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Waveform Aliasing in Satellite Radar Altimetry

IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 2015年第4期53卷 1671-1682页

作者： Smith, Walter H. F. Scharroo, Remko Natl Ocean & Atmospher Adm Lab Satellite Altimetry College Pk MD 20740 USA

The full deramp pulse compression scheme employed by satellite radar altimeters digitizes each radar echo at a sampling rate matched to the chirp bandwidth. Echo power is undersampled by a factor of 2 when the power samples are simply obtained by squaring the magnitude of the echo samples, without first resampling, as is done in all altimeters to date. This results in inadequate sampling of the leading edge of the waveform if the significant wave height (SWH) is low. For a typical Ku-band altimeter with a chirp bandwidth of 320 MHz, simple squaring should be inadequate over ocean surfaces with SWH less than 2 m, that is, half of the ocean. Simply zero-padding the digital samples prior to range Fourier transform alleviates the problem introduced by magnitude squaring. Data from the CryoSat altimeter are used to demonstrate this remedy, and it is found that this reduces the variance in estimated range by 10% and in SWH by 20%. These improvements are confined to a range of SWH values between 1 and 4 m. Zero-padding also seems to have some small impact on values estimated over very flat surfaces (SWH << 1 m), although theory suggests that better resolution of such surfaces would require a bandwidth exceeding 320 MHz. The 500-MHz bandwidth of the Ka-band altimeter on the Satellite with ARGOS and AltiKa mission should encounter these difficulties at smaller SWH values. Onboard range tracking and automatic gain control loops in future altimeters might be improved if zero-padding were employed during onboard waveform processing.

关键词： Geophysical sea measurements ocean surface pulse compression methods pulse measurements pulse modulation radar altimetry radar remote sensing signal sampling spaceborne radar synthetic aperture radar (SAR)

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Walsh-Hadamard Sequences for Binary Encoding of Radar Signals 5

Walsh-Hadamard Sequences for Binary Encoding of Radar Signal...

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International Conference on Military Technologies

作者： Matousek, Zdenek Babjak, Marian Ochodnicky, Jan Armed Forces Acad MR Stefanik Dept Elect Liptovsky Mikulas Slovakia

ISBN: (纸本)9788072319763

In this paper performance of Walsh-Hadamard sequences (WHS) for binary encoding of radar signals is described. It is shown that between WHS with length 8, 16 and 32 it is possible to find a set of orthogonal sequences with good properties. Probability of correct range detection of selected WHS in presence of active noise jamming is described and it is compared with cases when Barker code is used for binary encoding of radar signals and when widely used linear frequency modulation inside pulse duration is used to spread spectrum of radar signals.

关键词： pulse compression methods Radar signal processing Spread spectrum radar.

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Reconfigurable digital radar receiver implemented in FPGA using Under-sampling, Direct IQ generation, Multi-rate filter and pulse compression

Reconfigurable digital radar receiver implemented in FPGA us...

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IEEE International Microwave and RF Conference (IMaRC)

作者： Rathore, Ravinder Pratap Singh DRDO Elect & Radar Dev Estab LRDE Bengaluru Karnataka India

ISBN: (纸本)9781479963171

Reconfigurable digital receiver of radar system in FPGA required less computation and FPGA resources. Digital techniques like fast sampling ADC, Direct IQ generation, multi-rate filter, pulse compression are used in this design for improving the performance and reliability of receiver. Digital receiver receives, enhances and converts analog RF return energy into digital signals for further detection processing of target. Xilinx FPGA Virtex 5 is used in this design to give more flexibility in changing receiver parameter like different waveforms, bandwidths, sampling rates etc. Matlab tool develops and simulates the design whereas Xilinx system generator generates the VHDL code. All algorithms in FPGA are implemented in fixed point. In this paper, receiver design can be reconfigured with different bandwidth, sampling rate in FPGA by changing DDC FIR filter and pulse compression coefficients for multi-channel receiver application.

关键词： Digital filters field programmable gate arrays pulse compression methods radar applications receivers signal sampling

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Optimal Design of an N-Stage Nonlinear Transmission Line Based on Genetic Algorithm and LTspice

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IEEE TRANSACTIONS ON PLASMA SCIENCE 2013年第8期41卷 2408-2414页

作者： Baginski, Michael E. Lu, Hai Caudle, Byron T. Kirkici, Huyla Auburn Univ Dept Elect & Comp Engn Auburn AL 36849 USA

In this paper, we discuss a theoretical optimal design of a nonlinear transmission line using a genetic algorithm (GA) to achieve peak pulse power. The technique is based on an integrated optimization approach that uses a GA coded in MATLAB and the circuit simulation program LTspice. A bidirectional interface is created that allowed information to be rapidly transferred between the circuit simulator and GA with real-time monitoring of the entire design process, including peak power and elemental values. The designed process shows a peak voltage enhancement of 318% while eliminating the tedious trial and error process usually required. It is important to note that this result is achieved using only six L-C segments and a much greater voltage increase is likely as the number of segments is increased.

关键词： Nonlinear circuits pulse compression methods pulse power systems

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An Efficient pulse compression Method of Chirp-Coded Excitation in Medical Ultrasound Imaging

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IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL 2013年第10期60卷 2225-2229页

作者： Yoon, Changhan Lee, Wooyoul Chang, Jin Ho Song, Tai-Kyong Yoo, Yangmo Sogang Univ Dept Elect Engn Seoul South Korea Sogang Univ Interdisciplinary Program Integrated Biotechnol Seoul South Korea Sogang Univ Sogang Inst Adv Technol Seoul South Korea

Coded excitation can improve the SNR in medical ultrasound imaging. In coded excitation, pulse compression is applied to compress the elongated coded signals into a short pulse, which typically requires high computational complexity, i.e., a compression filter with a few hundred coefficients. In this paper, we propose an efficient pulse compression method of chirp-coded excitation, in which the pulse compression is conducted with complex baseband data after downsampling, to lower the computational complexity. In the proposed method, although compression is conducted with the complex data, the L-fold downsampling is applied for reducing both data rates and the number of compression filter coefficients;thus, total computational complexity is reduced to the order of 1/L-2. The proposed method was evaluated with simulation and phantom experiments. From the simulation and experiment results, the proposed pulse compression method produced similar axial resolution compared with the conventional pulse compression method with negligible errors, i.e., >36 dB in signal-to-error ratio (SER). These results indicate that the proposed method can maintain the performance of pulse compression of chirp-coded excitation while substantially reducing computational complexity.

关键词： Baseband Chirp Image coding Imaging pulse compression methods Radio frequency Ultrasonic imaging

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Chirped Optical pulse compression Using a Silicon Channel Waveguide

Chirped Optical Pulse Compression Using a Silicon Channel Wa...

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Asia Communications and Photonics Conference (ACP)

作者： Cao, Lizhong Gao, Shiming Zhejiang Univ Ctr Opt & Electromagnet Res Zhejiang Prov Key Lab Sensing Technol State Key Lab Modern Opt Instrumentat Hangzhou 3I0058 Zhejiang Peoples R China

An integrated pulse compression method is proposed for chirped optical pulses based on silicon channel waveguides. A compression factor of about 0.05 is obtained by optimizing the waveguide dimensions.

ISBN: (纸本)9781467362740

关键词： Chirped pulse compression Vital Signs channel waveguide Chirp modulation Optical pulse compression pulse compression methods Compressibility factors compression pulse compression Optical pulses pulses Silicon

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Super-resolution pulse compression techniques for radar subsurface imaging

Super-resolution pulse compression techniques for radar subs...

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European Conference on Antennas and Propagation, EuCAP

作者： Hui Zhang Dirk Plettemeier Chair for High Frequency Engineering Communication Laboratory Dresden University of Technology Dresden Germany

In this paper the super resolution pulse compression technique is proposed for radar subsurface imaging. Radar signals transmitted by antenna system are reflected by the terrain surface and subsurface of the radar illumination area. The resolution of radar surface and subsurface imaging using normal pulse compression algorithms is limited by the bandwidth of the transmitted signal, and depends on the sharpness of the signal's auto correlation function. For obtaining high resolution radar surface and subsurface imaging with limited data, the super resolution pulse compression method is implemented in this paper. The results of simulation and measurement by using this method can support the proposal.

关键词： Signal resolution Radar imaging pulse compression methods Reflection Noise Image resolution

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Optimized Correlator for LS Codes-Based CDMA Systems

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IEEE COMMUNICATIONS LETTERS 2011年第2期15卷 223-225页

作者： Carmen Perez, Ma Urena, Jesus Hernandez, Alvaro De Marziani, Carlos Garcia, Jesus Jimenez, Ana Univ Alcala Escuela Politecn Dept Elect Madrid 28805 Spain Natl Univ Patagonia San Juan Bosco Argentina Dept Elect Engn RA-9000 Comodoro Rivadavia Chubut Argentina

Loosely Synchronized codes, which have gained considerable interest in CDMA-based wireless communications and sensory systems, can be constructed from a set of mutually orthogonal complementary sets of sequences. In this paper a new architecture is provided for the correlation of such codes. It demands less memory and number of operations than previous ones based on efficient correlators for complementary set of sequences, and can be easily implemented in programmable devices due to its regular structure.

关键词： Code division multi-access correlators pulse compression methods sequences

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Recursive algorithm to directly obtain the sum of correlations in a CSS

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SIGNAL PROCESSING 2011年第5期91卷 1343-1346页

作者： De Marziani, Carlos Urena, Jesus Hernandez, Alvaro Jesus Garcia, Juan Alvarez, Fernando J. Jimenez, Ana Carmen Perez, Ma Natl Univ Patagonia San Juan Bosco Dept Elect Engn RA-9005 Comodoro Rivadavia Chubut Argentina Consejo Nacl Invest Cient & Tecn Natl Council Sci & Tech Res Consejo Nacl Invest Cient & Tecn RA-1033 Buenos Aires DF Argentina Univ Alcala Dept Elect Escuela Politecn Madrid 28871 Spain Univ Extremadura Dept Elect Engn Elect & Automat Fac Ciencias E-06071 Badajoz Spain

This paper presents a new recursive algorithm to directly obtain the sum of the autocorrelation functions of the M sequences belonging to a Complementary Set of Sequences (M-CSS). The proposed algorithm allows a digital filter with only one stage to be obtained, what significantly reduces the total number of memory requirements, multiplications and additions to be performed in comparison with the use of M correlators, even when these correlators could have an efficient implementation. The use of this algorithm can be of great relevancy since there is an increasing interest in the use of CSS (or derived sequences such as Loosely Synchronized LS-sequences or Zero Correlation Zone ZCZ-sequences) in the field of communications and sensor systems. (C) 2010 Elsevier B.V. All rights reserved.

关键词： Code division multiple access Complementary Set of Sequences Filter banks Correlators pulse compression methods

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Performance Analysis of Noncoherent pulse compression Technique

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IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC SYSTEMS 2011年第4期47卷 2986-2990页

作者： Kayani, Jahangir K. Natl Univ Sci & Technol PAF Acad Coll Aeronaut Engn Risalpur Pakistan

Noncoherent pulse compression (NCPC) is a recently investigated variant of the classical (coherent) coded pulse compression technique [1-5]. The performance of NCPC under various signal-to-noise ratio (SNR) conditions is investigated and compared with coherent pulse compression (CPC). Various performance measurement approaches are used to quantify NCPC performance. All of them indicate very similar performance trends. It was found that, as the SNR of received signal decreases, the advantage of pulse compression in terms of improved SNR, gets diminished. It is therefore argued that NCPC is not well suited for low input SNR conditions, and for applications requiring large pulse compression gain.

关键词： Detectors Finite element methods Finite impulse response filter pulse compression methods Receivers Signal to noise ratio

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