This paper presents GaN-based power amplifier integrated circuits targeting D-band frequencies. Two chips have been realized, using transistors with a gate length of 100 nm and 70 nm. On-wafer S-Parameter measurements of the designed GaN MMICs yields a high linear-gain of more than 20 dB and 25 dB at 130 GHz, respectively. Performed large-signal measurements of assembled samples demonstrated a saturated output power of 21.9 dBm (150 mW) for the 100 nm MMIC, along with a maximum PAE of 8.8 % at 140 GHz. Assembled 70 nm MMICs yield an improved large-signal performance of 23.1 dBm (200 mW) and more than 11.2 % PAE. Based on the power amplifier integrated circuits with the longer gate-length, a compact split-block module with waveguide flanges has been fabricated. The assembled module has been characterized between 130-150 GHz, demonstrating a typical linear-gain of 19 dB (±3 dB within the frequency band), along with more than 18 dBm (60 mW).

In this letter, we report on the realization of a two-stage 16-way solid-state power amplifier (SSPA) in the Ka-band. To this end, we describe the design of a high-power amplifier (HPA) in a 100-nm gallium nitride (GaN) process and its integration into a split-block waveguide module. The PA module achieves an output power of more than 7.6 W between 28 and 39 GHz. In conjunction with 16 of these PA modules, we then employed a custom low-loss radial splitter and combiner to create a compact SSPA system. The two-stage SSPA configuration exhibits a small-signal gain of up to 44 dB and a peak output power of 127 W at 31 GHz in 5 dB of gain compression. Furthermore, we measured output power of close to 100 W and state-of-the-art efficiency values of more than 19% between 28 and 38 GHz. To our knowledge, this is the most broadband high-power SSPA demonstrated so far in this frequency range.

In this paper, a broadband Sequential Power Amplifier (SPA) is designed and realized for the use in an active MIMO antenna around 3.5 GHz. For that purpose, specifications for the individual components are derived to yield optimum performance of the complete SPA when amplifying a mobile communication signal. In order to meet the size requirements of an active antenna, amplifier modules that include all necessary transformation and stabilization networks inside the package are developed. The SPA achieves a bandwidth of more than 1 GHz (RBW of 28%) and shows a peak drain efficiency of 47% in 8 dB backoff at 3.5 GHz. To transmit a complex signal such as QAM using the SPA, its two inputs have to be driven according to the system's characteristic curve. For the first time, modified constellation diagrams for each input have been derived to transmit a 16-QAM-modulated test signal with 10 MBaud at 3.2 GHz. For the amplification of this signal, the system shows an increase in drain efficiency of 10 %-points compared to a conventional class-B PA.