Unclassified TN-2006-00539 Title 24 GHz Antenna Array Design with Suppressed Sidelobes

Technical note TN-2006-00539

Issued:07/2006

24GHz Antenna Array Design with Suppressed Sidelobes

M.Kastelijn

G.Dolmans(Editor)

Philips Research Eindhoven

Philips Restricted

c Koninklijke Philips Electronics N.V.2006

TN-2006-00539Unclassified

Unclassified TN-2006-00539

Keywords:car radar,antenna array,ultra wideband

Abstract:

Short-range car radar systems can provide safety and comfort features such as parking aid,pre-crash warning,change lane assistant,etc.These

radar systems create a safety belt around the car using transmission of ultra

wideband(UWB)24GHz signals.Regulations limit the level of radiation at

certain elevation angles to avoid interference or disturbance in the24GHz

band.

The specific goal of this research was:”Design a broadband antenna array at24GHz that exhibits side lobe suppression of35dB at angles>30◦

and has enough forward gain.”

TN-2006-00539Unclassified Conclusions:

The effects of tapering methods on the side lobe suppression are investigated.It is shown that by just using multiple antenna elements,the

specifications can not be met.

Space tapering and amplitude tapering of the antenna elements are explored.Amplitude tapering turned out to be the best choice for the design

of the array.However,transmission lines to feed the array increases the side

lobe level,with a minimum level of about-23dB.

The Chebyshev family of amplitude tapering functions is introduced.

Using this function and by exploiting aliasing of side lobes,specifications

can be met with only6antenna elements.

The actual tapering is done by exploiting the relatively high substrate losses of the transmission lines.For large amplitude ratios it is convenient

to fold the feed lines into a meander structure.To minimize the spurious

radiation of the feed network,the feed lines are moved to the third metal

layer(Signal3)and are shielded by a metal plane in the second metal layer

(Signal2).Thefinal design achieves a side lobe level suppression of-33.1

dB for the nominal frequency of24.7GHz.This meets the specifications

until Jan1st,2014.

Unclassified TN-2006-00539 Contents

1Introduction1

1.1Project Background (1)

1.2Project Requirements (2)

1.3Structure of the Report (2)

2Linear Arrays3

2.1Configuration (3)

2.2Radiation Pattern (4)

2.3Summary (6)

3The Array Factor8

3.1Relation between Array Function and Array Factor (8)

3.2Effects of tapering (10)

3.2.1Multiple elements (10)

3.2.2Space tapering (11)

3.2.3Amplitude tapering (15)

3.3Summary (18)

4Matlab Simulations19

4.1Capabilities of the script (19)

4.2First simulations and verification (19)

4.3Application of the script:designing space tapered arrays (24)

4.4Summary (26)

5Building Blocks of ADS Designs27

5.1Technology and Simulation Settings (27)

5.2The patches (27)

5.2.1Patch of50 with moulding layer (28)

5.2.2Patch of100 with moulding layer (28)

5.2.3Patch of50 without moulding layer (29)

5.2.4Patch of100 without moulding layer (30)

5.3The feed network (30)

5.3.1Feed network elements for layouts with moulding layer (31)

5.3.2Feed network elements for layouts without moulding layer (34)

5.4Summary (36)