3 IQ Analyzer (Basic) Mode
3.1 Complex Spectrum Measurement
Ranges
Option Option # Phase Noise Option Range
No EPx Option 1 Best Close-in [offset < 20 kHz]
2 Best Wide-offset [offset > 30 kHz]
3 Fast Tuning [same as Best Close-In]
EP0 4 Best Close-in [offset < 600 kHz]
1 Balanced [offset < 600 kHz]
5 Best Spurs [offset < 600 kHz]
2 Best Wide-offset [offset > 800 kHz]
3 Fast Tuning [same as Best Close-In]
EP1 1 Best Close-in [offset < 140 kHz]
2 Best Wide-offset [offset > 160 kHz]
3 Fast Tuning [single loop]
EP2, EP3, EP5 1 Best Close-in [offset < 70 kHz]
2 Best Wide-offset [offset > 100 kHz]
3 Fast Tuning [medium loop bw]
EP4 1 Best Close-in [offset < 90 kHz]
2 Best Wide-offset [offset > 130 kHz]
3 Fast Tuning [same as Best Close-In]
ADC Dither
Accesses the menu to control the ADC Dither function. The dither function enhances
linearity for low level signals at the expense of reduced clipping-to-noise ratio. The
reduced clipping-to-noise ratio results in higher noise, because we work to ensure
that the clipping level of the ADC relative to the front terminals remains unchanged
with the introduction of dither, and this results in reduced ADC dynamic range. So,
making measurements with ADC DitherON gives you better amplitude linearity, but
turning ADC DitherOFF gives you a lower noise floor (better sensitivity).
With dither ON, the third-order distortions are usually invisible for mixer levels below
–35 dBm. With dither OFF, these distortions can be visible, with typical power levels
of –110 dBm referred to the mixer. Detection nonlinearity can reach 1 dB for dither
off at mixer levels around –70 dBm and lower, while the specified nonlinearity is
many times smaller with dither ON.
When ADC Dither is ON, the linearity of low-level signals is improved. The enhanced
linearity is mostly improved scale fidelity. The linearity improvements of dither are
most significant for Res BWs of 3.9 kHz and less in swept mode, and FFT widths of 4
kHz and less in FFT mode.
257 IQ Analyzer Mode User's &Programmer's Reference
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