Impedance matching is a process of making one impedance equal to another another.
Questions tagged [impedance-matching]
653 questions
45
votes
8 answers
Why is 50 Ω often chosen as the input impedance of antennas, whereas the free space impedance is 377 Ω?
In order to efficiently deliver power to a different part of a circuit without reflection, the impedances of all circuit elements need to be matched. Free space can be regarded as a further element, since a transmitting antenna eventually should…
DK2AX
- 901
- 1
- 9
- 18
28
votes
3 answers
What happens at the end of a transmission line?
Let's say I wanted to make a widget containing a relay to switch between two antennas. There is a coax transmission line coming in from the transmitter, and two going out, each to a separate antenna. Inside is a relay which switches the center…
Phil Frost
- 56,804
- 17
- 141
- 262
22
votes
6 answers
Does Impedance Matching Imply any Practical RF Transmitter Must Waste >=50% of Energy?
According to the maximum power transfer theorem, when a fixed source impedance is given, the load impedance must be chosen to match to the source impedance to achieve maximum power transfer.
On the other hand, if the source impedance is not out of…
比尔盖子
- 6,064
- 2
- 24
- 51
21
votes
5 answers
What can reduce overshoot and ringing on a simple square wave pulse generator?
I've built a simple RC and Schmitt-trigger-based square wave pulse generator. On the breadboard, it has some obvious unwanted qualities due to jumper length, the breadboard itself, etc.
Schematic and breadboard version:
And the waveform…
JYelton
- 32,302
- 33
- 134
- 249
20
votes
2 answers
Can I solder a RG316 coax directly to a PCB instead of using the intended SMA connectors?
I have a length of RG-316 single shield 50Ω coaxial cable carrying a 5.8 GHz signal that I need to connect to a PCB. While cheap relative to most coaxial connectors, SMA connectors are still quite expensive, take up space and are relatively heavy.…
jms
- 8,504
- 3
- 22
- 45
18
votes
4 answers
What's the importance of source impedance termination?
Given a circuit like this:
simulate this circuit – Schematic created using CircuitLab
What's the importance of R1? One can guess that it's to make the output impedance of BUF1 equal to the impedance of the transmission line, but why is this…
Phil Frost
- 56,804
- 17
- 141
- 262
13
votes
6 answers
Does non-matching impedance of amplifier and speaker distort the sound?
I'm about to buy a pair of headphones and an audio interface with built in amplifier. The specs say that the amp's impedance is "<30 Ohms".
The headphone I'd like to buy is a Beyerdynamic DT 990, which has versions of different impedance.
I'm only…
László Stahorszki
- 233
- 2
- 5
13
votes
2 answers
How do I lay out PCB traces for a given "differential impedance"
This is an attempt to craft a good general question and answer for a topic that's been asked before, but only in specific situations.
Could you describe what I need to know, prior to laying out a PCB board for a differential signal pair with a…
Bryce
- 859
- 1
- 10
- 26
12
votes
5 answers
Trace impedance ohm meaning
I've been trying to understand the principle of trace impedance (single ended and differential) for a while, read several articles (all the best google has to offer), but I have still some serious issues finalizing my understanding of it.
First of…
Ilya
- 3,478
- 7
- 33
11
votes
1 answer
Balun/matching network question
I am having problem to verify what an app note (AN068) explains to calculate Balun values. I would appreciate if someone could tell me what/where am I doing wrong?
The summary of the RF part:
Blue part is the DC blocking cap, C10-L1 and L3-C11 are…
Angs
- 3,275
- 8
- 33
- 54
11
votes
2 answers
Effects of impedance matching between 50 and 75 Ohm coaxial cables for 10 Mbit/s, Manchester-coded signals (20 MHz)
TL,DR:
This is quite a bunch of text because I have included plenty of background info. However, there will finally be a good, and precise question: Should I use an impedance matching network when connecting cables of different impedance such as…
zebonaut
- 18,170
- 4
- 60
- 104
10
votes
2 answers
Why Characteristic Impedance must be 50 ohms?
Where does this number come from?
For single ended it must be 50 ohm and for differential pairs 100 ohm. Why?
For PCB with controlled-impedance these are that common numbers. Outside of the PCB you can find others numbers for characteristic…
Jesus Castane
- 1,442
- 2
- 12
- 26
10
votes
2 answers
Why is length matching performed with the clock trace length as the target length?
Length matching is performed mainly to avoid the skew generated among the parallel data lines/data bus width.
All the high speed PCB design guideline suggest performing length matching with the clock trace length as the target length and trace…
Ananthesh Acharya
- 265
- 1
- 13
10
votes
4 answers
Question about trace length matching patterns for high speed signals
A colleague and I had a discussion and a disagreement about the different ways high speed signals can be length-matched. We were going with an example of a DDR3 layout.
All the signals in the picture below are DDR3 data signals, so they are very…
SomethingBetter
- 2,260
- 7
- 26
- 33
10
votes
1 answer
Quality factor in antenna matching / question about SX1261 LoRa transceiver
I have a question about how the quality factor is determined for RF antenna matching, especially for PI network matching.
The reason for the question is the Reference Design for antenna matching for the SX1261 LoRa transceiver:
C9 = C10 = 3.3pF, L5…
niklas
- 103
- 5