1,721,008 research outputs found
Phase coding of RF pulses in photonics-aided frequency-agile coherent radar systems
Full text linkAn innovative optical scheme to generate software-defined phase-modulated radio frequency (RF) pulses with carrier frequency agility from a mode-locked laser (MLL) is proposed. The technique exploits a direct digital synthesizer and a Mach-Zehnder modulator to apply an intermediate frequency modulation to the MLL's modes. The heterodyne detection of the optical signal allows the generation of amplitude- and phase-modulated RF carriers with very high phase stability, suitable for coherent radar applications. Further, a single MLL can be used to generate carriers simultaneously at different frequencies, enabling frequency hopping or multifunctional radars, with no need to increase the complexity of the transmitter. Results show chirped and Barker-coded pulses at around 10 or 40 GHz in a single setup, without any performance degradation while increasing the carrier frequency. The proposed technique allows the practical realization of compressed pulses for coherent radars over a wide carrier frequency range, allowing the development of software-defined radar systems with improved functionalities. © 1965-2012 IEEE
Flexible receiver for multiband orthogonal frequency division multiplexing signals at the millimeter waveband based on optical downconversion
No full textA novel (to our knowledge) and flexible photonics-based downconversion scheme is proposed for wireless receivers in base stations. It allows simultaneous detection of multiple signals at carriers up to tens of gigahertz, enabling communications at millimeter waves. Experiments demonstrate the effective downconversion of Wi-Fi signals at 2.4 and 39.8 GHz with the error vector magniture <−43 dB
Photonic generation of microwave phase coded radar signal
No full textIn modern radar systems, the requirements of resolution, sensitivity, and flexibility are pushing the development of reconfigurable and software-defined radio-frequency (RF) signal generators, capable of producing radar pulses with arbitrary amplitude and phase, over high-frequency carriers with the phase stability required by coherent radar applications. In this work we propose a photonic based approach for generating very-high-frequency radar signals with advanced phase coding. The scheme exploits a Mode Locked Laser and an IQ electro-optical Mach Zehnder Modulator. Experimental results obtained around 25GHz relative to Barker and Frank codes are presented and compared with numerical simulations in order to demonstrate the effectiveness of the proposed technique. The proposed scheme shows potentials for wideband modulation and could represent a promising solution for the implementation of fully digital radar systems
SDR multiband radars based on photonics for aerial and naval scenarios:from the concept to the field trials
No full textPhotonic generation of phase-modulated RF signals for pulse compression techniques in coherent radars
Full text linkA novel and flexible photonics-based scheme is proposed for generating phase-coded RF pulses suitable for coherent radar systems with pulse compression techniques. After selecting two modes from a mode-locked laser (MLL), the technique exploits an optical in-phase/quadrature modulator driven by a low-sample rate and low-noise direct digital synthesizer to modulate the phase of only one mode. The two laser modes are then heterodyned in a photodiode, and the RF pulse is properly filtered out. The scheme is experimentally validated implementing a 4-bit Barker code and a linear chirp on radar pulses with a carrier frequency of about 25 GHz, starting from an MLL at about 10 GHz. The measures of phase noise, amplitude- and phase-transients, and autocorrelation functions confirm the effectiveness of the scheme in producing compressed radar pulses without affecting the phase stability of the optically generated high-frequency carriers. An increase in the radar resolution from 150 to 37.5 m is calculated. The proposed scheme is capable of flexibly generating software-defined phase-modulated RF pulses with high stability, even at very high carrier frequency, using only a single commercial device with potentials for wideband modulation. It can therefore allow a new generation of high-resolution coherent radars with reduced complexity and cost. © 1983-2012 IEEE
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