Analog Frequency Multiplier

PL560-xx VCXO Family

47745 Fremont Blvd., Fremont, CA 94538 TEL (510) 492-0990, FAX (510) 492-0991

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Rev.:02-09-07 Page 7

DETERMINING STRAY L’s AND C’s IN A LAYOUT

Figure 6: Diagram Representation of the Board Layout

Lets take the PL560-38 (4x VCXO) for example. This takes a crystal input in the range of 30 to 80 MHz and

multiplies it to an output of 120 to 320 MHz. To determine the stray L’s and C’s of the layout we will assemble

two test units. One AFM will be tuned to the lower range of the device (120 MHz), and the other to the upper

range of the device (320 MHz).

120 MHz AFM Tuning: Using the “AFM Tuning Assistant” find the PL560-3x in the L2X worksheet. Enter the

Cinternal value found next to it into cell B21. In cell B24 enter the closest standard inductor value (see CoilCraft

0603CS series for example) to achieve the closest peak frequency to 60 MHz. Repeat the same procedure for

L4X at 120 MHz.

Results: L2X = 180 nH, L4X = 82 nH.

320 MHz AFM tuning: Repeat the previous procedure for L2X at 120 MHz and L4X at 320 MHz.

Results: L2X = 24 nH, L4X = 10 nH.

Proceed and assemble the test units.

Measuring 120 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 30 MHz. Since this is the

2x port, the scope will show 60 MHz with ~ 3V pk-pk amplitude. Vary the generator above and below 30 MHz until