Loop Antenna Bandwidth

[BusyEng]

Hi all,

I am dealing with a small loop antenna taht is supposed to work at 2.44GHz. My measurements with VNA shows taht the current designed antenna is resonating at 2.64GHz and has a 60MHz bandwidth. Two questions:

1) How can I increase the antenna bandwidth from 60MHz to 200MHz?

2) Can I reduce the resonating frequency from 2.64GHz to 2.44GHz by increasing the loop circumference? (in my current design the loop circumference is 28mm. How much more should I add to the circumference to bring the resonating frequency down from 2.64GHz to 2.44GHz)

Thanks.

 

[E Kafeman]

1. A simple wire loop in this size results in 300 MHz BW for VSWR below 1:3 with a two components matching network.
2. There is no natural resonating frequency for a simple wire loop with length much shorter then actual wavelength.

It is very easy to make an loop antenna with circumference 0.25 lambda as required network is very simple.

Take a wire ~40mm, solder one end at center of a coaxial cable. Read at VNA while holding other end of wire against braid of coaxial cable.
Adjust wire length until 2440 MHz is rotated max to the right. See below. Resulting wire length was in my case 32 mm, solder wire and braid.


Resulting impedance.

Add a impedance correcting network:

This network was automatically calculated. Murata LQG15HS inductor.

Smith chart before and after above network was applied:


VSWR:

BW for VSWR 1:3 is about 300 MHz.

 

[BusyEng]

Could you please provide your S11 readings as well? (both before and after adding the matching circuit)

Thanks

 

[E Kafeman]

Smith charts above shows S11 readings both graphical and numerical before and after matching circuit.