CONNECTOR ADAPTERS

From that same page:-

"Okay, what about as a power combiner? Consider a signal input at port

1. In this case, it splits equally between port 1 and the resistor R with none appearing at port 3. The resistor thus serves the important function of decoupling ports 2 and 3. Note that for a signal input at either port 2 or 3, half the power is dissipated in the resistor and half is delivered to port 1. Why is port 2 isolated from port 3 and vice-versa? Consider that the signal splits when it enters port 2. Part of it goes clockwise through the resistor and part goes counterclockwise through the upper arm, then splits at the input port, then continues counterclockwise through the lower arm toward port 3. The recombining signals at port 3 end up equal in amplitude (half power or the CW signal is lost in resistor R1, while half of the CCW signal is output port 1. And they are 180 degrees out of phase due to the half-wavelength that the CCW signal travels that the CW signal doesn't. The two signal voltages subtract to zero at port 3 and the signal disappears, at least under ideal circumstances. In real couplers, there is a finite phase through the resistor that will limit the isolation of the output ports."

I can see that if the signals at ports A and B are exactly in phase then the effect of the resistor will be cancelled out but surely if they are not in phase then the resistor must have some effect.

You are at least somewhat correct if you are talking about putting in a signal into port A and only port A. Im not sure just how much would be dissipated in the resistor in this case. I dont think its half. I think the output would be about 70% of the input in this case, this is just off the top of my head. Under the ideal conditions the powercombinner is suppose to operate the would be no power dissipated in the resistor. As a matter of fact under ideal conditions where the power and phase into A and B ports are equal the resistor would not even be needed.

Jimmie

I don't have an instant answer for that one. I wanna build a model of the combiner using LT-SPICE.

Meanwhile, see: "Understanding Power Splitters"

"The power combiner will exhibit an insertion loss that varies depending upon the phase and amplitude relationship of the signals being combined. For example, in a 2 way 0° power splitter/combiner, Fig. 1 if the two input signals are equal in amplitude and are in-phase then the insertion loss is zero. However, if the signals are 180° out-of-phase the insertion loss is infinite. And, if the two signals are at different frequencies, the insertion loss will equal the theoretical insertion loss shown above."

I'm not sure how to interpet that in terms of using 2 antennas on a single access point. If the antennas were slightly different distances from the client radio, and concidentally 180 degrees out of phase, (same amplitude is assumed), they will cancel in the combiner. If they're exactly the same distance, then they will add in the combiner. If only one antenna hears the signal, it looks like you're right (and I'm wrong again), as the loss should be 3dB. I'll do some more reading tomorrow...

I later thought about the phase problems you could have using two back to back AMOS/Franklin antennas a a WiFi antenna. Then I thought about the multipath canceling circuits in the WRT54 routers where it will automatically switch antennas to find the best signal. While I see this still as a problem in an environment where multi users a trying to connect to an AP perhaps it may be interesting if not useful to try in a home environment where there may be only one user.

Jimmie

I guess the easiest way to get an omni pattern would be to remove the reflector.

instead of trying to combine two antennas.

Jimmie