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A T-shaped feed based differential microstrip bandpass filter (BPF) with high commonmode (CM) rejection ratio is presented. The filter comprises two magnetically coupled conventional square open-loop resonators (SOLRs), with capacitive coupled T-shaped input-output (I/O). The choice of the T-shaped I/O coupling feed enables a higher common-mode suppression of −57 dB at f d 0 that extends up to 4.1f d 0 with a value better than −30 dB. Frequency f d 0 is the cutoff frequency of the differential-mode (DM) passband. Moreover, this feed can symmetrically position two transmission zeros (TZs) at the upper and lower stopbands. This yields a highly selective and compact filter. Additionally, a T-shaped feed only excites the odd mode of the filter resulting in a wide stopband with high out of band rejection. The upper and stopband rejection of the filter is better than −50 dB. To demonstrate the design, DM and CM lumped models of the filter are proposed and studied. The filter operates at 1.263 GHz with a fractional bandwidth (FBW) of 3.9%. The design is validated experimentally by characterizing DM, CM, common-mode to differential-mode (CD), and differential-mode to common mode (DC). Moreover, the group delay (GD) response of the filter is measured, and a significantly flat response is observed with a maximum delay variation of only 0.88 ns in the 3 dB bandwidth.

A tunable 10-stage all-pole (Papoulis) low-pass filter occupying 0.1815mm2 is designed and integrated as a building block in a 22nm CMOS FDSOI receiver for the 5G. Each filter stage comprises of a two-stage unity gain buffer with common mode feedback loop. Tunable resistors between each stage determine the bandwidth of the filter in the range of 0.7 GHz to 1.5 GHz. An identical filter structure, but with the outputs fed back to the inputs functions as an oscillator. Correlating the oscillation frequency with the filter bandwidth, under the same tuning conditions, the filter bandwidth can be calibrated to account for PVT variations. Measurement results show an in-band OIP3 of 8.8dBm and a nearly linear phase response at a power consumption of 35mW to 50mW from a 1V supply. The power/pole of 3.3mW/GHz is the best when compared to other filters from literature.

In this letter, a tuning fork shaped, differential dipole antenna, with two floating reflectors, is presented. The dipole antenna resonates at 1.22 GHz and has a fractional bandwidth (FBW) of 16.39% and a differential impedance of 100 Ω. The proposed antenna is composed of quarter wavelength tuning fork shaped dipole arms in the top layer. To improve robustness, while connecting to the differential circuits, two floating reflectors are used on the bottom layer, beneath the dipole arm. This method helps improving the gain by 7%. A microstrip-to-coplanar strip line (CPS) transition is designed to measure the stand-alone differential antenna. The measured gain and efficiency of the antenna are 2.14 dBi and 84%, respectively, at the resonant frequency. The possible targeted applications are circuits with differential inputs/outputs, like energy harvesting circuits, radio frequency tags, wireless communications and any other wireless sensor network nodes. Details of the design along with simulated and experimental results are presented and discussed.