CMX589A データシートの表示（PDF） - CML Microsystems Plc

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CMX589A

GMSK Modem

CML Microsystems Plc 

GMSK Modem

CMX589A

4.2.5 Rx S/N Detection

The Rx S/N Detector system classifies the incoming zero-crossings as GOOD or BAD depending upon the time

when each crossing actually occurs with respect to its expected time as determined by the Clock Extraction

PLL. This information is then processed to provide a logic level output at the Rx S/N pin. A high level indicates

a series of GOOD crossings; a low level indicates a BAD crossing.

By averaging this output, it is possible to derive a measure of the Signal-to-Noise-Ratio and hence the

Bit-Error-Rate of the received signal.

Figure 6: Typical Bit-Error-Rate Performance at VDD = 5.0V

Note: Figure 6 indicates typical performance, independent of bit rate (although the applied noise bandwidth is

considered to match the bit rate used), radio performance (e.g. IF filter distortion), supply voltage (higher bit

rates require VDD ≥ 4.5V), and other ‘real world’ factors.

© 1998 Consumer Microcircuits Limited

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D/589A/3

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