Microwave frequency synthesizer with ultra-fast frequency settling and very high frequency resolution

摘要

The ability to achieve ultra-fast frequency settling times with good frequency resolution and high absolute accuracy over significant bandwidth at microwave frequencies ranging over three octaves. The implementation is an open-loop system requiring little or no compensation of temperature. This is accomplished by providing a frequency doubled direct digital synthesizer output to up/down convert a microwave frequency source. A special tracking filter architecture coupled to the microwave source provides the suppression of unwanted products. Fixed frequency set-on and swept bandwidths in excess of 300 MHz have been demonstrated. This is accomplished by using a direct digitally synthesized quadrature phased carrier which can be set to any frequency within a 350 MHz bandwidth to coherently up/down convert a low phase- noise microwave frequency to the sum or the difference frequency product. Individual control of differential phase and amplitude over frequency assures very high suppression of unwanted products without the use of additional filtering.