Primary metrics for simulate antenna performance.

Antenna Designer & Guide (Full Suite)

1. Resonant Length Calculator

Calculate wire lengths based on frequency.

Target Frequency (MHz)

Velocity Factor

0.90 (Thick Wire) 0.95 (Standard) 1.00 (Free Space)

Quarter Wave (Monopole)

— mm

Ideal designs for ground plane

Half Wave (Dipole)

— mm

Total length (end to end)

Formula: L = (c / f) * VF * (1/4 or 1/2)

2. PCB Microstrip Calculator

Find the trace width for 50Ω Impedance on FR4.

PCB Height (mm)

Standard FR4 is 1.6mm

Dielectric Constant (Er)

FR4 is ~4.4

Trace Width (mm): 3.00

Calculated Impedance

— Ω

Adjust Width

FR4 Substrate

Dipole

Balanced, Omnidirectional.

Monopole

Needs Ground Plane.

Yagi-Uda

High Gain, Directional.

Patch

PCB Based, Directional (Up).

3. PCB Layout Rules

How to place a chip or trace antenna on a PCB circuit board.

KEEP OUT No Copper
No GND

MCU

The Keep-Out Zone

Ensure adequate space for the antenna element, avoiding components on or immediately below the ground plane. This requires suitable space.

Edge Placement

Always place the antenna on a corner or edge of the PCB. Don’t press it into the middle.

Short Feedline

Keep the trace connecting the radio chip to the antenna as short and straight as possible in Best practises .

4. Theoretical Range Estimator (Friis)

How far will my signal go? (Line of Sight)

Tx Power (dBm)

Receiver Sensitivity

Tx Antenna Gain (dBi)

Rx Antenna Gain (dBi)

Frequency (Used from Section 1)

2400 MHz

Estimated Line-of-Sight Range

— km

Theoretical Max. Real world is usually 21-55% of this due to obstacles, humidity, and ground reflection.

5. Testing Metrics & Validation

Convert VNA readings, analyze impedance, and estimate cable losses.

5.1 VNA Converter & Impedance Mismatch

Characteristic Impedance (Z₀, Ohms)

Input VSWR (e.g., 1.5)

– OR –

Input Return Loss S11 (dB) (e.g., -14)

Max Impedance (Zmax)

— Ω

Min Impedance (Zmin)

— Ω

Power Mismatch

Power Transmitted: 96.0%

Power Reflected (Wasted): 4.0%

5.2 Quality Factor (Q) & Bandwidth

Assumed Q-Factor:

—

Fractional Bandwidth:

–%

Q is the ratio of stored energy to energy lost. Low Q antennas (e.g., Dipoles, Log Periodic) have wide bandwidth. High Q antennas (e.g., Patches, Resonant Structures) have narrow bandwidth.

5.3 Coax Cable Loss Estimator @ 2.4GHz

Cable Type

Length (Meters)

Signal Loss:

-3.0 dB

50% Power Lost

5.4 Performance Benchmarks

VSWR

Return Loss (S11)

Power Reflected

Status

1.0 – 1.5

< -14dB

< 4%

Excellent

1.5 – 2.0

-14 to -10dB

4% to 11%

Acceptable

> 2.0

> -10dB

> 11%

Poor/Bad

6. Glossary & Terms

Visualizing Impedance: The Smith Chart

Center = Perfect Match (50 Ω). Top = Inductive. Bottom = Capacitive.

Gain (dBi)

Antennas don’t create power, they focus it. dBi measures how much it focuses signal compared to a ball (Isotropic) radiating equally everywhere.

Omni (0dBi) vs Directional (6dBi)

Fresnel Zone

Visual Line of Sight (LOS) isn’t enough. Radio waves occupy a parabolic-shaped volume. If the ground cuts into this, you lose range

dBm vs mW

Power scale is logarithmic. Every +3dB doubles the power.

0 dBm = 1 mW
10 dBm = 10 mW
20 dBm = 100 mW
30 dBm = 1000 mW (1W)