Codan Radio P25 Training Guide - Manual (Page 15)

P25 RADIO SYSTEMS | TRAINING GUIDE
Chapter 1: Introduction To P25 Page 7
The modulation sends 4800 symbols/sec with each symbol conveying 2 bits of information. The
mapping between symbols and bits is shown below:
Information Bits Symbol C4FM Deviation (Phase 1)
01 +3 +1.8kHz
00 +1 +0.6kHz
10 -1 -0.6kHz
11 -3 -1.8kHz
The C4FM modulator is comprised of a Nyquist Raised Cosine Filter, a shaping fi lter, and an FM
modulator.
Figure 1-3: C4FM Modulator
C4FM Modulator
Nyquist Raised
Cosine Filter
Digital
Input
Shaping
Filter
FM
Modulator
C4FM
Output