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Modeling And Experiments On Time-Interleaved Photonic Analog-to-Digital Converters

Posted on:2018-02-05Degree:DoctorType:Dissertation
Country:ChinaCandidate:F R SuFull Text:PDF
GTID:1368330590955281Subject:Electronic Science and Technology
Abstract/Summary:PDF Full Text Request
Analog-to-digital converters(ADCs),as one of the key devices in modern information system,are an important bridge connecting the physical world and the digital world.With the development of informatization,ADCs have already come into information technologies in various fields,such as measuring instruments,radar systems,auto-control systems and communication.To expand the scope of application,one of the main themes of studying ADCs is using innovations to improve their performance.Photonic ADCs are a promising way under development and are expected to replace pure electronic ADCs used mostly today.Photonic ADCs overcome the dilemma and bottleneck of pure electronic ADCs;they take into account today's photon technology and electronic technology development level and characteristics and combine the two creatively.As a result,photonic ADCs make best use of the advantages,bypass the disadvantages and make progress on overall performance.The photonic ADCs discussed in this thesis are time-interleaved photonic ADCs(TIPADCs).The TIPADCs are optic-electronic hybrid,with front-end taking photon technology for processing,back-end taking electronic technology for processing,and passively mode-locked laser offering clock source.Optical front-end makes use of high bandwidth and low jitter,while electrical back-end enables TIPADCs to quantize with high bits and high precision and compatible with existing digital circuits.Besides,time-interleaved sampling,which is composed of lowrate devices,can work well under high rate.Among numerous solutions,TIPADCs are one of the most promising schemes and have become the focus of attention in the frontier scientific research field.At present,TIPADCs have their own problems and some research blind spots.The most striking problem is the lack of basic models and system analysis based on the models.The thesis takes the problem as a starting point and carries out our research.Firstly,we discover the commutativity between multiplication and convolution under certain circumstance: the result of synchronous sampling a signal after periodic modulation is the same with the result of sampling a signal after passing through an equivalent system.Secondly,by studying each part of the system,we build the original model of the TIPADCs on behavioral level.Applying the commutativity between multiplication and convolution in the original model,we can get an equivalent model of the TIPADCs.Then the equivalent channel response of each channel in the TIPADC is available from the equivalent model.On the basis of equivalent channel effect,we continue to study the bandwidth of the TIPADCs and find that the global lowest feasible bandwidth of the back-end is half the sampling rate of the single channel to achieve continuous and high channel bandwidth of the equivalent channel response;while the bandwidth of the equivalent is mostly up to the bandwidth of optical pulse and modulator.We implement a channel-frequency-response test platform to verify theoretical analysis about channel response bandwidth and the platform is up to 40 GHz.The platform can measure optical pulse temporal shape with sampling precision below 1ps,and optical pulse bandwidth and back-end bandwidth can be adjusted.Conclusions drawn by theoretical analysis when back-end is low-passed is verified based on the platform.We work on the feature of channel gain,delay and offset.When the inter-symbol interference(ISI)introduced by the back-end cannot be neglected,the channel response exhibits frequency selectivity,so we cannot describe channel characteristics with a unitized gain and delay.Without ISI,channel gain and delay do not change along with frequency.Channel gain directly relates to optical pulse delay,back-end delay and back-end response and channel delay is only concerned with optical pulse delay.Also,if there is no ISI and if channel gain directly proportional to back-end response's peak value,then channel gain is directly proportional to back-end bandwidth.To test theoretical analysis about channel gain,delay and offset,we extend the function of the test platform and measurement results verify relevant conclusions drawn in the present of back-end induced ISI.Relevant conclusions drawn when there is no ISI are also verified.Finally,using the nature of the equivalent channel response effect,we implement TIPADCs with a built-in pre-filterer by changing the temporal shape of optical pulses.The scheme has two features: on one hand,the impulse response of the filtering is directly proportionally to the time inversion of temporal shape of optical pulses,the feasibility of the latter can cause the latter to be flexible;on the other hand,with the built-in filtering response,we do not need extra filters.To test TIPADCs with a built-in pre-filterer,we introduce pulse shaping.It can control temporal shape of optical pulses by program and change the filtering response.Some 24 GHz band-pass filters are built in the platform and it can then generate any phase shift after reconfiguration.The thesis concludes with a review of the entire study,summarizes above according to the logic of the research and looks forward to the future of the research topic.
Keywords/Search Tags:time interleaving, photonic analog-to-digital converter, channel response, gain, bandwidth, delay, offset, microwave photonic filter
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