Can anyone advise what type of equipment would be needed to create a
_localized_ beat frequency (standing wave) on the order of a few KHz
by engineering the phase relationship between two 900MHz PWM carriers?
What degree of oscillator stability is implied?
That would depend on your requirement for beat frequency stability.
The following is just an illustration and is a bad
practical approach WRT stability (see last line):
The Crystek CVCO55CL-0805-0900 will move it's output
by 30 MHz for every 1.0 V difference on pad 2 (Voltage Control Pin).
This would require you to hold the control voltage variation below
300 nV pk-pk to stay within say +- 6Hz stability of your beat
frequency, provided that your reference oscillator has *no*
instability or drift. Even then, you would probably require
a crystal oven and super regulated supplies for both oscillators
to get that level of performance.
V(high)=2.50000000 F = 852.906000 MHz
V(low)=2.4999997 F = 852.905990 MHz
F(ref) = 852.900995 MHz
F(highbeat) = 5005 Hz
F(lowbeat) = 4995 Hz
The actual stability would be worse because the part
imposes (for example) a 1 KHz phase noise of about -79 dbc/Hz.
--Winston
