Newnes Radio and RF Engineering Pocket Book, 3rd Edition

181

The maximum frequency of the pulses will be when transmitting alter-

nate 1s and 0s, and the occupied bandwidth,

1

2

× bit rate, 32 kb/s.

Quantization as described above is linear, i.e. the spacing of the

quantization levels is the same over the range of pulse amplitudes.

This produces a poor signal-to-noise ratio for low-level signals which

is improved by the use of more closely-spaced levels at small signal

amplitudes than at large amplitudes. Where non-linear quantization

is used the most significant bit of the sample character identifies the

polarity of the signal.

If linear quantization is used then about 12 bits per sample are

needed to give a good ...