Effects of hardware imperfection on six-port direct digital receivers calibrated with three and four signal standards

High-performance monolithically integrated 120° downconverter with relaxed hardware constraints

“…Under ideal hardware realization, i I and i Q can be obtained from the algebraic relation derived in Eq. (17). As it happened in the ideal 90° hybrid coherent receiver, common mode noise as RIN from LO and signal or ASE-signal beat noise will be once again cancelled under ideal performance.…”

“…(13) corresponds to three circles centered in q i (ideally 120° apart) with radius depending on the received symbol. As it was shown in [17], after the work in [18], three power readings are enough to establish a linear set of equations to uniquely obtain I-Q signal components under arbitrary hardware unbalances of phase diversity circuit. Consequently, note that the only two power measurements obtained from the standard 90° downconverter (see Fig.…”

“…where coefficients A Ii , A Qi , C I and C Q can be determined from a simple calibration procedure, solving the linear equation system obtained from Eq. (15) when transmitting four known symbols [17].…”

Signal Constellation Distortion and Ber Degradation Due to Hardware Impairments in Six-Port Receivers With Analog I/Q Generation

“…Six-port receivers are usually designed to work in homodyne operation, so that, the power detector outputs are directly obtained in baseband, and the I/Q signals can be recovered by analog or digital means. In the first six-port receiver proposals [1] the four power detectors outputs were digitized, which enabled the use of powerful calibration strategies to remove hardware imperfections [8]. However, more recently, analog I/Q generation has become the preferred alternative.…”