The Impedance Measurements Problem in Antennas for RFID Technique

Abstract

The authors paid particular attention to the problem of antenna impedance measurements in the RFID technique. These measurements have to be realized by using two ports of a vector network analyzer and dedicated passive differential probes. Since the measurement process and estimated parameters depend on the frequency band, operating conditions, type of the system component and antenna designs used, appropriate verification of the impedance parameters on the basis of properly conducted experiments is a crucial stage in the antenna synthesis of transponders and read/write devices. Accordingly, a systematized procedure of impedance measurements is proposed. It can be easily implemented by designers preparing antennas for different kinds of RFID applications. The essence of indirect measurements of the differential impedance parameters is discussed in details. The experimental verification has been made on the basis of a few representative examples.

Antenna Design for Semi-Passive UHF RFID Transponder with Energy Harvester

“…5).The impedance parameters of the chip and antenna are measured by using VNA Agilent PNA-X N5242A Vector Network Analyzer and PacketMicro TDP10210 differential probe. The probe is calibrated by using PacketMicro TCS50 RF Calibration Substrate [29]. The 3D calculated radiation pattern of the designed antenna is presented in Fig.…”

Compact RFID Enabled Moisture Sensor

“…After performing short-openload (SOL) calibration of the VNA, the differential probe is connected to the test cables at one end and to the antenna at the other. The S-parameters are obtained which are used to calculate the impedance of the antenna, as in [27].…”

A Method for Measuring the Radiation Pattern of UHF RFID Transponders

“…The complex impedance of RF front-end varies during the transponder chip working and its value is dependent on the electromagnetic field parameters (the electromagnetic field in RFID systems is influenced by environmental conditions around marked objects). It is the reason why the classical theory of antennas cannot be applied to solve the matching problem [18] and new measurement methods have to be developed in order to determine the parameters of RFID antennas.…”