Mohammad Shahrazel Razalli

Performance of PTS techniques with varied partition size in PAPR reduction of OFDM system

Orthogonal frequency division multiplexing (OFDM) is a promising modulation technique for transmitting large amounts of digital data through radio waves. One major drawback in OFDM communication is peak-to-average power ratio (PAPR). Mainly because of the nonlinearity of the high power amplifier, these results in high out-of-band radiation, inter-carrier interference, and bit error rate performance degradation. Partial transmit sequences (PTS), an attractive technique of PAPR reduction, provides significant PAPR reduction performance for (OFDM) signals. It essentially involves partitioning the OFDM data frame into disjoint sub-blocks. Adjacent partitioning (AP) scheme can be regarded as the best of the existing partitioning schemes when PAPR reduction performance and cost are considered together. In this paper, we study the impact of the size of PTS partitions on the performance through varying the size of the disjoint sub-blocks partition and comparing the PAPR reduction performance of three well known sub-block partitioning schemes namely Adjacent Partitioning (AP), Interleaved Partitioning (IP) and Pseudorandom Partitioning (PRP). Simulation results showed that performance of these PTS schemes largely depends on the chosen size of the partitions.

QPSK modulation using multi-port device

This paper investigates digital modulation transmitter using multi-port device. The multi-port device is a 6-port replacing the high cost mixer in conventional transmitter. The main objective of this paper is to develop the digital modulator based on six-port network using Agilent ADS (Advanced Design Simulation) simulation tool. The S-parameters of a fabricated six-port network are measured using network analyzer. All the 2-port measured data of the six-port network are then mapped into matrix 6×6 by using MATLAB. The mapped 6×6 matrix is then used to model the six-port network in ADS simulation. The six-port network can be functioned as a digital modulation by connecting port 1 to local oscillator and port 3 to port 6 to either open and short termination. The RF modulated signal is going out from port 2 of the six-port network. The QPSK (Quadrature Phase Shift Keying) symbols are dependent on the combination of open and short terminations which are controlled by SPDT (Single Pole Double Throw) switches. The simulation and analysis of the output result are observed in terms of symbol rate and frequency of local oscillator.

Hardware Implementation of Modeling Frequency Coded Serial Communication for Eurobalise Using ASK Module

This paper discusses about the modeling of frequency coded serial communication for the application of Eurobalise on hardware-based field programmable gate array (FPGA). The transceiver consists of FPGA and the ultra-high frequency (UHF) band amplitude shift keying (ASK) module. In the convention interface of the ASK transceiver module with the digital controller, noise has introduce into the channel. The noise in the output of ASK receiver has distorted the transmitted data causing the throughput of the wireless channel to be decreased. When the ASK module interfaces with the FPGA device, the noise from the output of the ASK receiver causing the receiving FPGA retarded. The purpose of the frequency coded serial data is to provide continuous specific frequency pulse train to the ASK transmitter. The original serial bit stream is then modulated in the pulse train with different frequency corresponding to the bit’s logic level. This technique has made the output of the ASK receiver to produce a very clean signal with extremely less noise. Hence, the receiver’s FPGA able to capture all the transmitted data accurately across traditional disciplinary boundaries, including computer hardware, algorithms, electronics interfacing and application domain.

MINIATURE TRIPLE-MODE DIPLEXER WITH GOOD SELECTIVITY

This paper presents a compact diplexer with high selectivity. The proposed diplexer employs two sets of triple-mode bandpass filters. Using this approach, the pair of even-mode resonant frequencies can be flexibly controlled by adjusting the characteristic impedance or electrical lengths of the two open-circuited stubs while the odd-mode resonant frequency remains at the fundamental resonant frequency. For a demonstration, a diplexer with two passbands centred at 1.50 and 1.70 GHz and the transmission zeros are created close to the passband edges which extremely improve the skirt selectivity. As a result, the proposed diplexer occupies an extremely small area, i.e., approximately 0.30λg × 0.35λg . The measured results are in good agreement with the simulated predictions.

Miniature microstrip bandpass filters based on quadruple-mode resonators with less via

This article aims to design of microstrip resonators in order to reduce size of microstrip bandpass filters in wireless communication systems. Characterized by both theoritical investigation and full-wave simulation, the proposed bandpass filters are designed consist of dual-band bandpass filters and quadruple mode bandpass filters with miniaturized size. The proposed filter is found to have benefits such that the even-mode resonant frequencies can be flexibly controlled while the odd-mode resonant frequency is reserved for the fundamental frequency. Since the structure of resonators is realized using common via holes, the difficulty and complexity of the fabrication process can be shortened. In order to achieve compact size, the total number of resonators is reduced so that the implemented resonators only occupy a small area.

Comparison of rectifier performance using different matching technique

This paper describes the design and implementation of the 4-stage Villard multiplier for RF energy harvesting. Each stage is a combination of two HSMS 2850 Schottky diodes and two capacitors for each stage. For ambient energy harvesting, the incident power is extremely small, thus an efficient rectifier is needed. The designed rectifier with the matching circuit is a good candidate since it is able to enhance the rectified output power up to 300% during -40dBm input power compared to the rectifier circuit alone.

Variable length adjacent partitioning for PTS based PAPR reduction of OFDM signal

Peak-to-Average power ratio (PAPR) is a major drawback in OFDM communication. It leads the power amplifier into nonlinear region operation resulting into loss of data integrity. As such, there is a strong motivation to find techniques to reduce PAPR. Partial Transmit Sequence (PTS) is an attractive scheme for this purpose. Judicious partitioning the OFDM data frame into disjoint subsets is a pivotal component of any PTS scheme. Out of the existing partitioning techniques, adjacent partitioning is characterized by an attractive trade-off between cost and performance. With an aim of determining effects of length variability of adjacent partitions, we performed an investigation into the performances of a variable length adjacent partitioning (VL-AP) and fixed length adjacent partitioning in comparison with other partitioning schemes such as pseudorandom partitioning. Simulation results with different modulation and partitioning scenarios showed that fixed length adjacent partition had better performance compared to variable length adjacent partitioning. As expected, simulation results showed a slightly better performance of pseudorandom partitioning technique compared to fixed and variable adjacent partitioning schemes. However, as the pseudorandom technique incurs high computational complexities, adjacent partitioning schemes were still seen as favorable candidates for PAPR reduction.

0 dB coupler employing slot technique on planar microstrip

Realization of crossovers is always a problem in the design of microwave integrated circuits. In many cases, when a high isolation between crossing strips is required in a rather large frequency band, it is preferable to avoid a trivial separation of the strips by a dielectric layer. This paper focuses on designing and developing a wideband 0 dB coupler on planar microstrip. in In this paper, the proposed 0 dB coupler is designed using square patch with slotted lines. To compare the performances of the proposed design, a conventional 0 dB coupler using double section branch line coupler is presented as well. A substrate Rogers RO4003C with dielectric constant of 3.38 and thickness of 0.508 mm at center frequency 2.4 GHz are used in both designs. They are compared in terms of the size, and their s-parameter performance. Both couplers developed with the aid of design tool CST Microwave Studio and fabricated using microstrip technology.

Effect of partition length variability on the performance of adjacent partitioing PTS in papr reduction of OFDM systems

Peak-to-Average Power Ratio (PAPR) reduction is an attractive research topic among the OFDM transmission research communities. Partial Transmit Sequence (PTS) has been a promising candidate out of the proposed PAPR reduction techniques without any distortion. In any PTS system, partitioning of the OFDM frame into disjoint sub-blocks is a crucial step. Adjacent partitioning (AP) is a rather simple partitioning scheme achieving attractive PAPR reduction performance. In this paper, we investigate effects of the length variability of disjoint sub-blocks on AP based PTS systems. In order to compare performance of variable length adjacent partitioning with the ordinary PTS scheme, we simulated other partitioning schemes, namely, interleaved, pseudorandom and fixed length adjacent partitioning for various types of modulation. Simulation results showed that the variable length adjacent partitioning is better than interleaved partitioning. However, it has worse PAPR reduction performance compared to the traditional adjacent and pseudorandom techniques.