Single and dual input packaged 5.5–6.5GHz, 20W, Quasi-MMIC GaN-HEMT Doherty Power Amplifier

Abstract

This paper presents the design, the realization and the power characteristics of plastic low cost packaged symmetric Doherty Power Amplifiers (DPA) operating in the 5.5–6.5GHz bandwidth. A single input (SI-DPA) and a dual input (DI-DPA) DPAs are proposed based on two power bars composed of two GaN HEMT cells (8 fingers of 275μm unit gate width). Input and output matching networks are designed on passive GaAs MMIC technology. To our knowledge, it is the first published SI and DI-DPAs working in C band, designed using Quasi-MMIC technology and assembled in plastic package. The measured power results under Continuous Wave (CW) signal of the SI-DPA demonstrate a maximum output power (Pout) upper than 20W (43.5dBm) with 50% drain efficiency (dE), 42% power added efficiency (PAE), 11dB of insertion gain (GI) in the 5.5–6.5GHz bandwidth. At 6dB output power Back-off (oBo), the drain efficiency is greater than 35% (32% PAE). The DPA linearity has been investigated with a 256QAM modulation signal of 30MHz bandwidth and using Digital Pre-Distortion (DPD) leading to a 50dBc Adjacent Channel Leakage Ratio (ACLR) at a 34 dBm average output power. The designed DI-DPA is identical to the SI-DPA without input power splitter. It demonstrates that the adjustment of power ratio between the main and the peak amplifiers associated with adequate bias points, improves all the power performances: linearity, PAE, oBo and GI. The DI-DPA reaches a 12.5 dB GI, a maximum Pout equal to 44dBm (3.5dB gain compression) with 45% PAE. Moreover, in the same previous bandwidth, 40% PAE with 4° of AM/PM variation are obtained at 6dBoBo and 36% PAE (AM/PM=3°) at 8dBoBo.