Hello,

I'm looking to use the HMC832 in the Exact Frequency Mode to generate the frequencies listed below. I would like to know if there is a Greatest Common Denominator (GCD) that can be used to generate these frequencies? Do you have a tool that can be used to determine a GCD and the required PFD? Thanks.

Best Regards.

774.881118876 MHz

768 MHz.

780.190476192 MHz.

680.4 MHz.

720.0 MHz.

786.432 MHz.

There is no tool available but from the definition of the GCD you can find the maximum Fpd common to all these output frequencies.

First find the VCO fundamental frequencies from the list of desired frequencies. The VCO operates between 1500MHz and 3000MHz.

774881118.876*2=1549762237.752 Hz

768000000*2=1536000000 Hz

780190476.192*2=1560380952.384 Hz

680400000*4=2721600000 Hz

720000000*4=2880000000 Hz

786432000*2=1572864000 Hz

Since these are fractional Hz convert everything to milli Hz before factoring:

1549762237752 = 2e3 x 3 x 173 x 373256801

1536000000000 = 2e18 x 3 x 5e9

1560380952384 = 2e6 x 3e2 x 127x 307 x 69481

2721600000000 = 2e12 x 3e5 x 5e8 x 7

2880000000000 = 2e15 x 3e2 x 5e10

1572864000000 = 2e25 x 3 x 5e6

Find the common GCD to all these frequencies. From the definition of GCD this is the common factors across all frequencies with the smallest exponent : 2e3 x 3 = 24 milli Hz. Remember, GCD is the channel spacing and 2e14 is the max number of channels between integer boundaries. With this GCD, the maximum Fpd = 2e14 * GCD = 393.216 Hz.

It doesn't work -- we have a 19 bit N divider which limits the minimum Fpd to 2880MHz/2e19=5493.16 Hz.