Transcript Slotted Waveguide Antenna

Slotted Waveguide Antenna
Generalized Design from 1-70 GHz
Anil Kumar Pandey
Array Antenna Design Flow in EMPro
Linear waveguide Slot array modeling in EMPro
using parameterize variable for all components
Slot array antenna Synthesis using python Script
1. Calculation of antenna design
parameters
2. Changing these parameters in
EMPro GUI hence Changing Antenna
CAD file as per specified Frequency
3. Setting FEM Simulation parameters
4. Starting FEM Simulation
Input Parameters
1. Operating Frequency
2. Number of Slots
Simulated
Data
How a Waveguide Antenna Works
Slotted antenna arrays used with waveguides are a popular
antenna in navigation, radar and other high-frequency systems.
A waveguide is a very low loss transmission line. It allows to
propagate signals to a number of smaller antennas (slots). Each
of these slots allows a little of the energy to radiate. Slot
impedance and resonant behavior for a single slot are
dependent on slot placement and size. Its exceptional
directivity in the elevation plane gives it quite high power gain.
The slotted waveguide has achieved most of its success when
used in an omnidirectional role To make the unidirectional
antenna radiate over the entire 360 degrees of azimuth, a
second set of slots are cut in the back face of the waveguide.
When looking straight at the face of the waveguide you will be
able to see straight through both slots. Unfortunately, unless a
lot of slots are used, the antenna becomes more like a
bidirectional radiator, rather than an omnidirectional.
Linear Array Sketch
Parameters of waveguide slot array design
Slot to Top
Slot length
Slot Offset
Length
Slot Width
Distance
from port
Wg_a
Various Linear Array Combinations
2.44 GHz
64 slots
32 slots
16 slots
N : No of Slots Variation
(F : Fixed)
13.2 GHz
30 GHz
No of slots and Frequency are
two variable input parameter .
Varying these two parameters
many combination of array
antenna can be designed
60 GHz
F : Operating Frequency
(N : Fixed)
Slot Array Design Formulas
lam_zero=300/FGHz
# Free space wavelength
WG_a= (lam_zero/2)+(lam_zero*0.2) # Auto calculation of broad (a) dimension of waveguide
WG_b = WG_a/2
# Height (b)of waveguide
PI=3.14
lam_cutoff=2*WG_a
lam_guide=1/sqrt(((1.0/lam_zero)**2)-((1.0/lam_cutoff)**2))
# Slot offset
G_2_slot=1.0/Nslots
New_G1=2.09*(lam_guide/lam_zero)*(WG_a/WG_b)*(cmath.cos(0.464*PI*lam_zero/lam_guide)-cmath.cos(0.464*PI))**2
New_Y=G_2_slot/New_G1
Soff=(WG_a/PI)*sqrt(abs(cmath.asin(New_Y)))
# Slot Lenght
Slot_wl=0.210324*G_2_slot**4-0.338065*G_2_slot**3+0.12712*G_2_slot**2+0.034433*G_2_slot+0.48253
Sl=lam_zero*Slot_wl
#Slot width
Sw=WG_a*0.0625/0.9
#Slot Spacing
Ss=lam_guide/2
# Distance from short ( end space)
S_top=lam_guide/4
#Estimated Performance
Gain=abs(10 * cmath.log10((Nslots/2) * lam_guide/lam_zero)) #dB
Beamwidth=50.7 * lam_zero / ((Nslots/2)*(lam_guide/2)) #degree
Working Model
This is generalized example of slot array antenna from 1 GHz to 70 GHz. This
example uses powerful feature of EMPro python scripting for slot array
parameters calculation and parameterize feature of EMPro to create
generalized example.
•Open the project in EMPro
•Double click synthesis script present in project
•Enter desired operating frequency and number of slots
•Run script, it will automatically calculate all design parameters, set
parameters in GUI and modified CAD file as per specified frequency and
launch FEM simulation
Other Tips
•If you don’t want to launch FEM simulation , comment below two lines in script
#setupSimulation(FGHz-1, FGHz+1, 25 )
#return empro.activeProject.addSimulationDataToProject(autoQueue)
Array Antenna Performance at 2.41 GHz
WAN: antenna for 2.44GHz, or channel 7
Slotted Waveguide 802.11b WLAN antennas
Gain-9.69 dBi
Simulation time- 22Min 47 sec
Unknown - 0.2 Million
Memory – 400 MB (Iterative)
Array Antenna Performance at 6 GHz
Simulation time- 32Min 41 sec
Unknown - 0.3Million
Memory – 400 MB (Iterative)
Gain-10.48 dBi
Array Antenna Performance at 27 and 60 GHz
Gain- 11.43dBi