Wideband local oscillator design for wideband transceivers

The wideband transceivers like the software defined radio require designing wideband RF hardware covering octave bands. The local oscillator of the mixer should be a wideband frequency synthesizer. Building on the theory of oscillations in the voltage controlled oscillator, the paper reviews the concept of negative resistance in the transistor circuit with some base inductance. It also provides simulation of this concept. To apply the theory and simulation, the actual VCO hardware was designed and fabricated for the range covering 1200 to 2400 MHz. These VCOs were used in the design of wideband PLL frequency synthesizer. The results including very good phase noise performance are presented. This approach can be used to design wideband synthesizers in other RF range.