A. K. AboulSeoud

A conformal conical phased array antenna for modern radars

In this paper a new conformal array antenna of conical structure has been proposed. A conical phased array antenna can steer the radar beam electronically in both azimuth and elevation to cover a hemi-sphere mesh surrounding the radar antenna. Beam steering can be accomplished either continuously or discretely at definite directions. The proposed technique not only overcomes the limitations of mechanical steering systems and surveillance radar dead cone but also improves the radar tracking capability. Moreover, it is suitable to be used in MIMO radars and enemy deception systems. Element weights of the conical phased array antenna are optimized using a genetic algorithm (G.A). The optimization process improves the beam pattern peak side lobe level (PSLL) while maintaining a narrow beam width. A high resolution phase shifter and adaptive attenuator have been used for each element to acquire both the desired phase and optimum weight for conical array beam pattern. Beam pattern is simulated and tested using a Matlab Program. Improvement achieved in both antenna gain and PSLL are 18.8 and 8 dB respectively. There is a 6° tilting angle and 24° half power beam width.

A simple 8-bit digital microcontroller implementation for chaotic sequence generation

This paper introduces a simple implementation of digital chaotic sequence generator. The implementation is based on using microcontroller ATMGA 16 to generate the chaotic map required for advanced encryption standard (AES) encryption scheme s-box and radar frequency agile control. The implemented circuit is simple, low cost and suitable for use with identification friend or foe (IFF) equipped with data encryption systems. The circuit also can changes the carrier frequency of the transmitted signal based on chaotic map, benefits a security and confidentiality to the radar waveform against Electronic Counter Measurement (ECM). The circuit generates 256 random sequences at different initial conditions and each of them has 256 sequences generated from different bifurcation parameters. The circuit is simulated under Matlab program environment and Proteus circuit simulation program. A security analysis for the implemented circuit is demonstrated. The results show the superiority of the circuit for generating the random sequences forming an efficient s-box for IFF system and radar frequency agility.

Error performance of free space optical MIMO systems in weak, moderate, and severe atmospheric turbulence channels

Atmospheric turbulence causes degradation in the performance of free space optical (FSO) transmission. This turbulence is referred to as scintillation. To mitigate this effect, a multiple input multiple output (MIMO) system is employed. This paper investigates and compares the performance of FSO MIMO systems in different atmospheric turbulence conditions such as weak, moderate, and severe when binary pulse position modulation (BPPM) is employed. In particular, single input multiple output (SIMO) system using BPPM technique is investigated with equal gain combining (EGC), selection combining (SC), and maximal ratio combining (MRC) diversity schemes. Moreover, the probability of error performance is evaluated using Monte Carlo simulations assuming different atmospheric turbulence channels.

Tunable optical buffer using a fiber bragg grating array and a widely tunable wavelength converter

This paper demonstrates a tunable optical buffer with widely variable time delays using an array of fiber Bragg gratings (FBGs) filter and tunable wavelength converters (WCs). The flexibility of the proposed system gives an exact required delay and, consequently, better output port utilization. This system is designed to be compatible with 10 to 40 Gbps RZ communication systems.

Indoor wireless optical communication systems: effect of ambient noise

Abstract. Many techniques using polarizers, differential detectors, and electrical filters are used to overcome the penalty induced by artificial light interference and are analyzed. These techniques are used to reduce noise current or remove it by using an electrical filter or a polarizer or both of them together. We are going to display the effect of noise voltage, flicker voltage of a tungsten lamp, and signal-to-noise ratio (SNR) of the systems by changing each parameter to reach the best solution for reducing the effect of noise on free space optics. This paper will show that the best SNR is obtained with the differential detector with a two orthogonal polarizer system and that the worst one is with the system of a single photodetector.

Impact of amplified spontaneous emission on the travelling wave semiconductor optical amplifier performance

The most important characteristic that affects the travelling wave-semiconductor optical amplifier (TW-SOA) performance is the amplified spontaneous emission (ASE) noise. This paper presents the SOA operation using the segmentation model that utilizes the rate equation employing the ASE noise. The impact of ASE noise on the total SOA gain response in absence and presence of input signals is investigated. Also the impact of ASE noise on SOA length for a single pulse and a packet of pulses and making comparison between them are introduced. As well as studying the dependence of gain uniformity on SOA length under the influence of ASE noise is clarified by calculating the gain standard deviation.

Introducing triangular lattices to dynamic photonic crystal structures for optical storage and processing

A dynamic photonic crystal structure based on a triangular lattice and GaAs is proposed for optical storage and processing. Preserving the translational invariance and the adiabaticity, the structure exhibits electromagnetic induced transparency and can compress larger bandwidth pulses than the previous square lattice models.

Optimum array weighting for minimum (SLL) using genetic algorithm

The goal of this paper is to optimize the array weighting in order to minimize the sidelobe level (SLL) of the phased array antenna without losing the beam width. The simulated antenna is linear array with 8 and 10 elements. Genetic algorithm has been used for the optimization process. The weights chosen to meet any specific criteria, the criterion is to minimize the sidelobe level with narrow beam width. The sidelobe level and beam width of the optimized weights are compared with those of three famous weights known as Hamming, Kaiser-Bessel, and Gaussian weights. The results show a good enhancement for the optimized weights. The sidelobe level (SLL) reduced by 8.3% and beam width (B.W) narrowed by 10% than results achieved by Hamming weights.

Compact low voltage CMOS rail-to-rail current conveyor

This paper presents a new low-voltage CMOS second generation current conveyor with a rail-to-rail linear voltage transfer characteristic. A pair of complementary NMOS and PMOS input circuits, configured as a voltage follower, in conjunction with current mirror arrangements are employed to implement this conveyor. SPICE simulation using 0.5 mum CMOS (BSIM3v3) process parameters have been carried out to verify the conveyor performance

D5. Wideband tunable MEMS phase shifters for radar phased array antenna

A wideband tunable MicroElectroMechanical System (MEMS) phase shifter is proposed for radar phased array antenna. A tuning circuit is added to modulate a narrow band phase shifter to achieve a bandwidth of about 200 MHz at 3 GHz central frequency which is suitable for radar applications. RF capacitors, inductors, and resistors are selected and optimized for the tuning circuit to achieve a phase response suitable at the pre-mentioned bandwidth. The overall phase response of the phase shifter is an algebraic sum of the narrow band phase shifter and the tuning circuit phase responses. The phase shifter is designed, simulated and tested using Advanced Design System (ADS) software either with or without using tuning circuits. This type of phase shifters can give high performance and resolution at a bandwidth 20 times wider than the normal switched line phase shifter.