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gelunmak Antenna Theory Regular
Joined: 05 Jun 2009 Posts: 17 Location: Hong Kong

Posted: Fri Jun 12, 2009 10:34 am Post subject: Antenna Quality Factor (AntennaQ) 


Is the Qfactor important in antenna theory?
What's is defination & equation of AntennaQ?
Is it Q=fc/(f2f1)? [fccenter freq, f1 and f2 are cutoff freq]
What i understand is higher the Q, lower the bandwidth, and Q is defined as 2(pi) times the ratio of total energy stored to energy radiated per cycle. But i can only think of microstrip patch as a resonant cavity and apply the idea to patch antenna design. i.e. Increasing the substrate thickness > increasing the radiated energy per cycle > decreasing the Q > Increasing Bandwidth! How Q related to other antennas?
Bty, not sure why there is a term " 2 (pi) " in the defination?
Thanks 

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admin Site Admin
Joined: 03 Jan 2007 Posts: 205

Posted: Sun Jun 14, 2009 4:58 am Post subject: antenna Q 


In my mind, antenna Q only deals with bandwidth. However, equally valid is the interpretation you mentioned: the ratio of stored energy to energy radiated. Some antenna engineers think about Q from this second viewpoint; but not me.
The 2*pi factor in the definition is to make the two definitions numerically consistent. 

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