Polarization Reconfigurable Dipole Antenna for FM Band Radio Spectrum Monitoring System
Abstract
This paper presents the design and implementation of a polarization reconfigurable dipole antenna operating in the FM radio frequency band (88–108 MHz) for low-cost radio spectrum monitoring applications. The proposed antenna consists of two orthogonal radiating arms integrated with an electronically controlled switching network that enables selection between two linear polarization states. Simulated results show that the antenna achieves |S₁₁| below −10 dB across the entire FM band, with stable omnidirectional radiation patterns and realized gains of approximately 1.7 dBi and 1.8 dBi for the two polarization modes. A prototype was fabricated and measured to validate the design. Measured results confirm acceptable impedance matching over the frequency range of 93–102 MHz, covering the core FM broadcast channels, while maintaining omnidirectional radiation characteristics and effective polarization switching. The minor frequency shift observed in measurements is attributed to fabrication tolerances and environmental effects. Owing to its simple structure, low fabrication cost, and reliable performance, the proposed antenna is well-suited for large-scale deployment in automated FM-band radio spectrum monitoring systems.