Chapter 9
443
IF Section
Log Amplifier (P/O A4 Assembly)
Log Amplifier (P/O A4 Assembly)
The log amplifier on the A4 assembly performs several functions. It
provides log and linear paths converting the 10.7 MHz IF signal to
video. In addition it also provides offset circuitry, AM/FM demodulator
circuitry, a frequency counter output, and down conversion of the
10.7 MHz IF to 4.8 kHz for use by the digital IF.
The log amp results are realized by using a wide dynamic range linear
detector followed by a video log amp. The detector is used for both
linear and log paths and contains a mixer that acts as the down
converter mixer for the digital IF.
CAUTION
For troubleshooting, it is recommended that you use an active probe,
such as an 85024A, and another spectrum analyzer. If an 1120A active
probe is being used with a spectrum analyzer having dc coupled inputs,
such as the 8566A/B, 8569A/B and the 8562A/B, either set the active
probe for an ac-coupled output or use a dc-blocking capacitor between
the active probe and the spectrum analyzer input. Failure to do this can
result in damage to the spectrum analyzer or the probe.
Log Amplifier
Refer to function blocks K, L, and AE of A4 Log Amplifier Schematic
Diagram (sheets 3 of 4 and 4 of 4) in the
8560 E-Series Spectrum Analyzer
Component Level Informatio
n. The log amplifier receives the detected
video signal from the Detector/Mixer and outputs a voltage proportional
to the log of the input voltage. The linear output is tapped off at the
emitter of U501D. U507 provides input offset adjustment capability and
adjusts the offset of the op amp formed by U501A, B, C, and D. Q502 is
a buffer. Q501 switches in additional offset for digital RBWs. The
logarithmic characteristic of the base-emitter junction of U502B is used
in the feedback path to produce the logging affect. U502D is used to
adjust for non-linearities in the linear mode. R531 is used to adjust log
fidelity at the top of the screen.
Use the following steps to verify proper operation of the log amplifier
chain:
1. Press
CAL
and
IF ADJ OFF
. Set the digital multimeter to read dc volts
and connect the negative lead to the chassis of the 8564EC or
8565EC spectrum analyzer.
2. Remove W27 from A4J3 and inject a 10.7 MHz signal of +10 dBm
into A4J3.
3. Set the 8564EC or 8565EC spectrum analyzer to log mode, with
a resolution bandwidth of 300 kHz and single sweep.
Содержание 8564EC
Страница 17: ...25 1 General Information ...
Страница 37: ...47 2 Adjustment Diagnostic Software ...
Страница 55: ...Chapter 2 65 Adjustment Diagnostic Software 2 LO Frequency Figure 2 2 LO Frequency Adjustment Locations ...
Страница 57: ...Chapter 2 67 Adjustment Diagnostic Software 3 YTO FM Coil Figure 2 3 YTO FM Coil Adjustment Locations ...
Страница 77: ...89 3 Manual Adjustment Procedures ...
Страница 129: ...161 3a Manual Adjustment Procedures 3335A Source not Available ...
Страница 142: ...175 4 Assembly Replacement ...
Страница 151: ...184 Chapter4 Assembly Replacement Procedure 2 A1 Front Frame A18 LCD Figure 4 2 LCD Assembly Exploded View ...
Страница 163: ...Chapter 4 205 Assembly Replacement Procedure 5 A2 A3 A4 and A5 Assemblies Figure 4 10 Assembly Cables 2 of 3 ...
Страница 166: ...208 Chapter4 Assembly Replacement Procedure 5 A2 A3 A4 and A5 Assemblies Figure 4 14 GPIB and A1A1 W1 Cable Placement ...
Страница 168: ...210 Chapter4 Assembly Replacement Procedure 6 A6 Power Supply Assembly Figure 4 15 Power Supply Cover ...
Страница 176: ...226 Chapter4 Assembly Replacement A9 Input Attenuator Figure 4 22 A9 and A10 A12 Mounting Screws ...
Страница 179: ...Chapter 4 229 Assembly Replacement A11 YTO Figure 4 23 A11 Mounting Screws at Right Side Frame ...
Страница 183: ...Chapter 4 233 Assembly Replacement Procedure 8 A14 and A15 Assemblies Figure 4 25 A14 and A15 Assembly Cables ...
Страница 190: ...Chapter 4 243 Assembly Replacement Procedure 11 Rear Frame Rear Dress Panel Figure 4 29 A6 Power Supply Cover ...
Страница 194: ...Chapter 4 257 Assembly Replacement Procedure 13 A21 OCXO Figure 4 34 A21 OCXO Mounting Screws ...
Страница 196: ...259 5 Replaceable Parts ...
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Страница 224: ...303 6 Major Assembly and Cable Locations ...
Страница 228: ...Chapter 6 307 Major Assembly and Cable Locations Introduction Figure 6 2 Top View A2 and A3 Unfolded ...
Страница 229: ...308 Chapter6 Major Assembly and Cable Locations Introduction Figure 6 3 Top View A2 A3 A4 and A5 Unfolded ...
Страница 230: ...310 Chapter6 Major Assembly and Cable Locations Introduction Figure 6 5 Bottom View A15 Unfolded ...
Страница 231: ...Chapter 6 311 Major Assembly and Cable Locations Introduction Figure 6 6 Bottom View A15 and A14 Unfolded ...
Страница 233: ...314 Chapter6 Major Assembly and Cable Locations Introduction Figure 6 9 Rear View FL4 B1 BT1 A20 VGA Connector ...
Страница 234: ...315 7 General Troubleshooting ...
Страница 238: ...Chapter 7 319 General Troubleshooting Introduction Figure 7 2 Ribbon Cable Connections 1 of 3 ...
Страница 239: ...320 Chapter7 General Troubleshooting Introduction Figure 7 3 Ribbon Cable Connections 2 of 3 ...
Страница 242: ...Chapter 7 323 General Troubleshooting Introduction Figure 7 5 Service Cal Data Menu ...
Страница 271: ...352 Chapter7 General Troubleshooting Block Diagram Description Figure 7 6 Functional Sections ...
Страница 283: ...364 Chapter7 General Troubleshooting Block Diagram Description ...
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Страница 287: ...377 8 ADC Interface Section ...
Страница 291: ...Chapter 8 381 ADC Interface Section Introduction Figure 8 2 A3 Test Connector Pin Locations ...
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Страница 322: ...427 9 IF Section ...
Страница 356: ...Chapter 9 461 IF Section A5 IF Assembly Figure 9 13 Detailed IF Adjust Signature 5 ...
Страница 358: ...Chapter 9 463 IF Section A5 IF Assembly Figure 9 14 Noisy Signature Figure 9 15 Noise with Correct Shape ...
Страница 359: ...464 Chapter9 IF Section A5 IF Assembly Figure 9 16 Region B Amplitude Variation Figure 9 17 Region B Amplitude Offset ...
Страница 369: ...474 Chapter9 IF Section Cal Oscillator P O A4 Assembly Figure 9 21 Output Waveform 10 kHz Resolution Bandwidth ...
Страница 370: ...Chapter 9 475 IF Section Cal Oscillator P O A4 Assembly Figure 9 22 Output Waveform 3 kHz Resolution Bandwidth ...
Страница 371: ...476 Chapter9 IF Section Cal Oscillator P O A4 Assembly Figure 9 23 Output Waveform 1 kHz Resolution Bandwidth ...
Страница 372: ...Chapter 9 477 IF Section Cal Oscillator P O A4 Assembly Figure 9 24 Output Waveform 300 Hz Resolution Bandwidth ...
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Страница 379: ...487 10 Controller Section ...
Страница 394: ...521 11 Synthesizer Section ...
Страница 431: ...564 Chapter11 Synthesizer Section Unlocked Fractional N PLL Figure 11 8 VCO Bias Voltages for A14 Assemblies ...
Страница 447: ...Chapter 11 581 Synthesizer Section Sweep Generator Circuit Figure 11 11 Simplified Synthesizer Section ...
Страница 448: ...582 Chapter11 Synthesizer Section Sweep Generator Circuit Figure 11 12 Simplified A14 Assembly Block Diagram ...
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Страница 454: ...593 12 RF Section ...
Страница 475: ...614 Chapter12 RF Section A14 Frequency Control Assembly Figure 12 4 A7 LO Multiplier Amplifier Drive ...
Страница 489: ...628 Chapter12 RF Section A15 RF Assembly Figure 12 10 10 MHz TTL Reference at U304 Pin 13 ...
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Страница 492: ...633 13 Display Power Supply Section ...
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Страница 505: ...671 14 Component Level Information Packets ...
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