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:
- 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:
- 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:
- 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
- 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!!
Copyright © 2010-2019 T. Weldon
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