Passive High Power RF Comb Filters Using Epitaxial GaN/NbN/SiC HBARs

Area of Science:

• Materials Science
• Electrical Engineering
• Acoustics

Background:

• Traditional RF comb filters can be bulky and limited in power handling.
• Gallium Nitride (GaN) and Niobium Nitride (NbN) are promising materials for high-frequency electronics.
• Silicon Carbide (SiC) substrates offer excellent thermal and mechanical properties.

Purpose of the Study:

• To demonstrate the first passive RF comb filters utilizing GaN/NbN/SiC epi-HBARs.
• To characterize the performance of these novel comb filters in terms of passband distribution, bandwidth, and figure of merit.
• To assess the high-power handling capabilities and potential applications of the developed filters.

Main Methods:

• Fabrication of two-port devices using epitaxial GaN/NbN/SiC layers.
• Electrical transduction and acoustic coupling for device operation.
• Characterization of filter response, including passband count, free spectral range (FSR), bandwidth (BW), and f x Q values.

Main Results:

• Demonstrated a multi-mode epi-HBAR comb filter with 158 passbands from 1 to 4 GHz.
• Achieved individual passbands with BWs up to 800 kHz and f x Q values up to 7x10^14 Hz.
• Observed linear, distortion-free performance up to 1 W CW and 10 W pulsed RF power.

Conclusions:

• Epi-HBARs offer a compact and high-performance solution for RF comb filters.
• These filters exhibit excellent high-power handling, suitable for demanding RF applications.
• Potential for co-fabrication with GaN electronics, enabling integrated RF systems for spectrum sensing and radar.