An improved version of the compensation method based on rod reflectors is presented. In this version, one or more metallic rod reflectors are installed near a transmitting antenna in order to create an additional field needed for decreasing the antenna's field inside the user's head, hence removing the need for auxiliary radiators. Both single and double rod reflectors are investigated. It is shown that using two rod reflectors, the field at the compensation point decreases by at least 7.5 dB in the frequency range of 850–2200 MHz. Using a single rod the reduction factor is above 5.4 dB in the same frequency band. Using the proposed rod-antenna structure with a single reflector, the peak specific absorption rate (SAR1g) and the total SAR measured at 1 GHz were reduced by 7.7 and 8.9 dB, respectively. With two reflectors, the SAR reduction factor for peak SAR (1 g) and total SAR levels were, respectively, 9.5 and 10.2 dB. The simulations and experimental results obtained so far show that the developed rod-antenna structures can be used as an effective method for SAR reduction.

Use of Rod Reflectors for SAR Reduction in Human Head

An antenna including a ground plane region, a feed element having associated with it a first reactance and a coupling element having associated with it a second reactance, the second reactance being of opposite sign to the first reactance, the coupling element being coupled to the feed element and to the ground plane region and being located in close proximity to the ground plane region, wherein an impedance and hence a resonant frequency of the antenna depend on the first and second reactances.

Distributed coupling antenna

A compensation method for reducing the irradiation of the head of a cellular phone user without degradation of the far field is analyzed. This method uses two radiators that are located in the near region of each other, and create a weak field area in this region. The impacts of the mutual coupling between closely located radiators on the input impedance, current distribution, and fields of the radiators are studied. It is shown that the structure of two closely spaced monopoles is equivalent to the superposition of two basic structures: a two-wire open-ended line, and a single monopole. The shape and dimensions of the dark spots and the irradiation-reduction factor are determined. To facilitate the field calculations in the near zone of the antennas, a method based on replacing a piecewise-homogenous medium by an equivalent homogenous medium is used. The calculations and the experimental results in the presence of the head qualitatively agreed.

Cellular Phone Antenna with a Small Irradiation of the Human Head

A proposal is put forward for an innovative method of multiple access, termed frequency Bank signal (FBS). The major advantage of FBS is that the error probability is almost non-sensitive to, either, the Doppler effect, separate signal delay or to the negative effect of reflected signals. In addition, FBS signals do not require special pilot or equalisation signals.

System free of channel problems inherent in changing mobile communication systems

Teknologi Long Term Evolution (LTE) dikembangkan dengan tujuan untuk mengurangi biaya yang dikeluarkan oleh pengguna maupun operator jasa telekomunikasi, memperluas daerah jangkauan, menambah kapasitas sistem, dan mengurangi delay. Dengan spesifikasi yang tinggi, LTE diharapkan mampu memberikan kemudahan pelanggan dalam mengakses layanan Voice over IP, Streaming, dan Video Conference. LTE diharapkan mampu memberikan layanan dengan besar throughput yang tinggi dan delay yang rendah. Padahal tidak semua user membutuhkan throughput yang sama besar namun yang dibutuhkan adalah kesesuaian pengendalian delay dan fairness index untuk setiap user dengan tetap memperhatikan batasan throughput. Untuk mendapatkan kinerja dan hasil yang maksimal tersebut pada LTE diperlukan sistem algoritma penjadwalan yang baik. Pada penelitian ini, dianalisis performansi LTE dengan parameter Delay, Packet loss, Throughput, dan Fairness Index menggunakan algoritma penjadwalan Proportional Fairness dan Log Rule pada LTE-Simulator dengan skenario menggunakan trafik VoIP, Video dan Best Effort. Hasil penelitian ini menunjukan bahwa penjadwalan algoritma Proportional Fairness lebih baik dalam menangani layanan VoIP, sedangkan algoritma Log Rule lebih baik dalam menangani layanan Video. Hal ini menandakan kedua algoritma ini sangat cocok digunakan untuk jaringan LTE dengan kondisi trafik layanan real-time, tetapi tidak untuk layanan non real-time seperti layanan Best Effort

/pdf/analisa-performansi-algoritma-penjadwalan-proportional-1vjj35ylm2.pdf

Analisa Performansi Algoritma Penjadwalan Proportional Fairness Dan Log Rule Dengan Skenario Multicell Pada Sistem 3GPP LTE

In this article, I propose an innovative method of multiple access, known as Frequency Bank Signal (FBS). FBS combines the phase shift compensation used in the PAL-TV system, the OFDMA principle and the spread spectrum concept with Walsh functions.

The main advantage of using an FBS is that the error probability is almost non-sensitive to the Doppler Effect, separate signals delay and to the influence of fading. In addition, the FBS signal is free of special pilot, synchronization or equalization signals.

http://www.wseas.us/e-library/conferences/2006venice/papers/539-197.pdf

Wireless mobile communication systems without pilot signals

The mutual effect of electric dipoles located in the near region of each other is considered. The problem is solved with due account of that the space is a heterogeneous medium with an equivalent permittivity. Calculations are based on the theory of folded dipoles. It is shown that by means of a compensation method one can produce a weak field in a given area and diminish a user's irradiation. The calculation and experimental results are presented and validate the high efficiency of the compensation method.

Near region field of antennas in piecewise-homogeneous media

Use of compensation method for creation of weak field area located above an antenna feed point is considered. Structure comprising two additional radiators, which are placed symmetrically with respect to the straight line passing through a main radiator feed point and a dark spot center and create the same fields, is presented.

Dark spot shift along a vertical line

A novel monopole internal antenna for mobile handsets is presented. The antenna, called the MB antenna, is a modified monopole whose radiating element is implemented in parallel proximity of a ground plane hence allowing for use as an internal antenna in handset applications. Simulation studies indicate that the proposed MB antenna has superior performance over PIFA antennas commonly used in modern handsets. Advantages include compact size, high gain and high efficiency. These characteristics make it very promising to use the proposed MB antenna in mobile handsets, including enhanced SAR reduction capabilities. The principle, design procedure, simulation results and comparison with PIFA also presented.

http://www.wseas.us/e-library/conferences/2009/vouliagmeni2/CIT/CIT-16.pdf

Cell phone antennas, problems and solutions

The field of a finite length monopole whose feed point is raised (sleeve antenna) is calculated. Its behavior is similar to a dipole with two feed points. The mutual coupling between closely located radiators of this type, when used in the compensation method, is considered.

M. Bank

Papers

Wireless mobile communication systems without pilot signals

Near region field of antennas in piecewise-homogeneous media

Dark spot shift along a vertical line

Cell phone antennas, problems and solutions

A monopole with raised feed point