An X-band GaN PA MMIC for phased array radar applications

June 29, 2017 //By Stuart Glynn and Liam Devlin, Plextek RFI
Active phased array radars require numerous power amplifiers (PAs), which must be small, efficient and low-cost. This article describes an X-band PA MMIC that covers 9 to 11.5 GHz and satisfies these requirements. It has an output power of 7W (38.5 dBm) from a 29 dBm drive with a Power Added Efficiency (PAE) of 42%.

The design was realized on the 0.25µm gate length GaN on SiC process of UMS (GH25) using Keysight’s ADS 2015. The die size is just 1.5-mm x 2-mm, which means around 2300 PAs can be fabricated on a single 4” diameter wafer.

 

Introduction

Phased array radars use many transmitters operating in parallel to generate a high total transmitted RF power level. The RF amplifier at the output of each transmitter must be capable of generating the required RF power efficiently, and at an acceptable cost. The elements must be closely spaced (normally around a half wavelength separation) and this requirement, coupled with the potentially huge level of total dissipated power, can represent enormous challenges for the radar design team. The PA is normally the key contributor to the power dissipation, so a component with high efficiency is very desirable.

Typical RF power levels required from each transmitting element are in the range 5W to 10W. GaN technology can realise such power levels with ease and can do so with high efficiency. The amplifier described here was designed such that the output stage would have adequate gain to allow the input drive to be provided by readily-available COTS technology. The target performance requirements for the amplifier are listed in Table 1.


Table 1: Target Performance Requirements for
the PA.

Design category: