picharro
Newbie level 3
Hello,
I am designing RFID tags on printed electronics (868 MHz Band) . I designed some dipole antennas and simulated. As an example my input impedance of my dipole is 73+11j Ohms. The response of my antenna seems to be ok, about -15 dB at the frequency of interest with a bandwidth of 180 MHz. I used 50 Ohm reference impedance for port 1 defined as balanced one (The port is composed by Pin 1 as positive and Pin 2 as negative). I use ADS 2011 as simulator.
My problems appears when I designed the matching network. I need an input impedance value that must be exactly the complex conjugate impedance of the RFID chip for the maximum transfer of power between the antenna and the chip. The impedance of the chip is 30-600j Ohms, so my antenna impedance should be 30+j600 Ohms. There are different strategies to do the matching network, as T-matching. I add the matching network to my antenna and simulated again to obtain the desired input impedance. The problem is that the response of my antenna changes dramatically. The resonant frequency stays at 868 MHz, but the magnitude of my response fall until -0.3 dB.
My question are:
-The antenna response must to be unchanged after adding the matching network?
-By definition, the mismatching must to be greater because my input impedance is far away from the 50 Ohms of my port. So, should I use as reference impedance of my port the value that is my objective (30+j600Ohms) and check again the antenna response?
I hope someone can help me.
Thank you in advanced.
I am designing RFID tags on printed electronics (868 MHz Band) . I designed some dipole antennas and simulated. As an example my input impedance of my dipole is 73+11j Ohms. The response of my antenna seems to be ok, about -15 dB at the frequency of interest with a bandwidth of 180 MHz. I used 50 Ohm reference impedance for port 1 defined as balanced one (The port is composed by Pin 1 as positive and Pin 2 as negative). I use ADS 2011 as simulator.
My problems appears when I designed the matching network. I need an input impedance value that must be exactly the complex conjugate impedance of the RFID chip for the maximum transfer of power between the antenna and the chip. The impedance of the chip is 30-600j Ohms, so my antenna impedance should be 30+j600 Ohms. There are different strategies to do the matching network, as T-matching. I add the matching network to my antenna and simulated again to obtain the desired input impedance. The problem is that the response of my antenna changes dramatically. The resonant frequency stays at 868 MHz, but the magnitude of my response fall until -0.3 dB.
My question are:
-The antenna response must to be unchanged after adding the matching network?
-By definition, the mismatching must to be greater because my input impedance is far away from the 50 Ohms of my port. So, should I use as reference impedance of my port the value that is my objective (30+j600Ohms) and check again the antenna response?
I hope someone can help me.
Thank you in advanced.