Adaptive RF-photonic arbitrary waveform generator

Generation of Power-Efficient FCC-Compliant UWB Waveforms Using FBGs: Analysis and Experiment

“…This characteristic creates nonnegligible spectral content near direct current (dc), and also spectral broadening (leakage) due to time windowing. The spectral content near dc can be seen in results reported in [6]- [9], [12], [13]. Our novel use of a two-arm structure and balanced photodetection allows us to easily remove the unwanted pedestal, and achieve a desired signal that has both positive and negative going parts.…”

“…The pulse shaping device in [13] is a 4-grating and lens apparatus consists of two free space bulky gratings, two large focal length lenses to angularly disperse the frequency components, and a spatial light modulator (SLM) to modulate the amplitude of frequency components. The reflection type of this device is used in [6], where SLM is replaced by a single-layer 0733-8724/$25.00 © 2008 IEEE liquid crystal modulator (LCM).…”

Time-Domain Measurement of the Frequency-Dependent Delay of Broadband Antennas

“…This electromagnetic pulse shaping technique provides unprecedented waveform agility and enables a variety of excitation waveforms for our antenna system, which range from broadband sinusoids (constant frequency as well as frequency-stepped) [6] to highly-structured UWB impulses [7]. We note that our technique allows direct-specification of the output electrical waveform; others have demonstrated a similar technique [8] which iteratively solves for sinusoidal and frequency-modulated waveforms.…”

“…Mathematically, the frequency-dependent delay should be described by the sum of the contributions from each antenna-the sum of (7) and (8). To observe the frequency-dependent delay of this asymmetric link, we again perform direct measurements of the frequency-dependent delay as detailed previously.…”

Cell Gap Effect on the Dynamics of Liquid Crystal Phase Modulators

“…Liquid crystal (LC) spatial light modulator (SLM)has been used as a phase-only modulation for laser beam steering [1], tunable-focus lens [2][3][4][5][6], and other photonic devices [7][8]. To obtain a large phase shift while keeping operating voltage below 10 V rms , homogeneous cell (also called parallel-aligned cell) is a favorable choice.…”