One confused question about antenna (please help)

[pfijk]

Dear all


characteristic for antennas

1. The quality factor (Q) is nagtive proportional to bandwidth (BW) .

The high loss leads to low quality factor , and it gets wide bandwidth.

2. But it views on return loss , the lower return loss can also get wide bandwidth.

What is the relation between the 1. and 2. ?

high loss ? lower return loss ?

I am confused in this question :|

Thanks if any body reply this topic .

BR

 

[mshareef]

use your Analysis with the following equations:

Bandwidth = {F (upper) - F (lower)}/ F (resonant) directly proportional to 1/Q

Where Q = 1/R * {Sqrt (L/C}

Where Q = Quality factor
R = Loss Component

 

[pfijk]

use your Analysis with the following equations:

Bandwidth = {F (upper) - F (lower)}/ F (resonant) directly proportional to 1/Q

Where Q = 1/R * {Sqrt (L/C}

Where Q = Quality factor
R = Loss Component

thanks for your reply .

The R meets my discription 1. , but

what is the relation between it and return loss ?

I think the return loss and R are different.

 

[sweetughirish]

Actually me and my friend recently had this problem too....I do not know how far this is true but this is what we reasoned out.....

Quality factor=energy stored/enery lost

So, the the higher the Q factor the lower the bandwidth.....

Meanwhile return loss is measure of s11 which only says the amount of E reflected/E transmitted.

Lower return loss(meaning higher S11 in terms of negative) will also get you higher bandwidth. Since the mismatch is reduced,reducing S11 will not increase the bandwidth because more energy are reflected back rather then stored or lost.

 

[pfijk]

Thanks for sweetughirish's response

Do anyone have some comments for this question ?