| Dipole Antenna Calculator | |
|---|---|
| Magnetic Current (Im) | |
| Half antenna length (L) | |
| Wave Length (λ) | |
| Radius (r) | |
| Z-axis length (z) | |
| Coordinate Angle (θ) | |
| Dipole Current (I): | {{dipoleCurrentResult()}} |
| Electric Wave (Eθ): | {{electricWaveResult()}} |
| Magnetic Wave (HΦ): | {{magneticWaveResult()}} |
| Average radiated power density (Pd): | {{powerDensityResult()}} |
Formula:
Current (I) = I mSin(β(L - |z|) )
Electric Wave (Eθ) = ( 60 × Im / r ) × [ ( Cos (β L Cos&theta) - Cos(βL) ) / Sinθ ]
Magnetic Wave (HΦ) = ( Im / 2 πr ) ×[ ( Cos (βL Cos &theta) - Cos(βL) ) / Sin θ ]
Average radiated power density (Pd) = (15× Im2 / πr2 ) × [ ( Cos (βL Cos&theta) - Cos(βL) ) / Sinθ ] 2
Where,
β = 2π / λ
λ = Wave Length
Im = Magnetic Current
L = Half Antenna Length
r = radius
θ = Angle
Frequently Asked Questions
What is a dipole antenna and what are its advantages?
A dipole antenna is the simplest radiating element consisting of two conducting arms of length L/2 each, fed at the center. When oscillating current flows through it, it creates electromagnetic radiation. Dipoles are fundamental building blocks for antenna arrays, have omnidirectional patterns in one plane, and serve as reference antennas for comparing other designs. They’re easy to construct, analyze, and implement across all frequency ranges.
What is the relationship between antenna length and wavelength in dipole design?
The half-wavelength (λ/2) dipole is the most common design, with resonant length near λ/2 where input impedance is purely resistive (~73Ω). Longer antennas (like λ dipoles) show higher directivity and multiple lobes. Shorter antennas become capacitive (requiring matching), while longer antennas become inductive. The ratio L/λ determines the radiation pattern, gain, and impedance characteristics.
How do I optimize dipole antenna gain and directivity?
Dipole gain at resonance is approximately 2.15 dBi (omnidirectional). For increased directivity, use linear or planar arrays of dipoles (Yagi designs). Add reflectors and directors to create directional patterns. Operate at optimal frequency where physical length matches electrical resonance. Use proper feeding networks for impedance matching to maximize power transfer from transmitter.
When should I use a dipole versus other antenna types?
Dipoles excel as simple, broadband reference antennas from LF through microwave frequencies. Use them for omnidirectional coverage or as array elements. For focused beams, add reflectors (Yagi) or apertures (horns, dishes). Dipoles are preferred for initial design validation before implementing complex antennas, and as building blocks for arrays covering large areas.
What is the physical relationship between dipole antennas and antenna array patterns?
Dipole antennas are fundamental radiating elements used in arrays. Multiple dipoles with controlled phase relationships create constructive interference in desired directions and destructive interference elsewhere. Array factor patterns depend on element spacing, number of elements, and relative phase. Understanding single dipole properties is essential for predicting array performance.
Related Physics Calculators
- Friis Transmission Equation - Analyze signal transmission between dipole antennas
- Antenna Array Calculator - Design phased arrays of dipole elements
- Aperture Antenna Calculator - Compare with aperture antenna designs
- Antenna Gain Calculator - Calculate radiation intensity and gain
Physical Basis & References
This calculator applies Dipole Radiation Theory (Hertz dipole):
$$E_\theta = \frac{60 I_m}{r} \frac{\cos(\beta L \cos\theta) - \cos(\beta L)}{\sin\theta}$$
Key Physics Principles:
- Oscillating Dipole - Time-varying current creates radiation
- Far-Field Pattern - Radiation pattern depends on viewing angle θ
- Resonance - λ/2 dipole shows minimum reactance at resonance
- Reciprocity - Same pattern for transmission and reception
Key Assumptions:
- Thin wire dipole (radius « length)
- Far-field observation (r » L)
- Sinusoidal current distribution
- Free-space propagation
- Linear polarization
Typical Range of Values:
- Antenna length: 0.25λ to 2λ (quarter-wavelength to full wavelength)
- Frequency: 1 MHz to 300 GHz
- Gain: 1.5 to 8 dBi (depending on length)
- Input impedance: 5Ω to 1000Ω (depending on resonance)
Further Reading:
- Griffiths, D.J. (2013). Introduction to Electrodynamics, 4th Edition. Pearson.
- Balanis, C.A. (2016). Antenna Theory: Analysis and Design, 4th Edition. Wiley.
- Electromagnetic Radiation - MIT OpenCourseWare