R&S SMJ100A, Operating Manual

Page: 443 / 874

Instrument Function
R&S
®
SMJ100A
427 Operating Manual 1403.7458.32 ─ 14
Carrier Spacing
Sets the spacing between carriers for the Multi Carrier CW signal.
The carriers are arranged symmetrically around the HF carrier.
The total bandwidth is calculated as follow:
Total Bandwidth = ("Number of Carriers" - 1) * "Carrier Spacing"
The result must not exceed the system bandwidth of the instrument (see data sheet).
Remote command:
[:SOURce<hw>]:BB:MCCW:CARRier:SPACing
on page 676
Clock Frequency
Displays the clock rate at which the multi carrier signal is output by the arbitrary wave-
form generator. The output clock rate depends on the number of carriers and the
selected carrier offset.
The value indicates the resolution during the marker generation.
Remote command:
[:SOURce<hw>]:BB:MCCW:CLOCk?
on page 678
Optimize Crest Factor Mode
Selects the mode for automatically minimizing the crest factor.
The carrier start phases are automatically set to this.
The crest factor represents the ratio of the peak voltage value to the rms voltage value.
The higher the crest factor and resulting dynamics of a signal, the greater the require-
ment for a power amplifier fed by the signal to be linear.
A very high crest factor arises when the carriers have an identical start phase, since
the carriers are periodically superposed and very high peak voltages occur in relation
to the rms voltage values.
Methods of reducing the crest factor differ with regard to both the optimization achieva-
ble and the time required for computation.
"Off" There are no automatic settings for minimizing the crest factor. The
"Phase" setting has an effect.
"Chirp" Very rapid crest factor optimization regardless of the number of carri-
ers. A minimal crest factor of < 3 dB is only obtained for multi carrier
signals in which all carriers are switched on and the power of the car-
riers is identical. In a configuration which differs from this, the achiev-
able crest factor is worse.
"Target Crest" Optimization of the crest factor to a desired value for all carrier config-
urations. The optimization time depends on the number of carriers
and the desired crest factor. Computation time increases only when
the number of carriers exceeds 256 and the crest factor is below 4
dB. The desired value can be entered in "Desired Crest Factor".
Note: Optimization can be cancelled at any time, and the current
value being displayed at that moment is then used.
Remote command:
[:SOURce<hw>]:BB:MCCW:CFACtor:MODE
on page 678
Baseband Signal - Baseband Block