Experiment No.2
Title : ANTENNA
OBJECTIVE
●
Design of a microstrip patch antenna with microstrip feed.
●
To study input impedance matching of an antenna.
●
To study the radiation characteristics of an antenna.
THEORY
A Patch antenna consists of a flat rectangular patch of metal mounted over a dielectric slab
backed by sheet of metal called a ground plane. The patch antenna is convenient for
microwave frequencies, specifically on the 2.4-GHz band and higher. It consists of a plated
geometric form (the patch) on one side of a printed circuit board, backed up on the
opposite board side by a ground plane which extends beyond the dimensions of the
radiating patch. Rectangular and circular forms are the most common, but other shape for
example, a trapezoid—are sometimes used. Maximum radiation is perpendicular to the
board. A square half-wave patch antenna has a directivity of 7 to 8 dB. The dimension L is
approximately a half wavelength, calculated as half the free space wavelength (λ) divided by
the square root of the effective dielectric constant (ɛ) of the board material. It must actually
be slightly less than a half wavelength because of the fringing effect of the radiation from
the two opposite patch edges that are L apart and the ground plane.
As long as the feed is on the centerline, the two other edges don’t radiate. The figure shows
a microstrip feeder, which is convenient because it is etched on the board together with the
patch and other component traces on the same side.
PART A: SIMULATION
Layout of the microstrip line :
Substrate Details :
Substrate Material: RogerR04003
Calculation of Length and Width for Microstrip Line :
Dielectric Constant = 3.55
Dielectric Height, h=0.813 mm
Frequency of Operation, f = 10 GHz
Characteristic Impedance, Zo = 50 Ohm
Theta = 90 degree
Using these values in the Microstrip Line Calculator, the Length and Width have been
obtained as:
Length (L) = 4.5 mm and Width (W) = 1.82 mm
Plots of E and H Fields :
● E Field Plot is as per following;
●
H Field Plot is as per following;
Layout of Monopole Antenna;
Thickness t = 0.017mm
Height h = 0.813mm
Dielectric Constant = 3.55
Plots
S Parameter Plot
E Field
Monopole Radiation Pattern
At Phi = 0 Degree
At Phi = 90 Degree
3D Radiation Pattern, Polar Plot
Discussions and Conclusions
The primary focus was to simulate the S parameters of the Microstrip line and Monopole
Antenna and see how efficiently the impedance matching is taking place in terms of the
power reflected. Also, the E and H fields of both the Simulations were observed.
Reflection parameter, S11 indicates the efficiency of the antenna in terms of the power
reflected back due to impedance mismatch. A low S11 signifies good impedance matching
and indicates that most of the signal is being radiated rather than being reflected.
The observed S11 values confirm that the antenna was appropriately matched to the design
frequency of 1.8 GHz.
PART B: MEASUREMENTS
Monopole Antenna Photo
Observations
E plane: Copole
Angle (°)
S11value(dBm)
Normalised(dB)
Angle (°)
S11value(dBm) Normalised(dB)
0
-38.34
0
100
-42.7
-4.36
10
-41.46
-3.12
110
-40.34
-2
20
-42.34
-4
120
-39.59
-1.25
30
-44.18
-5.84
130
-40
-1.66
40
-46.46
-8.12
140
-41.66
-3.32
50
-49.35
-11.01
150
-42.71
-4.37
60
-51
-12.66
160
-42.56
-4.22
70
-46.24
-7.9
170
-42.71
-4.37
80
--42.72
-4.38
180
-43.37
-5.03
90
-42.16
-3.78
Radiation Pattern Plot
H Plane: Co-pole
Angle (°) S11value(dBm)
Normalised(dB)
Angle (°)
S11value(dBm)
Normalised(dB)
0
-43.36
0
100
-47.56
-4.2
10
-43.41
0.05
110
-46.68
-3.32
20
-42.88
0.48
120
-44.95
-1.59
30
-43.22
0.14
130
-43.16
0.2
40
-42
1.36
140
-46.45
-3.09
50
-41.62
1.74
150
-45.84
-2.48
60
-43.72
-0.36
160
-47.31
-3.95
70
-46.44
-3.08
170
-48.72
-5.36
80
-51.55
-8.19
180
-47.19
-3.83
90
-49.37
-6.01
Radiation Pattern Plot
Overall Discussions
In the context of a Microstrip Patch Antenna Lab experiment where scattering parameters
(S-parameters) were measured, the conclusion might be framed as follows:
Objective Summary: The primary objective of the experiment was to design and evaluate a
microstrip patch antenna, with a focus on measuring and analyzing its scattering parameters
(S-parameters), specifically the reflection coefficient (S11) and, if applicable, transmission
parameters (S21).
Design and Fabrication: The antenna was designed with specific dimensions and substrate
characteristics. The fabrication process involved creating the antenna on a dielectric
substrate with defined material properties.
Scattering Parameter Measurements:
Reflection Coefficient (S11): The measured S11 values indicated the efficiency of the
antenna in terms of power reflected back due to impedance mismatch. A low S11 value
(below -10 dB) signifies good impedance matching and indicates that most of the signal is
being radiated rather than reflected.
Transmission Parameters (S21): If S21 was measured, it would show the transmission
characteristics if the setup involved coupling between multiple antennas. In many cases, this
might be less relevant for a simple patch antenna analysis.
Results and Analysis:
Resonant Frequency: The resonant frequency observed from the S11 measurements should
closely match the designed resonant frequency. Any deviations might be attributed to
fabrication imperfections or substrate dielectric variations.
Bandwidth: The bandwidth can be inferred from the frequency range over which S11
remains below a certain threshold (e.g., -10 dB). This helps assess the operational range of
the antenna.
Impedance Matching: Effective impedance matching is reflected in the S11 results. Good
impedance matching is crucial for minimizing reflected power and improving antenna
performance.
Conclusion: The experiment demonstrated that the designed microstrip patch antenna
effectively met the targeted design specifications based on the measured scattering
parameters. The observed S11 values confirmed that the antenna was appropriately
matched to the designed frequency, with acceptable performance in terms of bandwidth
and reflection loss.