Multibeam radar based on linear frequency modulated waveform diversity

Multibeam radar (MBR) systems based on waveform diversity require a set of orthogonal waveforms in order to generate multiple channels in transmission and extract them efficiently at the receiver with digital signal processing. Linear frequency modulated (LFM) signals are extensively used in radar systems due to their pulse compression properties, Doppler tolerance, and ease of generation. Here, the authors investigate the level of isolation between MBR channels based on LFM chirps with rectangular and Gaussian amplitude envelopes. The orthogonal properties and the mathematical expressions of the isolation are derived as a function of the chirp design diversity, and specifically for diverse frequency slopes and frequency offsets. The analytical expressions are validated with a set of simulations as well as with experiments at C-band using a rotating target

Signal design and processing for noise radar

An efficient and secure use of the electromagnetic spectrum by different telecommunications and radar systems represents, today, a focal research point, as the coexistence of different radio-frequency sources at the same time and in the same frequency band requires the solution of a non-trivial interference problem. Normally, this is addressed with diversity in frequency, space, time, polarization, or code. In some radar applications, a secure use of the spectrum calls for the design of a set of transmitted waveforms highly resilient to interception and exploitation, i.e., with low probability of intercept/ exploitation capability. In this frame, the noise radar technology (NRT) transmits noise-like waveforms and uses correlation processing of radar echoes for their optimal reception. After a review of the NRT as developed in the last decades, the aim of this paper is to show that NRT can represent a valid solution to the aforesaid problems

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