Frequency Generation - Agilent Technologies PSG Series Service Manual

Troubleshooting
Overall Block Description
green Light Emitting Diodes (LED). When lit the amber LED indicates that line voltage is present and the
signal generator is in standby mode. When lit the green LED indicates the signal generator is in the power-on
mode.
Front panel hardkeys/softkeys
Some front panel keys are labeled Hardkeys and are dedicated to specific functions. Dedicated hardkeys are
used to select the most commonly used features, entered values, and control the display's contrast and
intensity. Keys along the display are labeled Softkeys and are used to select the function shown to the left of
the softkey on the display. As softkeys are pressed the softkey functions change. The front panel keypad uses
a row and column configuration. Pressing a key makes a connection between a row and column. The row and
column information is routed to the A18 CPU where it is interpreted and the appropriate action is taken.
A2 Display
An LCD provides information about the instrument's settings and condition. The LCD requires a power
supply, lighting, and data. The light bulb for the back-light is powered by the A4 Inverter that converts a dc
voltage to the required ac voltage. Data is generated on the A18 CPU and routed to the LCD through the
A3 Power Switch.
Rear Panel
The power line module, LAN, GPIB, RS-232, and A20 SMI connections are located on the rear panel.
RF output connectors
The RF output connector is and APC 3.5 male or Type-N (Option 1ED) on the E8241A and E8251A models
and a 2.4 mm male on the E8244A and E8254A models. The signal generator's model and options determine
what additional connectors are installed and if the connectors are located on the front or rear panels.

Frequency Generation

The YIG oscillator generates frequencies from 3.2 GHz to 10 GHz. For desired frequencies above 3.2 GHz, the
output of the YIG oscillator is multiplied by two (10-20 GHz), or multiplied by four (20-40 GHz). These
frequencies follow the high frequency path. For frequencies up to 3.2 GHz, the YIG oscillator is tuned in the
4-8 GHz range and the output is divided by 2/4/8/16. If the desired frequency is below 250 MHz, an additional
mixer is used. These frequencies follow the low frequency path.
Highband Path - Frequencies 3.2 GHz and Above
The output of the YIG oscillator is routed to the A29 20 GHz Doubler microcircuit. Depending on the desired
frequency, the signal is routed through a frequency doubler circuitry or bypasses the doubler circuitry. The
signal is then amplified and filtered. The output of this microcircuit is routed to the A30 Modulation Filter,
which contains modulator, additional amplifiers, and filtering. If the signal generator is a 20 GHz model, the
output of the A30 Modulation Filter is routed to the A24 High Band Coupler and A25 High Band Detector,
through the optional AT1 attenuator and to the front panel RF output connector. If the signal generator is a
40 GHz model, the A30 Modulation Filter routes the signal to either the input of the A27 40 GHz Doubler (for
frequencies above 20 GHz) or to a bypass switch contained in the A27 40 GHz Doubler near its output
(frequencies up to 20 GHz). The output of the A27 40 GHz Doubler is connected to the A24 High Band
Coupler and A25 High Band Detector and routes through the optional AT1 attenuator and to the front panel
RF output connector.
Lowband Path - Frequencies Below 3.2 GHz
The output of the YIG oscillator is routed to the A29 20 GHz Doubler microcircuit. I n the A29 20 GHz
Doubler a portion of the signal is coupled off and routed t the A6 Frac-N. A divider on the A6 Frac-N reduces
the YIG frequencies of 4-8 GHz to frequencies of 250 MHz to 3.2 GHz. These frequencies are passed to the A8
Output where amplification, filtering and modulation takes place. Frequencies below 250 MHz are generated
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