Abstract
The load modulated balanced amplifier (LMBA) technique uses a control signal, injected at the output coupler, to modulate the impedance of the balanced amplifier transistors. A 14.1-W X-band LMBA is reported, integrating for the first time the balanced, driver, and control signal amplifiers in a single microwave monolithic integrated circuit. Load modulation and bias settings are used to demonstrate that high circuit efficiency can be achieved as the LMBA is adjusted for operation in three RF-power regimes; 1.5, 5.6, and 14.1 W for a constant input power of 22 dBm. Power-added efficiencies above 37% are observed in all power regimes from 8 to 9 GHz under saturated conditions.
Highlights
P OWER amplifier efficiency is a critical parameter for all applications
Large-signal measurements for the control signal power (CSP) amplifier were performed using signals injected only at the CSP input and with the balanced and driver amplifiers zero biased (i.e., 0 V on the drain and gate). These measurements serve as a calibration for the CSP amplifier characteristics and allow for the balanced amplifier power, and drain efficiencies (DEs) to be extracted from load modulated balanced amplifier (LMBA) measurements
This letter has for the first time reported a demonstration of an X-band LMBA microwave monolithic integrated circuit (MMIC)
Summary
P OWER amplifier efficiency is a critical parameter for all applications. Maintaining efficiency as the outputpower requirement changes has been the subject of many inventions and papers. A new technique, the load modulated balanced amplifier (LMBA) has been proposed and demonstrated [3]. In this technique, the output impedance seen by the transistors of a balanced amplifier is modulated using a control signal power (CSP) injected at the isolated port of the output coupler. An X-band LMBA in microwave monolithic integrated circuit (MMIC) technology is demonstrated for the first time. This MMIC was designed for specific applications which require discrete, rather than continuous, switched power levels with maximum efficiency
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