Rohde & Schwarz SMIQ02B - Digital Modulation

Digital Modulation SMIQ
1125.5555.03 E-92.86
2.10 Digital Modulation
With option Modulation Coder (MCOD) SMIQB20 provided, SMIQ can generate digitally modulated
output signals. Available modulation methods are ASK (amplitude shift keying), FSK (frequency shift
keying), PSK (phase shift keying) as well as QAM (quadrature amplitude modulation). Baseband filtering
and symbol rate can be freely set in a wide range.
The modulation coder generates the analog IQ signals for the I/Q modulator of SMIQ from the digital
input signals.
sin( t)
ω
cos( t)
ω
I
Q
RF OUT
IQ modulator
RF up/down converter
Option
Modulation
Coder
SMIQB10
Option
Data
Generator
SMIQB11
Fig. 2-47 Modulation coder in SMIQ
The modulation coder works with digital input signals such as
• clock signals (symbol clock, bit clock),
• modulation data or modulation symbols,
• control signals for envelope control and trigger signals.
The digital input signals may originate from the following sources:
• The modulation coder can generate clock signals such as PRBS data signals and simple data
patterns.
• External clock signals, modulation data and signals for envelope control can be fed in via connectors
at the front or rear panel of SMIQ.
• With option Data Generator SMIQB11 provided, an additional data source is available. This option
has a 16-Mbit memory for modulation data and control signals. The memory can be extended to
48 Mbit or 80 Mbit by installing one or two SMIQB12 options (Memory Extension).
I
DATA MEMORY
Q
DIGITAL
IN/OUT
PRBS GENERATOR
INT CLOCK
DIGITAL
MODULATOR
EXT DATA/CLOCK
Modulation coder
Data generator
Fig. 2-48 Digital input signals of modulation coder