Output Power Capability Research Articles

Methods For Improving Shipboard Waveguide Installations

ABSTRACTMany dollars are expended by the Navy to increase output power and range capabilities of search and fire control radar systems. The same results can be achieved to some extent by improving shipboard waveguide installation procedures, thereby reducing power losses in runs. To this end, for every db of power loss eliminated, a pay off of approximately 10% increase in range capability can be expected. One convenient way to eliminate waveguide power loss is to apply half wavelength phasing concepts to all bends and twists. This paper describes a half wavelength phasing technique in addition to other power saving installation practices which are usually overlooked by installing activities.

The utilization of subjective probabilities in production planning

The Central Electricity Generating Board in England and Wales is a highly integrated organization employing 80,000 people in some 240 power stations outputting about 48,000 MW of power (at maximum demand) into the National Grid supplying power to each demand area. The industry is capitalized at about £2,000 million and is organized into five regions of which the Midlands Region has a capital investment level of some £600 million in about 32 power stations. Because the CEGB is charged with providing a ‘secure’ service and because the complex equipment requires lengthy planned overhauls (not withstanding unplanned but shorter breakdowns) the incidence of overhauls across the UK must be carefully organized so that enough power output capability exists in any part of the country at any time to supply the national demand via the grid system (see text books on the problems of alternating current flows in large systems). This paper describes how the subjective probabilities of overhaul completion gleaned from workers in each power station, are combined in the Midlands Region Information Centre. These results are utilized by Management in the form of a prediction of the expected capabilities of the level of power generation over a possible horizon of 30 weeks. The conceptual background to the centre is discussed together with the mode of implementation. Finally the nature and the consistency of subjective reporting is reviewed.

Symmetry Correction for a Free-Running Transistor Inverter

Inverters and converters with large power output capabilities are presently being operated at frequencies above the audible band. The advantages of reduction in size and the elimination of audible noise have given designers the incentive to increase the frequency of operation of inverters and converters to the limit of the capabilities of available power transistors.

Some limitations of the power output capability of VHF transistors

The power output capability of a VHF transistor is often limited by the RF saturation resistance. The resistance is set up by the constriction of the emitter current to the geometric edges of the device. The contributions of large current densities and high frequencies to current crowding are discussed in this paper. An extension of this discussion leads to an interpretation of the first-order effects for large-signal high-frequency operation. The RF saturation resistance was measured under large-signal conditions and was found to increase by a factor of 2 over a frequency range of 40-200 MHz. This variation was compared to results obtained by a large-dc small-signal analysis. The resulting deviation was less than 20 percent.

High-performance experimental power triodes

The plate current, transconductance, gain-bandwidth product, and power output capabilities of small planar triodes have been increased nearly tenfold over that obtained from present day commercial tubes of comparable size and weight. In the new experimental triodes, the cathode can supply a CW current density of 1.6 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . A closely spaced, rigidly supported grid structure can provide a transconductance of 0.7 mho. The output capacitance is low enough to render a gain-bandwidth product of 22 Gc/s at 1.3 Gc/s. In this frequency range, the CW power output capability is 1 kW, and the pulsed power output capability in a 10-percent bandwidth circuit is 5 kW with 500 μs pulses at a duty factor of 0.07.

Current-Pumped Abrupt-Junction Varactor Power-Frequency Converters

This paper presents equations and design curves for a noninverting frequency converter which will enable the engineer to design efficient, high-level parametric devices using abrupt-junction varactors. In addition, the excellent intermodulation characteristic and extremely wide dynamic range (in excess of 140 dB) of the parametric frequency converters enables their use immediately as low-frequency downconverters or microwave upconverters without any deterioration of other parameters, such as noise figure, in system performance. It has been shown that these abrupt-junction diode devices possess the largest known dynamic range, in addition to being relatively spuria free with respect to intermodulation products produced by the diode nonlinearity, intermodulation distortion being generated in the device due only to gain saturation. The design curves also indicate the maximum conversion efficiency possible with a given abrupt-junction diode. An inflection point for 50 per cent converison efficiency occurs for all diodes. Any additional improvement in pump-to-sideband efficiency greater than 50 per cent gained by adjusting the diode and circuit performance, requires relatively large increases in the diode cutoff frequency and reduction in overall circuit losses. Other design curves include impedance variation with drive powers and the overall limiting output power capability for a given diode. A design example is presented to demonstrate the usefulness of the derived results and design curves. The experimental results obtained with this design have demonstrated a microwave, C band, tunable converter with almost 50 per cent conversion efficiency.

Factors affecting traveling-wave tube power capacity

In some of the early traveling-wave tubes relatively high efficiencies and powers were observed. As more tubes were made, however, these results were not repeated and it became apparent that extremely wide variations in operation were obtained between tubes, with no obvious correspondence to observed structural variations. As a result an experimental program was undertaken to determine those parameters which are important to power output and efficiency, using a demountable continuously pumped tube and a probe technique for measuring the field strength along the length of the helix. As a result of this work it has been concluded that the amount and distribution of attenuation on the circuit has an important effect on the power output capabilities of the tube, and in fact that there is a relatively small latitude of attenuation distribution which will allow the maximum power output to be obtained and still give a good margin against oscillations. On a basis of these measurements empirical design criteria have been developed which specify attenuation distributions resulting in a minimum length of active circuit and a minimum net gain consistent with maximum efficiency. Application of the principles given has resulted in an increase in beam efficiency from 2% to 11% for a 4000 cm traveling-wave tube. By collecting electrons at a low voltage and increasing the total current, an overall “plate” efficiency of about 20% and 8 watts output has been obtained. One would expect that efficiency would be a function of the gain parameter (C), space charge (QC), attenuation (L/C) and the beam radius (γa'). This work is incomplete in that the effect of the last factor has been ignored. It does however give rough empirical relationships between the other factors for certain conditions, which have proven to be sound guides in the practical design of traveling-wave power tubes.