Low Noise High-Gain Distributed Preamplifiers Using Cascaded Single Stage Distributed Amplifier Configurations

In this paper 2–10 GHz hybrid-distributed preamplifiers using two and three cascaded single stage distributed amplifiers are demonstrated. These amplifiers produce available power gains significantly higher than conventional distributed preamplifiers using the same number of active devices. Simulation results show the advantage of the proposed preamplifier over the conventional one. Measured results of the two realised configurations of preamplifiers using two and three cascaded single stage distributed amplifiers are presented. Each configuration shows that the available power gain can be increased by increasing interstage characteristic impedance of the cascaded single stage distributed amplifiers. The measured available power gain for two stages shows an improvement from 18 dB to 20 dB, and for three stages an improvement from 26 dB to 31 dB across the 2–10 GHz frequency band, as the inter-stage characteristic impedance is increased from low to high level. Input and output return losses better than −10 dB, and input-output isolation better than −55 dB at the beginning of the band and better than −45 dB at the end are achieved. This approach also provides a good measured noise figure performance of an average of 4 dB across the 2–10 GHz frequency band for both two and three cascaded stages. The group delay of both cascaded amplifiers are measured. Its flat performance proves the viability of this approach which is suitable for digital optical communication and pulse applications. key words: distributed ampli ers, gains, noise gure and group