Electromagnetic Waves
Project
Digital 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.
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!!
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