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Xplore Articles related to Vhf Devices

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Miniature superconducting coplanar strip antennas for microwave and MM-wave applications

1995 Ninth International Conference on Antennas and Propagation, ICAP '95 (Conf. Publ. No. 407), 1995

Miniaturization of components in wireless communications is constrained by the inefficiency of the antenna element and its feeding-matching circuitry and the high Q-factors associated with electrically small antenna systems. High temperature superconductors (HTS) permit miniaturization by reduction of dissipation. This paper discusses the use of HTS in a new class of coplanar radiating structures, with superior gain and bandwidth performance ...


Bandwidth investigation of coaxial colinear antennas

1995 Ninth International Conference on Antennas and Propagation, ICAP '95 (Conf. Publ. No. 407), 1995

Coaxial colinear (CoCo) antennas were considered, for decades, just as being wire antennas. However, the concept of the colinear phased array has been introduced by a number of authors. The principle of dual behaviour (transmission line-cylindrical antenna) allowed a better comprehension of these antennas. We give practical results based both on experimentation and simulation. We first show the technique of ...


A high performance ultra-broadband RF choke for microwave applications

IEE Colloquium on Evolving Technologies for Small Earth Station Hardware, 1995

The authors consider the design of chokes and their performance. They present the design and test of an ultra-broadband choke. Measurements show that this choke is usable upto about 20 GHz. As it is cheap, compact and easy to use it is suitable for satellite and mobile communication applications.<>


Ultrasonic micromanipulation of small particles in liquid using VHF-range leaky wave transducers

1994 Proceedings of IEEE Ultrasonics Symposium, 1994

New ultrasonic micromanipulation techniques for small particles based on the radiation forces of high-frequency ultrasound are proposed, using VHF-range leaky wave transducers. A newly developed leaky wave transducer with beamwidth compression consists of a floating-electrode-type unidirectional interdigital transducer and a LiNbO3 substrate. It has many advantages: no impedance matching scheme between liquid and substrate, efficient generation of higher- frequency ultrasonic ...


Design Formulas for a Meandered Dipole

IEEE Antennas and Propagation Magazine, 2011

The design equations for a reduced-size antenna that uses the traditional meandered geometry are established in this communication. The results were found through parametric analysis using NEC-2 and a second-order polynomial approximation of its results.


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Educational Resources on Vhf Devices

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IEEE-USA E-Books

  • Miniature superconducting coplanar strip antennas for microwave and MM-wave applications

    Miniaturization of components in wireless communications is constrained by the inefficiency of the antenna element and its feeding-matching circuitry and the high Q-factors associated with electrically small antenna systems. High temperature superconductors (HTS) permit miniaturization by reduction of dissipation. This paper discusses the use of HTS in a new class of coplanar radiating structures, with superior gain and bandwidth performance and potential applications as miniature antennas at VHF-UHF and elements in monolithic MM-wave phased arrays. A hybrid technique that combines transmission line theory and spectral domain method of moments (MM) is also briefly discussed and employed in the analysis of linear arrays of folded dipoles.<>

  • Bandwidth investigation of coaxial colinear antennas

    Coaxial colinear (CoCo) antennas were considered, for decades, just as being wire antennas. However, the concept of the colinear phased array has been introduced by a number of authors. The principle of dual behaviour (transmission line-cylindrical antenna) allowed a better comprehension of these antennas. We give practical results based both on experimentation and simulation. We first show the technique of impedance calculation (which is the basis of bandwidth evaluation). This depends on frequency, array size, and on the physical parameters of the cables. Finally, we investigate the case of CoCo antennas made of elements with different lengths.<>

  • A high performance ultra-broadband RF choke for microwave applications

    The authors consider the design of chokes and their performance. They present the design and test of an ultra-broadband choke. Measurements show that this choke is usable upto about 20 GHz. As it is cheap, compact and easy to use it is suitable for satellite and mobile communication applications.<>

  • Ultrasonic micromanipulation of small particles in liquid using VHF-range leaky wave transducers

    New ultrasonic micromanipulation techniques for small particles based on the radiation forces of high-frequency ultrasound are proposed, using VHF-range leaky wave transducers. A newly developed leaky wave transducer with beamwidth compression consists of a floating-electrode-type unidirectional interdigital transducer and a LiNbO3 substrate. It has many advantages: no impedance matching scheme between liquid and substrate, efficient generation of higher- frequency ultrasonic waves into a small-scale liquid system, and isolation of interdigital electrodes from liquid. The experimental leaky wave transducer with narrow beam width of 120-&mu;m shows a conversion loss of 5.8 dB at 97.5 MHz. Transportation and trapping of 50-&mu;m-diameter glass spheres in water are confined by preliminary experiments in the frequency range of 50 to 100 MHz

  • Design Formulas for a Meandered Dipole

    The design equations for a reduced-size antenna that uses the traditional meandered geometry are established in this communication. The results were found through parametric analysis using NEC-2 and a second-order polynomial approximation of its results.

  • Angular Sensitivity of VHF-Band CNT Antenna

    A carbon nanotube (CNT)-based antenna detects incoming electromagnetic waves based on electrically induced mechanical vibration. In this study, we perform an analysis of the angular sensitivity of a CNT-based antenna. To analyze the mechanical vibration, we introduce a simple model using the image charge method. The analysis shows that the angular sensitivity depends on |sin2θ|, where θ is the angle of arrival. This is clearly different from the traditional Hertzian dipole detector, whose sensitivity varies with |sinθ|. In addition, the full width at half maximum of the angular sensitivity distribution for the CNT-based antenna is 0.36 π, which is smaller than the value of 0.5 π for a Hertzian dipole detector.

  • Principle of rear windscreen car antenna

    The heated rear windscreen car antenna is being increasingly used for reception purposes, as a means of avoiding the mechanical problems which may arise with rod antennas. The objective in its design is not, however, to find an optimum geometric shape for printing on the rear windscreen, but rather to use the existing heater-demister as an antenna. Two problems arise in such a design. One is the matching problem over the wide frequency range from long waves to VHF, and the other is the electromagnetic solution to the geometry of the heater-demister.<>

  • Mathematical modelling of work regimes of cathode with net clusters in multi-beam klystrode

    In the given activity the interface of the program of calculation of electron guns with fine-mesh control grids used in a VHF devices with net control is described. The results of calculation electron gun for multi-beam klystrode are given.

  • Computer-aided panoramic vector analyzer based on a P2-60...P2-69 series meter

    The description of the design principles of computer-aided panoramic vector- analyzer based on the standard P2-60...P2-69 series meter and PC is given. The basic metrological characteristics are presented.

  • A 5 kHz channelling VHF linear modulation receiver for volume production

    Increased demand for spectrum has led the regulatory authorities to encourage the adoption of voice and data systems using 5 kHz channelling. In the USA, 200 duplex channels in the 220 to 222 MHz band released by the FCC are now in use. In the UK, a regulatory specification is published by the Radiocommunications Agency and trials have been carried out in the 70 MHz, 160 MHz and 220 MHz bands. Manufacturers are now using digital signal processing (DSP) in low-cost, flexible mobile transceivers. DSP is applicable both for linear receivers and for transmitters such as those using a Cartesian loop. Private Mobile Radio (PMR) equipment operating with 5 kHz channelling is now manufactured in volume and provides both excellent analogue voice quality and 14.4 kb/s digital capability for data or digital voice applications in both static and fading environments.



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