Six-port technology for MIMO and cognitive radio receiver applications

Six-port technique is a very accurate and cost effective method to determine the amplitude and phase of any input signal with respect to a known signal using only power or voltage measurements. This property of six-port technique has been variously exploited in a number of RF (radio frequency) and microwave applications. The present paper provides a very brief but wide review of the six-port technique for communication receiver applications. After providing a basic theory of six-port technique for single-band receiver application, the paper shows the usefulness of the technique for multi-band, MIMO (multiple-input and multiple-output) and CR (cognitive radio) receiver applications.