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Determination of Far-Field Antenna Patterns from Near-Field Measurements

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Richard C. Johnson, H. Allen Ecker, J. Searcy Hollis · 1973

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This foundational 1973 antenna measurement research established techniques still used today to characterize EMF emissions from wireless devices.

Plain English Summary

Summary written for general audiences

This 1973 technical study examined three methods for measuring antenna radiation patterns in near-field conditions rather than requiring impractical far-field distances. The research focused on engineering solutions for antenna testing when conventional long-distance measurements aren't feasible.

Why This Matters

While this appears to be a purely technical engineering study from 1973, it represents the foundation of how we measure and understand antenna radiation patterns today. The techniques described here are still used to characterize how cell towers, WiFi routers, and other wireless devices emit electromagnetic fields into our environment. Understanding antenna patterns is crucial for EMF exposure assessment because it determines how radiation spreads from sources we encounter daily. The reality is that proper antenna characterization helps engineers design systems and helps researchers accurately model human exposure levels from wireless infrastructure.

Exposure Information

Specific exposure levels were not quantified in this study.

Cite This Study
Richard C. Johnson, H. Allen Ecker, J. Searcy Hollis (1973). Determination of Far-Field Antenna Patterns from Near-Field Measurements.
Show BibTeX
@article{determination_of_far_field_antenna_patterns_from_near_field_measurements_g5531,
  author = {Richard C. Johnson and H. Allen Ecker and J. Searcy Hollis},
  title = {Determination of Far-Field Antenna Patterns from Near-Field Measurements},
  year = {1973},
  
  
}

Quick Questions About This Study

The study identified aperture scanning with field probes, creating uniform plane waves with reflectors, and near-field focusing with pattern measurement at reduced ranges as the three successful techniques for determining far-field patterns.
Conventional far-field measurements often require impractically long distances, antennas may be impossible to move from their operating environment, or the extensive pattern data collection takes too much time on ranges.
A scanning field probe samples the amplitude and phase distributions across the antenna aperture in the near-field region, then mathematical transforms convert these measurements into far-field radiation patterns.
This method uses a feed and large reflector to create an approximately uniform plane wave near the test antenna, simulating far-field conditions without requiring the actual distance to the radiating far-field.
The test antenna is focused within the near-field region where patterns are measured at reduced range, then the antenna is mathematically refocused to infinity to determine the actual far-field performance.