Specifications

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You may wish to alternate between C19 and R5 adjustments as you approach the final optimal point.
Temporarily note intermodulation rejection level.
Start cutting output stubs in locations E, G, F, H (in that order) in a similar manner to the input tuning scheme. After
any cut. Readjust C19 and R5 to find the lowest intermod. If intermod rejection level has gotten worse as a result of
the stub cut, then reattach the stub using solder and adjustment is complete.
If intermod improves as a result of a stub cut, then record the new intermod rejection level and cut the next stub in the
rotation. Repeat the C19 and R5 optimization.
As you gain experience, you will determine certain head start staring positions for each band. The table below
provides some examples for guidance.
As you improve the output match, you may need to readjust input levels to get the desired +30 dBm per carrier output
operating level. If you wish to adjust in sub dB steps, fine adjustment of supply voltage may help achieve the target.
Record final best intermod rejection and record IP3. Measure the difference between the lowest main carrier and the
highest intermod product. Divide this dB ratio by two. Add this to the main carrier level. This is the third order
intercept point.
• Review Input Return Loss (Optional once process capability proven)
If drastic tuning occurred at the output and you are not using first attempt guideline stub settings, then input match may
need further fine tuning. Return to setup of Fig. 1 and verify that input return loss is roughly centered at the operating
band and remains within minimum spec. You may need to repeat the procedure of 4.6. If input match requires
readjustment, then IP3 measurement must be re-verified, and C19 and R5 may require additional tweaks.
• Measure 1 dB Compression Point.
Set up a single signal generator at mid-band frequency and apply its signal to the UUT input. Adjust for output power
of +34 dBm.
Set up signal generator to use 10 dB amplitude increments. Toggle level between current setting and a setting 10 dB
higher and observe output level change. Fine adjust the generator level while keeping increment at 10 dB until the
difference in output level for a 10 dB step at input is 9 dB. Typically, the output will alternate between levels of + 34
and +42 dBm. In this example, +42 dBm would be the 1 dB output compression point.
During compression tests, some LDMOS amplifiers may “run away”. If supply current goes above 2.25 A, then do not
proceed with higher input levels.
• Temperature Limit Setting
Ensure R19 & R29 are fully counter-clockwise. Temporarily connect an 11K resistor in parallel with R28, a Thermistor.
Measure voltage at pin 8 of U1D. It should be approximately 6.7 VDC. An allowable range can be determined after a
quantity of units have been built, but a 10% variation should be tolerable. Adjust R29 clockwise until the voltage at pin
8 of U1D drops to 0 VDC. Remove the 11K resistor.
• Over-current Back-down and Under-current Fault Detect
Apply an input carrier of sufficient strength at mid-band to obtain an output power of +45 dBm. Use the Figure #2 setup
with one generator off. Turn R19 clockwise until power drops to +44 dBm.
• Record Results
Record desired operating band.
Record gain at mid-band and band edges.
Record input return loss mid-band and at edges.
Record Third order intercept point at mid-band.
Record mid-band 1 dB compression.
Record quiescent current.