I'm trying to design a microstrip patch antenna @ 2.6 GHz. The result I got is good but the antenna is very selective and I haven't been able to increase the BW.
Currently, the BW is 40 MHz and I need it to be 100 MHz (S11 = -10 dB @ 2.55 GHz //**// S11 = -10 dB @ 2.65 GHz). I've tried all the 7 optimization algorithms in CST studio but none of them was able to increase the BW. I've tried everything: modifying the dimensions of the patches, the insets, and the Tx lines, changing the polarization, adding tabs, adding slots into the patches, adding a small gap between the patch and the Tx line, placing the ground plane over the patches and modifying the air gap between them, and reducing the ground plane; but none of these methods have increased the BW in more than 5 MHz.
I can't increase the thickness of the substrate because I am already considering the thickest one I have.
This is meant to be a MIMO 2x2 photonic antenna and each patch is fed by a photodiode, the photodiodes receive their signals from an optical splitter, one patch should be able to transmit any of the 2 signals regardless of the one it gets. So there are 2 channels with central frequencies @2.575 GHz and @2.625 GHz, the BW for each channel should be 20 MHz with a guard-band of 5 MHz.
Here are the parameters of the PCB:
- PCB width: 190 𝑚𝑚
- PCB length: 70 𝑚𝑚
- Distance between the antennas: 71.5 𝑚𝑚
- Antenna’s width: 42.5 𝑚𝑚
- Antenna’s length: 29.3 𝑚𝑚
- Insets’ width: 4 𝑚𝑚
- Insets’ length: 7.1 𝑚𝑚
- Transmission line width: 3.37 𝑚𝑚
- Transmission line length: 20.35 𝑚𝑚
- Copper’s thickness: 0.035 𝑚𝑚
- Substrate’s thickness: 1.524 𝑚𝑚
- Dielectric constant (𝜀𝑟): 3.67
- Dissipation factor (tan𝛿): 0.0021
I would really appreciate it if you could tell me the adjustments I need to do in order to achieve a BW of 100 MHz.
I attached the schematic of the PCB and the S parameters I got.
Thank you very much in advance for your help!