Pseudo-noise Signal Research Articles

Inverse Synthetic Aperture Radar Imaging of Space Targets Using Wideband Pseudo-Noise Signals with Low Peak-to-Average Power Ratio

With the number of new satellites increasing dramatically, comprehensive space surveillance is becoming increasingly important. Therefore, high-resolution inverse synthetic aperture radar (ISAR) imaging of satellites can provide an in-situ assessment of the satellites. This paper demonstrates that pseudo-noise signals can also be used for satellite imaging, in addition to classical linear frequency-modulated chirp signals. Pseudo-noise transmission signals offer the advantage of very low cross-correlation values. This, for instance, enables the possibility of a system with multiple channels transmitting instantaneously. Furthermore, it can significantly reduce signal interference with other systems operating in the same frequency spectrum, which is of particular interest for high-bandwidth, high-power systems such as satellite imaging radars. A new routine has been introduced to generate a wideband pseudo-noise signal with a peak-to-average power ratio (PAPR) similar to that of a chirp signal. This is essential for applications where the transmit signal power budget is sharply limited by the high-power amplifier. The paper presents both theoretical descriptions and analysis of the generated pseudo-noise signal as well as the results of an imaging measurement of a real space target using the introduced pseudo-noise signals.

차세대 GNSS를 위한 GIG 부호 기반 시간다중 이진부호심볼 변조기법

In this paper, we propose a time multiplexed binary coded symbol (TMBCS) modulation scheme based on Gray and inverse Gray (GIG) codes for the next generation global navigation satellite system (GNSS). A representative binary coded symbol (BCS) is a binary offset carrier (BOC). Compared to the existing binary phase shift keying (BPSK) modulation, which is a representative GNSS modulation scheme, BOC modulation has a high degree of freedom in terms of frequency band shape design and is less affected by multipaths because the correlation function is sharper at the correct code phase. However, since several sub-peaks occur in the correlation function of the BOC-modulated pseudo-noise signal, false locks can easily occur during code tracking. This disadvantage is called the ambiguity of the BOC modulated signal. Time multiplexed binary Walsh spreading (TMBWS) modulation, which is a TMBCS scheme that uses a Walsh code, is one method for reducing ambiguity and is a perfectly orthogonal code with a very good correlation among BCSs. However, Walsh codes can only be generated with a power of two length. In this paper, we propose a novel TMBCS modulation scheme using quasi-orthogonal GIG codes that can be generated with lengths that are multiples of 2. The proposed scheme maintains the same bandwidth and spectral separation coefficient compared to TMBWS when a symbol of length 8 is used. In addition, the proposed scheme has a higher degree of freedom in terms of band shape design compared to TMBWS modulation, because the length can be designed in multiples of 2 (such as 6, 10, or 12) and has high multipath immunity with unambiguity.

Primitive Polynomials for Iterative Recursive Soft Sequential Acquisition of Concatenated Sequences

An iterative initial sequence acquisition technique is proposed for the pseudo-noise signal derived from a pair of m -sequences used for generating the concatenated sequence, which relies on the soft-in-soft-out detection to improve the acquisition performance. This recursive soft sequential estimation technique has a linearly increasing complexity with the number of chips in the concatenated sequence. Receiving as few as S consecutive chips of a (2 S -1)-chip sequence is sufficient for the local concatenated-sequence generator of the receiver to synchronize. Hence, this initial synchronization technique is eminently suitable for long m -sequences and concatenated sequences. Another key result is the comparison of m -sequences and concatenated sequences regarding the acquisition time. It is also observed that low-order primitive polynomials (PPs) achieve better performances than higher-order polynomials for both the m -sequences and concatenated sequences. When considering PPs having a higher number of taps, the exploitation of concatenated sequences is capable of achieving in excess of 3-dB signal-to-noise ratio gains over m -sequences.

Method for pseudo-noise signal generation based on M-sequences with non-multiple recurring periods

Method for pseudo-noise signal generation based on M-sequences with non-multiple recurring periods

Robustness of pure white pseudonoise signal to temporal fluctuation in impulse response measurement

Robustness of pure white pseudonoise signal to temporal fluctuation in impulse response measurement

Fading statistics variation and optimum Mary frequency shift keying system design in sea surface fluctuation

The underwater acoustic channel can be expressed as a frequency selective fading channel due to multipath, sea surface roughness, and propagation medium change with time and space. Therefore the fading statistics varies with time, space, and frequency. Inherent factor of this fading change is related to a frequency dependent constructive or destructive interference change with time, space, and frequency. The magnitude of interference depends on closely on sea surface roughness. In this study, channel fading statistics are analyzed with delay spread and Doppler spread using pseudo noise (PN) signals. Based on this channel fading statistics, a low data rate M-ary frequency shift keying (MFSK) system of 1kbit/s, is designed for a command/control of navigation or an equipment status monitoring system. The forward error correcting code of convolution code is also applied. Experimental work is conducted in shallow water and it is found that the design parameters of MFSK system can be optimized using the measured fading statistics deduced from PN signal.

Research on Performance Analysis of Digital Baseband Signal Transmission

Nowadays, in order to improve the quality of signal transmission and reduce the signal attenuation and noise interference, the transmission digital baseband signal modulation become mainstream in today's signal transmission. For the digital baseband signal transmission performance of research helps us to understand the process of digital signal transmission. Firstly, using shift registers to produce m sequence, used to simulate the data signal and the pseudo random noise signal. Then, to design a low pass filter, used to simulate the channel. Data signal transmission in the channel was carried with additive random noise interference, we can measure signal interference by observing eye pattern at the receiving terminal. If to Manchester encoding of data signal, the receiver decoding output data signal can be extracted using the synchronous clock circuit to get the clock signal to synchronize, and display the eye pattern, which is used to evaluate the performance of the transmission system. And we put forward the optimization scheme of the digital baseband signal transmission performance through the research.

Disruption of synchronization in the tracking system with delayed pseudo noise signal

Disruption of synchronization in the tracking system with delayed pseudo noise signal

A Correlation-Based Watermarking Technique of 3-D Meshes via Cyclic Signal Processing

This paper describes a blind watermarking scheme through cyclic signal processing. Due to various rapid networks, there is a growing demand of copyright protection for multimedia data. As efficient watermarking of images, there exist two major approaches: a quantization-based method and a correlation-based method. In this paper, we proposes a correlation-based watermarking technique of three-dimensional (3-D) polygonal models using the fast Fourier transforms (FFTs). For generating a watermark with desirable properties, similar to a pseudonoise signal, an impulse signal on a two-dimensional (2-D) space is spread through the FFT, the multiplication of a complex sinusoid signal, and the inverse FFT. This watermark, i.e., spread impulse signal, in a transform domain is converted to a spatial domain by an inverse wavelet transform, and embedded into 3-D data aligned by the principle component analysis (PCA). In the detection procedure, after realigning the watermarked mesh model through the PCA, we map the 3-D data on the 2-D space via block segmentation and averaging operation. The 2-D data are processed by the inverse system, i.e., the FFT, the division of the complex sinusoid signal, and the inverse FFT. From the resulting 2-D signal, we detect the position of the maximum value as a signature. For 3-D bunny models, detection rates and information capacity are shown to evaluate the performance of the proposed method.

Design of a Covert RFID Tag Network for Target Discovery and Target Information Routing

Radio frequency identification (RFID) tags are small electronic devices working in the radio frequency range. They use wireless radio communications to automatically identify objects or people without the need for line-of-sight or contact, and are widely used in inventory tracking, object location, environmental monitoring. This paper presents a design of a covert RFID tag network for target discovery and target information routing. In the design, a static or very slowly moving target in the field of RFID tags transmits a distinct pseudo-noise signal, and the RFID tags in the network collect the target information and route it to the command center. A map of each RFID tag’s location is saved at command center, which can determine where a RFID tag is located based on each RFID tag’s ID. We propose the target information collection method with target association and clustering, and we also propose the information routing algorithm within the RFID tag network. The design and operation of the proposed algorithms are illustrated through examples. Simulation results demonstrate the effectiveness of the design.

Comments on "OFDM Transmission for Time-Based Range Estimation"

The letter by Wang and Fattouche makes the claim that the Cramer-Rao lower bound (CRLB) for range estimation using orthogonal frequency division multiplexing (OFDM) signals is 4.8 dB lower than that of pseudo-noise (PN) signals. However, this is not the case. The sole reason for the 4.8 dB gain in the said letter is due to the fact that the authors implicitly used an uncommon pulse shaping filter in the digital-to-analog conversion process for the PN signal.

Results of operation of detection system with application of Golay’s codes

There represented results of operation of algorithm of reduction of side pips of inter-correlation function of complex pseudo-noise signal, which is shaped by phase shift keying with Golay’s code law, whose development principle and detector optimal filter are presented. It is carried out a comparison of detection results with application of classical and proposed processing circuits.

Golay’s codes application features in radiolocation

It is proposed a method of reduce side surges of cross-correlation function of complex pseudonoise signal, that shapes by phase-shift keying according to Golay’s code law. Structural chart of correlation section of given signal detection is represented. It is compared cross-correlation functions for considered signal type and signal shaped by phase-shift keying according to the law of maximal period sequence (M-sequence).

Identification of Scattering Objects in Microcell Urban Mobile Propagation Channel

A series of measurements in two streets in a dense urban area were accomplished. The measurement scenario was small microcell line-of-sight (LoS) with low antenna height at both link ends where dipole sleeve transmitter (Tx) antenna, directive receiver (Rx) antenna, wideband pseudo-noise (PN) signal and correlator were employed. We analyze the data obtained from the measurements by careful investigation of the single-bounce scattering power distribution conforming to precise maps of the environments including all present objects. We try to identify the single-bounce scatterers for the cluster received waves appearing in the single-bounce scattering power distribution. A number of objects were identified by this method as single-bounce scatterers within the spatial resolution bins. The identified objects are signboards, traffic signs, etc. and we conclude that any metallic object visible to both Tx and Rx with dimensions in orders of tens of wavelengths can be a significant source of scattering in small cell scenarios with low antenna heights. The contribution of the scattering from these identified objects to the received power compared to other micromechanisms is evaluated. Results show that the scattering from these objects can be comparable to the wall reflections

Measurement of the sensitivity and directivity pattern of hydroacoustic measuring modules in artificial tanks

A method of measuring the sensitivity and directivity pattern of hydroacoustic measuring modules of considerable dimensions in artificial tanks is considered. The method is based on the use of a pseudonoise signal. The results of the mathematical modeling and practical application of the method are presented.

Illumination of the shadow zone in a two-channel oceanic waveguide with a fine structure of sound speed inhomogeneities

The experimental data on the sound field structure, which were obtained by emitting a continuous pseudonoise signal (a midfrequency of 3.2 kHz) in a two-channel oceanic waveguide, are compared with the calculations performed by the wave program with allowance for the fine structure of the sound speed inhomogeneities. A considerable increase in the intensity of the sound field with a definite angular spectrum is observed in the upper channel in the first shadow zone, and, in the experiment, the increase begins nearer to the sound source than predicted by the wave and ray calculations for a smooth sound speed profile. These features of the field structure are explained by the illumination of the shadow zone by the regular scattering of signals from highly anisotropic fine-structure inhomogeneities of the sound speed profile, which are clearly pronounced in the region of the given oceanic experiment.

Characteristics of sound signals on a quasi-stationary track between the Josephine and Ampere Seamounts

Experimental data are presented on the measurement of the cross-correlation coefficients and the differences in the arrival times (temporal spectra) of acoustic signals transmitted through a 210-km-long quasi-stationary track in the Atlantic Ocean. At the summit of the Josephine Seamount, a continuous pseudonoise signal was emitted in the one-third-octave band with a mean frequency of 630 Hz. The signal was received at the Ampere Seamount by a 40-m flexible vertical array with a directivity pattern in the form of a static fan of 32 lobes. The width of each lobe was ∼3°. At a signal-to-noise ratio of about 3 dB and with an incomplete resolution of multipath signals by the array, the correlation coefficients reached a value of 0.48. The rms fluctuations of the differences in the arrival times varied from 1.8 to 3.1 ms depending on the signal arrival angles. The factors responsible for the low correlation coefficients and the relatively high fluctuations of the arrival time differences are discussed. Apparently, one of the factors is the presence of short-period internal waves.

PN Acquisition for DS/SS Using a Preloop Parallel Binary Search Phase Estimator and a Closed-Loop Selective Search Subsystem

An acquisition method of long pseudo-noise (PN) sequences in direct-sequence spread spectrum (DS/SS) systems is presented. The concurrent cross correlation of locally generated auxiliary signals with the incoming PN sequence produces binary search estimates leading to an initial approximation of the input signal's PN offset. The PN receiver then uses a closed-loop subsystem to determine the true offset of the incoming PN signal. New phase estimates are generated from successive corrections of likely errors in the binary search. The acquisition scheme's average acquisition time and its variance are analytically determined. Simulation results show that the proposed acquisition scheme is faster than the conventional serial receiver. A hybrid serial/parallel PN acquisition receiver is used for comparing the acquisition performance given similar hardware complexity. The hybrid receiver used the same number of parallel correlators as used in the proposed receiver's input phase estimator. Simulation results show that the proposed system provides an improved performance under normal operating conditions.

Generating calibration signals for an adaptive beamformer

A beamformer is calibrated for use as an acoustic echo canceler in a hands-free communications environment having a loudspeaker and a plurality of microphones. To perform the calibration, a number of adaptive filters are provided in correspondence with each of the microphones, and each of the adaptive filters is trained to model echo properties of the environment as experienced by the corresponding one of the microphones. A target source is activated, thereby generating an acoustic signal that is received by the microphones. The trained adaptive filters are then used to generate jammer signals by, for example, having each one filter a pseudo noise signal. Respective ones of the jammer signals are then combined with corresponding signals supplied by the microphones, thereby generating combination signals. The combination signals are then used to adapt the beamformer to cancel the jammer signals. In another aspect of the invention, the adaptive filters may be utilized during normal operation by having them perform an echo cancellation operation on each of the signals that is to be supplied to the calibrated beamformer.

Long-term stability of the sound field structure in the central part of the eastern Atlantic

Results of studying the angular and energy structures of the sound field formed in the first convergence zone as a result of the transmission of a continuous pseudonoise signal in the frequency range 0.8–1.5 kHz are presented for the case of the corresponding points lying in the upper ocean layer at depths between 150 and 500 m. The sound field characteristics were studied with the use of omnidirectional and narrow-beam (∼2°) reception in the vertical plane. The variability of the basic experimental parameters of the field structure is analyzed using the data of three experiments carried out in the eastern part of the Atlantic Ocean, near the Canary Islands, over a period of 11 years. The experimental results are compared with ray calculations. It is shown that, in the region under investigation, the experimental characteristics of the field structure are relatively stable and the extent to which they agree with the calculated parameters is also stable. In addition, some data are presented to illustrate the effect of a small lens of Mediterranean water, which manifests itself in sound velocity variations at the channel axis, on certain field characteristics.