Viavi 87339, Operation Manual

Page: 92 / 198

Testing
4 -11
4.1.6.C C/N
0
Measurement Options
In scenarios where measurement speed is important, such as a production environment,
you can use a higher C/N0 value and extrapolate the sensitivity information from the
result.
There is a linear relationship between RF power and C/N0 ratio, refer to table 4-2. As an
alternative to measuring the receiver’s C/N0 ratio at the given sensitivity level, it is
possible to derive sensitivity based on the C/N0 at a different power level. Typical
receiver C/N0 ratio is 28 to 32 dB-Hz to achieve a position fix. If the receiver reports a
C/N0 value of 28 dB-Hz at -145 dBm, it also reports a C/N0 value of 43 dB-Hz at
-130 dBm.
NOTE:
It is important that a given receiver is first characterized by measuring the
acquisition sensitivity to ensure that receiver self-interference (e.g. spurs) or
digitization noise, does not adversely effect the C/No figure before applying this
technique.
While the exact RF level used to measure sensitivity varies from one receiver to the next,
the ratio of the receiver of C/N0 to RF power level is perfectly linear.
Table 4-2 Typical Receiver C/N
0
as a function of RF level
When a high input level is used to stimulate the C/N
0
ratio, the receiver reports the
maximum possible C/N
0
value allowed by the chipset. Typically this figure is between
54 to 66 dB -Hz, (56 dB - Hz in Table 4-2 example).
RF Level Receiver C/N
0
-110.0 dBm 56 dB –Hz
-115.0 dBm 56 dB –Hz
-120.0 dBm 53 dB –Hz
-125.0 dBm 48 dB –Hz
-130.0 dB 43 dB –Hz
-135.0 dB 38 dB –Hz
-140.0 dB 33 dB –Hz
-145.0 dB 28 dB –Hz