An Introduction to Spectrum Analyzers
A
N INTRODUCTION to SPECTRUM
ANALYZERS
Spectrum analyzers are one of the most important
instruments for RF microwave measurements. Being familiar
with spectrum analyzers in general is very important for
operating high frequency microwave equipment or for
performing communication measurements. In addition, being
familiar with the basic operating principals will allow you to
quickly understand other related test equipment. In this chapter,
we will briefly introduce the basic working principles of the
spectrum analyzer. After understanding the basic working
principles, you will find that a spectrum analyzer can be a
handy tool to use.
Broadband Receiver
The principal function of a spectrum analyzer is to convert
the input signal frequency down to a frequency (band) that
detection circuitry can handle. For example, a 2.4GHz signal
needs to be down-converted to several MHz before the
Detection & Display unit can process the signal. Therefore a
spectrum analyzer must be able to reduce the frequency band
down to several MHz. The first half of a spectrum analyzer is
called the radio frequency module and its task is to reduce the
input signal frequency. A mixer and a bandpass filter are used to
decrease the frequency (they can raise the frequency as well).
The mixer is a component with three ports: two inputs and one
output. Assume that the two input frequencies on input port are
f
RF
and f
LO
respectively, and then the output frequency will be
f
IF.
f
IF
is made of two signals of different frequencies (f
LO
- f
RF
and
f
LO
+ f
RF
) that appear on the output port at the same time. One
signal is the sum of the input signals and the other is the
difference. Determining which of the IF signals that will be used
depends on the system and subsequent bandpass filter design.
As for why the three ports are named after RF, LO, IF, they are
just the conventional terms that are used.
23
Summary of Contents for GRF-1300
Page 15: ...Introduction to the GRF 1300 Figure A 10 Operation interface for HyperTerminal 13 ...
Page 19: ...Overview of the Time and Frequency Domain Time domain Frequency domain 17 ...
Page 20: ...GRF 1300 User Manual and Teaching Materials NOTES 18 ...
Page 21: ...Overview of the Time and Frequency Domain NOTES 19 ...
Page 22: ...GRF 1300 User Manual and Teaching Materials NOTES 20 ...
Page 23: ...Overview of the Time and Frequency Domain NOTES 21 ...
Page 24: ...GRF 1300 User Manual and Teaching Materials 22 NOTES ...
Page 30: ...GRF 1300 User Manual and Teaching Materials NOTES 28 ...
Page 31: ...An Introduction to Spectrum Analyzers NOTES 29 ...
Page 56: ...GRF 1300 User Manual and Teaching Materials NOTES 54 ...
Page 57: ...RF Communication and Signals Experiments NOTES 55 ...
Page 58: ...GRF 1300 User Manual and Teaching Materials NOTES 56 ...
Page 59: ...RF Communication and Signals Experiments NOTES 57 ...
Page 95: ...RF Communication and Signals Experiments 10MHz frequency deviation test results 93 ...
Page 101: ...Test for Learning Outcomes NOTES 99 ...
Page 102: ...GRF 1300 User Manual and Teaching Materials NOTES 100 ...
Page 103: ...Test for Learning Outcomes NOTES 101 ...
Page 104: ...GRF 1300 User Manual and Teaching Materials 102 NOTES ...
Page 109: ...Appendix Modulation Index and Sideband Amplitude Comparison Table 107 ...