Project

Electromagnetic Waves

Project

Non-Foster Antennas

Overview

Work in assigned project groups.

The objective of this project is to simulate antenna bandwidth improvements using non-Foster circuits.

NOTE: Use the Project Report Template .

IN NO CASE may code or files be exchanged between students, and each student must answer the questions themselves and do their own plots, NO COPYING of any sort! Nevertheless, students are encouraged to collaborate in the lab session. 24

Non-Foster Antenna Bandwidth Improvement

We investigate the use of non-Foster Circuits having negative capacitance for improving antenna bandwidth
For reference, see:

"Non-Foster Matched Antennas for High-Power Applications," by Minu M. Jacob ; Daniel F. Sievenpiper.

More recent digital implementations are used in Digital Non-Foster Radio Architectures for wideband matching of electrically small antennas
For details on such radio design concepts, see:

Digital non-Foster circuits
Digital Non-Foster radio architecture for wideband matching of electrically small antennas

The project will be simulated in Keysight ADS
From a Linux terminal, Keysight ADS (Advanced Design System) should be available in the menu (Applications::ElecEngineering::KeysightAdvancedDesignSystem)
From a PC terminal, you must first open a remote Linux session, then proceed as for a Linux terminal
After ADS starts you should get a starting window similar to this (navigate into your apps/ads folder):
Load and run the pulse example as follows:
Download the 7zap archive as follows:

Download the 7zap archive rfDigRad_NonFosAnt_30jul2018a_wrk.7zads to your ads directory
Use MenuBar::File::Unarchive to extract the project into your ADS directory as follows

You should find a new directory rrfDigRad_NonFosAnt_30jul2018a_wrk created in apps/ads
Run ADS and open the new RFcourse2012_pulse1a_wrk workbook by double-clicking it

Go down through the directory tree to pulse1/schematic and double click that schematic file

and the following schematic should appear.

The circuit in the cyan circle below finds s-parameters of the antenna (Zant, S33)
The circuit in the yellow circle below obtains s-parameters of the passively-matched (inductor-matched) antenna (ZindMatch, S22)
The circuit in the blue circle below obtains s-parameters of the non-Foster (-40pF) matched antenna (ZnonFos, S11)

Fig 002

Double-click the MONOPOLE antenna (blue arrow above) and look at the variables in the pop-up menu.
Use the mouse to select the variables and observe the changing description at the bottom of the pop-up.

Double-click the "gear" icon (yellow arrow above) in the upper right of the window to simulate.
After simulation the plotted results should pop up in a new window
One plot is the s-parameters similar to below

FIg 003

Note the sharp dip in S22 (blue arrow above) at the center frequency of the passive match at 20 MHz
Adjust your non-Foster capacitor (-40 pF originally) so that the dip in S11 (red arrow above) is also at 20 MHz

Then, slide markers m1 and m2 to measure the bandwidth at the -6 dB points
Save this new plot for your report
Record the 2 frequencies and bandwidth for your report
Record the new value for your non-Foster capacitance (changed from the original -40 pf)
Then, slide markers m3 and m4 to measure the passive-matched antenna bandwidth (S22) at the -6 dB points

For the passive match you must be very careful to measure points on opposite sides of the "dip" in S22
Because the slope is so steep, you will need to pick the values closest to 6 dB that you can

Record the 2 frequencies and bandwidth for your report

Rerun the simulation one last time to make sure that your plot is for the final value of the capacitor

The second plot is the impedance, similar to below

Fig 004

Use your adjusted new value from above for your non-Foster capacitor (-40 pF originally)

Save this new plot for your report
Then, slide marker m5 to 20MHz to measure the real part of the antenna Zant at the tuned frequency
Then, slide marker m7 to 20MHz to measure the imaginary part of the non-Foster matched antenna ZnonFos at the tuned frequency (it should be near zero ohms!)
Record the measured values for your report

Save your work!

See report template below

Report Data

============================ WARNING !! ====================================
**** WARNING **** YOU MUST USE THE PROJECT REPORT TEMPLATE Below:

See the Project Report Template at bottom of this page
A well-written report/paper is EXPECTED
STRONGLY RECOMMEND that you read IEEE authorship series: How to Write for Technical Periodicals & Conferences
Clearly describe everything, including:

variables in block diagrams
variables in formulas
units of variables kHz, pF, nH, m, s,
all traces on plots
all curves on plots
all results in any tables

Minimum required data content for your report and demos

Required theory/formulas numbered as below:

(1) formula for Wheeler-Chu limit of Q=fo/B=1/(k a)^3 where a is the radius of smallest sphere enclosing antenna
(2) formula for Wheeler -Chu "k a" ...not (k a)^3 where "k a=2 pi fo a/c" and c is speed of light
(2) formula rearranging first formula to solve for bandwidth B in terms of k a (not in terms of Q)

Required figures:

Any illegible plots receive zero credit (must be able to read all numbers, axes, labels, curves, grids, titles, legends)
All plots must of professional quality as in IEEE papers

LEGIBLE schematic showing the inductor antenna impedance matching circuit as in Fig 002 (yellow circle only)
LEGIBLE schematic showing the non-Foster antenna impedance matching circuit as in Fig 002 (blue circle only)
LEGIBLE simulation showing s-parameters including your final non-Foster match as in Fig 003
LEGIBLEsimulation showing impedances including your final non-Foster match as in Fig 004

Required tabular data content:

Table I Inductively-Matched Antenna giving Wheeler-Chu Q and bandwidth with 3 columns: parameter, parameter value, and units

Row 1: monopole antenna length
Row 2: Wheeler-Chu "a" (equals monopole length)
Row 3: Wheeler-Chu "ka"
Row4: theoretical Wheeler-Chu "Q"
Row5: theoretical Wheeler-Chu bandwidth in Hz
Row6: measured 6-dB bandwidth in Hz for inductor-matched circuit (at -6 dB points of S22)

Table II Non-Foster Antenna Match giving ADS results with 3 columns: parameter, parameter value, and units

Row 1: the final value of your non-Foster capacitance (change to the -40 pf) in pF
Row 2: the final 6 dB bandwidth of your non-Foster match in MHz (at -6 dB points of S11)
Row 3: the 6 dB bandwidth of the passive match (inductor match) in MHz (at -6 dB points of S22)
Row 4: the real part of the antenna Zant at 20 MHz
Row 5: the imaginary part of your non-Foster matched antenna ZnonFos at 20 MHz

See report template below

NOTE ReportTemplate: Use the Project Report Template

YOU MUST ADD CAPTIONS AND FIGURE NUMBERS TO ALL FIGURES!!

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