Design of Microstrip Lowpass Filter Using bend Configuration with Excellent sharpness in Transition Band

Abstract

In this letter, a microstrip lowpass filter (LPF) using bend configuration with several excellent features such as a compact size, great roll-off rate and high rejection in the stopband is presented. This structure is composed of a spiral transmission line loaded by several stepped impedance and T-shaped resonators. The cut-off frequency of the proposed filter is equal to 2.73 GHz and the transition band is from 2.73 up to 2.82 GHz with –3 and –20 dB attenuation point, respectively, which represents a very high sharpness in the transition band. To achieve a –40 dB rejection level in the stopband, multiple open stub and T-shaped patches are utilized. An acceptable agreement between EM-simulation and measurement results is observed.

Design of a low pass filter using rhombus-shaped resonators with an analyticalLC equivalent circuit

“…The transfer function and transmission zero of the double rhombus-shaped resonator are extracted similar to the main resonator. They are written in (9) and (11) The main resonator and the double rhombus-shaped resonator cannot generate transmission zero at high frequencies (above 10 GHz). To generate a transmission zero at high frequencies, the capacitance and inductance values of the structure should be decreased.…”

“…To design the final low pass filter, the examined rhombus-shaped resonators are combined in Figure 11. The presented filter generated several transmission zeros, but first and second transmission zeros are really important and so their equations were calculated in (8) and (11). The frequency response of the final filter is illustrated in Figure 12.…”

New design of an adjustable compact microstrip lowpass filter using Z‐shaped resonators with low VSWR

“…LPFs play a key role in wireless communication systems owing to their tasks in eliminating unwanted harmonics and noise 3 . Growing demands for these elements motivate scientists to design LPFs with diverse structures and specifications 4‐19 . C‐shaped structures along with complementary split‐ring resonators were used to design an LPF 4 .…”

“…In another research, hairpin units were utilized to obtain a compact size and also high relative stopband bandwidth (RSB) 7 . Stepped impedance resonators were suggested so as to design LPFs 8‐10 . It should be noted that in References 6 and 7, the unacceptable return loss has an adverse effect on the VSWR, and in Reference 10, the roll‐off rate should be enhanced.…”

Ultra Sharp Transition-Band LPF with Miniaturized Size for GSM Applications

“…Also, this filter presents a slow transition-band and the limited stop-band. In [10], a microstrip LPF with acceptable stop-band width using T-shaped resonators was reported, but the circuit dimensions are large. To develop the stop-band of the low-pass filter in [11], improved hairpin resonators were adopted; nonetheless the transition-band is slow.…”