3-3
At the IF section the incoming signal is divided into two paths. The main route leads to image rejection filters while the
second, a highly attenuated feeler path signal is used for generation of wide band trigger signal in TRIG/GATE section
(option 06) situated on OPTION BASE board.
The main signal after passing through an image rejection filter is beat down to a 10.69 MHz signal using a 100 MHz
reference signal. This signal is then sent to various Resolution Band Width (RBW) setting circuits.
For RBW setting of 30 Hz to 200 Hz the signal is frequency converted to 450 kHz using 10.24 MHz signal. After passing
through the RBW circuits (Crystal filter circuits) the signal is up converted back to 10.690 MHz signal and passed through
wider RBW setting circuits. For RBW setting of 300 Hz to 3 MHz the signal is sent directly to wide RBW setting circuits
without any frequency modifications.
The RBW processed signal is passed onto SCAN/AD section, where it passes through logarithmic amplifiers and then to a
linear detector. This linear detected signal is passed through smoothing filters called Video Band Width Filters (VBW).
This smoothed signal is then passed through Positive or Negative peak detection circuits and the output is converted to
digital signal by a Analog to Digital Converter (ADC) circuit.
The results are then written (in digital word format) to a Dual Port RAM through one of the ports.
The CPU of the instrument on CPU section reads from the other port of Dual Port RAM and processes the data before
displaying on the LCD screen. The CPU also controls various interface functions such as reading the Key Inputs or remote
control commands received, and various outputs such as prints or plots of various data. The CPU also generates various
commands required for controlling or setting of all hardware units inside the instrument.
FRONT BOARD section generates the KEY and rotary-knob encoder data, drives the LEDs, detects the power switch
(PWR SW) setting, controls the power-supply On/Stby setting, and supplies power for the LCD backlight, etc.
3.1 Overall Circuit description
To Next Page
Loading...
