Wideband MIMO Channel Sounding Setup for 2.4 GHz ISM Band

This paper describes a wideband multi-antenna channel sounding system designed to capture 4x4 space-polarization MIMO channel impulse responses using an 80 MHz-wide signal in the 2.4 GHz ISM band (2402-2483 MHz). Frequency multiplexing of the sounding waveforms across the transmit antenna ports enables simultaneous capture of the full 4x4 MIMO channel response within a short snapshot time (less then 100 microseconds). Therefore, channel sounding repetition rates up to 10 kHZ are achievable. The sounding waveforms are optimized for low crest factor (0.4 dB) in order to make best use of the power amplifiers output range and are designed to have minimal spurious power in an adjacent restricted-band-of-operation described by FCC regulations (part 15.205). The receiver employs direct digital RF reception and digital linear phase down-conversion to help minimize distortion of the captured time-domain channel impulse responses.