Questions tagged [coupling]

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136 views

Roles of the coupling and bypass capacitors in a CE transistor

I wonder what the purpose of the coupling capacitors and the bypass capacitors are and the type of effect each capacitor has on the circuit. As I've understood it, you use coupling capacitors to block ...
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2answers
46 views

What is the right way to measure K on an inductor with three coils?

I have an inductor which has three coils, L1, L2, L3. In normal use L2 and L3 are connected in series, and resonated with a capacitor. L1 would then drive the tank circuit. In Spice, I need the ...
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1answer
50 views

How is this LCD controlled?

Source: https://ozhealth.com.sg/product/genial-digital-thermometer-t15-orange/ I tore down a digital thermometer today (a Genial T15), and the interface to the LCD caught my eye: although there were ...
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1answer
56 views

Why isn't capacitive coupling considered in EMC testing?

It seems like the emissions of interest in EMC testing are radiated and conducted emissions. Is this because capacitive coupling is so weak it doesn't pose a threat to other devices?
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3answers
62 views

DC-DC converter isolation capacitance return path?

For those isolated DC-DC converter bricks like seen in the photo below: The data sheet specifies an isolation capacitance in the order of picofarads. And in order to meet EMC requirements they ...
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1answer
67 views

Find the Q-factor for coils and understand weak power transfer

I built coils for wireless power transfer. Found inductance with a LRC meter. Put capacitors, hoping for a resonant frequency at 300kHz. Student assisted me with a NVA machine where a resonant ...
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0answers
21 views

“Coupling” gain-setting resistors in a single-ended source, differential amplifier?

I am working on a fully differential amplifier design that receives a single-ended differential voltage from a piezo sensor. I computed a theoretical gain and selected appropriate resistors and it ...
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0answers
20 views

Ac current injecton to dc bus

I want to inject a 2V ac sine wave on a 480V dc bus. to protect my ac signal generator from entering high dc voltage I am going to use capacitor as coupling device. Ac generator also should deliver 15 ...
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2answers
59 views

AC coupling of a transistor

So we assume to have proper bias currents flowing in both of the two transistors. What is claimed by books is that a capacitive coupling will not change the bias parameters. But, we know that a ...
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0answers
110 views

Royer oscillator - frequency shifting in WPT

I am having a problem with my WPT resonant application. In my circuit modified Royer oscillator feeds LC tank. Receiver coil nearby is connected to rectifier and variable resistor. I know about ...
2
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2answers
72 views

EMC - conducted emissions - unused wires in cable - puzzling coupling

I am trying to understand the impact of unconnected wires in a cable for EMC conducted emissions tests. My product has a shared unshielded cable for supply and communication (I know it's bad practice....
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0answers
55 views

Where is the capacitive coupling in this adafruit soil moisture sensor?

Here is the moisture sensor: https://learn.adafruit.com/adafruit-stemma-soil-sensor-i2c-capacitive-moisture-sensor/downloads It has a large copper area insulated with soldermask that sticks in the ...
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0answers
51 views

Understanding Ac coupling in this circuit

I'm simulating the circuit below in LTspice and there's something I don't get regarding C3 and C4. Suppose the input signal is a 32 uArms 60Hz current as shown. This value multiplied by the burden ...
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0answers
66 views

How to measure capacitive coupling on pcb traces?

I have bare PCB board (6 layers) with me and I would like to see if my switching signals (60 kHz) have any effect on the sensitive current measurement lines. I just want to know if there is quick ...
0
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1answer
71 views

How to calculate cutoff frequency for a high pass filter in DC biasing circuit

I would like to DC bias an AC signal using a voltage divider as shown in the following schematic. I realise the bias point would be subject to noise from the power rails, but that is not a concern for ...
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0answers
37 views

Finding effective mutual inductance between a parallel inductors and a separate inductor

The effective inductance of two parallel coupled inductors can be calculated as \$ L_{eff} =\frac{ L_{1}L_{2} - M_{12}^2}{L_{1} + L_{2} - 2M_{12}} \$ where \$L_{eff}\$ is the effective inductance of ...
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1answer
67 views

Coupling coefficient of microstrip resonators

I am working in HFSS and I'm trying to determine the coupling coefficient between two microstrip resonators (k) so that I can design a filter using a certain resonator shape. I have the formula I need....
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2answers
122 views

Unintentional capacitive coupling

This question comes from text from the AOE 3rd ed. It's about unintentional capacitive coupling right after differentiators in chapter 1. I've included the text. Please read the first excerpt. That is ...
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1answer
27 views

Does DiSEqC require a DC bias?

The DiSEqC (Di[gital] S[attelite] Eq[uipment] C[ontrol] specification (bus_spec.pdf within https://www.eutelsat.com/files/PDF/DiSEqC-documentation.zip) describes a tone-based serial data bus that can ...
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3answers
122 views

Shifting level voltage of a signal

I have a signal, which can vary from 400 to 7000 Hz approximately. It is a kind of pwm signal and has the time of high level, Ton, 30 times longer than the time of low level, Toff. The shape of the ...
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3answers
137 views

Adding small AC signal to a DC current using inductive coupling

Is it possible to add a small AC current on to a DC current in a wire using inductive coupling from an external source. Or if there is another way, I want to add AC ripples to a DC current. simulate ...
1
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1answer
56 views

What grounding should I use for this capacitively coupled input?

I'm designing a device that will receive and digitize analog video signals. In analog video, it's recommended to capacitively couple inputs. A typical input might look like this: In this case the ...
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1answer
118 views

2n7000 used for inductively coupled load modulation apparently latched

So I've got a fairly basic circuit set up for load modulation of an inductively coupled circuit: A few notes on the above: LC's were designed for 1 MHz but work better at 950 kHz, thus the chosen ...
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4answers
326 views

AC-Coupling on Composite video

Many sources say that composite video input should be AC-coupled. Voltage levels for blank, black and white signal are also specified. How is it possible to detect these voltage levels after AC ...
2
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3answers
101 views

If a PEC surface completely reflects an EM wave, why doesn't an ungrounded shield work?

I was thinking about shielding and its effectiveness. An ungrounded shield doesn't work well for either inductive or capacitive coupling. However, if you think about plane wave theory, a PEC surface ...
0
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1answer
271 views

Coupling PCB traces

In my pcb design I have 2 triangular voltage signals with the following specs: Peak voltage = 300V Rise and fall time= 7us Freq=25kHz (assume a constant current of 0.5A) Because of the limited ...
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1answer
109 views

Could shielding (not grounded) affect signal integrity?

I'm trying to shield 6 flat cables that give me some communication issues because I thought that there might be cross-talk or other sources of interference that cause the problem. The shielding is ...
3
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2answers
522 views

How does placing cap between signal GND and earth GND solve common mode noise?

Thanks in advance for your time. I am reading several articles about differential mode noise and common mode noise. Among which I found the below 2 pretty instructive: https://www.murata.com/~/media/...
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0answers
58 views

Maximum ringing due to inductive coupling

Consider a bundle of wires carrying binary data and the worst case (or almost-worst case) scenario of them switching all at the same time. The wires with their partial mutual inductances would be ...
0
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2answers
327 views

Parallel inductive coupling approximation - coupling coefficient

I have the problem of a few independent current loops (wires) that on a portion of the circuit are close to one another so there will be inductive coupling between them. Each wire, on the portion of ...
0
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1answer
135 views

Crosstalk between AC and DC

First time asking a question but I've come across something I just can't find the answer to. Whether or not it's because a silly question I hope to find out. So I understand that with crosstalk ...
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3answers
323 views

How do I terminate a directional coupler?

I'm using a directional coupler for a radar application using frequencies of 5.3-5.9GHz. The directional coupler linked above is matched to a 50ohm characteristic impedance. How do I terminate the ...
3
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1answer
122 views

Coupling coefficient variation in Wireless power transfer

Question regarding WPT compensation topologies. I'm trying to make a inductive wireless power transfer system where the RX coil can move quite conisderably relative to TX coil and still transfer ...
0
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3answers
205 views

Why does the voltage induced in the receiver coil of this WPT circuit decrease when a load is added (in parallel)?

The following is a circuit that wirelessly transfers power via inductive coupling. The circuit is supposed to power a 12 V 0.15 A DC fan and a typical smartphone, which requires 5 V DC across it. The ...
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2answers
1k views

Mutual inductance vs coupling coefficient

Question regarding this and this question about mutual inductance and coupling coefficient. I'm trying to analyse a two coil system: It consists of two coils like in the picture with 2 cm air gap ...
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2answers
67 views

Is wireless technology only possible due to inductance?

I asked a friend how capacitative coupling works in glass-mount antennas. He said it's like when installing a sound system; where you want to keep the power & audio cables separated, to avoid ...
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1answer
632 views

USB 3.1 AC Coupling Capacitor Implementation

How should the AC coupling should be implemented when connecting a USB 3.1 hub to a USB Type-C connector through a MUX. Is it: Both sides of each MUX. On the switched output of each MUX. On the ...
0
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1answer
56 views

Why are inductively coupled RFID systems put in certain frequency bands when there are no EM waves used?

LF - 125 kHz HF - 13.56 MHz Those frequencies refer to the magnetic field that is used to induce a voltage in the transponder. Can the magnetic fields actually interfere with EM waves in the ...
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1answer
284 views

Help with design a mic preamp with opamps for PGA and ADC

I want to sample an audio source using an electret microphone and analyze the spectrum of it with a uC. I'm interested in the 100Hz-2.5kHz range, so I calculate with these values when I tried to ...
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3answers
106 views

RFID: Why is inductive coupling used instead of EM waves for LF and HF systems?

Is it because of antenna sizes? At 900 MHz a 1/2 dipole has a size of around 15 cm. That would be far higher for 125 kHz, so instead we use coils to power the transponder and use load modulation for ...
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3answers
928 views

AC coupling capacitor in the ground to break the ground loop?

I'm implementing the following audio single-ended to differential converter for an ADC: This is the reference design for the PCM1804 that I intend to use. What would happen if I do this: Would it ...
0
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1answer
174 views

Can someone explain how frequency and inductance affects this pair of coupled inductors?

I am simulating this simple circuit on PSIM; a single-phase AC voltage source connected to the primary of a pair of coupled inductors, with a 12 Ohms load on the secondary side. I want to increase the ...
0
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1answer
54 views

Capacitive coupling: how to collect 60uA from this set-up?

I need to collect at least 60uA via capacitive coupling between a high tension Cu cable with PVC insulation and a connector that is acting as the opposite face of the capacitor (can be a copper plate ...
4
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2answers
557 views

How do coupling capacitors in transistor not affect biasing?

I understand the usefulness of the capacitors in an amplifier circuit but i dont understand why we use one at the input? and how does this not affect the biasing if it removes the dc voltage? Thanks.
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1answer
400 views

Series and Parallel RLC Circuit [closed]

I am trying to build a resonant circuit for data communication between coils. Which would be better, a series or a parallel resonant circuit? What is the difference between them and in which ...
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2answers
126 views

Is this phenomenon capacitive coupling or human antenna effect?

I injected a 90 MHz signal into an electrical cable via a signal generator. And I used a spectrum analyzer to measure the signal strength of 90 MHz at the other end of the cable. Then I found the ...
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1answer
89 views

Coupling between a cable and the main power line: how to measure it?

I'm wondering what's the simplest way to find the value of capacitive coupling between a cable and the main power line (230Vrms @50Hz, I'm in Europe) to use afterwards in some SPICE simulations. I ...
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3answers
908 views

Shock from Capacitive Coupling

In an AC supply which is not earth grounded, I see a small amount of current flowing to ground from both wires of the supply (live wire has higher) even though the circuit is incomplete. It is due ...
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3answers
590 views

How to find coupling and decoupling capacitor values?

I am trying to learn receiver design, one thing I noticed is the use of coupling capacitors and decoupling capacitors and incuctors. There were set of standard values such as 100 pF, 1000 pF or 0.1 uF ...
2
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2answers
290 views

Crosstalk in analog switch

Art of Electronics, 3rd Ed, pg. 179, gives a model for the capacitive coupling between independent channels of an AD7510DI analog switch. The authors ask to calculate the coupling between channels ...