Sierpinski monopole antenna with controlled band spacing and inputimpedance

A novel configuration of the Sierpinski triangular gasket antenna is proposed. A quasi-log-periodic performance was achieved for the operating bands of GSM, DECT and WLAN by using a new band spacing control technique. This design enhances the input matching performance to well over -10 dB with a 50 Ω feed     

Performance Analysis of Heterodyne-Detected Coherent Optical CDMA Using a Novel Prime Code Family

In this paper, a novel prime code, which is hereby referred to as ldquodouble-padded modified prime code,rdquo is introduced and employed in a synchronous optical code division multiple access for both spreading and despreading operations. We have analyzed this system signal-to-noise-ratio penalty as a function of the number of simultaneous users that is accommodated to maintain an appropriate value of the bit-error rate. In the analysis, the coherent binary-phase-shift-keying modulation is used, and at the receiver, signals are heterodyne detected and processed. In addition, in the analysis, both the receiver noise and multiple-access interference are investigated.     

Analysis of gain and saturation characteristics of a semiconductorlaser optical amplifier using transfer matrices

The transfer matrix method (TMM) has been applied to analyze the gain and saturation characteristics of semiconductor laser optical amplifiers. This method approximates the amplifier cavity by dividing it into M discrete subsections, and TMM has been applied to analyze the stepwise longitudinal field distribution at each subsection along the amplifier cavity. By incorporating also the carrier rate equations into the analysis, it has been shown that the approximation can accurately describe the carrier density and longitudinal field distribution along the amplifier cavity if M is sufficiently large (i.e., the size of each subsection is about an order of magnitude of one wavelength of the input signal). By assuming that the amplifier is biased below oscillation threshold such that the contribution of spontaneous emissions to the gain characteristics can be neglected, we have shown that our proposed method yields a fast and efficient algorithm in analyzing the gain and saturation characteristics of laser amplifiers. We have compared the results produced by our method to those analyzed using the average photon density (AVPD) approximation technique, as well as to experimental results on a 1.5-μm buried heterostructure semiconductor laser amplifier     

Fractal stacked monopole with very wide bandwidth

A parallel feed stacked fractal antenna using the square Sierpinski and diamond Sierpinski carpet is introduced. The design achieves a good input impedance match throughout the passband (1-20 GHz) but occasional slight mismatch occurs. Three different experimental results are shown and the measured gain of these antennas is generally >0 dBi. These antennas are suitable for applications in picocell environments for the operating bands of GSM, DECT and WLAN systems     

Shorted fractal Sierpinski monopole antenna

This paper describes novel configurations of shorted fractal Sierpinski gasket antenna. The antenna uses half the structure of a conventional Sierpinski gasket antenna and is folded over to be parallel to the ground plane, to form an element similar to that of the inverted L antenna. A quasi log periodic resonance behavior is obtained with a shorting pin placed at the far end of the antenna. Several configurations are shown and a design using two shorting pins which improves the bandwidth at the fundamental band is also demonstrated.     

Modified quadratic congruence codes for fiber Bragg-grating-basedspectral-amplitude-coding optical CDMA systems

We have constructed a series of new code families for the spectral-amplitude-coding optical code-division multiple-access (CDMA) system, and proposed new transmitter and receiver structures based on tunable chirped fiber Bragg gratings (FBGs). The proposed system has been analyzed by taking into account the effects of phase-induced intensity noise, shot noise, and thermal noise. We have also compared the performance of this system with that of a former system where a Hadamard code is used. It has been shown that the new code families can suppress the intensity noise effectively and improve the system performance significantly. When the effective power is large (i.e., >-10 dBm), the intensity noise is the main factor that limits the system performance. When the effective power is not sufficiently large, thermal and shot noise sources become the main limiting factors and the effect of thermal noise is much larger than that of shot noise     

A novel method for analysis of soliton propagation in opticalfibers

We have proposed a new technique to analyze the propagation behavior of solitons in an optical fiber. This technique is based on the Fourier series analysis technique (FSAT) which can consider fiber loss and third-order dispersion. Using this technique, the propagation of solitons in an optical fiber has been investigated. The results compare well with the well-known split-step Fourier method (SSFM). We found that for a given computational accuracy, in order to obtain the same results, we need fewer sampling points for FSAT compared with the SSFM     

Perturbed Sierpinski multiband fractal antenna with improved feeding technique

This paper describes the multiband behavior of a series of perturbed fractal Sierpinski gasket antennas. Sierpinski gaskets, with periodic ratios of 0.5, 0.65, and 0.75 were fabricated and tested. Two methods are presented that improve the inherently poor input impedance match of the antenna with a 50 /spl Omega/ port. Theoretical simulation is used to give an insight into the field distribution of the antenna as the perturbing ratio varies. Different properties and merits of the antenna due to perturbation were noted. These improved feeding methods will allow further flexibility to the application of these multiband antennas.     

Frequency transform synthesis method for cross-coupled resonator bandpass filters

In this letter, an improved synthesis method for equal-ripple cross-coupled resonator bandpass filter is proposed based on the frequency transform method and Atia's method. In this method, the conventional lowpass prototype method is revised by replacing the low pass prototype with the frequency transform method. The detailed element extraction procedure in z-domain is given. Also the coupling matrix reduction implemented by optimization algorithm is described. This method is powerful for filter synthesis with asymmetric frequency response and complex transmission zeros. The design examples are presented and the experimental results validate its effectiveness.     

Effect of phase shift position on spectral linewidth of the π/2distributed feedback laser diode

The dependence of the spectral linewidth on the phase shift position (PSP) of a phase-shifted distributed-feedback (DFB) laser diode is investigated theoretically, using the coupled wave model. In particular, the analysis is performed to find an optimum PSP so as to minimize the spectral linewidth of the laser diode. This optimum PSP is compared to that obtained by maximizing the stability of the laser oscillation. Since both narrow spectral linewidth and good stability are essential for the light source in coherent optical communications, the analysis revealed the suitability of using phase-shifted DFB laser diodes in coherent transmissions