It is a German spectrum analyzerIn modulation signal analysis, core skills need to be mastered from three dimensions: parameter configuration, functional application, and problem troubleshooting. The specific analysis is as follows:
1、 Parameter configuration skills: Accurately matching signal characteristics
Frequency range selection
The carrier frequency and sidebands of the modulated signal need to be covered. If the range is too narrow, the signal may be truncated; If it is too wide, it will reduce the measurement efficiency. For example, when analyzing a 1MHz signal, it is recommended to set the Span to 3MHz (extending 3 octave bands to both sides).
Resolution bandwidth (RBW) optimization
Narrow RBW (such as 10kHz): suitable for distinguishing close frequency components, but may prolong measurement time.
Wide RBW (such as 1MHz): improves measurement speed but reduces accuracy.
Recommended value: Choose 1/10 of the signal bandwidth as RBW. For example, when analyzing a signal with a bandwidth of 100kHz, RBW is set to 10kHz.
Video bandwidth (VBW) setting
VBW should be ≤ RBW/10 to smooth out noise. For example, when RBW=100kHz, VBW is set to 10kHz.
Function: Suppress random noise, improve signal-to-noise ratio, but too small may cause signal distortion.
Scan type selection
Zero intermediate frequency scanning: higher sensitivity, suitable for narrowband signals.
Sweep frequency scanning: suitable for broadband signal measurement.
Adaptation of detection methods
Peak detection: Observe transient signals.
Average detection: measure the average power.
Positive peak detection: measures the peak value of the signal.
2、 Functional application skills: Deep analysis of modulation characteristics
Automatic modulation analysis
Some models (such as N9000A) support automatic recognition of modulation types (AM/FM/PM/QAM, etc.) and automatic measurement of parameters (such as modulation depth, frequency deviation).
Demodulation function
AM demodulation: Extract envelope information and calculate modulation depth.
FM/PM demodulation: Analyze modulation index and frequency deviation.
Digital demodulation: supports ASK/FSK/PSK/QAM, etc., to recover binary data streams. Parameters such as bitrate and symbol rate need to be pre-set.
Preset measurement items
Simplify the operation process by selecting preset measurements such as signal-to-noise ratio and adjacent channel power through software.
Real time spectrum analysis (optional)
Enable real-time mode to capture transient intermodulation products, suitable for frequency hopping signal analysis.
Marking and Tracking Function
Use the 'Marker' function to locate the carrier and sideband frequencies, and automatically display parameters such as center frequency, bandwidth, peak power, etc.
IIIIt is a German spectrum analyzerProblem solving skills: Quickly locate and measure anomalies
Signal strength too low
Inspection items:
Signal source output power.
Connection cable quality (low loss coaxial cable is recommended).
Sensitivity setting of spectrum analyzer (enable preamplifier).
The measurement results are unstable
Optimize parameters:
Adjust RBW, VBW, and scanning time.
Enable the "trace averaging" function (such as 16 averaging) to reduce random noise.
Unable to identify modulation type
Inspection items:
Signal quality (whether there is significant noise or interference).
Use a vector signal analyzer for more in-depth analysis.
Intermodulation distortion measurement abnormality
Troubleshooting steps:
Check if the input signal power is too high (gradually decrease to -10dBm).
Replace high-quality connectors and shorten cable length.
Enable the "phase noise cancellation" function to reduce background noise.
Loss of high-frequency components
Solution:
Confirm that the input signal attenuation ratio is correct.
Enable full bandwidth mode (such as 20MHz).