slide1 l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
ELEC 412 RF & Microwave Engineering PowerPoint Presentation
Download Presentation
ELEC 412 RF & Microwave Engineering

Loading in 2 Seconds...

play fullscreen
1 / 22

ELEC 412 RF & Microwave Engineering - PowerPoint PPT Presentation


  • 290 Views
  • Uploaded on

ELEC 412 RF & Microwave Engineering. Fall 2004 Lecture 19. Stub Tuner Matched RF Amplifiers. Stub tuners can be used to match sources and load to S 11 * and S 22 * of the RF BJT or FET Either open or short circuit stubs may be used

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'ELEC 412 RF & Microwave Engineering' - liam


Download Now An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

ELEC 412

RF & Microwave Engineering

Fall 2004

Lecture 19

ELEC 412 - Lecture 19

stub tuner matched rf amplifiers
Stub Tuner Matched RF Amplifiers
  • Stub tuners can be used to match sources and load to S11* and S22* of the RF BJT or FET
  • Either open or short circuit stubs may be used
  • When using short circuit stubs, place a capacitor between the stub and ground to produce RF path to ground – Do not short directly to ground as this will affect transistor DC biasing
  • High resistance /4 transformers or RFC’s may be used to provide DC path to transistor for biasing without affecting the RF signal path

ELEC 412 - Lecture 19

stub tuner matched rf amplifier
Stub Tuner Matched RF Amplifier

Series Resonant Ckt at Operating Frequency:

Short Ckt at Resonance, Open Circuit at DC

Stub tuners of two types:

Base-Side: Open Circuit Stub w/ Isolation from DC Bias Circuit Using RFC.

Collector-Side: RF Short Circuit Stub via By-Pass Capacitor

l/4 Transformer: Transforms Short Circuit at Resonance to Open circuit at BJT Collector Thus Isolating RC from RF Signal Path

Power Supplies Are Cap By-Passed and RF Input and Output are Cap Coupled

The BJT “Self-Bias” Configuration Is Shown Which Produces Excellent Quiescent Point Stability

ELEC 412 - Lecture 19

stub tuner matched rf amplifier4
Stub Tuner Matched RF Amplifier

Simpler method of bias isolation at BJT collector: CBP is RF short-circuit which when transformed by the Quarter-Wave Transformer is open circuit at the Single Stub Tuner and provides DC path for the Bias Network

ELEC 412 - Lecture 19

design strategy rf amplifiers
Design Strategy: RF Amplifiers
  • Objective: Design a complete class A, single-stage RF amplifier operated at 1 GHz which includes biasing, matching networks, and RF/DC isolation.

ELEC 412 - Lecture 19

design strategy rf amplifier
Design Strategy: RF Amplifier
  • Design DC biasing conditions
  • Select S-parameters for operating frequency
  • Build input and output matching networks for desired frequency response
  • Include RF/DC isolation
  • simulate amplifier performance on the computer

ELEC 412 - Lecture 19

design strategy approach
Design Strategy: Approach

For power considerations, matching networks are assumed lossless

ELEC 412 - Lecture 19

power relationships
Power Relationships

Transducer Power Gain

ELEC 412 - Lecture 19

stability of active device
Stability of Active Device

ELEC 412 - Lecture 19

stability of amplifiers
Stability of Amplifiers
  • In a two-port network, oscillations are possible if the magnitude of either the input or output reflection coefficient is greater than unity, which is equivalent to presenting a negative resistance at the port. This instability is characterized by

|Gin| > 1 or |Gout| > 1

which for a unilateral device implies |S11| > 1 or |S22| > 1.

ELEC 412 - Lecture 19

stability requirements
Stability Requirements
  •  Thus the requirements for stability are

and

  • These are defined by circles, called stability circles, that delimit |Gin| = 1 and | GL| = 1 on the Smith chart.

ELEC 412 - Lecture 19

stability regions stability circles
Stability Regions: Stability Circles
  • Regions of amplifier stability can be depicted using stability circles using the following:

Output stability circle:

Input stability circle:

ELEC 412 - Lecture 19

stability regions stability circles13
Stability Regions: Stability Circles

Where:

ELEC 412 - Lecture 19

different input stability regions
Different Input Stability Regions

Dependent on ratio between rs and |Cin|

ELEC 412 - Lecture 19

unconditional stability
Unconditional Stability

Stability circles reside completely outside |GS| =1 and |GL| =1. Rollet Factor:

ELEC 412 - Lecture 19

constant gain amplifier
Constant Gain Amplifier

ELEC 412 - Lecture 19

constant gain circles in the smith chart
Constant Gain Circles in the Smith Chart

To obtain desired amplifier gain performance

ELEC 412 - Lecture 19

gain circles
Gain Circles
  • Max gain Gimax =1/(1-|Sii|2) when Gi = Sii* ; gain circle center is at dgi= Sii* and radius rgi=0
  • Constant gain circles have centers on a line connecting origin to Sii*
  • For special case Gi = 0, gi= 1-|Sii|2 and

dgi = rgi= |Sii|/(1+|Sii|2) implying Gi = 1 (0 dB) circle always passes through origin of Gi plane

ELEC 412 - Lecture 19