Design of a compact microstrip lowpass filter with sharp roll-off using combined T-shaped and L-shaped resonators

作者：Jahanbakhshi M; Hayati M^*

来源：Electronics Letters, 2016, 52(23): 1931-1933.

DOI：10.1049/el.2016.3432

• resonator filters
• microstrip filters
• low-pass filters
• transfer functions
• UHF filters
• compact microstrip low-pass filter design
• sharp roll-off
• combined T-shaped-L-shaped resonators
• transfer function
• transmission zeros
• return loss
• cut-off frequency
• frequency 2 GHz

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 cut-off 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 approximate to 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 x 0.170 (2)(g), where (g) is the guided wavelength at the cut-off 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.

• 出版日期2016-11-10