Analog Frequency Multiplier

PL56X-XX VCXO Family

Measuring 320 MHz L2X: Connect the RF generator and scope probe as shown in Figure 6, above. While

power is applied to the PCB, set the generator output to +12 dBm and the frequency to 80 MHz. Since this is the

2x port the scope will show 160 MHz with ~ 3V pk-pk amplitude. Vary the generator above and below 80 MHz

until the amplitude on the scope is maximum and record the generator frequency. For example , the peak is

recorded at 78.0 x 2 = 156 MHz

In the AFM Tuning Assistant, add the scope’s probe capacitance to the Cstray cell. For our example 0.5 pF + 1.0

pF = 1.5 pF. With L2X at 24 nH adjust LWB1 (cell B23) until the peak frequency reads 156 MHz. Next replace the

L2X value with 180 nH and see if it peaks at 59.6 MHz. If it does not, adjust Cstray until 59.4 MHz is achieved.

Again enter 24 nH for L2X and fine tune LWB1 for 156 MHz.

Results: LWB1 = 1.6 nH, Cstray = 2.9 pF -0.5 pF = 2.4 pF (subtract scope probe stray capacitance)

Repeat the same steps for the L4X: Set the generator to 80 MHz. The 82 nH peaks at 118 MHz and the 10 nH

peaks at 304 MHz.

Results: LWB1 = 1.8 nH, Cstray = 2.5 pF -0.5 pF = 2.0 pF (subtract scope probe stray capacitance)

Internal Capacitor Selection by Device

Device Number

Cinternal (pF)

2X

4X

P565-08

7.625

6.250

P560-09

7.625

6.250

P560-3x

34.125

16.500

P560-4x

34.125

P560-6x

7.625