Chapter 4 — Spectrum Analyzer 4-19 Carrier to Interference Ratio Measurement
MS20xxA VNA Master UG 10580-00166 Rev. C 4-19
4-19 Carrier to Interference Ratio Measurement
Carrier to Interference Ratio (C/I) Measurement is a two-step process, first measuring the
carrier level and then, with the carrier turned off, measuring the remaining signals and noise
in the band of interest. After the two measurements are complete, the ratio of the carrier level
to the noise plus interference is displayed using three assumptions:
• The interferer is a narrowband frequency hopping signal (NB FHSS)
• The interferer is a wideband frequency hopping signal (WB FHSS)
• The interferer is a broadband signal (BB).
The primary application for this type of measurement is determining the magnitude of
interference problems for 802.11b, 802.11g and 802.11a access points (hot spots).
Procedure
1. Press the Frequency key followed by the Signal Standard soft key. Select the appropriate
signal standard based on the signal to be measured and press
Enter.
2. Press the
Select Channel soft key, select the operating channel of the access point being
measured and press
Enter.
3. Press the
Shift key followed by the Measure (4) key and the C/I soft key.
4. Press the
Center Freq soft key and enter the desired frequency, unless a Signal Standard
and Channel have already been selected in the
Frequency menu.
5. If needed, press the
Span soft key and set an appropriate span width for the signal to be
measured.
6. If the signal environment includes slow frequency hopping signals, such as cordless
telephones, press the
Min Sweep Time soft key to set a sweep time of one second or more
to give a good chance of capturing instances of the interfering signal.
7. Press the
On/Off soft key and follow the on-screen prompts to complete the
measurement.
8. After the measurement is complete, the measurement box gives results for the three
different signal types. Some measurement results may show as
Error, and this is to be
expected.
Note
Access to the transmitter is required to complete this procedure as the transmitted
carrier must be turned off for the second portion of the measurement.
10580-00166C.book Page 19 Thursday, February 21, 2008 12:52 PM
To Next Page