Analog Circuit Design Volume 2

Chapter 29

Low cost coupling methods for RF power detectors replace directional couplers

Shuley Nakamura and Vladimir Dvorkin

Introduction

Minimizing size and cost is crucial in wireless applications such as cellular telephones. The key components in a typical GSM cellular telephone RF transmit channel consist of an RF power amplifier, power controller, directional coupler and diplexer. Some of the more recent RF power amplifiers incorporate a directional coupler in their module, reducing component count and board area. Most power amplifiers, however, require an external directional coupler. Unfortunately, directional couplers come at a price and sometimes a performance loss. While cost is an issue, long lead-time and wide variations in coupling ...