Abstract: Qilian Mountain permafrost, with area about 10×10 4 km 2 , locates in the north of Qinghai‐Tibet plateau. It equips perfect conditions and has great prospecting potential for gas hydrate. The Scientific Drilling Project Gas Hydrate which Juhugeng Muri Coalfield, Tianjun County, Qinghai Province, been implemented by China Geological Survey 2008–2009. Four scientific drilling wells have completed a total footage 2059.13 m. Samples hydrate are collected separately from holes DK‐1,...

The density-based spatial clustering of application with noise (DBSCAN) algorithm is able to cluster arbitrarily structured datasets. However, the result this exceptionally sensitive neighborhood radius (Eps) and points, it hard obtain best quickly accurately it. To solve above problems, we propose an adaptive DBSCAN method based on chameleon swarm (CSA-DBSCAN). First, take evaluation index DBSCNA as objective function use (CSA) iteratively optimize value Eps result. Then, introduce theory...

We propose a photonic scheme to generate binary phase-coded microwave pulses and dual-chirp waveforms without baseband-modulated signals (background noise) based on dual-polarization dual-drive Mach-Zehnder modulator (DP-DDMZM) which contains x-DDMZM y-DDMZM at two different polarization states. A radio frequency (RF) signal from source is transferred into differential RF employed one arm of y-DDMZM, while baseband an arbitrary waveform generator divided by electronic coupler then driven the...

Frequency estimation of microwave signals is a crucial functionality for applications ranging from biomedical engineering to electronic warfare systems. Photonics-based frequency measurement systems offer advantages flexible reconfigurability and wide bandwidth compard methods. However, photonic based are limited by trade-offs between range accuracy. Here, we propose experimentally demonstrate identification system with ultrahigh accuracy 900 kHz, large 39 GHz, the capability multiple...

We report a method to significantly improve the accuracy of an optical vector network analyzer (OVNA) with double-sideband (DSB) modulation. The measurement errors DSB-OVNA mainly derive from carrier uncertainty and beating between higher order sidebands. propose three-step accuracy-enhanced algorithm eliminate these perfectly. A theoretical model is built analyze potential as well find way remove them. Excellent improvement OVNA confirmed by proof-of-concept experiment. shows ultrahigh...

We propose and experimentally demonstrate a microwave frequency measurement system based on the photonic technique. An amplitude comparison function is constructed to perform frequency-to-power mapping non-sliced broadband optical source. The results are fed into machine learning module which can be utilized minimize differential mode noise of caused by polarization fluctuation. reconfigurable with adjustable bandwidth adjusting dispersion group delay signals at orthogonal polarizations...

We propose a novel single-notch microwave photonic filter (MPF) using nonsliced amplified spontaneous emission (ASE) source and laser diode (LD). The ASE is used for implementation of phase tunable bandpass MPF, where the participation an LD enables simultaneous realization allpass without adding more devices into system. By destructive interfering between MPF can be achieved with center frequency. Compared previous approach based on source, proposed has broader frequency range much simpler...

We propose a photonic mixer with image rejection capability using broadband optical source (BOS) and polarization processing. Intermediate frequency (IF) signals are generated from the local oscillator-modulated time-delayed radio (RF)-modulated BOS light. The RF operating is flexibly tunable over wide range by simply adjusting time delay. In addition, proposed system free dispersion-induced mixing power fading bias drift problem. Experimental results exhibit an ratio of more than 44.6 dB...

We propose a photonic approach to generating frequency-doubled triangular waveforms using dual-parallel Mach–Zehnder modulator (DPMZM). Most previous modulator-based schemes require additional processing of optical sidebands filters or dispersive element. In our work, components is no longer necessary. The with repetition rate twice the frequency applied microwave signal can be directly generated by properly setting bias and driven DPMZM. Since there processing, proposed structure cost...

In order to quantitatively evaluate the geomaterial surface characteristics, roughness was divided into two kinds according texture scale: micro-roughness at a micrometre or millimetre level and macro-roughness centimetre decimetre level. The definition of given. Four evaluation methods, digital survey method, contour line elongation elements average height method projected area ratio platform slope were put forward regular steps, inclined plane different gradients curved surfaces. Through...

We present a method to realize single-notch microwave photonic filter (MPF) based on interferometry of single, low-coherence broadband optical source (BOS). Normally, notch MPF requires independent control two sources located in different wavebands. In this work, we use single BOS accurately perform destructive interference between bandpass and an all-pass MPF. A frequency bandwidth freely tunable can thus be realized. The proposed is theoretically analyzed experimentally demonstrated. depth...

With the improvement of information transmission rate and progress semiconductor process technology, Lithium Niobite on insulator (LNOI) electro-optic modulators have received more attention. The LNOI high linearity extinction ratio that silicon-based do not reach, so it can be used to support high-speed long-distance optical communication. In modulator, traveling wave electrodes with coplanar waveguides (CPWs) structure are used. We mainly consider impedance matching microwave transmission,...

In this letter, we propose and demonstrate a phase stabilization approach to distribute radio frequency (RF) signal from remote antenna local station based on passive post correction. Simplified structure makes our scheme cost-effective easy implement. The key advantage of method is that only one-stage mixing used, which indicates simpler operation less conversion loss. A proof-of-concept experiment verifies the drift effectively compressed using proposed compared free-running situation.