This post was last edited by donatello1996 on 2018-10-22 00:18 1. Project background: A wireless spectrum analyzer is a very useful tool for detecting surrounding frequency signals. It can detect whether there are wireless communication signals around, such as 2G/3G/4G/WIFI communication signals or 135MHz/433MHz walkie-talkie communication signals. People can use spectrum analyzers to test various parameters of walkie-talkies or monitor unknown WIFI signals to ensure communication security, playing a key role in the field of civil and military wireless communications. Traditional spectrum analyzers are very large, as big as a box, and very heavy. They need to be plugged into a 220V power supply when working. They are basically not portable and can only be placed on a table for detection. In recent years, with the development of embedded software and hardware, wireless spectrum analyzers have begun to take the small route. Now many portable wireless spectrum analyzers can be as small as mobile phones, powered by portable 5V DC power supplies, and can be easily picked up for testing. Take the spectrum analyzer produced by seeed (Shenzhen Seeed Technology Co., Ltd.) as an example. It is only the size of a palm and uses a monochrome black and white LCD as an interface display. It has both spectrum transmitter and spectrum analysis functions. However, this spectrum analyzer produced by seeed is for amateurs. The ADC frequency and accuracy of the microcontroller they use are far from professional standards. I am currently working as an embedded software engineer in the company. This time I used the GD32F350 development board, combined with my knowledge of signal processing and practical experience, and made full use of the performance advantages of the development board to create a professional spectrum analyzer with a color screen interface and computer host control function. 2. Changes in project details and problems encountered: The initial plan was to use the 8266 module as the WIFI network control module of the development board. However, in actual application, the power supply of the GD32F350 Little Red Board was not very stable. After plugging in the power supply pin of the 8266, using the GPIO high level or 3.3V output pin to connect the EN pin of the 8266 module will cause the development board to restart. Therefore, the 8266 module was abandoned as the control, and the traditional computer-side serial port host program control was used instead. And because the Little Red Board's power supply is unstable, it cannot drive two 5V-powered devices at the same time. It is necessary to add an additional 5V power input at the CN3 pin header, such as a switching power supply, a serial port to USB module, etc. 3. System block diagram
5. Physical connection diagram: Because the ADF4351 frequency analysis module is our company's commercial secret, we cannot reveal its appearance and schematic diagram, so we use foam paper to cover it. I hope Zhaoyi will forgive me. If you are interested in the principle of this module, you can communicate with me separately on QQ. The LCD screen used is a SPI bus LCD color screen. Because the power supply circuit design of the Little Red Board itself is problematic, it cannot supply high power to the 5V powered peripheral module, so it needs to be connected to a 5V voltage input, such as a USB to TTL serial port module or a switching power supply. 6. Frequency curve interface demonstration diagram:
When there is a frequency signal input, for example, I pressed the PTT transmit button of the U-segment walkie-talkie at this time and transmitted a wireless frequency of 435.55MHz, the curve will change significantly and a peak will appear:
The purpose of the AMP function is to allow the microcontroller to adapt the signal amplification factor (amp_value) according to the algorithm. That is, when the signal is too weak, the amplification factor is continuously increased until a peak value approaches the maximum value boundary (amp_value increases); if a signal stronger than the current peak value appears, the frequency amplification factor is reduced (amp_value decreases) in turn to adapt the new signal as the amplification factor of the peak signal. Then comes the WIFI frequency analysis interface: The 2.4G WIFI frequency of mobile phones or 8266 modules is roughly between 2400MHz and 2500MHz, divided into 14 channels. The bandwidth of each channel is 12MHz, and there is a 5MHz overlap area between two adjacent channels. For example, 2.421~2.433GHz is channel 5, 2.426~2.448GHz is channel 6, and so on. Each WIFI hotspot will reuse these 14 channels with different time differences according to the protocol of its own manufacturer. Different channel frequencies are used crosswise, so that different WIFI hotspots can be turned on at the same time without any interference. Here I use 14 spectrum bar graphs to represent the signal strength of each channel. When the bar jumps, it means there is WIFI nearby, such as the 8266 module next to it: 383740 383741 383737 7. Host computer program interface: 8266 WIFI module was originally planned to be used as the control end of the system, but various problems were encountered. Finally, the computer had to use the wired serial port to control the system. The control functions include: 1. Setting the start and end frequencies; 2. Setting the switch of the AMP function; 3. Switching the WIF spectrum and the broken line interface; 4. Displaying the peak frequency and the peak frequency strength.
Boss, what is the bandwidth and sampling rate of this spectrum analyzer? I have always had a question. If I use the performance of GD305 to measure the 2.4g spectrum, will the data be too large and cause untimely processing? You also have a color frequency refresh
The sampling rate of the spectrum analyzer is definitely not as good as that of a professional desktop frequency analyzer. The approximate data is obtained by summing up several tests, and the accuracy is sufficient for daily use.
Details
Published on 2018-10-21 13:04
The sampling rate of the spectrum analyzer is definitely not as good as that of a professional desktop frequency analyzer. The approximate data is obtained by summing up several tests, and the accuracy is sufficient for daily use.
Details
Published on 2018-10-21 13:04
lehuijie posted on 2018-10-21 12:07 Boss, what is the bandwidth and sampling rate of this spectrum analyzer? I have always had a question. If I use the performance of GD305 to measure the spectrum of 2.4g, will the data be too large and lead to...
The sampling rate of the spectrum analyzer is definitely not as good as that of a professional desktop frequency analyzer. The rough data is obtained by summing up several tests, and the accuracy can meet daily use.
lehuijie posted on 2018-10-21 12:07 Boss, what is the bandwidth and sampling rate of this spectrum analyzer? I have always had a question. If I use the performance of GD305 to measure the spectrum of 2.4g, will the data be too large and lead to...
This working principle is our company's commercial secret and cannot be disclosed. You can refer to the design of some frequency analyzers on the Internet.
The GD MCU actually acts as a data receiver and forwarder. All core functions such as up and down frequency conversion, sampling and analysis are completed by his company's modules. After processing, a result is output. The MCU only performs some data transmission...
The functions that a single-chip microcomputer can do are just control and acquisition. One is output and the other is input. How much more powerful functions do you want a single-chip microcomputer to achieve? How about playing videos?
Details
Published on 2018-11-21 19:06
Here is a hardware connection diagram. Since the frequency analysis module is company confidential, it is covered. The red one is the GD32F350 small red board.
Feiyang self-published on 2018-10-22 14:12 GD MCU actually acts as a data receiver and forwarder. All the core functions such as up and down frequency conversion, sampling and analysis are completed by his company's modules. ...
The functions that the MCU can do are only control and acquisition. One output and one input. How much more awesome functions do you want the MCU to achieve? Is it good to play videos?
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