This device is intended as a reference for a later to be build Arduino / Genuino Shield 6.8 GHz Synthesiser based on the ADF4356. As the HMC1031 can handle an input range of 100 mVpp up to 3.5 Vpp, the 10 MHz is limited with two antiparallel diodes (BAV99). It is then ac coupled to pin 2 of the pll.

The master oscillator is a Ultra Low Phase Noise VCXO from ABLNO (ABLNO-V-100.000MHz-T2) running at 100 MHz and promising a phase noise of (typical) -160 dBc/Hz at 10 kHz offset. The output is buffered / amplified by a GALI-6F+.

The loopfilter is taken from the schematics of the evaluation board. Use only NP0 capacitors for that ! We must confess, that our calculator for loopfilters is unable to handle that small currents of ± 50 µA.

There are two ldo voltage regulators with very large capacitors at the output to ensure low noise and stability.

The circuit consumes 100 mA when powered with + 7 V. Output power level is + 12 dBm.

The performace is similiar to commercial devices. Once more it must be noted, that the 10 MHz used to lock this thing must be of the best possible quality. What ever garbage rides on the 10 MHz can be seen in the output - multiplied by ten !

As cmos oscillators are rich in harmonics it is also possible to filter out one of them, maybe to clock a dds or as a (clean) lo source.

Check the availability of the voltage regulators first. It looks like they are already obsolete !

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