Chapter 7
355
General Troubleshooting
Block Diagram Description
Fine frequency control originates from a preselector peak DAC located
on the A3 interface assembly. Values for the preselector peak DAC are
interpolated approximately every 17 MHz based upon data taken
during the frequency response (flatness) adjustment. The preselector
bandwidth varies from greater than 30 MHz, at 2.75 GHz, to greater
than 60 MHz, at 26.5 GHz.
The mixer is ac coupled. It uses the first, second, and fourth harmonics,
mixed with the 1st LOcal oscillator, to cover the frequency range. A PIN
diode switch in A7 LOMA directs the 1st LO to the appropriate mixer.
The A14 frequency control assembly provides PIN diode bias.
A11 YTO
A11 is a YTO (YIG-tuned oscillator). YIG (yttrium-iron-garnet) is a
ferro-magnetic material which is polished into a small sphere and
precisely oriented in a magnetic field. Changes in this magnetic field
alter the frequency generated by the YTO. Current control of the
magnetic field surrounding the YIG sphere tunes the oscillator to the
desired frequency.
A12 Switched Barium-Tuned Mixer (SBTX)
The switched barium-tuned mixer (SBTX) is a combination of an RF
switch, tracking preselector, millimeter (26.5 GHz to 50 GHz) mixer,
and low-noise amplifier. The PIN diode switch directs the RF input to
the appropriate mixer in the A12 SBTX or to A10 RYTHM, where it
may be again switched to the A8 low band mixer.
The tracking preselector is a barium-tuned filter. It functions as a
tunable bandpass filter for millimeter signals. Coarse frequency control
originates from slope and offset DACs located on the A14 frequency
control assembly. (Slope and offset DAC values are loaded into
EEROM.)
Fine frequency control originates from a preselector peak DAC located
on the A3 interface assembly. Values for the preselector peak DAC are
interpolated approximately every 17 MHz based upon data taken
during the frequency response adjustment ('front-end cal'). The
preselector 3 dB bandwidth varies from approximately 200 MHz at
26.5 GHz to approximately 300 MHz at 50 GHz.
The millimeter mixer IF (3.9107 GHz) is fed through a low-noise
amplifier and one input of a PIN diode switch before being sent to the
A13 second converter. The other switch input accepts the IF output of
the A8 low band mixer.
Summary of Contents for 8564EC
Page 17: ...25 1 General Information ...
Page 37: ...47 2 Adjustment Diagnostic Software ...
Page 77: ...89 3 Manual Adjustment Procedures ...
Page 129: ...161 3a Manual Adjustment Procedures 3335A Source not Available ...
Page 142: ...175 4 Assembly Replacement ...
Page 194: ...Chapter 4 257 Assembly Replacement Procedure 13 A21 OCXO Figure 4 34 A21 OCXO Mounting Screws ...
Page 196: ...259 5 Replaceable Parts ...
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Page 224: ...303 6 Major Assembly and Cable Locations ...
Page 234: ...315 7 General Troubleshooting ...
Page 238: ...Chapter 7 319 General Troubleshooting Introduction Figure 7 2 Ribbon Cable Connections 1 of 3 ...
Page 239: ...320 Chapter7 General Troubleshooting Introduction Figure 7 3 Ribbon Cable Connections 2 of 3 ...
Page 242: ...Chapter 7 323 General Troubleshooting Introduction Figure 7 5 Service Cal Data Menu ...
Page 271: ...352 Chapter7 General Troubleshooting Block Diagram Description Figure 7 6 Functional Sections ...
Page 283: ...364 Chapter7 General Troubleshooting Block Diagram Description ...
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Page 287: ...377 8 ADC Interface Section ...
Page 291: ...Chapter 8 381 ADC Interface Section Introduction Figure 8 2 A3 Test Connector Pin Locations ...
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Page 322: ...427 9 IF Section ...
Page 356: ...Chapter 9 461 IF Section A5 IF Assembly Figure 9 13 Detailed IF Adjust Signature 5 ...
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Page 379: ...487 10 Controller Section ...
Page 394: ...521 11 Synthesizer Section ...
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Page 454: ...593 12 RF Section ...
Page 489: ...628 Chapter12 RF Section A15 RF Assembly Figure 12 10 10 MHz TTL Reference at U304 Pin 13 ...
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Page 492: ...633 13 Display Power Supply Section ...
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Page 505: ...671 14 Component Level Information Packets ...
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