Investigation into the use of high-efficiency, switched-mode Class E power amplifiers for high-dynamic range, pulse-mode applications

In typical communication and radar systems, the transmitter is operated in either a continuous wave or a pulsed mode where the transmitter is periodically turned on for a portion of time. These systems commonly use a power amplifier in the transmitter to raise the power level of the transmitted signal to a value sufficient to meet system sensitivity requirements. In high-dynamic range systems, the power amplifier pulse must turn off at a rate compatible with the system noise floor at the receive time. Some high-dynamic range systems are sensitive to signals greater than 120 dB below the transmit power level, and correlated energy that exists during the receive time can cause serious system consequences.;The Class E high-efficiency power amplifier is an attractive candidate for pulse-mode systems, but it is unknown if the pulse profile characteristics are compatible with the stringent requirements of these systems. It is shown that the Class E amplifier mode allows generating a high-isolation pulsed signal simply by pulsing the input radio frequency (RF) signal. The unique properties of the switched-mode amplifier cause it to be off when it is not driven.;A technique to characterize the pulse profile of an RF amplifier over a very wide dynamic range under fast-pulsing conditions is presented. A pulse modulated transmitter is used to drive a device under test with a phase coded signal coupled with a correlation technique that allows for an increased measurement range beyond standard techniques. A measurement receiver is described that samples points on the output pulse power profile and performs the necessary signal processing and coherent pulse integration, improving the detectability of low-power signals. A full measurement dynamic range of greater than 160 dB is achieved, extending the current state of the art in pulse profiling techniques. The pulse profiles of example Class E amplifiers are examined and compared to the results for the same amplifiers operating in a linear mode. It is discovered that the inherent trapping properties of the active device technology limit the usefulness of these specific amplifiers in a high-dynamic range pulsed system.