Fading correlation and its effects in the capacity of multi-element antenna systems, IEEE Trans Commun 48 (2000), 502- ABSTRACT: In this article, a new compact defected ground structure (DGS) low pass filter (LPF) with wide rejection band, low insertion loss in the stopband, and sharp transition from passband to stopband is proposed. The prototype LPF is composed of three repetitive DGS elements with open stubs to act as a compensated capacitance. Each single DGS element consists of multisections of T-shaped slots. The filter is then realized as a multilayer structure to achieve size reduction and enhance the filter response. The proposed filter has been fabricated and measured. The agreement between the simulated and measured results confirms the effectiveness of the proposed concept. Finally, multilayer LPF is transformed to band pass filter using J-inverter method.

The deterministic ear-to-ear on-body channel is modeled by the use of a number of elliptically shaped paths. The semi-major axes of the elliptically shaped paths are adjusted such that they trace the outline of the head. The path gain converges when the number of paths is increased, such that the head is modeled more accurately, and the radiation pattern is sampled in more points. The model is able to take the on-body radiation pattern of the antenna, as well as arbitrary head contours into account. The model is validated by the use of measurements and Ansys HFSS simulations on the specific anthropomorphic mannequin (SAM) head. The model is used with a genetic algorithm in order to synthesize a radiation pattern that is optimal for use with the ear-to-ear on-body channel. The radiation pattern is synthesized in terms of the spherical wave expansion coefficients of the hypothetical small antenna. The variation in the ear-to-ear on-body path gain, due to perturbations of the shape of the nominal SAM head, is studied by the use of a Monte Carlo analysis. The analysis revealed that the path gain that is obtained with a single on-body radiation pattern may vary up to 25 dB.

Abstract-A novel concept for an electrically-small on-body antenna targeted for 2.4 GHz ISM band custom in-the-ear (ITE) hearing instrument (HI) applications is introduced. The antenna is based upon a cavity-backed design in order to take advantage of the maximum volume available in the ear while providing isolation from the user's body, and it occupies only 40% of the volume of the sphere with radius a = 12 mm. The antenna is implemented on a realistic 3D-printed lossy substrate and exhibits high efficiency of 70% and 22%, and a 6-dB impedance bandwidth of 108 MHz and 149 MHz, when the antenna is measured in free space and ITE, respectively. A measurement campaign conducted in free space and on a specific anthropomorphic mannequin (SAM) head with ears shows that the radiation pattern is optimal for HI applications. Furthermore, the antenna is primarily polarized normal to the surface of the head to ensure the best on-body path gain. This is substantiated by the study of the ear-to-ear (E2E) path gain, which is measured and compared to analytic and numerical results.Index Terms-Cavity-backed antennas (CBA); conformal antennas; electrically small antennas (ESA); medical devices; onbody communications; wearable antennas; wireless body-area networks (WBAN).

A cavity backed coplanar waveguide (CPW) to coplanar strip (CPS) -fed logarithmic uniplanar spiral antenna, which covers a 9 to 1 bandwidth with a return loss better than I O dB from 0.4 to 3.8 GHz is presented. A wideband balun is used to accomplish the transition from the unbalanced CPW transmission line to the balanced CPS transmission line. The balun exhibits an insertion loss of less than 3 dB in a frequency band from sub 100 kHz and up to a frequency of 3.85 GHz. The numerical results presented are based on simulations using the lE3D Version 6.03 for Windows 98 on an INTEL Celeron 338 MHz computer. The obtained numerical results are in good agreement with experimental data. The spiral antenna is designed and prototyped for the FR-4 substrate. By placing the antenna on the FR-4 substrate it yields a low cost solution, which indeed is an advantage. Simulations have shown that the input impedance remains essentially constant over a bandwidth, which is larger than 1 1 to 1. The simulated as well as the measured input impedance for the spiral antenna is 80 R. Measurements in an anechoic chamber have been made in order to measure the radiation pattern and the directivity of the antenna. The cavity backed spiral antenna exhibits a unidirectional radiation pattern, due to the absorbing material. It is noted that only half of the input power is transformed into radiated power due to the presence of the absorber. The simulated performance of the spiral antenna is very promising. The simulations indicated that the antenna has a radiation efficiency of more than 70 % and an axial ratio and a return loss better than 3.5 dB and I O dB, respectively, in the frequency band from 0.4 to 3.8 GHz, i.e., a 9 to 1 bandwidth.

SUMMARYThe influence of mutual coupling on the envelope correlation between two identical planar inverted F-antennas (PIFA) are investigated. The capacity of a multiple-input multiple-output (MIMO) antenna system strongly depends on the correlation between the antennas. By placing two antennas in a fixed area, it is found that the envelope correlation could be halved simply by proper mutual orientation. The set-ups that maximise the distances between the open ends of the PIFAs yield the lowest mutual coupling as well as the lowest envelope correlations. It is found that the envelope correlation is 0.8 when the PIFAs are oriented in parallel. The envelope correlation can be decreased to 0.4 by rotating one of the PIFAs by 180 degrees.

A novel in-the-ear (ITE) antenna solution for hearing instruments that operates at 2.45 GHz is presented. The antenna consists of a quarter wave monopole and a ground plane that are placed in the ear. The simulated path gain |S 21 | is −86 dB and the measured path gain is −80 dB. Simulations and measurements show that the antenna covers the entire 2.40-2.48 GHz industrial, scientific and medical (ISM) band. It is the first ever ITE-antenna solution that demonstrates the possibility of establishing an ear-to-ear link by using a standard Bluetooth chip.Introduction: Wireless body area networks have been researched increasingly in recent years. Significant interest has been shown within the hearing instrument (HI) industry to make ear-to-ear (E2E) communication possible. This increases the capability of the HIs to restore hearing loss. A special interest has been shown for the industrial, scientific and medical (ISM) band from 2.40 to 2.48 GHz. This band is worldwide and enables connectivity from HIs to phones and other accessories with Bluetooth. Several antennas for this purpose have been presented, but mostly for the behind-the-ear HIs, as in [1], which has also been used in commercial products. For in-the-ear (ITE) HIs, the antennas presented in the literature have been either non-feasible to implement [2] or very narrow band [3]. The ITE antennas proposed in [2, 3] yield an E2E path gain (S 21 ) below −90 dB on phantom heads with no outer ear. Therefore, a novel ITE antenna for HIs with improved performance is needed and such is presented in this Letter.

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