Interception Algorithm of S-cubed Signal Model in Stealth Radar Equipment

AbstractRadar equipment of stealth platforms such as aircraft have adopted the newest modern technology to design the signal waveforms. One of the important and effective methods is the hybrid waveform called spread spectrum stretch (S-cubed) which combines linear frequency modulation (LFM) and discrete phase code. In order to investigate the function of enemy's stealth radar equipment, the interception algorithm of S-cubed is needed. In this paper, a novel detection and parameter estimation approach for the reconnaissance S-cubed radar signal is presented. First, the generalized time-frequency representation of Zhao, Atlas, and Marks (ZAM-GTFR) and Hough transforms (HT) are applied to detecting the signal, and then the initial frequency and modulation slope of LFM are estimated from the ZAM-GTFR. On the basis of LFM information, the reconstructing signal is generated. Finally, the code rate of discrete phase code is extracted from the negative peaks of the ZAM-GTFR. Simulation results show that the proposed algorithm has higher estimation accuracy when the signal to noise ratio (SNR) is above 3 dB

Optophone design: optical-to-auditory vision substitution for the blind

An optophone is a device that turns light into sound for the benefit of blind people. The present project is intended to produce a general-purpose optophone to be worn on the head about the house and in the street, to give the wearer a detailed description in sound of the'scene he is facing. The device will therefore consist'of an'electronic camera, some signal-processing electronics, earphones`, and a battery. The two major problems are the derivation of (a) the most suitable mapping from images to sounds, and (b) an algorithm to perform the mapping in real'time on existing electronic components. This thesis concerns problem (a). Chapter 2 goes into the general scene-to-sound mapping problem in some detail'and presents the work of earlier investigators. Chapter 3 1- discusses the design of tests to evaluate the performance of candidate mappings. A theoretical performance test (TPT) is derived. Chapter 4 applies the TPT to the most obvious mapping, the cartesian piano transform. Chapter 5 applies the TPT to a mapping based on the cosine transform. Chapter 6 attempts to derive a mapping by principal component analysis, using the inaccuracies of human sight and hearing and the statistical properties of real scenes and sounds. Chapter 7 presents a complete scheme, implemented in software, for representing digitised colour scenes by audible digitised stereo sound. Chapter 8 tries to decide how'many numbers are required to specify a steady spectrum with no noticeable degradation. Chapter 9 looks'at a scheme designed to produce more natural-sounding sounds related to more meaningful portions of the scene. This scheme maps windows in the scene to steady spectral patterns of short duration, the location of the window being conveyed by simulated free-field listening. Chapter 10 gives detailed recommendations as to further work

The use of late time response for stand off onbody concealed weapon detection

A new system for remote detection of onbody concealed weapons such as knives and handheld guns at standoff distances presented in this thesis. The system was designed, simulated, constructed and tested in the laboratory. The detection system uses an Ultrawide Band (UWB) antenna to bombard the target with a UWB electromagnetic pulse. This incident pulse induces electrical currents in the surface of an object such as a knife, which given appropriate conditions these currents generate an electromagnetic backscatter radiation. The radiated waves are detected using another UWB antenna to obtain the Late Time Response (LTR) signature of the detected object. The LTR signature was analysed using the Continuous Wavelet Transform (CWT) in order to assess the nature and the geometry of the object. The thesis presents the work which divided into two related areas. The first involved the design, simulation, fabrication, and testing of an Ultra-wide Band (UWB) antenna with operating bandwidth of 0.25 – 3.0 GHz and specific characteristics. Simulated and measured results show that the designed antenna achieves the design objectives which are, flat gain, a VSWR of around unity and distortion less transmitted narrow pulse. The operating bandwidth was chosen to cover the fundamental Complex Natural Resonance (CNR) modes of most firearms and to give a fine enough time resolution. The second area covered by this thesis presents a new approach for extract target signature based on the Continuous Wavelet Transform (CWT) applied to the scattering response of onbody concealed weapons. A series of experiments were conducted to test the operation of the detection system which involved onbody and offbody objects such as, knives, handheld guns, and a number of metallic wires of various dimensions. Practical and simulation results were in good agreement demonstrating the success of the approach of using the CWT in analyzing the LTR signature which is used for the first time in this work. Spectral response for every target could be seen as a distribution in which the energy level and life-time depended on the target material and geometry. The spectral density provides very powerful information concerning target unique signature