Final Report A Study into the Theoretical Appraisal of the Highest Usable Frequencies

121 Pages·2003·1.1 MB·English

Final Report
A Study into the Theoretical Appraisal of the
Highest Usable Frequencies
Radiocommunications Agency Contract Reference AY 4329
J. R. Norbury, C. J. Gibbins and D. N. Matheson
Radio Communications Research Unit
Rutherford Appleton Laboratory
Chilton, Didcot
Oxfordshire OX11 0QX
Tel: [phone]
Fax: [phone]
May 2003
Theoretical Appraisal of the Highest Usable Frequencies .
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Theoretical Appraisal of the Highest Usable Frequencies .
Table of Contents
1 INTRODUCTION...............................................................................................................3
2 PROPAGATION IN THE MILLIMETRIC AND INFRA-RED WAVEBANDS.................4
2.1 GASEOUSATTENUATION...............................................................................................4
2.2 SPECIFICGASEOUSATTENUATION.................................................................................4
2.3 PATHATTENUATIONTHROUGH THE CLEARATMOSPHERE FROM SEALEVEL....................7
2.4 ZENITHATTENUATION FROM HIGHALTITUDES..............................................................10
2.5 ATTENUATION DUE TO RAINFALL..................................................................................14
2.5.1 Frequency Range up to 400 GHz...............................................................................15
2.5.2 Terrestrial Path Attenuation.....................................................................................16
2.5.3 Slant-Path Rain Attenuation .....................................................................................20
2.5.4 Frequency Range above 400 GHz .............................................................................23
2.6 ATTENUATION DUE TO CLOUDS AND FOG......................................................................28
2.7 SCINTILLATIONEFFECTS..............................................................................................36
3 STATUS OF TECHNOLOGY...........................................................................................42
3.1 INTRODUCTION............................................................................................................42
3.2 TRANSMITTERTECHNOLOGY........................................................................................43
3.2.1 Available Transmit Power........................................................................................44
3.2.2 Technology Potential................................................................................................45
3.2.3 Bandwidth...............................................................................................................45
3.2.4 Convenience............................................................................................................45
3.2.5 Frequency and Phase Characteristics........................................................................46
3.3 RECEIVERTECHNOLOGY..............................................................................................46
3.3.1 Amplifier Technology...............................................................................................47
3.3.2 Diode Mixer Technology..........................................................................................49
3.3.3 Superconducting Mixer Technology ..........................................................................49
3.3.4 Receiver Performance..............................................................................................50
3.3.5 LO Requirements.....................................................................................................50
3.3.6 Receiver Potential....................................................................................................51
3.3.7 Bandwidth...............................................................................................................51
3.3.8 Convenience............................................................................................................51
3.3.9 Other Receiver Technology.......................................................................................52
3.4 COST OF TECHNOLOGY.................................................................................................52
4 REVIEW OF THE HIGHEST FREQUENCY ABOVE 100 GHZ AT WHICH VARIOUS
COMMUNICATIONS SYSTEMS COULD OPERATE............................................................54
4.1 INTRODUCTION............................................................................................................54
4.2 ANTENNAS FOR MILLIMETRE AND SUBMILLIMETREWAVE SYSTEMS...............................54
4.3 RF POWERSUBSYSTEMS..............................................................................................56
4.4 SYSTEMEVALUATIONMETHODOLOGY .........................................................................56
4.5 SAFETYISSUES............................................................................................................57
4.6 DISCUSSION OF INDIVIDUALSYSTEMREQUIREMENTS AND RELATIVEPERFORMANCES....58
4.6.1 Fixed Service Applications, Point-to-Point (P-P) Links...............................................58
4.6.2 Broadband Fixed Wireless Access (BFWA) Systems...................................................63
4.6.3 High Density Application in the Fixed Satellite Service (HDFSS)................................65
4.6.4 Aeronautical Satellite Applications such as In-Flight Internet Access & High Quality
Video Streams......................................................................................................................68
4.6.5 Cellular Mobile - 4G and Beyond (data rates up to 100 mb/s).....................................69
4.6.6 Typical Nomadic Broadband WLAN System (data rates up to 1 Gb/s)..........................71
4.6.7 Wireless Gigabit Ethernet (indoor)............................................................................71
4.6.8 Personal Area Networks – e.g. Wearable Devices......................................................73
4.6.9 High Altitude Platforms Systems (HAPS)...................................................................74
4.6.10 General Comments on UWB and Systems Above 100 GHz......................................75
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Theoretical Appraisal of the Highest Usable Frequencies .
4.6.11 Home Entertainment and UWB Applications in Bands above 100 GHz....................76
4.6.12 Safety Aspects of Home Communications Systems..................................................76
4.6.13 Anti-collision Radar in Cars Using UWB Techniques.............................................77
4.6.14 Free Space Optical (FSO) Systems........................................................................79
4.6.15 Operational Issues with FSO Links.......................................................................80
4.6.16 Link Budget Calculations for FSO Systems............................................................81
4.6.17 Comparison of FSO and Millimetre Wave System Performance ..............................82
4.6.18 Other Applications for FSO Systems......................................................................83
5 CONCLUSIONS AND RECOMMENDATIONS...............................................................84
5.1 CONCLUSIONS..............................................................................................................84
5.2 RECOMMENDATIONS FOR FURTHERSTUDIES.................................................................85
6 REFERENCES ..................................................................................................................87
ANNEX 1...................................................................................................................................91
SOURCES OF CONTINUOUS WAVE POWER.......................................................................91
A1.1 FREQUENCY MULTIPLICATION.................................................................................91
A1.1.1 PLANAR VARACTOR/VARISTOR DIODE MULTIPLIERS......................................................92
A1.1.2 HBV DIODE MULTIPLIERS.............................................................................................93
A1.2 VACUUM ELECTRON DEVICES...................................................................................94
A1.2.1 KLYSTRONS................................................................................................................95
A1.2.2 BACKWARDWAVEOSCILLATORS................................................................................95
A1.2.3 GYROTRONS...............................................................................................................97
A1.3 SOLID STATE OSCILLATORS- NON LASER..............................................................97
A1.3.1 GUNNDIODES.............................................................................................................98
A1.3.2 IMPATT OSCILLATORS.............................................................................................100
A1.3.3 RESONANTTUNNELDIODES......................................................................................101
A1.4 MOLECULAR VAPOUR LASERS................................................................................101
A1.4.1 OPTICALLY PUMPED FIRLASERS................................................................................102
A1.5 POWER COMBINING...................................................................................................103
A1.5.1 POWERCOMBININGTECHNIQUES...............................................................................103
A1.6 QUANTUM CASCADE LASERS (QCL)........................................................................105
A1.7 PHOTOMIXING ............................................................................................................105
ANNEX 2.................................................................................................................................107
A2.1 MIXER TYPES...............................................................................................................107
A2.1.1 FUNDAMENTAL PUMP,SINGLE DIODE WAVEGUIDE MIXER............................................107
A2.1.2 SUB-HARMONIC, DOUBLE DIODE, MIXERS...................................................................107
A2.1.3 FUNDAMENTALLY PUMPED,BALANCED MIXER............................................................108
A2.2 DIODE MIXER DEVELOPMENT.................................................................................110
A2.2.1 INDIVIDUAL AND SMALL ARRAYS OF DIODES...............................................................110
A2.2 MONOLITHIC.............................................................................................................110
A2.2.3 DIODES ON QUARTZ...................................................................................................110
A2.2.4 MEMBRANE DEVICES.................................................................................................111
ANNEX 3.................................................................................................................................112
APPLICATIONS LIST PROVIDED BY RATO CONSIDER IN THE “HIGHESTUSABLEFREQUENCY
STUDY”.................................................................................................................................112
ANNEX 4.................................................................................................................................113
SOME TYPICAL SUPPLIERS OF FSOEQUIPMENT........................................................................113
ANNEX 5.................................................................................................................................114
EXAMPLELINKBUDGETS.......................................................................................................114
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Theoretical Appraisal of the Highest Usable Frequencies .
1 Introduction
This Report investigates the upper operational frequency limit of several potential
communications and radar systems, operating above 100 GHz; (Radiocommunications
Agency ITT Reference AY 4329 “Theoretical Appraisal of the Highest Usable Frequencies”).
This study has examined the constraints imposed by propagation conditions, device
technology and safety aspects. Gaseous absorption renders nearly all wireless based systems
non-viable above 1000 GHz. The performance of systems in the infrared and optical
windows (generally referred to as free space optical, FSO) systems have also been examined
and compared with millimetre wave systems. These FSO systems are currently available as
operational equipment.
The performances of several potential applications, which included point-to-point fixed
services, broadband wireless access, satellite services, high-altitude platform systems, short-
range nomadic services, indoor communications and anti-collision radar, have been estimated.
The performance of point to point millimetre wave systems are also compared with existing
FSO systems
The propagation mechanisms, which affect millimetre wave and optical communications
systems, are described in detail in Section 2. The technology of millimetre wave devices is
discussed in detail in Section 3, where a review has been conducted to estimate the
performance parameters (e.g. amplifier output levels, noise figures, etc) and device
technologies which could be appropriate for commercially available systems in the next ten
years.
Section 4 examines the performance limitations of these systems by choosing a set of realistic
parameters for each of the candidate systems. The link margins, which include gaseous
absorption, are then calculated for clear air conditions. The range limitations and achievable
performance in terms of availability are then determined in adverse climatic conditions.
Upper limits of operational frequency are found to range from ~150 GHz to 700 GHz
depending on the application. Most systems, excluding fixed satellite services, are found to
be suitable for frequencies near or in excess of 300GHz, depending on the range. In general
the higher upper frequency limits results from applications which could make use of high gain
antennas and be appropriate for operations over short ranges, such as anti-collision radar
systems. Surprisingly, short-range indoor communications for home networks are found to
have one of the lowest upper limits of frequency. This arises from the need to deploy low
gain antennas and safety considerations, which limit the RF power flux density from small-
aperture low-gain antennas in the home environment.
The performance of FSO systems in fog conditions, which persists for considerable periods of
time (1% to 2%), is poor. Although both millimetre wave and FSO systems have similar
performances in heavy rain conditions, millimetre wave systems are much less affected by fog
and turbulence.
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Theoretical Appraisal of the Highest Usable Frequencies .
2 Propagation in the Millimetric and Infra-red Wavebands
This section of the Report considers the various propagation constraints imposed by the
Earth’s atmosphere. These include absorption by atmospheric gases, scattering and
attenuation by hydrometeors in the form of rain and cloud/fog, and scintillation phenomena
induced by atmospheric turbulence.
2.1 Gaseous Attenuation
Gaseous attenuations have been calculated using Recommendation ITU-R P.676-5, Annex 1
(Attenuation by Atmospheric Gases) [ITU-R, 2001], for the millimetric region of the
spectrum, at frequencies up to 1000 GHz, 1 THz, and LOWTRAN 7 [Kneizys et al, 1988,
1989] for the regions above 1 THz.
2.2 Specific Gaseous Attenuation
Specific gaseous attenuations are calculated for sea-level conditions, with a pressure of
1013.25 hPa, temperature of 15ºC and a surface water-vapour density of 7.5 g/m3,
representing a relative humidity of ~58%. The following Figures show the specific
attenuation in dB/km from 10GHz to 1000 THz.
In the region from about 1 THz to 10 THz, attenuations are in excess of 200 dB/km the
atmosphere can be regarded as essentially opaque, as shown in the next Figure, although some
of the detail is smoothed out because of the limitation in frequency resolution of 5 cm-1, i.e.
300 GHz, inherent in the LOWTRAN model.
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Theoretical Appraisal of the Highest Usable Frequencies .
FIGURE 2.1a
Specific attenuation at sea level
(Pressure = 1013.25 hPa, temperature = 15ºC, water-vapour density = 7.5 g/m3)
FIGURE 2.1b
Specific attenuation at sea level
(Pressure = 1013.25 hPa, temperature = 15ºC, water-vapour density = 7.5 g/m3)
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Theoretical Appraisal of the Highest Usable Frequencies .
FIGURE 2.1c
Specific attenuation at sea level
(Pressure = 1013.25 hPa, temperature = 15ºC, water-vapour density = 7.5 g/m3
FIGURE 2.1d
Specific attenuation at sea level from 0 to 1.5 THz
(Pressure = 1013.25 hPa, temperature = 15ºC, water-vapour density = 7.5 g/m3
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Theoretical Appraisal of the Highest Usable Frequencies .
FIGURE 2.1e
Specific attenuation at sea level from 0 to 1.5 THz
(Pressure = 1013.25 hPa, temperature = 15ºC, water-vapour density = 7.5 g/m3
2.3 Path Attenuation Through the Clear Atmosphere from Sea Level
The total path attenuation through the clear atmosphere has been calculated by dividing the
atmosphere into layers, each with defined pressure, temperature, water-vapour density, and
concentrations of other, minor, atmospheric molecules including O, CO , CO, CH , N O,
3 2 4 2
NH , NO and SO . Pressure and temperature are defined using the U.S. Standard
3 2 2
Atmosphere (1976), while an exponential model is used for water vapour, with a scale height
of 2 km. Figures 2.2a and 2.2b show the resulting path attenuations for vertical transmission
paths and at 30º elevation. Figures 2.2c and 2.2d show the same data on different scales to
highlight the window regions in the infra-red region
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Theoretical Appraisal of the Highest Usable Frequencies .
FIGURE 2.2a
Path attenuation at 90º elevation
US Standard Atmosphere, 7.5 g/m3
FIGURE 2.2b
Path attenuation at 30º elevation
US Standard Atmosphere, 7.5 g/m3
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