I'm wondering what the insertion of notch filters into the IQ channels will do to the quadrature relationship of those channels.
While I'm sure the insertion of the notch filters will suppress certain narrowband frequencies effectively I think it would be most difficult to maintain a quadrature relationship between the notches at a single frequency much less at a band of frequencies. Even if the notches are in quadrature it is even more unclear how they would interact off resonance. Some serious modeling is in order to determine what the overall effect would be, but I have a feeling the sideband suppression may be seriously compromised. Am I missing something? 73 de Ray WB6TPU -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Monday, April 03, 2006 5:16 PM To: [email protected] Cc: [EMAIL PROTECTED] Subject: [soft_radio] Notch Filters? Man, this is an active email group, but thats good, I got lots to read and very interesting, Ken brought up the question of whether you can notch the I and Q signals in the audio chain of a receiver? I have had receivers with i.f. notch before and as far as I understand the two phase shifted signals you should be able to do this. The two signals although phased 90 degrees from each other still are sine wave components of frequency and amplitude. Being generated by a transmitter somewheres on the airwaves. I see no reason why a notch filter would not work in the audio chain of the two port signals I and Q. The reasoning behind this is that the I and Q signals are in the audio pass band and are sinewave components having various frequencies. A CW tone will appear somewheres in the pass band when a CW signal is present and it will be located at a certain frequency and so a notch filter in the audio pass band should be able to notch it out if it is undesired in the pass band. At least thats how I see it? Of course such a notch would have to be very narrow in order to work in the desired audio pass band. If too wide it would take out too much band width. So Op Amps would accomplish this. I am not a software desinger, just a radio tech thats all. I am looking at the circuits. I can't even imagine the software, I look at learning Java and Python and well its scary. I have tried my hand at artificial intellegence mark up language though (aiml), I have a few of those robots like Alice Bot. Now this is my theory of the the analog circuits and well it will take some experimenting to see if the audio notch filter idea will work. As far as I understand it, it should work. Dan Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/soft_radio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
