1、CEPT T/R*i1,35 n 81.35 n Cable to the measuring 0 receiver Ceiling - c 1f2 -i- 3-4 l hl m Absorbant material Reference point of the equipment under test 1- 0,75 hz I I I -L m / Wall Floor Figure 1 (TIR 20-04). Indoor site arrangement (shown for horizontal polarization). The potential reflections fro
2、m the wall behind the equipment under test are reduced by placing a barrier of absorbent material in front of it. The corner reflector around the test antenna is used to reduce the effect of reflections from the opposite wall and from the floor and ceiling in the case of horizontally polarized measu
3、rements. Similarly, the comer reflector reduces the effects of reflections from the side walls for vertically polarized measurements. For measurements in the lower part of the frequency range (below approx. 175 MHz) no corner reflector or absorbent barrier is needed. For measurements in the higher p
4、art of the frequency range, no corner reflector is needed if use is made of a horn radiator or a parabolic antenna. For practical reasons, the h/2 antenna in Figure 1 (T/R 20-03) may be replaced by an antenna of constant length, allowing it to be used at frequencies corresponding to a length between
5、 h/4 and h, as long as the sensitivity is sufficient. In the same way the distance of h/2 to the apex may be varied. The test antenna, test receiver, substitution antenna and calibrated signal generator are used in a way similar to the general method. To ensure that errors are not caused by the prop
6、agation path approaching the point at which phase cancellation between direct and the remaining reflected signals occurs, the substitution antenna shall be moved through a distance of f 10 cm in the direction of the test antenna as well as in the two directions perpendicular to this first direction.
7、 If these changes of distance cause a signal change of greater than 2 dB, the test sample should be resited until a change of less than 2 dB is obtained. 4. TRANSMITTER 4.1. Frequency error 4.1.1. Definition The frequency error of the transmitter is the difference between the measured carrier freque
8、ncy and its nominal value. Edition of September IS, 1988 _- I l CEPT T/R*20-04E = 2326434 000b407 4 f 0.6 - - 4.1.2. 4.1.3. - - f 1.5 f 1.5 *2 f 2.5 4.2. 4.2.1. 4.2.2 4.2.3. 4.2.3.1 TIR 20-04 E Annex 11, Page 7 Method of measurement The carrier frequency shall be measured in the absence of modulatio
9、n (if possible) with the transmitter connected to an artificial antenna (Clause 3.2.). Equipment with integral antennae shall be placed in a test fixture (Clause 3.4.2.) connected to the artificial antenna (Clause 3.2.). The measurement shall be made under normal test conditions (Clause 2.3.) and ex
10、treme test conditions (Clause 2.4.), (Clauses 2.4.1. and 2.4.2. applied simultaneously). Limit The frequency error shall not exceed the values given in Table 1 (T/R 20-04) in both normal and extreme test conditions or in any intermediate set of conditions. Channel spacing (kH4 20 and 25 Transmitter
11、carrier power Dejnition Frequency error 27.3-32.3 MHz I 146-174 MHz I 430-460 MHz The transmitter carrier power is the mean power delivered to the artificial antenna during a radio frequency cycle or, in the case of equipment with integral antennae, the effective radiated power in the direction of m
12、aximum field strength under specified conditions of measurement (Clause 3.5.), if possible in the absence of modulation. The rated output power is the carrier power declared by the manufacturer. Method of measurement for equipment with an outlet for connection to an external antennae The transmitter
13、 shall be connected to an artificial antenna (Clause 3.2.), and the power delivered to this .artificial antenna shall be measured. The measurements shall be made under normal test conditions (Clause 2.3.) and extreme test conditions (Clause 2.4.), (Clauses 2.4.1. and 2.4.2. applied simultaneously).
14、Method of measurement of equipment with integral antennae Method of measurement under normal test conditions On a test site fulfilling the requirements of Clause 3.5. the sample shall be placed on the support in the following position: (a) for equipment with internal antennae, it shall stand vertica
15、lly, with that axis vertical which is closest (b) for equipment with rigid external antennae, the antenna shall be vertical; (c) for equipment with non-rigid external antennae, with the antenna extended vertically upwards by a The transmitter shall be switched on, without modulation (if possible), a
16、nd the test receiver shall be tuned to the frequency of the signal being measured. The test antenna shall be orientated for vertical polarisation and shall be raised or lowered through the specified height range until a maximum signal level is detected on the test receiver. The transmitter shall be
17、rotated through 360“ until a higher maximum signal is received. Note. This maximum may be a lower value than the value obtainable at heights outside the specified limits. to vertical in normal use; non-conducting support. The transmitter shall be replaced by the substitution antenna as defined in Cl
18、ause 3.5., and the test antenna raised or lowered as necessary to ensure that the maximum signal is still received. The input signal to the substitution antenna shall be adjusted in level until an equal or a known related level to that detected from the transmitter is obtained in the test receiver.
19、The carrier power is equal to the power supplied to the subsitution antenna, increased by the known relationship if necessary. The measurement shall be repeated for any alternative antenna supplied by the manufacturer. A check should be made at other planes of polarization to ensure that the value o
20、btained above is the maximum. If larger values are obtained, this fact should be recorded in the test report. Edition of September IS, 1988 CEPT T/R*20-04E 232b4l14 000b408 b TIR 20-04 E Annex II, Page 8 4.2.3.2. 4.2.4. 4.3. 4.3.1. 4.3.2. 4.3.2.1. 4.3.2.2. Method of measurement under extreme test co
21、nditions The equipment shall be placed in the test fixture (Clause 3.4.2.), and the power delivered to the artificial antenna shall be measured. The measurements shall be made under normal test conditions (Clause 2.3.) and extreme test conditions (Clause 2.4.), (Clauses 2.4.1. and 2.4.2. applied sim
22、ultaneously). Limits The carrier output power under normal test conditions and under extreme test conditions shall not exceed the values given in Table II (T/R 20-04). I Carrier frequencies I Below 50 MHz I Above 50 MHz I I Effective radiated power I 0.1 W I 0.5 W I I Output power I 0.5 W 0.5 w Tabl
23、e II (T/R 20-04). Adjacent channel power Definition The adjacent channel power is that part of the total output power of a transmitter modulated under defined conditions of modulation which falls within a specified passband centered on the nominal frequency of either of the adjacent channels. This p
24、ower is the sum of the mean power produced by the modulation, hum and noise of the transmitter. Methods of measurement General Two methods are proposed, the results of which are equivalent. The member Administrations of CEPT are requested to use one or both of these methods. The method applied shall
25、 be stated in the test reports. Note. When using the test fixture for this measurement, it is important to ensure that direct radiation from the transmitter to the power measuring receiver or spectrum analyser does not affect the result. Method of measuring using a power measuring receiver The adjac
26、ent channel power shall be mesured with a power measuring receiver which conforms to Clause 4.3.2.2.2. (also referred to in Clause 4.3. as the “receiver”). 4.3.2.2.1. Operations (a) The transmitter shall be operated at the carrier power determined in Clause 4.2. under normal test conditions (Clause
27、2.3.). The output of the transmitter shall be linked to the input of the receiver by a connecting device such that the impedance presented to the transmitter is 50 ohms and the level at the “receiver” input is appropriate. In the case of equipment with integral antennae the equipment shall be placed
28、 in the test fixture (Clause 3.4.2.) and operated at the carrier power (Clause 4.2.) under normal test conditions (Clause 2.3.). The radio frequency output of the test fixture shall be applied to the input of the receiver, at a level that is appropriate. (b) With the transmitter unmodulated), the tu
29、ning of the “receiver” shall be adjusted so that the maximum response is obtained. This is the O dB response point. The “receiver” attenuator setting and the reading of the meter shall be recorded. ) The measurement may be made with the transmitter modulated with the normal code test signal (Clause
30、3.1.4.), in which case this fact shall be recorded along with the test results. Edition of September 15, 1988 CEPT T/R*K20-04E 2326414 000b409 8 Channel spacing in kHz TIR 20-04 E Annex li, Page 9 Specified necessary Displacement bandwidth in kHz of the 6 dB point (c) The tuning of the power measuri
31、ng receiver shall be adjusted away from the carrier so that the “receivers 6 dB response nearest to the transmitter carrier frequency is located at a displacement from the nominal carrier frequency as given in Table III (T/R 20-04). 25 20 12.5 10 16 14 8.5 8.5 17 13 8.25 5.15 Table III (T/R 20-04).
32、(d) The transmitter shall be modulated with the normal coded test signal (Clause 3.1.4.). If possible this (e) The receiver variable attenuator shall be adjusted to obtain the same meter reading as in step (b), or (0 The ratio of adjacent channel power to carrier power is the difference between the
33、attenuator settings (g) The measurement shall be repeated with the “receiver” tuned to the other side of the carrier. 4.3.2.2.2. Power measuring receiver specification The power measuring receiver consists of a mixer, an IF-filter, an oscillator, an amplifier, a variable attenuator and an r.m.s. val
34、ue indicator. Instead of the variable attenuator with the r.m.s. value indicator it is also possible to use a dB-calibrated r.m.s. voltmeter. The technical characteristics of the power measuring receiver are given below. The IF-filter shall be within the limits of the following selectivity character
35、istic. should be a continuous modulation for duration of the measurement. a known relation to it. in step (b) and (e) corrected for any differences in the reading of the meter. 4.3.2.2.2.1. IF-filter 04 D1 dB 90 D4 O Dl kHz Figure 2 (T/R 20-04). Selectivity characteristic of the “receiver”. Ediiion
36、of September 15, 1988 CEPT T/R*20-04E - 2326414 O006410 4 m Channel spacing I kHz Tf R 20-04 E Annex II, Page 10 Tolerances range (kHz) D1 D2 D3 D4 Depending on the channel spacing, the selectivity characteristic shall keep the following frequency separa- tions from the nominal centre frequency of t
37、he adjacent channel: Frequency separation of filter curve from nominal centre frequency of adjacent channel (kHz) spacing 10/12.5 4.25 5.5 9.5 7.0 8.25 12.25 25 8.0 9.25 13.25 1 Oll 2.5 20 25 Table IV (T/R 20-04). Depending on the channel spacing, the attenuation points shall not exceed the followin
38、g tolerances: +1.35 f 0.1 - 1.35 - 5.35 +3.1 fO.l - 1.35 -5.35 +3.1 fO.1 - 1.35 - 5.35 Channel spacing I kHz Tolerances range (kHz) D1 D2 D3 D4 Table V (T/R 20-04). Attenuation points close to carrier. 1 o/ 12.5 20 25 f 2.0 f 3.0 f 3.5 f 2.0 f 3.0 f 3.5 f 2.0 f 3.0 f 3.5 +2.0 - 6.0 + 3.0 -7.0 +3.5 -
39、 7.5 Table VI (T/R 20-04). Attenuation points distant from the carrier. The minimum attenuation of the filter outside the 90 dB attenuation points must be equal to or greater than 90 dB. 4.3.2.2.2.2. Attenuation indicator The attenuation indicator shall have a minimum range of 80 dB and a reading ac
40、curacy of 1 dB. With a view to future regulations an attenuation of 90 dB or more is recommended. 4.3.2.2.2.3. Rms value indicator The instrument shall accurately indicate non-sinusoidal signals in a ratio of up to 10: 1 between peak value and r.m.s. value. 4.3.2.2.2.4. Oscillator and amplifier The
41、oscillator and the amplifier shall be designed in such a way that the measurement of the adjacent channel power of an unmodulated transmitter, whose self-noise has a negligible influence on the measurement result, yields a measured value of G90 dB for channel spacing of 20 and 25 kHz and G -80 dB fo
42、r channel spacings of 10 and 12.5 kHz, referred to the carrier of the transmitter. 4.3.2.3. Method of measurement using a spectrum analyser 4.3.2.3.1. The adjacent channel power may be measured with a spectrum analyser which conforms to Clause 4.3.2.3.2. The transmitter shall be operated at the carr
43、ier power determined in Clause 4.2. under normal test conditions (Clause 2.3.). The output of the transmitter shall be linked to the input of a spectrum analyser by a connecting device such that the impedance presented to the transmitter is 50 ohms and the level at the spectrum analyser input is app
44、ropriate. The transmitter shall be modulated by the normal coded test signal. If possible this should be continuous modulation for the duration of the measurement. The spectrum analyser shall be so adjusted that the spectrum of the transmitter output, including that part which lies within the adjace
45、nt channel, is displayed. Edition of September 15, 1988 - _ CEPT T/R*ZO-O4E 232b414 0006411 b = 1 O/ i 2.5 20125 TIR 20-04 E Annex 11, Page 11 10 microwatt 200 nanowatt For the purpose of this test, the bandwidth of a receiver of the type normally used in the system shall be taken from among the fol
46、lowing values: (a) 16 kHz for adjacent channel spacing of 25 kHz; (b) 14 kHz for adjacent channel spacing of 20 kHz; (c) 8.5 kHz for adjacent channel spacing of 10/12.5 kHz, with a tolerance of f 10%. The centre frequency of the bandwidth within which measurements are to be made shall have a separat
47、ion from the nominal carrier frequency of the transmitter equal to the channel separation for which the equipment is intended. The adjacent channel power is the sum of the power relative to the useful signal and of the noise in the appropriate bandwidth. This sum may be calculated or an automatic po
48、wer level integrating device may be used to obtain it (see Clause 4.3.2.3.3.). In the latter case, the relative power level of the carrier and its sidebands is initially measured by integration in the appropriate bandwidth, centred on the nominal frequency. The integration is repeated at this bandwi
49、dth centred on the nominal frequency of the adjacent channel and the input level of the carrier signal increased until the same power level at the output of the device is obtained. The difference in the input levels, in dB, is the ratio of the adjacent channel power to the carrier output power. The adjacent channel power is determined by applying this ratio to the carrier output power as measured in Clause 4.2. or by a direct substitution measurement using a calibrated source. The measurement shall be repeated for the other adjacent channel. O Edition of September 15, 1988 4.3.2.3.2
