What is line impedance in transmission lines?

The characteristic impedance or surge impedance (usually written Z0) of a uniform transmission line is the ratio of the amplitudes of voltage and current of a single wave propagating along the line; that is, a wave travelling in one direction in the absence of reflections in the other direction.

What is a differential impedance?

Differential impedance is defined as impedance between the two lines when the line pair is driven differentially. This definition effectively makes it equal to twice the odd mode impedance. Common mode impedance is defined as impedance between the two lines when the line pair is driven with common mode stimulus.

What is differential impedance and why do we care?

Simply put, differential impedance is the instantaneous impedance of a pair of transmission lines when two complimentary signals are transmitted with opposite polarity. For a printed circuit board (PCB) this is a pair of traces, also known as a differential pair.

Is USB a differential pair?

In USB, signals are transmitted using differential signaling. USB 2.0 uses a single differential pair of signals, DP and DM. The USB 3.0 specification adds super-speed signaling using two additional sets of differential pairs, SSTX and SSRX, to support a separate, full-duplex connection.

How do you calculate characteristic impedance?

The characteristic impedance is the ratio of the effective sound pressure at a given point to the effective particle velocity at that point in a free, plane, progressive sound wave. It is equal to the product of the density of the medium times the speed of sound in the medium (ρ0c).

How to calculate differential impedance of a transmission line?

First Order Model of a Transmission Line (Loss Less Model) ∆x (unbalanced transmission line) C = C L ∆x L = L L ∆x capacitance inductance (loop) The circuit analysis result: Z

What is the odd mode impedance of a transmission line?

The odd mode impedance is the impedance of one transmission line when the pair is driven differentially. In terms of the characteristic impedance in line 1, mutual impedance, and current in line 1, the odd mode impedance is:

What is the common mode impedance of a differential pair?

And the common mode signal current in the differential pair is ‘I1 + I2 = 2I1’ so that the common mode impedance of the differential pair is: Thus, the common mode impedance of the differential pair is half of the even mode impedance of one line.

What is the return path of differential impedance?

Just referring to “…the impedance” may be a bit ambiguous  Eric Bogatin 2000 Slide -10 www.BogatinEnterprises.com MYTHS Training for Signal Integrity and Interconnect Design Return Path in T Lines Current into signal line Where is the return path? For DC currents: For RF currents? When does current come out return path? TD = 1 sec