Antenna Fundamentals and Integration Practical Antenna Questions Informational

How do I design a collinear antenna array for omnidirectional coverage with gain?

Designing a collinear antenna array for omnidirectional coverage with gain stacks multiple half-wave dipole or sleeve antenna elements vertically, phased to produce in-phase radiation in the broadside direction. The collinear array concentrates the radiation in the azimuth plane (horizontal) while maintaining omnidirectional coverage (360 degrees in azimuth), increasing the gain over a single element. The design parameters are: number of elements N (more elements = higher gain but narrower elevation beamwidth and taller antenna; gain approximately 10log10(N) + 2 dBi over a single dipole; for N=2: gain approximately 5.2 dBi; for N=4: gain approximately 8.2 dBi; for N=8: gain approximately 11.2 dBi), element spacing (typically lambda/2 to lambda between element centers; lambda/2 spacing: compact, moderate sidelobe level; lambda spacing: higher gain per element but higher sidelobes), phasing method (each element must be fed in-phase for maximum broadside radiation; for a collinear dipole array: the phasing is achieved by alternating the feed polarity of adjacent elements with half-wave interconnecting transmission lines; for a Franklin array: each element is fed through a collinear phasing stub that provides the 180-degree phase reversal; for a commercial collinear: the phasing is built into the feed network inside the radome), and feed network (a corporate feed or series feed distributes power equally to all elements; the feed network must maintain equal amplitude and phase at each element across the operating bandwidth).

Category: Antenna Fundamentals and Integration

Updated: April 2026

Product Tie-In: Antennas, Measurement Equipment

Collinear Antenna Array Design

Collinear antenna arrays are the standard choice for base station and repeater antennas where omnidirectional coverage with gain is needed. They are used in: VHF/UHF land mobile radio, cellular base stations (omni-cell configurations), marine VHF, and aviation COM/NAV.

Parameter	Low Gain	Medium Gain	High Gain
Gain Range	2-6 dBi	6-15 dBi	15-45 dBi
Beamwidth	60-360°	15-60°	1-15°
Typical Types	Dipole, monopole, patch	Yagi, helical, horn	Parabolic, array, Cassegrain
Bandwidth	Narrow to wide	Moderate	Narrow to moderate
Complexity	Low	Medium	High

Design Considerations

When evaluating design a collinear antenna array for omnidirectional coverage with gain?, engineers must account for the specific requirements of their target application. The optimal choice depends on the frequency range, power level, environmental conditions, and cost constraints of the overall system design.

Performance verification: confirm specifications against the application requirements before finalizing the design
Environmental factors: temperature range, humidity, and vibration affect long-term reliability and parameter drift
Cost vs. performance: evaluate whether the application demands premium components or standard commercial grades

Performance Trade-offs

When evaluating design a collinear antenna array for omnidirectional coverage with gain?, engineers must account for the specific requirements of their target application. The optimal choice depends on the frequency range, power level, environmental conditions, and cost constraints of the overall system design.

Common Questions

Frequently Asked Questions

How many elements do I need?

Depends on the required gain and the acceptable antenna height: for 6 dBi gain: 2-3 elements (approximately 0.5-1 m tall at UHF). For 9 dBi gain: 4-6 elements (approximately 1-2 m). For 12 dBi gain: 8-10 elements (approximately 3-4 m). For 15 dBi gain: 16+ elements (approximately 6+ m). Higher gain = taller antenna = narrower elevation beamwidth. Ensure the elevation beamwidth covers the intended service area (a very narrow beam may miss nearby users who are at high elevation angles relative to the antenna).

What is the bandwidth of a collinear array?

The bandwidth is limited by: the element bandwidth (each element must remain resonant and well-matched), and the phasing network (the phase between elements must remain correct). Typical bandwidth: 5-10% for a simple collinear (adequate for a single VHF or UHF channel). Wider bandwidth (10-30%): use wideband elements (e.g., fat dipoles, sleeve dipoles) and a broadband feed network. For broadband coverage (e.g., entire VHF 136-174 MHz band = 24%): use a wideband collinear design with empirical optimization.

Can I tilt the beam?

Electrical downtilt: by introducing a progressive phase shift between elements (instead of all in-phase), the main beam tilts downward. Downtilt = arcsin(phase_gradient × lambda / (2pi × d)). For 1 degree downtilt at d=lambda/2: need approximately 3.1 degrees of progressive phase per element. Downtilt is used in cellular base station antennas to reduce interference to distant cells and improve coverage of the near-in area. Most commercial base station collinear antennas include adjustable electrical downtilt (0-10 degrees).

Keep Reading