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# Questions tagged [impedance-matching]

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

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### Correct connection of a Wi-Fi board having both printed antennas and U.FL sockets

An RF part of a dual antenna Wi-Fi module from Aliexpress. We can see coax sockets connected in parallel to printed antennas. Two external antennas and corresponding pigtails are part of the package. ...
4 votes
2 answers
990 views

### Which is preferred over differential pairs: trombones or sawtooths?

I have been told that trombones are much better to use than sawtooths, even if sawtooths may be prefered in some certians scenarios. Here I have added trombones to the differential pairs. If I had ...
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3 answers
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### Is it possible to simulate reflections by designing an RLC transfer function?

Assume that you're knowing the PCB stack and the geometry of the conductor. You're computing the capacitance per mm and inductance per mm and also the total resistance of the conductor. That means you ...
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### Difference between characteristic impedance vs complex impedance

Are there any differences between complex impedance of antenna pcb trace vs characteristic impedance of antenna pcb trace. This question rised up because of online pcb trace impedance calculator doesn'...
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3 answers
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### How to match multiple impedance discontinuities?

I am trying to design a circuit to transmit various digital high frequency signals over cables, connectors and pcb to an oscilloscope. The simplified circuit looks like this: simulate this circuit &...
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1 vote
1 answer
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### Impedance of different track widths - Should I compute the average width?

Assume that you having one track that goes from 0.11mm in width to 0.09mm in width. I want to compute the impedance, but I need to select the width. What option should I select? The largest width of ...
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1 answer
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### RC filter cutoff and impedance

I wanted to create RC lowpass filter with cutoff frequency 15 kHz and output impedance 50 ohm. What should be R and C values? I'm a little confused how to interpret 50 ohm output impedance to ...
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1 answer
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### Match 50 ohm impedance to LNA input impedance

I have following PCB version of circuit: on SMA input we have antenna strictly matched to 50 ohm, then we have regular RF switch IC, after RF switch impedance matching network and final stage is ...
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### Operational amplifier layout- Controlled impedance

In the following picture, we can see a reference layout by Texas instrument for OPA838: I noticed, in the polygon on the top layer, they have used a specific gap=0.5 mm, I wonder if they used a ...
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1 vote
1 answer
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### Layer stack up and impedance matching- 100 ohm

I have a 14 layer stack up as follows (the stack up is from EURO circuit): I need to provide 100 Ohm differential impedance for my LVDS on layer 7, currently by the information from the manufacturer (...
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1 vote
1 answer
137 views

### Calculating output impedance of amplifier to match to 50 Ω

Below is a schematic of an amplifier. The inductor used is a 1 μH inductor, emitter resistor is 2.2 kΩ. The bias resistors are both 200 kΩ. The capacitors are both 1 μF. I am planning to design a ...
2 votes
1 answer
53 views

### understanding the recommended impedance match for a SAW filter

I'm trying to understand the recommended impedance match for a TA0168A SAW filter input. The datasheet is https://www.rfmw.com/datasheets/taisaw/ta0168a%20_rev.2.0_.pdf In my first circuit I'm trying ...
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1 answer
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### Wideband Impedance Matching for Inductive Source/Load

I'm designing the frontend of a receiver and I want the output impedance to be 50Ω so that I can get as much power into the mixer. I tried placing a bandpass filter (image filter for 88-108MHz) in ...
2 votes
1 answer
95 views

### Optimal thin absorber of electromagnetic energy

I am a material engineer and have a question about a formula derivation regarding microwave absorption properties. I really cannot figure it out after days of trying. This should be simple for a ...
1 vote
1 answer
126 views

### Matching circuit for piezo transducer

I am at the stage of designing a system that match impedance of the power output (half-bridge) to a piezo transducer operating at 1MHz (Max 60W of power). I calculated the piezo parameters from the ...
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1 vote
2 answers
72 views

### Is the reason for guitar "tone suck", i.e. loss of high end frequencies with impedance mismatching, actually due to high reactance?

When connecting a guitar's output to an input with insufficiently high input impedance, the signal is undesirably filtered, which is referred to as "tone suck". To deal with this, it is ...
2 votes
0 answers
42 views

### How to create schematic of common mode choke that reflect on Common mode, differential mode and mixed mode? [closed]

I aim to create a schematic that can replicate the results exactly as seen in the measured S4P file. I have conducted the measurement using a VNA and am attempting the schematic simulation in CST. ...
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### How to reduce on-resistance and parasitic capacitance effects of my MUX setup?

I am designing a mux board to mux a flashing setup. Both UART and SPI lines are on 1.8V logic. The Mux chips have ~4-8ohms on-resistance and 1.7pF on-capacitance. Few questions: Would I need buffers ...
0 votes
1 answer
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### Coax cables, impedance matching and BNC extensions

I'm trying to understand how to do proper measurements with a Voltage Differential Probe ( TT-SI 9010. This probe has an output impedance of 50ohm and has a BNC (It doesn't specify it in the data ...
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2 votes
1 answer
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### What is the purpose of a shunt element in a balun?

I'm working on a balun for a differential front-end receiver and see that they quite often use a shunt element (inductor) across the differential pair. From what I could gather is that when you insert ...
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2 answers
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### Balun converting 100ohm single-ended trace to 50ohm single ended for spectrum analyzer

On my board, I have 100ohm differential pair traces connected to a 1:1 balun, so the signal impedance becomes 100ohm single ended. I would like to measure the signal spectrum with spectrum analyzer. ...
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1 vote
1 answer
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### Coax cables and input impedances

I'm doing a voltage measurement with the help of an Active Differential Probe (TESTEC TT-SI 9010) with an output voltage of +-7V. This voltages have rise times of the order 500ns. The set up looks ...
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2 votes
1 answer
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### Incorrect Output of RF Mixer

I've designed a RF mixer (Gilbert Cell) which takes a RF frequency between 88-108MHz and a LO of 77.3-97.3MHz, I want to take the difference between the two so the IF is 10.7MHz. Currently, the output ...
0 votes
0 answers
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### Is it possible to implement shunt stubs to replace shunt capacitors for differential matching?

I am reviewing the subject of stub matching. For example, consider Network D: Example photo screen-shot from TI documentation: https://e2e.ti.com/cfs-file.ashx/__key/communityserver-discussions-...
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3 answers
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### Can I add a resistors to add speakers?

I have a 2 channel stereo output from my laptop connected to a surround sound amp: all 5 speakers with an impedance of 4 ohms (front, rear and sub) play the stereo sound. The speaker connectors on the ...
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### Chip antenna matching of a custom board equipped with a STM32WB55

I am planning on designing a custom board using a STM32WB55. I have followed the "How to develop RF hardware using STM32WB microcontrollers" (AN5165) Figure 9 design for the RF part, which ...
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2 votes
0 answers
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### Challenges in Bandwidth in Common mode Choke Modeling

I'm currently working on characterizing a common mode choke (CMC). However, I'm encountering difficulties aligning the bandwidth of my model with the measured results. Specifically, when I attempt to ...
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2 answers
138 views

### Why don't people always use 50 ohm resistors when matching impedances?

Impedance matching when designing the RF receiver circuit and antenna design takes a lot of time and effort for VNA. People often use capacitors and inductors to match the impedance of the antenna ...
3 votes
1 answer
87 views

### Which antenna trace design is better?

I need to design an antenna trace (WiFi and Bluetooth) that connects an ESP32-S3 chip to an IPEX connector with an impedance matching circuit. I have some constraints that I need to work around: ...
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1 answer
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### Where do I place my matching network for an antenna?

Let's say I have a microcontroller with an antenna output. The characteristic impedance of the pin for the antenna output is x+jy. I want to then connect it to a 50-ohm antenna. This is the part that ...
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1 vote
1 answer
35 views

### Slight difference in equations for the design of resistive matching network

I'm currently reading trough an application note from Analog Devices 2, in particular the "A NARROW-BAND LC MATCHING EXAMPLE AT 100 MHz" section. I re-did the calculations by hand and got ...
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8 votes
4 answers
1k views

### Impedance matching and termination resistor

I’m a little confused regarding impedance matching with resistors. As far as I know, the impedance of a trace is a part of its characteristics and it can’t be measured with an ohmmeter. For example, ...
1 vote
1 answer
55 views

### Confusion About Impedance Matching For Single-Ended and Differential Lines

I understand that for single ended RF signals I must ensure that the characteristic impedance of the transmission line matches the load impedance (say 50 ohm). I am a bit confused for differential RF ...
1 vote
0 answers
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### how can I calculate impedance matching for STM32WLE5 RF network?

I am attempting to compute an impedance matching network by following the guidelines outlined in the ST Application Note - AN5457. However, on page 24, the formula and calculations appear perplexing ...
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2 answers
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### How to design an RF frontend for an FM receiver

I'm designing a RF receiver for FM Radio. I simulated the circuit in LTspice and got an output as shown below: This is OK, but I would like the gain to be 24 dB across the range of 88-108 MHz. The ...
1 vote
1 answer
50 views

### Connecting multiple loads in self-balancing parallel [closed]

I have three (or 'n', where n=3 at the moment) large LED panels that I want to run in parallel. As we know (or should have known before the 'royal we' actually tried it!), just wiring them together in ...
1 vote
1 answer
43 views

### How can I calculate filter parameters between RF switch and antenna?

In the schematics en.MB1389-WL55JC-highband-E02_Schematic, there's a Pi filter following the RF switch before it links to the SMA connector for the antenna. Upon calculation, I found that the cutoff ...
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1 vote
1 answer
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### Intuitive explanation of shorted stub behaviour

Can someone please give me an intuitive explanation of shorted stub behaviour? NOTE: This is not a duplicate of Intuitive explanation of open stub behaviour which has been narrowed to focus on open ...
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2 answers
189 views

### Intuitive explanation of open stub behaviour

Can someone please give me an intuitive explanation of open stubs? I have the length-based mathematical derivation and explanation from my textbook, but I am looking for an intuitive one. For example,...
1 vote
1 answer
61 views

### External circuit to increase the series capacitance of a resonant circuit

I am working with a long-range reader and antenna coil for a low frequency (135 kHz) RFID application (please see the basic representation below.) The reader features some unknown source impedance, as ...
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4 votes
1 answer
547 views

### Why can domestic induction stoves heat aluminium tape, but not aluminium pans?

Domestic induction stoves can't be used with thick aluminium or copper pans, but when I try to heat aluminium tape it does get hot. Can someone explain why this is the case?
2 votes
2 answers
210 views

### 75 ohm cable in an otherwise 50 ohm antenna system: Can I impedance match it?

I have an marine radio antenna installation as shown in the diagram. Can I place baluns (or similar devices) at either end of the 75 Ω cable to solve the impedance mismatch problem? Background In ...
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1 vote
2 answers
217 views

### Half Bridge Impedance Matching

I’m currently building a half bridge induction heater and can’t understand impedance matching for the life of me. Here’s an example of a basic half bridge induction heater. How and why was 45uH ...
1 vote
2 answers
102 views

### Via process when implementing GCPW in RO4003 + FR-4 multilayer structure

I am currently developing an RF board that receives up to 8GHz. The board consists of a multi-layer structure combining Ro4003C (8mil) and FR-4. The connector I will be using for the RF board is a ...
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### Signal Generator Output Impedance Matching and Floating Ground

I am attempting to recreate a signal generator circuit based on the XR2206, as seen in this video. The schematic uses op-amps for offset cancellation and output amplitude matching. To avoid the need ...
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2 answers
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### Antenna tuning and L/C matching

I see there are already a few questions asked wether it is better to physcally tune the antenna for said frequency and impedance or use a matching network. It seems the conscenus is often the physical ...
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3 answers
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### How best to match and ground antenna?

An example of RF AM modulation: https://www.ee-diary.com/2021/12/am-modulator-using-bjt-transistor.html It is clear that the output is on point C4 and the circuit has a RF function, so I need an ...
0 votes
2 answers
73 views

### How to calculate output impedance of switching regulator?

If I consider a buck converter where in 24 volts, L =100 μH, capacitor 47 μF. Then converter will operate at 400 kHz. How do I calculate the output impedance of the converter?
0 votes
1 answer
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### LTspice - auto-transformer impedance ratio

Can you please clarify what formula is used by LTspice to calculate the auto-transformer impedance transfer ratio for the equivalent circuits below? Both circuits resonate on the same frequency. I ...
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1 vote
1 answer
106 views

### Why is the current angle negative?

I don't understand why the current angle is negative.
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