Quad‐band bandpass filter design by embedding dual‐band bandpass filter with dual‐mode notch elements

Abstract

A quad-band bandpass filter of compact dimensions by embedding several dual-mode notch elements into a stub-type dual-band bandpass filter is presented, and the four passbands are achieved by splitting the two passbands of the dual-band bandpass filter with two notch bands generated by the dual-mode notch elements. A prototype filter with passbands located at 1.4-1.7, 2.1-2.3, 3.3-3.6 and 5.2-5.4 GHz is designed with the help of optimisation methods. Good agreement between simulations and measurements are achieved, demonstrating good features such as controllable and wide bandwidths, higher filter order, compact dimensions and high isolations.

Synthesis of multi-band bandpass filters using semi-hidden multi-mode coupling elements

“…3, Compute the equivalent LC values of every multi-mode resonator at every passband using (4). Merge the multi-mode capacitors into the nearby multi-mode resonators, and modify the equivalent LC values of the multi-mode resonators with (6).…”

“…Early solutions realize multi-band response by cascading a bandpass and a bandstop filters [1] or by parallel connecting bandpass filters [2,3], and two or more pre-designed filters and even extra impedance matching networks are needed, thus resulting in large dimensions. A mutual-embedding structure of bandpass filters and bandstop filters can result in double passbands with compact dimensions [4], but complete synthesis method is absent and circuit optimization is required. Microstrip and DGS (defected ground structure) resonators implemented on two sides of a substrate are combined to realize multiple passbands with large design difficulty, due to interferences between the two layer circuits [5,6].…”

Compact quad-band bandpass filter based on stub-loaded resonators

“…The bandwidth of the four passbands is different and their loss varies from 2.18-0.93 dB. The quadband filter in [3] is implemented by loading a transmissionline with either open or short-circuited stubs in a parallel configuration. With this structure the passband response deteriorates by loading the transmission-line resulting from the complex coupling between adjacent resonant stubs.…”

Compact Planar Quad-Band Bandpass Filter for Application in Gps, Wlan, Wimax and 5g Wifi

“…Quad-band bandpass filters have thrived in recent years [6][7][8][9][10][11][12][13]. In [6], a quad-band BPF is achieved based on splitting two passbands of a dual-band BPF by transmission zeros (TZs).…”

“…In [6], a quad-band BPF is achieved based on splitting two passbands of a dual-band BPF by transmission zeros (TZs). This method is not applicable when there is a great distance between pass bands.…”