Microwave synthesizer subsystem

The development of the 5G system, software-defined radio or Radio-over-Fiber solutions necessitates the availability of small, cost-effective, programmable microwave and millimeter wave signal sources. This paper presents a subsystem of a microwave synthesizer at the frequency band around 9GHz. The circuits were designed and built in a microstrip structure. The subsystem comprises a voltage-controlled oscillator (VCO) around 3GHz, an analog frequency tripler, a bandpass filter (BPF) and amplifier. A lowpass filter (LPF) and a Wilkinson power divider were also built in the 3GHz band to enable feedback of the oscillator output for later stabilization. The subsystem is usable in a 900MHz band at 9GHz.