Does anyone know what are the methods of automatic metering of spectrum analyzers?

1. Level and frequency response verification.

The level measurement accuracy and frequency response are important parameters that reflect the uncertainty of the power amplitude measurement of the spectrum analyzer.

There are two components in this test:

The main verification equipment required includes: signal generators, power probes, and power dividers. Among them, the signal generator provides a suitable test signal, and the power divider should be calibrated with corresponding correction data.

In order to avoid the influence of standing waves on the test results, the power divider and the tested spectrum analyzer are usually directly connected to the fixed attenuator, and the loss and frequency response of the attenuator and the connecting cable also need to be included in the correction factor.

For absolute power accuracy verification, the spectrum analyzer selects small spans (e.g., 30kHz) and RBW (e.g., 10kHz), and the reference level is set to be equal to that of the signal generator. During the frequency response test, the reference frequency point level test is the same as the spectrum analyzer setting during the absolute power verification above, and the spectrum analyzer selects zero span (zero span), RBW (such as 10kHz) for other frequency point tests, and the reference level setting is equal to that of the signal generator.

The readings of the power meter (power probe) are corrected and used as standard reference values to evaluate the level and frequency response of the spectrum analyzer.

2. Verification of average display noise level.

The average display noise level characterizes the test sensitivity of the spectrometer.

Spectrometer settings: a 50 load matcher is connected to the input;

The reference level is set to a lower level, e.g. -60dBm;

Zero SPAN or smaller SPAN

Smaller RBW (less than or equal to 1 10 center frequency, not greater than 1kHz).

The display power value is normalized to 1 Hz. (dbm/hz)

3. Attenuator accuracy verification.

Verify the accuracy of the set value of the internal attenuator of the spectrum analyzer.

The connection is shown in the figure below, where the signal generator generates a constant, high-power signal (e.g., 10dBm) and connects to the RF input of the spectrum analyzer under inspection via a precision attenuator.

Set the built-in attenuator of the spectrum analyzer under test and switch it at full scale;

correspond to the setting value of the built-in attenuator of the spectrum analyzer, change the value of the precision attenuator, so that the sum of the set values of the two attenuators corresponds to the total range of the built-in attenuator of the tested spectrum analyzer;

When the built-in attenuator of the spectrum analyzer is 10dB, the power reading of the spectrum analyzer is used as the reference value of the reference level; The difference between the other attenuation settings and the above level reference values is the accuracy of the target attenuator after being corrected by the calibration data of the precision attenuator.

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The method of analysis and automatic metering is calculated according to its wavelength.

Spectrum analyzer is an instrument to study the spectral structure of electrical signals, which is used for the measurement of signal parameters such as signal distortion, modulation, spectral purity, frequency stability and intermodulation distortion, and can be used to measure some parameters of circuit systems such as amplifiers and filters, and is a multi-purpose electronic measuring instrument. It can also be referred to as a frequency domain oscilloscope, tracking oscilloscope, analysis oscilloscope, harmonic analyzer, frequency characteristic analyzer or Fourier analyzer, etc. Modern spectrum analyzers can display the results of the analysis in analog or digital form, and can analyze electrical signals in all radio frequency bands from VLF to submillimeter wave bands below 1 Hz.

If the instrument uses digital circuits and microprocessors, it has storage and computing functions; Equipped with standard interfaces, it is easy to form an automatic test system.

Spectrum analyzers are divided into two types: real-time analysis and sweeping. The former can obtain all the required spectrum information in the actual time of the measured signal and analyze and display the analysis results; The latter requires multiple sampling processes to complete the analysis of duplicate information. Real-time spectrum analyzers are primarily used for non-repetitive, short-duration signal analysis.

Non-real-time spectrum analyzers are mainly used for the analysis of continuous RF signals and periodic signals from the audio frequency to the sub-millimeter band.

The working principle of Beijing Furui Hengchuang Technology ****WH HS5720 special spectrum analyzer adopts digital detection technology, which replaces some traditional digital sound level meters in the past, and the stability and reliability are greatly improved. Integrated fractional octave filter. Built-in 6-octave filter, filter center frequency can be manually selected.

Large-screen LCD display, clear and intuitive display. The mechanical analogue meter can also reflect the results of the test. It has functions such as data connection with computer.

To a certain extent, a spectrum analyzer is a type of signal analyzer. Signal analyzers are a generic term and we cannot identify their specific functions from the name.

The main principle of the spectrum analyzer is based on the Fourier transform. What is the Fourier transform?

An arbitrary periodic signal, through the Fourier transform, can be decomposed into one or more or infinite sine waves of different sizes, frequencies, and phases. In other words, the periodic signal is made up of the superposition of these sine waves. A spectrum analyzer uses the Fourier transform to obtain the amplitude (magnitude), frequency (integer multiple of the fundamental frequency of the signal), and phase (relative to the fundamental or other reference signal) of these sine waves corresponding to a signal.

So, why do it?

A waveform, which we look at in an oscilloscope, is very intuitive, right?

However, unless it's a special, simple waveform, it's usually hard to do that after you've seen it, turn off the oscilloscope and let you redraw it, right?

The way an oscilloscope represents a signal, which we call a time-domain description, reflects the corresponding changes in the signal over time.

Spectrum analyzers, on the other hand, break down a signal into a large number of simplest sine wave components that can be quantitatively expressed (amplitude, frequency, phase). We only need to memorize a few numbers and with the right tools, we can reproduce the waveform.

This way of expressing a signal in a spectrum analyzer, with frequency as a variable, is what we call a frequency domain description.

At the most basic level, a spectrum analyzer can be thought of as a frequency-selective, peak-sensing voltmeter that is calibrated to display the RMS value of a sine wave.

It should be emphasized that although we often use a spectrum analyzer to display power directly, it is not a power meter after all. Of course, as long as you know a certain value of the sine wave (e.g. peak or average) and the value of the resistance used to measure this value, you can calibrate the voltmeter to indicate the power.

The advent of digital technology has given modern spectrum analyzers more capabilities. This guide provides an introduction to the basic principles of spectrum analyzers and describes the new capabilities that can be brought to these instruments using digital techniques and digital signal processing.

Regarding the classification of spectrum analyzers, the original scan-tuned superheterodyne analyzer could only measure amplitude. However, as technology continues to evolve and communication systems become more complex, phase plays an increasingly important role in measurement. Spectrum analyzers, while still known as signal analyzers, have evolved into a separate class of instruments.

By digitizing the signal, the phase and amplitude information in the signal can be preserved and displayed after one or more levels of frequency conversion. As a result, current signal analyzers combine the characteristics of analog, vector, and FFT (Fast Fourier Transform) analyzers. To further improve functionality, the new signal analyzer also incorporates a computer and features a removable disk drive that keeps sensitive data within a safe area even if the analyzer is moved to an unsecured location.

The development of technology has also led to the miniaturization of meters. As a result, engineers can more easily perform outdoor measurement tasks, such as surveying transmitter or antenna sites, with a rugged portable spectrum analyzer. In situations where a short stop is required for a quick measurement, an analyzer with zero warm-up time allows engineers to get up and running as quickly as possible.

By applying advanced calibration techniques, these handheld analyzers are able to perform field measurements with an accuracy of less than one-tenth of a dB compared to laboratory-grade benchtop spectrum analyzers.

Our technology is becoming more and more developed, and a series of electronic products have been developed. But no matter how good the electronic products are, there will still be a series of problems if they are used for a long time. When this phenomenon exists, we need a multi-functional electronic measuring instrument.

What we are preparing for you today is an introduction to a multi-functional electronic measuring instrument, a spectrum analyzer, and its principle.

First, let's understand what a spectrum analyzer is.

Spectrum analyzers are used to specialize.

A machine that studies the spectral structure of electrical signals. It is an indispensable equipment for the measurement of radio signals in our modern era, and it is also indispensable for the development and production of electronic products. Therefore, he is also called "the RF multimeter of the engineer", which is highly praised for its wide range of use.

Now that we've briefly understood the basics of spectrum analyzers, let's take a journey into the principles of spectrum analyzers.

The spectrum analyzer has a number of function control buttons on the work panel, which are used to adjust and control the system functions. The principle of the spectrum analyzer is that it responds differently to different frequency signals (mainly reflected in its filters and detectors), and then transmits the scanned signal to our CRT screen through the multi-task scanner to facilitate the recording of its data by our staff.

The above is the working principle of the spectrum analyzer, so what are its functions and advantages and disadvantages?

In fact, the function of the spectrum analyzer has been mentioned above, it is mainly for the research and development, production and inspection of electronic products, and then in detail is to measure the distortion, modulation and purity of the received signal.

The advantages of spectrum analyzer are: the practical performance of the product is very high, the application range is very wide, and it has brought a lot of convenience to our work;

The disadvantages of the spectrum analyzer are: the noise emitted by the spectrum analyzer is a bit loud when it is working, it is also relatively expensive, and when the operation time exceeds 200ms, there will be certain problems in our observation.

The above is an introduction to the principle and function of the spectrum analyzer brought to you today. According to the collected data, the general market price of the spectrum analyzer is between 4000-8000 yuan, and some of them are more than 10,000 yuan, and a few are very expensive. Therefore, the advice is that everyone should consider their own needs when choosing to buy, and do not be deceived and spend unjustly money.