Home |
Search |
Today's Posts |
#2
![]() |
|||
|
|||
![]()
Bob Bob wrote:
If I then take a stripline cct terminated at one end with a 50r resistor and a detect diode at the other and is a half wave long, what is the current/voltage distribution in this configuration. Since the ends of the 1/2WL conductor are open circuits, standing waves on the conductor are the result. The standing wave(s) consists of the superposition of the forward wave(s) and the reflected wave(s). This is exactly why the forward and reflected waves cannot be ignored (as some gurus advise) if understanding is the goal. For a 1/2WL conductor, the standing wave has a cosine envelope with a phase near zero all along the line because the forward and reflected phasors are rotating in opposite directions. The current is obviously zero at the ends and maximum in the center. The resistor termination at one end dissipates either the forward wave or reflected wave depending upon which end it is located. The dipole at the other end rectifies the other wave. If you are measuring the forward power, the forward wave is rectified by the diode and the reflected wave is dissipated/attenuated by the resistor. I have an old Heathkit SWR meter that operates the same way. There's two pickup conductors, one for forward power and one for reflected power. In short, the resistor dissipates one of the component traveling waves thus preventing reflections while the diode rectifies the other traveling wave, thus providing a voltage proportional to that other traveling wave. Which wave is dissipated and which wave is rectified depends upon which end of the conductor the resistor and diode are located. -- 73, Cecil http://www.qsl.net/w5dxp |
Thread Tools | Search this Thread |
Display Modes | |
|
|
![]() |
||||
Thread | Forum | |||
[question] current/voltage amplitude inducted in antenna | Antenna |