144MHz PLL synthesizer
A PLL (Phase Locked Loop) synthesizer for 2m band.Configuration
I used ADF4118(f = 0.1~3GHz) as a PLL IC with a dual modulus prescaler. The VCO oscillate between f = 130~160 MHz for Vcrtl = 0~5 V. The loop filter was designed with frequency for phase detector fc = 25 kHz. I used a crystal oscillator SG-210 for fref = 50 MHz.PLL IC is manipulated by Serial Peripheral Interface (SPI) with Ardiuno. A skitch is here.
Output frequency fRF is determined by following equation with value of counters A, B and R.。
fRF = (P*B + A)fref/R
P = 32 (fixed)
A = 0-31
B = 3-8191
R = 1-16383
Then, frequency for phase detection is fc = fref/R
Characteristics
I evaluated the spectrum at fRF = 145 MHz. Spectrum for span = 500, 100kHz are shown in the below figure.Output power is approximately -7dBm(0.2mW). Spurious components fspur = fRF + N*fc (N: integer) are surpressed below -60dBc. If you want to use different fc, please optimize parameters for loop filter in order to fulfill spurious ristriction.
You can download a gerber file for PCB used here: Download