We design a photonic terahertz (THz) antenna operating in the 275–296 GHz band, integrating two identical modified uni-traveling-carrier photodiodes (MUTC-PDs), two impedance matching networks, a Wilkinson power combiner and a Vivaldi antenna. Simulation results show a saturated output power of 1.58 dBm at 280 GHz, achieving a 4.13× power enhancement through optimized impedance and power combining compared to a standalone device. The integrated antenna achieves a peak gain of 7.93 dBi, with reflection coefficients below −10 dB. The system demonstrates a power combining efficiency exceeding 95% for phase imbalances up to 20°, and the Wilkinson combiner exhibits only 0.76 dB insertion loss at 285 GHz, demonstrating high radiation and combining efficiency in the 275–296 GHz band.

This paper proposes a dual-side hybrid embedding network (DHEN) to mitigate gain degradation in terahertz amplifiers at frequencies near $f_{\max }$. The proposed approach employs a pre-embedding network for parasitic absorption, followed by Y-embedding for gain enhancement. A theoretical analysis is conducted to derive the embedding conditions for process-constrained circuit synthesis. In this architecture, a capacitive base-side pre-embedding provides intrinsic DC isolation, while a defected-ground-structure (DGS) inductor realizes the Y-embedding inductive element with reduced layout area. Based on the DHEN, a four-stage amplifier is designed in a 130 nm SiGe BiCMOS process. Electromagnetic co-simulation results demonstrate a power gain of 19.3 dB at 280 GHz, corresponding to an 11.5 dB improvement over a conventional unboosted amplifier. The proposed approach provides a unified synthesis methodology that simultaneously addresses parasitic absorption, DC isolation, and gain enhancement for near-$f_{max}$ THz amplifier design.

This study investigates trellis shaping (TS) for mitigating nonlinear impairments in photonic terahertz (THz) communication systems. A parallel shaping architecture integrating hierarchical modulation (HM) with adjustable power allocation is proposed. The scheme applies TS to structure the data stream hierarchically and employs superposition coding (SC) to generate non-uniformly distributed TS-16QAM signals, enhancing transmission performance. Experimental validation over a 5-m link at 320 GHz demonstrates that the proposed scheme achieves a 1.65 dB improvement in input power sensitivity and a 1.39 dB gain in Q-factor compared to the Maxwell–Boltzmann (MB) distribution. Furthermore, the system provides enhanced power allocation flexibility, expanding the tunable range of the hierarchical power ratio by a factor of 1.37.