Daniel Jackson wrote: > Phase Splitters <http://softwaredefinedradiousa.pbwiki.com/Phase+Splitters>
The quadrature hybrid coupler at (a) works well if carefully designed and constructed. The phase shift is always 90 degrees but the I/Q amplitudes become unbalanced either side of the design frequency. This coupler has a number of interesting properties. Recommended reading: "Twisted-Wire Quadrature Hybrid Directional Couplers" by Reed Fisher W2CQH, QST January 1978. This article is on the CD that comes with the book "Experimental Methods in RF Design", ARRL (also recommended reading...). The transformer at (b) has nothing to do with 90 degrees. The two outputs are 180 degrees apart regardless of everything. The circuit at (c) does not shift the signals 90 degrees. The circuit at (d) is useful for generating a quadrature (I/Q) squarewave L.O. but it divides the frequency by 4. It does not work with analog signals. 73 Johan SM6LKM > > Dave > > Ok, the toroid transformer induces an electromagnetic field into the > two secondary windings. Remember now that the voltage leads the current > in an inductor by 90 degrees. > > So there is a 90 degree phase difference in the secondaries. And > these are phased opposite each other. Exactly how this way of phasing > produces two 90 degrees secondary outputs is way too difficult for me to > describe but someone here at the group might try it. > > I understand there are points in the wave cycles where the phasings > come together and then 90 degrees, and at some points 180 degrees. So I > understand that there are more than one set of angles at work in the > phasing wave cycles. But 90 degree phasings occur and I guess thats all > we need. > > Here at this link is what I have compiled about phase splitters; from > those used by various folk around the Internet. Phase Splitters > <http://softwaredefinedradiousa.pbwiki.com/Phase+Splitters> > > * There is a resistor / capacitor phase splitter at this link that > might be more feasible for a crystal set. Where we know for usre the > phasing is 90 degrees. You know the idea of a crystal set is not > unreasonable as you look at it. I am not sure how two diodes will act > here but it seems that all we need to do is produce a demodulate audio > band signal. The sound card has plenty gain for strong night time > medium wave signals. But I could be all wrong. And this circuit is > merely for fun and speculation. We'll see though. > > Now if I am incorrect on my understanding of phase splitters please > correct me so I can get the most accurate text put up on the site. > > Dan >
