A Narrow Band HighResolution Synthesizer using a Direct Digital Synthesizer Followed by Repeated Dividing and Mixing
2010
A synthesizer is described that generates a narrow band offrequencies around 10 MHz with extremely small step size and high spectral purity. A DDS running at 667 kHz is upconverted to 10.667 MHz and divided back to 667 kHz several times to improve the resolution and spurious suppression of the DDS. The final 10.667 MHz offset frequency is then mixed with 667 kHz resulting in a 10 MHz output. The post mixerfiltering is done with inexpensive 10.7 MHz ceramic filters of the type used in FM broadcast receivers.