GW Instek GRF-1300A - Manual (Page 62)

GRF-1300A User Manual and Teaching Materials
Experiment 5: AM Signal Measurement
Relevant
information Message signals are usually of a low frequency. In general,
these low frequency signals are not appropriate for
transmission. Therefore, modulation is required to transmit
messages for communication and test systems. Modulation is a
signal adjustment method used in signal transmission. It is used
to modulate a low frequency signal which carries information
with a signal of an appropriate frequency. This is used to solve
problems associated with the amplification and transmission of
weak signals. The role of modulation in RF communication
systems is essential. Not only is modulation used to modulate
the original low-frequency signal and its transmission, but it is
also used for frequency division multiplexing (FDM). If signals
with the same frequency range are transmitted on the same
channel at the same time, they can easily interfere with each
other, and hence why they are first modulated onto different
carriers so that multiple signals can be transmitted
simultaneously. These experiments start with amplitude
modulation. The spectrum analyzer is used to measure the
characteristics of AM signals, which has a great significance for
students to master FM as well as AM principles and
characteristics.
Item Equipment Quantity Note
1 Spectrum analyzer 1 GSP-730
2 RF & Communication Trainer 1 GRF-1300A
3 RF wire 2 100mm
4 RF wire 1 800mm
Experiment
equipment
5 Adapter 1 N-SMA
Experiment
goals 1. Learn the working principals of amplitude modulation.
2. Use the spectrum analyzer to measure the AM characteristics
of an RF signal.
Experiment
principles Modulation is the process of moving a low-frequency signal
to a high-frequency and then transmitting the high-frequency
signal. Generally the low frequency signal carrying the original
information is called the modulating signal or baseband signal.
The high-frequency signal is known as the carrier signal. After
the carrier signal is modulated by the modulating signal, the
resultant signal is called the modulated wave. There are three
kinds of modulation methods that are used: AM, FM and phase
modulation.
60