RF Electronics Chapter 5: Frequency Mixers Page 109
2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0.
Chapter 5
Frequency Mixers
Introduction
Figure 5.1 shows the typical block diagram of a transmitter and a receiver. It can be seen
that in both cases frequency translation is achieved by the use of a frequency mixer. A
frequency mixer can be a passive mixer using diodes or it can be an active mixer using
transistors or FETs. In many receivers and transmitters, a succession of frequency mixing
and filtering stages are used, to ensure that the filtering requirements can be satisfied.
A frequency mixer is used as an up-converter when the output frequency is higher than
the input frequency. This is typical in a transmitter. A frequency mixer is used as a down-
converter when the output frequency is lower than the input frequency. This is typical for
a receiver. In this chapter, the term mixer denotes a frequency mixer.
RF in
Filter and
RF Amplifier
Mixer
Filter and
IF Amplifier
Transformer
Demodulator
or ADC
Mixer
Filter and
RF Amplifier
Local
Oscillator
Local
Oscillator
Filter and
IF Amplifier
Matching
Modulator
or DAC
RF out
Transmitter
Receiver
Audio or
Data In
Audio or
Data Out
Figure 5.1. Typical transmitter and receiver block diagram.
Figure 5.2. Frequencies of a mixer.
RF Electronics: Design and Simulation
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