40,638 research outputs found

    Matched wideband low-noise amplifiers for radio astronomy

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    Two packaged low noise amplifiers for the 0.3–4 GHz frequency range are described. The amplifiers can be operated at temperatures of 300–4 K and achieve noise temperatures in the 5 K range (<0.1 dB noise figure) at 15 K physical temperature. One amplifier utilizes commercially available, plastic-packaged SiGe transistors for first and second stages; the second amplifier is identical except it utilizes an experimental chip transistor as the first stage. Both amplifiers use resistive feedback to provide input reflection coefficient S11<−10 dB over a decade bandwidth with gain over 30 dB. The amplifiers can be used as rf amplifiers in very low noise radio astronomy systems or as i.f. amplifiers following superconducting mixers operating in the millimeter and submillimeter frequency range

    The Use of Cryogenic HEMT Amplifiers in Wide Band Radiometers

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    Advances in device fabrication, modelling and design techniques have made wide band, low noise cryogenic amplifiers available at frequencies up to 106 GHz. Microwave radiometry applications as used in radio astronomy capitalize on the low noise and large bandwidths of these amplifiers. Radiometers must be carefully designed so as to preclude sensitivity degradations caused by small, low frequency gain fluctuations inherent in these amplifiers

    Isosceles detector provides maximum resolution in expanded range

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    Dynamic range expansion system for radio frequency /RF/ signal detection equipment consists of RF amplifiers, RF amplitude modulated detectors, and operational amplifier. The analog output gives maximum resolution over fixed voltage range, without switching. Two minor drawbacks of this circuit are cited

    Radio Frequency Solid State Amplifiers

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    Solid state amplifiers are being increasingly used instead of electronic vacuum tubes to feed accelerating cavities with radio frequency power in the 100 kW range. Power is obtained from the combination of hundreds of transistor amplifier modules. This paper summarizes a one hour lecture on solid state amplifiers for accelerator applications.Comment: 20 pages, contribution to the 2014 CAS - CERN Accelerator School: Power Converters, Baden, Switzerland, 7-14 May 201

    Power density measurements in the near field of the DSS 13 26-meter antenna

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    Power density measurements were made at Deep Space Station (DSS) 13 in the near field of the 26-m antenna to determine if radio frequency (rf) fields generated by the 20-kW transmitters could be responsible for the failure of three solid state rf amplifiers. These amplifiers are used in the Search for Extraterrestrial Intelligence (SETI) Radio Spectrum Surveillance System, which is currently located at the site. Measurements were made independently for one transmitter at 7150 MHz, and both transmitters together. Measurement results are tabulated and compared with predicted power densities under the measurement conditions. The results agree with the predictions within a factor of two. The predictions appear to give worst case values. Measurements indicated that amplifier failures are not attributable to the transmitter

    Tunable, Concurrent Multiband, Single Chain Radio Architecture for Low Energy 5G-RANs

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    This invited paper considers a key next step in the design of radio architectures aimed at supporting low energy consumption in 5G heterogeneous radio access networks. State-of-the-art mobile radios usually require one RF transceiver per standard, each working separately at any given time. Software defined radios, while spanning a wide range of standards and frequency bands, also work separately at any specific time. In 5G radio access networks, where continuous, multiband connectivity is envisaged, this conventional radio architecture results in high network power consumption. In this paper, we propose the novel concept of a concurrent multiband frequency-agile radio (CM-FARAD) architecture, which simultaneously supports multiple standards and frequency bands using a single, tunable transceiver. We discuss the subsystem radio design approaches for enabling the CM-FARAD architecture, including antennas, power amplifiers, low noise amplifiers and analogue to digital converters. A working prototype of a dual-band CM-FARAD test-bed is also presented together with measured salient performance characteristics

    Adaptive Biasing Of Radio-Frequency Power Amplifiers

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    Radio-frequency (RF) power amplifiers (PA) have a nearly linear response only at small input amplitudes, with their outputs gradually saturating as input amplitudes increase. This slightly sub-linear transfer characteristic gives rise to out-of-band emissions, which can potentially interfere with other users of the RF spectrum. Regulatory requirements place limits on the maximum out-of-band emissions by a device. In turn, these translate to operating the PA at a highly linear region, e.g., at low input amplitudes compared to the dynamic range of the PA. However, low input amplitudes are associated with low PA efficiencies. This disclosure describes techniques to adapt the operating point of the PA to suit the targeted output power and/or bandwidth. By doing so, the emissions mask is met even as the PA operates at its worst conditions, and energy efficiencies are achieved when the device is operating at its most efficient conditions. The techniques reduce current drain and heat dissipation, and improve battery life

    A Solid State VHF Single Sideband Transmitter

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    This research report investigates a unique method of generating single sideband power, which is particularly useful in transistorized transmitters operating at VHF frequencies. Radio frequency power id developed by class C amplifiers, rather than conventional class A or B amplifiers. Currently, VHF power transistors are not well adapted for use as linear amplifiers, and will function far better in the class C mode. A prototype VHF transmitter which develops single sideband power with nonlinear amplifiers was designed and constructed. The transmitter characteristics were measured and analyzed to establish the feasibility of the new design
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