Vikass Monebhurrun

Predicting the starting distance of the far field

The far field of an antenna is generally considered to be the region where the outgoing wavefront is planar and the antenna radiation pattern has a polar variation and is independent of the distance from the antenna. Hence, to generate a locally plane wave in the far field the radial component of the electric field must be negligible compared to the transverse component. Also, the ratio of the electric and the magnetic far fields should equal the intrinsic impedance of the medium. These two requirements must hold in all angular directions from the antenna. The radial and the transverse components of the fields are space dependent so to determine the starting distance of the far field we need to examine the simultaneous satisfaction of these two properties for all θ and φ angular directions, where θ is the angle measured from z-axis and φ is the angle measured from the x-axis. The objective of this paper can be summarized in three points: First, this paper intends to illustrate that 2D2/λ formula, where D is the maximum dimension of the antenna and λ is the operating wavelength, is not universally valid, it is only valid for antennas where D ≫ λ. Second, this paper intends to compute a more specific constraint so instead of D ≫ λ we compute a threshold for D after which the 2D2/λ formula applies. Third, this paper intends to properly interpret D in the formula 2D2/λ when the antenna is operating over an imperfect ground plane. In this paper, we do not use 2D2/λ for antennas operating over an imperfect ground instead we use a formula which depends on the transmitting and receiving antennas heights over the air-Earth interface.

Where Does the Far Field of an Antenna Start? [Stand on Standards]

The far field of an antenna is generally considered to be the region where the outgoing wavefront is planar and the antenna radiation pattern has a polar variation and is independent of the distance from the antenna. Hence, to generate a local plane wave in the far field, the radial component of the electric field must be negligible compared to the transverse component. Also, the ratio of the electric and the magnetic far fields should equal the intrinsic impedance of the medium. These two requirements-that the radial component of the field should be negligible when compared with the transverse component and the ratio of the electric and the magnetic fields equal the intrinsic impedance of the medium-must hold in all angular directions from the antenna. So to determine the starting distance for the far field, we need to examine the simultaneous satisfaction of these two properties for all θ and φ angular directions, where θ is the angle measured from the z-axis and φ is the angle measured from the x-axis. It is widely stated in the antenna literature that the far field of an antenna operating in free space, where all the aforementioned properties must hold, starts from a distance of 2D2/Λ, where D is the maximum dimension of the antenna and Λ is the operating wavelength.

CAD mobile phone model calibration using experimental specific absorption rate data

International measurement standards have been elaborated to assess the specific absorption rate (SAR) compliance of mobile phones. The procedure to evaluate SAR pre-compliance of mobile phones using numerical modeling tools based on the finite difference time domain (FDTD) method is currently being developed by the international standardization committee of IEC/IEEE 62704-3. The uncertainty quantification of the SAR calculation using a computer-aided design (CAD) mobile phone model is a challenging task, yet to be fully addressed. Herein a procedure to quantify the model or structural uncertainty is proposed. It is based on the calibration of the CAD mobile phone model by experimental SAR data obtained using a flat phantom filled with the appropriate tissue equivalent liquid. The procedure is applied to two commercially available mobile phone models.

Defining the starting distance for the far field of antennas operating in any environment

The far field of an antenna is generally considered to be the region where the outgoing wavefront is planar and the antenna radiation pattern has a polar variation and is independent of the distance from the antenna. In this paper, the starting distance for the far field is defined for antennas operating in free space and over an imperfect ground plane. First, this paper intends to illustrate that 2D2 / λ formula, where D is the maximum dimension of the antenna and λ is the operating wavelength, is not universally valid, it is only valid for antennas where D >> λ. Second, this paper intends to compute a more specific constraint so instead of D >> λ we compute a threshold for D after which the 2D2 / λ formula applies. Third, this paper intends to properly interpret D in the formula 2D2 / λ when the antenna is operating over an imperfect ground plane. In this paper, we do not use 2D2 / λ for antennas operating over an imperfect ground instead we use a formula which depends on the transmitting and receiving antennas heights over the air-Earth interface.

Evaluation of the real-life exposure due to mobile phones in an indoor environment

The peak spatial-average specific absorption rate (SAR) of a mobile phone measured at maximum power level under laboratory condition is not representative of the real-life exposure. The real-life SAR is strongly dependent on the over-the-air (OTA) performance of the mobile phone as well as the propagation condition. An indoor environment is herein considered for the evaluation of the real-life exposure from three mobile phones. It is shown that on average the mobile phone with the best so-called SAROTA index-expressed as the ratio between the SAR and total radiated power (TRP) - exhibits the lowest real-life exposure.

Revision of the Standard Test Procedures for Antennas [Stand on Standards]

The antenna design, development, and measurement industry has long relied upon the IEEE 149-1979 IEEE Standard Test Procedures for Antennas to define procedures for the verification of antenna performance. This standard has become outdated and is due to be made inactive per IEEE Bylaws.