Slipstream Design

Slipstream Design Successfully Develops a Doherty Amplifier Using NI AWR Software
Microwave Office software is an invaluable tool that enables us to deliver products according to our flexible and responsive business model. We use the software in all stages of product development, from providing confidence in quoting to detailed and in-depth modeling (both nonlinear and EM) through the final delivery phase.
Dr. Michael Roberts
Technical Director
Slipstream Design

Slipstream Design Successfully Innovates a Modified Three-Level Doherty Amplifier Using NI AWR Software

Company Profile

Founded in 2011 and based in the UK, Slipstream Engineering Design Ltd is a growing design firm with a strong customer base of major original equipment manufacturers who rely on the company’s hands-on and flexible approach. Slipstream Design leads the way in innovative wireless and digital product development for applications including radar. The company’s high-speed, high-frequency designers are passionate about RF and digital technology and specialize in the development and test of sub-systems for the aerospace, communications, and security industries. The main areas of focus lie in RF and microwave design up to 60 GHz, high-speed field-programmable gate array (FPGA) design, and embedded system design.

The Design Challenge

Slipstream Design engineers were responsible for the design of a complex, modified three-level Doherty power amplifier (PA) for use in security-related counter-terrorism equipment. Modern communication systems routinely use complex modulation techniques that result in peak-to-average ratio (PAR) signals of 9 dB and higher. To achieve sufficient linearity, these high PAR levels require a PA to operate far below the power levels that would yield optimum power-added efficiency (PAE). The Slipstream Design PA had large-signal dynamic load-pull effects that had to be carefully modeled prior to fabrication and it was important to balance the PA performance to operate optimally at both high- and low-power levels. The project had a tight design schedule and pressure to deliver a right-the-first-time prototype.

The Solution

The Slipstream Design team chose NI AWR Design Environment, specifically Microwave Office circuit design software, for its innovative three-stage Doherty PA design due to the software’s superior nonlinear large-signal harmonic balance technology. For the initial design, the team used small-signal S-parameters to obtain an approximate design solution. As the design developed, it was important to understand, in detail, the large-signal performance as it related to terminating load impedance, a key factor in determining Doherty PA operation. Using the large-signal modeling tools in Microwave Office, the team was able to implement the entire RF layout and simulate the full amplifier prior to committing to the printed circuit board (PCB).

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