Bassam Harb

Chaos control of third-order phase-locked loops using backstepping nonlinear controller

Abstract Previous study showed that a third-order phase-locked loop (PLL) with sinusoidal phase detector characteristics experienced a Hopf bifurcation point as well as chaotic behavior. As a result, this behavior drives the PLL to the out-of-lock (unstable) state. The analysis was based on a modern nonlinear theory such as bifurcation and chaos. The main goal of this paper is to control this chaotic behavior. A nonlinear controller based on the theory of backstepping is designed. The study showed the effectiveness of the designed nonlinear controller in controlling the undesirable unstable behavior and pulling the PLL back to the in-lock state.

Chaos and bifurcation in a third-order phase locked loop

Abstract The chaos induced in a new type of phase locked loop (PLL) having a second-order loop filter is investigated. The system under consideration is modeled as a third-order autonomous system with sinusoidal phase detector characteristics. The modern of nonlinear theory such as bifurcation and chaos is applied to a third-order of PLL. A method is developed to quantitatively study the type of bifurcations that occur in this type of PLL’s. The study showed that PLL experiencing a Hopf bifurcation point as well as chaotic behaviour. The method of multiple scales is used to find the normal form near the Hopf bifurcation point. The point is found to be supercritical one.

ECG signal compression using combined modified discrete cosine and discrete wavelet transforms

A new hybrid two-stage electrocardiogram (ECG) signal compression method based on the modified discrete cosine transform (MDCT) and discrete wavelet transform (DWT) is proposed. The ECG signal is partitioned into blocks and the MDCT is applied to each block to decorrelate the spectral information. Then, the DWT is applied to the resulting MDCT coefficients. Removing spectral redundancy is achieved by compressing the subordinate components more than the dominant components. The resulting wavelet coefficients are then thresholded and compressed using energy packing and binary-significant map coding technique for storage space saving. Experiments on ECG records from the MIT-BIH database are performed with various combinations of MDCT and wavelet filters at different transformation levels, and quantization intervals. The decompressed signals are evaluated using percentage rms error (PRD) and zero-mean rms error (PRD1) measures. The results showed that the proposed method provides low bit-rate and high quality of the reconstructed signal. It offers average compression ratio (CR) of 21.5 and PRD of 5.89%, which would be suitable for most monitoring and diagnoses applications. Simulation results show that the proposed method compares favourably with various state-of-the-art ECG compressors.

Controlling Chaos in Josephson-Junction Using Nonlinear Backstepping Controller

In this paper, a nonlinear backstepping controller has been designed to control bifurcation as well as incipient chaos that has been experienced in the RCLSJ (shunted nonlinear resistive-capacitive-inductance) Josephson-Junction. The results show that the system, without controller, has a dangerous Hopf bifurcation point that lead to chaotic behavior. For certain values of the external direct current (I0), the system becomes chaotic. On the other hand, the nonlinear backstepping controller converts the chaotic region into a stable periodic solution region

Chaos and bifurcation in third-order phase locked loop

The chaos induced in a new type of phase locked loop (PLL) having a second-order loop filter is investigated. The system under consideration is modeled as a third-order autonomous system with sinusoidal phase detector characteristics. The modern nonlinear theory such as bifurcation and chaos is applied to a third-order PLL. A method is developed to quantitatively study the type of bifurcations that occur in this type of PLL. The study showed that this PLL experienced a Hopf bifurcation point as well as chaotic behaviour. The method of multiple scales is used to find the normal form near the Hopf bifurcation point. The point is found to be supercritical one.

A Batch-Based MAC Design With Simultaneous Assignment Decisions for Improved Throughput in Guard-Band-Constrained Cognitive Networks

The adjacent channel interference (ACI) resulting from imperfect filtering can severely degrade the performance of any wireless communication system. Despite this fact, most of previously proposed medium access control (MAC) protocols for cognitive radio networks (CRNs) were designed while ignoring the effects of ACI (assuming ideal filtering). The effect of ACI can be reduced by introducing guard bands (GBs). However, this solution comes at the expense of degrading spectrum efficiency. In this paper, we develop an efficient GB-aware MAC protocol that attempts at maximizing network throughput while improving fairness in CRNs. Unlike most of previously proposed GB-aware MAC protocols that perform channel assignment sequentially, our MAC performs the channel assignment for multiple CR links simultaneously (the so-called batch method). Batching enables concurrent channel assignment for multiple CR links, which consequently allows for concurrent data transmissions. Batching can be realized by introducing an admission control phase for CR users to share their control information. The batch method can effectively provide distributed decisions that achieve better throughput while reducing the number of GBs. Our MAC also allows the CR users to utilize the reserved GBs of primary networks under predefined FCC power constraints. Simulation results indicate that our protocol achieves significant performance improvement compared to previous GB-aware protocols.

THE HALF-PLANE PULL-IN RANGE OF A SECOND-ORDER PHASE-LOCKED LOOP

Abstract The pull-in range Ω p of a second-order, Type I phase-locked loop (PLL) is defined as the maximum value of loop detuning ωos for which pull-in occurs from anywhere on the PLLs phase plane. That is, pull-in is guaranteed from anywhere on the phase plane if |ω os | p . Simple approximations are available for computing Ω p . The concept is expanded here, and a definition is given for the PLLs half-plane pull-in range Ω 2 . Simply stated, pull-in is guaranteed from anywhere on the phase planes lower-half if 0 os 2 . Unlike the parameter Ω p , a simple approximation for Ω 2 is not available. However, a Galerkin based algorithm is presented for computing the PLLs half-plane pull-in range Ω 2 , and it is applied to a simple example.

Review and redesign of the curriculum of a Masters programme in telecommunications engineering – Towards an outcome-based approach

This article presents the methodology and results of the curriculum review of the Masters of Science programme in Wireless Communications offered by the Telecommunications Engineering Department at Yarmouk University in Jordan. The review is based on expert opinion collected through questionnaires and meetings about the programme and focuses on two main aspects: the first is relevance of the programme to the needs of local and regional telecommunications industry and the second is comparability to similar programmes in the EU. Through an extensive analysis of the collected data, a set of recommendations for improvement of the existing curriculum was developed. These recommendations were then used to redesign the curriculum with regard to contents, teaching methodology and assessment.

Effect of instructional software on achievement of undergraduate students in Digital Signal Processing

Traditional tools used in education, are increasingly more complemented with computer based Instructional software. This paper presents an interactive approach for teaching the Digital Signal Processing (DSP) course. The effect of the Instructional Software on the achievement of students in the subject of DSP is compared to the conventional teaching method.

A Masters Programme in telecommunications management – demand-based curriculum design

This paper presents a curriculum design approach for a Masters Programme in Telecommunications Management based on demand data obtained from surveying the needs of potential students of the proposed programme. Through online surveys disseminated at telecom companies in Jordan, it was possible to measure the demand for such a programme and to determine the required programme contents and specifications. The curriculum design is based on definition of programme outcomes and on using a house of quality approach (HOQ) to determine the list of courses required in the programme. Surveyed competencies are mapped to a long list of proposed courses in a HOQ in order to determine the importance of each of these courses. A final list of core and elective courses is then developed considering the contribution to programme outcomes and the academic standards.