Questions tagged [coupling]

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Regarding Magnetic coupled circuit

Here, all the initial conditions are : i1(0-)=0A and i2(0-)=0A When t≥0, the current i1(t) and i2(t) starts flowing. From my assumption, steady state value of i1(t) is 10A but what happens to i2(t)? ...
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41 views

Output AC coupling: upper limit or lower limit?

I bought a DC2900A board for my project. In its datasheet it is stated: The maximum repetition rate of the pulsed laser should be 100kHz. The DC2900A repetition rate is limited by the output AC ...
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54 views

Why are the coupling capacitors needed in this DCM converter?

I have a 48V power supply which needs to be converted to a 12V output. I want to achieve this by using the DCM2322 dc/dc converter. In the Datasheet the following recommended circuit is given: My ...
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1answer
25 views

Understanding of coupling coefficient and power transfer efficiency

I am a bit confused about my derivation to get power efficiency from the coupling coefficient. The coupling coefficient \$k=M/\sqrt{L_1L_2}\$. $$ V_2=M\frac{dI_1}{dt}=L_2\frac{dI_2}{dt}\\ V_1=M\frac{...
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1answer
66 views

Location of AC coupling capacitors

I am trying to decide location of AC coupling capacitors between FPGA and PHY SGMII interface and datasheets of neither part has any useful information. I've read some notes, like this one from Dr. ...
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2answers
50 views

Oscilloscope probe coupling [duplicate]

I am using this buck converter. Schematic: Buck Converter Specifications : Input Voltage - 18V to 32V Switching Frequency - 300kHz Output Voltage 9V Load Current - 0mA to 200mA Maximum. When ...
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4answers
184 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
55 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
63 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
94 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
72 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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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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22 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
64 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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198 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 ...
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2answers
86 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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73 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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58 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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85 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 ...
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1answer
113 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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1answer
74 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
149 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
132 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
165 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 ...
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1answer
67 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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125 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
438 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 ...
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3answers
109 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 ...
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1answer
310 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
117 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 ...
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2answers
633 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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60 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 ...
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2answers
416 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 ...
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1answer
157 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
387 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 ...
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1answer
130 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 ...
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3answers
230 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
2k 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
68 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
790 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 ...
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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
324 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
112 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
1k 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 ...
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1answer
221 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 ...
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1answer
57 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 ...
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2answers
651 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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469 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 ...