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In the modern LTE systems the Zadoff-Chu sequences are being used to transmit the synchronization signal. The complex sequence is transmitted both in the in-phase (I) and quadrature (Q) channels, the precision of which depends on the technological mismatch of the devices' parameters. The used sequences set a series of limitations on the existed communication systems. The development of new and prospective communication systems, including 5G, sets a mission for designers of the hardware components to achieve the performance limits for signal processing while employing current manufacturing technologies. There are various issues connected with technological scaling, such as using new materials and optimization of power consumption. But the issue of match precision of same type of elements, both passive and active, within same technological process can't be solved with the current technological basis and equipment. Thus, the restrictions induced by the mismatch are laid upon all devices in the communications system. This article focuses on the analysis of behavior of a synchronization system with Zadoff-Chu sequences in the presence of technological imbalance of all elements and devices inside the communication system, namely, I- and Q-channels. Synchronization system analysis includes evaluation for linear and non-linear effects occurring during the signal conversion and processing. The phase and amplitude mismatch of integrated circuit elements in the I- and Q-channels was analyzed. Based on that analysis we obtained the influence of mismatch on settling and hold-up times, and on the false-alarm probability and the synchro-signal undetection probability. The limits of local homeomorphic mapping for technological imbalance of synchronization system parameters are defined. Based on the obtained results, we suggest several measures for circuit and layout implementation of devices in the I- and Q-channels. Additionally, an evaluation of the possibility of restoring synchronization with limited resources of analog-to-digital conversion is made, where the restoring accuracy of each sequence element is constrained by the effective resolution of ADC. |
