A 43.2 μW 2.4 GHz 64-QAM Pseudo-Backscatter Modulator Based on Integrated Directional Coupler

Multi-Tag Backscattering to MIMO Reader: Channel Estimation and Throughput Fairness

“…This full-duplex reader operation, involving efficient suppression of the unmodulated carrier leakage [16], provides array gains during DL carrier transmission and also enables spatial multiplexing of the backscattered signals in the UL. Also, in contrast to the full-duplex operation in conventional wireless systems [14] involving modulated information signals, the unmodulated carrier leakage can be efficiently suppressed [15] in monostatic full-duplex BSC systems. Exploiting this fact, several practical implementations [15], [16], [28]- [30] for fullduplex readers in monostatic BSC have been realized either using circulator or directional coupler.…”

“…Also, in contrast to the full-duplex operation in conventional wireless systems [14] involving modulated information signals, the unmodulated carrier leakage can be efficiently suppressed [15] in monostatic full-duplex BSC systems. Exploiting this fact, several practical implementations [15], [16], [28]- [30] for fullduplex readers in monostatic BSC have been realized either using circulator or directional coupler. So, for enabling fullduplex operation, reader includes a decoupler (or a circulator [28]) which comprises of automatic gain control circuits and conventional phase locked loops [29] to effectively suppress out the transmit carrier from the backscattered one at the receiver unit [15].…”

“…Exploiting this fact, several practical implementations [15], [16], [28]- [30] for fullduplex readers in monostatic BSC have been realized either using circulator or directional coupler. So, for enabling fullduplex operation, reader includes a decoupler (or a circulator [28]) which comprises of automatic gain control circuits and conventional phase locked loops [29] to effectively suppress out the transmit carrier from the backscattered one at the receiver unit [15]. Here, exploiting the fact that the reader performs an unmodulated transmission, this decoupler can easily suppress the self-jamming carrier, while isolating the transmitter and receiver units' paths, to eventually implement the full-duplex architecture for monostatic BSC settings [30], [31].…”

“…where X k 0 N ×(k−1)N I N 0 N ×(M−k)N , ∀ k ∈ M, is an N × N M matrix and S A (A ⊗ S) ∈ C N M×N M . Further, we can write (15) in a more elegant form given below.…”

“…Set γ k = γz k , ∀ k ∈ M. 5: Solve the convex problem OS using CVX in Matlab and set its global-optimal solution to F op ⊲ SDR OS : maximize . 15: if (ch = 1) then ⊲ Output for low SNR case 16: Set fL = fn op ,mop and obtain GL by substituting fL in (24). 17: else if (ch = 2) then ⊲ Output for high SNR case 18: Set fH = fn op ,mop and obtain GH by substituting fH in (24).…”