Chapter 8
429
IF Section
Log Amplifier Assembly (P/O A4)
Synchronous Detector
A wide dynamic range linear detector is realized by the limiter (block
G), the isolation amplifier (block H), the LO amplifier (block I), and the
detector/mixer (block J). The combination of these circuits form what is
commonly known as a synchronous detector.
The input signal is split between two paths. One path flows through the
isolation amplifier and the other path flows through the limiter and LO
amplifier The path flowing through the limiter generates the LO for the
detector/mixer block. The path through the isolation amplifier drives
the RF port.
To troubleshoot this group of circuits set the RBW to 300 kHz. Inject
10.7 MHz at +6 dbm into J3. Probe the gate of A4Q404 or A4Q405 with
a scope. Look for a 0 to
−
3 V square wave. Decrease the input power
from +6 dBm to
−
84 dBm in 10 dB steps. The square wave signal should
remain unchanged. It is normal for the phase of the signal to jitter at
the lowest signal levels.
The signals at the gates of A4Q404 and A4Q405 should be 180 degrees
out of phase from each other. If they are not 180 degrees out of phase or
one of the signals are not present, troubleshoot the LO Amplifier or the
FETs in the mixer. If the signal is not a symmetrical square wave,
troubleshoot the LO amplifier. If the signal drops out prematurely or is
not present at all, troubleshoot the limiter or LO amplifier.
Repeat the procedure for an RBW
≤
100 kHz. If the log amplifier works
in the 300 kHz RBW but not in the narrower RBWs, troubleshoot the
log narrow filter in the limiter or isolation amplifier. A4CR302 and
A4CR303 are varactor diodes in the limiter filter and are used to tune
the filter.
Limiter
Refer to function block G of A4 Log Amplifier Schematic Diagram (sheet
2 of 4) in the
HP 8560 E-Series Spectrum Analyzer Component Level
Informatio
n.
The limiter consists of 7 identical 20 dB gain stages. A "log narrow
filter" is switched in for RBWs
≤
100 kHz. This filter is switched in using
the control lines NARROW between the 4th and 5th stages. During
normal operation, the limiter serves to amplify even the smallest
10.7 MHz signals up to a level sufficient to drive the LO Amplifier and
subsequent detector/mixer. This signal serves as the LO for the mixer
circuitry.
Summary of Contents for 8560E
Page 17: ...16 Contents ...
Page 24: ...23 1 General Information ...
Page 49: ...48 Chapter1 General Information Sales and Service Offices ...
Page 50: ...49 2 Adjustment Procedures ...
Page 132: ...131 2a Adjustment Procedures HP 3335A Source not Available ...
Page 146: ...145 3 Assembly Replacement ...
Page 224: ...223 4 Replaceable Parts ...
Page 251: ...250 Chapter4 Replaceable Parts Firmware Dependent Part Numbers ...
Page 253: ...252 Chapter4 Replaceable Parts Firmware Dependent Part Numbers ...
Page 255: ...254 Chapter4 Replaceable Parts Firmware Dependent Part Numbers ...
Page 257: ...256 Chapter4 Replaceable Parts Firmware Dependent Part Numbers ...
Page 259: ...258 Chapter4 Replaceable Parts Firmware Dependent Part Numbers ...
Page 261: ...260 Chapter4 Replaceable Parts Firmware Dependent Part Numbers ...
Page 263: ...262 Chapter4 Replaceable Parts Firmware Dependent Part Numbers ...
Page 265: ...264 Chapter4 Replaceable Parts Firmware Dependent Part Numbers ...
Page 267: ...266 Chapter4 Replaceable Parts Firmware Dependent Part Numbers ...
Page 268: ...267 5 Major Assembly and Cable Locations ...
Page 279: ...278 Chapter5 Major Assembly and Cable Locations Introduction Figure 5 9 Front End ...
Page 281: ...280 Chapter5 Major Assembly and Cable Locations Introduction ...
Page 282: ...281 6 General Troubleshooting ...
Page 285: ...284 Chapter6 General Troubleshooting Introduction Figure 6 1 Assembly Test Points ...
Page 286: ...Chapter 6 285 General Troubleshooting Introduction Figure 6 2 Ribbon Cable Connections 1 of 3 ...
Page 287: ...286 Chapter6 General Troubleshooting Introduction Figure 6 3 Ribbon Cable Connections 2 of 3 ...
Page 290: ...Chapter 6 289 General Troubleshooting Introduction Figure 6 5 Service Cal Data Menu ...
Page 331: ...330 Chapter6 General Troubleshooting Block Diagram Description Figure 6 6 Functional Sections ...
Page 343: ...342 Chapter6 General Troubleshooting Block Diagram Description ...
Page 345: ...344 Chapter6 General Troubleshooting Block Diagram Description ...
Page 347: ...346 Chapter6 General Troubleshooting Block Diagram Description ...
Page 349: ...348 Chapter6 General Troubleshooting Block Diagram Description ...
Page 351: ...350 Chapter6 General Troubleshooting Block Diagram Description ...
Page 353: ...352 Chapter6 General Troubleshooting Block Diagram Description ...
Page 354: ...353 7 ADC Interface Section ...
Page 406: ...405 8 IF Section ...
Page 436: ...Chapter 8 435 IF Section A5 IF Assembly Figure 8 3 IF Adjust Signature ...
Page 437: ...436 Chapter8 IF Section A5 IF Assembly Figure 8 4 Detailed IF Adjust Signature 1 ...
Page 438: ...Chapter 8 437 IF Section A5 IF Assembly Figure 8 5 Detailed IF Adjust Signature 2 ...
Page 439: ...438 Chapter8 IF Section A5 IF Assembly Figure 8 6 Detailed IF Adjust Signature 3 ...
Page 440: ...Chapter 8 439 IF Section A5 IF Assembly Figure 8 7 Detailed IF Adjust Signature 4 ...
Page 441: ...440 Chapter8 IF Section A5 IF Assembly Figure 8 8 Detailed IF Adjust Signature 5 ...
Page 443: ...442 Chapter8 IF Section A5 IF Assembly Figure 8 9 Noisy Signature ...
Page 444: ...Chapter 8 443 IF Section A5 IF Assembly Figure 8 10 Noise with Correct Shape ...
Page 445: ...444 Chapter8 IF Section A5 IF Assembly Figure 8 11 Region B Amplitude Variation ...
Page 447: ...446 Chapter8 IF Section A5 IF Assembly Figure 8 13 Faulty Crystal Short ...
Page 463: ...462 Chapter8 IF Section Cal Oscillator Assembly P O A4 ...
Page 465: ...464 Chapter8 IF Section Cal Oscillator Assembly P O A4 ...
Page 467: ...466 Chapter8 IF Section Cal Oscillator Assembly P O A4 ...
Page 469: ...468 Chapter8 IF Section Cal Oscillator Assembly P O A4 ...
Page 470: ...469 9 Controller Section ...
Page 486: ...Chapter 9 485 Controller Section Display Problems 8560E Figure 9 10 Delta Y Waveform ...
Page 503: ...502 Chapter9 Controller Section Keyboard Problems ...
Page 505: ...504 Chapter9 Controller Section Keyboard Problems ...
Page 506: ...505 10 Synthesizer Section ...
Page 577: ...576 Chapter10 Synthesizer Section A21 OCXO ...
Page 579: ...578 Chapter10 Synthesizer Section A21 OCXO ...
Page 581: ...580 Chapter10 Synthesizer Section A21 OCXO ...
Page 582: ...581 11 RF Section ...
Page 598: ...Chapter 11 597 RF Section A14 Frequency Control Assembly Figure 11 2 A7 LODA Drive ...
Page 617: ...616 Chapter11 RF Section A10 Tracking Generator Option 002 ...
Page 618: ...617 12 Display Power Supply Section ...
Page 651: ...650 Chapter12 Display Power Supply Section A6 Power Supply Assembly ...
Page 653: ...652 Chapter12 Display Power Supply Section A6 Power Supply Assembly ...
Page 654: ...653 13 Component Level Information Packets ...
Page 660: ...Chapter 13 659 Component Level Information Packets Introduction ...