5a-18
Theory of Operation
A14 Modulation Generator (Option 1E2)
A14 Modulation Generator (Option 1E2)
The modulation generator contains the DSP (digital signal processor), memory, DAC,
serial I/O for the other assemblies, and output filters. It generates sine, square, triangle,
and saw (or ramp) waveforms used to modulate the AM, FM, and ΦM states of the
instrument.
When the instrument is using the variable frequency/waveform source, the modulation
generator will work as an internal modulation source connected to the MOD
INPUT/OUTPUT port. The modulated signal can be monitored from the MOD
INPUT/OUTPUT port as a 2 Vp-p signal.
This assembly has a serial communication port and communicates with the main
controller on the A3 motherboard through this port. The calibration data for the
modulation generator output level is stored in EEPROM on this assembly.
The modulation generator has its own crystal controlled oscillator.
The DAC output signal is filtered by a 50 kHz cut-off, low-pass filter.
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