Theory And Operation; Rf Generation - SIGNALCORE SC5511A Operating & Programming Manual

T
H E O R Y A N D
Despite its small size, the SC5511A is an instrument-grade, high performance synthesizer with easy to
program register-level control. It functions as a standard synthesized CW source with the added
capability of a sweep/list mode that makes it ideal for applications ranging from automated test systems
to telecommunication equipment to scientific research labs. Being small and modular, it is the ideal
solution system integration applications that require a high performance RF source. In addition, it could
be used as a general purpose lab source. Figure 2 shows the block diagram of the device, and the
following sub-sections provide details to its operation.
REF
IN
TCXO
10
REF
OUT
Figure 2. Block diagram of the SC5511A.

RF Generation

The SC5511A is a 100 MHz to 20 GHz low phase noise and low spur synthesizer, using a hybrid
architecture comprising of phase lock, harmonic generation, and a DDS functions. Coarse tuning is
accomplished by PLL and harmonic generators, while fine tuning is accomplished with the variable
modulus DDS, providing exact frequency generation. Isolation between the internal oscillators, their
mixed IF products, harmonics, and inter-modulation products is accomplished by internal EMI sealed
cavities. A hybrid architecture with well-shielded cavities improves the overall phase noise performance
and reduces the spurious signal content of this compact size frequency synthesizer. Signals are
synthesized from an internal 10 MHz TCXO reference clock, or an external 10 MHz reference.
The SC5511A has 2 independent channels; channel 1 frequency range is from 100 MHz to 20 GHz with
frequency resolution of 1 Hz, while the range on channel 2 is from 25 MHz to 3 GHz with 25 MHz step.
Channel 1 has calibrated power level adjustment but this feature is not available on channel 2.
Furthermore list and sweep modes are only available for channel 1. A typical use of the 2 channels is to
drive LO ports of mixers for a dual stage downconverter where the first RF stage is tunable and the
second IF stage is fixed.
SC5511A User Manual
O
P E R A T I O N
10 GHz -
Fine Step
20 GHz
Gen
Gen
Harmonic FracN
Step Gen Step Gen
VCXO
Rev 1.7.0
FILT
BANK
N
ALC
25 MHz
Step Gen
RF1
OUT
RF2
OUT
8