ROBUST CHIRP PARAMETER ESTIMATION FOR HANN WINDOWED SIGNALS

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A chirp is a signal in which the frequency increases ('up-ch...

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In several bushcricket species, individual males synchronise their chirps during acoustic interactions. Synchrony is imperfect with the chirps of one male leading or lagging the other by a few milliseconds. Imperfect synchrony is believed to have evolved in response to female preferences for leading chirps. We investigated the mechanism underlying synchrony in the bushcricket species Mecopoda 'Chirper' from Southern India using playback experiments and simulations of pairwise interactions. We also investigated whether intrinsic chirp period is ...

The sinusoidal model has been a fundamentally important signal representation for coding and analysis of audio. We present an enhancement to sinusoidal modeling in the form of a linear frequency chirp parameter estimator applicable to Hann-windowed quasi-sinusoidal signals. The estimator relies on models of the phase curvature and peak width of a given chirp signal?s FFT magnitude domain peak. We show that different models are applicable for smaller and larger values of the chirp parameter, derived respectively from Taylor series and Fresnel in...

Abstract We propose a new robust and accurate synchronization procedure using a training sequence composed of chirp signals. We use a new integer frequency estimation algorithm and propose a new combination of a known fractional frequency offset estimation algorithm and timing synchronization algorithm. The training sequence is composed of one up and two down chirp symbols, also known as Newman phases. The integer frequency offset estimation algorithm uses the effect of timing and frequency offsets on the matched filter outputs of the chirp si...

Abstract We propose a new robust and accurate synchronization procedure using a training sequence composed of chirp signals. We use a new integer frequency estimation algorithm and propose a new combination of a known fractional frequency offset estimation algorithm and timing synchronization algorithm. The training sequence is composed of one up and two down chirp symbols, also known as Newman phases. The integer frequency offset estimation algorithm uses the effect of timing and frequency offsets on the matched filter outputs of the chirp si...

Abstract In this study, we propose a new spread spectrum image watermarking algorithm that embeds linear chirps as watermark messages. The slopes of the chirp on the time-frequency (TF) plane represent watermark messages such that each slope corresponds to a different message. We extract the watermark message using a line detection algorithm based on the Hough-Radon transform (HRT). The HRT detects the directional elements that satisfy a parametric constraint in the image of a TF plane. The proposed method not only detects the presence of wate...

Abstract A high data-rate wideband chirp spread spectrum system for indoor communication is proposed. The use of chirp signals with the well known pulse compression technique makes the system extremely robust and therefore suitable for applications in an industrial environment. By using ?/4 DQPSK modulation, overlapping chirp signals, and optimized chirp signal design we get data rates up to 70 Mbps. There is no need for sophisticated digital signal processing due to the use of surface acoustic wave (SAW) filters for the generation and filteri...

Abstract A new robust image watermarking algorithm that embeds multiple watermark bits in the host image is proposed. Linear chirps are embedded as watermark messages, where the slopes of the chirp on the time-frequency (TF) plane represent watermark messages, such that each slope corresponds to a unique message. The Hough-Radon transform (HRT) is a widely used tool to detect directional elements that satisfy a parametric constraint in images. Since linear chirps are localised as a straight line in the TF plane, the HRT is used to detect the w...

Abstract The chirp scaling algorithm (CSA) is considered as an efficient SAR imaging algorithm. The existence of the range-uncompressed chirp is the necessary condition for CSA to be used. However, if the range chirp is large in the high squint angle case, there will be a strong coupling between the range chirp and azimuth frequency. This coupling will render the relationship between range curvature and Doppler frequency non-linear and hence make the CSA lose its precision in such a case. An analysis about this coupling effect and a compensati...

Abstract The chirp scaling algorithm (CSA) is considered as an efficient SAR imaging algorithm. The existence of the range-uncompressed chirp is the necessary condition for CSA to be used. However, if the range chirp is large in the high squint angle case, there will be a strong coupling between the range chirp and azimuth frequency. This coupling will render the relationship between range curvature and Doppler frequency non-linear and hence make the CSA lose its precision in such a case. An analysis about this coupling effect and a compensati...

Abstract The discrete Fourier transform (DFT) has found tremendous applications in almost all fields, mainly because it can be used to match the multiple frequencies of a stationary signal with multiple harmonics. In many applications, wideband and nonstationary signals, however, often occur. One of the typical examples of such signals is chirp-type signals that are usually encountered in radar signal processing, such as synthetic aperture radar (SAR) and inverse SAR imaging. Due to the motion of a target, the radar return signals are usually ...

Abstract The discrete Fourier transform (DFT) has found tremendous applications in almost all fields, mainly because it can be used to match the multiple frequencies of a stationary signal with multiple harmonics. In many applications, wideband and nonstationary signals, however, often occur. One of the typical examples of such signals is chirp-type signals that are usually encountered in radar signal processing, such as synthetic aperture radar (SAR) and inverse SAR imaging. Due to the motion of a target, the radar return signals are usually ...

Abstract It has been experimentally demonstrated that the chirp imposed on the pulses from an actively modelocked erbium fibre ring laser can be controlled by using a dual-drive variable-chirp modulator as a modelocker

Abstract We experimentally demonstrate that the chirp imposed on the pulses from an actively mode-locked erbium fiber ring laser can be controlled by using a dual-drive variable-chirp modulator as mode locker

Abstract Summary form only given, as follows. The time-frequency distribution (TFD) of a spread spectrum signal looks more like a noise, and the energy distribution occupies the full two-dimensional time-frequency (TF) plane. Any jammer or interference will be well localized in the TF plane. By treating the TF plane as an image, the interference patterns can be detected by using the image analysis technique of the Hough-Radon transform (HRT). Curves with mathematical equations can be easily detected by transforming the shapes into the Hough do...

Abstract The possibility of nearly chirp-free electroabsorption (EA) characteristics in intensity modulation at an operating wavelength of 1.55 �m is studied theoretically. The TE-polarized EA spectra, their Kramers�Kr�nig (K�K) transformed refractive index changes, and the chirp parameters derived under both small-signal and large-signal conditions are calculated including excitonic effect within the framework of the effective mass theory. We investigate on the basis of the simulated EA results how to keep chirp parameters always negative. Th...