Future spectrum sharing between high-power radars and Citizens Broadband Radio Service Device CBSD in the 3550–3650 MHz (3.5 GHz) band could expose radio frequency (RF) receiver front-end low noise amplifiers (LNAs) to high peak power radar pulse signals in the band under certain situations. In this band, radar effective isotropic radiated power (EIRP) peak levels can exceed 1 gigawatt. Previous experience with LNAs exposed to high-power radar pulses in spectrum near 3.7 GHz has shown that non-linear effects can be induced in the LNAs, leading to service interruptions. To assess the level of risk for similar LNA overload at 3.5 GHz, NTIA performed gain overload (e.g., compression) tests on two representative 3.5 GHz LNAs and a small-cell base station receiver. The tests determined the pulsed radar signal power levels that caused overload (1 dB gain compression) for these devices. Approximate distance separations that would be necessary to preclude potential overload interference effects are presented, based on the measurement results and propagation modeling.
Keywords: radar; spectrum sharing; low noise amplifier (LNA); effective isotropic radiated power (EIRP); Long Term Evolution (LTE); 3.5 GHz band; Citizens Broadband Radio Service Devices (CBSD); non-linear effects; LNA overload; 47 C.F.R. Part 96; General Authorized Access (GAA); Priority Access Licensed (PAL)