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Calculators / Microstrip Antenna
Microstrip Antenna
Calculator
Calculate patch width, patch length, effective dielectric constant, and fringing effect for a rectangular microstrip patch antenna on any PCB substrate. Designed for PCB antenna engineering using the Bahl & Trivedi transmission-line model.
Radiating Patch
Substrate (εr)
Fringing Fields
⚙ Microstrip Patch Engine
Design frequency for patch resonance
Common PCB: 0.8, 1.0, 1.6, 3.2 mm
FR4 ≈ 4.4, Rogers RO4003C ≈ 3.55, PTFE ≈ 2.1
FR4 ≈ 0.02, RO4003C ≈ 0.0027, PTFE ≈ 0.0002
Advanced Parameters
mm
1 oz copper = 0.035 mm, 2 oz = 0.070 mm
Edge: Zin≈200–300 Ω. Inset: tunes to 50 Ω.
Inset depth y₀ calculated for this target
×h
Recommended: ≥3×h border around patch
Calculated Results
Patch Width (W)
—mm
Width of radiating element
Patch Length (L)
—mm
Length after fringe correction
Eff. Permittivity (εreff)
—
Accounts for fringing fields
Fringing Extension (ΔL)
—mm
Per side (total 2ΔL subtracted)
Fringe effect (ΔL / h)
—
Effective Length (Leff)—
λ in free space—
λ in substrate (λg)—
Radiation Resistance (Rr)—
Quality Factor (Q)—
Bandwidth (VSWR<2)—
Gain (approx.)—
Input Impedance Zin—
Enter values above to calculate.
📖 PCB Design Theory
A microstrip patch antenna is a thin metallic patch on a grounded dielectric PCB substrate. It resonates at λg/2, where λg is the guided wavelength in the substrate medium.
Step 1 — Patch Width
W = c / (2fr · √((εr+1)/2))
Optimises radiation efficiency vs width.
Step 2 — Effective εr
εreff = (εr+1)/2 + (εr-1)/2 · (1+12h/W)^−½
Fringing fields partially extend into air → εreff < εr.
Step 3 — Fringing Effect (ΔL)
ΔL = 0.412·h · (εreff+0.3)(W/h+0.264) / ((εreff−0.258)(W/h+0.8))
Hammerstad (1975). ΔL is subtracted from each end: L = Leff − 2ΔL.
Step 4 — Patch Length
L = c / (2fr · √εreff) − 2ΔL
📡 PCB Cross-Section & E-Field Viewer
Live Preview
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◉ Geometry scales with εr and h
View Mode
εr sweep
4.4
1.0 (Air)12 (Ceramic)
h/W ratio
0.10
Cross-Section
ℹ
PCB Design Insights
Enter frequency and substrate parameters to see PCB design insights.
Common Applications
WiFi & Bluetooth PCB
2.4 / 5 GHz patches on FR4 for IoT modules, routers, access points, and wearable devices.
GPS / GNSS Receiver
1.575 GHz (L1) ceramic-substrate patches. High-εr substrate reduces patch size for compact PCB integration.
5G mmWave Arrays
Patch arrays at 28/39 GHz on Rogers low-loss substrates for 5G base stations and CPE devices.
Automotive Radar
24/77 GHz patches on PTFE or Rogers substrates for ADAS radar, blind-spot detection, and lane assist.
Use this result with related RF tools
A microstrip calculation depends on the actual board stackup. Enter the intended dielectric properties and thickness, then confirm the manufactured dimensions and the complete RF return path before treating a result as final.
Get "10 RF Design Principles Every Engineer Should Know" Free
Learn practical principles for better RF circuits, PCB layouts, simulations, measurements, and troubleshooting.