Patch Antenna Array

7/27/2019 Patch Antenna Array

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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.



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



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.



Values are in millimeters.



• 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



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.



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)



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









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



Return measurements for the Double –Antenna Array from

the Previous Slide



Radiation Pattern on E-plane and H-plane For the

Double - Antenna Array (transmitter side)



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 )



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.

Patch Antenna Array

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