DOI:10.1049/ree.1983.0055

出版商:IERE    

年代:1983

数据来源: IET

DOI:10.1049/ree.1983.0056

出版商:IERE    

年代:1983

数据来源: IET

摘要:

The principles and techniques for preparing and using photochromic waveguide passive components for fibre optics are described. The sandwiched layer is considered to have a robust format in which fibre-to-waveguide alignment is fairly easy and reliable.

DOI:10.1049/ree.1983.0058

出版商:IERE    

年代:1983

数据来源: IET

摘要:

The technique of Time-Encoded Speech (TES) has shown considerable promise in transmitting good quality speech at bit rates below 16 kb/s. The central concept of this approach depends upon the transmission of coded shape descriptors for successive extended segments of the speech waveform. For transmission over a constant rate data channel, buffer management via a first-in first-out store is required. A modified time encoding method for speech signals which is basically a kind of extremal coding is described. This technique enables the low frequencies of speech waveform to be reconstructed more faithfully, and this is desirable for human perception. With linear encoding and transmission rate at about 12–16 kb/s, the TES output speech quality approaches that of public telephone quality, and little improvement can be gained by further increase in the data rate.

DOI:10.1049/ree.1983.0059

出版商:IERE    

年代:1983

数据来源: IET

摘要:

Coloured noise signals with pseudo-Gaussian distribution very closely approximate the operating efficiency characteristics of typical broadcast programming and therefore are the preferred test source when measuring overall transmitter power consumption and efficiency. More accurate comparison of different manufacturers' transmitter efficiency can be made when noise modulation data are utilized.To date, no standard procedure exists to measure a transmitter's linearity at 125% positive modulation. Two test signals are proposed to accomplish such a test.

DOI:10.1049/ree.1983.0060

出版商:IERE    

年代:1983

数据来源: IET

摘要:

Ruze and Rotman lenses are devices which can be used to form multiple beams for antenna arrays. A previous paper has shown these lenses can be designed for low-phase aberrations and minimum size. Published work on these lenses has concentrated on phase and largely neglected amplitude performance (except Maybell). Here, a theoretical model is developed which predicts the primary amplitude distribution across the array ports of the lens; this then allows predictions of insertion loss and sidelobe levels of the fed array.An experimental waveguide-fed parallel-plate lens has constructed, and amplitude and phase performance measured. Comparison with the theoretical predictions shows good agreement. The multiple beam radiation patterns produced by a 16-element array fed by this lens have also been measured. The lens has a low insertion loss (−2 dB) and provides a low sidelobe level (−20 dB) for the 8–12 GHz band.

DOI:10.1049/ree.1983.0061

出版商:IERE    

年代:1983

数据来源: IET