Vector modulation is used to encode the chroma
signal in NTSC analog broadcast video and data in digital telecom
modems. It is also used in wireless applications such as GSM.
SystemView can be used to model any of these applications.
The following discussion is based on the SystemView Application
Note AN121B – QPSK Transmitter and Receiver Simulation using
Ideal Component. and the journal Communications Systems Design
of July and August 1998.
A transceiver is simply a transmitter and receiver combined
in a single unit. A full duplex connection therefore requires a
pair of transceivers.
Transceiver Block Diagram
GSM Time Frame
GSM uses TDMA/FDMA. The 25 MHz bandwidth is divided into
124 carrier frequencies spaced 200 KHz apart. Each carrier is time
division multiplexed into 26 slots containing 8 full duplex voice
channels plus control channels.
The time-slot burst rate is 270.833 Kbps. This digital
signal is modulated onto the analog carrier frequency using GMS.
The transmitter will be examined first.