Ceyear 4051 Series, User Manual

Page: 129 / 751

4. Operating Instruction
4.2 Advanced operation guide
115
4.2.5.2 Measure SNR
Step 1. set the analyzer as spectrum analysis mode and reset the analyzer:
 Press 【 Mode 】 and [Spectrum].
 Press
【
Preset
】
.
Step 2. Input 500 MHz internal calibration signal into the analyzer:
 Press
【
Input/Output
】
, [Input Port RF Cal] to select calibration port.
 Press [Cal Port], [500 MHz] to select 500 MHz calibration signal.
Step 3. set center frequency, frequency span, reference level and attenuator:
 Press 【 Frequency 】 , [Center Freq] and enter 500 MHz.
 Press
【
Span/X Axis
】
, [Span] and enter 1 MHz.
 Press
【
Amplitude/Y Axis
】
, [RefLevel] and enter -10 dBm.
 Press 【 Amplitude/Y Axis 】 , Press 【 Amplitude/Y Axis 】 , [Attenuation ▶ ], [Mech Atten Auto
Man
] and
enter 40 dB.
Step 4. place the marker at the signal peak and then put the delta marker to the noise with 200 kHz
frequency offset:
 Press
【
Peak Search
】
, [Delta Marker] and enter 200 kHz.
Step 5. turn on the delta marker function to check SNR:
 Press [Marker Func], [Noise Marker ON OFF] to open noise marker. As shown in Fig. 4.31.
SNR reading is expressed in the unit of dBc/Hz because such noise level is the value of noise bandwidth under
1 Hz which is reduced at a rate of 10×log (BW). If you wish to obtain noise values under different channel
bandwidth, the measurement result needs to be corrected based on current bandwidth. For example, if the
analyzer reading is -86.07 dBc/Hz and the current channel bandwidth is 30 kHz, SNR will be S/N = 86.07 dBc
/ Hz - 10 × log (30 kHz) = 41.3 dBc / (30kHz). If the delta maker is smaller than 1/4 of the distance from the
signal peak to response edge, there will be potential error in noise measurement.