X-band balanced power amplifier using novel coupler with 50% power-added efficiency

In this paper, we demonstrate an X-band balanced power amplifier using a no vel microstrip line dc blocking impedance-transforming branch-line coupler (DCITBC). This novel coupler has the function of dc blocking, which can eas ily cascade two stages of an active circuit together. Therefore, we can red uce the cost and the circuit size. The measured power-added efficiency of t his balanced power amplifier is 50% over the 9.8-10.2 GHz band, with an ass ociated gain of 9 dB and 25 dBm output power. Additional important results are the superior performance of the harmonic suppression; the measured resu lt shows a second harmonic below -40 dBc without an extra harmonic rejector . (C) 1999 John Wiley & Sons, Inc.