Antenna synthesis
42
Antenna Synthesis ALBERTO DI MARIA AJAL.A.J – AP ECE DEPT UNIVERSAL ENGG COLLEGE MAIL: [email protected]
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HFSS complete antenna model Synthesized Array Factor
Transcript of Antenna synthesis
Antenna Synthesis
ALBERTO DI MARIAAJAL.A.J – AP ECE DEPT
UNIVERSAL ENGG COLLEGEMAIL: [email protected]
APP. A: PHASED ARRAY ANTENNA : SINGLE
ANTENNA
APP. A: PHASED ARRAY ANTENNA: MULTIPLE
ANTENNAS
APP. A: PHASED ARRAY ANTENNA: BEAM STEERING
MWP » MWP IN PAAS » SMART » CONCLUSIONS » QUESTIONS »
APP. A: PHASED ARRAY RECEIVE ANTENNA: DELAYS
T2T
MWP » MWP IN PAAS » SMART » CONCLUSIONS » QUESTIONS »
antenna 1
antenna 2
antenna 3
+
+
T
2T
ANSYS Conference & 27. CADFEM Users’ Meeting 2009 – Nov. 19 th - 7
ANSYS Conference & 27. CADFEM Users’ Meeting 2009 – Nov. 19 th - 8
ANSYS Conference & 27. CADFEM Users’ Meeting 2009 – Nov. 19 th - 9
ANSYS Conference & 27. CADFEM Users’ Meeting 2009 – Nov. 19 th - 10
ANSYS Conference & 27. CADFEM Users’ Meeting 2009 – Nov. 19 th - 11
HFSS complete antenna model
The model is electrically large and complex
ANSYS Conference & 27. CADFEM Users’ Meeting 2009 – Nov. 19 th - 12
HFSS complete antenna modelField Animation: Antenna, feed and enclosureVertical Polarization
ANSYS Conference & 27. CADFEM Users’ Meeting 2009 – Nov. 19 th - 13
HFSS complete antenna modelField Animation: Antenna, feed and enclosureHorizontal Polarization
ANSYS Conference & 27. CADFEM Users’ Meeting 2009 – Nov. 19 th - 14
HFSS complete antenna model
Simulations to compute Simulations to compute TTAA
15
16
Observable Sky
Antenna Synthesis
1. Basic principle for antenna synthesis
2. Line source synthesis (Fourier transform, woodward-lanson sampling)
3. Linear array synthesis (Fourier series, woodward-lanson sampling)
4. Low sidelobe synthesis (Dolph-Chebyshev, Taylor)
Synthesis Problems
Given affordable SLL, No. of elements, how to synthesize?
Ideal case: narrow beam, constant side-lobe envelope
Approaches: Dolph-Chebyshev, Taylor Line Source….
Secret behind: to synthesize a polynomial like pattern….
Examples of Chebyshev polynomials.
Dolph-Chebyshev Linear Array The Chebyshev polynomials:
)coshcosh(
)coscos(
)coshcosh()1(
)(1
1
1
xn
xn
xn
xT
n
n
1x11 x
1x
188)(
34)(
12)(
)(
1)(
244
33
22
1
0
xxxT
xxxT
xxT
xxT
xT )()(2)( 11 xTxxTxT nnn
Property used:
)][cos()cos( nTn
Chebyshev Polyminals
Symmetrically Excited Array
2/
1
2/)1(
10
]2
)12cos[(2
)cos(2
)(P
mm
P
mm
mi
mii
f
,mm ii
, P odd
, P even
)][cos()cos( nTn Property:
)(f is P-1 th polynomial of )2
cos(
)2
cos(0
xx Let
Choose appropriate to match the coefficients to those in Chebyshev polynomial, we obtain,
mi
)]2
cos([)( 01
xTf P
Chebyshev Polynomial Example
Synthesis StandardsSLL=-20log R (dB)
so ]cosh)1cosh[()( 01
01 xPxTR P
]cosh1
1cosh( 1
0 RP
x
1cos
1
1
optd
1
cos1
2
1
optd
Optimum spacing,
Broadside: Endfire:
)]1ln(1
1cosh[ 2
RR
P, where
Beamwidth and Directivity
In general, dHP h
1cos2 (broadside)
)1(cos 1
dHP h
(endfire)
, where
]cosh1
1cosh[
]2
cosh1
1cosh[
cos21
1
1
RP
RP
n
An approximation for the broadside:L
RHP
)2ln(
1
Beambroadening factor: )2ln(637.0866.0
)2ln(1
RR
bHP
HPR
RD
2
2
1
2
Directivity:
Synthesized Array Factor
Example No.2Optimum Spaced 10-Element, -30dB Side Lobe,Dolph-Chebyshev Endfire Array
Transformed Chebyshev Polynomial
Bionomial array
44 Two Dimensional Beam Steering Array
Antenna
Nonlinear
Delay LineBias Board
Power Divider
Tapering of Arrays
Tapering may not reduce sidelobes.
• The dish antenna theory: Tapering of the current distribution at the apperture leads to the side lobes decrease.
• This statement may not be true at the case of the arrays. Tapering is multiplication of the UV coverage with the tapering function. So at the image plane, it leads to the convolution of the untapered beam pattern with the Fourier transform of the tapering function. The convolution leads to the broadening of the main beam as well of the sidelobes. But the level of sidelobes may not be reduced, if the distance between the sidelobes is bigger than the width of the Fourier transform of the tapering function
Super directive arrays
35 / 42MWP » MWP in PAAs » SMART » Conclusions » Questions »
beamformerAntennaarray
RFfront-end to
receiver(s)
40x40gain
beam width
scan angle
optical
with amplitude tapering
8x8 8x1
36 / 42MWP » MWP in PAAs » SMART » Conclusions » Questions »
OBFN
electrical » optical optical » electrical
RF front-end
LNA
TIA
DM laser
chirp!
E/O and O/E conversions?• low optical bandwidth;• high linearity;• low noise
photo-diode
37 / 42MWP » MWP in PAAs » SMART » Conclusions » Questions »
mod.
OBFN
RF front-end
LNA
spectrum
frequency
TIA
electrical » optical optical » electrical
CW laser
10.7 GHz
12.75 GHz2 x 12.75 = 25.5 GHz
photo-diode
Conventional Antennas & Arrays
Antenna
Top View
Antenna Array
Top View
Omnidirectional Sectorized
WHY SMART ANTENNA ARRAYS ARE
SUPERIOR TO CONVENTIONAL ANTENNAS
Switched Beam System Adaptive Array
Antenna Array
Desired User
Interfering User
Antenna Array
Active Beam
Interference Rejection Comparison
Desired Signals
Co-channel Interfering Signals
TYPES (summary)
ANSYS Conference & 27. CADFEM Users’ Meeting 2009 – Nov. 19 th - 42
Thank you
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