12GHz LO

Analog Devices has some great chips that make life for us SHF amateurs much easier. After the design of a /1000 prescaler up to 13GHz and up, I have now designed a simple 10.5-12.5 GHz local oscillator. Here you see a picture of the test setup. The VCO is programmed for 11772 MHz, times four gives a test signal on 47GHz:

This LO uses a HMC515 from AD. This is the chip on the right on the PCB. A little hard to mount, solder a few pins, then solder the pad on the ground side to fixate it. Or, maybe better, use paste and flux. This VCO runs from 10.5 to 12.5 GHz with a tuning voltage of 0 to 13V.

The tuning voltage is acquired in a PLL using a ADF4113HV PLL, also from AD. The HV indicates the tuning voltage can be up to 13V. The HMC515 has apart from the main RF output also outputs for RF/2 and RF/4. The latter is used, so spans the frequency roughly from 2.5 to 3.5 GHz. The ADF4113 is able to process signals up to 4 GHz. The reference frequency is generated by a (very tiny) 40MHz TCXO ASTX-13-C-40.000MHz. Of course it is possible to use in stead a 10MHz from a GPSDO in the shack. The PLL is programmed by an ATTINY13A, which in turn can be programmed in circuit. The software currently assumes an Fref of 40MHz and and Frf of 2943 MHz. If other frequencies are wanted you need to change the firmware appropriately. For further details, see the schematics:

I used KiCad to draw the schematic and to design the PCB. The PCB fits in a standard tin box of size 74x35mm:

The project files can be found at github/pe1jpd.