- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
[IEEE 2018 International Conference on Communication and Signal Processing (ICCSP) - Chennai (2018.4.3-2018.4.5)] 2018 International Conference on Communication and Signal Processing (ICCSP) - Envelope Modification of the Hyperbolic Frequency Modulated Signal with LC-Filters in order to have a Better Range Resolution in Radar Systems
摘要： The theme of this paper is to realize a continuous time domain window similar to the Hamming window. Windowing is used in signal processing to smooth the spectral content and for reducing the spectral leakage as well. Long time duration windows with narrow spectral content can provide much better smoothing compared with short duration windows with broad spectral content. The other advantage of the windowing in the time domain is the reduction of sidelobe levels in the output of the matched filter (MF). In radar systems which use the MF, this reduction in the relative sidelobe level improves the resolution of the system. Radar systems use the hyperbolic frequency modulated (HFM) signals to have the better range and velocity resolutions since these waveforms are Doppler invariant. To further improve the range resolution, the envelope of the HFM signal has been modified using a continuous time domain Hamming window and its Doppler invariant property has been observed. In order to realize the practical circuit that implements the analogous continuous time domain Hamming window for the HFM signal, Butterworth notch filter, and Butterworth highpass filters (HPF) has been considered and it is observed that HPF is approximating the characteristics of the Hamming window.
关键词： hyperbolic frequency modulation,matched filter,notch filter,relative sidelobe level,Doppler invariance,Auto-correlation
更新于2025-09-23 15:23:52
-
Dechirping Compression Method for Nonlinear Frequency Modulation Waveforms
摘要： This letter proposes a novel dechirp processing method for wideband nonlinear frequency modulation (NLFM) waveform which enables low sampling rate of data. As we know, NLFM waveform can easily realize optimal shape of power spectral density which helps to achieve better pulse compression result with low range sidelobes without signal-to-noise ratio degradation caused by weighting as we usually do for LFM waveforms. In the approach, hamming window is adopted in the generation of the NLFM waveform for better balance on the low range sidelobes and a relative small bandwidth. In dechirp operation, the NLFM radar echoes are mixed with a local reference LFM signal, and thus narrowband signals are resulted and only low sampling rate is needed. The dechirped NLFM signals are then up-sampled and inverse dechirped by software and ?nally matched ?ltering is conducted to complete pulse compression. Both numerically simulated data and real radar data are processed to verify the effectiveness of the proposed method.
关键词： nonlinear frequency modulation (NLFM),sampling rate,pulse compression,Dechirp processing
更新于2025-09-23 15:23:52
-
[IEEE 2018 IEEE 3rd International Conference on Signal and Image Processing (ICSIP) - Shenzhen, China (2018.7.13-2018.7.15)] 2018 IEEE 3rd International Conference on Signal and Image Processing (ICSIP) - Analysis of Linear FM Signal Based on the STFT in the Filtering Viewpoint
摘要： Analyzing signal with STFT transformation is not able to achieve a fine resolution in both the time and frequency due to the restriction of the Heisenberg–Gabor inequality. However, little has been studied about the STFT in the filtering viewpoint, such as the influence of the length of the filter impulse response. This paper mainly studies the frequency estimation of linear frequency modulated (LFM) signal with the STFT in the filtering viewpoint. The length of the filter impulse response is observed in its impact on the variation of time-frequency distribution (TFD). Based on a series of experiments, it is proved that the longer impulse response does not always guarantee the better concentration in the TFD. To obtain the best TFD for the LFM signal processing, an optimal impulse response length needs to be determined beforehand.
关键词： filtering viewpoint,frequency modulation parameters,impulse response
更新于2025-09-23 15:23:52
-
Manipulation of nanomechanical resonator via shaking optical frequency
摘要： Cavity optomechanical system has made rapid advances in the past decades, which is mainly used to study the macroscopic quantum effects of the micromechanical resonators, such as the ground-state cooling of the mechanical resonator, mechanical squeezing, entanglement, macroscopic quantum superposition, etc. Owing to the unique advantages of optomechanical systems, numerous potential applications have been proposed, e.g., the ultrahigh precision metrology, exploring the quantum-classical boundary, and studying the weak signal transducer. The progress of the gravitational-wave detection is a great example for the application of optomechanics. In recent years, the periodically modulated optomechanical systems have attracted significant attention, which have been used to study various macroscopic quantum effects. However, in those modulation proposals, most of them focus on modulating the driven laser field, which results in the first-order moments of the system operators and the effective optomechanical coupling changing periodically to achieve and study some quantum effects. On the other hand, the frequency modulated quantum systems also exhibit a rich behavior and display nonequilibrium properties that are absent in their static counterparts, such as the phenomena of motional averaging and narrowing, Landau–Zener–Stückelberg–Majorana interference, and the formation of dressed states with the appearance of sidebands in the spectrum. However, in cavity optomechanical systems, the study of the influence coming from the frequency modulation is relatively rare to date. In this paper, we study an usual cavity optomechanical system where the frequency of the optical mode is shaken periodically. As we all know, the stability of optomechanical systems is closely related to the effective optomechanical coupling strength. For an excessively large coupling strength, the optomechanical systems are unstable and the studying is also meaningless. However, we find that the shaking optical mode can reduce the effective optomechanical coupling strength arbitrarily when the shaking frequency is much larger than the mechanical resonator frequency, and the deeply physical mechanism can be explained through the Raman-scattering and frequency domain pictures. The result indicates that it will be possible to study the steady quantum effects of optomechanical system even with strong coupling where the standard optomechanical systems without frequency modulation are always unstable. In order to verify the above analyses, we study the ground-state cooling of the mechanical resonator and the entanglement between the optical and mechanical modes in the conventional unstable region, and the results indicate that the final mean phonon number and entanglement not only can be achieved but also can be modulated by the optical shaking parameters. Our proposal provides a method to study the macroscopic quantum effects even in conventional unstable region.
关键词： micromechanical resonator cooling,entanglement,frequency modulation,optomechanics
更新于2025-09-23 15:22:29
-
A High-Resolution 220-GHz Ultra-Wideband Fully Integrated ISAR Imaging System
摘要： In this paper, an ultra-wideband fully integrated imaging radar at sub-terahertz (sub-THz) frequencies is presented, which demonstrates a fine lateral resolution without using any focal lens/mirror. We have achieved a lateral resolution of 2 mm for an object at 23-cm distance as well as a range resolution of 2.7 mm. To achieve the decent range resolution, in a frequency modulation continuous wave radar configuration, a state-of-the-art chirp bandwidth (BW) of 62.4 GHz at a center frequency of 221.1 GHz is generated and efficiently radiated. We have presented a design technique for the optimal design of the passive embedding around the core transistor to maximize the tuning BW of the voltage controlled oscillator. At the receiver side, to maximize the intermediate frequency level, a subharmonic mixer is utilized, which is designed for the lowest conversion loss. Finally, to obtain the fine lateral resolution, we have implemented near-field beamforming algorithm based on the inverse synthetic aperture radar (ISAR) systems. The synthesized beamwidth is less than 0.5°; hence, high-resolution images are reconstructed. The system is fabricated in a 55-nm BiCMOS process. To the best of our knowledge, this is the first imaging radar at THz/sub-THz frequencies, which utilizes ISAR to achieve a high lateral resolution while the radar system is fully integrated.
关键词： ultra-wideband,Frequency modulation continuous wave (FMCW),remote sensing,THz,radar,sub-terahertz (sub-THz),oscillator,inverse synthetic aperture radar (ISAR),plane wave
更新于2025-09-23 15:21:21
-
Increase of an Output Optical Signal of an Acousto-Optic Monochromator upon Frequency Modulation of a Control Signal
摘要： An angular aperture of an acousto-optical filter upon a linear frequency-modulated (chirp) control signal has been experimentally studied for the first time. The results of studying the spectral and angular dependences of the spectral transmission function of a filter upon a frequency modulation have shown the possibility of an efficient increase of the output optical signal. The value of the optical signal was increased by 2000 times using the selected design of the acousto-optical filter. This makes it possible to obtain a gain in the measurement time or in the value of the detected optical signal. Such an increase of the output signal upon a chirp control signal is provided by the increase of the angular aperture and broadening of the spectral transmission bandwidth together with the required proportional increase of the control signal power.
关键词： angular aperture,output optical signal,spectral transmission function,acousto-optical filter,frequency modulation
更新于2025-09-23 15:21:01
-
Resonance Frequency Modulation for Rapid Point-of-care Ebola Glycoprotein Diagnosis with a Graphene-based Field-effect Bio-transistor
摘要： Recent outbreaks of the Ebola virus infection in several countries demand a rapid point-of-care (POC) detection strategy. This paper reports on an innovative pathway founded on electronic resonance frequency modulation to detect Ebola glycoprotein (GP), based on carrier injection-trapping-release-transfer mechanism and standard antibody-antigen interaction principle within a dielectric-gated reduced graphene oxide (rGO) field-effect transistor (GFET). The sensitivity of the current Ebola detection can be significantly enhanced by monitoring the device’s electronic resonance frequency, such as inflection frequency (fi), where phase angle reaches maximum (θmax). In addition to excellent selectivity, a sensitivity of ~36-160 % and ~17-40 % for 0.001-3.401 mg/L Ebola GP can be achieved at high and low inflection resonance frequencies, respectively, which are several orders of magnitude higher than the sensitivity from other electronic parameters (e.g., resistance-based sensitivity). Using equivalent circuit modelling on contributions of channel and contact, analytical equations for resonance shift have been generalized. When matching with the incoming ac measurement signal, electronic resonance from the phase angle spectrum is evolved from various relaxation processes (e.g., trap and release of injected charge at surface trap sites of channel-gate oxide and channel-source/drain interface) that are associated with a characteristic emission frequency. Using charge relaxation dynamics, a high-performance bio-FET sensing platform for healthcare and bio-electronic applications is realized through resonance shifting.
关键词： graphene-based field-effect transistor,Ebola glycoprotein,resonance frequency modulation,point-of-care detection,bio-FET sensing platform
更新于2025-09-23 15:21:01
-
Applicability of small-signal laser and fiber models for passive optical networks operating at the 1550??nm window
摘要： Small-signal techniques are a useful engineering tool to estimate system performance, though small-signal models need to be tested against the large-signal from which they are derived. We show that combined small-signal models for lasers and optical fiber are valid for passive optical networks employing directly modulated semiconductor lasers, provided that the modulation extinction ratios are < 4 dB and the transmission distances < 25 km. For larger extinction ratios and longer transmission distances, large-signal approaches are needed in order to investigate system capabilities. The small-signal models break down due to the increasing adiabatic chirp in semiconductor lasers with increasing modulation current. We estimate how the small-signal models can estimate for the performance of 10 Gbit/s signal from directly modulated lasers. We verify the equivalence of the small-signal and large-signal regimes and we develop a quality metric to identify the range of fiber lengths and signal extinction ratios over which the small-regime remains valid.
关键词： Frequency,Modulation,Passive Optical Networks,Semiconductor lasers,Phase,Fiber dispersion,Numerical modelling
更新于2025-09-23 15:19:57
-
[IEEE 2019 Joint Conference of the IEEE International Frequency Control Symposium anEuropean Frequency and Time Forum (EFTF/IFC) - Orlando, FL, USA (2019.4.14-2019.4.18)] 2019 Joint Conference of the IEEE International Frequency Control Symposium and European Frequency and Time Forum (EFTF/IFC) - A Versatile Testbed for CubeSat Atomic Clock Development: EOM vs Laser Current Modulation
摘要： Atomic clocks for compact satellite missions have limitations on size, weight, and power (SWaP), while requiring ever greater levels of frequency stability and accuracy. To aid in the development of next-generation low SWaP Coherent Population Trapping (CPT) clocks, we are developing a CubeSat Atomic Clock Testbed (CuSACT). This testbed will give us the capability to vary single aspects of CPT-clock design while keeping all others constant. In this presentation, we will provide an overview of CuSACT, and discuss our preliminary results comparing direct injection-current modulation of a VCSEL with electro-optic phase modulation of the VCSEL.
关键词： vapor-cell atomic clock,coherent population trapping,Rb clock,frequency modulation,electro-optic modulation,VCSEL,optical sidebands
更新于2025-09-16 10:30:52
-
[Laser Institute of America ICALEO? 2016: 35th International Congress on Applications of Lasers & Electro-Optics - San Diego, California, USA (October 16–20, 2016)] International Congress on Applications of Lasers & Electro-Optics - Velocity and range measurement optical frequency stepped chirp modulated coherent LIDAR for space application
摘要： The spacecraft landing on Mars or other planets generally requires measuring relative velocity and distance between itself and the land. The measurement demands high accuracy and high reliability. This paper presents an optical frequency stepped chirp modulated pulse train coherent lidar technology for range and velocity measurement. This paper advances an all-fiber structure lidar. It has advantages of small size, high efficiency, low power consumption and stable performance. This paper introduces the optical frequency stepped chirp modulation technology. It gives the semiconductor seed laser theoretical model of driver current versus laser frequency, and computes the modulation waveform. We use an AWG (arbitrary waveform generator) to load the waveform and get the optical stepped chirp modulated pulse train. This paper derives the ambiguous function of the lidar. This function provides a powerful tool to analyze the property and find the highlight property of this lidar: high effective time-bandwidth products. The property gives high range accuracy and velocity accuracy. The signal processing method is advanced. The algorithm can get the range and velocity simultaneously. The Doppler effect caused by target motion is analyzed. The rang walk error caused by Doppler effect is compensated by special algorithm.
关键词： Optical coherence,detection,frequency modulation,lidar,Doppler effect,fiber laser
更新于2025-09-16 10:30:52