A RF spectrum analyzer with high performance and unique capabilities that traditional all-electronic spectrum analyzers
do not exhibit is demonstrated. The system is based on photonic signal processing techniques that have enabled us to
demonstrate the spectral analysis of a 1.5 GHz bandwidth with a 1.4 ms update time and a resolution bandwidth of 31
kHz. We observed a 100% probability of intercept for all signals, including short pulses, during the measurement
window. The spectrum analyzer operated over the 0.5 to 2.0 GHz range and exhibited a spur-free dynamic range of 42
dB. The potential applications of such a system are extensive and include: detection and location of transient electromagnetic
signals, spectrum monitoring for adaptive communications such as spectrum-sensing cognitive radio, and
battlefield spectrum management.
Spectral-spatial holographic crystals have the unique ability to resolve fine spectral features (down to kilohertz) in an optical waveform over a broad bandwidth (over 10 gigahertz). This ability allows these crystals to record the spectral interference between spread spectrum waveforms that are temporally separated by up to several microseconds. Such crystals can be used for performing radar range-Doppler processing with fine temporal resolution. An added feature of these crystals is the long upper state lifetime of the absorbing rare earth ions, which allows the coherent integration of multiple recorded spectra, yielding integration gain and significant processing gain enhancement for selected code sets, as well as high resolution Doppler processing. Parallel processing of over 10,000 beams could be achieved with a crystal the size of a sugar cube.
Spectral-spatial holographic processing and coherent integration of up to 2.5 Gigabit per second coded waveforms and of lengths up to 2047 bits has previously been reported. In this paper, we present the first demonstration of Doppler processing with these crystals. Doppler resolution down to a few hundred Hz for broadband radar signals can be achieved. The processing can be performed directly on signals modulated onto IF carriers (up to several gigahertz) without having to mix the signals down to baseband and without having to employ broadband analog to digital conversion.
The pattern matching for fingerprints requires a large amount of data and computation time. Practical fingerprint
identification systems require minimal errors and ultrafast processing time to perform real time verification and
identification. By utilizing the two-dimensional processing capability, ultrafast processing speed and noninterfering
communication of optical processing techniques, fingerprint identification systems can be
implemented in real time. Among the various pattern matching systems, the joint transform correlator (JTC) has
been found to be inherently suitable for real time matching applications. Among the various JTCs, the fringeadjusted
JTC has been found to yield significantly better correlation output compared to alternate JTCs. In this
paper, we review the latest trends and advancements in fingerprint identification system based on the fringeadjusted
JTC. Since all pattern matching systems suffer from high sensitivity to distortions, the synthetic
discriminant function concept has been incorporated in fringe-adjusted JTC to ensure distortion-invariant
fingerprint identification. On the other hand a novel polarization-enhanced fingerprint verification system is
described where a polarized coherent light beam is used to record spatially dependent response of the scattering
medium of the fingerprint to provide detailed surface information, which is not accessible to mere intensity
measurement. It is shown that polarization-enhanced database improves the accuracy of the fingerprint
identification or verification system significantly.
Keywords: Fringe-adjust joint transform correlation, finger print identification, polarization, synthetic
The design, performance analysis and experimental demonstration for an analog, broadband, high performance electro-optical signal processor are presented. The Spatial Spectral (S2) Coherent Holographic Integrating Processor, or S2-CHIP, has been developed recently as a broadband core-component for range and mid-to-high pulse repetition frequency radar-signal processing systems, as well as for lidar and radio astronomy applications. In a range radar system, if the transmit and receive RF waveforms are modulated onto a stable optical carrier, the S2 material will perform the analog correlation of the transmit and receive signals to yield the target’s range, and also coherent integrate multiple return results to increase the signal-to-noise-ratio and provide for target velocity determination. Preliminary experimental results are shown of S2-CHIP range processing using a 1.0 Gb/s data rate with 512-bit BPSK pulses. Good range resolution is observed for delays up to 1.0 microsecond. The ability of the processor’s to handle dynamic coding on the transmit RF waveforms is demonstrated.
The design issues for the technique of continuously programming a coherent transient spatial-spectral optical signal processor are discussed. The repeated application of two spatially distinct optical programming pulses to a non- persistent hole-burning material writes an accumulated, spatial-spectral population grating with low intensity optical pulses as compared to single shot programing. An optical data stream is introduced on a third beam, resulting in a processor output signal spatially distinct from all the input pulses. Programming and processing take place simultaneously, asynchronously and continuously. For accumulated gratings, the frequency stability of the optical source is an important consideration. Assuming a sufficiently stable optical source, simulations show that an accumulated (and maintained) grating in steady state, for both storage of a true-time delay and/or pattern waveform, can be highly efficient using currently available materials, on the order of that predicted for a perfect photon-gated device. An experimental demonstration of the continuous programming concept for true time delays programmed with chirped pulses is presented, showing the accumulation of the grating with low area pulses over time until it reaches steady state, for times longer than the persistence of the material.