of Synchronously Tuned Multiple-Resonant-Circuit Filters
ABSTRACT A simple method of "tuning up" a multiple-resonant-circuit filter quickly and exactly is demonstrated. The method may be summarized as follows: Very loosely couple a detector to the first resonator of the filter; then, proceeding in consecutive order, tune all odd-numbered resonators for maximum detector output, and all even-numbered resonators for minimum detector output (always making sure that the resonator immediately following the one to be resonated is completely detuned). Also considered is the correct adjustment of the two other types of constants in a filter. Filter constants can always be reduced to only three fundamental types: f0, dr(1/Qr), and Kr(r+1). This is true whether a lumped-element 100-kc filter or a distributed-element 5,000-mc unit is being considered. dr is adjusted by considering the rth resonator as a single-tuned circuit (all other resonators completely detuned) and setting the bandwidth between the 3-db-down-points to the required value. Kr(r+1) is adjusted by considering the rth and (r+1)th adjacent resonators as a double-tuned circuit (all other resonators completely detuned) and setting the bandwidth between the resulting response peaks to the required value. Finally, all the required values for K and Q are given for an n-resonant-circuit filter that will produce the response (Vp/V)2=1 +(Â¿f/Â¿f3db)2n.
Article: Direct-Coupled-Resonator Filters[Show abstract] [Hide abstract]
ABSTRACT: A new analysis is given of direct-coupled-resonator filters that results in excellent response at much greater bandwidths than has previously been possible. The method relies on the fact that the coupling elements can be made into perfect impedance inverters, or "quarter-wave" transformers, by the addition of negative elements in lumped-constant circuits, or of short negative lengths of line in waveguide and transmission-line circuits. Specific design formulas are given for filters constructed of lumped-constant elements, waveguide, and strip or other TEM transmission line, and for pass band response functions of the maximally flat and Tchebycheff types. The formulas include a simple frequency transformation that corrects for the frequency sensitivity of the coupling reactances, and thereby greatly improves the design accuracy for both lumpedconstant and microwave types when the bandwidth is more than a few per cent. Exact response curves computed from typical filter designs are compared to the prototype-function response curves, and it is shown that the design formulas give good results with bandwidths of at least 20 per cent in guide wavelength in the case of waveguide filters, or 20 per cent in frequency for TEM-mode transmission-line and lumped-constant filters.Proceedings of the IRE 02/1957; 45(2):187-196.
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ABSTRACT: The BPF designed by the formula based on strip line shows the center frequency shift and distortion in filter response and this becomes more significant with higher frequency. In this paper, the novel design based on EM simulation is proposed. In the design, the filter is decomposed into individual resonators and, for each resonator, the reactance slope and the inverter values are measured and tuned to desired design values for a inverter BPF prototype. The filter composed with such resonators shows the desired filter response without further tuning. This is because possible effects of discontinuities and dispersion are included in the filter parameter extraction. The method can generally apply to all filters that can be transformed into inverter BPF prototype. The procedure is verified by designing a 5th-order SIR filter and quite general to adapt into the design of a parallel coupled line filter, and hair-pin filter.The Journal of Korean Institute of Electromagnetic Engineering and Science. 04/2009; 20(4).
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ABSTRACT: In this paper, we present a design of a 5th order Chebyshev interdigital band-pass filter using inverter and susceptance slope parameter values obtained from EM simulated multi-port Y-parameters. The shifted length of the resonator is determined when the frequency of the transmission zero is separated far away from the center frequency. For the initial dimensions of the interdigital filter, the filter is decomposed into the individual resonators, and the dimensions are obtained using EM Simulation of the decomposed resonators. However, the interdigital filter with the dimensions determined from the EM simulation of the decomposed resonators shows slightly distorted response from the desired frequency response due to the coupling between non-adjacent resonators. To obtain a EM simulation dataset, EM simulation for this filter is carried out by parameter sweep with constant ratio for the initial values. In this dataset, it is determined the final values for the filter by optimization. The fabricated filter by PCB shows an upper-shift of center frequency of about 70 MHz, which was caused by permittivity changed and tolerance of fabrication.The Journal of Korean Institute of Electromagnetic Engineering and Science. 07/2011; 22(7).