In this paper, we propose a new phased array calibration method that measures all antenna element excitations simultaneously. The method has the minimum number of measurements among the known similar methods. The auxiliary antenna used for measurement is placed in either near-field or far-field region to receive the complex array signals during the change of the antenna element phase settings. According to the superposition principle of electromagnetic field, a set of linear equations concerning the element signals are created with the measured array signals. With the scattering parameters between the measurement probe antenna and the element antennas pre-stored or simplified, we calculate the excitations of the antenna elements by solving the linear equations. The coefficient matrix of the linear equations determines the antenna element phase settings for the array signal measurements. The principles for the selection of the coefficient matrix concerning accuracy, complexity and hardware requirements are presented. A recursive matrix-forming method is presented for the matrix selection in this paper. Numerical simulations and experiment results validated the effectiveness of the proposed method.

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In this letter, a single-fed low-profile high-gain circularly polarized slotted cavity antenna using a high-order cavity mode, i.e. TE 440 mode, is proposed. The proposed antenna has a simple structure which consists of a radiating linearly polarized slotted cavity antenna and a linear-to-circular polarization converter. An antenna prototype operating at WLAN 5.8 GHz band fabricated with low-cost standard printed circuit board (PCB) process is exemplified to validate the proposed concept. Measured results compared to their simulated counterparts are presented, and a good agreement between simulation and measurement is obtained.

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Radio frequency identification (RFID) is a key technology to realize IoT (Internet of Things) dreams. RFID technology has been emerging in sensing, identification, tracking, and localization of goods. In order to tag a huge number of things, it is cost-effective to use one RFID antenna for tagging different things. Therefore, in this paper a platform tolerant RFID tag antenna with tunable capability is proposed. The proposed tag antenna is designed and optimized using characteristic mode analysis (CMA). Moreover, this tag antenna consists of a folded patch wrapped around FR 4 substrate and a feeding loop element printed on a paper substrate. The inductive feeding loop is stacked over folded patch and it provides impedance match with RFID chip. Because of separate radiating and feeding element, this tag antenna has a versatility of impedance matching with any RFID chip. Furthermore, this tag is able to cover American RFID band (902–928 MHz) and can be tuned to European RFID band (865–868 MHz) by adding tunable strips. In order to demonstrate platform tolerant operation, the read range of RFID tag is measured by mounting it on different materials. The maximum read range of RFID tag is 4.5 m in free space or on dielectrics and 6.5 m above 200 × 200 mm2 metal plate, respectively.

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