R&S SMA100B - Page 301

Reference oscillator
R&S
®
SMA100B
301User Manual 1178.3834.02 ─ 09
●
Source = "Internal"
●
Reference Output/1 GHz Reference Output = "10 MHz"
●
Optional:
– External Tuning Active = "On"
– External Tuning Slope = "Low"
Figure 9-1: Synchronizing instruments using the internal 10 MHz reference signal of the
R&S SMA100B
EFC = External frequency control
EFC,Ref In,Ref Out = Connectors
In phase noise measurement systems, for example, you can also use the EFC (exter-
nal frequency control) function and shift the frequency. EFC is a function that trans-
forms an external tuning voltage into frequency shift, where the value range of the
resulting frequency is a technical characteristic listed in the data sheet. See the data
sheet also for information on the sensitivity, input voltage range, impedance and maxi-
mum bandwidth for external tuning signal.
Consider the following interdependency:
●
EFC in combination with an external PLL
If the EFC is applied in combination with an external PLL (phase locked loop), the
PLL bandwidth must be smaller than the bandwidth of the external tuning signal.
●
FM-DC mode
If the measurement requires higher PLL bandwidth, we recommend that you use
the external FM modulation (DC coupling) in low noise mode.
The FM-DC mode yields a fixed tuning sensitivity that is independent of the RF out-
put frequency and corresponds to the selected FM deviation.
Sharing the 1 GHz reference frequency to obtain phase-coherent signals
Compared to 10 MHz, a 1 GHz reference signal significantly improves the achievable
phase stability between two signal sources. Because the synchronization frequency
increases by a factor of 100, the relative phase fluctuations between the sources can
be reduced.
1 GHz at connector Ref In 1GHz and 1 GHz at Ref Out 1GHz
●
External f
Ref
= 1 GHz
●
Source = "External"
●
External Reference Frequency = "1 GHz"
●
1GHz Reference Output = "1 GHz"
Using the reference frequency for instruments synchronization