ETSI ETS 300 441, Инструкция по эксплуатации

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Page 19
ETS 300 441: February 1996
7.6.2 Method of measurement
The test shall be carried out with the automatic gain control operative. The measurement shall be made
by means of the simultaneous application of two test signals to the input of the receiver. One of the test
signals is the wanted signal to which the receiver is tuned and the other is the unwanted signal.
The wanted signal shall be an A2A signal with a carrier frequency of 2 182 kHz, modulated to a depth of
30 % at 1 kHz.
Measurements shall be carried out with an input level of the wanted signal of + 60 dB
µ
V.
The receiver shall be adjusted so that the wanted signal gives standard output power (subclause 7.1). The
modulation of the wanted signal shall be switched off.
The unwanted signal shall have a frequency of
±
20 kHz relative to that of the wanted signal and be
modulated to a depth of 30 % at 400 Hz. The input level of the unwanted signal shall be increased until
total unwanted power in the receiver output due to cross modulation is 30 dB below the standard output
power.
The input of the unwanted signal at which this condition is reached is the cross modulation level.
7.6.3 Limit
The cross modulation level shall not be less than + 90 dB
µ
V.
7.7 Intermodulation
7.7.1 Definition
Intermodulation is a process by which signals are produced from two or more (generally unwanted)
signals simultaneously present in a non-linear circuit.
7.7.2 Method of measurement
With the automatic gain control operative, an A2A test signal at the carrier frequency 2 182 kHz
modulated to a depth of 30 % at 1 kHz shall be applied to the receiver input at a level of + 30 dB
µ
V, and
the audio frequency gain control shall be adjusted to give standard output power. The audio frequency
gain control shall not be adjusted during the remainder of this test. The wanted signal shall then be
removed and the two unwanted signals shall be simultaneously applied to the input of the receiver. The
signal nearest to the wanted signal frequency shall be unmodulated. The other unwanted signal shall be
an A2A signal modulated to a depth of 30 % at 1 kHz.
Neither of the two signals shall have a frequency within 30 kHz from the wanted signal (input frequencies
likely to cause unwanted inter-modulation products are mentioned in ITU-R Recommendation 332-4,
section 6.4 [5]). When choosing the frequencies used for this measurement, care should be taken to avoid
frequencies at which spurious responses occur. The input levels of the two interfering signals shall remain
equal and shall be adjusted until the output power of the receiver due to the interfering signals is equal to
the standard output power.
7.7.3 Limit
The level of either of the two interfering signals which results in standard output power shall not be less
than + 80 dB
µ
V.
7.8 Spurious response rejection ratio
7.8.1 Definition
The spurious response rejection ratio is the ratio of the input level of an unwanted signal at the frequency
of the spurious response, to the input level of a wanted signal, when the wanted and unwanted signals
individually produce the same SND/N ratio at the receiver output.