New modulation techniques for increased efficiency in UHF-TV transmitters
The use of electron-beam modulation in klystron amplifiers is an important means of reducing the electrical power consumption of ultra-high-frequency power amplifiers, employed in the transmission of television signals. This paper explores the characteristics of the amplifiers, describes the methods developed for applying video modulation, and gives details of typical power savings which can be expected.
13 – Television Transmitters
Publisher Summary 
This chapter discusses television transmitters. There are two basic types of television transmitter, one using combined and the other separate vision and sound amplification. In the first, modulated vision and sound signals are combined at low level and amplified together by a single amplifier chain. In the second, vision and sound are amplified separately and combined at high level. Combined amplification has the advantage that, as only one amplifier is used; the transmitter is simpler, smaller and less expensive. A modulator introduces precorrections adjusted to be equal and opposite to those encountered in subsequent stages to maintain the transmitter output within close specification limits. By enabling the use of a larger part of the power amplifier's transfer characteristic, transmitter efficiency is increased significantly. The up-converter contains two identical chains. Each comprises a double balanced mixer, an amplifier, a channel filter, and a further amplifier. These convert the outputs of the modulator to the radiated carrier frequencies. The local oscillator signal is generated by a synthesizer or a temperature stabilized crystal oscillator with multiplier and filter. It is split to feed both mixers. In subcarrier systems, the composite baseband signal is generated by a coder that is usually a part of the program input equipment. Provided that the sound channel has adequate deviation and bandwidth, multi-channel/stereo sound has little effect on the design of a transmitter.
Investigation of scatter radiation of non-circular X-ray scan trajectories
Modern interventional X-ray devices are highly maneuverable and allow complex 3D imaging trajectories. New scan trajectories enable not only optimized object sampling but also introduce new approaches for dynamic 3D imaging. In this paper, we investigated the scatter radiation of two different scan trajectories. The scatter radiation was sampled by a rail setup with dosimeters at defined positions. After data analysis, contour maps were generated which show for four exemplary heights the scatter radiation distribution. The alternative scan trajectory showed smaller dose exposures at heights correlated to upper torso and head areas of a model physician. Keywords—Image acquisition, alternative scan trajectory, circular tomosynthesis, scatter radiation distribution