A wideband quasi-elliptical bandpass filter with enhanced reject-band performance is presented. The proposed bandpass filter utilizes a new asymmetric defected ground structure (DGS) under a pair of end-coupled microstrip line. The DGS consists of two square headed slots connected transversely with a rectangular slot. The DGS-microstrip resonator provides band-accept filtering characteristics. To be equivalent to the circuit DGS is demonstrated. The presented equivalent circuit shows both resonant and anti-resonant properties. The equivalent circuit parameters are extracted using the modeling method of proposed DGS. A better selectivity in lower transition band in comparison to upper transition band is observed in the frequency response. To improve the roll-off in upper transition band, a pole is created by putting an additional DGS unit under the same microstrip line. The combined structure shows bandpass characteristics with deep and wide stopband on both sides of the passband. The bandwidth and centre frequency of the filter is controlled by the dimensions of both DGS cells. The article presents some promising patents on Defected Ground Structure Resonators and Admittance J-Inverter.
Keywords: Microstrip, DGS, quasi-elliptic, lowpass, bandpass filter, Defected Ground Structure Resonators, Admittance J-Inverter, passband, microwave filters, attenuation zero, transmission zero, end-coupled line, Butterworth, Chebyshev types, compact planar design, LC resonant circuit, RC resonant circuits, TOPOLOG, square headed slots, relative dielectric constant, STOPBAND, capacitance, inductance, electromagnetic field, Transition area, Microwave officesimulator, tangent, circuit-simulated S-parameters, sharpness ratio, stopband attenuation, passband insertion loss, Microwave office-simulator, conductor strip, attenuation minima, parallel capacitances, anti-resonance, prototype resonator, EM-simulated, shunt capacitors, slot-heads, S-parameters, physical dimension, rising edge, falling edge, Arlon substrate
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