Design, fabricate, and characterize multiple antenna types (dipole, Yagi, patch, helical) using NanoVNA measurement and HFSS simulation.
Design, fabricate, and characterize multiple antenna types (dipole, Yagi, patch, helical) using NanoVNA measurement and HFSS simulation. This comprehensive guide covers everything from design through implementation, testing, and deployment.
Antenna converts electrical energy to electromagnetic waves and vice versa. Key parameters: Gain (dBi, ratio to isotropic antenna), Directivity (how concentrated the radiation pattern), Bandwidth (frequency range where VSWR < 2), Impedance (complex input impedance at feed point, target: 50Ω for match to coax), Polarization (linear: vertical/horizontal, circular: L/R). Half-wave dipole: most fundamental antenna. Length = λ/2 = c/(2f). Impedance ≈ 73Ω at resonance. Pattern: donut shape, null along axis, maximum broadside.
10 components required for this project.
| # | Component | Purpose | Qty |
|---|---|---|---|
| 1 | NanoVNA V2 (vector network analyzer, 3GHz) | Antenna measurement (S11, VSWR, impedance) | x1 |
| 2 | Copper tube (8mm OD) for dipole elements | Yagi antenna elements | x1 |
| 3 | FR4 PCB substrate (1.6mm, εr=4.4) | Microstrip patch antenna substrate | x1 |
| 4 | SMA connectors + RG316 coax cable | RF connectivity | x1 |
| 5 | Balun core (Fair-Rite 2861010002) | Dipole balun (balanced-to-unbalanced) | x1 |
| 6 | HFSS or CST Studio Student (simulation) | Electromagnetic simulation | x1 |
| 7 | Antenna test range (open field 10m) | Radiation pattern measurement | x1 |
| 8 | RTL-SDR (for pattern measurement) | Receive signal strength measurement | x1 |
| 9 | Signal generator (for pattern measurement) | Reference transmit signal | x1 |
| 10 | 3D printed antenna mast and bracket | Measurement fixture | x1 |
Follow these 4 steps carefully.
Antenna converts electrical energy to electromagnetic waves and vice versa. Key parameters: Gain (dBi, ratio to isotropic antenna), Directivity (how concentrated the radiation pattern), Bandwidth (frequency range where VSWR < 2), Impedance (complex input impedance at feed point, target: 50Ω for match to coax), Polarization (linear: vertical/horizontal, circular: L/R). Half-wave dipole: most fundamental antenna. Length = λ/2 = c/(2f). Impedance ≈ 73Ω at resonance. Pattern: donut shape, null along axis, maximum broadside.
Yagi: driven element + reflector + directors. Reflector: 5% longer than dipole, positioned λ/4 behind — reflects forward-going wave backward. Directors: 5% shorter, spaced λ/4 to λ/2 ahead — concentrate wave forward. Gain: 3-element Yagi ≈ 7 dBd (vs dipole). Each director adds ~1dB up to diminishing returns at 15+ elements. 433 MHz 5-element Yagi: driven = 340mm, reflector = 356mm, director 1 = 324mm, director 2 = 318mm, boom length ≈ 600mm. Design using YagiCalc software or MMANA-GAL (free NEC-based antenna simulator).
Patch antenna: rectangular copper patch on dielectric substrate above ground plane. Resonant at frequency where patch length ≈ λ/2 (in dielectric medium). Length: L = λ/(2×√εr_eff). Width: W = c/(2f) × √(2/(εr+1)). Feed: 50Ω coax at inset feed position. Used in: GPS, WiFi (2.4GHz patch arrays), mobile phones (LTE patch). Advantages: low profile, easily integrated on PCB, can be made circularly polarized (square patch, two feed points 90° apart). Bandwidth: typically 2–5% (narrow compared to wire antennas).
Calibration: connect OPEN, SHORT, LOAD (50Ω) standards to NanoVNA port, perform SOLT calibration — this removes cable and connector effects. Connect antenna via reference cable. Measure S11: magnitude and phase of reflection coefficient. Calculate VSWR = (1 + |S11|) / (1 - |S11|). Resonant frequency: where S11 is minimum (most power delivered to antenna). Target: |S11| < -10 dB (VSWR < 2) across desired bandwidth. Smith chart: shows complex impedance — ideal: center of Smith chart (50Ω, 0Ω reactance). Tune: adjust element length or feed point until resonant at target frequency.
Core code for antenna_calculator.py:
import math def dipole_design(freq_MHz): """Design a half-wave dipole antenna.""" c = 299792458 # Speed of light m/s freq = freq_MHz * 1e6 wavelength = c / freq # Half-wave dipole: actual length slightly less than λ/2 due to end effects velocity_factor = 0.95 # Wire dipole (~95% velocity factor) length_total = (wavelength / 2) * velocity_factor length_each_arm = length_total / 2 print(f"=== Half-Wave Dipole @ {freq_MHz} MHz ===") print(f"Wavelength: {wavelength*100:.1f} cm") print(f"Total length: {length_total*100:.1f} cm") print(f"Each arm length: {length_each_arm*100:.1f} cm") print(f"Feed impedance: ~73 Ω (real), ~43 Ω reactance at resonance") print(f"VSWR to 50Ω: ~1.5 without balun/matching") print(f"Gain: ~2.15 dBi (2.16 dBi theoretical)") return length_each_arm def yagi_design(freq_MHz, num_directors=3): """Simple Yagi-Uda design.""" c = 299792458 lam = c / (freq_MHz * 1e6) driven = lam * 0.4736 # Driven element refl = lam * 0.4822 # Reflector (5% longer) dirs = [lam * (0.4427 - i*0.002) for i in range(num_directors)] print(f"\\n=== {num_directors+2}-element Yagi @ {freq_MHz} MHz ===") print(f"Reflector: {refl*100:.1f} cm (at -λ/4 = {lam/4*100:.1f} cm)") print(f"Driven element: {driven*100:.1f} cm (feed here)") for i, d in enumerate(dirs): print(f"Director {i+1}: {d*100:.1f} cm (at +{(i+1)*lam/4*100:.1f} cm)") gain_dBd = 3.7 + 2.4 * math.log10(num_directors) print(f"Estimated gain: {gain_dBd:.1f} dBd = {gain_dBd+2.15:.1f} dBi") dipole_design(433) yagi_design(433, num_directors=3)Test Antenna Design and RF Propagation by verifying each subsystem individually before full integration.
Verify power voltages, check ground connections, use serial monitor for debug.
An interactive simulator will be available here — simulate circuits and run code in-browser without hardware.