The Schelkunoff-Smith Chart and Small Antennas

Schelkunoff-Smith Chart

Dipole Impedance and Power

• Schelkunoff's

Dipole Impedance

• Smith-Carter Chart
• Power Factor

The Art and Science of UWB Antennas, 2015, pp. 282-283

Small Antenna Gain

Dipole Impedance

Schelkunoff Smith Chart & Energy Flow

Space-Time Energy Flow

The Schelkunoff-Smith Chart,

Energy Flow & Small Antennas

How The Smith Chart Works

The Schelkunoff-Smith Chart & Small Antennas

• The Smith Chart: a useful tool for impedance matching
• The Schelkunoff-Smith Chart: a useful tool for understanding how small antennas work
• The Gain Relation: allows you to predict small antenna performance knowing only size and loaded Q.

Questions?

Hans G. Schantz, Principal Scientist, KC5VLD

Geeks and Nerds Corporation

hans.schantz@geeksandnerds.com

Hans G. Schantz,

Principal Scientist,

Geeks and Nerds Corporation

https://www.geeksandnerds.com

hans.schantz@geeksandnerds.com

Slides - check out: https://prezi.com/-xuawaznecdz/

https://gab.ai/aetherczar

https://twitter.com/aetherczar

Blog: http://aetherczar.com

Overview

Smith Charts:

• What are they?
• How do they work?
• What can they do?
• Example

Schelkunoff & the Dipole Fields:

• Impedance
• Time Domain Energy Flow
• Magnitude & Phase
• Power Factor,

Quality Factor,

& Gain

The Great Circle of Electromagnetism

• Interference
• Energy Velocity & Near-Fields
• The Great Circle
• Dirac's Big Mistake

Energy Flow in Harmonic Fields

• Phase Differences
• Energy Velocity

Schelkunoff & Dipole Impedance

The Smith Chart

Interference

Destructive Interference

• |E| goes to zero
• |H| doubles
• Electric energy becomes magnetostatic

Constructive Interference

• |H| goes to zero
• |E| doubles
• Magnetic energy becomes electrostatic

Fields exchange energy

• Waves go one way
• Fields go another way
• Even if orthogonally polarized!

"They [the dipole equations] are the most important equations in the theory and practice of antennas."

Schelkunoff & Friis, 1952

Energy Flow in Harmonic Fields

The "Great Circle" of Electromagnetism

Schelkunoff & Impedance

Energy Flow in Harmonic Fields

Dirac's Big Mistake

Hans G. Schantz,

"Energy Velocity

and Reactive Fields"

Phil Trans Roy Soc A

29 October 2018

https://doi.org/10.1098/rsta.2017.0453

Consider normalized fields with phase difference

• Same sign: forward motion
• Opposite sign: reverse motion

"Suppose we have a beam of light consisting of a large number of photons split up into two components of equal intensity. On the assumption that the intensity of this beam is connected with the probable number of photons in it, we should have half the total number of photons going into each component. If the two components are now made to interfere, we should require a photon in one component to be able to interfere with one in the other. Sometimes these two photons would have to annihilate one another, and other times they would have to produce four photons. This would contradict the law of conservation of energy. The new theory, which connects the wave function with probabilities for one photon, gets over the difficulty by making each photon go partly into each of the two components. Each photon then interferes only with itself. Interference between two different photons never occurs."

Sergei Alexander Schelkunoff

(1897-1992)

Match a UHF TV Antenna

Admittance & Matching