Balanced RF Power Amplifier Design in Horizontal Current Bipolar Transistor (HCBT) Technology

The paper presents a balanced RF power amplifier designed by using Horizontal Current Bipolar Transistors (HCBT). The near-50-Ω large-signal input and output impedances of HCBT are exploited to achieve wideband operation. Matching and bias networks are designed in microstrip technology and the optimization is performed using electromagnetic simulator. Signal splitting and combining is achieved by microstrip double-box branchline hybrid couplers, which are optimized for wide bandwidth and high return loss. Bias lines are implemented as quarter-wavelength short-circuited shunt stubs, which provide short circuit for even harmonics and open circuit for the fundamental frequency over the entire operating bandwidth. The amplifier is implemented on a low-cost 1-mm-thick FR4 substrate. At 1-dB compression point, the amplifier exhibits 21.4 dBm output power and 10.4 dB gain in the frequency range from 1.8 GHz to 2.5 GHz, with input and output return losses higher than 20 dB while using pure-silicon HCBT technology.