3 Short-Range Comms & IoT Mode
3.8 SEM Measurement
There are other times where selecting the low noise path improves performance,
too. Compression-limited measurements such as finding the nulls in a pulsed-RF
spectrum can profit from the low noise path in a way similar to the TOI-limited
measurement illustrated. Accuracy can be improved when the low noise path allows
the optimum attenuation to increase from a small amount like 0, 2 or 4dB to a
larger amount, giving better return loss at the instrument input. Harmonic
measurements, such as second and third harmonic levels, are much improved using
the low noise path because of the superiority of that path for harmonic (though not
intermodulation) distortion performance.
µW Preselector Bypass
Toggles the preselector bypass switch for band 1 and higher. When the microwave
presel is on, the signal path is preselected. When the microwave preselector is off,
the signal path is not preselected. The preselected path is the normal path for the
instrument.
The preselector is a tunable bandpass filter which prevents signals away from the
frequency of interest from combining in the mixer to generate in-band spurious
signals (images). The consequences of using a preselector filter are its limited
bandwidth, the amplitude and phase ripple in its passband, and any amplitude and
phase instability due to center frequency drift.
Short Range Comms & IoT Mode User's &Programmer's Reference 1071
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