Majlesi Journal of Telecommunication Devices
Volume:2 Issue: 4, Dec 2013

Nowadays, it is very important to receive high quality wideband signal in the presence of interference and unwanted environmental effects. To achieve this goal, one way is to improve the quality of signal and decrease the undesired phenomena by antenna array beamforming. In this paper, first we investigate the problem of wideband beamforming in frequency domain considering the effect of interference signals. Then, we present a new low-complex efficient idea to jointly decrease the effect of interference signal and increase the Signal to Interference plus Noise Ratio (SINR). Afterwards, another idea is proposed which increases the value of SINR using some changes in the main beampattern generator. Finally, the performance of new proposed method is compared with previous work by simulations in MATLAB software. Simulation results show that the proposed wideband frequency invariant beamforming approach offers faster convergence and higher gain for main signal with respect to previous work.

Radio frequency (RF) micro electro-mechanical systems (MEMS) switches are rapidly replacing the PIN diodes and field-effect transistors (FET). Linear behavior, low power consumption, low insertion loss, high isolation, improvement power handling and etc. are benefits of MEMS switches. This paper presents a high isolation RF MEMS capacitive switch with two shunt beams for Ka-band (27-40 GHz) applications such as in communications satellites. Simulation results using Ansoft’s high frequency simulation software (HFSS) at Ka-band shows in the down-state of switch, the isolation (S21) is > 47 dB and return loss (S11) is < 0.3 dB. In the up-state, the insertion loss (S21) is less than 0.15 dB and the return loss (S11) is more than 18 dB. The pull down voltage of designed switch is 5.13 V and down-state to up-state capacitance ratio (Cd/Cu=12.11pF/0.137pF) is 88.39. Also a novel index material (IM2) is proposed to determine optimum material using Ashby approach. In this paper the Aluminum (Al) is chosen for the membrane for having low pull down voltage and silicon nitride (Si3N4) is chosen for dielectric for having faster switching speed and larger down-state capacitance.

This paper propose a method in order to achieve a suboptimum permutation distance for every multi-input multi-output orthogonal frequency-division multiplexing (MIMO-OFDM) block code in the absence of perfect channel state information at the transmitter. As a matter of fact, our method is based on artificial delay power profiles (ADPPs) to obtain this permutation distance. Furthermore, we show that the performance of every MIMO-OFDM block code can be improved by applying our proposed suboptimum permutation distance in comparison with fixed, random and maximum permutation distance. Also, simulation results show that the performance of recent MIMO-OFDM block codes can be improved more than 3 dB by considering the proposed permutation.

Using ESM, RWR and ARM missiles pose significant limitations to the performance of the radar systems in new battles. In these wars, MTI radars are commonly used with high Power to achieve long ranges, therefore they are easily detectable by the enemy EW receivers, and so they lose their effectiveness. In addition to having the ability of anti-Jamming and good ECCM, the radar systems should to use suitable CESM features to reduce the effectiveness of hostile ESM systems. So ability of low interception or LPI has become an important factor in radar systems. On the other hand, interception receivers must also develop detection capabilities and improve their performance in parallel to the LPI radars. The LPI radar signals are used in so many different waveforms and thus there are different ways to detection of these signals. In this paper, WVD and CWD techniques are used in order to detection FMCW signals (LPI signal).

A new ultra wideband 5 to 50 GHz and low power single ended input, differential output active balun using 0.18µm CMOS technology is presented in this paper. Using a pair of common-source and common gate NMOS transistors with utilize active load PMOS transistors. Total power consumption of the proposed active balun circuit is 5mw at the supply voltages of ±1.2v much less than 11.5mw of the conventional active balun.

Due to the increasing need for high-rate service and maintain the quality of service in wireless networks, wireless telecommunications world is now moving into the fourth generation of the third generation.Contacts fourth-generation wireless communication system requires a maximum of efficiency. In order to develop strategies to increase the efficiency of payment that requires analysis of opportunistic scheduling and spectrum reuse in cellular networks based on a diversity of relay.One of the devastating effects of wireless communication systems is fading. To address the problem of diversity uses. Fade the diversity of ways of coping with adverse effects and improve the performance of the system.In line with the diversity and multi-system planning and optimize spectrum reuse in relay-based cellular networks has been tried that in this paper analyzes the spectral efficiency performance in a multi-channel to be dealt The results stated that the procedure was done very good performance even with a small number of users in the Fade is Riley. Orthogonality between sub-channels in frequency relays operate based on the frequency of the source and relay.

Supervisory Control and Data Acquisition (SCADA) is a term used to refer to systems and networks that monitor, manage, and control automation, production and distribution of considred system. In this paper, we describe an overview of SCADA system and its supetibilities and commendations for implementing security and protection in this system.