522 Chapter11
Synthesizer Section
Introduction
Introduction
The synthesizer section includes the A7 LOMA (LO multiplier/
amplifier), the A11 YTO, and parts of the A14 frequency control and
A15 RF assemblies. Simplified and detailed block diagrams for each
assembly are located at the end of this chapter.
Page
Test Connector Locations.............................................. page 524
Troubleshooting Test Setup...........................................page 527
Confirming a Faulty Synthesizer Section.....................page 528
General PLL Troubleshooting ......................................page 534
PLL Locked at Wrong Frequency ..............................page 534
Unlocked PLL .............................................................page 535
Unlocked Reference PLL (100 MHz VCXO) ................page 537
Operation (100 MHz VCXO) ......................................page 537
Troubleshooting (100 MHz VCXO) ............................page 537
Third LO Driver Amplifier (100 MHz VCXO) ..........page 541
Unlocked Offset Lock Loop (Sampling Oscillator) ......page 547
Operation ....................................................................page 547
Troubleshooting ..........................................................page 547
Unlocked YTO PLL .......................................................page 551
Operation ....................................................................page 551
Troubleshooting an Unlocked YTO PLL ...................page 553
Unlocked Fractional N PLL ..........................................page 560
Operation ....................................................................page 560
Confirming an Unlocked Condition ...........................page 560
Fractional N PLL .......................................................page 561
Frequency Span Accuracy Problems ............................page 568
Determining the 1st LO Span ...................................page 568
Confirming Span Problems ....................................... page 569
YTO Main Coil Span Problems (LO Spans >20 MHz) .page 570
YTO FM Coil Span Problems (LO Spans 2.01to 20 MHz) .page 570
Fractional N Span Problems (LO Spans ≤2 MHz) ....page 572
1st LO Span Problems (All Spans) ............................page 572
1st LO Span Problems (Multiband Sweeps) .............page 573
Phase Noise Problems ...................................................page 575
Phase Noise in Locked versus Unlocked Spans .......page 575
Reference versus Reference PLL Phase Noise .........page 576
Fractional N versus Offset PLL or YTO PLL Phase Noise page 576
Sampler and Sampler IF ..............................................page 577
Sweep Generator Circuit ..............................................page 579
A21 OCXO .....................................................................page 585
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