Design and evaluation of a low-cost X-band synthesizer for LMDS applications

Inspired by the availability of the low-cost, high performance L-Band synthesizers and X-Band dividers, the design and performance of a low-cost X-Band synthesizer is evaluated. The X-Band synthesizer is designed for LMDS base station applications below 25GHz with high stability requirements, lower level modulation schemes and higher modulation rates. The X-Band VCO is an MHMIC design using the NEC321000 chip as its active element, with a low-cost printed spiral inductor to form the resonator and resistive buffering at its output. The L-Band synthesizer can be any off-the-shelf low-cost device. The reference frequency is obtained from a low-cost 10MHz TCVCXO.; The phase noise performance of the built synthesizer is evaluated in terms of the residual signal to noise ratio at the demodulator input. Link margin degradation due to synthesizer phase noise is then calculated for lower modulation schemes and higher symbol rates.