This paper proposes an accurate and efficient method to calculate probability distributions of pulse-shaped complex signals. We show that the distribution over the in-phase and quadrature-phase (I/Q) complex plane is obtained by a recursive probability mass function of the accumulator for a pulse-shaping filter. In contrast to existing analytical methods, the proposed method provides complex-plane distributions in addition to instantaneous power distributions. Since digital signal processing generally deals with complex amplitude rather than power, the complex-plane distributions are more useful when considering digital signal processing. In addition, our approach is free from the derivation of signal-dependent functions. This fact results in its easy application to arbitrary constellations and pulse-shaping filters like Monte Carlo simulations. Since the proposed method works without numerical integrals and calculations of transcendental functions, the accuracy degradation caused by floating-point arithmetic is inherently reduced. Even though our method is faster than Monte Carlo simulations, the obtained distributions are more accurate. These features of the proposed method realize a novel framework for evaluating the characteristics of pulse-shaped signals, leading to new modulation, predistortion and peak-to-average power ratio (PAPR) reduction schemes.

We discuss the spectral efficiency of orthogonal frequency-division multiplexing (OFDM) signals widely adopted in practical systems from a viewpoint of their power spectral density property. Since the conventional OFDM does not make use of pulse shaping filter, its out-of-band (OOB) spectrum may not be negligible especially when the number of subcarriers is small. Thus, in practice, windowing is applied to mitigate OOB emission by smoothing the transition of consecutive OFDM symbols, but its effectiveness has not been well investigated. Furthermore, OFDM signal suffers from nonlinear distortion associated with its high signal peak-to-average power ratio (PAPR), which also leads to OOB radiation. We examine how power amplifier nonlinearity affects the spectral efficiency based on the theoretical results developed in the literature.

An artificial transmission line with variable capacitors as its shunt elements, also known as a nonlinear transmission line, can be used to generate pulsed waveforms with short durations. In this work, the variable capacitors are implemented using ferroelectric materials. Analysis and experimental results of such a ferroelectric-based artificial transmission line are presented. The differential equation that describes the nonlinear transmission line is derived and solved. The analytical expression for the solitary waves propagating along the line is found. An artificial transmission line is fabricated using thin-film barium--strontium--titanate capacitors and commercially available chip inductors. The fabrication process of the ferroelectric-based artificial transmission line is described. On-wafer characterization of the line is performed. Measurement results show that, with proper dc bias and substantial input power, a sinusoidal input waveform turns into a bell-shaped pulse train at the output, demonstrating the pulse-shaping capability of the ferroelectric-based artificial transmission line.

A K-exponential filter is derived and utilized for pulse shaping to reduce peak to average power ratio (PAPR) without intersymbol interference (ISI). While keeping the same bandwidth, the frequency responses of the filters vary with different values of the parameter k. The minimum PAPR is associated with a value of the parameter k when the roll-off factor α is specified. Simulations show that the PAPR can be reduced compared with the raised cosine (RC) filter in various systems. The derived pulse shaping filters also provide better performance in PAPR reduction compared with the existing filters.

An ISI-free power roll-off pulse, the roll-off characteristic of which is tunable with one power parameter, is proposed. It is shown that the proposed pulse is advantageous in terms of the probability of error for pulse detection in the presence of a timing error among currently known good pulses, among which the raised cosine pulse, "better than" raised cosine pulse, and polynomial pulse are considered.

In this paper, the effect of the impulse response of pulse shaping filters on a fractional sampling orthogonal frequency division multiplexing (FS OFDM) system is investigated. FS achieves path diversity with a single antenna through oversampling and subcarrier-based maximal ratio combining (MRC). Though the oversampling increases diversity order, correlation among noise components may deteriorate bit error rate (BER) performance. To clarify the relationship between the impulse response of the pulse shaping filter and the BER performance, five different pulse shaping filters are evaluated in the FS OFDM system. Numerical results of computer simulations show that the Frobenius norm of a whitening matrix corresponding to the pulse shaping filter has significant effect on the BER performance especially with a small numbers of subcarriers. It is also shown that metric adjustment based on the Frobenius norm improves BER performance of the coded FS OFDM system.

A procedure is developed to construct a time-limited pulse for its use in the short-range impulse radio communications. The even-numbered shifts of the pulse constitute a train of overlapping pulses. The pulses are intentionally made orthogonal to the second derivative of one another. This orthogonality makes it possible to detect the received pulses, which are assumed to be the second derivative of the transmitted pulses, by means of correlation with the original pulses. An example pulse is presented that complies with the FCC regulation for indoor ultra-wide bandwidth radio communications.

This paper proposes wavelet packets for use in ultra wideband communications. The pulse shapes that are generated are quasi orthogonal and have almost identical time duration. After normalization, an M-ary signaling set can be constructed allowing higher data rate. Finally, the performance of such a system when multipath propagation occurs is investigated by computer simulations. In order to combat multipath fading, a Rake receiver using coherent channel estimation is designed. This channel estimation is carried out using adaptive algorithms such as least-mean square (LMS), normalized least-mean square (NLMS), or recursive least square (RLS) algorithms which adapt the received signal given a reference signal.

The system uses spectral shaping of a supercontinuum source followed by wavelength-to-time mapping to generate ultra wideband RF waveforms with arbitrary modulation. It employs an adaptive computer control to mitigate the non-ideal features inherent in the optical source and in the spectrum modulation process. As proof of concept, ultra-wideband frequency hopped CDMA waveforms are demonstrated.

The reverse link bandwidth efficiency of a spectrally overlapped CDMA system with fast transmit power control is evaluated to find the optimum overlapping, where the bandwidth efficiency is defined as the maximum aggregate bit rate of all subsystems per unit bandwidth (bps/Hz). Single and multiple cell environments are considered. Besides the rectangular chip pulse, the impact of a pulse-shaping filter is discussed. It is found that the raised cosine spectrum pulse shaping helps to increase the bandwidth efficiency and strict pulse shaping filter problem can be avoided if a large number of subsystems are overlapped. It is also found that the optimum carrier spacing remains unchanged irrespective of the power delay profile shape of the multipath channel, whether multipath fading exists or not, and whether a single cell or multiple cell system is considered. However, the bandwidth efficiency strongly depends on them and the impacts of the related parameters are discussed.

We propose and describe a new configuration for splitting and combining operations of high-speed amplitude-modulated optical signals between the two interacting beams by using two-wave mixing in photorefractive Cu-doped (K0.5 Na0.5)0.2 (Sr0.61 Ba0.39)0.9 Nb2O6 (Cu-KNSBN) crystal. These operations are simultaneously achieved by changing the intensity ratio of the two incident beams. We also apply this scheme to a photorefractive pulse shaping in the time domain that consists of two amplitude-modulated beams that are coupled automatically through two-beam interactions in the crystal. Some preliminary experimental results are presented and discussed.