Impedance Definition and 507 Threads

Help finding the load impedance of a transmission line? How do you find the load impedance of a transmission line?

So we are told in our class that the characteristic impedance of a coaxial cable is impractical to be at a value like 500Ohms. Why is that? The assumption is that the transmission line is lossless and that the dielectic constant (Er) is 1

After googleing the formula to calculate impedance of a radio antenna, I came up with this formula Z = R + jX where X is reactance and R is resistance. I figured resistance could be measured with an ohmmeter. Then, it seems like there are two kinds of reactances, capacitive and inductive. The...

See the circuit diagram attached. The voltage source is a sinusoidal AC source with amplitude = 240, Frequency = 50, Phase = 90. Essentially I have a lab report and I was wondering what sort of equations are required to find the impedance of the circuit. We're not really told if we're...

Homework Statement Time-domain expression for i(t), based on measures above: Time-domain expression for i(t), based on measured R and L: Vp-p on 16Ω resistor: 7.25mV "measured above" Ip-p for resistor: 0.676mA "measure above" Ip for resistor: .338mA "measured above" R: 14.8Ω L: 10.1mH...

Hello, i just want to clarify, is there a difference between the inductor impedance or inductive reactance XL. inductive reactance XL = 2pi*fL is this the same for inductor impedance? i see on an example where they ask you to calculate the reactance in a series RL circuit. V= 100, f=...

I have somehow worked myself into a mental loop that I need a push to break out of. Consider an inductor in series with a resistor. In sinusoidal steady state, the combination has an impedance Z = R + jωL. The admittance is given by (1/Z) = (R-jωL)/(R2+(ωL)2), and if R is zero, it is simply...

Hello all, In one of our labs we determined the input impedance of a FET amplifier circuit via a potentiometer. We were told it was due to "maximum power transfer theorem" (something we have not learned yet). Essentially we attached a potentiometer in series with the input of the circuit and...

Hey all, Between two devices, I will need to have a coaxial line (with SMA connections on either end) connecting them. The operating frequency of the signal I am propagating is approximately 125 MHz. With this said, the wavelength (assuming ideal) is 2.4 meters. I have heard from numerous...

Homework Statement I understand power factor is defined as (average power)/(apparent power) or cos(theta v - theta i) where theta v = load voltage and theta i = load current. Also the power factor angle is equal to the load impedance. I don't understand how the 2 definitions of power...

The voltage is large AC signal, not small AC. I never deal with this kind of biasing... I am doing some simulations to extract the impedance of the device. I heard about some ways to measure it, like load pull, S parameter. But I can't not do measurement now... The device is quit...

Hello. In a class today, the lecturer said, in an introduction to the material that will be covered, something along the lines of "..and the current is kept relatively flat (low?) thanks to impedance ..." Is this because impedance acts like resistance (but in AC circuits), or would there be...

i have a coax cable that will be used in data transmission. i have measured the open and short impedance and then characteristic impedance(Zo) for the cable. Eventually I will have a transmitter with Z_source in one end of the cable and receiver with Z_load at the other end of the cable. Is it...

I know what impedance voltage is. I will state it just make sure we are talking about the same thing. Impedance voltage is relative short circuit voltage, when secondary of a transformer is short circuited, and we are slowly raising the primary voltage "Vpr" until the current at the secondary...

A bit confused about direction of current flow in the BJT equivalent ckt. I'm trying to calculate the resistance seen, looking into the emitter terminal. In what direction does the current flow in the bjt output resistance ro?

In the equivalent diagram of BJT, Vbe and rbe represent the base voltage and resistance. gmVbe is a current source, which represents the current gain. Since gm = Ic/Vt Vt/Ic = 1/gm Does this mean the impedance of the current source is 1/gm ? I know this sounds a bit weird. It's because...

Homework Statement Find input resistance of the ckt (see attached) Homework Equations The Attempt at a Solution Q2 is diode connected, so I replaced Q2 with VBE resistance (rbe or r∏). So, Rin is rbe1+(β+1)rbe2 But the answer is somewhat different, it's rbe1+ (β+1)...

Hi, I need to write a c++ program that calculates the total impedance of a simple RLC circuit. I'm given the values of each component (resistance, coil, condenser). The programming part is not a issue however I can't find the formulas for the impedance on the internet. Can someone help me out...

Why is so much emphasis placed on matching the impedance of a feed line with an antenna? Shouldn't the emphasis be placed on matching the internal generator impedance AND feed line with the antenna instead? That is, you take the impedance of the source, transform it using the transmission...

Homework Statement We have a resistor R1 in series with a capacitor C1, then we have a capacitor C2 in parallel with a resistor R2 I don't want to achieve the whole question, just the start as it is confusing me. Homework Equations 1/Rz = 1/r1+1/r2 (parallel) The Attempt at a...

If I have a cable of 84 ohms of characteristic (or surge) impedance (which is independent of length) and whose DC resistance is far greater than 84 ohms (let's say 840 ohms), would I get, by hooking up a capacitor charged at 12 volts across it for a very short period of time (let's say 1...

Hi, I am trying to understand the calculation of the characteristic impedance of a CPW ground. I need to get an analytical expression for the impedance. My first step was to read the book: "Coplanar_waveguide_circuits__components__and_systems" Here is what I don't understand: the...

Hi, I am trying to model electrical equivalent of a coaxial cable. The data I have is 1. Conductor resistance 2. Insulator resistance 3. Partial discharge 4. Insulation Thickness 5. Overall diameter Actually I planned to use an equivalent circuit that has series connection of...

i have designed my circuit, but i am confused about impedance matching. i know we can use a resistor for matching, but is it possible to use a capacitor or inductor for matching the impedance in a circuit.

I need to connect the transformer to an 5V open-collector source as shown below, but the load must not see a larger impedance than 50Ω. The 5V source is an internal source to the driver and not available outside of it. As it stands, the seen impedance will be 5k when the bjt is off, so this will...

I'm trying to solve this problem and the first 2 questions on it are giving me a tough time. Picture Attached. (1) Determine the equivalent impedance Zeq of the OpAmp circuit. Assume that the OpAmp is ideal. (2) Determine Rx, Lx, and Ry as a function of R, R1, and C such that Zeq of the...

I need help calculating the magnitude of the impedance for a RLC circuit shown below. See the attached schematic. I found the impedance magnitude of a similar circuit here: Impedance Formulas ...see the 4th circuit from the bottom (let's call its impedance Z_a). Unfortunately, I do not know...

Homework Statement I have this circuit: 0----------C----------0 U1___R C I1 I2 R C ___U2 0---------------------0 That's supposed to be two sets of Resistor, Capacitor, and dependent current sources all in parallel except with a capacitor separating the dependent current sources...

A 400 Ohm resistor is connected in series with an inductor of reactance 300 Ohm and a capacitor C, and a 50 V voltage is applied to the circuit. Find impedance. Is it possible to calculate it? Am I missing something or I would need Xc or I to do that? Thank you for a hint.

The concept of output impedance is highly confusing to me. I will be thankful if some body gives simple explanations to the following. 1. I undertand that in the case of current amplifiers, the out put impedance should be low and the input one should be high. In the case of voltage...

Hi I'm doing simulations in preparation for experimental measurements of decoupling capacitor parasitic inductance. I've done simulations of two port measurements, in mentors hyperlynx, of parallel capacitors on small power planes. These have given me s2p files that I've converted to...

Can someone explain to me the following: I have been told that acoustic impedance is analagous to mechanical impedance. For mechanical impedance (Z), Z = force / velocity and for acoustic impedance (Z), Z = pressure / flow However, in the mechanical case, force refers only to...

Homework Statement I know that for air, the intrinsic impedance η is 377 Ω, but it becomes complex in a conductive medium. This fact is sort of hindering me in being able to answer a few problems consisting of electric and magnetic waves in a conductive medium, but I just wanted to clarify one...

Friends: I was recently introduced to a [published] method of calculating the impedance of a metallic cylinder [applicable to both DC and AC] which I thought was interesting but counter-intuitive. This method is: Lets say you have a metallic cylinder that is inhomogeneous. In other words...

Homework Statement Calculate the J notation impedance of the network We have an inductor in series with a resistor and both in parallel with a capacitor. Homework Equations The Attempt at a Solution i believe it is true that if I was to say: if I have an inductor in parallel...

Homework Statement We have a capacitor in parallel with an inductor. These are both in series with a resistor and capacitor. Calculate the J notation Impedance of the network. I only want the initial basic solution. The problem I have is that sometimes the J notation of C is -ve and...

Homework Statement I recently got a problem that confuses for days, the picture for this problem is in the attachment field, is there someone can tell me that, if an oscillator is topology is described using the negative impedance model in the picture, should I have R>r to ensure that the...

Hi people~ My name is Sam, a student just trying to work something out and failed. A little help please :cry: I've drawn it and attached the figure here and if you take a look I have a series ciruit with PZT (some material) and resistor. I need to work out the real and imaginary part...

Hey guys, I’m trying to do a simple experiment where both my DAQ (Data AcQuisition) card and my microcontroller trigger off the same signal. The trigger source is from the Agilent 33210A which is a 50 Ohm impedance output. From that source, I have connected it to both the AlazarTech DAQ...

Homework Statement An aerial feeder cable (characteristic impedance 75Ω) is connected to a long cable of characteristic impedance 120Ω. If a 100μV signal is received at the aerial, calculate the amplitude of the signal transmitted into the second cable. What fraction of energy is carried by...

Hi I am a bit unsure about terminology and method, so I would like to discuss this with anyone who knows anything about this. I'm examining the properties of a network of parallel capacitors. I have calculated an impedance versus frequency curve, Z(f), using complex impedance of the...

I'm having trouble finding the impedance of the simple given network below: I know Z(s) of each capacitor is 1/2s, but I'm confused on what's in series/parallel. How can you tell? I know it has to do with the nodes. Any help would be appreciated.

The power stored in an inductor is E=0.5LI2 which is independent of frequency However, the impedance is ωL. So, what makes the impedance increase with frequency?

Hi, I have a couple questions regarding a homework problem and would really appreciate some help. Consider the lossless 50ohm transmission line shown below, which has an LC circuit inserted at some point along the line. If I want to find the input impedance how would I approach this problem...

In the case of a complex source impedance ZS and load impedance ZL, maximum power transfer is obtained when ZS = ZL*. For a lossless transmission line terminated on one end with a purely resistive load, zero reflection is obtained when ZS=ZL. What about the case of a lossy transmission...

Hi I'm looking at an impedance curve of a non-ideal tantalum capacitor in LTSpice. The test circuit and impedance curve is seen in this screengrab: http://www.apspektakel.com/bilder/tantal.png" The spice file is here http://www.apspektakel.com/bilder/tantal.asc". So, the imdpedance curve...

Homework Statement a) Determine the impedance of this circuit. b) What is the impedance when \omega = \frac{1}{\sqrt{LC}} Homework Equations The Attempt at a Solution EDIT: I got the Z wrong. It's Z = \frac{L}{C(j{\omega}L - \frac{j}{{\omega}C})} For part b, I'm...

Hi ... my equations is : 1- if the refractive index of the dielectric material related with frequency ? if yes , is that because the permittivity relation with frequency or permeability or both of them ?. also i want the equation of refractive index relation with frequency. 2- in...

Hello everybody, I've often read that if a light ray travels from a medium 1 to a medium 2 and the two media have the same impedance, there is no reflected light at all, only transmitted light. So i made some calculations assuming to have two media with two different refractive indexes but same...

Okay, I know in standard inductors the coil itself causes electrical resistance when AC current is passed through it, but I was wondering if a superconductive coil below its Tc has the same effect? Is there any impedance because the meisser effect does not allow outside magnetic fields to...