Baseband Processor For Mixed Mode Land Mobile Radio
CMX880
C4FM Receiver Bit Error Rates
1.e-01
1.e-02
1.e-03
1.e-04
1.e-05
1.e-06
BER with FEC (CMX880 + DSP)
BER without FEC (CMX880 only)
8
9
10
11
12
13
14
15
16
S/N dB (Noise in 2 x Symbol Rate Bandwidth)
Figure 27 Typical Bit Error Rate with and without FEC
The Bit Error Rate (BER) performance shown in Figure 27 is measured under nominal working conditions, with
pseudo-random data. The graph shows the BER of the CMX880 (which is without FEC), and also the BER that
is expected to be attainable when the CMX880 is used in conjunction with a DSP performing error correction.
This will depend on the DSP error correction algorithm performance.
Note:
S/N calculated as 20 ´ LOG ( Signal Voltage ¸ Noise Voltage), where:
10
·
·
Signal Voltage is the measured rms voltage of a random 4-level signal.
Noise Voltage is the rms voltage of a flat Gaussian noise signal having a bandwidth from a
few Hz to twice the symbol rate (9600Hz).
·
Both signals are measured at the same point in the test circuit.
ã 2001 Consumer Microcircuits Limited
79
D/880/1
CMLMICRO [ CML MICROCIRCUITS ]
