rf1008
Full Member level 2
Hi all.
I've been measuring my dipole antenna impedance at UHF band recently,i used single-ended two-port VNA and calculated the final differential impedance by some formula directly from S11/S22/S12/S21. Attached(the coaxial one) is my differential probe made by coaxial cable.
Before measure the dipole,0603 100R resister is measured to verify and confirm the whole measurement method including the formula.And i calculated and got the impedance of 102.7+j2.5 Ohm,I believe it is good enough! Then i changed 100R resistor to my DUT,PCB dipole antenna.
BUT, the final calculated impedance is -4.6+j144.2 Ohm. The Imag part is very similar to my simulation value,the Real part is smaller to my simulation value which is about 19 Ohm,Also the Real part is negative! There must be sth.wrong!
I can not access anechoic chamber now and do the measurement in lab where has some reflections nearby. The curve on the VNA screen jitters a little when move the dipole antenna WASD. Is the anechoic chamber very important?or anything else wrong?
I need your help,thanks a lot!!
I've been measuring my dipole antenna impedance at UHF band recently,i used single-ended two-port VNA and calculated the final differential impedance by some formula directly from S11/S22/S12/S21. Attached(the coaxial one) is my differential probe made by coaxial cable.
Before measure the dipole,0603 100R resister is measured to verify and confirm the whole measurement method including the formula.And i calculated and got the impedance of 102.7+j2.5 Ohm,I believe it is good enough! Then i changed 100R resistor to my DUT,PCB dipole antenna.
BUT, the final calculated impedance is -4.6+j144.2 Ohm. The Imag part is very similar to my simulation value,the Real part is smaller to my simulation value which is about 19 Ohm,Also the Real part is negative! There must be sth.wrong!
I can not access anechoic chamber now and do the measurement in lab where has some reflections nearby. The curve on the VNA screen jitters a little when move the dipole antenna WASD. Is the anechoic chamber very important?or anything else wrong?
I need your help,thanks a lot!!