Required Frequency Stability Research Articles

Development of Novel Piezoelectric Biosensor Using PZT Ceramic Resonator for Detection of Cancer Markers.

A novel biosensor based on piezoelectric ceramic resonator was developed for direct detection of cancer markers in the study. For the first time, a commercially available PZT ceramic resonator with high resonance frequency was utilized as transducer for a piezoelectric biosensor. A dual ceramic resonators scheme was designed wherein two ceramic resonators were connected in parallel: one resonator was used as the sensing unit and the other as the control unit. This arrangement minimizes environmental influences including temperature fluctuation, while achieving the required frequency stability for biosensing applications. The detection of the cancer markers Prostate Specific Antigen (PSA) and α-Fetoprotein (AFP) was carried out through frequency change measurement. The device showed high sensitivity (0.25ng/ml) and fast detection (within 30min) with small samples (1μl), which is compatible with the requirements of clinical measurements. The results also showed that the ceramic resonator-based piezoelectric biosensor platform could be utilized with different chemical interfaces, and had the potential to be further developed into biosensor arrays with different specificities for simultaneous detection of multiple analytes.

Robust PI Controller for Frequency Stabilisation of Islanded Microgrid Operation using Battery Energy Storage System

Background/Objectives: Maintaining constant frequency in an Islanded microgrid is highly demanding and challenging issue. Therefore it is proposed to use Robust PI Controller for controlling the frequency of islanded microgrid using Energy Storage system. Methods/Statistical Analysis: The proposed Robust PI controller provides the required frequency stability to the islanded microgrid. The test modeled in MATLAB Simulink environment. The Test system modeled as typical remote location (Island or Military Power Grid or Geographically Disconnected or Hilly Terrain) with a wind turbine and Solar panel, along with distributed loads and Energy storage system. Findings: The drawbacks of the traditional PI controller to adapt to the parametric variations and to provide faster response is overcome using proposed Robust PI controller. The inherent disadvantage of PID controller such as instability and peak overshoot is also overcome with the proposed controller. The Proposed Robust PI controller provides the improved dynamic frequency stability and reduced peak overshoot to the islanded microgrid with in 0.3seconds, if the microgrid is suddenly disconnected from the main grid. The controller also tested under various conditions and it provides required frequency stability to test system during islanding operation. The proposed method is simple, flexible and provides improved performance as compared to the existing methods and approaches for frequency stability of islanded microgrid. Application/Improvements: The proposed controller can be used in remote location and provides simple, yet cost effective solution as compared to costlier PID Controller based on fuzzy logic and neural network.

Effect of master oscillator stability over pulse repetition frequency on hybrid semiconductor mode-locked laser

Semiconductor mode-locked lasers are a very attractive laser pulse source for high accuracy length metrology. However, for some applications, this kind of device does not have the required frequency stability. Operating the laser in hybrid mode will increase the laser pulse repetition frequency (PRF) stability. In this study it is showed that the laser PRF is not only locked to the master oscillator but also maintains the same level of stability of the master oscillator.The device used in this work is a 10 mm long mode-locked asymmetrical cladding single section InAs/InP quantum dash diode laser emitting at 1580 nm with a pulse repetition frequency of ≈4.37 GHz. The laser nominal stability in passive mode (no external oscillator) shows direct dependence with the gain current and the stability range goes from 10−4 to 10−7. Several oscillators with different stabilities were used for the hybrid-mode operation (with external oscillator) and the resulting mode-locked laser stability compared. For low cost oscillators with low stability, the laser PRF stability achieves a value of 10−7 and for higher stable oscillation source (such as oven controlled quartz oscillators (OXCO)) the stability can reach values up to 10−12 s).

Detection of cancer biomarkers by piezoelectric biosensor using PZT ceramic resonator as the transducer

A novel piezoelectric biosensor using lead titanate zirconate (PZT) ceramic resonator as transducer was developed for label-free, cost-effective, and direct detection of cancer biomarkers. We designed a dual sensing scheme where two ceramic resonators were connected in parallel, in which one resonator was used as the sensing unit and the other as the control unit, in order to minimize environment influences including temperature fluctuation and to achieve the required frequency stability for biosensing applications. Detection of selected cancer biomarkers, such as prostate specific antigen (PSA) and α-fetoprotein (AFP) was carried out to evaluate the performance of the biosensor. The device showed high sensitivity (0.25ng/ml) and fast detection (within 30min) with small amount of sample (1μl), which is compatible to that required by clinical measurements. The results also showed that the ceramic resonator-based piezoelectric biosensor platform could be utilized with different chemical interfaces, and the miniaturized size of the ceramic resonators makes it suitable for fabricating sensor arrays for multiplex detection.

Measuring the photodetector frequency response for ultrasonic applications by a heterodyne system with difference- frequency servo control

A technique for the calibration of photodiodes in ultrasonic measurement systems using standard and cost-effective optical and electronic components is presented. A heterodyne system was realized using two commercially available distributed feedback lasers, and the required frequency stability and resolution were ensured by a difference-frequency servo control scheme. The frequency-sensitive element generating the error signal for the servo loop comprised a delay-line discriminator constructed from electronic elements. Measurements were carried out at up to 450 MHz, and the uncertainties of about 5% (k = 2) can be further reduced by improved radio frequency power measurement without losing the feature of using only simple elements. The technique initially dedicated to the determination of the frequency response of photodetectors applied in ultrasonic applications can be transferred to other application fields of optical measurements.

Polarization diversity detection performance of 2.4 Gbit/s CPFSK heterodyne system

AbstractIn the practical implementation of the coherent optical transmission system, it is important to establish the techniques for stabilizing the optical frequency considering the actual environmental condition, as well as a technique for compensating for the variation of the state of polarization in the usual single‐mode optical fiber cable.This paper considers the application of the polarization diversity receiver to the CPFSK heterodyne delay detection in the 2.4‐Gbil/s band and discusses the construction and performance. The regenerative repeater equipment is designed in a compact form to be implemented in a commercial rack (INS cabinet rack). Using the designed equipment and the existing trunk fiber transmission route, an experiment in the actual site is conducted and the results are shown.The first part of this paper presents the construction of both the automatic frequency control (AFC) system and the automatic gain control (AGC) system suited to the polarization diversity system. The design guides are presented for the required frequency response speeds of AFC and AGC, the required frequency stability of AFC, and the response performance to the fluctuation of polarization. A high‐output, high‐sensitivity 2.4‐Gbit/s regenerative repeater equipment (with repeater gain above 48 dB) is realized with the overall performance that the variation of optical received sensitivity against the polarization fluctuation can be suppressed to within 0.5 dB.Finally, the stable operation of the equipment is verified by the experiment at the actual site, and the practical usefulness is indicates.

FM Terminal Transmitter and Receiver For the TH Radio System

The FM terminals form an important subsystem of TH radio, as the link between the 0.10 mc baseband signal and the 74.1-MC FM signal. Severe requirements arise from the design objective of 16 terminal pairs in tandem in 4000 miles. The FM transmitter design uses a 6-kmc reflex klystron as a frequency modulator, the output of which is heterodyned down to 74 mc by another 6-kmc source. Automatic frequency control, with a 74.13-MC crystal oscillator as reference, provides the required frequency stability. In the FM receiver, an IF amplifier-limiter is followed by a balanced FM discriminator which uses parallel resonant discriminator networks. Improved linearity is obtained by special design of a common interstage network. The video amplifiers are balanced and use high-performance electron tubes. The over-all gain of a terminal pair is 8 db, between 124-ohm balanced video circuits.