Contents
Does impedance increase with length?
Distance relays respond to a ratio of voltage and current at the relay location, this ratio is in the form of impedance, as the impedance of a transmission line is proportional to its length.
How do you determine the physical length of a transmission line?
A signal’s wavelength is the physical distance it will propagate in the timespan of one period. Wavelength is calculated by the formula λ=v/f, where “λ” is the wavelength, “v” is the propagation velocity, and “f” is the signal frequency.
When should a transmission line be treated?
-long cable, you must treat the cable as a transmission line for signals at frequencies greater than 24 MHz. The following formula illustrates this point: where tPD equals 4.15 nsec, which is the time it takes for the electromagnetic wave to make a one-way trip.
Why are there long and short lines?
The criterion for this division is fluid and depends on the current situation on the chart. The so called short line is the one where the market volatility is very low (small price range). Similarly, the long line will be the one of high volatility (large price range).
When does the impedance of a track begin to matter?
General rule of thumb: the impedance of the track begins to matter when its length is greater than 1/10th the wavelength.
Is the characteristic impedance of a transmission line independent?
Although an infinite line is assumed, since all quantities are per unit length, the characteristic impedance is independent of the length of the transmission line.
What do you need to know about controlled impedance?
The manufacturer gives you the stackup that mentions the trace widths on each layer, the number of layers, the thickness of each dielectric in the stackup, trace thickness, and PCB material.
How is the impedance of a circuit related to the dimensions?
Stick to the following relationships to know how impedance depends on dimensions: Impedance is inversely proportional to trace width and trace thickness. Impedance is proportional to the laminate height and it is inversely proportional to the square root of laminate’s dielectric constant (Er).