Tunable microwave signal generation based on an Opto-DMD processor and a photonic crystal fiber

Frequency-tunable microwave signal generation is proposed and experimentally demonstrated with a dual-wavelength single-longitudinal-mode （SLM） erbium-doped fiber ring laser based on a digital Opto-DMD processor and four-wave mixing （FWM） in a high-nonlinear photonic crystal fiber （PCF）. The high-nonlinear PCF is employed for the generation of the FWM to obtain stable and uniform dual-wavelength oscillation. Two different short passive sub-ring cavities in the main ring cavity serve as mode filters to make SLM lasing. The two lasing wavelengths are electronically selected by loading different gratings on the Opto-DMD processor controlled with a computer. The wavelength spacing can be smartly adjusted from 0.165 nm to 1.08 nm within a tuning accuracy of 0.055 nm. Two microwave signals at 17.23 GHz and 27.47 GHz are achieved. The stability of the microwave signal is discussed. The system has the ability to generate a 137.36-GHz photonic millimeter signal at room temperature.

Control of microwave signals using bichromatic electromechanically induced transparency in multimode circuit electromechanical systems

We theoretically investigate the tunable delay and advancement of microwave signals based on bichromatic electromechanically induced transparency in a three-mode circuit electromechanical system, where two nanomechanical resonators with closely spaced frequencies are independently coupled to a common microwave cavity. In the presence of a strong microwave pump field, we obtain two transparency windows accompanied by steep phase dispersion in the transmitted microwave probe field. The width of the transparency window and the group delay of the probe field can be controlled effectively by the power of the pump field. It is shown that the maximum group delay of 0.12 ms and the advancement of0.27 ms can be obtained in the current experiments.

High-power linear-polarization burst-mode all-fibre laser and generation of frequency-adjustable microwave signal

Narrowband microwave generation with tuneable frequency is demonstrated by illuminating a photoconductive semiconductor switch(PCSS)with a burst-mode fibre laser.The whole system is composed of a high-power linearly polarized burst-mode pulsed fibre laser and a linear-state PCSS.To obtain a high-performance microwave signal,a desired envelope of burst is necessary and a pulse pre-compensation technique is adopted to avoid envelope distortion induced by the gain-saturation effect.Resulting from the technique,homogenous peak power distribution in each burst is ensured.The maximum energy of the laser burst pulse reaches 200μJ with a burst duration of 100 ns at the average power of 10 W,corresponding to a peak power of 4 kW.When the PCSS is illuminated by the burst-mode fibre laser,narrowband microwave generation with tuneable frequency(0.80-1.12 GHz)is obtained with a power up to 300 W.To the best of the authors’knowledge,it is the first demonstration of frequency-tuneable narrowband microwave generation based on a fibre laser.The high-power burst-mode fibre laser reported here has great potential for generating high-power arbitrary microwave signals for a great deal of applicable demands such as smart adaptive radar and intelligent high-power microwave systems.

Single-shot incoherent optical processing of microwave signals： opening the path to low cost high performance analog photonics

Incoherent optical processing of microwave signals,where low-coherence broadband light sources are employed instead of costly mode locked lasers,has attracted great interest thanks to its wide applications in microwave photonics filtering[1–3],arbitrary generation[4–6]and analog to digital conversion[7]。

Photonic generation of ASK microwave signals with SSB format

Optical beating is the usual approach to generation of microwave signals.However,the highest frequency achievable for microwave signals is limited by the bandwidths of optoelectronic devices.To maximize the microwave frequency with a limited bandwidth of a photodetector(PD)and relieve the bandwidth bottleneck,we propose to generate microwave signals with the single sideband(SSB)format by beating a continuous wave(CW)light with an optical SSB signal.By simply adjusting the frequency diference between the CW light and the carrier of the optical SSB signal,the frequency of the generated microwave SSB signal is changed correspondingly.In the experiment,amplitude shift keying(ASK)microwave signals with the SSB format are successfully generated with diferent carrier frequencies and coding bit rates,and the recovered coding information agrees well with the original pseudo random binary sequence(PRBS)of 2^(7)−1 bits.The proposed approach can signifcantly relieve the bandwidth restriction set by optoelectronic devices in high-speed microwave communication systems.

Tunable photonic microwave generated by multi-wavelength Brillouin fiber laser

Aimed at the problem of narrow tunability and low frequency microwave signal generated by the optical method,a novel approach to stabilizing the tunable photonic microwave generated by the multi-wavelength Brillouin fiber laser is proposed and is experimentally demonstrated.A singlelongitudinal-mode Brillouin fiber laser is designed,and by using the laser,a multi-wavelength Brillouin fiber laser with more than eleven orders of Stokes wave is observed.The wavelength spacing of the adjacent Stokes wave is 0.085 nm.If the Brillouin pump power is increased,the number of Stokes wave output can be further increased.The tunable microwave signals of 10.8 and 21.6 GHz are obtained by heterodyning the Rayleigh wave and Stokes wave of the multiwavelength Brillouin fiber laser.In the experiment,by tuning the pump wavelength and temperature of the gain fiber,microwave signals at different frequencies are generated.The tunable frequency range can be further expanded by using a temperature controller with a wider adjustment range,and the generated microwave signal exhibits high stability on frequency.

Nonlinear Properties of an Inhomogeneous Diode Structure in a Strong Microwave Field

Results of experimental investigation of detection (rectification) of high power X-band microwave signal in diodes of various design (semiconductor p-n-junction, point-contact, Schottky, Metal-Isolator-Metal—MIM) are reported. The maximum of the detected direct voltage V vs. power P of microwave signal and subsequent polarity reversal, previously found in MIM diodes in the optical and microwave bands, have found to be characteristic of all investigated diodes as well. After the reversal of polarity, this dependence comes linear, and the sign of the voltage corresponds to thermoEMF. In some diodes, the hysteresis on V(P) was observed. All 5 types of V(P) of MIM diodes (have made from different pairs of metals), reported earlier, were reproduced on same p-n-junction diode by variable external DC bias. These results joined with abnormal frequency cutoff forced to suggest that there is an unknown mechanism for direct flow of charge carriers (and for generate direct current) in the high-frequency electrical field, which differs from the conventional rectification.

The microwave large signal load line of an InGaP HBT

The microwave dynamic load line characteristics of an advanced InGaP HBT are investigated experimentally and analyzed at small signal level and at large signal level for microwave power amplification. Investigation results show that the dynamic load curves are not always like an elliptic curve, and the current extreme points do not locate at voltage extreme points. The dynamic load curve current extreme point lines sit at the small signal load line up to the P-3dB point, and the lines show a constant slope from a small signal up to the saturation power point. A method to calculate the realistically delivered power to load is presented which fits the test result well.

Photonic-assisted FSK signal generation based on carrier phase-shifted double sideband modulation

An approach to generate high-speed and wideband frequency shift keying(FSK)signals based on carrier phase-shifted double sideband(CPS-DSB)modulation is proposed and experimentally validated.The core part of the scheme is a pair of cascaded polarization-sensitive LiNbO_(3) Mach–Zehnder modulators and phase modulators,whose polarization directions of the principal axes are mutually orthogonal to each other.A proof-of-concept experiment is carried out,where a 0.5 Gb/s FSK signal with the carrier frequencies of 4 and 8 GHz and a 1 Gb/s FSK signal with the carrier frequencies of 8 and 16 GHz are generated successfully.

Microwave Communication Under Weak Intensity to Quantumized Level:Recent Progress and Future Challenges

We provide an overview of the recent progresses on the system architecture design and performance prediction for microwave signal detection under weak signal intensity regime,up to quantumized level.The technique roadmap includes two perspectives,the opto-electro-mechanical(OEM)and superconducting devices.For the former one,we first overview the concept of OEM,and then introduce the signal detection based on capacitive-opto-electro-mechanical systems and piezoopto-electro-mechanical systems.For the latter one,we first overview the concept and architecture of Josephson junction,and then introduce the signal detection based on superconducting Hanbury Brown-Twiss(HBT)experiments andΛenergy-level splitting system.Besides,we review the microwave detection based on Rydberg atom system.We believe that this overview can provide a guidance for future transmission limit,signal processing,detection device fabrication and real experiments.

Use of Hi-resolution data for evaluating accuracy of traffic volume counts collected by microwave sensors

Over the past few years, the Utah Department of Transportation has developed the signal performance metrics （SPMs） system to evaluate the performance of signalized in- tersections dynamically. This system currently provides data summaries for several per- formance measures, one of them being turning movement counts collected by microwave sensors. As this system became public, there was a need to evaluate the accuracy of the data placed on the SPMs. A large-scale data collection was carried out to meet this need. Vehicles in the Hi-resolution data from microwave sensors were matched with the vehicles by ground-truth volume count data. Matching vehicles from the microwave sensor data and the ground-truth data manually collected required significant effort, A spreadsheet- based data analysis procedure was developed to carry out the task. A mixed model analysis of variance was used to analyze the effects of the factors considered on turning volume count accuracy. The analysis found that approach volume level and number of approach lanes would have significant effect on the accuracy of turning volume counts but the location of the sensors did not significantly affect the accuracy of turning volume counts. In addition, it was found that the location of lanes in relation to the sensor did not significantly affect the accuracy of lane-by-lane volume counts. This indicated that accu- racy analysis could be performed by using total approach volumes without comparing specific turning counts, that is, left-turn, through and right-turn movements. In general, the accuracy of approach volume counts collected by microwave sensors were within the margin of error that traffic engineers could accept. The procedure taken to perform the analysis and a summary of accuracy of volume counts for the factor combinations considered are presented in this paper.

Development of a daily soil moisture product for the period of2002–2011 in Chinese mainland

Soil moisture is an essential climate variable(ECV) concerned widely. Due to its high spatial variability, it is costly to measure soil moisture at tens of kilometers scale. In this study, a ten-year(2002–2011) daily soil moisture dataset at 0.25° spatial resolution for Chinese mainland was produced through assimilating the Advanced Microwave Scanning Radiometer for Earth Observing System(AMSR-E) brightness temperature(TB) data into a land surface model(LSM). The obtained soil moisture data was evaluated against soil moisture-measuring networks deployed in two wet areas and one dry area of the Tibetan Plateau.The results show that for the wet areas the accuracy of the soil moisture product obtained from the assimilation is considerably higher than that of both AMSR-E official soil moisture products and land surface simulation results, and for the dry area their accuracy is comparable to each other. The spatial pattern of the soil moisture from the new product is consistent with that of soil porosity from an independent survey-based dataset, further confirming the credibility of the new product. According to this product, the transition regions in China show stronger seasonal variation of soil moisture than dry and wet regions, and drier regions have stronger inter-annual variability of soil moisture than wetter regions, particularly during transitional seasons(spring and autumn). The soil moisture product is accessible at the National Tibetan Plateau Data Center.