1、AECMA STANDARD NORME AECMA AECMA NORM prEN 2591-221 Edition P 1 February 2005PUBLISHED BY THE EUROPEAN ASSOCIATION OF AEROSPACE INDUSTRIES - STANDARDIZATION Gulledelle 94 - B-1200 Brussels - Tel. + 32 2 775 8110 - Fax. + 32 2 775 8111 - www.aecma-stan.orgICS: Descriptors: ENGLISH VERSION Aerospace s
2、eries Elements of electrical and optical connection Test methods Part 221: Voltage Standing Wave Ratio (VSWR) Srie arospatiale Organes de connexion lectrique et optique Mthodes dessais Partie 221 : Ratio dOndes Stationnaires Luft- und Raumfahrt Elektrische und optische Verbindungselemente Prfverfahr
3、en Teil 221: StehwellenverhltnisThis “Aerospace Series“ Prestandard has been drawn up under the responsibility of AECMA-STAN (The European Association of Aerospace Industries - Standardization). It is published for the needs of the European Aerospace Industry. It has been technically approved by the
4、 experts of the concerned Domain following member comments. Subsequent to the publication of this Prestandard, the technical content shall not be changed to an extent that interchangeability is affected, physically or functionally, without re-identification of the standard. After examination and rev
5、iew by users and formal agreement of AECMA-STAN, it will be submitted as a draft European Standard (prEN) to CEN (European Committee for Standardization) for formal vote and transformation to full European Standard (EN). The CEN national members have then to implement the EN at national level by giv
6、ing the EN the status of a national standard and by withdrawing any national standards conflicting with the EN. Edition approved for publication 28 February 2005Comments should be sent within six months after the date of publication to AECMA-STAN Electrical Domain Copyright 2005 by AECMA-STAN Page 2
7、 prEN 2591-221:2005Foreword This standard was reviewed by the Domain Technical Coordinator of AECMA-STANs Electrical Domain. After inquiries and votes carried out in accordance with the rules of AECMA-STAN defined in AECMA-STANs General Process Manual, this standard has received approval for Publica
8、tion. Contents Page 1 Scope 3 2 Normative references. 3 3 Preparation of specimens. 3 4 Apparatus 4 5 Procedure 5 6 Requirement . 5 7 Detail to be specified 5 Annex A (normative) Definition of S parameters 7 Page 3 prEN 2591-221:20051 Scope This standard specifies a measurement method of VSWR, in th
9、e required frequency bandwith of coax contacts or connectors with characteristic impedance. It shall be used together with EN 2591-100. The measurement is carried out according to vectorial method using “S” parameters (see definition in Annex A). 2 Normative references The following referenced docum
10、ents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 2591-100, Aerospace series Elements of electrical and optical connection Tes
11、t methods Part 100: General 1)3 Preparation of specimens Method “A” This method is applicable when exist accurate adapter in the series of connectors or contacts to tested. The sampling shall include, for each specified cable, one section of coaxial cable with device under test in both ends. The sec
12、tion is constituted as follow (see Figure 1): 60 cm 2,5 mm of coaxial cable 1 male coaxial device 1 female coaxial device Key 1 Male coaxial device 2 Female coaxial device 3 Coaxial cable; Lg. = 60 cm 2,5 mm Figure 1 1) Published as AECMA Prestandard at the date of publication of this standard 1 2 3
13、Page 4 prEN 2591-221:2005Method “B” This method is applicable when exist accurate adapter in the series of connectors or contacts to tested. The sampling shall include for each specified cable, one section of coaxial cable with standard connectors in both end, and device under test in the middle of
14、the section of the cable. The section is constituted as follow (see Figure 2): 60 cm 2,5 mm of coaxial cable divided in 2 (2 30 cm) 1 male coaxial standard connector (SMA, Nor TNC type ) 1 female coaxial standard connector (SMA, Nor TNC type ) 1 male coaxial device 1 female coaxial device Key 1 Coax
15、ial (Std) male connector 2 Device under test 3 Coaxial (Std) female connector 4 Coaxial cable; Lg. = 2 30 cm 2,5 mm Figure 2 4 Apparatus The apparatus shall comprise: Measure equipment include (see Figure 3): vector network analyser calibration kit standard precision adapters a 75 kit of transformat
16、ion, to perform measurement from 50 network analyser, when it is necessary. 3 41 4 2Page 5 prEN 2591-221:20055 Procedure 5.1 Calibration Select measure frequency range and sampling points number. Carry out the complete calibration of network analyse, Part 1 and Part 2 (“S” Parameters, S11, S12, S21a
17、nd S22) Using calibration kit according to instructions specified by network analyser manufacturer. 5.2 Measurement Method A Connect the section in measure on network analyser, using if necessary, standards accurate adapters, and perform the measurement. The VSWR of one connector is determined by us
18、ing the temporal response (time domain) and a function called “GATE” to isolate the connector, which must be connected to the standard precision adapter. Method B Connect the section in measure on network analyser, using if necessary standards accurate adapters, and perform measurement. The VSWR of
19、the two mated connectors is determined by using the temporal response (time domain) and a function called “GATE” to isolate the two mated connectors from the coaxial cable. 6 Requirement The Voltage Standing Wave Ratio (VSWR) does not exceed specified values on the product standard. 7 Detail to be s
20、pecified The following items shall be specified: coaxial cables part number standard coaxial connectors part number network analyser, manufacturer, type and serial number frequency range sampling point number standard precision adapter part number measurement impedance (50 or 75 ) for coaxial contac
21、t, connection length wiring instruction and tooling for thread coupling connectors, the coupling torque of the coupling ring Page 6 prEN 2591-221:2005Key 1 Vector network analyser 2 RF generator and “S” parameter test set Legend Precision hermaphroditic connectors Standard Precision Adapters Figure
22、3 Hermaphrodite Interface Standard Coaxial Connector Interface Device Under Test Interface 1 2 Page 7 prEN 2591-221:2005 Annex A (normative) Definition of S parameters A.1 Effective Power of a Sinusoidal source Consider an E.M.F. source, E, measured in Vrmswith an internal impedance Zgand a load imp
23、edance Z. The applied power P dissipated in Z is defined as () ()Z eZZE*Z*Z*EZZZEe*I V e Pggg+=+=22)()(P is a maximum when *ZZg= (balanced load). This maximum power is known as the effective or RMS nota Root Mean Squared power for a given source (E, Zg) and can be expressed as Prms= )(2gdZeEP=4In ge
24、neral, when Z has a different value to Zg, we define P as +=221)(gggZZ*Z-ZZeEP4where ggZZ*ZZ+is known as the Power Reflection Coefficient. The power dissipated in Z can be expressed as the difference of two powers, and when the source (E, Zg) power is maximum and when Z Zg, the amount of power refle
25、cted towards the source is equal to 2ggZZ*Z-Z+Page 8 prEN 2591-221:2005A.2 Waves Incident and Reflected (Kurokawa Waves) Let us define an impedance, Z, in terms of a potential difference, V, and a current I. We also define an Incident Wave, a, and a Reflected Wave, b, with respect to a Reference Res
26、istance, Rg, as follows: the power dissipated in Z = P = |a|2 |b|2 the effective power generated by the source (E, Rg) = Prms= |a|2Expressing a and b in terms of V, I, Rg, gives: ggRI R Va2+= ggRI R Vb2= If Z is supplied by the source (E, Rg) we can state that E = V + Rg.I which automatically valida
27、tes Prms = |a|2. NOTE - Rgis known as the Reference Resistance for the “waves“ a and b - The word wave is written inside speech marks because a and b do not show the typical electromagnetic behaviour associated with classical waves they are rather Power Waves - The definition of a and b is independe
28、nt of that fact that the dipole Z is fed by a source of an internal resistance Rg- The power dissipated in Z is independent of the characteristics of the source and is always equal to |a|2|b|2- The ratio of the waves b to a is equal to (when V = Z.I) ggR ZR - Zab+= which is the Reflection Coefficien
29、t of the impedance Z with respect to the reference resistance Rg. Page 9 prEN 2591-221:2005A.3 S Parameters of a quad pole Let us apply the precedent definition to the input and output of a quad pole device. This time we define an incident and reflected wave, a1and b1, for the input side and inciden
30、t and reflected wave, a2and b2, for the output side, relative to the input and output reference resistances, R1and R2. 111112 R I RVa+= 222222 R I RVa+= 111112 R I RVb= 222222 R I RVb= We can state that the system is linear and we can therefore re-write the above equations to express on variable in
31、function of two of the other unknowns. b1= S11 a1+ S12 a2b2= S21 a1+ S22 a2These S Parameters are also known as the system distribution parameters and characterise the quad pole in function of its input and output reference resistances, R1and R2. NOTE These S Parameters define the quad pole at a giv
32、en frequency A.4 Physical Signification and Interest of S Parameters A.4.1 Physical significance of S11If S11= b1/a1, where a2= 0, then a2is equivalent to V2= R2.I2, the output of the quad pole is therefore closed loop on R2and if Zeis the input impedance of Q, then in these conditions, we can state
33、 that V1 = Ze.I1and S11is the input reflection coefficient with respect to R1when the output impedance = R2. 1111RZRZSee+=Page 10 prEN 2591-221:2005A.4.2 Physical significance of S22In the same way, if S22= b2/a2then when a1= 0, the input is closed loop on R1and under these conditions if Zois the ou
34、tput impedance, we obtain S22is the input reflection coefficient with respect to R2when the input impedance = R1. The Smmparameters are therefore defined as the Reflection Coefficients. A.4.3 Physical significance of S21If S21= b2/a1then when a2= 0, the output is closed loop on R2and therefore 11122
35、2211221IRVIRVRRabS+= If we assume that the quad pole Q is supplied by a source (E, R1) then E = V1+ R1.I1and V2= R2.I2The quad pole being supplied by a source of impedance R1and with a load R2will have a S Parameter S21proportional to a voltage gain called the System Transmission Coefficient. If we
36、take the square of S21then we obtain )/12122221222221RMS PowerinRMS Power 44R (E, R RERVRREVS = where |S21|2is the Composite Power Gain. 2222RZRZSss+=EVRRS221212=Page 11 prEN 2591-221:2005A.4.4 Physical significance of S12We can do a similar calculation as above and we will find that, for a quad pol
37、e Q supplied by a source (E, R2) and whose input is closed loop on R1, the S12parameter is defined by EVRRS112212= S21is called the Inverse Transmission Coefficient. These S Parameters are used to characterise the junctions in high frequency applications because they possess a number of advantages:
38、these parameters are measurable at R1and R2. In practice we choose standard values for resistances R1and R2such as 50 ohms or 75 ohms. It is much easier to measure variables over a known resistance than on an open circuit (Z Parameters) or in a short circuit (Y Parameters). in closing each side of t
39、he circuit allows frequency sweeping. as the termination resistances R1and R2are dissipative, the risks of instability during the analysis of the active quad pole are decreased (which is not the case for open or short-circuits). a simple device already exists to separate a and b waves at high frequencies. This device is the directional coupler.
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