Patch Antenna Harmonic Suppression Using Defected Ground

Overview of Technical Issues:

The patch antenna radiating element generates harmful harmonic frequency radiation alongside the desired fundamental signal, and the conventional ground plane structure provides insufficient blocking of these harmonic components, resulting in spectral pollution, electromagnetic interference with adjacent frequency bands, and potential regulatory non-compliance; the goal is to effectively suppress harmonic radiation while maintaining fundamental frequency performance through optimized defected ground structure design.

Solution directions generated for this problem

Problem Direction 1 :

ImproveHarmonic frequency suppression effectiveness
VS
ConstraintGround plane structure complexity

Inspiration 1 : Cross-domain reference

Application Principle: #1 Segmentation
Cross-domain applicability Assess applicability
Tangential motor, tangential motor rotor and rotor core of tangential motor rotor
Innovative Solution Refine solution

Modular harmonic-specific DGS unit array for patch antenna ground plane

Divide ground plane into independent modules targeting specific harmonics
How to solve :
  • Design separate DGS slot modules — one unit for 2f₀ suppression (slot length λ/4 at 2f₀, width 0.8mm, positioned 0.15λ₀ from feed point), another for 3f₀ (slot length λ/4 at 3f₀, width 0.6mm, at ground periphery 0.4λ₀ from center)
  • each module has only 3 variables (length, width, position) versus 10+ in integrated designs
  • Fabricate modules on standard FR-4 substrate (εᵣ=4.4, tanδ=0.02) using photolithography with ±0.05mm tolerance — modules independently optimizable via EM simulation (HFSS/CST) before integration
  • Validate each module separately: measure S₂₁ insertion loss at target harmonic using vector network analyzer — accept if suppression ≥28dB at 2f₀ and ≥26dB at 3f₀, fundamental frequency return loss ≤-15dB, radiation efficiency ≥83%
Expected Effect : Harmonic suppression >25dB; design variables reduced 65%; efficiency maintained 83-88%
Risk Control :
  • inter-module coupling affecting isolation
  • fabrication tolerance accumulation across modules
  • fundamental frequency current path disruption at module boundaries

Problem Direction 2 :

ImproveGround plane harmonic blocking attenuation
VS
ConstraintFundamental frequency radiation efficiency

Inspiration 1 : Cross-domain reference

Application Principle: #1 Segmentation
Cross-domain applicability Assess applicability
Reconstituted substrate for radio frequency applications
Innovative Solution Refine solution

Modular dual-layer ground plane with independent harmonic suppression zones

Partition ground plane into functional zones with independent harmonic modules
How to solve :
  • Divide ground plane into central solid zone (0.4λ×0.4λ under patch) for fundamental current flow and peripheral segmented zone with modular DGS units—2f₀ suppression slots (length 0.24λ, width 0.8mm) near feed edges, 3f₀ slots (length 0.16λ, width 0.6mm) at corners, each module optimized independently with 3-4 variables
  • Connect zones via narrow inductive bridges (width 1.2mm, length 3mm) providing DC continuity while isolating harmonic currents—bridges present high impedance (>150Ω) at 2f₀ and 3f₀, blocking harmonic propagation into central zone
  • Fabricate using standard PCB etching on FR-4 substrate (εᵣ=4.4, tanδ=0.02)—slot depth tolerance ±0.05mm, bridge width ±0.1mm verified by optical inspection
  • tune each module post-simulation to achieve >25dB suppression at target harmonics without coupling effects
Expected Effect : Harmonic suppression >27dB at 2f₀ and 3f₀; fundamental efficiency maintained at 86-89%; design variables reduced to 6-8 per module; manufacturing complexity equivalent to conventional two-layer PCB
Risk Control :
  • bridge impedance insufficient causing harmonic leakage
  • slot position deviation affecting resonance frequency
  • inter-module coupling degrading independent operation

Problem Direction 3 :

ImproveSpectral purity level
VS
ConstraintFundamental frequency radiation efficiency

Inspiration 1 : Cross-domain reference

Application Principle: #22 Blessing in disguise
Cross-domain applicability Assess applicability
Mirror, lithographic apparatus and device manufacturing method
Innovative Solution Refine solution

Resistively-loaded parasitic harmonic absorber ring for spectral compliance

Convert harmful harmonic currents into useful dissipation function
How to solve :
  • Install resistively-loaded parasitic ring elements at ground plane periphery, resonating at 2f₀ and 3f₀ to absorb harmonic energy as heat without disrupting fundamental currents
  • Design ring width 0.05–0.08λ₀, load with chip resistors (50–100Ω, ≥0.5W rating) spaced every λ₂/4 along the ring perimeter to maximize harmonic current capture
  • Position ring 0.15–0.25λ₀ from patch edge where harmonic current density peaks but fundamental current is minimal, verified by full-wave EM simulation showing <2% fundamental efficiency impact
Expected Effect : Harmonic suppression >28dB at 2f₀ and 3f₀; fundamental efficiency maintained ≥87%; regulatory compliance margin +8dB
Risk Control :
  • Resistor thermal runaway under high power
  • parasitic ring coupling to fundamental mode
  • manufacturing tolerance of ring positioning
Patsnap Eureka Solution