About impedance matching

键盘侠1988

About impedance matching [Copy link]

 

Can any expert help me to specify, the following circuit drives a 4M transducer, and the voltage drop is too large after adding an extension line. How to solve it: (The extension line is a 1.5m RF coaxial line. The drive is normal without the extension line, but it cannot drive the transducer after adding it)

Jacktang

It is also possible that the characteristic impedance of the coaxial line may not match the rest of the system, causing signal reflection and attenuation.

键盘侠1988

Jacktang posted on 2024-4-18 07:28 It is also possible that the characteristic impedance of the coaxial line may not match the rest of the system, causing signal reflection and attenuation,,,

How can I troubleshoot this situation? ? This is a blind spot in my knowledge, please give me some advice.

maychang

Your circuit operates at a frequency of 4M, presumably 4MHz. This frequency corresponds to a wavelength of 75 meters, and your extension cord is only 1.5m, which is 1/50 of the wavelength, so it is not "unable to drive the transducer". First, you should consider whether the extension cord is well welded.

乱世煮酒论天下

Where do you use this transducer?

键盘侠1988

maychang posted on 2024-4-18 09:29 Your circuit operates at 4M, presumably 4MHz. The wavelength corresponding to this frequency is 75 meters, and your extension cable is only 1.5m, which is 1/50 of the wavelength, so it is not...

After checking the soldering, there is no problem. The following are the electrical characteristics of the coaxial line

and the following are the parameters of the transducer Could it be an impedance problem? ?

键盘侠1988

Luan Shi Zhu Jiu Lun Tian Xia published on 2024-4-18 11:21 May I ask where this transducer is used?

This is a DIY thing, mainly to see how to drive the atomizer

maychang

Keyboard Man 1988 posted on 2024-4-19 09:51 After checking the welding, there is no problem. The following are the electrical characteristics of the coaxial line and the parameters of the transducer. Could it be an impedance problem? ?

【Could it be an impedance problem? ? 】

I don't think so.

键盘侠1988

maychang posted on 2024-4-19 10:15 [Is it an impedance problem? ? ] I don’t think so.

The voltage at the beginning of the cable I tested the transducer was about 80V, and when it reached the end, there was only about 18V left.

maychang

Keyboard Man 1988 posted on 2024-4-19 10:19 The voltage at the beginning of the cable I tested the transducer was about 80V, and when it reached the end, there was only about 18V left

What is the voltage across the transducer when no coaxial line is added?

What instrument did you use to measure?

键盘侠1988

maychang posted on 2024-4-19 10:35 What is the voltage across the transducer when there is no coaxial line? What instrument did you use to measure it?

Before adding the coaxial line, it was about 80V, as tested by an oscilloscope.

maychang

Keyboard Man 1988 posted on 2024-4-19 10:54 Before adding the coaxial line, it was about 80V, tested by an oscilloscope

I can't figure out what causes the voltage across the transducer to drop.

键盘侠1988

maychang posted on 2024-4-19 10:58 This, I can't figure out what causes the voltage at both ends of the transducer to drop.

Then I'll check it myself.

JCF184

Little White passing by

伟林电源

Use an oscilloscope to measure the GS waveform of the mos and you should be able to find the problem.