Marijan Herceg

A Method for the Schmitt-Trigger Propagation-Delay Compensation in Asynchronous Sigma–Delta Modulator

This brief provides the mathematical analysis of the Schmitt-trigger propagation-delay influence on the asynchronous sigma-delta modulator (ASDM) output-signal frequency spectrum. Beside the propagation delay, the Schmitt-trigger slew-rate impact has been also presented. Based on the mathematical analysis, a method for the Schmitt-trigger propagation-delay compensation has been proposed. The method is implemented by introducing hysteresis-level modulation. The first-order ASDM simulation and measurement models have been proposed for the propagation-delay influence to the ASDM output-signal frequency and for the compensation method verification. The measurement and simulation results for the proposed method confirm the ASDM output frequency spectrum improvement.

Pulse interval modulation for ultra-high speed IR-UWB communications systems

This paper analyzes performances of the Pulse Interval Modulation (PIM) scheme for impulse radio ultra-wideband (IR-UWB) communication systems. Due to the PIM anisochronous nature, a tap delay line (TDL) coded division multiple access (CDMA) scheme based on strict optical orthogonal codes (SOOC) is proposed. This scheme is suitable for multiuser high-speed data asynchronous transmission applications because the average symbol length is shorter than in Pulse Position Modulation (PPM) schemes and it needs only chip synchronization. The error probability over the additive white Gaussian noise (AWGN) channel is derived in the single- and multi-user environment and compared with other modulation schemes.

Limit cycle frequency jittering of an asynchronous sigma-delta modulator

This paper presents limit cycle frequency jittering of a first order Asynchronous Sigma-Delta Modulator (ASDM) implemented with Schmitt trigger. Particular interest is placed on a jitter of a Schmitt trigger hysteresis voltage (hysteresis jitter). Hysteresis jitter has been modeled in MATLAB® Simulink and the model simulation has been compared with measurements for first ordered ASDM. Both simulation and measurement show that ASDM model limit cycle frequency depends on the hysteresis jitter.

Frequency-translated differential chaos shift keying for chaos-based communications

Abstract In this paper, an efficient, differential chaos shift keying (DCSK) method, known as frequency-translated DCSK (FT-DCSK), is proposed. Ordinary DCSK is difficult to incorporate using CMOS integrated circuits because of the long wideband delay line that is required to separate reference and data chaotic sequences into two time-shifted slots of each frame. Another disadvantage of DCSK is the repetition of chaotic sequence in reference and data slots, which decreases data security and bandwidth efficiency. In the proposed method, the usage of a delay line is avoided by frequency translation of the reference chaotic sequence over the frame time. Frequency translation is achieved by amplitude modulation of two orthogonal sine carriers with reference chaotic sequences. As a result, the FT-DCSK scheme avoids the usage of wideband delay lines and increases the bandwidth efficiency. The analytical expression for bit error rate (BER) performance is derived and compared with simulation results. Finally, the obtained performance results are compared with similar modulation schemes. The proposed FT-DCSK scheme exhibits promising performance based on BER results.

Permutation Index DCSK Modulation Technique for Secure Multiuser High-Data-Rate Communication Systems

A new noncoherent scheme called Permutation Index Differential Chaos Shift Keying (PI-DCSK) modulation is proposed in this paper. This original design aims to enhance data security, energy and spectral efficiencies, compared to its rivals. In the proposed PI-DCSK scheme, each data frame is divided into two time slots in which the reference chaotic signal is sent in the first time slot and a permuted replica of the reference signal multiplied by the modulating bit is sent in the second time slot. In particular, the bit stream is divided at the transmitter into blocks of

Correlation-Multi-Delay-Shift-Keying for Chaos Based Communications

n+1

Performance of hybrid pulse shape amplitude modulation for UWB communications systems over multipath channels

bits, where

Method for Bandwidth Efficiency Increasing of M-ary PPM Transmitted-Reference UWB Communication Systems

n

Multi Pulse Position Amplitude Modulation for ultra-high speed time-hopping UWB communication systems over AWGN channel

mapped bits are used to select one of the predefined reference sequence permutations, while a single modulated bit is spread by the permuted reference signal just mentioned. At the receiver side, the reference signal is recovered first, then all permuted versions of it are correlated with the data-bearing signal. The index of the correlator output with maximum magnitude will estimate the mapped bits, while the output content of the corresponding correlator is compared to a zero threshold to recover the modulated bit. Moreover, a new multiple access method based on the proposed scheme is described and analysed. Analytical expressions for the error performance in single-user and multiuser environments are derived for additive white Gaussian noiseand multipath Rayleigh fading channels, respectively. Furthermore, the performance of the proposed PI-DCSK system is analysed and compared with other noncoherent chaotic modulation schemes and is found to be promising.

Ultra-wideband transmitter based on integral pulse frequency modulator

In this paper, the new correlation-multi-delay-shift-keying (CMDSK) modulation scheme for chaos based communications is proposed. In this scheme the information-bearing time delayed chaotic sequence is subtracted with original one. As a result, the higher data rate is obtained by defining a different time delays in order to maps a multiple bits within a frame. The number of transmitted bits per symbol is proportional to the number of possible delayed sequences. The analytical expression for error rate, based on Gaussian approximation, is derived and the results are confirmed with Monte-Carlo simulation. The performance of the CMDSK are analyzed and compared with differential-chaos-shift-keying (DCSK) and correlation-delay-shift-keying (CDSK). The result shows that CMDSK scheme outperforms DCSK and CDSK scheme with the increase of spreading sequence M. Due to the larger number of delay lines and correlators at transmitter and the receiver, CMDSK requires higher hardware complexity.