Probe-fed circularly polarized (CP) patch antennas using relatively thick substrates often exhibit significant inductive reactance, which is difficult to compensate using conventional feed-position adjustment. This letter investigates the effect of orthogonal feed displacement on the input impedance characteristics of such antennas. A modal interpretation and equivalent circuit model are used to explain the proposed mechanism. An X-band CP patch antenna operating at 8.483 GHz was designed, fabricated, and measured on a substrate with a thickness of approximately 0.044λ₀. Simulations and measurements indicate that the proposed feed adjustment can improve impedance matching while maintaining CP operation.

This letter presents a CMOS-based reversed Doherty power amplifier with a compact resonant peaking-path combiner for improved back-off efficiency and reduced passive area. In the proposed topology, the carrier branch is connected to the combining node, whereas the auxiliary branch employs a π-type resonant network that realizes the combining and impedance-inverting functions. This preserves Doherty load modulation while minimizing the effects of the quarter-wave inverter losses in the carrier path. Designed at 1 GHz in 180 nm CMOS, the amplifier achieves 34 dBm maximum output power, 36.3% peak PAE, and 26.2% PAE at 6 dB output back-off, demonstrating a compact solution for RF transmitters.

This letter describes a low jitter PAM4 receiver for high-speed very-short-reach application, where the decision feedback equalizer and the PAM4 decoder are merged together to reduce the duty cycle distortion (DCD) jitter of the decoded MSB and LSB signals. To alleviate timing constraints and reduce the output jitter, a modified double-tail (DT) slicer is applied. The post-layout simulation results in 28 nm CMOS technology indicated that our designed receiver can successfully recover and decode 56 Gb/s PAM4 signal for a channel with 12.5 dB@14 GHz insertion loss with a power efficiency of 1.93 pJ/bit. The peak-to-peak jitters of the restored MSB and LSB signals are 1.6 and 1.8 ps, respectively.

This letter presents an analysis of the toroidal-core energy (TCE) harvester that draws power from the near-field of a UHF leaky-feeder communication cable to supply ultra-low-power IoT sensor nodes deployed inside underground tunnels. The NiZn ferrite toroid (R_i = 38 mm, R₀ = 63 mm, height = 25 mm, μ_i= 700, N = 7 turns) is coupled inductively to an RLK78-50JFNA leaky-feeder cable resonating at f₀ = 416.5 MHz, the center of the 411–422 MHz operating sub-band. Full-wave simulations performed in CST Microwave Studio are experimentally validated with a 24 W UHF transmitter that establishes an in-tunnel near-field along the cable, and the harvester delivers V_AC = 6.83 V and I_AC = 71.4 mA at resonance under the 1 W simulation reference power, corresponding to an AC power-conversion efficiency of 48.8%. A two-stage HSMS-285P Schottky voltage doubler followed by a commercial RFD199A-PCB RF-DC converter regulates the output to 4.7 V DC, sufficient to power low-duty-cycle sensor nodes. A linear post-processing methodology is introduced to reconcile CST’s 1 W port-power normalization with the parametric input-power sweep required for experimental verification, enabling rapid design exploration without re-running the solver. To the best of the authors’ knowledge, the proposed harvester is the first reported device to exploit the UHF leakage from a slotted radiating coaxial cable as a stationary power source for in-tunnel IoT applications.