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1、F- e EIA TEP171 7 2 = 3234600 0008488 Fe b. 1972 Recommended Practice for Measurement here the radiation leakage problem is really one of equipment design. Hicrowave energy leaking from a small aperture h a microwave enclosure radiates in accordance withMaxwells equations. equations governkg such le
2、akage, it can be shorn that the energy is stored b the media in the vichity of the leak in two forms; (a) a radiative term whose field intensity varies inversely as the first power of range from the leakage source, and (b) reactive t e r m s whose htensities decrease more rapidly with distance from
3、the source. As the size of the leakage aperture increases and becomes significant- relative t o the microwave wavelength, the manner of variation of field Intensity of the radiative tern must also include the effect of the relative phase of excitation from discrete elements within the aperture and t
4、he effect of wavefront curvature. case, the radiative field w i l l not vary inversely with range from the aperture until the range exceeds Since microwave tubes are most frequently operated with planar triodes, From a study of the Thus, for the large aperture where: D = major dimension of the apert
5、ure Copyright Electronic Components, Assemblies ions+ delivers m o r e Chan 1 / 4 watts of average pawer through i t s normal rf output connection, it is recornended that - a l l the caution mechanisms shown below be used: r l _ _ _ _ _ Copyright Electronic Components, Assemblies IS FNERGZED. ALL IN
6、PUT RF LEAK PROOF AND mZ0PERL;Y EXAGED. NEVER OPBUTE THIS DEVICE WXTH(BPT NEVER M O 9 c INTO AN OPW 9.0 REFERENCES 9,l Proceedings of the IRE, Vol. 49, No. 2, pp 427447, February 1961, Vorne Technical Aapects of Microwave Radiation Hazards W W . Mumford. 9 . 2 USAS C95.1-1966 “Safety Level of Electr
7、omagnetic Radiation (10 MHz to 100 GHz) with Respect t o Personnel. 9.8 USAS C95.2-1!366 !Radio-Frequency Radiation Hazard Warning Symbolll. . 9.4 Proceedings of the DEE, Bol. 57, No. 2, pp 171-178, February 1969. Heat Stress Due t o RF Radiationtt - W. W . MWop3. I “ Copyright Electronic Components
8、, Assemblies 4 t o I SMALL 6 t o I MEDIUM 4 . SYMBOL I S SQUARE, TRIANOLES ARE RIOHT-ANGLE ISOSCELES FIGRE 1 i - -xxI f Copyright Electronic Components, Assemblies (b) the best fit straight lhe, The maxiinum deviations between these curves should be within the linearity limits o Excursions through t
9、he power range should be repeated (a) one consisthg of a series of straight lines 4.0 SENSDIVlYY CALIBRATICM 4.1 With the instrument mounted as in 2.0 and the elevation angle adjusted so that the instrument axis is one proximity distance above the ground plane, adjust the sensor range t o a stated v
10、alue between Aand 3A . Then adjust frequencyto mid-band and input power to obtain f u l l scale hdication, thereafker holding both constant. Increment the elevation fmgle through severalostated values relative i o the antenna axis (usually So, 60, 450, 30, O , -30, 4 5 O , -60, -75 ) and reoard the
11、corres- ponding instrument indications. Then repeat with the instrument incre- mented through the same values for the orthogonal elevation axis. e / P Copyright Electronic Components, Assemblies Instrument is mounted as in 3.0 and input is adjusted t o provide EI stated known power density at the se
12、nsor. The detector (see note) is removed from the sensor (with the sensor remining in the same position), The actual power absorbed by the sensor is thtm measured by a power meter whose input impedance is idediGa1 to that of the detector. Dividing ( 3 . ) the measured power by (2) the stated power d
13、easity gives (3) the effective aperture of the instrument in square centimeters. N(YTE: Some instrumenta directly connect sensor and detector, When this - ia done, do not attempt t o measure effective aperture. 8.0 MAXIMM DIMENSI? OF TPHE: APEENJRE 8.1 The physical length of the langest element of t
14、he antenna is measured irect3.y or determined from an x-ray of the sensor. Materials which dielectrically load the sensor must be hcluded but non-participathg. materials can be excluded. 9.0 CALIBRATIW ACCURACY 9 . 1 The calibration error is the maximum value of the algebraic sum of the linearity er
15、ror (from 3 . 0 ) expressed Ul dB and the worst case correction factor K (from 4.0 and 5.0) expressed in B. Copyright Electronic Components, Assemblies & Materials Association Provided by IHS under license with ECA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 02:10
16、:41 MDTNo reproduction or networking permitted without license from IHS -,-,- a - 5 - 10,O DETERMINATION OF CALIBRATION INACCURACY ARISING FROM STRAY PICK-UP NOTE: Instruments which detect leakage energy by a sensor which is remote from the indicators generally w i l l have less difficulty from prox
17、imity 10.1 effects than those which combine indicator and sensor i n an integral arrangement. indicated value is derived from unintended coupling to the instrument. Since the effect of such coupling w i l l vary with the spatial d i s t r i - bution of the field being measured, the error introduced
18、by such unintended coupling cannot be calibrated out. As a consequence, a test for unintended leakage is important. When the indicator is seperate from the sensor, it is often necessary to cover connecting cables with lossy materials and to ensure that a l l openings be shielded or screened. Explore
19、 the field over an extensive polyethylene foam (or equivalent material of dielectric susceptibility approaching zero), and mark on the surface a constant energy density profile. sensor i n the normal manner at one end of the sector marked out. Then, i n turn, position the indicator box so that: a l
20、l its surfaces, i n turn, are parallel t o the constant energy profile and at least 30cm from the sensor. Likewise, expose a l l cables, line cords needed i n normal use, etc., at the same distance. Under no conditions shall the indicated value change by more than 1 dB. In either case, it is possibl
21、e that a portion of the men position the CAUTION: THIS MEASUREMENT CANNOT BE MADE TOO CLOSE TO THE SOURCE MONOPOLE OR REFLECTIONS FROM THE INDICATOR BOX MAY AFFECT FIELDS AT THE SENSOR. IF MOVEMENT OF THF, INDICATOR BOX TOWARD OR AWAY FROM THE SOURCE MONOPOLE CAUSES THE INDI- CATED FIELD STRENGTH To
22、 RISE AND FALL PERIODICALLY, SIMILAR TO A STANDING WAVE PATTERN, THE INDICATOR BOX IS TOO CLOSE TO THE SOURCE. 11.0 DETERMINATION OF RESPONSE TIME 11.1 Mount the sensor as i n 4.0. Adjust the power source to give f u l l scale indication on the test instrument and measure source power calorimetrical
23、ly. with nominally 10% duty. taining average power constant as determined calorimetrically by the water load. length increases until, at some pulse length, the indicated value is the stated portion of the true value (as determined by the calor- imeter). This value of pulse length, i n seconds, is th
24、e response t i m e , Then switch the power source for pulse service Gradually increase the pulse length, main- Indicated power density will increase as pulse Copyright Electronic Components, Assemblies & Materials Association Provided by IHS under license with ECA Licensee=IHS Employees/1111111001,
25、User=Wing, Bernie Not for Resale, 03/30/2007 02:10:41 MDTNo reproduction or networking permitted without license from IHS -,-,- E I A TEP171 72 = 323LlbOO 0008503 O t- P O W E R SOURCE NOTE : - - 6 - MEASURING INSTRUMEN: + DIRECT TONAL MATCHER GROUND PUNE RADIATOR COWLER I IL The power source should
26、 have provision t o vary power over more than a 10 dB range. of instrument response (paragraph 4.11) needs to be added. can be a clock driver timer, driven by a variable frequency os- cillator, which automatically adjusts pulse length t o produce a constant duty cycle. In addition, provision for mea
27、surement This FIG. 1 - BLOCK DIAGRAM OF P O W E R SYSTEM Copyright Electronic Components, Assemblies & Materials Association Provided by IHS under license with ECA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 03/30/2007 02:10:41 MDTNo reproduction or networking permitted without license from IHS -,-,-