ABSTRACT This paper presents a novel, extremely low‐profile, miniaturized monopole antenna for spectrum monitoring applications. The antenna achieves an unprecedented 100:1 impedance bandwidth (30–3000 MHz), corresponding to a fractional bandwidth of 196%, with a compact size of , where is the wavelength at the lowest operating frequency. To address size, weight, and power (SWaP) constraints while extending operation into the challenging 30–300 MHz band, a multi‐stage lumped‐element matching network is integrated on the antenna's back side. This dual‐path matching network enables Ant. 5 () to match the low‐frequency performance of a much larger antenna (Ant. 4, ), effectively overcoming the size‐bandwidth limitation. The antenna achieves a peak gain of 3.6 dBi at 800 MHz and maintains gain above 0 dBi from 360 to 3000 MHz. Measured VSWR remains below 3 from 30 to 38 MHz and below 2 across the remaining of the operational band. Simulated and measured results show excellent agreement, validating the design's suitability for SWaP‐constrained platforms such as mobile, airborne, and densely deployed systems. This study offers a transformative solution for broadband spectrum monitoring and direction‐finding arrays.
Khan et al. (2025) studied this question.