A real-time directional sensing system is proposed
for 2:4 GHz ISM band by exploiting the concept of spatiotemporal
spectral white spaces. The proposed system consists
of a 16-element patch antenna array, an FFT-based multi-beam
beamformer and an energy detector. Our system operates at
the baseband with quadrature sampling. Furthermore, digital
architectures for two energy detectors that employ integrate-anddump
circuits are presented. With the multi-beam beamformer,
the first energy detector can be employed to directional sensing
and the second can be employed for both directional and spectral
sensing of radio frequency sources. The multi-beam beamformer
having 16 beams and the energy detectors are implemented
on a ROACH-2 based FPGA system with a 160 MHz clock.
With an 8-point temporal FFT, the second energy detector
provides approximately 20 MHz bandwidth per temporal FFTbin.
Preliminary experimental measurements obtained with Wi-
Fi devices and the first energy detector verify the proof-of-concept
directional sensing of the proposed system
