Transformer T11T Output Impedance
Alfredo Mendiola Loyola
Dear All: Does the Transformer T1:1T has an output impedance of 50 ohm through all the transformer bandwidth? Does the transformer output impedance change on high frequencies? Bandwidth: 0.08 to 200 Mhz Branch. Mini Circuits Regards Alfredo Mendiola Loyola Lima, Peru


K5ESS
Well I’ll take a shot at answering this and welcome any comments/corrections to my reply. The T11T is a transformer with a onetoone turns ratio, so within limits its output impedance should be equal to that of the source its connected to. IF it were a perfect transformer which it isn’t. The Input Return Loss gives a measure of how imperfect it is. Let’s take the Return Loss figure for 80 Mhz. and call it 10 dB. So, if you connect the T11T to a device with a 50 ohm source impedance the output impedance of the T11T at 80 MHz. will be somewhere between purely resistive impedances of 96.2 and 26 ohms. To see all the possible impedances presented for the 10 dB return loss you can draw a circle on a Smith Chart centered on 50 ohms normalized to one with a radius of 1.92. See attached PDF. Mike K5ESS
From: PHSNA@... [mailto:PHSNA@...]
Sent: Sunday, December 27, 2015 3:18 PM To: PHSNA@... Subject: [PHSNA] Transformer T11T Output Impedance
Dear All:
Does the Transformer T1:1T has an output impedance of 50 ohm through all the transformer bandwidth? Does the transformer output impedance change on high frequencies?
Bandwidth: 0.08 to 200 Mhz Branch. Mini Circuits
Regards Alfredo Mendiola Loyola Lima, Peru


Alfredo Mendiola Loyola
I understand that at 80 Mhz, I will not get an output impedance of 50 Ohm at the output of the T11T Transformer.
How Can I know the exact transformer output impedance at 80 mhz with a source with 50 ohm of output impedance. How can I transform the 10db of return loss to impedances? Thank you for the information. Regards. Alfredo Mendiola Loyola


K5ESS
Alfredo, Well I don’t offhand know of any way other than measuring it. The T11T spec sheet gives the magnitude of the Return Loss but not the phase so the actual output impedance of the transformer at 80 MHz could lie at any point on the circle drawn on the attached Smith Chart.
Anyone out there want to chime in on this?
Mike K5ESS
From: PHSNA@... [mailto:PHSNA@...]
Sent: Monday, December 28, 2015 11:10 AM To: PHSNA@... Subject: RE: [PHSNA] Transformer T11T Output Impedance
I understand that at 80 Mhz, I will not get an output impedance of 50 Ohm at the output of the T11T Transformer.
How Can I know the exact transformer output impedance at 80 mhz with a source with 50 ohm of output impedance.
How can I transform the 10db of return loss to impedances?
Thank you for the information.
Regards. Alfredo Mendiola Loyola


vasilyivanenko@...
Please provide a link to the schematic your referring to  thanks V


Alfredo Mendiola Loyola


drmail377
* Alfredo Mendiola Loyola,
You asked: "How can I transform the 10db of return loss to impedances?" You can easily calculate the minimum and maximum real (normalized) impedance limits for a given Zo and returnloss. (There are many references on the Web.) Here's one online calculator that may help as well as providing the equations: http://chemandy.com/calculators/returnlossandmismatchcalculator.htm The nice thing about the Smithchart is that by plotting a circle normalized to Zo you can easily see how the real and imaginary parts change. Ofcourse you could also calculate the circle shown on the Smithchart in a spreadsheet. Just be careful to handle the signs for the nonzero imaginary variables properly. Another (more rigorous method) is to plot and/or extract the complex (real and imaginary) data provided in the manufacturer's SParameter data for the transformer. But this is beyond the scope of my post, and I'm not sure if MiniCircuits provides this data for the transformer inquestion. * Mike, K5ESS What did you use to plot the nice Smithchart circle? Best 73's, David WB4ONA


K5ESS
David, Well I cheated. I pasted the Smith Chart .jpg image into Microsoft Visio, drew a line from R=0.52 to R=1.92 to determine the circle diameter needed. Drew the circle, centered it on the line and deleted the line. Not very elegant but OK for a quick response. Best 73’s and have a great 2016 Mike K5ESS
From: PHSNA@... [mailto:PHSNA@...]
Sent: Saturday, January 02, 2016 9:47 AM To: PHSNA@... Subject: [PHSNA] Re: Transformer T11T Output Impedance
* Alfredo Mendiola Loyola,

