1、i 1 - EIA 252-A 72 3234600 0063538 8 -I EIA STANDARD Standard Microwave Transmission Sy s terns RSm252-A (Revision of RS-252 and RS-203) Sep tem ber 1972 Engineerng Department ELECTRONIC INDUSTRIES ASSOCIATION NOTICE EIA engineering standards are designed to serve the public interest through elimina
2、ting mis- understandings between manufacturers and purchasers, facilitating interchangeabiiity and improve- ment of products, and assisting the purchaser in selecting and obtaining with minimum delay the proper product for his particular need. Existence of such standards shall not in any respect pre
3、- clude any member or non-member of XIA from manufacturing or selling products not conformin to such standards, nor shall the existence of such standards preclude their voluntary use by those o ill er than EIA members whether the standard is to be used either domestically or internationally. Recomme
4、nded standards are adopted by EIA without regard to whether or not their adoption may involve patents on articles, materials, or processes. By such action, EU does not assume any liability to any patent owner, nor does it assume any obligation whatever to parties adopting the recommended standards.
5、Published by ELECTRONIC INDUSTRIES ASSOCIATION 6- 7 * EIA 252-A 72 3234b00 00b3539 T Engineering Department 2001 Eye Street, N.W., Washington, D. C. 20006 Electronic Industries Association 1972 Ail rights reserved PRICE: $6.50 Printed in U.S.A. EIA 252-A 72 M 3234600 O063540 6 M RS-2524 Page 1 STAND
6、ARD MICROWAVE TRANSMISSION SYSTEMS (From EIA Standards RS-203 and 252. and Standards Proposal No . 11 19. formulated under the cognizance of EIA Subcommittee TR-14.1 on Microwave Equipment) Page 1 . GENERAL SYSTEM CHARACTERISTICS . 4 1.1 Antennasubsystems 4 1.2 BranchingNetwork . 5 1.4 Receiving Sub
7、system . 5 1.6 Bandwidth, RF Channel . 6 1.7 Bandwidth, Transmitted Spectrum . 6 1.8 Bandwidth. Receiving System 6 1.9 CrossCoupling 6 . 1.3 Transmitting Subsystem . 5 1.5 Bandwidth, Authorized Channel 5 1.10 RF Gain. Radio Equipment 7 1.1 1 Power of Transmitting Subsystems. Rated . 7 1.12 Minimum U
8、sable Signal. Receiver 7 1.13 Selectivity. Receiver Subsystem 7 1.14 Transmission Gain . 8 1.15 Test Tone. Standard . 8 2 . MODULATION CHARACTERISTICS . 8 2.1 Frequency Modulation 8 2.2 PhaseModulation 9 2.3 PulseModulation 9 2.4 Test Tone Deviation (Per Channel Deviation) . 9 2.5 SystemLoading . 10
9、 2.6 RF Carrier RMS Deviation . 11 2.7 RF Carrier Peak Deviation . 11 2.8 Modulation Index . 11 2.9 Deviation Ratio . 12 2.1 O Pre-Emphasis/De-Emphasis . 12 3 . BASEBAND CHARACTERISTICS 12 3.1 Baseband . 12 3.2 BasebandTerminal . 13 3.3 Baseband Input and Output Impedances 13 3.4 Transmission Gain S
10、tability . 13 3.5 Amplitude-Frequency Response Characteristics . 14 3.6 Signal to Noise Ratio (Voice Channel) 14 3.7 Baseband Envelope Delay Distortion . 15 3.8 TransmissionTime 15 a . O . . 1 Page * #* EIA 252-A 72 w 3234b00 00b354L RS-252-A Page 2 4 . TRANSMISSION PATH CHARACTERISTICS . 15 4.1 Mic
11、rowave Transmission Path . 15 4.2 Obstruction 16 4.3 Reflection Surface . 16 4.4 Clearance . 16 4.5 First Fresnel Radius . 17 4.6 Effective Earth Radius and K Factor 17 4.7 PathLength 18 4.9 Obstruction Loss 18 4.10 Reflection Loss (Gain) . 19 4.1 1 Fading Margin . 1.9 4.12 Normal Path Loss . 20 4.1
12、3 RF Transmission Loss . 20 4.14PathProfile . 21 4.15PathSurvey 21 5 . PHYSICAL PLANT DEFINITIONS . 21 5.1 Backbone 21 4.8 FreeSpaceLoss . 18 5.2 Center, Alarm . 22 5.3 Center, Alarm and Control . 22 5.4 Center, Control . 22 5.6 Channel, Insert 22 5.7 Channel, Supervisory . 22 5.8 Channel, Stop . 22
13、 5.9 Diplexer . 22 5.11 Diversity Operation 23 5.12 Equipment, Diversity . 23 5.14 Repeater, Passive 23 5.15 Station, Intermediate 23 5.16 Station, Junction 23 5.17 Station, Terminal 23 5.18 Site . 23 5.19Spur . 24 5.20 Emergency Power Supplies . i 24 5.2 1 Microwave Housing Facilities . 24 6 . DEFI
14、NITIONS FROM OTHER SOURCES . 24 6.1 Bandwidth 24 6.2 Beamwidth . 24 5.5 Channel, Drop 22 5.10Duplexer 22 5.13 Equipment, Standby . 23 6.3 CrossCoupling 24 6.4 Fresnel Zone, First . 24 6.5 Frequency, Assigned . 25 . EIA 252-A 32 3234600 0063542 T = 4 RS-252-A Page 3 Page 6.6 Frequency. Reference 25 6
15、.7 Frequency. Tolerance . 25 6.8 Radiation. Leakage . 25 6.9 Repeater . 25 6.10SpuriousRadiation . 26 6.11SpuriousResponse . 26 6.12Terminating 26 28 Appendix II - Pre-emphasis/De-emphasis . 30 Appendix III - Noise Analysis 35 Appendix IV - Path Climatology and Effective Earth Radius Factor . 41 App
16、endix I - Methods to Measure the Bandwidth of a Transmitted Spectrum II 7 -y / RS-252-A Page 4 EIA 252-A 72 m 3234b00 00b3543 I m INTRODUCTION AND SCOPE This standard applies to microwave relay communication systems. Usually these systems are multi- hop. They transmit intelligence initially derived
17、from speech, telegraph, data, facsimile, etc., all multiplexed on the radio baseband. Relay systems exclusively for broadcast material are excluded, and are covered by EIA Standard RS-250-A. The standard includes only the system from the baseband input terminals to the baseband output ter- minals an
18、d does not include the multiplex equipment, which is dealt with in a separate standard. It does, however, include the transmission mad c, ium. While it may not be possible to specify actual minimum performance numbers, it wil serve as a stan- dard of terminology and a guide toward detailed specifica
19、tions, Definitions of pertinent systems pa- rameters are given and methods of measurement are included. Thus, the emphasis has been toward establishing a common language and defining certain reference points in the system. Terminology al- ready established by standards and regulatory organizations h
20、as been used wherever applicable. NOTE: This standard deals primarily with analog microwave systems using angle modulation. It should be noted that a number of definitions may not be applicable to systems using digital modulation techniques such as PCM. 1. GENERAL SYSTEM CHARACTERISTICS 1.1 Antenna
21、Subsystems 1.1.1 Definition: The antenna subsystem comprises all those fabricated components involved in the conversion of confined electromagnetic energy to space radiation along the microwave trans- mission path or vice versa. NOTE: The antenna subsystem includes radiating elements, reflectors, tr
22、ansmission lines and other such components necessary for the formation of directed space radiation which are not normally a part of the radio transmitting and receiving subsystems. The electrical and mechanical characteristics of antenna and passive reflector assemblies for microwave radio relay app
23、lications are covered in RS-195-A. The structural standards for steel antenna towers and antenna supporting structures are covered in RS-222-A. Transmission line standards are given in: RS-200-A Circular Waveguides RS-25 8 RS-25 9 RS-26 1-A Rectangular Waveguides (WR3-WR2300) RS-27 1-A Semi-flexible
24、 Air Dielectric Coaxial Cables and Connectors, 500 Rigid Coaxial Transmission Lines and Connectors Waveguide Flanges-Pressurizeable Contact Types for Waveguide Sizes WR 90 - WR 2300 - e -. EIA 252-A 72 m 3234600 O063544 3 m RS-252-A Page 5 RS-285 RS-3 04 Ridge Waveguides RS-225 50 ohm Coaxial Lines
25、RS- 199 Solid Dielectric Coaxial Lines RS-166 Miniature Waveguide Flanges Waveguide Flanges - Dual Contact Pressurizeable and Miniature Type for Waveguide Sizes WR 90 - WR 975 1.1.2 Standard. Not applicable. 1.1.3 Method of Measurement. Not applicable. 1.2 Branching Network 1.2.1 Definition: The bra
26、nching network includes filters, isolators, circulators, etc., necessary for transmission and reception of one or more RF channels on the same antenna. 1.2.2 Standard. Not applicable. 1.2.3 Method of Measurement. Not applicable. 1.3 Transmitting Subsystem 1.3.1 Definition: The transmitting subsystem
27、 comprises all components involved in the form tion of the modulated microwave carrier to be transmitted, including that portion of the branching network (a branching section) specifically associated with each transmitter. 1.3.2 Standard. Not applicable. 1.3.3 Method of Measurement. Not applicable.
28、O 1.4 Receiving Subsystem 1.4.1 Definition: The receiving subsystem comprises all components, including that portion of the branching network (a branching section) specifically associated with each receiver, involved in the processing of the received microwave carrier, including demodulation equipme
29、nt where applicable. 1.4.2 Standard. Not applicable. 1.4.3 Method of Measurement. Not applicable. 1.5 Bandwidth, Authorized Channel 1.5.1 Definition: The authorized channel bandwidth is that portion of the radio frequency spectrum between two limiting frequencies within which one way transmission is
30、 authorized by the appropriate regulatory body. EIA 252-A 72 m 3234b00 00b3545 5 m c RS-252-A Page 6 1.6 1.7 1.8 1.9 1.5.2 Standard. Not applicable. 1.5.3 Method of measurement. Not applicable. Bandwidth; RF Channel 1.6.1 Definition: The minimum value of bandwidth sufficient to ensure the transmissi
31、on of information at the rate and with the quality required, for the system employed. (Paraphrase of Necessary Bandwidth from FCC Rule 2.202b.) 1.6.2 Standard: The bandwidth shall be stated in MHz. 1.6.3 Method of Measurement: Deferred. Bandwidth, Transmitted Spectrum 1.7.1 Definition: The transmitt
32、ed spectrum bandwidth is that portion of the radio frequency spectrum between two limiting frequencies encompassing a specified percentage of the total radiated power. 1.7.2 Standard: Shall be expressed in megahertz such that, below its lower and above its upper frequency limits, the mean powers rad
33、iated are each equal to 0.5 percent of the total mean power radiated by a given emission. (Paraphrase of “Occupied Bandwidths as defined in FCC Rules 2.202a.) 1.7.3 Method of Measurement: See Appendix I. Bandwidth, Receiving System 1.8.1 Definition: The bandwidth of a microwave communication receive
34、r is the difference be- tween the limiting frequencies at which the signal presented to the demodulator is lower by a specified amount than that presented at the center frequency, assuming no amplitude limiting. 1.8.2 Standard: Shall be stated in megahertz for the frequency difference between the li
35、miting frequencies at which the response is 3 dB down, unless otherwise noted. 1.8.3 Method of Measurement: Deferred. Cross Coupling 1.9.1 Definition: Cross coupling is the level of modulation cross-talk between two different communication channels. 1.9.2 Standard: Shall be expressed as the level di
36、fference, in dB, between the modulation signal level on one channel and the modulation signal level caused by crosstalk coming from the other communication channel. 0 EIA 252-A 72 m 3234600 0063546 7 W 1.9.3 Method of Measurement: Deferred. 1.1 O RF Gain, Radio Equipment 1.1 O. 1 Definition: Radio e
37、quipment gain is the ratio of the rated power of the transmitter sub- system to the required receiver subsystem input power for minimum usable performance. I. 10.2 Standard: Shall be expressed in dB. 1.10.3 Method of Measurement: By calculation from the two quantities used. 1.1 1 Power of Transmitti
38、ng Subsystems, Rated 1.1 1.1 Definition: The rated power of the transmitting subsystem is the minimum radio fre- quency output power specified by the manufacturer. 1.1 1.2 Standard: Shall be specified in watts when terminated in the rated load impedance, in terms of peak power for amplitude pulsed e
39、missions, or average power for amplitude, fre- quency, or phase modulated emissions. 1.1 1.3 Method of Measurement. Deferred. 1.12 Minimum Usable Signal, Receiver 1.12.1 Definition: The minimum usable signal of a radio receiver or similar device is taken as the minimum input signal required to produ
40、ce an output signal of minimum usable perfor- mance. Minimum usable performance depends upon the type of information being transmitted and the intended quality of service, and is usually defined in terms of a limiting signal to noise ratio. 1.12.2 Standard: Unless otherwise specified, the receiver s
41、ubsystem minimum usable signal shail be specified in dBm (in terms of peak power for amplitude pulsed emissions, or average power for amplitude, frequency or phase modulated emissions) as the power input to the re- ceiver subsystem (terminated in its rated load impedance) resulting in minimum usable
42、 per- formance. 1.12.3 Method of Measurement. Deferred. 1.13 Selectivity, Receiver Subsystem 1.13.1 Definition: The selectivity of a microwave communication receiver is the degree to which it is capable of discriminating between the desired signal, and unwanted signals or inter- ference at other fre
43、quencies. (See also ANSI 65.08.065). 1.13.2 Standard: Shall be expressed as a curve of the response in dB versus frequency relative to the center frequency response carried to include frequencies at least three receiver band- widths above and below the design center frequency. For simplified tabular
44、 presentation, may o - . RS-2524 Page 7 EIA 252-A 72 = 3234b00 00b3547 9 1 RS-252-A Page 8 be expressed as the receiver bandwidth and the response relative to the center frequency at fre- quencies f 1, f 2, and f 3 bandwidths from the design center frequency. 1.13.3 Method of Measurement. Deferred.
45、1.14 Transmission Gain i. 14.1 Definition: The transmission gain 0f.a microwave communications system is the ratio of the output baseband signal level to the input baseband signal level expressed in dB. NOTE: Transmission gain is of importance for determining conformation to specified test tone leve
46、ls at the baseband input and output, or for determining the necessity for interface amplification or attenuation to other systems. 1.14.2 Standard: Shall be expressed as power gain in dB, and baseband input and output im- pedances in ohms shall also be stated. 1.14.3 Method of Measurement: Deferred.
47、 1.15 Test Tone, Standard 1.15.1 Definition: In a telephone channel at audio frequency, a 1 kHz sinusoidal tone. At a zero transmission level point (O TLP) the tone has a level of O dBm. (The toll test board of the central office where the channel originates is usually a O TLP). At other points the
48、level of the tone WU vary; i.e., at a +7 TLP the level is +7 dBm. NOTE: When the telephone channel is translated in frequency, as in frequency division multiplex, the frequency of the test tone will be translated correspondingly. When the format of the telephone channel undergoes translation, so tha
49、t after translation some other quantity corresponds to instantaneous voltage before translation, then the test tone .format is also translated, For example, when the channel is translated to FM on a CW carrier, test tone level is stated not in RMS volts but in corresponding units of frequency :i deviation as RMS kHz. 1.15.2 Standard: Not applicable. 1.15.3 Method of Measurement: Not applicable. 2. MODULATION CHARACTERISTICS 2.1 Frequency Modulation 2.1.1 Definition: Frequency Modulation (FM) is that process of angle modulation in which the instantaneous frequency deviat
