Signal-to-noise ratio and time-modulated signal spectrum in four-dimensional antenna arrays

The signal-to-noise ratio (SNR) and the time-modulated signal spectrum in four-dimensional (4D) receiving antenna arrays are investigated. The expression of the SNR for the time-modulated signal is presented for the case where the bandwidth of the received signal is lower than the time modulation frequency and is demodulated in both cases of binary phase shift keying signal and Gaussian signal reception. It is shown that a narrowband signal can be received, time-modulated and then correctly demodulated by the 4D array, with an output SNR equivalent to that of a conventional phased array. Moreover, it is shown that 4D arrays can simultaneously receive multiple signals incoming from different directions at the same band by utilising multiple beams within the centre frequency band and low-order sidebands, with better output SNRs than that of a conventional array.