Design and fabrication of a continuous tunable microstrip lowpass filter with wide stopband and sharp response

Abstract

Tunable microstrip lowpass filters (LPFs) with a good performance are used in most telecommunication systems. In this article, a third‐order circuit with stepped impedance resonator is used to design LPF, and suppression cells are used to improve the performance of the filter in stopbands up to 20 GHz. The −3 dB cut‐off frequency can be controlled in the range of 0.35 to 1 GHz with the tuning range of 96%. Rejection stopbands of 30 dB (type‐I) and 20 dB (type‐II) can be extended to more than 20 GHz. For the passband, the insertion loss variations are in the range of 0.35 to 2.12 dB. The proposed tunable LPF has a sharp roll‐off rate (42‐96 dB/GHz). The varactor‐tuned microstrip LPF is designed, simulated, fabricated, and measured. The results of simulation and measurement for the proposed LPF are in good agreement. The size of the proposed tunable LPF is small and the filter dimensions are equal to 0.267λg × 0.13λg.

A compact filtering power divider with low‐pass response and wide harmonic suppression

“…The Wilkinson power divider has various applications in microwave systems, such as in wireless connections and radar communication. The lowpass filter (LPF) rejects the high frequency and spurious signals in communication systems 1,2 . The power divider and LPF are the two passive components which can be integrated, forming a filtering power divider (FPD) that acts like a single and more efficient device.…”

“…The lowpass filter (LPF) rejects the high frequency and spurious signals in communication systems. 1,2 The power divider and LPF are the two passive components which can be integrated, forming a filtering power divider (FPD) that acts like a single and more efficient device. Earlier, in conventional structures, they were designed individually and then connected to a quarter-wavelength transmission line, leading to counterfeit frequencies and large circuit size.…”

Modified Wilkinson power divider with harmonics suppression and compact size for GSM applications

“…Radio frequency (RF)/microwave power dividers with good properties such as wide stopband, compact size, high suppression factor (SF), high isolation between output ports, and simple structure are widely used in modern wireless communication systems for dividing the input signal into two or more signals. Nowadays, filters 1–10 and power dividers 11–25 are widely used in microwave systems such as power amplifiers, mixers, and feeding network in an antenna array, because they are easily designed and fabricated with other microwave devices. In Reference 1, a compact low‐pass filter (LPF) with wide stopband using stepped impedance and open stubs is presented.…”

“…Nowadays, filters 1–10 and power dividers 11–25 are widely used in microwave systems such as power amplifiers, mixers, and feeding network in an antenna array, because they are easily designed and fabricated with other microwave devices. In Reference 1, a compact low‐pass filter (LPF) with wide stopband using stepped impedance and open stubs is presented. In References 2 and 3, an LPF with a sharp roll‐off rate (ROF) and wide stopband is presented.…”

Compact tunable U-Hi-Lo low pass filter using quasi C-shaped stubs

“…One of the most important component in the reconfigurable wireless communication systems is the low pass filter since it posses larger operating band, wide rejection band, low pass-band loss, sharp roll-off rate, in addition to its compactness in size [18]. The tunability of the LPF can be achieved by using various RF components such as varactor diode [18][19][20][21][22][23], lumped capacitors [24], MEMS switches [25], PIN diodes [26], and piezoelectric transducer [27].…”