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Improved Asymptotic Friis Formula with Higher-Order Terms: Calculating Antenna Coupling in Close Proximity
1Department of Electrical and Electronics Engineering, Sejong Cyber University, Seoul 05000, Republic of Korea.
Sensors (Basel, Switzerland)
|August 13, 2026
Summary
Accurate near-field communication link budget estimation is crucial for 6G. This study introduces an improved asymptotic formula for antenna coupling, reducing the minimum prediction distance by 22-25% for enhanced accuracy.
Area of Science:
- Electromagnetics and Applied Electrophysics
- Wireless Communication Systems
- Antenna Theory and Design
Background:
- Sixth-generation (6G) communication systems increasingly utilize near-field communication (NFC).
- Accurate link budget estimation is essential for NFC performance in the near-field region.
- Existing methods for predicting antenna coupling at short distances require refinement.
Purpose of the Study:
- To develop an accurate asymptotic expression for the gain reduction factor in near-field antenna coupling.
- To enhance the prediction accuracy of antenna coupling at short distances.
- To investigate the impact of higher-order terms on the minimum prediction distance.
Main Methods:
- Derivation of an asymptotic expression for the gain reduction factor, incorporating higher-order terms.
- Examination of asymptotic Friis formulas with gain reduction factors for circular and rectangular apertures.
- Validation of the derived formula through full-wave electromagnetic simulations and experimental measurements.
Main Results:
- The proposed asymptotic formula with higher-order terms provides improved accuracy for near-field antenna coupling.
- Asymptotic formulas incorporating higher-order terms reduce the minimum prediction distance by 22-25% compared to lower-order terms.
- The derived formula demonstrates validity when compared against full-wave simulations and measurements.
Conclusions:
- The enhanced asymptotic expression is effective for accurate near-field communication link budget estimation in 6G systems.
- Incorporating higher-order terms significantly improves the prediction of antenna coupling at short ranges.
- This work provides a more precise tool for designing and analyzing near-field communication systems.
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