Gabriele Pavan

Computer simulation of weather radar signals

Abstract Computer simulation is largely used in radar signal analysis. The present work treats the simulation of precipitation echoes in weather radar applications. Such simulated signals are very useful when different processing techniques have to be tested and compared. Modern weather radar has both Doppler and polarimetric capabilities; from the simulation point of view, this implies the generation of two pseudorandom sequences with an assigned autocorrelation function (ACF) and an assigned cross correlation. A new generator of pseudorandom sequences is proposed and compared with an old one. The results show that the novel technique represents correctly both the ACF and the cross correlation, even when a limited number of samples (e.g. 8 or 16 typical of Air Traffic Control applications) is considered. Finally, the computer time needed to generate one sequence is evaluated and compared for both generators.

Generation of pseudo-random sequences for noise radar applications

Noise Radar Technology (NRT) is nowadays a promising tool in radar systems. It is based on the transmission of waveforms composed of many noisy samples, which behave as LPI (Low Probability of Intercept) and antispoofing signals. Each noisy sequence is theoretically uncorrelated with the others. In the paper we propose a scheme to generate a “tailored” pseudo-random sequences (limited in amplitude). It will be followed by an analysis of the main performances in terms of the Peak Side Lobe Ratio (PSLR) of the autocorrelation function, cross-correlation analysis to evaluate the orthogonality, bandwidth and energy efficiency.

Waveforms design for modern and MIMO radar

One of the main focus of the research in modern radar systems, as MIMO (Multiple Input Multiple Output) radar and multifunction/multistatic radar, is the waveforms design and optimization in order to get a low degradation in the main lobe (low Signal to Noise Ratio loss), a low Peak Side-Lobe Ratio (PSLR) and good orthogonality properties. In MIMO applications typically M different waveforms, or codes, are required, where M is the number of the transmit elements. In reception the orthogonal property of the M transmitted waveforms permits their separation. Orthogonality may be imposed in time domain, in frequency domain or in signals space. In most radar applications, obtaining the orthogonality in the signals domain is the best choice. Good candidates to design deterministic signals that satisfy the orthogonality requirements are the well-known “up” and “down” chirp (Linear-FM and Non-LFM), the Costas codes, the Alltop sequences and the OFDM signals. Another important class of orthogonal signals are the random signals such as the noise waveforms. In this paper we present the main characteristics of these signals and their comparison through a characterization, including an analysis of the auto and cross correlation functions, and of the spectral properties, with recommendations for practical use.

Mutual Interference Problems Related to the Evolution of Marine Radars

The increasing environmental consciousness and the better attention paid to the primary resources (especially oil and raw materials) is one of the main drivers of the increase in vessel traffic. In addition the sea shipping is characterized by a good delivery rate and affordable operating costs in comparison with other transport means, i.e. by road, rail or air. For this reasons, the continuous increase of vessel traffic requires a high degree of control and an adequate assistance to the navigation, in order to ensure safety, reduction of risks for the environment, as well as an efficient navigation. The paper describes the evolution of the marine radar systems pointing out the advantages and the potential drawbacks due to the implementation of solid state technology in new generation of marine radars.

Noise radar technology: Pseudorandom waveforms and their information rate

The well-known LPI (Low Probability of Intercept) and antispoofing capabilities of some radar waveforms as well some other desirable feature such as a low sidelobes level of their autocorrelation function can be enhanced by “tailored” pseudo-random sequences, whose phase is made up by a deterministic part plus a variable random term. With such an approach it is possible to design a virtually unlimited number of noisy waveforms with good auto-correlation properties (PSLR, i.e. Peak to Side Lobe Ratio) and, for MIMO applications, good orthogonality between them. In this paper the LPI characteristic are analyzed by evaluation of the variation of their information rate with their “randomness” varying. It results that an ad-hoc tradeoff between the different requirements (LPI, PSLR) is required in most cases.

Airport Surveillance Processing Chain for High Resolution Radar

The paper focuses on the design of the digital processing chain of a surface movement radar (SMR) for airport traffic in the frame of A-SMGCS (advanced-surface movements guidance and control system); in order to reach, or exceed, the demanding requirements for the A-SMGCS surveillance function, special attention has to be paid to SMR processing, whose main functional blocks are the CFAR (constant false alarm rate) processor, the plot extractor, and the track-while-scan (TWS). A description of these processing functions, tailored to a noncoherent, high-resolution radar, and of their implementation is provided. The performance evaluation is accompanied by trials on recorded data, as obtained from a national research and development project called fast prototyping (FP) project (2001-2003) and its subsequent activities. The aim of the work presented here is to give a system view of the radar processing chain for high-resolution SMR, being rather different than standard surveillance radar.

Range Sidelobes Suppression in Pulse-Compression Radar using Golay Pairs: Some Basic Limitations for Complex Targets

This study deals with a specific aspect of the well-known problem of the variation of the radar cross section of complex targets with the transmitted frequency. In particular, it considers pairs of modified Golay codes and demonstrates that-even with a modest variation of the transmitted frequency-the square complementary properties of radar returns are lost when targets are complex (i.e., made up by some point scatterers). This fact causes the range sidelobes to increase very much. A partial remedial measure to this drawback may be the simultaneous transmission of both codes by an array antenna at the same frequency.

Novel concepts for surface movement radar design

Traditional millimeter wave Surface Movement Radar (SMR) have been designed and tested. A novel concept for the design of a new SMR is suggested based upon Synthetic Aperture Antenna and Noise Radar Technology. It enables designing of SMR without mechanical rotation of an antenna, but applying several nonmoving Synthetic Aperture Antennas instead. Application of Noise Radar Technology is also considered in more detail to improve the expected performance of a new SMR.

Stochastic simulation techniques as related to innovation in communications-navigation-surveillance and air traffic management (CNS/ATM)

The design and operational tuning of the instruments and procedures employed in communications-navigation-surveillance (CNS) and air traffic management (ATM) often relies on stochastic simulation techniques. In this paper the application areas of simulation in the CNS/ATM context are reviewed together with the simulation methods that can help solve the main problems encountered, i.e. quick simulation techniques for the simulation of rare events, and the bootstrap technique for the evaluation of the accuracy of the results.

Interference problems expected when solid-state marine radars will come into widespread use

The increasing environmental consciousness and the better attention being paid to the primary resources (especially oil and raw materials) is one of the main drivers of the increase in vessel traffic. Moreover, sea shipping is characterized by a good delivery rate and by affordable operating costs in comparison with other transport means, i.e. by road, rail or air. For this reasons, the continuous increase of vessel traffic requires a high degree of control and an adequate assistance to the navigation, in order to ensure safety, reduction of risks for the environment, as well as an efficient, quick and comfortable navigation. The paper describes the evolution of the marine radar systems pointing out the advantages and the potential drawbacks due to the implementation of solid state technology in the incoming, new generation solid-state, high duty cycle marine radars.