Bandwidth and Efficiency Improvements in Cascaded Single-Stage Distributed Amplifier

This paper first demonstrates the viability of the cascaded single-stage distributed amplifier (CSSDA) implementation using discrete packaged HJ-FET devices. The design is shown to provide superior performance in terms of available power gain than conventional distributed amplifiers (CDA) using the same number of active devices. Next modifications to CSSDA design by employing reactive terminations is shown to render the amplifier suitable for large-signal operation, and this significantly improves the amplifiers overall performance. The novel distributed amplifier implemented using DHEMPT devices achieved an associated gain above 26 dB with flatness of < 0.5 dB, an average PAE in access of 27% at an output power of 25 dBm over a multioctave bandwidth of 2-18 GHz with an efficiency peak of 30% at 12 GHz. The CSSDA is suitable for digital optical communication and pulse applications.