Practical RF Handbook

hicknesses are considered 5 mm (0.200″) and 0.5 mm (0.020″). Absorption loss for steel and copper 200 150 100 50 0 A bs or pt io n lo ss (d B) 10 102 103 104 105 106 Frequency (Hz) Steel 5 mm (0.2 in) Steel 0.5 mm (0.02 in) or copper 5 mm (0.2 in) Copper 0.5 mm (0.02 in) Figure 6 Reflection loss for steel and copper 200 150 100 50 0 R ef le ct io n lo ss (d B) Plane wave Copper Steel 10 102 103 104 105 106 Frequency (Hz) R (Plane wave) = 168.10.Log(f) – 10 log (µ/σ) (dB) Figure 7 Reflection loss (plane wave) The reflection loss increases with the ratio of the impedance of the incident wave to the impedance of the screen material. For plane EM waves, such as exist beyond a distance of about one-sixth of a wavelength from the source, the wave impedance is constant at about 377 ohms. The impedance of the screen material is proportional to the square root of the frequency times the permeability divided by the conductivity. Good conductors and non-magnetic materials give low screen impedance and hence high reflection loss. Working at higher frequencies raises the screen impedance and lowers the reflection loss. Figure 7 shows some typical values for reflection loss. Combined absorption and reflection loss for plane waves Figure 8 shows the total shielding effectiveness for a copper screen 0.5 mm (0.02″) thick, in the far field, where the wave front is plane and the wave impedance is constant at 377 ohms. The poor absorption at low frequencies is compensated by the high reflection loss. The multiple reflection correction factor, B, is normally neglected for electric fields because the reflection loss is so large. This point will be considered later. Reflection loss in the near field The wave impedance in the near field depends on the nature of the source of the wave and the distance from that source. Figure 9 shows that for a rod or straight wire antenna, 256 Practical Radio-Frequency Handbook the wave impedance is high near the source. The impedance falls with distance from the source and levels out at the plane wave impedance value of 377 ohms. In contrast, if the source is a small wire loop, the field is predominantly magnetic and the wave impedance is low near the source. The impedance rises with distance away from the source but will also level at the free space value at distance beyond about one-sixth wavelength. As detailed in the ‘Enclosure Design’ section, EMI shields are required in a range of materials for reasons other than those of attenuation alone. Such factors as compatibility with existing materials, physical strength and corrosion resistance, are all relevant. The properties of those materials used by RFI Shielding Ltd., are discussed here to assist in selection of the most suitable with regard to these factors. Comparative tables are provided at the end of the section. Remembering that reflection loss varies as the ratio of wave to screen impedance it can be seen that reflection loss will depend on the type of wave being dealt with and how far the screen is from the source. For small, screened, equipments we are usually working in the near field and have to deal with this more complex situation. Figure 10 shows the relevant formulae. The procedure for calculating the correction factor, B, is also shown in Figure 10. This is normally only calculated for the near-field magnetic case and then only if the absorption loss is less than 10 dB. Re-reflection within the barrier, in the absence of much absorption, results in more energy passing through the second face of the barrier. Thus the correction factor is negative indicating a reduced screening effectiveness. Screening effectiveness in the far field Plane wave 0.5 mm (0.02 in) Cu250 200 150 100 50 0 Sc re en in g ef fe ct (d B) Total Reflection Absorption 10 102 103 104 105 106 Frequency (Hz) Wave impedance near E and H field sources 104 3770 103 102 37.7 10 W av e im pe da nc e (oh ms ) E-field dominant Plane wave Zo = 377 H-field dominant Near field Far field 0.1 1.0 10 Distance from source (in units of λ ÷ 2π) Figure 8 Figure 9 Appendix 11 257 Reflection Loss in the Near Field R (Electric) = 321.8 – 20.log(r) – 30.log(f) – 10.Log(µ/σ) (dB) R (Magnetic) = 14.6 + 20.Log(r) + 10.Log(f) + 10.Log(σ/µ) (dB) r = distance from source to screen (m) f = frequency (Hz) µ = permeability relative to copper σ = conductivity relative to copper Correction Factor B B = 20.Log(1-exp(– 2 t/δ)) (dB) t = screen thickness (mm) δ = skin depth = 0.102 | f. . | (mm)÷ µ σ For (t/δ) = 0.1, B = – 15 dB = 0.5, = – 4 dB = 1.0, = – 1 dB Figure 10 Figure 11 illustrates the variation of reflection loss with distance and frequency in the near field for a copper screen. Notice that in the near-field, as reflection loss for electric fields is higher, the closer the screen is to the source, the better. For magnetic fields the reverse is true. Reflection loss in near-field for copper screen r = distance from source to screen (m) 300 250 200 150 100 50 0 R ef le ct io n lo ss (d B) Electric r = 1 m Electric r = 10 m Plane wave Magne tic r = 10 m Magne tic r = 1 m 102 103 104 105 106 107 108 Frequency (Hz) Figure 11 258 Practical Radio-Frequency Handbook The electronic design engineer can therefore specify his screening requirements in terms of the emission frequency range of interference sources, their location relative to the screening effectiveness to be achieved. The mechanical design engineer can then begin to explore screening enclosure material options and calculate their screening effectiveness. Screen materials The provision of high screening effectiveness at very low frequencies can only be achieved by high permeability materials. The permeability of these materials falls off with frequency and can also be reduced if the incident magnetic field is high. Further, the permeability may be reduced by the mechanical working of the metal necessary to fabricate the required shape of screen. For all these reasons the exploitation of high permeability materials for screening purposes is a demanding task and recourse should be made to a specialist supplier in this field. On the other hand, at higher frequencies it becomes possible to use cheaper metallic materials at quite modest thickness. Some typical screen materials are listed in Figure 12. Depending on the screening effectiveness requirement, which must never be overstated, it often becomes cost-effective to distinguish between a material for electric screening purposes and another material which provides the physical support and determines the mechanical integrity of the screened enclosure. As an example, consider a plastic box which provides mechanical and, perhaps, environmental protection to an enclosed electronic circuit. This box might be lined with flexible laminates, electroless plating, conductive paints, metallic foil tapes, wire spray or vacuum metallizing. The box might be made of conductive plastic. Large screened enclosures are often made of steel-faced wooden sheets or of welded steel sheets mounted on a structural framework. The final choice will depend on considerations involving the ability to make effective joints to the screening material for items such as access panels, connectors and windows; the avoidance of significant galvanic corrosion; the ability to withstand whatever external environment is stipulated, including mechanical shock and vibration. All these factors must be considered against the cost of achieving the stated required performance. Reasons for Joints or Apertures in Screened Enclosures Seamless construction not feasible Access panel needed for equipment installation/ maintenance Door for instant access Ventilation openings needed Windows needed for viewing displays and meters Panel mounting components, e.g.: Connectors for power and signal leads Indicator lamps Pushbuttons Fuses Switches Control shafts Materials for Screens Sheet metal Adhesive metal foil sheet and tape Flexible laminates Conductive paint Wire spray (e.g. zinc) Vacuum metallizing Electroless plating Figure 12 Figure 13 Appendix 11 259 Integrity of a screened enclosure It has been shown that good screening effectiveness can generally be achieved by reasonably thin metal screens but it is assumed that the screen is continuous and fully surrounds the sensitive item, without gaps or apertures. In practice it is rarely possible to construct a screen in this way. The screen may have to be fabricated in pieces which must be joined together. It may be necessary to penetrate the screen to mount components. Any decrease in the effective conductivity of the screen, because of joints, will reduce screening effectiveness. Any slots or apertures can act as antennas allowing RF energy to leak in or out. Figure 13 lists some of the reasons why screened enclosures may require joints or apertures. Now consider, briefly, the attenuation of EM waves through a metallic gap or hole. Gaps and holes in screens Concerning the gap or hole which penetrates the screen, as a waveguide through which EM energy is flowing. If the wavelength of this energy is too long compared with the lateral dimensions of the waveguide, little energy will pass through. The waveguide is said to be operating beyond cut-off. Figure 14 shows formulae for cut-off frequency in round and rectangular waveguide. For operating frequencies much less than the cut-off frequency the formulae for shielding effectiveness are also given. Notice that the attenuation well below cut-off depends only on the ratio of length to diameter. Attenuation of about 100 dB can be obtained for a length to diameter ratio of 3. Thus it may be possible to exploit the waveguide properties of small holes in thick screens where penetration is essential. An alternative way of achieving a good length/diameter ratio is to bond a small metallic tube of appropriate dimensions, normal to the screen. Waveguide Cut-off Frequency (fc) In round guide, fc = 175.26/d GHz (6.9/d in.) d = waveguide diameter (mm) In rectangular guide, fc = 149.86/a GHz (5.9/a in.) a = largest dimension of waveguide cross-section (mm) Shielding Effectiveness (s) of Waveguide For operating frequencies well below cut-off S (round) = 32 t/d (dB) S (rectangular) = 27.2 t/a (dB) t = Screen thickness Figure 14 This theory and its extension to multiple holes, forms the design basis for commercially available perforated components such as viewing and ventilation panels which must have good screening effectiveness. 260 Practical Radio-Frequency Handbook Seams and joints For joints between sheets which are not required to be parted subsequently, welding, brazing or soldering are the prime choices. The metal faces to be joined must be clean to promote complete filling of the joint with conductive metal. Screws or rivets are less satisfactory in this application because permanent low impedance contact along the joint between the fastenings is difficult to ensure. For joints which cannot be permanently made, conducting gaskets must be used to take up the irregularities in the mating surfaces. Consideration should be given to the frequency and circumstances in which such joints will be opened and closed during the life of the equipment. One classification defines Class A, B and C joints. Class A is only opened for maintenance and repair. In a Class B joint the relative positions of mating surfaces and gasket are always the same, e.g. hinged lids and doors. In a Class C joint the relative positions of mating surfaces and gasket may change, e.g. a symmetrical cover plate. A wide range of gasket materials is available commercially. They include finger strip; wire mesh with or without elastomer core; expanded metal and oriented wire in elastomer and conductive elastomers. Most suppliers provide estimates of screening effectiveness which can be achieved with the various gaskets. The gaskets come in a variety of shapes to suit many applications. The selection of a suitable gasket depends on many factors, the most important of which are listed in Figure 15. Some Factors Governing Choice of Gasket Screening effectiveness Class A, B or C joint Mating surface irregularity Gasket retention method Flange design Closure pressure Hermetic sealing needed? Corrosion resistance Vibration resistance Temperature range Subject to EMP? Cost Figure 15 Appendix 12 Worldwide minimum external noise levels The figures reproduced below give the minimum levels of external noise ever likely to be encountered at a terrestrial receiving site. They are thus a useful guide to the receiver designer, in that there is, in general, no point in designing a receiver to have a noise level much lower than that to be expected from a reasonably efficient aerial system. (The only exception is where, for some special purpose, a very inefficient aerial must be used, e.g. a buried antenna servicing an underground bunker.) The figures cover the whole frequency range of radio frequencies with which this book is concerned, 10 kHz to 1 GHz, and beyond. The report from which they are reproduced also covers frequencies from 10–1 Hz to 104 Hz and 1 to 100 GHz. Figures A12.1 and A12.2 are reproduced from Report 670 (Mod F) ‘Worldwide Minimum External Noise Levels, 0.1 Hz to 100 GHz’, with prior authorization from the copyright holder, the ITU. Copies of this and other reports and recommendations may be obtained from: International Telecommunication Union General Secretariat, Sales and Marketing Service Place des Nations, CH, 1211 Geneva 20 Switzerland Telephone: +41 22 730 61 41 (English)/ +41 22 730 61 42 (French) Telex: 421 000 uit ch/Fax: +41 22 730 51 94 X…400: S=Sales; P=itu; C–ch Internet: Sales@itu.ch Annex 1: ITU-R Recommendations and Reports ITU-R Recommendations constitute a set of standards previously known as CCIR Recommendations. They are the result of studies undertaken by Radiocommunication Study Groups on: • the use of radio frequency spectrum in terrestrial and space radiocommunication including the use of satellite orbits: • the characteristics and performance of radio systems, except the inter-connection of radio systems in public networks and the performance required for these interconnections which are part of the ITU-R Recommendations; 262 Practical Radio-Frequency Handbook • the operation of radio stations; • the radio communication aspects of distress and safety matters. ITU-R Recommendations are divided into series according to the subject areas they cover as follows: Series Subject area BO* Broadcast satellite service (sound and television) BR Sound and television recording BS* Broadcasting service (sound) BT* Broadcasting service (television) F Fixed Service IS Inter-service sharing and compatibility 180 160 140 120 100 80 60 40 20 0 F a (dB ) A C B E D 104 2 5 105 2 5 106 2 5 107 2 5 108 Frequency (Hz) 2.9 × 1020 2.9 × 1018 2.9 × 1016 2.9 × 1014 2.9 × 1012 2.9 × 1010 2.9 × 108 2.9 × 106 2.9 × 104 2.9 × 102 Figure A12.1 Fa versus frequency (104 to 108 Hz). This figure covers the frequency range 104 to 108 Hz, i.e., 10 kHz to 100 MHz. The minimum expected noise is shown via the solid curves and other noises that could be of interest as dashed curves. For atmospheric noise, the minimum values expected are taken to be those values exceeded 99.5% of the time and the maximum values are those exceeded 0.5% of the time. For the atmospheric noise curves, all times of day, seasons, and the entire Earth’s surface has been taken into account. More precise details (geographic and time variations) can be obtained from Report 322. The man-made noise (quiet receiving site) is that noise measured at carefully selected, quiet sites, world-wide as given in Report 322. The atmospheric noise below this man-made noise level was, of course, not measured and the levels shown are based on theoretical considerations. Also shown is the median expected business area man-made noise. A Atmospheric noise, value exceeded 0.5% of time; B Atmospheric noise, value exceeded 99.5% of time; C Man-made noise, quiet receiving site; D Galactic noise; E Median business area man-made noise, Minimum noise level expected. M* Mobile, radiodetermination, amateur and related satellite service P* Propagation RA Radioastronomy S Fixed-satellite service SA Space applications SF Frequency sharing between the fixed-satellite service and the fixed service SM Spectrum management techniques SNG Satellite news gathering TF Time signals and frequency standard emissions V Vocabulary and related subjects There are currently 594 ITU-R Recommendations in force. ITU-R Recommendations are progressively being posted on TIES and will be accessible by subscribers to the ITU-R Recommendations Online Service. For further information please contact the ITU Sales Service. Figure A12.2 Fa versus frequency (108 to 1011 Hz). The frequency range 108 to 1011 Hz is covered, i.e., 100 MHz to 100 GHz. Again, the minimum noise is given by solid curves, while some other noises of interest are given by dashed curves. A Estimated median business area man-made noise; B Galactic noise; C Galactic noise (toward galactic centre with infinitely narrow beamwidth); D Quiet sun ( 12 degree beamwidth directed at sun); E Sky noise due to oxygen and water vapour (very narrow beam antenna); upper curve, 0° elevation angle; lower curve, 90° elevation angle; F Black body (cosmic background), 2.7 K, Minimum noise level expected. 40 30 20 10 0 –10 –20 –30 – 40 F a (dB ) 108 2 5 109 2 5 1010 2 5 1011 (1 GHz) Frequency (Hz) 2.9 × 106 2.9 × 105 2.9 × 104 2.9 × 103 2.9 × 102 2.9 × 10 2.9 2.9 × 10–1 2.9 × 10–2 t a (K ) A C B D E(0°) F E (90°) *Also includes ITU-R Reports Appendix 12 263 Appendix 13 Frequency allocations Frequency allocations are settled on a world-wide basis by WRC, the World Radio Conference, previously known as WARC, the World Administrative Radio Conference. The Conference, which is convened as necessary (usually every two or three years), is held under the aegis of the International Telecommunications Union (ITU), which is itself an organ of the United Nations. Implementation is down to individual countries, not all of which are represented at the WRC, while not all of those that are observe all of the allocations. Annexe 1: Radio frequency spectrum management in the UK (part of Region 1) In the UK, frequencies are allocated by The Radio Communications Agency, which is an Executive Agency of the Department of Trade and Industry. The documents described in the previous edition, covering the range 9 kHz to 105 GHz in five separate booklets, are now superseded by a single new document, RA365. At the time of writing, this is itself currently under review, and consequently it is not reproduced here, either in whole or in part. However, this document is to be maintained, updated as required, as an on- line document, and may be consulted and downloaded from the Radio Communications Agency’s website at www.radio.gov.uk The Radio Communications Agency itself may be contacted at: The Radio Communications Agency, Wyndham House, 189 Marsh Wall, London E14 9SX. Tel. 020 7211 0211 The document ‘UK Radio Interface Requirements’  Crown copyright, Radio Communication Agency, 2000, downloadable from www.radio.gov.uk, is reproduced in part below. It includes a list indexing UK Radio Interface Requirements number 2000 to 2041, together with their file size in WORD format, or PDF format (usually much shorter than the WORD format). UK Radio Interface Requirement 2030 refers to Short Range Devices, while other requirements refer to subjects as varied as EPIRBs, PMR, TETRA, Cordless telephony etc., etc. UK Radio Interface Requirements The Radio Equipment and Telecommunications Terminal Equipment (R&TTE) Directive 1999/5/EC was implemented in the UK on 8 April 2000. Amongst other things, the Directive replaced the previous national type approval regimes in place throughout the various Member States of the European Union (EU). The Directive introduced a harmonised set of essential requirements and conformity assessment procedures governing the placing on the market of equipment within its scope. Version WORD PDF UK Radio Interface Requirements Index 57.5 KB 2000 Point-to-Point radio-relay systems Operating in 1.41 138 KB 90 KB Fixed Service frequency bands Administered by the Radiocommunications Agency 2001 UK Interface Requirement 2001 Private Business 1.0 1378 KB 402 KB Mobile Radio 2004 Private Business Mobile Radio (TETRA) (Draft) 0.1 79 KB 27 KB UK Interface Requirement 2005 Wideband 2005 Transmission Systems Operating in the 2.4 GHz 1.0 74 KB 27 KB ISM Band and Using Spread Spectrum Modulation Techniques 2010 UK Radio Interface Requirement 2010 For Public 1.0 81 KB 30 KB Paging Services 2011 UK Radio Licence Interface Requirement 2011 for 1.0 135 KB 44 KB the Cordless Telephony Service 2029 UK Radio Interface Requirement 2029 for Maritime 1.0 57 KB 20 KB Emergency Position indicating Radio Beacons (EPIRBS) intended for use on the frequency 121,5 MHz or the frequencies 121,5 MHz and 243 MHz for homing purposes only 2030 UK Radio Interface Requirement 2030 Short Range 1.0 180 KB 80 KB Devices 2032 UK Radio Interface requirement 2032 for 1.0 56 KB 18 KB transmission of differential correction signals of Global Navigation Satellite Systems (DGNSS) from Maritime Radio stations in the Frequency Bands 162.4375–162.4625 and 163.0125–163.03125 MHz 2036 UK Radio Licence Interface Requirement 2036 1.0 110 KB 29 KB For Mobile Asset Tracking Services Annexe 2: Radio frequency spectrum management in the US (part of Region 2) The Communications Act of 1934 provides the foundations for US spectrum rules and regulations, management and usage. The basic authority is delineated in Sections 303, 304 and 305 of the Act. Section 303 presents the general powers of the Federal Communications Commission (FCC) regarding transmitting stations; 304 deals with waiving frequency claims; and 305 provides that Federal Government owned stations shall be assigned frequencies by the President (delegated to the Department of Commerce National Telecommunications and Information Administration [NTIA] via Executive Appendix 13 265 266 Practical Radio-Frequency Handbook Order 12046). Section 305 is particularly significant as it provides for the separation of authority between the Federal Government and the non-Federal Government, or private sector. Section 305 has resulted in two US spectrum regulatory bodies: the FCC regulating the non-Federal Government sector, and the NTIA regulating the Federal Government sector. Section 305 has also resulted in agreements between the Federal Government and non-Government sectors that essentially divide the spectrum usage into three parts: exclusive Federal Government use, exclusive non-Federal Government use, and use shared between the two sectors. The NTIA is aided by other federal agencies and departments through an advisory group, the Interdepartmental Radio Advisory Committee (IRAC). IRAC carries out frequency coordination for the Federal Government Agencies, recommends technical standards, and reviews major Federal Government systems to assure spectrum availability. The IRAC also provides advice to the NTIA on spectrum policy issues. Although the NTIA and FCC generally operate independently of each other, they coordinate closely on spectrum matters. An FCC liaison representative participates in the IRAC, and the NTIA participates in the rule making process of the FCC with the advice of the IRAC. FCC and NTIA spectrum sharing coordination is also carried out daily as required. For the purposes of international coordination, the ITU divides the world into three regions as presented in Figure A13.1, with each region having its own allocations, although there is much commonality among the regions. Each region has over 400 distinct frequency bands and hundreds of footnotes (exceptions or additions to the table). Also reproduced (as Table A13.1, below) is a sample page from the frequency allocation table as it applies internationally, and to the US in particular. Figure A13.1 180° 160° 140° 120° 100° 80° 60° 40° 20° 0° 20° 40° 60° 80° 100° 120° 140° 160° 180° 160° 180° 160° 140° 120° 100° 80° 60° 40° 20° 0° 20° 40° 60° 80° 100° 120° 140° 160° 180° 160° 75° 60° 40° 20° 0° 20° 40° 60° 75° 60° 40° 20° 0° 20° 40° 60° B A Region 1Region 2 Region 3 Region 3 ABC C C Ta b l e A 1 3 . 1 R eg i o n s d e fi n e d f o r f r e q u e n cy a l l o c a t i o n s . S h a d e d a r e a r e p re s e n t s t r o p i c a l z o n e . I n t e r n a t i o n a l U n i t e d S t a t e s B a n d N a t i o n a l G o ve r n m e n t N o n - G o ve rn m e n t R eg i o n 1 R eg i o n 2 R eg i o n 3 M H z P r ov i s i o n s A l l o c a t i o n A l l o c a t i o n R e m a r k s M H z M H z M H z 1 2 3 4 5 3 5 0 0 – 3 7 0 0 3 5 0 0 – 3 6 0 0 U S 1 1 0 A E RO NAU T I C A L R a d i o l o c a t i o n F I X E D R A D I O NAV I G AT I O N F I X E D - S AT E L L I T E ( S p a c e - t o - E a r t h ) ( G r o u n d - b a s e d ) M O B I L E ex c e p t a e r o n a u t i c a l m o b i l e R A D I O L O C AT I O N R a d i o l o c a t i o n 7 8 4 7 8 1 7 8 2 7 8 5 G 5 9 G 1 1 0 3 6 0 0 – 4 2 0 0 3 6 0 0 – 3 7 0 0 U S 1 1 0 A E RO NAU T I C A L R a d i o l o c a t i o n F I X E D U S 2 4 5 R A D I O NAV I G AT I O N F I X E D - S AT E L L I T E F I X E D - S AT E L L I T E ( G r o u n d - b a s e d ) ( S p a c e - t o - E a r t h ) ( S p a c e - t o - E a r t h ) R A D I O L O C AT I O N M o b i l e 7 8 6 G 5 9 G 1 1 0 3 7 0 0 – 4 2 0 0 3 7 0 0 – 4 2 0 0 F I X E D F I X E D F I X E D - S AT E L L I T E F I X E D - S AT E L L I T E ( S p a c e - t o - E a r t h ) ( S p a c e - t o - E a r t h ) M O B I L E ex c e p t a e r o n a u t i c a l m o b i l e 7 8 7 N G 4 1 4 2 0 0 – 4 4 0 0 4 2 0 0 – 4 4 0 0 U S 2 6 1 A E RO NAU T I C A L A E RO NAU T I C A L A E RO NAU T I C A L 7 9 1 R A D I O NAV I G AT I O N R A D I O NAV I G AT I O N R A D I O NAV I G AT I O N 7 8 9 7 8 8 7 9 0 7 9 1 4 4 0 0 – 4 5 0 0 4 4 0 0 – 4 5 0 0 F I X E D F I X E D M O B I L E M O B I L E 4 5 0 0 – 4 8 0 0 4 5 0 0 – 4 8 0 0 U S 2 4 5 F I X E D F I X E D - S AT E L L I T E F I X E D M O B I L E ( S p a c e - t o - E a r t h ) F I X E D - S AT E L L I T E ( S p a c e - t o - E a r t h ) M O B I L E 7 9 2 A The following is reproduced from RA114 Rev. 8 Oct. 2000, Short Range Devices Information Sheet, © Crown copyright, Radio Communication Agency, 2000. What is a short range device? 1. This is a general term which is applied to various radio devices designed to operate over short ranges and at low power levels. This includes alarms, telemetry and telecommand devices, radio microphones, radio local area networks and antitheft devices with maximum powers ranging up to 500 milliwatt at VHF/UHF, as well as certain microwave/doppler devices with maximum powers of up to 5 Watts. A full list of devices covered by this information sheet and the parameters that they must operate within, can be found in the UK Radio Interface Requirements IR 2005, IR 2006 and IR 2030. 2. Short range devices (SRDs) are for terrestrial use only, unless stated otherwise. SRDs normally operate on a non-protected, non-interference basis, see paragraphs under the heading Interference (paragraph 56 onwards). Some points to note 3. When selecting parameters for new SRDs, manufacturers and users should pay particular attention to the potential for interference from other systems operating in the same or adjacent bands. This is particularly important where a device may be used in a safety critical application. 4. SRDs cannot claim protection from other authorised services and must not cause harmful interference. 5. It should be remembered that the pattern of radio use is not static. It is continuously evolving to reflect the many changes that are taking place in the radio environment; including the introduction of new applications and technologies. Spectrum allocations may need to be reviewed from time to time to reflect these changes and the position set out in this information sheet is subject to amendment following consultation with interested parties. Appendix 14 SRDs (Short Range Devices) Appendix 14 269 The following definitions are used in this information sheet: 6. Telecommunication: Any transmission, emission or reception of signs, signals, writing, images and sounds or intelligence of any nature by wire or radio, optical or other electromagnetic systems. 7. Radiocommunication: Telecommunication by means of radio waves. 8. Alarm: An alarm system which uses radio signals to generate or indicate an alarm condition, or to arm or disarm the system. 9. Radar Level Gauges: A device used mainly for measuring the contents of containers at industrial sites such as refineries. These devices operate in the microwave bands at low power levels. 10. Radio Local Area Networks (RLANS): A radiocommunication device which links data networks/computers. 11. Radio Microphone: A microphone that uses a radio link to convey speech or music to a remote receiver. 12. Teleapproach: The use of radiocommunication for the purpose of gaining information as to the presence of any moving object. However, it is possible for the target to remain fixed whilst the source is mobile. 13. Telecommand: The use of radiocommunication for the transmission of signals to initiate, modify or terminate functions of equipment at a distance. 14. Telemetry: The use of radiocommunication for automatically indicating or recording measurements at a distance from the measuring instrument. Why have some of these devices been exempted from licensing? 15. The potential of SRD’s to cause interference to other radio users is minimal, provided that they operate under the correct technical conditions. In keeping with the Government’s general policy of deregulation and reducing unnecessary burdens on business, the Agency has removed the need for most SRDs to be licensed under Section 1 of the Wireless Telegraphy Act 1949. Details of the current exemption regulations for SRDs are contained in Schedule 6 of the Statutory Instruments (SI) titled “The Wireless Telegraphy (Exemption) Regulations 1999” (SI 1999 No. 930) as amended by SI 2000 No 1012. Note the Exemption SI is reviewed annually and is amended or reissued as required. 16. Copies of Statutory Instruments and those published previously are available from any Stationery Office Bookshop or from the HMSO website at www.hmso.gov.uk/ legislation. UK Radio Interface Requirements 17. Under the Radio and Telecommunications Terminal Equipment (R&TTE) Directive, Directive 1999/5/EC, Member States are required to notify the European Commission of the details of the radio interfaces they regulate. These interfaces specify the conditions to comply with in order to use the radio spectrum. In the UK these notified interfaces are published as UK Radio Interface Requirements and together with further details on the R&TTE Directive they can be found on our website at 270 Practical Radio-Frequency Handbook www.radio.gov.uk and then by going to Documents, Library, Conformity Assessment (including R&TTE Directive). 18. The “UK Radio Interface Requirement 2030 Short Range Devices” (IR 2030) contains the requirements for the licensing and use conditions for SRD’s in the specified frequency bands, this can be found on our website as detailed above followed by going to UK Radio Interface Requirements, 2030. RA114 continues with sections 19–88 covering, among other topics, channel spacing requirements for IR2030, details on various types of telemetry and alarms, radiomicrophones, interference, R&TTE Directive/type approval etc., etc. RA114 is to be maintained and updated as required, as an on-line document, and may be consulted and downloaded from the Radio Communications Agency’s website at www.radio.gov.uk For further details of IR2030, see Appendix 13. Types of Short Range Devices Exempt from Licensing Annex 1 Uses Frequency Maximum ERP Specification Medical and Biological Telemetry Medical/Biological Telemetry 300 kHz–30 MHz See specification W6802 Medical and Biological Telemetry (narrow band and wide band) 173.7–174 MHz 10 milli Watts MPT 1312 Medical/Biological Telemetry 458.9625–459.1000 MHz 500 milli Watts MPT 1329* General Telemetry and Telecommand Devices General Telemetry and 26.995 MHz 1 milli Watt MPT 1346 Telecommand 27.045 MHz 27.095 MHz 27.145 MHz 27.195 MHz Telemetry Systems for Databuoys 35 MHz 250 milli Watts MPT 1264 General Telemetry and Telecommand 173.2–173.35 MHz 10 milli Watts MPT 1328 (narrow band) General Telemetry and 173.2–173.35 MHz 10 milli Watts MPT 1330 Telecommand (wide band) General Telemetry, Telecommand 417.90–418.1 MHz 250 micro Watts MPT 1340 and Alarms Vehicle Radio Keys 433.72–434.12 MHz 10 milli Watts MPT 1340 Industrial/Commercial Telemetry 458.5–458.95 MHz 500 milli Watts MPT 1329** and Telecommand Alarms Short Range Alarms for the elderly and infirm 27.450 MHz 500 micro Watts MPT 1338 Appendix 14 271 34.925 MHz 34.950 MHz 34.975 MHz General Alarms 417.90–418.10 MHz 250 micro Watts MPT 1340 Vehicle Paging Alarms 47.4 MHz 100 milli Watts MPT 1374 Marine Alarms for Ships 161.275 MHz 10 milli Watts MPT 1265 Mobile Alarms 173.1875 MHz 10 milli Watts MPT 1360 Short Range Fixed in Building 173.225 MHz 10 milli Watts MPT 1344 Alarms between 1 mW and 10 mW Fixed Alarms 458.8250 MHz 100 milli Watts MPT 1361 Transportable and Mobile Alarms 458.8375 MHz 100 milli Watts MPT 1361 Vehicle Paging Alarms with integral 458.9000 MHz 100 milli Watts (paging) MPT 1361 Radio Key 1 milli Watt (radio key) Model Control General Models 26.96–27.28 MHz 100 milli Watts N/A + Air Models 34.955–35.255 MHz 100 milli Watts N/A + Surface Models 40.665–40.955 MHz 100 milli Watts N/A + General Models 458.5–459.5 MHz 100 milli Watts N/A + Short Range Microwave Devices or Doppler Apparatus Maximum EIRP Apparatus designed solely for 10.577–10.597 GHz 1.0 Watt MPT 1349 outdoor use Apparatus designed for indoor use and 10.675–10.699 GHz 1.0 Watt MPT 1349 Short range data links within one building Apparatus designed for fixed or 24.150–24.250 GHz 2.0 Watts MPT 1349 portable applications Apparatus designed solely for use 24.250–24.350 GHz 2.0 Watts MPT 1349 in a mobile application Anti-Collision Devices 31.80–33.40 GHz 5.0 Watts MPT 1349 Any apparatus not within any 2.445–2.455 GHz 100 milli Watts MPT 1349 category above and short range data links within one building Other Devices Spread Spectrum Applications 2.4–2.483 GHz 100 milli Watts ETS 300 328 (including Radio Lans) Induction Communication Systems 0–185 kHz and see MPT 1337 240–315 kHz specification Uses Frequency Maximum ERP Specification 272 Practical Radio-Frequency Handbook Metal Detectors 0–148.5 kHz See Sl 1980 No 1848 N/A + Access and Anti-Theft Devices and 2–32 MHz See specification MPT 1339 Passive Transponder Systems Teleapproach Anti-Theft Devices 888–889 MHz See specification MPT 1353 Teleapproach Anti-Theft Devices 0–180 kHz See specification MPT 1337 General Purpose Low Power Devices 49.82–49.98 MHz 10 milli Watts MPT 1336 Cordless Audio Equipment 36.61–36.79 and 10 micro Watts MPT 1336 37.01–37.19 MHz Radio Microphones 174.600–175.020 MHz 5 milli Watts (narrowband) MPT 1345 Radio Microphones 173.800–175.000 MHz 2 milli Watts (wide band) MPT 1345 Radio Hearing Aids 173.350–174.415 MHz 2 milli Watts MPT 1345 Uses Frequency Maximum ERP Specification Index Admittance, 9 ADC (analog to digital converter), 168 Adcock antenna, 196 AFC (automatic frequency control), 94, 154 AGC (automatic gain control), 92, 153, 154 Aliasing, 168 AM see Modulation Amplifier, 57, 59, 67– limiting amplifier, 76 log amplifier, 76 parametric, 180 power amplifier (PA), 83 class A, B, C power amplifier, 85, 123 RF power amplifier, 122– push pull amplifier, 124, 127 single-ended, 127 Air-gap, 34 Anode, 50, 54 Antenna, 181– active antenna, 191 aperture, 188, 191 arrays, 196 crossed field, 194 dipole antenna, 171 Australian dipole antenna, 194 halfwave dipole antenna, 181 dish antenna, 196 electrically small antenna, 190 isotropic antenna, 172 monopole antenna, 185 patch antenna, 191 tuning unit, 181 Yagi antenna, 184, 195 Argument, 10 ARQ (automatic repeat request), 84 ASH (amplifier sequenced hybrid), 169 ASCII, 84 Attenuation, 11 attenuation constant, 18 Attenuator, 145, 225, 199–, 215 ATU see Antenna, tuning unit Aurora borealis, aurora australis, 179 Balance, 27 balance pad, 27 balanced feeder, 18 balanced mixer see Mixer transformer balance ratio, 27 Balun see Transformer Bandpass, 13 Bandwidth, 78, 167, 182 occupied bandwidth (OBW), 83, 84, 202 Base, 53 common, 57, 67 Bellini–Tosi antenna, 196 Beryllium oxide, 122 Bias, biasing, 133– Bit: bit error rate (BER), 91 bit period, 83 bit sync, 85 Blocking, 153 Bode plot, 112, 207 Breadboard, 122 Butterworth, see Filter Cables, 228 Cathode, 50 Capacitance, 2–, 69 distributed capacitance, 25 feedback capacitance, 71 inter-winding capacitance, 25 reverse transfer capacitance, 59 self capacitance, 25 Capacitor, 2– on-linear capacitor, 51 variable capacitor, 6, 51 Carrier (s): carrier wave see Wave majority carrier, 57 minority carrier, 52 Cascode, 59, 71 Channel, 57–, 197 channel spacing, 151 274 Index I, Q in-phase, quadrature channel, 155, 165 luminance, chrominance channel, 89 Charge, 2 stored charge, 52 Chebychev see Filter Chirp sounder, 177 Choke, RF, 9 Circle diagram, 10 Circulator, 46 microwave circulator, 47 CISPR, 210 Clarifier, 78 Coax, 18 Coefficient: temperature coefficient, 5, 34 negative temperature coefficient, 6 reflection coefficient, 19 Collector, 53 common collector, 57, 71 Common mode see Signal Complex signal, 165 Compression, 64 Conductance, 1–, 67 mutual conductance, 67 conduction angle, 128 Conductor, 1– Constantan, 1 Copper: tape copper, 27 Corkscrew rule, 6 Coulomb, 2 Coupler: directional, 44 Coupling: critical, 11 Crystal: AT cut crystal, 102 crystal cut, 15 crystal pulling, 17 quartz crystal, 15, 238 SC (strain compensated), 102 Current: magnetizing, 23, 37 CW see Wave dB see Decibel DCS/PCS, 169 Dead zone, 176 Decibel, 18, 199 Decoupling, 5 DECT, 169 Delay: delay line, 90 glass delay line, 89 group delay, 202 Delta, 2, 215 Depletion layer, 50 Desensitisation see Blocking Detector, 76 diode detector, 92, 144 phase detector, 114– quadrature detector, 93 ratio detector, 93 Deviation, 78 Dielectric, 4, 5 dielectric constant (relative permitivity), 45 Diode, 49– hot carrier diode see Diode, schottky PIN diode, 51, 124 Schottkydiode, 52, 64 snap-off diode, 51 varicap diode, 50 zener diode, 52 Dipole see Antenna Discone, 182 Distortion: harmonic distortion, 26 second order distortion, 60 third order distortion, 60 Distribution: Gaussian distribution, 96 Doublet see Antenna Drain, 57– DS see Spectrum DSP (digital signal processor), 168, 202 Ducting, 175 Dynamic range, 74 ECM, 76 Efficiency, 129 radiation efficiency, 181, 191 Egli, 174 Electromagnetic compatibility, 210, 252 Electromotive force see EMF Electron, 2 free electron, 49 EMC see Electromagnetic compatibility EMF, 1, 4 back EMF, 8 Emitter, 53 common emitter, 57, 69 Channel, (Contd) Index 275 Encoding, 85 End effect, 182 Equalizers, 199, 202 ESR, 17 Eye diagrams, 210 Farad, 4– FCC, 207, 211, 265 FDMA, 169 Feedback, 137– negative feedback, 74, 111 positive feedback, 69 Feed, feeder, 18 balanced, see Balance feed point, 182, 191 impedance, 188 Ferrite, 6, 26– core, 26, 37 bead, 9 manufacturers, 235 soft ferrite, 26 FH see Spectrum Field: electric field, 171 induction field, 171 magnetic field, 6, 8, 171 near, far field, 171, 188 radiation field, 171 field strength, 181 Filter: allpass filter, 202 bandpass filter, 75, 147 Butterworth filter, 15 Chebychev filter, 15, 124 crystal filter, 35 elliptic filter, 15, 125, 240 passband: filter passband ripple, 124 finite impulse response filter, 202 highpassfilter, 10, 145 harmonic filter, 124 lattice filter, 35 lowpass filter, 10, 15 notch filter, 145 polyphase filter, 167 SAW filter (surface acoustic wave), 164 second order filter, 35 FIR see Filter FLL see Frequency Floating circuit, 27 FLOT, 197 Flux: flux density, 32 magnetic flux, 6, 7, 23 FM see Modulation FOT, 176 Frequency, frequencies: cut-off frequency, 124 frequency lock loop (FLL), 83, 109 frequency shift keying (FSK), 83 image frequency, 151 Nyquist frequency, 117 resonant frequency, 10, 35 sum and difference frequency, 61 Gain, 67–, 132 processing gain, 95 unity loop gain, 111– Gate, 57 common gate, 67 dual gate see Transistor Generator: current generator, 13 ideal current generator, 34 Germanium, 49 Ghosting, 91, 196 Gilbert cell, 66, 76 GSM (global system mobile), 169 Harmonics, 17, 51, 206 Heat sink, 131 Henry, 8 Hertz, 5 hfe, hFE, 54 Hilbert see Transformer Hole, 49 Hybrid, 40– IF see Intermediate frequency Image see Frequency Impedance, 9 characteristic impedance, 18, 34, 199 impedance transformation, 23 input impedance, 74, 146 output impedance, 74 source impedance, 18 Inductance, 8 leakage inductance, 24, 25 mutual inductance, 14 primary inductance, 25 276 Index self inductance, 1, 2 stray inductance, 144 Inductor, 6–, 126 pot core inductor, 34 Insertion loss see Loss Insulator, 1–, 4 Interlacing, 89 Intermediate frequency, 64, 66 intermediate frequency amplifier, 153 Intermodulation, 26, 62, 151, 206 reverse intermodulation, 147 third order intermodulation, 206 Interference: intersymbol interference (ISI), 84, 85, 167, 178, 202 Intrinsic see Silicon ITU, 198, 261, 264 Inverse square law, 172 Ionosphere, 176 ISB see Sideband ISI see Interference ISM, 179 Isolation, 23, 42, 200 reverse isolation, 71, 75 Isolator, 45 Isotropic, 181 radiator, 171 ITA2, ITA5, 84 Jammer, 82 Jitter, 85 Joule, 1, 5, 8 k see Coupling Keying: frequency exchange keying (FEK), 84 minimum shift keying (MSK), 85 Gaussian filtered minimum shift keying (GMSK), 88 on off keying (OOK), 84, 91 phase shift keying (PSK), 84 quadrature phase shift keying (QPSK), 85, 90 offset phase shift keying (OQPSK), 88 Lambda λ see Wavelength Lenz law, 8 Leveller, 123 Lifetime, 51 Limiting, 76 Linearity, 2, 59 Line see Transmission line LO see Oscillator Local oscillator see Oscillator Lobes, 182 sidelobes, 196 Logarithm, 18 logarithmic mode, 157 Loss: absorption loss, 254 conversion loss, 64 insertion loss, 27 path loss, 173 reflection loss, 254 return loss, 46 Magnetic field see Field Magnetising current see Current Manganin, 1 Matching, 18, 73, 226 input matching, 140– Maxwell, 181, 213 Measurements: bridging, 204 through, 204 Memory: first in first out memory (FIFO), 94 read only memory (ROM), 115 Mesh see Delta Meteorscatter, 178 Microstrip, 44 Mismatching, 35, 70 minloss mismatch pad, 201 mismatch pad, 200 Mixer, 64– image reject mixer, 166, 168 MMF, 6 Modulation, 76, 78– cross modulation, 153 frequency modulation (FM), 78– modulation classification, 236 modulation index, 79, 210 modulation meter, 205 serasoidal modulation, 148 SSB modulation, 78, 154 Modulus, 10 Monopole see Antenna MPEG (motion picture experts group), 91 MUF, 176 Inductance, (Contd) Index 277 MUSIC, 197 Mutual conductance see Conductance Neper, 18, 199 Network: constant resistance network, 202 cross-over network, 202 network analyser, 207 Neutralisation, 70 NICAM, 85, 90 Nichrome, 1 Noise, 72, 96, 109 external noise, 261 galactic noise, 179 man-made noise, 179 noise figure, 73, 75, 154 phase noise, 205 thermal noise, 73 Normalise, 20 Nulls, 188 Nyquist: Nyquist diagram, 112 Nyquist sampling criterion, 168 OBW see Bandwidth OFDM (orthogonal frequency division multiplex), 91 Ohm’s law, 1 Oscillator, 96– Butler oscillator, 101 Clapp oscillator, 99 class D oscillator, 103 Colpitts oscillator, 98 electron coupled oscillator, 99 Franklin oscillator, 101 Hartley oscillator, 98 local oscillator (LO), 59, 64, 66 Meissner oscillator, 100 negative resistance oscillator, 106 OCXO, 15, 102 Pierce oscillator, 99 quench oscillator, 157 squegging oscillator, 158 TATG, 100 TCXO, 15, 102 Vakar oscillator, 103 voltage controlled oscillator, 111, 112 Oscilloscope, 209 Overtone see Harmonic OWF, 176 π see Attenuator PA see Amplifier Pads, 124, 199–, 225 Parameters: hybrid parameters, 54– s parameters, 54, 220 Passband, 11, 35 Pentode, 54, 59 PEP peak envelope power, 154 Permeability, 7, 37 Permitivity, 4 relative, 5 Phase, 10, 69, 76 antiphase, 19 phase equalizer, 202 phase lock loop, 76, 85, 89, 107 phase noise see Noise phase rotation, 165 shift, 5, 8, 57 Piezo electric, 16 Piccolo, 95 PLL see Phase lock loop PM see Modulation PMR (private mobile radio), 109, 119 Polarization, 171, 181 circular polarization, 191 Polyphase network, 76 Polystyrene, 6 Power, 1 maximum power theorem, 18 power meter, 204 power spectral density, 81 Poynting vector, 195 PRBS: pseudo random bit sequence, 94, 95 Pre-amble, 85 Pre-emphasis, 79 Propagation, 171– power constant, 18 PSD see Power spectral density Pseudo Brewster angle, 186 PTFE, 27 Push-pull see Signal Q (quality factor), 9, 11, 17, 27, 51, 69, 98, 112, 125, 141, 171, 191, 227 QPSK see Keying Quartz see Crystal Radar, 76 278 Index Radian, 11, 18 Radiation: isotropic radiation, 171 radiation pattern, 181 radiation resistance, 181, 190 Radio horizon, 174 Ratio: signal to noise ratio see SNR turns ratio, 25 Rays see Wavefront Reactance, 5, 8 Received signal strength indication (RSSI), 76, 169 Receiver, 148– homodyne receiver, 154–, 169 GPS receiver, 191 panoramic receiver, 205 superheterodyne receiver, 151 super-regenerative receiver, 154 synchrodyne receiver, 154 Reflections, 196 Reluctance, 7, 8 Resistance, 1– constant resistance network, 202 incremental resistance, 50, 52 internal resistance, 18 negative resistance, 71, 106 slope resistance, 50 thermal resistance, 132 Resistivity, 1– Resistor, 1– variable, 2, 51 Resonance see Tuned circuit Ring mixer see Mixer RSSI see Received signal strength indication Ruthroff, 36 Sample, sampling: Subsampling, 168 Saturation, 63 saturation voltage Vsat, 127 Servo: bang-bang servo, 115 Short range devices, 268 Sideband(s), 78, 82, 85, 96, 109 independent sideband (ISB), 78, 167 Sidelobes see Lobes SIDs, 177 Signal: common mode signal, 184 push-pull signal, 184 signal generator, 208 signal to noise ratio, 179 Silicon, 49 intrinsic silicon, 49, 51 silicon dioxide, 59 SINAD: signal to noise and distortion, 154 SITs, 178 Skin effect, 9, 19 Skip distance, 176 Smith chart, 20, 127, 145, 146, 207, 215 SNR see Signal to noise ratio Solenoid, 6 Source, 57– matched source, 34 S parameters see Parameters Spectrum: spectrum analyser, 82, 117, 144, 205 spectrum occupancy, 78 spread spectrum (SS), 94 direct sequence spread spectrum (DS), 95, 179 frequency hopping spread spectrum (FH), 94 sync spectrum, 91 Splitter, 40 Spurious (spur), 115, 148 spurious response, 64, 151 Squegging, 158, 209 SRDF, 197 SSB see Modulation Stability, 142– Star, 2, 215 Store-and-forward, 179 Stripline, 44 Substrate, 59 Sunspot cycle, 176 Superheterodyne see Receiver Susceptance, 5, 8, 67 Synthesizer, 112 direct digital synthesizer, 115 Take-off angle, 188 TDMA, 169 Tee see Attenuator Teletext, 90 Television: NTSC, PAL, SECAM, 89 Temperature: temperature coefficient (tempco), 34, 52, 97 temperature inversion, 175 Index 279 Terman, 14 Theorem: maximum power theorem, 18, 215 TIDs, 178 Time: attack- hold- decay-time, 154 revisit time, 82 time constant, 79, 85 Tissue: photographic mounting tissue, 27 Top loading, 186 Toroid, 7 Transformer, 9 balun transformer, 35, 37, 184 Hilbert transformer, 167 inverting transformer, 37 line transformer, 36 matching transformer, 23 quarter wave transformer, 20 r.f. transformer, 23– Transistor, 52– field effect transistor (FET): junction FET, 57– MOSFET, 59, 134 dual gate MOSFET, 59, 71 Transmission: transmission line, 18–, 37 balanced transmission line, 18 unbalanced transmission line, 18 Transmitter, 148– spark transmitter, 96 Triode, 59 Trombone, 145 Troposcatter, 178 Tuned circuit, 11, 69 parallel tuned circuit, 13 series tuned circuit, 13, 17 stagger tuned circuit, 11 synchronously tuned circuit, 11 tank tuned circuit, 63 Turns ratio see Ratio Unilateralisation, 70 Vacuum, 4 Varactor see Diode (varicap) VDE, 210, 211 Voltage: breakdown voltage, 128 pinch-off voltage, 57, 57 voltage standing wave ratio see VSWR VSWR, 20, 22, 64–66, 123, 182, 226 Watt, 1 Wave: carrier wave, 78 continuous wave (CW), 78 ground wave, 175 incident wave, 19 reflected wave, 19 sky wave, 196 wavefront, 172, 188, 197 wavelength, 18, 37 Weber, 7, 8 Winding: primary, 23 secondary, 23 Wire: enamelled wire, 27 wire gauges, 232 Wullenweber array, 196 Wye see Star Yagi see Antenna