Non-intrusive characterization of 60GHz antenna array, using packet measurements

Standardization bodies such as the 3rd Generation Partnership Project (3GPP), as well as industry and academia are investigating new and novel ways to evaluate the performance of Fifth Generation (5G) devices. The evaluation of current (sub 6GHz) wireless user equipment (UE) is carried out using cabled connections to temporary antenna connectors which disconnect the antenna. More recently, SISO over the air (OTA) test methods have been developed to measure antenna efficiency. The most recent evolution is the addition of MIMO OTA tests which measure the impact of the antenna on MIMO transmissions. The 5G standard will utilise the large available bandwidth at centimetre and millimetre wave frequencies of up to 100GHz to provide gigabit data rates. At such high frequencies, 5G devices will require phased antenna arrays to compensate for the high losses with the use of beamforming techniques. These integrated arrays are unlikely to have temporary antenna connectors due to their small form-factors, and this represents a big challenge for non-intrusive testing of their performance. The consequence is that all testing at mmWave will need to be carried out OTA. This paper outlines a method to determine the 3D antenna array pattern of the 60 GHz antenna array integrated within an 802.11ad modem (Lightning-J manufactured by Blu Wireless Technology) with the use of packet measurements, without disassembling the device or bypassing the antenna. Co and cross polar relative array gain patterns were measured for a range of array scan angles, and show good agreement with the modem behaviour (15.7dBi maximum boresight directivity) including the cross-polarisation levels observed in outdoor testing using this modem (up to −10dB co/cross polar ratio).