Patch Antenna Design for Automotive Collision Avoidance

Overview of Technical Issues:

The patch antenna's radiating element exhibits insufficient directivity with excessive side lobe and back lobe radiation, causing reduced forward gain that limits detection range for collision avoidance, wasted RF power in unwanted directions, and increased vulnerability to electromagnetic interference from vehicle body reflections and onboard electronics; the goal is to optimize the radiation pattern for focused forward beam coverage with suppressed side lobes to achieve reliable target detection at required distances.

Solution directions generated for this problem

Problem Direction 1 :

ImproveAntenna directivity
VS
ConstraintAntenna physical size

Inspiration 1 : Cross-domain reference

Application Principle: #17 Another dimension (Dimensionality change)
Cross-domain applicability Assess applicability
Multibeam antenna comprising direct radiating array and reflector
Innovative Solution Refine solution

Vertically stacked multi-layer patch antenna with tilted parasitic directors for compact high-directivity radar

Exploit vertical dimension within bumper depth
How to solve :
  • Stack a driven patch layer at base with two parasitic director layers elevated at 0.15λ (1.9 mm at 24 GHz) and 0.30λ (3.8 mm) above using low-permittivity foam spacers (εr=1.05-1.1, Rogers PORON)
  • each layer 45×45 mm, total height 12 mm fits bumper depth
  • Tilt parasitic patches 15° forward relative to base patch plane using precision-molded dielectric wedges, creating phase-progressive wavefront that concentrates radiation into 30° beamwidth forward cone
  • Feed base patch via single coaxial probe at 0.35 patch-width offset for 50Ω match
  • parasitic coupling automatically achieved through vertical spacing—no additional feed network required, maintaining single-point excitation simplicity
Expected Effect : Directivity 13.2 dBi, side lobes <-18 dB, footprint 45×45×12 mm
Risk Control :
  • foam spacer compression under vibration altering layer spacing by ±0.2mm
  • parasitic tilt angle deviation beyond ±2° degrading directivity
  • temperature-induced dielectric constant shift in foam affecting coupling strength

Problem Direction 2 :

ImproveSide lobe suppression level
VS
ConstraintFeed network complexity

Inspiration 1 : Cross-domain reference

Application Principle: #3 Local quality
Cross-domain applicability Assess applicability
Beam forming antennas having dual-polarized dielectric radiating elements therein
Innovative Solution Refine solution

Spatially-graded dielectric substrate for passive side lobe suppression

Graded permittivity substrate suppresses side lobes without feed modification
How to solve :
  • Replace homogeneous PCB substrate with spatially-graded dielectric composite: center region εr=3.5–4.0, edge region εr=2.2–2.5, creating smooth radial gradient over 15–25mm transition zone to taper edge current distribution
  • Fabricate via co-fired ceramic layering or polymer-ceramic composite casting: stack three concentric dielectric zones (high-εr core, medium-εr middle, low-εr periphery) with thickness 1.6mm, bonding via thermal compression at 180–220°C, 2–5 MPa for 30 minutes
  • Maintain single-point coaxial probe feed at patch center with 50Ω impedance matching: probe height 1.2–1.5mm, position tolerance ±0.1mm, verified by vector network analyzer S11 < -15dB across 76–81 GHz band
Expected Effect : Side lobe suppression -22dB, feed unchanged, directivity 11–13dBi
Risk Control :
  • dielectric constant gradient uniformity ±0.15
  • interlayer bonding delamination risk
  • thermal expansion mismatch induced warping

Problem Direction 3 :

ImproveForward radiation gain
VS
ConstraintFeed network complexity

Inspiration 1 : Cross-domain reference

Application Principle: #6 Universality (Multi-functionality)
Cross-domain applicability Assess applicability
Integrated antenna elements, multi-array antennas, and their transmission and reception methods
Innovative Solution Refine solution

Self-impedance-matching patch geometry for integrated gain recovery

Design patch to perform both radiation and impedance matching
How to solve :
  • Adopt E-shaped patch geometry where the central slot and side arms inherently provide 50Ω impedance match and suppress surface wave spillage, eliminating external matching networks
  • Set slot width 0.8–1.2 mm and arm length 0.25λ to control current distribution for redirecting 3–4 dB spillage into main lobe
  • Feed via single microstrip line at optimized inset position (0.3–0.4 patch width from edge) to excite dual resonant modes that concentrate forward radiation
Expected Effect : Forward gain +3.5 dB, single-point feed, side lobe <-18 dB
Risk Control :
  • slot dimension tolerance ±0.05 mm
  • substrate εr variation ±0.1
  • inset feed position accuracy ±0.2 mm
Patsnap Eureka Solution