This paper presents a high rejection and compact ultra-wideband (UWB) highpass filter using suspended stripline technology based on Generalized Chebyshev polynomial that operates between 3 GHz to 12 GHz for wideband application. Based on the Generalized Chebyshev polynomial, a 13th order lowpass filter with 5 pairs of finite transmission zeros (TZ) is synthesized. Under frequency transmission, the highpass filter network can be realized. Suspended stripline is used to realize the proposed highpass filter by introducing parallel coupled line placed between the ultra-Thin Roger Duriod RO3003 substrate and the resonators to obtain higher coupling and achieve very wideband. With the unique passband, stopband elements and excellent reliability in rough working condition, the application of the filter ranging from military and aerospace to commercial communication system such as ultra-broadband receiver, 5G and others. The proposed filter is simulated, fabricated, and tested to verify the proposed design concept. The measured and simulated results are in agreement to each other. Therefore, the highpass filter in this paper could serve as a reference for high rejection and ultra-wideband application. © 2022 IEEE.