©2018
Rev 2.0
13
Functional Description
3
Functional Description
Overview
The SC5310A uses USB as its primary interface with an optional SPI or RS232 interface. The SC5309A
is a PXIe version of the product.
The downconverter assembly consists of three module parts:
•
The Signal Conversion Module contains the mixers, filters, signal amplifiers, and attenuators. This
module is
referred to as the “signal
chain”.
•
The Synthesized Local Oscillator Module contains the 3 synthesized LO signals and the reference
signal circuitry.
•
The Power Conditioning and Digital Control Board contains the supply switchers that generate
the needs rails for the RF modules and an onboard MCU that provides both the computation
engine and interface between the user and the RF modules.
The figure below shows how the modules relate to each other.
Figure 3. Simplified Block Representation of the Downconverter Assembly Module
The downconverter has a maximum of three conversion stages. The first converted intermediate
frequency (IF) stage is called IF1, whose signal is converted from the RF input signal. The second
converted stage is called IF2, and the third converted stage is IF3. The converted signals in each stage
are derived by mixing their respective input signal with their local oscillator (LO) signal. This mixing
process results in many products and the desired product at each IF stage is picked out using band-
pass filters. Signals that appear inside the passband of the filter will be passed through, while those
that are outside the passband are suppressed. Generally, the farther an unwanted signal is away
from the filters the better it is suppressed. Unwanted signals that are close to the passband or inside
the passband are called spurious signals (or ‘spurs’ for short). Because of the wide bandwidth of the
Signal Conversion Module
Synthesized Local Oscillator Module
Supply Conditioning and Digital Control/Interface
RF Input
Ref In
Ref Out
Digital IO
Supply
IF Output
IF2 Input
LO1 Output