A novel compact microstrip lowpass filter with high performance is designed and analysed based on transfer function. The main resonator consists of L-shaped and T-shaped patches. The L-shaped resonator is used to increase the width of the stopband. The presented filter has −3 dB cutoff frequency at 2 GHz. It also has a wide stopband about 17.82 GHz with the suppression level of −21 dB. The transition band is ∼168 MHz from −3 to −40 dB. The locations of transmission zeros are calculated by transfer function. The presented lowpass filter has other advantages, such as high return loss more than 20 dB and low insertion loss <0.15 dB in the passband. The size of the filter is only 0.087 × 0.170 λ g 2 , where λ g is the guided wavelength at the cutoff frequency. The proposed lowpass filter has the figure of merit of 50,285, which shows its strong efficiency. The lowpass filter is simulated and fabricated and there is a good agreement between the simulation and measurement results.
A novel scheme of a shrunken Wilkinson power divider with harmonic suppression, using two identical resonators in the conventional Wilkinson power divider is designed. Moreover, the LC equivalent circuit and its relevant formulas are provided. To substantiate the functionality and soundness of design, a microstrip implementation of this design operating at 1 GHz with the second to eighth harmonic suppression, is developed. The proposed circuit is relatively smaller than the conventional circuit, (roughly 55% of the conventional circuit). Simulation and measurement results for the proposed scheme, which are highly consistent with one another, indicate a good insertion loss about 3.1 dB, input return loss of 20 dB and isolation of 20 dB, while sustaining high-power handling capability over the Wilkinson power divider.
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