Photonic analog-to-digital conversion with equivalent analog prefiltering by shaping sampling pulses

Abstract

We propose a photonic scheme to digitize RF signals with a programmable equivalent analog prefilter, where the filter impulse response is directly proportional to the time-reversed temporal shape of the sampling pulse and hence can be adjusted by shaping sampling pulses. The model of the proposed scheme is presented to prove its principle and derive its operation conditions. A four-channel scheme with program-controlled pre-filters is demonstrated experimentally, where bandpass filters with the phase shifts of 0°, 90°, 180°, and 270° are synthesized, respectively, by changing temporal shape of the sampling pulses. The experimental results agree well with the theoretical analysis, indicating the validity of the proposed scheme.

Ultrafast and Wideband Microwave Photonic Frequency-Hopping Systems: A Review

“…In this section, we discuss and compare the principles, hopping Microwave photonics (MWP), which bridges RF signal and photonic signal processing, is capable of overcoming bottlenecks in electronics due to its large bandwidth, instantaneous response, as well as flexibility and reconfigurability [8]. Various RF signal processing tasks have been successfully demonstrated using photonic technologies [9][10][11][12][13][14][15][16][17][18][19], such as MWP analog-to-digital converters, MWP filters, MWP arbitrary waveform generators, MWP image rejection mixer, and MWP frequency measurement, to name a few. Although microwave photonic approaches are capable of generating various types of RF signals [20], it is not trivial to use them for generating frequency-hopping signals due to the limited frequency tunability and hopping speed in the existing signal generating approaches, as well as the time required to stabilize at the desired frequency.…”

An Optical Pulse Shaping Scheme for Simultaneous Photonic Filtering and Digitizing Systems

“…4(c). The intensity spectra can simulate the equivalent filter response of the optical pulses shaped by single path and multiple paths [1]. The simulated equivalent filter responses indicate that the 3 dB bandwidth is reduced from 2.44 GHz to 0.99 GHz when multiple paths were coupled together.…”

“…To achieve equivalent filter response with narrow bandwidth at high central frequency, optical pulses with both high temporal precision and long duration time are required in simultaneous photonic filtering and digitizing systems. In previous work [1]- [3], since temporal precision and duration time of the generated optical pulses are limited by pulse shaping schemes, what can be achieved is equivalent filter response with either high central frequency and wide bandwidth of 10 GHz [1], or delicate bandwidth of 1 GHz and limited central frequency [2], [3]. This motivates us to explore other pulse shaping schemes suitable to be implemented in simultaneous photonic filtering and digitizing systems, so that the system can have narrow-bandwidth equivalent filter response at high central frequency.…”

“…Recently, an simultaneous photonic filtering and digitizing system [1]- [3] has been proposed. The system can achieve the integrated function of filtering and digitizing of input RF signals by combining optical pulse shaping and photonic analog-to-digital convertors (PADC), and therefore avoids multi-stage electro-optic and optic-electric conversion in the direct cascade of microwave photonic filters (MPFs) [4]- [6] and PADCs [7]- [9].…”

A Photonic Digitization Scheme With Enhanced Bit Resolution Based on Hierarchical Quantization

“…The wideband signal acquisition, such as wideband radars, electronic monitor, high-speed optical and wireless communications, requires high performance analog-todigital conversion (ADC) [1][2][3]. However, limited by the inherent aperture jitter of sampling clock and comparator ambiguity, it is a big challenge for the current electronic ADCs to digitize analog signals with a sampling rate over tens of gigahertz while keeping high resolution [4].…”