Abstract
Coaxial aircells are designed and fabricated to measure the electromagnetic properties of ferrite materials in the frequency range from 1 MHz to 3.6 GHz. These S-parameters are actually measured connecting the aircell to a vector network analyzer (VNA). The electromagnetic properties such as complex permittivity and complex permeability are extracted using Nicolson-Ross-Weir (NRW) method and also suitable air-gap corrections are made. To optimize the measured result and to estimate the error, the aircells are characterized in terms of their phase constant and resistivity of the aircell conductor. The measurements clearly showed that the electrical length is longer than the mechanical length of the aircell at all frequencies. The arithmetic mean of the resistivity of aircell which is of 7mm line size and 60mm length is about 66 nΩm. This paper presents a simple method by which the phase constant and resistivity of the aircell can be determined accurately. This is done with the transmission measurements made using a VNA.
Highlights
INTRODUCTIONCoaxial air dielectric transmission lines can be very useful as references, or standards, for high-precision impedance measurement at RF and microwave frequencies [13,14,15]
The measurement of complex permeability (μ∗ = μ′ − iμ′′) and complex permittivity (ε∗ = ε′ − iε′′) of materials at high-frequency is used in microwave communication devices, electromagnetic interference (EMI) shielding, electromagnetic compatibility (EMC), field sensors, microwave heating and magnetic recording etc
Before we proceed for the measurement of the ferrite samples, the fabricated coaxial aircells without samples are characterized for phase constant and resistivity
Summary
Coaxial air dielectric transmission lines can be very useful as references, or standards, for high-precision impedance measurement at RF and microwave frequencies [13,14,15]. These aircells do not contain dielectric support that are usually used to hold the center conductor of the aircell coaxially. The scattering equations relate the measured scattering parameters to the permittivity and permeability of the material For these aircells to be used for such applications, they must be characterized accurately in terms of their propagation characteristics and impedance. A simple to-execute test technique has been exhibited in this paper for the determination of the resistivity of the aircells conductor including VNA estimations of the S-parameters of the aircell
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