I have a ENA 5071C. I use AppCAD to calculate 50 ohms microstrip line. The problem is I want to make sure that a microstrip line has 50 ohms impedance.

The way I did is I use 50 ohms coaxial cable connect to Port 1, and solder the 50 ohms coaxial signal wire to the microstrip line. Nothing connects to the microstrip line. Please see the attached picture.I know that I can check 50 Ohms from a smith chart in a NA. The smitch chart line at 1900 MHz is totally far away from 50 ohms line. Could anyone guide me how to measure a microstrip line no other components connecting to it.

This is my microstrip design to match 50 ohms in 1900 MHz. It is in attached picture. I appreciate every helps. Thank you in advance.

The way I did is I use 50 ohms coaxial cable connect to Port 1, and solder the 50 ohms coaxial signal wire to the microstrip line. Nothing connects to the microstrip line. Please see the attached picture.I know that I can check 50 Ohms from a smith chart in a NA. The smitch chart line at 1900 MHz is totally far away from 50 ohms line. Could anyone guide me how to measure a microstrip line no other components connecting to it.

This is my microstrip design to match 50 ohms in 1900 MHz. It is in attached picture. I appreciate every helps. Thank you in advance.

But, fyi, you cannot measure the characteristics of an unterminated line. You must at least terminate the line in a known impedance, or all you get is the response of an open stub.

"I looked at your posting but I have no idea what the picture is supposed to be. I can't see the launch or the termination of the microstrip line; so you are going to have to be a lot more clear about your situation.

But, fyi, you cannot measure the characteristics of an unterminated line. You must at least terminate the line in a known impedance, or all you get is the response of an open stub."

Sorry that if my explanation is not clear.

From my picture, the black 50 ohms coaxial cable is the launch point. It has U.FL connector at the end to connect to the port 2 of NA. But I have no idea how to measure the impedance of the microstrip line. You said that I have to terminate a line by a known impedance. What can I use? Can I use a 50 ohms resistor? I'm sorry if my question looks stupid but I'm really new to this kind of measurement. I would highly appreciate your advice. I have RF background but it is like I dont know how to apply it.

I do appreciate every help!!!

The second best choise is to terminate the line with a 50 ohm impedance, but I recommend using two 100-ohm resistors as they have better compensation for parasitic L and C.

In fact, if you do this, you need to remove the effects of the coax. To do this, start a cal at the SMA or VNA cable, then add you coax and automatic port extend, then solder on the 2 100-ohm resistors and measure the return loss. This is the limit of your measurements, so look at the S11 and see what it is.

Then, take off the 2 100-ohm resistors, add the microstrip line, add the resistors to the end of the line, and now you have another measuarement. The difference between the two measurements is due to your line. If your line is 50 ohms, then you will have no difference, but only if the 2 100-ohm resistors have no parasitic L or C.

1. My NA model is E5071C, and I have Agilent 85032F Type N Calibration kit which have only Type N Male and Female. There is no problem for the first port which has Type N male to Type N male cable. Problem is on port 2 the cable is Type N male to SMA male. When I calibrate the NA, I have to use a SMA female to Type N female adapter to connect to a calibration kit. So I think my calibration is not 100% correct. Also, when I test, I have to use an adapter to convert from SMA male to UMC jack, and use UMC plug to cable connecting to an adapter. Could you please suggest how to correctly calibrate?

2. FYI "In fact, if you do this, you need to remove the effects of the coax. To do this, start a cal at the SMA or VNA cable, then add you coax and automatic port extend, then solder on the 2 100-ohm resistors and measure the return loss." I have a 50 ohms coaxial cable which connects to NA cable. I wonder that how can I solder the two parallel 100 ohms resistors to a coaxial cable? How can I measure it? Could you please explain more in details? The cable has only signal wire, plastic insulator, and surrounding ground. Sorry if it looks like a stupid question, but I have no idea how to measure the return loss of two 100 ohms resistors.

3. "A good choice is to measure the line as a 2-port, connecting to each end." From your recommendations, does it mean that I plug the port 1 cable at the launching point and port 2 cable at the terminated point? And see S21 from a smith chart? Do I understand correctly? Anyway I have to calibrate the two port cable with extended 50 ohms coaxial cable following your suggestions from my question 1.

All in all, I do appreciate your help very much. Thank you very much.

I am a junior engineer, and this is my first RF job. So please do understand me.

Bill

But, as a start, get and read the application note 1287-9; 1364-1; and you better read this too: http://cp.literature.agilent.com/litweb ... -7917E.pdf

I would study what you recommend. If I have other aspects that I don't understand, I would ask for your help to clarify. Thank you very much. Have a great weekend!!!

Bill