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Passive radar networks offer several advantages compared to standard single radar. For instance a target is illuminated from different aspect angles and this leads to an increase of the detection performance and higher position estimation accuracy. Beside these both improvements the network is able to cope with an increased number of targets and the range/Doppler resolution is enhanced. As the system...
This paper focusses on the urban multipath channel reduction problematic for Global Navigation Satellite Systems (GNSS) receiver performance assessment. First, multipath aggregation methods are compared to parametric methods through channel delay and Doppler characteristics preservation criteria. Then, the impact of these criteria on the GNSS receiver's positioning computation is quantified, in order...
Uncorrelated samples of GPS carrier phase can be measured at a high rate in a tracking loop or via open-loop tracking. The high-rate carrier phase estimates from both approaches are expected to be equivalent to each other. However, the practical implementation of the tracking loop could cause a small difference in the measurement, which may become substantial when there is residual or transient error...
The detection of a desired weak GPS signal in the presence of other strong GPS signals is often problematic because the strong signal is not adequately attenuated by the receiver processing. The situation becomes worse in the case where multiple strong signals compete with the desired weak signal. This is a further complexity of the near-far problem, since the presence of strong signals that are not...
The article presents the analysis, model development and experimental verification of the specific for polarimetric radar with dual orthogonal LFM CW signals processing effect of the presence of range-dependent residual video phases with polarization-dependent sign in measurement channels. This artifact disturb the measurement process and has to be efficiently mitigated.
The article deals with description of spatial motion of the experimental radio-communications satellite Alphasat. The used Cartesian coordinates of the Alphasat satellite (given one week in advance in the OEM files of 5 minute resolution) are described. The coordinates conversion to the elevation and azimuth from the perspective of the receiver in Prague is added and described. This satellite motion...
Satellite navigation is now widely used in a land, sea, and air transport. It is easy to forecast the negative effects related to the lack of a signal of the Global Navigation Satellite System (GNSS), especially in the aviation and maritime traffic. In 20th century they were allayed the terrestrial navigation systems, e.g. Decca, Omega, Loran-C. Recently, only eLoran is used, as a backup system for...
Measurement results show that the motion direction of objects has a significant effect on the deformation of the autocorrelation function (ACF) and the power spectrum density (PSD) of the received signals. However, this fact is not included in the analysis of these characteristics previously presented in the literature. In this paper, ACF and PSD are presented as a function of the receiver (Rx) /...
In this paper, we propose a recursive least square (RLS) adaptive filter for sparse identification of underwater acoustic (UWA) channels. The adaptive filter is based on sliding window, diagonal loading, and dichotomous coordinate descent iterations. The adaptive algorithm possesses a complexity that is only linear in the filter length. The adaptive filter is used for channel estimation in an UWA...
In this paper, research was carried out to analyze the channel environment in the real sea using data measured in the shallow water of West sea of South Korea. By diversifying the distance between transmitter and receiver, we estimated RMS delay spread and maximum excess delay spread in various channel environments to draw coherence bandwidth and then estimated Doppler spread of received signal to...
This paper proposes a communication structure which can operate reliably over doubly spread and multiple access acoustic channels. The doubly spread channel estimation is embedded into the general-sidelobe-canceller (GSC). From the combination we derive a novel spatial-temporal-frequency (STF) GSC. Such communication system can be operated in situation where multiple underwater platforms with different...
Tracking and Data Relay Satellite System (TDRSS) Demand Access System (DAS) sustainment is aimed at modernizing the existing DAS using low-cost hardware components as well as a more robust monitor and control architecture. A key part of the system is the DAS receiver, which supports the Pseudo Noise (PN) modulation waveforms of the TDRSS. The receiver in the current DAS system is a custom design that...
In this paper, we propose a broadband Doppler estimation and compensation receiver, which combines a bi-directional decision feedback equalizer (DFE). Compared with the existing receivers, the proposed closed loop Doppler estimation and compensation receiver combined with a bi-directional DFE can not only estimate and compensate the broadband Doppler symbol-by-symbol, but also reduce the error propagation...
Linear Frequency Modulation (LFM) pulse compression search radars maintains high range resolution along with high average power. Moreover, it has high processing gain which results in a high immunity against conventional noise jamming. In this paper, convolution noise jamming is introduced as a form of smart noise jamming against LFM-PC search radars. A typical LFM-PC search radar model is introduced...
Interference alignment like techniques are promising in multiuser networks as they yield a high sum capacity and allow multiple users to communicate concurrently. As alignment of interference requires tight coupling to estimates of the channel, time variations in the channel lead to loss of capacity since estimates take time to make and communicate. Thus, the length of the data and training phase...
This paper proposes a cascaded filter-based model that efficiently generates correlated complex Gaussian variates for mobile-to-mobile double-Rayleigh scattering multipath fading channels. We apply an infinite impulse response (IIR) filter followed by a variable interpolator, to accommodate different Doppler rates, can directly be applied to the design of so-called “double-Rayleigh” mobile-to-mobile...
This article discusses the detection problem of a passive multistatic radar system with a non-cooperative illuminator of opportunity in the presence of compensation errors. Two detectors are used to address this detection problem according to whether the noise powers in the receivers are equal or not. Both of them have a constant false alarm rate with respect to the noise power. Numerical examples...
This paper introduces our recently upgraded Ka-band two-receiving-channel radar system, which adopts stepped-frequency chirp signal (SFCS) and the signal spans 2GHz bandwidth. The upgrading include the two-channel dechirping-on-receiving receiver and the data sampling and recording subsystem where high-speed optical transmission technique is used. We use two arbitrary waveform generators in the system,...
Intermittent tracking or cyclic tracking is a common method used in modern Global Navigation Satellite System (GNSS) receivers to conserve power. It is critical for receivers in battery-operated devices like wearables, smartphones and handheld devices. These devices are often used in degraded or weak signal environments such as indoors. This paper discusses the challenges for intermittent signal tracking...
GNSS carrier phase measurement capability is one of the most important features for high performance/accuracy receivers. However significant signal attenuation due to blockage and multipath as experienced indoors for example, degrades carrier phase quality in standard carrier phase tracking loops using PLL or KF-PLL. Under such conditions, the receiver may not be able to generate reliable carrier...
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