JeremyGarry
Newbie
Hi everyone,
On Broadband Microstrip Antennas, pp.254, an open stub with length l and width w is coupled to the radiating edge of a rectangular patch antenna. When length l grows larger(in a certain range), its resonance frequency decreases. When the phenomenon is explained by the increment of effective resonant length, I feel it pretty easy to understand. However, the book then delivers another explanation which blows my mind. It says the decrease in the resonance frequency can also be explained in terms of an increase in the capacitance of the open-ended stub(due to increase in l). The total capacitance of the equivalent patch increases and consequently the resonance frequency decreases.
Could someone please tell me why should resonance frequency shift with patch capacitance?
The reason why I feel so lost is that every time I simulate an antenna, I fix the resonance frequency first and then apply appropriate matching networks to eliminate the reactance part (the part caused by capacitance/inductance). But that do not seem to change the center frequency I set up before matching the antenna. In other words, when I apply short stubs to match the patch antenna impedance, I definitely introduce a new capacitance part to the effective patch. But I do not suppose the matching network affect center freq. So how can the capacitance of the patch actually affect resonance freq., according to the textbook?
Thank you so much for reading. I will be so grateful if you would help me out.
Jeremy
On Broadband Microstrip Antennas, pp.254, an open stub with length l and width w is coupled to the radiating edge of a rectangular patch antenna. When length l grows larger(in a certain range), its resonance frequency decreases. When the phenomenon is explained by the increment of effective resonant length, I feel it pretty easy to understand. However, the book then delivers another explanation which blows my mind. It says the decrease in the resonance frequency can also be explained in terms of an increase in the capacitance of the open-ended stub(due to increase in l). The total capacitance of the equivalent patch increases and consequently the resonance frequency decreases.
Could someone please tell me why should resonance frequency shift with patch capacitance?
The reason why I feel so lost is that every time I simulate an antenna, I fix the resonance frequency first and then apply appropriate matching networks to eliminate the reactance part (the part caused by capacitance/inductance). But that do not seem to change the center frequency I set up before matching the antenna. In other words, when I apply short stubs to match the patch antenna impedance, I definitely introduce a new capacitance part to the effective patch. But I do not suppose the matching network affect center freq. So how can the capacitance of the patch actually affect resonance freq., according to the textbook?
Thank you so much for reading. I will be so grateful if you would help me out.
Jeremy