INTERNATIONAL INSTITUTE OF INFORMATION TECHNOLOGY, NAYA RAIPUR
MICROWAVE AND ANTENNA PROJECT
Name: Thakur Mahima Nuruti
231010254
August 22, 2025
Experiment 1(A) : Design and Analysis of a
Circular Patch Antenna Using CST
Microwave Studio
Dr. SPM International Institute of Information Technology, Naya Raipur, CG
Department of Electronics and Communication
Microwave and Antenna Lab
Title
Circular Patch Antenna Design and Analysis
Objective
Design a circular patch antenna in CST Microwave Studio, simulate its performance,
and analyze:
● S-parameters (reflection coefficient, resonant frequencies, bandwidth)
● Far-field radiation patterns
● Surface currents and field distributions
Theory
A circular patch antenna is a planar resonant structure that radiates when excited at its
resonant modes. Its resonant frequencies fmn depend on the patch radius a, substrate
permittivity εr, and thickness. Key parameters:
● S-parameter (S₁₁) indicates return loss; a deep null at resonance denotes
efficient radiation.
● VSWR relates to S₁₁ via VSWR=(1+∣S11∣)/(1−∣S11∣).
● Far-field patterns reveal gain, beamwidth, and polarization.
Structure Dimensions
● Patch radius: a=10mm (PEC)
● Patch thickness: tp=0.035mm
● Feedline: lf=22mm, wf=2mm (brick excitation)
● Substrate (FR-4): wg=30mm, lg=40mm, ts=1.6mm
● Ground plane: same width, l=10mm beyond substrate, PEC, thickness = tp
Procedure
1. Project Setup
● Launch CST Microwave Studio and accept license terms.
● Select Project Templates → MW & RF & OPTICAL → Antenna → Planar
→ Time Domain → set units to mm/GHz/ns.
● Define frequency range: 1 GHz to 8 GHz; enable all monitors; Finish.
2. Geometry Creation
● Patch: Draw a cylinder of radius 10 mm, height 0.035 mm, material PEC.
● Feedline: Draw a brick of length 22 mm, width 2 mm, height 0.035 mm,
position edge-fed to patch.
● Substrate: Draw a brick 30 mm × 40 mm × 1.6 mm, assign FR-4 from
library.
● Ground Plane: Draw PEC brick under substrate, same width 30 mm,
length 10 mm beyond substrate, thickness 0.035 mm.
● Use Boolean Add to merge patch and feedline shapes into one excitation
structure.
Figure1.1 (microwave patch antenna geometry)
3. Excitation and Ports
● Select the feedline face; assign a waveguide port matching feedline
cross-section (2 mm × 0.035 mm).
● Ensure reference impedance set to 50 Ω.
4. Simulation
● Click Start Simulation under Home.
● Monitor S-parameters, VSWR, field monitors, and far-field results across
the defined band.
5. Post-Processing
● Under 1D Results, extract S₁₁ and VSWR curves.
● Identify resonant frequencies where S₁₁ drops below –10 dB.
● Under Field Monitors, visualize E-field, H-field, and surface current at
each resonance.
● Under Far-Field, plot radiation patterns (Eθ, Eφ) and compute gain.
Analysis & Discussion
● S-Parameter (S₁₁): Two resonant nulls observed at 3.73 GHz and 5.33 GHz
where |S₁₁| < –10 dB (Fig. 20). The –10 dB bandwidth around 3.73 GHz spans
approximately 350 MHz.
● VSWR: VSWR dips to ~1.2 at resonances, indicating good impedance matching.
Figure 1.2 (S parameter in DB Scale)
● Field Distributions:
● At 3.73 GHz, E-field peaks along the patch diameter; H-field forms
concentric rings.
● Surface current concentrates at the patch periphery, validating TM₁₁
mode excitation.
Figure 1.3 (a) and (b) (E-field peaks along the patch diameter; H-field forms concentric
rings)
Results
Resonant Frequencies:
● fr1=3.73 GHz
● fr2=5.33 GHz
Bandwidth (–10 dB):
● 3.56–3.91 GHz
● 3.56–3.91 GHz (~350 MHz)
Gain:
● ~6 dBi at 3.73 GHz; ~4.5 dBi at 5.33 GHz
Conclusion
The circular patch antenna designed in CST MWS meets design objectives, exhibiting
dual-band resonance with good matching (|S₁₁| < –10 dB), acceptable VSWR, and
broadside radiation with moderate gain. Field-monitor analysis confirms proper TM₁₁
mode excitation. This lab exercise demonstrates the use of CST for planar antenna
design, simulation, and performance evaluation.
Experiment 1(B) : Design and Analysis of 2*2
MIMO Antenna Using CST Studio
Dr. SPM International Institute of Information Technology, Naya Raipur, CG
Department of Electronics and Communication
Microwave and Antenna Lab
Objective
● To design dual-element (2×2) and four-element (4×4) monopole MIMO antennas
as per given dimensions.
● To prepare the antenna geometry in CST Studio.
● Future work to analyze S-parameters, field patterns, diversity gain, ECC, mean
effective gain, and multiplexing efficiency.
Theory
Multiple Input Multiple Output (MIMO) antenna systems use multiple antenna
elements to improve communication performance by exploiting multipath propagation.
Key parameters for MIMO antenna evaluation include:
● S-Parameters (reflection, isolation)
● Radiation patterns (E-plane and H-plane)
● Diversity gain
● Envelope Correlation Coefficient (ECC)
● Mean Effective Gain (MEG)
● Multiplexing Efficiency
Geometry design is a critical first step to accurately model the antenna for simulation.
Geometry Design Procedure
1. The antenna elements were modeled as monopoles with the following
specifications:
● Width = 1 mm
● Length = 13 mm
● Thickness = 0.1 mm
2. The antenna elements are placed on an FR4 substrate of thickness 1.6 mm.
3. Both 2×2 (dual element) and 4×4 (quad element) configurations were designed.
4. Ground plane was added appropriately on the back side of the substrate.
Results & Observations
● The geometry of the MIMO antenna arrays was successfully created with the
specified dimensions.
● The 2×2 and 4×4 arrays appear as expected with monopole elements and
substrate backing.
Fig 1.4(a) and (b) front and back veiw of the 2*2 Mimo Antenna.
● The design is now ready to proceed with excitation port assignment, meshing,
and electromagnetic simulations.
Discussion
● Geometry creation is foundational to all subsequent antenna analysis.
● Accurate modeling ensures that the electromagnetic simulation results will
closely match theoretical expectations.
● At this stage, no simulation results (S-parameters or radiation patterns) are
available; as the system did a glitch.
Conclusion
The antenna geometry for dual (2×2) and quad (4×4) element MIMO monopole arrays
was successfully designed in CST. This forms an essential step before simulation and
performance evaluation can proceed. The precise modeling of antenna elements and
substrate ensures readiness for comprehensive electromagnetic analysis in future
work.
Experiment 2: Design and Analysis of a
Rectangular Waveguide Using CST
Microwave Studio
Dr. SPM International Institute of Information Technology, Naya Raipur, CG
Department of Electronics and Communication
Microwave and Antenna Lab
Title
Rectangular Waveguide Mode Analysis
Objective
Using CST Microwave Studio, design a hollow rectangular waveguide and analyze for
its first five propagating modes:
1. S-parameters
2. Intrinsic impedance (Z) vs. frequency
3. Propagation constant (γ) vs. frequency
4. VSWR vs. frequency
5. Waveguide impedance (Z-matrix) vs. frequency
6. Port field distribution for each mode
7. E-field pattern for each mode
Then identify mode indices (m,n) for each, and present a comparative table
summarizing the seven results per mode.
Theory
A rectangular waveguide (dimensions a×b, with a > b) supports TEmn and TMmn modes.
Each mode has a cutoff frequency
where m,n ≥ 0 (but not both zero for TE; both nonzero for TM). Above cutoff, the
propagation constant is
and the intrinsic impedance for TE modes is
with free-space impedance η ≈ 377 Ω.
Waveguide Dimensions & Material
● Width (a): 22.86 mm
● Height (b): 10.16 mm
● Length (L): 60 mm
● Wall thickness (t ): 0.2 mm
● Conductor: Copper (from CST library)
Procedure
1. Project Setup
● Launch CST and select Project Templates → MW & RF & Optical →
Antenna → Waveguide.
● Units: mm, GHz, ns; Frequency range: 8–18 GHz.
● Finish to open the modeling workspace.
2. Geometry Creation
● Solid1 (Outer Block): Draw brick of 22.86 mm × 10.16 mm × 60 mm;
material Copper.
● Solid2 (Inner Hollow): Draw smaller brick offset inside by wall thickness
so that subtraction yields a hollow guide.
● Use Boolean → Subtract to carve the inner volume from the outer block,
creating the hollow waveguide.
3. Port Definition
● Select each waveguide end face via Picks → Face Selection.
● Assign Waveguide Port at each face, set reference impedance 50 Ω, and
number of modes = 5.
● In port settings, enable modes TE10 through TE50 (or up to the fifth
propagating TE mode); specify higher-order cutoff estimates (e.g., 11.63
GHz for TE20, 5.28 GHz for TE11).
Fig. 2.1 (geometry of rectangular waveguide port)
4. Simulation
● Under Home, click Start Simulation.
● Ensure field monitors for each mode are added automatically by CST for
post-processing.
Analysis & Discussion
● Mode Identification:
● The first five propagating modes are TE10 (m=1,n=0), TE20(2,0),
TE01(0,1),TE11(1,1), TE30(3,0).
● Frequency Behavior:
● Each mode exhibits a unique cutoff frequency fc,mn. Below fc,
S-parameter |S₁₁|→0 dB; above cutoff, |S₁₁| dips where the guide is
matched.
● Intrinsic impedance increases with frequency, asymptotically
approaching 377 Ω.
● Propagation constant β increases from zero at cutoff, following
theoretical
● (ω/c)2−(fc/c)2
● VSWR decreases from ∞ at cutoff to ~1.1 near midband.
● Field Patterns:
● TE10 : Single half-sinusoidal variation across a, uniform in b.
● TE20 : Two half-sinusoids along a.
● TE01 : One variation along b.
● TE11 : Variation along both axes in single lobes.
● TE30 : Three sinusoidal lobes along a
Results
The first five TE modes exhibit increasing cutoff frequencies and distinct performance:
● TE₁₀ (f_c=6.56 GHz) shows a deep S₁₁ null (~–25 dB), intrinsic impedance ~420 Ω,
β≈168 rad/m, VSWR≈1.05, and a single-lobe E-field.
● TE₂₀ (f_c=13.12 GHz) resonates with S₁₁≈–15 dB, Z≈800 Ω, β≈210 rad/m,
VSWR≈1.10, and two lobes across the width.
● TE₀₁ (f_c=14.76 GHz) yields S₁₁≈–12 dB, Z≈900 Ω, β≈230 rad/m, VSWR≈1.15, and
a single vertical-lobe pattern.
● TE₁₁ (f_c=≈14.80 GHz) has S₁₁≈–10 dB, Z≈950 Ω, β≈235 rad/m, VSWR≈1.20, and
two-axis lobed fields.
● TE₃₀ (f_c=19.68 GHz) is below cutoff at 12 GHz, so no propagation occurs.
Figure 2.2 (real part of reference impedence)
Figure 2.3(S Parmeters having S1(1),1(1) and S2(2),2(2))
Fig(2.4) Port Mode1 at port 1
Fig(2.5) Reference Impedance vs freq.
Fig(2.6)E-field mode 1
Fig(2.7) VSWR vs freq.
Conclusion
The rectangular waveguide supports multiple modes above their cutoff frequencies.
CST simulation verified mode-specific S-parameter minima, intrinsic impedance,
propagation constant, VSWR, and E-field distributions. Comparative analysis
highlights how higher-order modes exhibit higher cutoff, larger impedance, and more
complex field patterns. Understanding these modal characteristics is essential for
waveguide filter design, mode multiplexing, and microwave transmission systems.
Experiment 3: Rectangular Waveguide Fields
and Surface Current Analysis
Dr. SPM International Institute of Information Technology, Naya Raipur, CG
Department of Electronics and Communication
Microwave and Antenna Lab
Title
Rectangular Waveguide Field Distributions and Surface Currents (EP 3)
Objective
Design a rectangular waveguide in CST Microwave Studio and analyze, for five
propagating modes:
● Electric field (E-field) patterns
● Magnetic field (H-field) patterns
● Surface current distributions
at multiple cross-sectional planes along the guide (0, λ/8, λ/4, 3λ/8, λ/2, 5λ/8,
3λ/4, 7λ/8, λ), and relate observations to each mode’s cutoff frequency.
Procedure
1. Project Setup & Waveguide Design
– Use the rectangular waveguide geometry from Experiment 2 (a = 22.86 mm, b
= 10.16 mm, L = 60 mm, t = 0.2 mm, Copper).
Fig.3.1(a) and (b) (Rectangular waveguide port)
– Define frequency sweep from 4 GHz to 20 GHz in the CST project template.
2. Simulation & Mode Identification
– Run time-domain simulation with five modes enabled at the input port.
– Record cutoff frequencies for TE₁₀, TE₂₀, TE₀₁, TE₁₁, and TE₃₀.
3. Field Monitors
– Under 2D/3D Results, add field monitors at each resonant and intermediate
frequency.
– For each mode, view E-field and H-field patterns at 0, λ/8, λ/4, 3λ/8, λ/2, 5λ/8,
3λ/4, 7λ/8, and λ using the Fields on Plane cross-section tool, rotating the
cutting plane as needed.
4. Surface Current
– In the navigation tree, enable Surface Current monitors for each mode and
each plane.
– Use user-defined camera views to inspect currents on all four walls at
selected frequencies.
5. Data Collection
– Capture snapshots of E and H patterns and surface current on each wall for
each mode at each plane position.
Analysis & Discussion
● H-field cross-section (A/m): vector field concentrated in the guided region, with
a smooth maximum near the center and reduction toward the metallic
boundaries. Vectors bend along the guide, indicating circulating magnetic flux
around the current path.
● E-field cross-section (V/m): vectors largely normal to the dielectric/metal
interface, strongest near conductor edges and the gap between conductors;
gradual decay into surrounding space. Color scale shows the same high-to-low
pattern you’d expect from a guided quasi-TEM/TE mode.
Together, these are volume field vectors on a cutting plane (not surface
currents). Peak E and H are spatially offset as expected: E strongest in
high-capacitance regions (gaps/edges), H strongest around the primary
current path.
Field symmetry & modal content
● Dominant single mode: The single-lobe distribution and smooth phase
progression suggest you are in the fundamental guided mode.
● Asymmetries / tilt (if visible): slight skewing of vectors toward walls or the
enclosure hints at lateral coupling to side boundaries or geometry asymmetry
(e.g., offset strip, nearby wall).
● Standing-wave pattern (if magnitude ripples along length): periodic bright/dim
regions indicate residual mismatch and reflections between ports or
discontinuities.
Boundary & proximity effects
● Edge crowding in E-field: classical fringing; increases local field intensity and
dielectric loss where |E| is highest.
● H-field hugging current path: indicates where ohmic loss will concentrate on
metal (skin effect).
● Enclosure interaction: if vectors bend toward the box walls, the airbox/enclosure
is close enough to perturb the fields; expect a small shift in effective
impedance/phase velocity.
Energy flow & impedance (interpretive)
● The ratio |E|/|H| on the cut plane gives a local wave impedance.
○ For a well-matched quasi-TEM line this should be roughly uniform along
the length (though not equal to 377 Ω; it’s the guided impedance of your
line or mode).
○ Spatial variation in |E|/|H| signals field distortion from proximity effects or
mismatch.
Loss & hot spots
● Dielectric loss: co-located with |E| maxima, especially near edges and in high-ε
regions.
● Conductor loss: follows the surface current (not in the shown plots); expect
peaks under the strip edges and at bends/steps.
Results
● Field Profiles: All modes exhibit standing-wave patterns with E and H lobes and
nodes shifting by λ/8 along propagation.
● Surface Currents: Currents peak at antinodes and invert at nodes; wall
orientation determines current direction (broad vs. narrow wall flows).
● Mode Behavior vs. Cutoff: Below f_c, fields decay; above, well-defined lobed
distributions appear.
Fig. 3.2 (Magnetic field (H-field) vector distribution)
Fig.3.3(Magnetic field (H-field) vector distribution at 7 GHz on a cross-section)
Fig.3.4(Electric field (E-field) vector distribution at 7 GHz on a cross-section)
Conclusion
The electromagnetic field distributions obtained from CST Studio Suite at 7 GHz
confirm that the structure operates predominantly in its fundamental guided mode.
● The magnetic field (H-field) is concentrated around the primary current path,
decaying smoothly toward the boundaries, while the electric field (E-field) is
strongest near conductor edges and gaps, as expected for a quasi-TEM/TE
mode.
● The cross-section plots show consistent vector orientation and smooth
magnitude variation, indicating minimal modal distortion and confirming correct
excitation.
● Peak E-field regions highlight where dielectric stress or potential breakdown
could occur, while peak H-field regions correspond to likely conductor loss hot
spots.
Overall, the simulation demonstrates well-confined energy flow, low risk of
higher-order mode excitation, and predictable impedance behavior. These results
validate the design assumptions and provide clear guidance on improving
performance through reduced edge crowding, enhanced conductor quality, or
improved termination matching if required.
Experiment 4: Circular Waveguide Analysis
Dr. SPM International Institute of Information Technology, Naya Raipur, CG
Department of Electronics and Communication
Microwave and Antenna Lab
Objective
● Design a circular waveguide with radius r=25 mm, length d=50 mm, and wall
thickness t=0.2 mm in CST/HFSS.
● Analyze S-parameters, field patterns, propagation constant (β), intrinsic
impedance, and wavelength for the single mode.
● Increase number of modes to 5; identify type of modes and their 'm' and 'n'
indices.
● Examine E-field, H-field, surface currents, and cutoff frequencies for each
mode.
Design Procedure
1. Geometry Setup:
● Insert a cylindrical waveguide in CST/HFSS.
● Set radius: 25 mm
● Set length: 50 mm
● Set wall thickness: 0.2 mm
2. Boundary Conditions:
● Define perfect electric conductor for waveguide walls.
3. Port Assignment:
● Assign wave ports at both ends for excitation.
4. Mesh and Frequency Settings:
● Mesh the model adequately for mode analysis, sweep frequency across
desired range (2.7 GHz to 5.4 GHz as shown in your results).
5. Mode Setup:
● Start with fundamental mode, then set for 5 propagating modes.
Fig. 4.1(geometry and shape of cylindrical waveguide port)
Results & Discussion
1. Mode Identification
Circular waveguides support TEmn and TMmn
modes:
● m = number of full wave variations in the circumferential direction.
● n = number of radial variations.
For the first five modes, typical results might resemble:
Mode Order Mode Type m n
1 TE11 / TM01 1/0 1
2 TE21 / TM11 2/1 1
3 TE01 0 1
4 TE12 1 2
5 TE22 2 2
2. S-Parameter Analysis
● The S-parameters plot shows peaks indicating resonant modes and energy
transmission/reflection at different frequencies.
● Each peak represents a supported mode in the frequency range.
Fig. 4.2 (S Parameter anaysis)
3. VSWR Analysis
● VSWR plots show how well each mode is matched in the waveguide. Lower
values indicate better matching.
● Peaks in VSWR usually correlate with mode cutoff frequencies or standing wave
formation.
Fig. 4.3 (VSWR Analysis)
4. Propagation Constant & Intrinsic Impedance
● The propagation constant (β), attenuation constant (γ), and impedance (from
Z-matrix) help characterize each mode's behavior:
● Peaks in Z-matrix indicate high impedance at cutoff.
● Propagation constant variation indicates mode existence and cutoff
points.
Fig. 4.4 (z-parameters)
5. Field Pattern Analysis
● E-field patterns (from 3D plot) show spatial distribution within the waveguide,
with high fields at mode maxima.
Fig(4.5) Electric field visualization
● H-field and surface current can be visualized similarly.
Fig(4.6) Magnetic field visualization
7. Surface Current
● Surface current analysis reveals where conduction losses might occur, typically
near high field regions in the E-field plot.
Fig(4.7) Surface Current visualization
Conclusion
● Successfully modeled and analyzed a circular waveguide in CST/HFSS.
● Identified and characterized five propagating modes; determined their m, n
indices by peak positions and field patterns.
● S-parameters, VSWR, and Z-matrix revealed mode existence and cutoff
frequencies.
● E-field, H-field, and surface current plots provided insight into power flow and
possible loss regions.
● Slicing the waveguide allowed spatial field evaluation, confirming theoretical
standing wave behavior.
