CLOCK OSCILLATOR FOR DDS |
New 179,2MHz Oscillator suitable for AD9850/1 clocking. The signal from quartz oscillator (TCXO 12,8MHz) is multiplied by 14 times. The output signal is clean, low harmonics content can be observed. Phase noise performances are more better than AD9851 internal clock multipler!
My old clock oscillator was replaced by this design due good frequency stability and low level harmonics.
DDS clock input must to be biased at +2,5V (Vdd/2) by one voltage divider (two 2K2 resitors connected between +Vdd, Clock input and Gnd). In this way is possible to use a sinusoidal signal without any shift level converter. The output of oscillator is already AC coupled (1nF capacitor).
Because the distance between harmonics is quite small, band pass filter adjustement is very important. Output signal can be monitored by a spectrum analyser or a wide band VHF receiver. In this way, 14th harmonic can be selected with good accuracy.
NEW TCXO OSCILLATOR(schematic)
OLD OSCILLATOR(schematic)
PCB Files(pdf + sprint layout)