Microstrip Patch Antenna Design
Understanding Patch Antenna Design
Patch antennas are the most widely used antenna type in modern wireless systems because they are flat, low-cost (PCB fabrication), conformal, and easily arrayed. Understanding the design parameters enables optimization for specific applications.
Patch Design Parameters
- Length (L): Approximately lambda_eff/2. Determines resonant frequency. Fine-tuned by trimming or simulation.
- Width (W): Affects radiation efficiency and impedance. Wider = lower impedance, more bandwidth.
- Substrate: Low-er (air, foam): wide bandwidth (10-20%), high efficiency. High-er (ceramic): compact but narrow bandwidth (2-5%).
- Feed: Inset feed, probe feed, aperture-coupled, or proximity-coupled. Each has different bandwidth and cross-pol characteristics.
Frequently Asked Questions
How do I design a patch antenna?
Choose substrate (er, thickness). Calculate L = c/(2f*sqrt(er_eff)) for resonance. Set W for desired impedance. Choose feed type. Simulate with EM solver (HFSS, CST). Iterate to tune frequency, match, and pattern.
How much bandwidth can a patch achieve?
Standard single-layer patch: 2-5% BW. Stacked patches: 15-30%. U-slot or E-shaped: 20-40%. Thick, low-er substrate maximizes bandwidth. At 5 GHz on 60-mil Rogers 5880 (er=2.2): about 5-8%.
Can a patch antenna do circular polarization?
Yes. Use a square patch with two feeds 90 degrees apart (dual feed CP). Or a single feed with perturbation (truncated corners, single feed at 45 degrees). Dual-feed provides better axial ratio bandwidth.