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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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### Impedance matching for an antenna

I've been working on a project for school which involves designing matching networks for antennas (meant to be driven at 2.4 GHz) being connected to a 50 Ω line, and it led me to consider the ...
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### Eliminate reflections on pulse signal transformer

I am trying to isolate an RLC ringdown signal via an RF signal transformer but I'm having trouble maintaining the signal integrity through the transformer. Below is the simple schematic describing my ...
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### When are 1:1 baluns worth it?

I am trying to build an antenna to connect to the GOES-16 satellite (downlink at 1690,1MHz, linear polarization) with my SDR. My plans are using a 1m offset parabolic dish with a BiQuad feed, ...
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### HDMI: What is the maximum acceptable differential impedance variation and for which length

Imagine I have a HDMI bus with differential impedance 100 Ohm and length 10cm Imagine that for a segment of length "L" there is an impedance variation of "DELTA" Question: in order ...
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### When should an unmatched antenna be measured with a cable length in even multiples of a half-wavelength?

A few years ago someone told me that if you use a cable which has a length of an even half-wavelength multiple for the frequency being tested, then the impedance measured at the end of that cable will ...
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### Transistor impedance

According to LDMOS transistor AFT05MS031N datasheet at p. 13 " ZSource - Test circuit impedance measured from gate to ground" for 155 MHz is Z = 4.31 + j.7.54 https://www.nxp.com/products/...
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### Function generator impedance matching with an amplifier

I am currently designing an experiment with a material which at low temperatures (below 180K) works like a light detector for infrared. There needs to be a bias applied to the sample which has to be ...
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### What is the link between conjugate matching efficiency and amplifier efficiency?

In the design of a class AB amplifier, there is part of the understanding that I miss. It is well-known that the maximum power transfer is achieved when the load impedance is the complex conjugate of ...
172 views

### SX1262 Matching impedance

I want to build a LoRa node from SX1261 which works on the frequencies of 868Mhz and I found at the manufacturer the following assembly ms I did not find more details on the different passive ...
328 views

### Calibrating a VNA

I am using the Siglent SSA3032A-R spectrum analyser which has a Vector Network Analyser (VNA). Before measuring the impedance of an antenna under test so that I can match this antenna, I have to ...
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### Antenna matching using L-sections does not always yield a "matched" solution

I created a program to compute the component values of a T network to match a reactive load (R+jX) to a 50 ohm source, based on the procedure outlined by M. Walter Maxwell in his book "...
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### Different trace width signal transmission line

I have a really basic question. I am wondering what happens physically with the signal, if I have a change in a trace width (see picture below). My point of view is that you have a reflection of the ...
414 views

### Impedance matching of a RF power amplifier based on the s2p file

I'm designing the input/output impedance matching circuit for a RF power amplifier, based on the vendor supplied s2p file. I designed separately the input/output matching circuit at the given working ...
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### Modern piezo microphone impedance-matching circuit

I want to record sound with a piezo transducer. I am connecting it to my sound card's input which has a good mic pre-amp. The levels are quite good and the sound seems quite clear but there's a lack ...
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### Keep potential difference fixed for transformer's output

I have a source consisting of V1, R1, L1, and L2 to which my load R2 is attached: For the load, I have 10 or 100 Ohms. 1) R2 = 10 Ohms: Vrms = 315 V, irms = 32 A, P = 10 kW 2) R2 = 100 Ohms: Vrms =...
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### Resistive on-die termination

It is widely known that resistive termination (e.g. 50 Ohm to ground) is superior when noise is no concern. Specifically in the block diagrams of RFICs I see many 50 Ohm resistors to ground directly ...
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### Resources for impedance matching networks

I am working on my first hobby PCB design project that includes RF components. On one hand, I have a 2.5GHz WiFi signal and an 868Mhz LoRa signal. I copied the matching networks from the reference ...
1 vote
92 views

### Impedance matching 133 MHz - Topology and terminating resistor concerns

I am using the QSPI bus of the RP2040 to talk to a flash chip. I am also putting 8 more chips (PSRAMs) on that bus in my design, and a second RP2040 to load them. The datasheet for the RP2040 isn't ...
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### Measuring a balanced matching network

I'm working with a Silicon Labs EFR32G12 Wireless MCU and I'm following their design guides for developing the matching network for the device. However, I saw that in one of their design notes (here), ...
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### How do you "calibrate" (?) a matching network to re-optimize an S11 match based on physical measurements from a VNA?

We made EDA simulations to match an LNA input and had good results on the simulation (including EM simulation!) --- but when we built the board in real life the S11 match went from -30dB to -7dB. Ouch....
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### At which point do we take the value of impedance to tune an antenna?

I am a beginner in antenna design and tuning. I want my antenna to have a resonant frequency of 2.45GHz for low-energy Bluetooth communication, and I want to know what to consider for the matching ...
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116 views

### "Short" calibration

The following section from ST Micro's AN4974 - 'Antenna Matching' app note is a bit of a mystery. Is there a VNA / network analyzer guru out there who can tell me what the 4th line there is saying? I ...
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### Designing of a ribbon microphone (sort of) output transformer

I'm currently working on an experimental string musical instrument. It isn't my invention though. The source of inspiration called Dvina has an unusual pickup system. It senses the current induced in ...
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### ST32WL RF Matching Network

I am adapting a minimal design based on the TTN Generic Node. I am trying to reduce the BOM and do not require the option to switch power. In the following diagram there are 4 RF signal I/O pins, 2 ...
1 vote
60 views

### Impedance matching of an antenna with a cable

This is sort of a conceptual question. Suppose I have an antenna that is connected to a PCB via a 50 Ohm coaxial cable and a U.FL connector which is fed by some 50 Ohm PCB trace. Take this antenna for ...
1 vote
1k views

### Impedance matching for ESP32-D0WD-V3 QFN 5x5 connected to uFL port

I'm designing a PCB that uses a ESP32-D0WD-V3 QFN 5x5 and I want to have a uFL port for 2.4Ghz Wifi/BLE. Directly from the datasheet, I get the following note: The output impedance of the RF pins of ...
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153 views

### Understanding the input characteristics of an RF power transistor (2SC2237)

I've had this 2SC2237 RF power transistor from Mitsubishi for quite some time and I've finally found a project for it. The datasheet can be found here. The first thing I need to do is figure out its ...
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### Antenna matching circuit - weird behaviour

I have a 2.4GHz device with room for a Pi matching circuit. I cut J5 (to disconnect the MCU - brown line in layout picture), soldered the ground of the coaxial cable in the white region and the ...
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### Matched termination of a microstrip using absorber foam

I have open ended microstrips in an RF circuit (operation freq. 18 GHz) and they cause unwanted back reflection into the rest of the circuit. Now, I wonder if it is possible to eliminate / reduce ...
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### How to match Transformer output Impedance for Ultrasonic Cleaning Transducer

I have a transformer outputting the 240VAC 40kHz. The Transducer is 50W, 4100pF, 10-20 Ohm at resonance, ~40kHz resonance) The Secondary of the transformer is 12mH. I am trying to match the impedance ...
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1 vote
128 views

### RF output matching using baluns: LTC6946

The datasheet that I refer to below can be found here: https://www.analog.com/media/en/technical-documentation/data-sheets/6946fb.pdf I have a question about baluns. In the datasheet for LTC6946 ...
1 vote
86 views

### Impedance matching on oscillator

I have built an oscillator configuration at 4-7GHz. At 5.29GHz, the output of the oscillator has resistance R=-189-j*51. How can I use impedance matching and a bandpass filter since I have a negative ...
1 vote
138 views

### Controlled impedance traces necessary between line driver and series termination resistor?

I'm designing a line driver circuit with the SN74BCT25244 chip. The chip has a rise time of ~10 ns into an open circuit based on my own scope testing, but we are only wanting to drive the signal at a ...
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### Why is an attenuator placed on the scope end and not the PCB end?

I've noticed when adding an external attenuator between PCB and the scope (1MOhm) that it is placed in this manner: PCB -> SMA Socket -> SMA Cable Plug -> SMA Attenuator -> SMA-to-BNC -> Scope Why ...
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### Determining Z1 for voltage divider of RF Matching Circuit

I have a problem where I was given an RF circuit with a series RL load. I am tasked in finding a matching L circuit and determining the values of the components. I used a smith chart to determine that ...
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112 views

### Padding/impedance matching of a phono input

My old stereo amp got coffee spilled on it. I replaced it with the latest model from the same manufacturer. I am an old-world person, and prefer simple approaches - i.e., radio buttons to select ...
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### Is this an Impedance Matching Curve?

This may be a very quick answer, I had a test that was set up like this. The primary inductance of the transformer was roughly 0.022H and the inductance of the secondary of the transformer was 0.045H. ...
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113 views

### Help needed to design a suitable energy harvester for TENG

I am in the process of desgining a scalable triboelectric nanogenerator (TENG) through which I can easily harvest and store electricity in a battery or a capacitor. A TENG can be modelled as voltage ...
1 vote
175 views

### RFID reader antenna matching

I am trying to connect a RFID reader chip to an W3113 antenna on PCB. As said in datasheets, the antenna pin of the reader chip has internal 50 ohm impedance and antenna W3113 also has 50 ohm ...
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378 views

### Impedance for TTL Hsync and Vsync Pulses

I'm just finishing up a sync combiner and audio/video PCB. I'm trying to impedance match my traces and I've done so for the 75 ohm RGB lines. Now I'm looking at the TTL level Hsync and Vsync lines ...
1 vote
123 views

### Can antenna VSWR be corrected?

For this antenna, which cites a VSWR of 1.4, can that be improved (decreased) with the use of a matching network? Could the matching network be between the feed cable and the board or must it be ...
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### F type female to SMA male adapter impedance question

I have a coaxial cable that I need to connect to a SMA female connect. The impedance of the cable is 75 ohms, and from online the SMA female connect is 50 ohms. Online there are a few places that sell ...
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### LC matching or pi filter used in rf

I am working in RF and if i go through articles it is seen that in every point where the RF signal flows it is said we need LC matching networks or Pi filters, but i cant get the sole reason why they ...
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### Antenna VSWR value and impedance matching claims by the manufacturer

Having larger value of VSWR is indication of improper matching. Eg. http://www.abracon.com/patchantenna/ACA-107-T.pdf this datasheet claims VSWR to be around 4:1 to 5:1 (which seems bad VSWR value to ...
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### Impedance matching a capacitive source

I am trying to work out how to match a current source coupled with a capacitor to a 50 Ω load for maximum power transfer. Specifically, I have a 6 pF PIN photodiode which driven by a 2.5 GHz optical ...
1 vote
4k views

### Drive a 50-Ohm load from a logic gate

I have a device that I'm trying to send a trigger too, it has a 50$\Omega$ termination and suggests a pulse between 2-5 volts, ~1$\mu$s width. The way things are set up, the trigger needs to come ...
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### Antenna Matching 2.4GHz

i'm using a 2,4GHz transceiver with a differential output. A Balun with 50Ω Output is connected. I have 3 free places to add matching Components in π Topology. The antenna is placed on the other side ...
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### When impedance matching networks aren't

As someone new to practical RF design (the theory is easy by comparison!), I have a relatively simple question when it comes to matching networks, and it has to do with best practices. Obviously, a ...
1 vote