RFE has designed a reliable, fast-tuning, multi-octave microwave source with the smallest possible footprint and least weight. The design uses commercial, off-the-shelf, surface-mount components—VCOs, pre-scalars, amplifiers, filters and synthesizers—to shrink size, eliminate hand tuning and minimize the parts count. The result is a low-cost, lightweight, integrated module that performs in the harshest environments.
The RFE synthesizer covers the entire 0.1 to 20 GHz spectrum in 1 MHz steps, using a 10 MHz external reference. Output power is between 10 and 15 dBm, with a flatness of 1 dB. Phase noise is −65 dBc/Hz at 10 kHz offset and −100 dBc/Hz at 100 kHz offset, with spurious signals −50 dBc or better inside a ±10 MHz offset and −60 dBc elsewhere. Harmonics are no greater than −15 dBc. In 100 µsecs, the synthesizer tunes to within ±1 MHz of the final frequency. The unit has a single SMA output and a micro D-25 connector for bias and control, which allows parallel or serial control. The synthesizer is biased with +15, -5 and +5 V supplies and consumes a total DC power of 7.5 W. It can be packaged in several form factors, including low profile and hermetic.
The design uses two synthesizer ICs, one to cover 0.1 to 1.6 GHz, the other for 1.6 to 20 GHz. Signals in the 0.1 to 1.6 GHz band are produced using the Analog Devices AD4351 wideband synthesizer. Higher frequency signals are generated using a 10 to 20 GHz VCO, a divider and an Analog Devices AD4157 fractional N frequency synthesizer. The 1.6 to 10 GHz band uses a programmable pre-scalar and, to maintain harmonic performance, the band is separated into five sub-bands using a switched filter network.