Millimeter-wave frequencies and beamforming techniques are two crucial pillars for realizing high data rate communication systems in 5G (learn more). By using beamforming techniques, huge transmission loss of mm-wave can be compensated and SNR performance of the communication system can be improved significantly. Improved SNR performance will in turn improve the achievable data-rate of the communcation system.

Beamforming is usually realized using phased array systems, where it is possible to control the direction of the output beam by simply adjusting the phase of output signals from multiple transceiver elements as shown in Fig.1 above. This method is preferred because the beam direction can controlled electronically, hence no moving parts are needed to control the beam direction.

Unfortunately, on-chip implementation of such system is sensitive to the mismatch between elements,which will heavily degrade the beam directivity and beam steering accuracy of the phased array system. This mismatch exists due to several factors such as unbalanced layout design and unavoidable variation during chip fabricattion process.To account for this problem, calibration of the phased array system is needed in order to restore the performance of the system, as shown in Fig.2 below.

In real world applications, state-of-the-art phased array systems ( [1] [2] ) are often equipped with phase and amplitude detection circuits to realize calibration process. The role of these circuits are to inspect the signal states at each element output and detect any mismatches between the elements. Then, Based on the obtained information, calibration can be performed to ensure optimal operation of the phased array system.

To summarize, high data rate communications in 5G are mainly implemented using millimeter-wave phased array systems. However, on-chip implementations of such system are weak to mismatches which heavily degrade their performance. To account for this problem, real world application of phased array systems require calibration to be performed in order to restore and optimize their performance.