03 | Keysight | Power Supply Testing – Application Note
Pure audio signal generation
A pure or clean audio signal is defined by a signal with very low distortion and noise. One
of the common contributors to signal distortion in traditional digitizers is phase dis-
continuity. Traditional digitizers typically come with relatively small arbitrary waveform
buffers that can only house a maximum of 1K to 2K samples. For complex test signals
that exceed this capacity, usually several hundred thousand samples, the signal needs
to be ‘chopped’ up into multiple pieces and then ‘stitched back’ together to recreate the
entire waveform. The ‘stitching back’ is where phase discontinuity inevitably happens.
With the M9260A PXIe audio analyzer module, you can transmit up to 1 million samples
of signal all at once, owing to its large arbitrary waveform buffer, which avoids the issue
of distortion due to phase discontinuity.
Distortion in audio signal generation can also be caused by the non-linearity of output
amplifiers. Typically, this can be resolved by using an amplifier with a higher gain. While
a traditional digitizer module typically has only three ranges (gain of 3), the M9260A PXIe
audio analyzer module has five, resulting in an output that’s relatively more linear and
accurate. With the M9260A, you can achieve:
– THD+N (20 Hz to 20 kHz): –103 dB (≥ 1 Vp)
– THD (20 Hz to 20 kHz): –106 dB
– Amplitude accuracy: ±0.087 dB (±1%)
High-performance audio measurement
Leveraging the design of the high performance Keysight U8903B audio analyzer, the
M9260A PXIe audio analyzer module provides reliable audio measurement capabilities
that matches its pure signal generation.
– Amplitude accuracy: ±0.58% for AC, ±1% for DC
– Low input residual distortion and noise: –95 dB @1 kHz, 20 Hz to 20 kHz BW
– Residual THD: –101 dB @1 kHz, 20 Hz to 20 kHz BW
– Max input amplitude: 46 Vp
– Flatness: ±0.08 dB (20 Hz to 88 kHz BW, ≤ 10 Vp)
– Ultra-low crosstalk for multi-channel measurement: –123 dB (20 kHz BW)
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