Design of Acoustic Bifocal Lenses Using a Fourier-Based Algorithm

In this work, we develop a new design method based on fast Fourier transform (FFT) for implementing zone plates (ZPs) with bifocal focusing profiles. We show that the FFT of the governing binary sequence provides a discrete sequence of the same length, which indicates the location of the main foci at the ZP focusing profile. Then, using reverse engineering and establishing a target focusing profile, we are capable of generating a binary sequence that provides a ZP with the desired focusing profile. We show that this design method, based on the inverse fast Fourier transform (IFFT), is very flexible and powerful and allows to tailor the design of bifocal ZPs to achieve focusing profiles with the desired foci locations and resolutions. The key advantage of our design algorithm, compared to other alternatives presented in previous works, is that our method provides bifocal focusing profiles with an absolute control of the foci locations. Moreover, although we analyze the performance of this novel design algorithm for underwater ultrasonics, it can also be successfully extended to different fields of physics, such as optics or microwaves, where ZPs are widely employed.

PAPR Reduction in UFMC for 5G Cellular Systems

Universal filtered multi-carrier (UFMC) is a potential multi-carrier system for future cellular networks. UFMC provides low latency, frequency offset robustness, and reduced out-of-band (OOB) emission that results in better spectral efficiency. However, UFMC suffers from the problem of high peak-to-average power ratio (PAPR), which might impact the function of high power amplifiers causing a nonlinear distortion. We propose a comparative probabilistic PAPR reduction technique, called the decomposed selective mapping approach, to alleviate PAPR in UFMC systems. The concept of this proposal depends on decomposing the complex symbol into real and imaginary parts, and then converting each part to a number of different phase vectors prior to the inverse fast Fourier transform (IFFT) operation. The IFFT copy, which introduces the lowest PAPR, is considered for transmission. Results obtained using theoretical analysis and simulations show that the proposed approach can significantly enhance the performance of the UFMC system in terms of PAPR reduction. Besides, it maintains the OOB emission with candidate bit error rate and error vector magnitude performances.

Implementation of 64-Bits Radix - 8 IFFT for Computation Speed by IDIF using Verilog

Always technical designers choice includes algorithms, flowcharts, programming etc and the end users requires given input and application output. Based upon this view this paper focus on the advancement of Inverse Fast Fourier Transform(IFFT) by doing design and observing the performance analysis of 64 point IFFT, using Radix-8 algorithm. The algorithm is developed by Inverse Decimation In Frequency(IDIF) of IFFT, using Verilog as design entity and synthesis are performed in Xilinx. In this architecture the numbers of stages are reduced to 75%.

Generalizing the inverse FFT off the unit circle

This paper describes the first algorithm for computing the inverse chirp z-transform (ICZT) in O(n log n) time. This matches the computational complexity of the chirp z-transform (CZT) algorithm that was discovered 50 years ago. Despite multiple previous attempts, an efficient ICZT algorithm remained elusive until now. Because the ICZT can be viewed as a generalization of the inverse fast Fourier transform (IFFT) off the unit circle in the complex plane, it has numerous practical applications in a wide variety of disciplines. This generalization enables exponentially growing or exponentially decaying frequency components, which cannot be done with the IFFT. The ICZT algorithm was derived using the properties of structured matrices and its numerical accuracy was evaluated using automated tests. A modification of the CZT algorithm, which improves its numerical stability for a subset of the parameter space, is also described and evaluated.

Two- and Three-Dimensional Fast Intrawall Imaging with Microwave Tomographic Algorithm

A fast and efficient microwave tomographic algorithm is proposed for 2-D and 3-D real-time intrawall imaging. The exploding reflection model is utilized to simplify the imaging formulation, and the half-space Green’s function is expanded in the spectral domain to facilitate the easy implementation of the imaging algorithm with the fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT). The linearization of the inversion scheme and employment of FFT/IFFT in the imaging formula make the algorithm suitable for various applications pertaining to the inspection of a large probed region and allow real-time processing. Representative numerical and experimental results are presented to show the effectiveness and efficiency of the proposed algorithm for real-time intrawall characterization.

OFDM: A Mathematical Review

Mathematical review of the Orthogonal Frequency Division Multiplexing is demonstrated in terms of Inter symbol interference, Multi carrier modulated system and cyclic prefix. Modeling of the mathematical equation of the Orthogonal Frequency Division Multiplexing, Inverse fast Fourier transform and fast Fourier transform is explained with the suitable example using MATLAB. Bit error rate performance of OFDM is also presented with the help of statistical computation.

Design and Synthesis of Visible Light Communication Transceiver on FPGA

Pre-print :In this paper, we designed and synthesized a Visible Light Communication (VLC) system with Inverse / Fast Fourier Transform (I/FFT) as a frequency multiplexing method using an FPGA. The system will map the data sent using a constellation mapper, which uses 4-Quadrature Amplitude Modulation. After mapped, the data is frequency multiplexed using an IFFT block and converted into its analog form before being transmitted through an LED amplifier circuit and a Cree XML2 LED. Next, the signal is received by Ba PV10 photodiode on the receiver module and a transimpedance amplifier. Once processed by the VLC receiver, the conversion of analog signals to digital is done before demultiplex the signal using FFT. Then we demapped the signal from back to the original data using a 4QAM demapper. The transceiver system was implemented on Altera De-0 Nano board with an Altera Cyclone 4E FPGA. The VLC transmitter module, VLC receiver, and ADC / DAC were implemented on a breadboard. The communication system works with a bit rate of 302 kbps. The Analog and digital subsystems are capable of supporting the bitrate, and supplying the LED lamp with a power of 0.10125 W. The system was then tested at different distances from 25 cm to 60 cm. At 25 and 30 cm, there is no error on the characters received. But at 35 cm there was a character error rate of 0.042%. This error continued to increase as the distance was added so that it reached 7.42% at a distance of 60 cm. This is normal since, at a distance of 25 and 30 cm, the signal received was still large so that the SNR was still good. But at 35 cm onwards, the received signal started to distort and the SNR started to decrease.