RF64 Datasheet, PDF (18/76 Pages) List of Unclassifed Manufacturers – ADVANCED COMMUNICATIONS & SENSING

ADVANCED COMMUNICATIONS & SENSING
3.3. Transmitter Description
The RF64 is set to transmit mode when MCParam_Chip_mode = 100.
Amplification
Second
up-conversion
First up-conversion
Int erpolation
filters
DACs
DDS
RFIO
PA
I
LO1 Tx
Q
I
LO2 Tx
Q
I
LO2 Tx
Q
W av eform
generator
RF64
Data
Clock
RF
IF
Baseband
Figure 8: Transmitter Architecture
3.3.1. Architecture Description
The baseband I and Q signals are digitally generated by a DDS whose digital to analog converters (DAC) followed
by two anti-aliasing low-pass filters transform the digital signal into analog in-phase (I) and quadrature (Q)
components whose frequency is the selected frequency deviation (Fdev).
1
Fdev
I(t)
Q(t)
Figure 9: I(t), Q(t) Overview
In FSK mode, the relative phase of I and Q is switched by the input data between -90°and +90°with continuous
phase. The modulation is therefore performed at this initial stage, since the information contained in the phase
difference will be converted into a frequency shift when the I and Q signals are up-converted in the first mixer
stage. This first up-conversion stage is duplicated to enhance image rejection. The FSK convention is such that:
DATA ''1'' Frf  Fdev
DATA ''0'' Frf  Fdev
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