RF Circuit Design - [Ch4-2] LNA, PA, and Broadband Amplifier
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Transcript of RF Circuit Design - [Ch4-2] LNA, PA, and Broadband Amplifier
Chapter 4-2
Introduction to Low Noise, High Power,
and Broadband Amplifier Design
Chien-Jung Li
Department of Electronics Engineering
National Taipei University of Technology
Department of Electronic Engineering, NTUT
Functional Block Diagram of Communication Systems
Input
Transducer
Output
Transducer
Input Signal
(Audio, Video, Data)
Output Signal
(Audio, Video, Data)
Transmitter
(Tx)
Receiver
(Rx)
Channel
• The main job of the communication systems is to transfer
useful information from one end to the other ends.
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Block Diagram of a Basic Radio System
• Transmitter (Tx)
• Receiver (Rx)
Data in
Modulator IF Filter Mixer
Bandpass Filter
(BPF) Power Amplifier
(PA)
Antenna
Local
Oscillator
(LO)
Bandpass Filter
(BPF) Mixer IF Filter
Data out
DemodulatorIF Amplifier
Local
Oscillator
(LO)
Low Noise
Amplifier
(LNA)
Antenna
This architecture was first called superheterodyne and patented in 1917 by
Armstrong. The “transceiver” means the system that combines Tx and Rx.
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Constant NF Circles
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Noise Circle and Gain Circles (I)
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Noise Circle and Gain Circles (II)
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Noise Circle and Gain Circles (III)
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Broadband Design
• The most popular and well-established circuit techniques
employed in the design of broadband amplifiers that are
generalized in hybrid and monolithic technologies are:
Reactively matched circuit
Traveling wave distributed circuit
Feedback circuit
Lossy matched circuit
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Broadband Stability
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Broadband v.s. Narrowband Matching
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PA Matching Considerations
• In order to obtain maximum output power, typically the power
amplifier is not conjugately matched. In stead, the load is designed
such that the amplifier has the correct voltage and current to deliver
the required power.
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Matching to S22* vesus Matching to Γopt
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Class A, AB, C PAs
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Power Contour
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Power Combing
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Cascaded PA
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