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22

Freescale Semiconductor

MC44CC373

Audio Modulation Index - FM Modulation

Video: Black Sync

This is measured using a Demodulator in B/G

and an Audio Analyzer at 1 kHz

The audio signal 205 mV at 1 kHz is supplied by the Audio Analyzer, and the

FM demodulated signal deviation is indicated on the Demodulator in kHz peak.

This value is then converted in % of FM deviation, based on specified

standards.

Audio Frequency Response

Video: Black Sync

This is measured using a Demodulator in B/G

and an Audio Analyzer.

demodulated by the Demodulator and the audio analyzer measures the AC

amplitude of this demodulated audio signal: this value is taken as a reference

(0 dB).

The audio signal is then swept from 50 Hz to 15 kHz, and demodulated AC

amplitude is measured in dB relative to the 1 kHz reference.

Audio pre-emphasis and de-emphasis circuits are engaged, all audio analyzer

filters are switched OFF.

Audio Distortion FM

Audio: 1 kHz, adjustable level

Video: Black Sync

This is measured using a UHF Demodulator in

B/G and an Audio Analyzer at 1 kHz. The

output level of the audio analyzer is varied to

obtain a deviation of 50 kHz indicated on the

Demodulator.

The input arms detector of the Audio Analyzer converts the ac level of the

combined signal + noise + distortion to dc. It then removes the fundamental

signal (1 kHz) after having measured the frequency. The output rms detector

converts the residual noise + distortion to dc. The dc voltmeter measures both

dc signals and calculates the ratio in% of the two signals.

Audio Signal to Noise

Audio: 1 kHz, adjustable level

Video: EBU Color Bars

This is measured using a Demodulator in B/G

and an Audio Analyzer at 1 kHz. The output

level of the Audio analyzer is varied to obtain

a Modulation Deviation of 25 kHz indicated on

the Demodulator.

The Audio Analyzer alternately turns ON and OFF its internal audio source to

make a measure of the Audio signal plus noise and then another measure of

only the noise.

The measurement is made using the internal CCIR468-2 Filter of the Audio

Analyzer together with the internal 30 +/

−2 kHz (60 dB/decade) Lowpass

filters.

The demodulator uses a quasi-parallel demodulation as is the case in a normal

TV set. In this mode the Nyquist filter is bypassed and the video carrier is used

without added delay to effectuate intercarrier conversion. In this mode the

phase noise information fully cancels out and the true S/N can be measured.

Table 22. Performance Measurement Test Set-ups (continued)

Device and Signals Set-up

Measurement Set-up

ADist

Distortion Noise

+

() Distortion Noise Signal

++

()

⁄

=

ASN dB

()

20

Signal Noise

+

()

log

×

Noise

()

⁄

=