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ME1000 RF Circuit Design
Quick Start Guide - 19/23
Appendix A: ME1000 Transmitter Unit
The Transmitter Unit (TX) contains the basic blocks of a typical RF front-end system as follows:
•
RF Frequency Synthesizer
•
Bandpass Filters
•
Upconverter
•
Power Amplifier
The block diagram of the TX is shown below. The TX accepts a modulated 50 MHz intermediate
frequency (IF) signal with a maximum bandwidth of 1 MHz. This is then upconverted to 868 MHz by
the Upconverter. The Bandpass Filters suppress unwanted frequency components while the Power
Amplifier boosts the signal power to a maximum of 1 mW (into a 50
Ω
load) before being fed to the
antenna. The Power Amplifier, Upconverter, and Frequency Synthesizer, being active circuits, are
controlled by the Control Unit. The Control Unit receives commands from the personal computer (PC)
via the universal serial bus (USB) port. Applications running on the PC intercept the user’s instructions
and send the appropriate commands to the Control Unit of the TX. The Control Unit in turn provides
the necessary power and control signals to the active circuits.
Transmitter Unit
upconverter
in
upconverter
out
upconverter
LO in
synthesizer
out
filter
out
filter
in
amp
out
amp
in
filter
in
USB
port
Upconverter
RF Bandpass
Filter 1
Power
Amplifier
RF Bandpass
Filter 2
Control
Unit
Antenna
Synthesizer
filter
out
