Which one has a 50 ohm impedance matching circuit? Please refer to it.

QWE4562009

Which one has a 50 ohm impedance matching circuit? Please refer to it. [Copy link]

 

Which one has a 50 ohm impedance matching circuit? Please refer to it.

btty038

The instrument and the load are both 50 ohms.

半亩先生

Can't we just use an antenna? 50 ohm impedance is best made with a 4-layer board, but the board is expensive and the signal may not be good.

topwon

This is not a certain circuit, but refers to the PCB routing, terminals, and wires are designed according to the 50 ohm characteristic impedance requirement. Among them, PCB routing is achieved by calculating and adjusting parameters such as layer spacing, line width, and line spacing. Generally, tools are used to estimate and design first, and then the circuit board factory is asked to make fine adjustments.

Place several capacitors/inductors connected to the ground and in series near the antenna terminals on the PCB to form a π-shaped circuit, which is convenient for compensating and fine-tuning the antenna performance.

QWE4562009

topwon posted on 2019-9-20 11:05 This is not a certain circuit, but refers to the PCB routing, terminals, and wires are designed according to the 50 ohm characteristic impedance requirement. Among them, the PCB routing is designed by calculating...

PI circuit

QWE4562009

Mr. Banmu published on 2019-9-20 11:03 Can't we use the antenna directly? 50 ohm impedance is best made with a 4-layer board, the board is expensive, and the signal may not be good

It's FPC, not onboard.

QWE4562009

btty038 posted on 2019-9-20 10:26 Both the instrument and the load are 50 ohm characteristics

Why is it 50 ohms? Can this be tested? It shouldn't be tested like measuring resistance, right?

topwon

QWE4562009 posted on 2019-9-20 14:27 Why is it 50 ohms? Can this be tested? It shouldn't be tested like measuring resistance.

The characteristic impedance of PCB traces should be measured with TDR. As for why it is 50 ohms for single-ended, this is a historical issue. The predecessors selected this value after a long period of calculation and practice. Of course, there are different impedance requirements for different applications, such as 75 ohms for single-ended, 90 ohms for differential, 100 ohms for differential, 120 ohms for differential, and so on. . . .

topwon

why 50ohm.pdf (68 KB, downloads: 53)

2019-9-20 14:59 上传

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btty038

topwon posted on 2019-9-20 14:58 The characteristic impedance of PCB traces should be measured by TDR. As for why it is 50 ohms for single-end, this is a historical problem. After a long period of calculation and practice, the old predecessors have found that...

50 Euros, towards 50 Euros, not absolutely 50, I've learned, thank you

btty038

topwon posted on 2019-9-20 14:59

chunyang

If we talk about impedance matching, it's a matter of a resistor, but obviously that's not what the OP wants. So, let's first fully describe your problem.

半亩先生

QWE4562009 posted on 2019-9-20 14:26 It is FPC instead of onboard

It seems that what you have is a NB module. Since you bought the module from someone else, why do you need to develop the antenna yourself?

Even if it is a flexible board, it is better to buy it from Taobao than to make the sample yourself.

The performance of the flexible board is not as good as that of the cylindrical antenna. Don't you want your Internet function to be known?

QWE4562009

Mr. Banmu published on 2019-9-24 12:01 It seems that you bought the NB module from someone else. Why do you need to develop the antenna yourself? Even if it is a flexible board, it is better to buy it from Taobao than to make it yourself...

My product only uses this module. The antenna should be suitable for its own structure installation.

DAXSX

QWE4562009 posted on 2019-9-20 14:26 Yes, π-type circuit

It's a π-type circuit.