GW Instek GRF-1300A - Manual (Page 98)

GRF-1300A User Manual and Teaching Materials
Experiment 10: Mixer
Relevant
information In experiment 5 and 6 we introduced how the signal is modulated
onto a carrier. However, what are the other processes that need to be
performed on the modulated signal before it can be transmitted?
One thing called a frequency mixer is very import in this process.
The main function of a frequency mixer is to perform frequency
conversion; The mixer can convert the RF signal into an
intermediate frequency signal or it can do the opposite and convert
the intermediate frequency signal into an RF frequency signal in
order to transmit or process the carried message, respectively. The
goal of this experiment is to observe how a mixer will shift the
frequency spectrum of a signal from a spectrum point of view and to
understand the principles of the mixer.
Item Equipment Quantity Note
1 Spectrum Analyzer 1 GSP-730
2
RF & Communication
Trainer
1 GRF-1300A
3 USB Signal Generator 1 USG-LF44
4 RF cable 2 100mm
5 RF cable 1 200mm
6 RF cable 1 800mm
Experiment
Equipment
7 Adapter 1 N-SMA
Experiment
goals 1. To understand the working principles of the mixer.
2. To observe frequency shift by analyzing the frequency spectrum
with a spectrum analyzer.
3. To measure mixer parameters such as conversion gain and port
isolation.
Experiment
principals 1. Introduction to the concept of mixing
The mixer is used for frequency conversion. Mixing is also known
as conversion. Mixing is used to convert a modulated signal with
a carrier frequency
c
f to a modulated signal with the carrier the
frequency
L
f for processing at the next circuit. This process is
called frequency shifting (shifting of the frequency spectrum).
Frequency conversion by the mixer needs to maintain the
modulation from the modulated carrier unchanged~ so it still
carries information and has no distortion.
The basic function of a mixer is to maintain the modulation of the
96