Transcription of Impedance Matching and Smith Charts - Fermilab
{{id}} {{{paragraph}}}
Example: barber
Impedance Matching and Smith Charts - Fermilab
Impedance Matching and Smith ChartsJohn Staples, LBNL Impedance of a Coaxial Transmission LineA pulse generator with an internalimpedance of R launches a pulsedown an infinitely long coaxialtransmission though the transmission line itself has no ohmic resistance, a definite current I is measured passing into the line by during the period of the pulse with voltage Impedance of the coaxial line Z0 is defined by Z0 = V / Impedance of a coaxial transmission line is determined by the ratio of the electric field E between the outer and inner conductor, and the induced magneticinduction H by the current in the surge Impedance is, where D is the diameter of the outer conductor, and d is the diameter of the innerconductor. For 50 ohm air-dielectric, D/d = 0 0ln Dd =60ln Dd Z0= 0 0=377ohmsis the Impedance of free space. Velocity of Propagation in a Coaxial Transmission LineTypically, a coaxial cable will have a dielectric with relative dielectric constant erbetween the inner and outer conductor, where er = 1 for vacuum, and er = a typical polyethylene-insulated characteristic Impedance of a coaxial cable with a dielectric is thenand the propagation velocity of a wave is,where c is the speed of lightIn free space, the wavelength of a wave with frequency f isFor a polyethylene-insulated coaxial cable, the propagation velocity isroughly 2/3 the speed of r60ln Dd vp=c r coax=1 rcf= free space r Reflection from End of a Shorted Transmi
The voltage reflection coefficient is: , where Z L is the load impedance and Z 0 is the impedance of the transmission line. If Z L = Z 0 ... (microwave) domain, it is difficult to probe the voltages and currents in various parts of a circuit, but easier to measure the voltages at given reference planes in a circuit. For a linear circuit, ...
Tags:
Information
Domain:
Source:
Link to this page:
Please notify us if you found a problem with this document: