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This study presents a new low-voltage and low-power, mixed-mode, universal Gm-C filter capable of generating simultaneous filtering outputs. The proposed circuit employs only 19 inverters as operational transconductance amplifiers, and 2 grounded capacitors in carbon nanotube field-effect transistor (CNTFET) technology. However, due to the proper use of subthreshold transistors biased at ±0.25 V supply, the power consumption of the proposed circuit is reduced effectively. Furthermore, as the HSPICE simulation results show, the proposed filter consumes only 11.66 µW of power, while its total harmonic distortion is obtained −55.4 dB at 100 MHz centre frequency. Moreover, the input referred noise values at 100 MHz are reduced to 11.57 nV/ Hz and 760 fA Hz in voltage and current modes, respectively.

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This study aimed to design and fabricate a lowpass‐bandpass (LP‐BP) diplexer with high isolation for telecommunication applications including wireless communications. The results revealed that the −3 dB cutoff frequency of the lowpass filter (LPF) was equal to 0.82 GHz. The advantages of the LPF section include a very high suppression factor (SF) parameter (about 4.4), very sharp roll‐off‐rate (ROF or ζ) parameter (687), and a very high figure of merit (FOM) (about 233491). The bandpass filter (BPF) section was designed applying dual‐mode resonators with triband. The central frequencies of these tribands were equal to 2.38, 3.93, and 5.65 GHz. In the following, an SMV‐1247‐079LF SMD varactor diode is used to adjust the proposed LPF. The tuning range for the proposed LPF is 0.3‐0.72 GHz. In the proposed diplexer, the isolation between the output ports was higher than 45 dB. The results of measurements were in good agreement with those of the simulation.

Summary This paper presents a dual‐mode tunable bandpass filter (BPF) for global system for mobile communication, universal mobile telecommunications system, wireless fidelity, and worldwide interoperability for microwave access standard applications. The proposed filter consists of a stepped‐impedance resonator, single resonator, and coupled line, which are loaded with varactors. The center frequency and bandwidth of the proposed filter can be tuned with tuning varactors. Furthermore, the measurement results show that the BPF can be tuned over the frequency range of 1.8 to 2.5 GHz. Moreover, the bandwidth can be changed at each certain frequency. Furthermore, using PIN diodes, a bandstop filter is added to the tunable BPF to reduce the out‐of‐band frequencies around the desired frequencies. The values of LC equivalent circuits are calculated, and the results are compared with those obtained from the layout of the proposed structure. Finally, the measurement results justify the simulation results.

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