Interpretation of six common problems in the use of spectrum analyzer

A spectrum analyzer is an instrument that studies the spectrum structure of electrical signals. It is used to measure signal parameters such as signal distortion, modulation, spectral purity, frequency stability, and intermodulation distortion. It can be used to measure certain circuit systems such as amplifiers and filters. Parameter is a multi-purpose electronic measuring instrument.

It can also be called frequency domain oscilloscope, tracking oscilloscope, analysis oscilloscope, harmonic analyzer, frequency characteristic analyzer or Fourier analyzer, etc.

Modern spectrum analyzers can display the analysis results in an analog or digital manner, and can analyze electrical signals in all radio frequency bands from very low frequencies below 1 Hz to sub-millimeter wave bands.

If the digital circuit and microprocessor are used inside the instrument, it has storage and calculation functions; with a standard interface, it is easy to form an automatic test system.

The spectrum analyzer is a commonly used analysis instrument, mainly for the detection of radio frequency and microwave signals, and has certain applications in many fields.

Question and answer area

There are some common problems in the use of spectrum analyzers that need users' attention. Today I will introduce you to the six common problems in the use of spectrum analyzers. I hope they can help you.

Q1: How to set up to obtain the best sensitivity of the spectrum analyzer, so as to facilitate the observation of small signals?

A: First set the corresponding center frequency, span and reference level according to the size of the small signal being measured; then gradually reduce the attenuation value without the overload prompt of the spectrum analyzer.

If the signal-to-noise ratio of the small signal under test is less than 15db, gradually reduce rbw. The smaller the rbw, the lower the noise floor of the spectrum analyzer and the higher the sensitivity.

If the spectrum analyzer has pre-play, turn on the pre-play. Pre-opening can increase the noise figure of the spectrum analyzer, thereby improving the sensitivity. For small signals with low signal-to-noise ratio, you can reduce vbw or use trajectory averaging to smooth noise and reduce fluctuations.

It should be noted that the measurement result of the spectrum analyzer is the sum of the external input signal and the internal noise of the spectrum analyzer. To make the measurement result accurate, the signal-to-noise ratio is usually required to be greater than 20db.

Q2: Is the resolution bandwidth (rbw) as small as possible?

A: The smaller the rbw, the better the sensitivity of the spectrum analyzer. However, the scanning speed will become slower. Well set up rbw according to the actual test requirements to find a balance between sensitivity and speed-not only to ensure accurate measurement of the signal but also to get a fast measurement speed.

Q3: How to choose the average detection method (averagetype): power? logpower? voltage?

Logpower logarithmic power average: also known as videoaveraging, this averaging method has a low noise floor and is suitable for low-level continuous wave signal testing.

But there will be certain errors for "noise-like" signals, such as wideband modulated signals w-cdma, etc.

Power averaging: also known as rms averaging, this averaging method is suitable for total power measurement of "noise-like" signals (eg cdma).

Voltage averaging: This averaging method is suitable for observing the rise and fall times of amplitude modulation signals or pulse modulation signals.

Q4: Selection of scanning mode: sweep or fft?

A: The scan mode of modern spectrum analyzers usually has sweep mode and fft mode. Usually in the narrow rbw setting, fft has a speed advantage over sweep, but in the wider rbw condition, the sweep mode is faster.

When the span is less than the analysis bandwidth of fft, the fft mode can measure transient signals; when the span exceeds the fft analysis bandwidth of the spectrum analyzer, if the fft scan mode is used, the working method is to process the signal in sections There is a discontinuity in time between the time, then the useful signal may be lost during the signal sampling gap, and there will be distortion in the spectrum analysis.

This type of signal includes: pulse signal, tdma signal, fsk modulation signal, etc.

Q5: How does the choice of detector affect the measurement result?

Peak detection method: select the large value in each bucket as the measured value. This detection method is suitable for continuous wave signal and signal search test.

Sample detection method: This detection method is usually suitable for testing noise and "noise-like" signals.

negpeak detection method: suitable for small signal test, for example, emc test.

Normal detection mode: suitable for observing signal and noise at the same time.

Q6: What is the role of tracking source (tg)?

A: The tracking source is one of the common options on the spectrum analyzer.

When the output of the tracking source passes through the input port of the device under test and the output of this device is connected to the input port of the spectrum analyzer, the spectrum analyzer and the tracking source form a complete adaptive swept frequency measurement system.

Tracking the frequency of the signal output by the source can accurately track the tuning frequency of the spectrum analyzer.

The spectrometer with optional tracking source can be used as a simple scalar network analysis to observe the excitation response characteristic curve of the device under test, such as the frequency response and insertion loss of the device.

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• Plug the Remoce Socket$($)lnto the wall socket(s) and switch on the mams supply, the red LED will flash every second.
• If the LED is not flashing press & hold the manual ON/OFF button for 5 seconds until it Hashes

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Operation:
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If a Remote Socket does not react to the Remote Control please check the followng:
♦ Low battery in tbo Remote Control
• Distance too large between the remote control and the recerver (ensure the range distance is no more than 20 clear Metres) and free from obstacle that may reduce the distance.
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How to decode
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230 Metres
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