Compact Elliptic-function Low-pass Filter Research Articles

Compact elliptic-function lowpass filter using improved mushroom resonator cells

An improved mushroom resonator cell is proposed for the design of the compact elliptic-function lowpass filter (LPF). This resonator cell provides sharp skirt and wide stopband for the LPF. As an example, a five-pole elliptic-function LPF with cutoff frequency 2.5 GHz has been designed and fabricated. The measurement results show good agreement with those of simulations. The measured insertion loss in the passband is less than 0.3 dB, and the stopband over 20 dB is from 3 to 10.7 GHz. The dimensions of the LPF are as small as 6 × 15 mm (i.e. 0.082λ × 0.18λ where λ is the guided wavelength at cutoff frequency).

Compact Elliptic function Lowpass Filter based on Defected Ground Structure

A compact microstrip lowpass filter (LPF) with prominent cutoff sharpness and wide stopband is presented. The microstrip LPF is composed of a broadened microstrip line on the top side of the microstrip structure, an H-shaped defected ground structure (DGS) and a modified dumbbell (DB) DGS in the ground plane. It has a simple design procedure and easily can be tuned. The designed filter is developed and experimental results show that it has a sharp cutoff frequency response.

Compact Elliptic-Function Low-Pass Filter Using Defected Ground Structure

A novel elliptic-function low-pass filter (LPF) is presented, which consists of a dumb-bell-shaped defected ground structure (DB-DGS), a spiral-shaped defected ground structure (SP-DGS) and a broadened microstrip line. The DB-DGS provides the required wideband attenuation in stopband, while the SP-DGS provides steep transition from passband to stopband. A 2.4 GHz five-pole LPF is developed and experimental results show that it has a sharp cutoff frequency response. The measured passband insertion-loss is below 0.3 dB, and the rejection band over 20 dB is from 2.95 to 8.25 GHz.

Design of compact, broad-stopband lowpass filter using modified stepped impedance hairpin resonators

A compact elliptic function lowpass filter using a stepped impedance hairpin resonator is proposed. The filter has the advantages of compact size, low insertion loss, easy fabrication, a wide stopband, and sharp cutoff frequency response. In order to cause a sharp cutoff frequency response and the wide stopband suppression, a coupled stepped impedance resonator is taken into consideration for the newly proposed lowpass filter. A demonstration filter has been designed, fabricated and tested, and the results agree well with the theory. The size of the filter is less than 0.037λg×0.093λg, where λg is the waveguide length at the cutoff frequency 1.5 GHz, and the 10 dB rejection stopband can be extended to more than 15 GHz. The filter is useful for many microwave system applications.

Compact elliptic-function low-pass filters using microstrip stepped-impedance hairpin resonators

A compact elliptic-function low-pass filter using microstrip stepped-impendance hairpin resonators and their equivalent-circuit models are developed. The prototype filters are synthesized from the equivalent-circuit model using available element-value tables. To optimize the performance of the filters, electromagnetic simulation is used to tune the dimensions of the prototype filters. The filter using multiple cascaded hairpin resonators provides a very sharp cutoff frequency response with low insertion loss. Furthermore, to increase the rejection-band bandwidth, additional attenuation poles are added in the filter. The filters are evaluated by experiment and simulation with good agreement. This simple equivalent-circuit model provides a useful method to design and understand this type of filters and other relative circuits.