This paper presents a method for exploiting wideband spectral information of real-valued radio frequency (RF) signals using the Nyquist Folding Receiver architecture. A new system model based on a symmetric modulation matrix is introduced so that the frequency band of the real input signals can be estimated without in-phase and quadrature reception and processing. To recover the original frequency of the input RF signal, we use the parameter-free sparse learning via iterative minimization (SLIM) method. Finally, the proposed model and the success of the recovery algorithm are demonstrated with data collected from an experimental testbed.
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The modern advancements in digital electronics allow waveforms to be easily synthesized and captured using only digital electronics. The synthesis of radar waveforms using only digital electronics, such as Digital-to-Analog Converters (DACs) and Analog-to-Digital Converters (ADCs) allows for a majority of the analog chain to be removed from the system. In order to create a constant amplitude waveform, the amplitude distortions must be compensated for. The method chosen to compensate for the amplitude distortions is to pre-distort the waveform so, when it is influenced by the system, the output waveform has a near constant amplitude modulus. The effects of the predistortion were observed to be successful in both range and range-Doppler radar implementations.@en

Range migration is unavoidable and cannot be neglected in pulse Doppler radar when target velocity is high and/or wideband transmit signals are used. In this paper, we investigate the range and Doppler degradation due to target motion in wideband pulse Doppler radar. To correct range cell migration, an alternative focusing method is introduced by using the backprojection algorithm. The success of the method is shown by simulations.@en

This paper considers wideband beamforming and waveform design for transmission from advanced multiple channel radar systems. Hence, this paper describes the initial designs of a wideband transmit beamformer for a multi-channel high resolution radar, applicable to airborne and spaceborne radars. As a case study for this paper, we use the EcoSAR instrument developed by NASA Goddard Space Flight Center for the measurement of science parameters. The wideband EcoSAR employs two multi-channel antennas and full transmit and receive digital beamforming to generate high resolution images of the ground features. Maintaining a consistent beampattern when the bandwidth is approximately 50% of the center frequency is a challenge. Breaking this nexus relies on optimum beam weight design and accompanying waveform design; not merely the former as is typically done. The approaches of this paper have shown how the beampatterns can be maintained while meeting beam requirements.@en