DOI:10.1049/ree.1979.0065

出版商:IERE    

年代:1979

数据来源: IET

摘要:

Increased interest in the millimetre and submillimetre wavelength regions during the past decade has stimulated the development of sensitive heterodyne receivers for a wide range of applications. The GaAs Schottky-barrier diode has received the most attention as a mixer in this wavelength range as a result of its sensitivity, reliability, mechanical stability and wide bandwidth and its ability to operate at room temperature. The concepts of receiver design and the particular problems associated with this region of the frequency spectrum are discussed. The optimization of material parameters and the device topology for low-noise operation are considered. The extension of fundamental waveguide mixers into the submillimetre region and the development of various types of quasi-optical receivers are reviewed. The development of integrated monolithic receivers in which antenna, coupling structure, mixer diode and intermediatefrequency filter network are fabricated on the GaAs surface offers the possibility of increased reliability, repeatable and improved performance, and the potential economy associated with integrated circuit technology. In addition, the possibility of monolithic receiver arrays provides the systems designer with a capability that was not previously attainable using discrete diode receivers. This newly emerging technology is reviewed and the potential impact on the 100-1000 GHz region is discussed.

DOI:10.1049/ree.1979.0066

出版商:IERE    

年代:1979

数据来源: IET

摘要:

The paper presents a review of the present capabilities of solid-state ‘avalanche-diodes’ at frequencies between 90 and 400 GHz.Applications of solid-state sources are given with information on the relationship of reliability and performance.The diode design and fabrication details are described briefly, and present-day laboratory capabilities are outlined and compared with those of commercially available sources.

DOI:10.1049/ree.1979.0067

出版商:IERE    

年代:1979

数据来源: IET

摘要:

Until recently, the application of microwave systems has been hampered by the relatively large and expensive equipment, particularly in the millimetre and submillimetre-wave range. The development of more reliable and efficient solid-state sources up to the submillimetre-wave range has now stimulated new interest in commercial applications. Three different approaches can be distinguished, radar, radiometry and transmission measurement applications.The widest spread applications are found in radar systems for traffic control and industrial and scientific use. High resolution, high antenna gain and easy acquisition, even of non-metallic objects, in conjunction with contactfree or remote sensing, makes the millimetre-wave approach best suited for measurement purposes. Applications are the contactless measurement of velocity, distance and acceleration on rail vehicles, and radiometry in medicine and industry, e.g. for cancer diagnostics and atmospheric remote sensing.The behaviour of materials and gases can be examined, using the transmission measurement approach. Atmospheric pollution control and the non-destructive evaluation of solid materials are realizations of this technique.Employing millimetre- and submillimetre-wave frequencies for these applications gives inherent improvement of the measurement accuracy and due to the high transmission loss for this frequency range the risk of interference between different measurement systems is effectively reduced.

DOI:10.1049/ree.1979.0068

出版商:IERE    

年代:1979

数据来源: IET

摘要:

A number of radar systems are now being developed for operation in the 100–1000 GHz frequency range. A few special-purpose radars are already in limited use in this region. This paper is a survey of radars at short millimetric wavelengths. The new IEEE Standard definition of radar and IEEE Standard letter designations for radar bands are presented with a note on the transitional nature of this frequency region. Possible radar applications and principal advantages of short millimetric wavelength radar are given. Technical characteristics of a number of representative civilian and military radars are given. It is shown that the characteristics of some of these radars are similar, but characteristics of other radars vary considerably. A discussion of future trends and issues concludes this survey paper.

DOI:10.1049/ree.1979.0069

出版商:IERE    

年代:1979

数据来源: IET

摘要:

The influence of the atmosphere on propagation in the frequency range 100–1000 GHz is discussed in terms of molecular absorption, effects due to particles or droplets, and refractive effects. Compared with propagation at lower frequencies, molecular absorption shows a substantial increase in effect, mainly due to absorption by water vapour molecules and this aspect is given particular attention. Molecular absorption may be modelled using published line parameters, but attention must also be given to significant absorption caused by double molecules of water vapour (dimers), which at present are not included in the line tabulations. The total predicted absorption accounts for the main aspects of molecular absorption observed in the field, but at frequencies with minimum attenuation, away from the strong resonance absorption regions, field measurements have shown significant differences which are not understood. Refractive effects and the influence of particles, involving both absorption and scattering, can be modelled, but prediction is limited by the need for appropriate meteorological data which has a particular relevance to propagation in this frequency range. Comparison with prediction is made both for horizontal transmission paths and slant paths through the atmosphere.

DOI:10.1049/ree.1979.0070

出版商:IERE    

年代:1979

数据来源: IET

摘要:

Practical use has been made of frequencies above 30 GHz for the last 20 years in the UK National Radar Modelling Facility to investigate the characteristics of radar reflections from typical radar targets. This paper discusses the purposes, principles and methods of radar scale modelling. It also describes the several different types of measuring radar which are being used at frequencies up to 890 GHz to investigate various aspects of radar scattering. Some comments are made on methods of data reduction to simplify their use in the investigation of real radar problems. Possible future trends towards operation at frequencies up to 2 THz are indicated.

DOI:10.1049/ree.1979.0071

出版商:IERE    

年代:1979

数据来源: IET

摘要:

Waveguides used, or under consideration, for application at frequencies greater than 100 GHz include dominantmode and overmoded rectangular guides, circular low-loss mode guide, microstrip, H and groove guides, various dielectric guide configurations, suspended strip and fin lines, and quasi-optic guides. Most existing systems, such as receivers, operating in the 100–300 GHz range have utilized rectangular TE10guide, or some form of strip line operating in a rectangular guide system. Losses are high, and dimensions are very small, but the system length is short. Neither guide type has the potential for extension into the frequency range much above 300 GHz. A number of other guide types have some encouraging features, such as reasonably low loss, ease of construction or potential for component construction, but none is yet sufficiently advanced to demonstrate practicability to allow systems to give full exploitation to this part of the frequency spectrum.

DOI:10.1049/ree.1979.0072

出版商:IERE    

年代:1979

数据来源: IET

摘要:

This paper reviews the key applications areas for spaceborne systems operating in the 100–1000 GHz spectral range. The strong interaction between the atmosphere and e.m. radiation at these frequencies is discussed and its consequences in terms of applications stated. For radio astronomy the heavy absorption by the atmosphere forces space-borne telescopes to be employed and the primary radio astronomy objectives in this frequency range are reviewed. The presence of atmospheric molecular transitions at these wavelengths allows extensive atmospheric studies to be conducted especially by the limb-sounding of important trace gases in the upper atmosphere. The possible application of this frequency range to inter-satellite communication links is also described. A detailed account of the present development status of receiver hardware technology is given with special reference to the importance of heterodyne techniques for tuneable, high resolution high sensitivity receivers.

DOI:10.1049/ree.1979.0073

出版商:IERE    

年代:1979

数据来源: IET

摘要:

The exploration and exploitation of the submillimetre and millimetre wave regions of the electromagnetic spectrum have progressed steadily over the last twenty years. Sophisticated Fourier spectroradiometric instrumentation, matching in performance that of the conventional instruments developed for the infra-red and visible regions over the last century, has become commercially available. Frequency can now be determined in this region directly against the caesium frequency standard to about 1 part in 1010, and the problem of reliable power measurement is being slowly resolved. The electrical properties of many materials have now been measured in this ultra-high frequency region, and the techniques are being successfully exploited in measurements of atmospheric composition and applied to the important area of plasma diagnostics.

DOI:10.1049/ree.1979.0074

出版商:IERE    

年代:1979

数据来源: IET