ABSTRACT
This chapter gives the design methods for couplers and reflectometers and radio frequency (RF) power sensors. Directional couplers are a critical device in RF amplifiers and used widely as a sampling device for measuring forward and reflected power based on the magnitude of the reflection coefficient. It can be implemented as a planar device using transmission lines such as microstrip and stripline or lumped elements with transformers based on the frequency of operation. Three-line, six-port microstrip directional couplers can be used for several purposes in RF applications including voltage, current, impedance, and voltage standing wave ratio (VSWR) measurements. As a result, six-port microstrip directional couplers are cost-effective alternatives to existing reflectometers. The magnitude and phase detection in the RF power sensor can be done with an integrated circuit (IC), which has two six-stage logarithmic amplifiers, a magnitude comparator, and a phase discriminator to measure the relative magnitude and phase between two input signals.
