# Questions tagged [impedance-matching]

Impedance matching is a process of making one impedance equal to another another.

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### 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 ...
705 views

### terminated cable capacitance

As much as I know, the input impedance of a coaxial cable with a characteristic impedance of 50 $\Omega$ which is terminated with a 50 $\Omega$ load resistor, should be 50 $\Omega$ as well. This ...
330 views

### How are the positions of matching network elements determined for RF power amplifiers?

I asked an electrophysicist and he gave me a wishy washy experimental answer. Let me provide an example. Let's say we want 50 ohm input and 50 ohm output from some particular wideband amplifier. The ...
59 views

### Impedance for a communications console

I'm working on some old school Zetron consoles for my summer job. They provide 2/4 wireline control to some base radios as well as I/O for aux operations like triggering relays to open/close doors ...
1k views

### Tapering of planar waveguides

Can anybody recommend some literature or explain some rules of thumb for tapering planar waveguides? As I understand correct tapering is needed for example for bended waveguides or like in the picture ...
8k views

### 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 ...
3k views

### matching input and output impedance in an audio circuit

I have searched many places but have failed to get a clear and convincing explanation about why we match input and output impedance in audio circuits. For example: lets consider a simple audio circuit ...
2k views

### 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. ...
397 views

### How does less cable impedance, source/termination impedance, lead to longer cable length for higher data rates?

This question is about high speed digital transmission on a transmission line, I need to know about how does the (1) impedance of the transmission line and the (2) source impedance and (3) ...
16k views

### 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 ...
10k views

### Convert Iphone 3.5mm pin to standartd Samsung Android 3.5mm pin

This is a simple question. I want the new Iphone EarPod to work with Samsung/Nokia phones. I tried to use the headphone to Samsung phones. Here is the result Here is the Universal 4-pole Cell ...
1k views

### Problem with microphone powering up a comparator circuit

The circuit below is supposed to turn on a LED when the microphone input reaches these levels: 1V, 3V, 5V, 7V. What this circuit does in real life is when we turn on the power, all 4 LEDs light up. ...
3k views

### Cable Splitter Loss and Impedance Matching

From my memory, cable splitters (such as for splitting a cable tv coax cable into two televisions) provide impedance matching to prevent signal reflections, etc. If one 50 Ohm line is split into two ...
2k views

### Matching RF traces

The datasheet for this part states the input and output are internally matched to 50 ohms. However what exactly does this mean? For example the output, would I still need a 50 ohm microstrip to ...
9k views

### 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 ...
3k views

### The "10x rule" for impedance bridging

Quoting the Wikipedia impedance bridging article . . . A connection is commonly said to be bridged if the load impedance is at least ten times the source impedance. Why the magical numer 10? ...
515 views

### How to go about designing an impedance matching circuit for microphones

I have a black-box circuit attached to a condenser microphone. I would like to replace this condenser microphone with another. I have output impedance data for both microphones across frequency. The ...
2k views

### Impedance Matching for Short-Low Frequency Traces

Is it necessary to have impedance matching for short PCB traces if the frequency is lower than say 100MHz ? I've read somewhere that for a trace to be considered a transmission line it should have a ...
671 views

### Radiation Resistance of a Straight Wire Antenna

I am new to antenna theory, and I have been reading up on antenna properties to create my own antenna. I want to use a piece of copper wire, maybe around 18 gauge, as a monopole antenna, but it will ...
541 views

### Circuit that dumps RF energy on matched load. Can anyone help?

Background Trying to protect my home against the RF irradiation by cellular tower nearby. Read an article that proposes 2 things: Metal film, or fine metal mesh, which is grounded. This is used on ...
474 views

### Help with Matching circuit

I'm using a SAW filter which has balanced input and output. In the datasheet there is shown a matching application for 50ohms balanced output. But plotting the S22 parameters into a Smith Chart and ...