A novel compact antenna for ultrawideband channel sounding is presented. The antenna is composed of a symmetrical biconical antenna modified by adding a cylinder and a ring to each cone. A feeding coaxial cable is employed during the simulations in order to evaluate and reduce its impact on the antenna performance. The optimized antenna demonstrates S11 below-10 dB and a stable omnidirectional radiation pattern robust against the cable effect over the frequency band 1.5-41 GHz despite its compactness (the maximum electrical dimension is of 0.29λmax, where λmax is the free space wavelength at the lowest frequency of operation). A prototype of the antenna is fabricated and tested. The simulated and measured S11 are in a good agreement. Measured radiation patterns confirm the pattern stability in terms of the direction of maximum radiation and 3 dB beamwidth.

The propagation of signals is affected by the characteristics of the materials in the medium. Hereof, the information about the material properties is of paramount importance when radio propagation is investigated. In this paper, the measured complex relative permittivity of 20 common materials in indoor environments (including plastics, wood and wood-based materials, glass, gypsum plaster and plasterboard, brick, and concrete) over the frequency band 0.2-67 GHz is shown. The dielectric properties are measured by using two open-ended coaxial probes. The single-pole Cole-Cole model is employed for fitting the measured data since most of the materials follow this model. Moreover, the fitting parameters for the multi-pole Debye model which can be used instead of the Cole-Cole one (it is more appropriate for FDTD applications) are given. Thus, an easy way for obtaining the data is provided which can be helpful when wideband propagation is considered.

Mobile terminals have become an integral part of people's everyday life. The ability of the handset to transmit and to receive power determines how good communication link it can establish. This paper presents results from a comprehensive study on the radio performance, in terms of total radiated power (TRP) and total isotropic sensitivity (TIS), of 16 mobile terminals, common in the Nordic countries, in different use scenarios -free space, talk mode using right and left hand phantom next to head phantom, and data mode with right hand phantom. The phones are tested following the standardized non-invasive procedure for 2G, 3G and 4G communication standards. It is found that there is a large spread in the performance among the tested phones even in free space (up to 9 dB for TRP and up to 5 dB for TIS) and the case is more severe when the user is located next to the handset. The results indicate that the vicinity of the user to the mobile terminal can lead to degradation up to 22 dB in the transmit performance and up to 8 dB in the receive performance.INDEX TERMS Mobile phone, antenna, user effect, body loss, OTA, talk mode, data mode, TRP, TIS.

An experimental study of the interaction between user's hand and an ultrawideband multiple-input multiple-output (MIMO) antenna array is presented for mobile terminals. The dualelement array covers the frequency ranges 698-990 MHz and 1710-5530 MHz with a good efficiency in free space. Depending on the standard, it can be used for channel sensing in cognitive radio networks or for communications in cellular networks. Hand phantoms for three usage scenarios are used for the investigation, namely, personal digital assistant (PDA) right hand, PDA left hand, and two hands. The absorption in the immediate located hand is the main factor causing degradation of the total efficiency (slightly affected by the hand induced changes in the S-parameters), reduction and imbalance in the antennas mean effective gain contributing to a deteriorated diversity gain. The user caused changes in the antennas radiation patterns reduce the correlation in the lower band which enhance the diversity gain and multiplexing efficiency. The exposure of the hand in each scenario is studied by the Specific Absorption Ratio (SAR).

The operation of antennas deployed in mobile terminals is affected by the presence of human tissue in their near-field region. Therefore, testing the antenna performance, when the radiator is located in close vicinity to the user, is of paramount importance for any handset. In order to conduct such a study, knowledge about the dielectric properties of relevant human tissues is needed. In this paper, the results for in vivo measured complex relative permittivity of the dry and wet human hand palm and fingertip of thumb are presented. For the sake of having a broader set of data, the palms of 22 individuals and thumbs of 16 individuals are tested at multiple points. The measurements are conducted over the frequency band of 5-67 GHz by using an open-ended coaxial probe. The single-pole Cole-Cole model is used for fitting the measured results. Furthermore, the fitting parameters for the multi-pole Debye model are extracted by using the Cole-Cole ones. The effect of the difference in the dielectric properties between dry and wet palm on the performance of a dual-element PIFA antenna array (operating in the band of 5.8-7.7 GHz) is numerically studied. Useful finding for antenna designers is that the S-parameters and radiation efficiency of the antennas are insensitive to the change in the complex permittivity of the hand. INDEX TERMSComplex relative permittivity, open-ended coaxial probe, palm, thumb, Cole-Cole model, Debye model, user hand effect.