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7/27/2019 Patch Antenna Array
http://slidepdf.com/reader/full/patch-antenna-array 1/13
24 GHz Patch Antenna Array
• Xu Feng et al. simulated double-antenna architecture( for transmitting and
receiving on a single board) consisting of 84 elements demonstrating 60 %
efficiency and 26.5 dB gain [1].We can fabricate a single-antenna system using
a similar design.
Main Source:
“K-Band Micro- strip Antenna Array Applied in Anti- collision Radar” see reference [1] on last page of the slides.
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Patch Element Design Equations
Width of patch
Patch length along which the current flows
Change in patch length, b, due to fringing
fields which makes the Patch appear longer
Effective substrate dielectric constant,
h is the height of the substrate
feeding point b
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Determining the Inset Feeding Point Length , l
• is the patch resistance that is required to match the feeding
line’s resistance to prevent loss of power due to reflection. is
the resistance seen at the edge of the patch and is constant.
Center of patch, b/2,
Rin
= 0 ohms
• The patch resistance
decreases from maximum at
the edge to zero at the center.
Thus, the resistance can be
controlled by inset feeding,
where the feed line is placed
at a specified location
between the center and edge
of the patch.
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Values are in millimeters.
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• is the wavelength in free space, [2] used 0.73 and reported 60% efficiency
and 21.25 dB gain with return loss less than -14dB in a 48 element array system.
The authors of [1] used 4.35 mm.
Distance Between Patches on Substrate
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Feeding Network
50 Ω coaxial cable is
connected at point o .
57.6Ω
100Ω
• 100Ω transmission lines feed the patches. Quarter wave transformers ( 58.5 Ω, 50 Ω,
and 57.6 Ω ) are used to achieve the impedance matching.
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Quarter –Wave Transformer
• The quarter-wave transformer has a length of . The characteristic
impedance Z0 of the transformer required to match two impedances Z1 and
Z2 is calculated as follows:
•The following equation relates the width w of the microstrip quarter-
wave transformer and its impedance:
• Therefore, the width of the line can be determined once we know the
required transformer impedance which is found from the top equation.
(5)
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Determining the Widths of Quarter-Wave transformers
• Online microstrip line calculator is used to calculate the transformers’ widths
( this was not provided in [1] ):
http://www.microwaves101.com/encyclopedia/calmstrip.cfm
http://www1.sphere.ne.jp/i-lab/ilab/tool/ms_line_e.htm
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84 Element Array Used in [1]
• This double- antenna array is
designed for vehicle radar
with a range of 200m.
The gain is 26.5dB, -10dB
bandwidth is 1GHz from
23.6GHz to 24.6GHz,3dB beamwidth in azimuth
(E- plane )is 60 and
in elevation ( H-plane)
is 180. [1]
• A suggestion might be to fabricate a 2*2,4*4, or 8*8 single -antenna array
and measure the response oppose to the 14*6 double- antenna array above.
transmitter Receiver
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Return measurements for the Double –Antenna Array from
the Previous Slide
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Radiation Pattern on E-plane and H-plane For the
Double - Antenna Array (transmitter side)
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Suggestion:
• Fabricate a 1*1( for testing ?), 2*2,4*4, or 8*8 single -
antenna array with the parameters provided in table 1 and 2.
Results should be similar to [1] but with lower gain and
directivity. This should be adequate for us since we only
need 10 m range, whereas [1] was designed for 200m.
• (Note 2*2 array do not require quarter-wave transformers )
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References
[1] X. Feng, C. Xu, and W. Xin'an, “K-band micro-strip antenna array applied in
anti-collision radar,” inProceedings of the IEEE 12th International Conference onCommunication Technology (ICCT '10), pp. 1240 –1243, November 2010.
[2] M. Siovic, B. Jokanovic and B. Kolundzija, "High efficiency patch antenna for 24
GHz anticollision radar," in Telecommunications in Modern Satellite. Cable and
Broadcasting Services, 2005. 7th International Conference on, 2005, pp. 20- 23
vol.