A Miniaturised Negative Group Delay Triple Pass Band Filter Using Half Wavelength Meander Step Impedance Resonator

Negative Group delay (NGD) triple passband filter with a lossy Meander Step Impedance Resonator (MSIR) is introduced in this article. The size miniaturization technique by increasing the number of meander turns is presented. In the process of filter design, the calculation of the total inductance value of the meander section is discussed in a simplified way. At the same time, the electrical and physical lengths of each section of meander resonator are calculated. The proposed filter has three passbands at 2.4, 5.0, and 7.4 GHz. The Group Delay (GD) in the three passbands is -2.5 ns, -2.1 ns, and -2.0 ns respectively. The more the number of meander turns is, the more the NGD will be. The proposed design is well equipped to be used in feed-forward and feed-back power amplifier applications. The frequency response exhibits satisfactory Return Losses (RLs) of -24, -25, and -22 dB at these three passbands. Four Transmission Zeros are generated at 3.35, 3.98, 6.2, and 8.31 GHz using an absorptive Folded SIR (FSIR) structure which improves the stopband performances. The overall dimension of the filter is (20.7 x 12) mm = (0.16 x 0.09)Ag.