Lambda SR1, Operation Manual, Page: 118 / 317

SR1 Operation Manual 118
© 2014 Stanford Research Systems
automatically adjusts the input attenuation and gain, and an analog frequency measurement is made on
both input channels. When the HiRes converter is selected, the two signals are digitized by a 24-bit
stereo ADC. As in the HiBw case, the phase and level measurements are computed by the DSP. The
Amplitude Chain, unlike the HiBw case, is implemented purely in the DSP. For the HiRes converter, the
Bandpass/Notch filter is implemented digitally by the DSP. There is no post-filter gain. Bandwidth
limiting and weighting filters are implemented digitally. The DSP measures the amplitude signal with a
selectable RMS/Peak/Quasi-Peak response.
The amplitude signal is reconverted to an analog signal by a DAC and is output on the rear panel "A0
Monitor Out" (or "A1 Monitor Out", depending on which analyzer is being used) BNC connector. Finally,
the amplitude signal is sent to the "Other Analyzer" (e.g. A1 if the TDD is active on A0, or A0 if the TDD
is active on A1). If the "Other Analyzer" is an FFT analyzer whose input is set to "Other Analyzer" the
FFT analyzer will display the spectrum of the post Notch/BP filtered, bandwidth limited, weighted
amplitude signal.
Time Domain Detector: Digital Audio Inputs
Detailed TDD Block Diagram : Digital Audio Inputs
(Show n for Ch. A Selected)
For digital signals all calculations are performed by the DSP. A digital audio receiver decodes and
demultiplexes the multiplexed bi-phase encoded digital audio signal and the decoded amplitude data for
both channel is sent to the DSP. The DSP calculates the RMS levels for both channels, the frequency
and relative phase of the input signals. For the selected channel, a 140dB deep notch or selectable
width bandpass filter is applied followed by bandwidth limiting and weighing filters. The resulting
amplitude signal is sent to a DAC where it is transformed into an analog signal available at the rear-panel
"A0 Monitor Out" (or A1 Monitor Out ) connector. The DSP computes the amplitude of the amplitude
signal with a selectable RMS, Peak, or Quasi-Peak response.