75 ohm bias tee

Dear everyone,

I want to design bias tee. But I don't have solutions.

The spec.

1. Frequency Range : 0.95GHz ~ 2.125GHz
2. Insertion Loss : 0.5 dB
3. VSWR : 1.3
4. Input Connector : F(female, 75 ohm)
5. Output Connector : SMA(female, 50 ohm)
6. DC : 30V, 0.8A

I try to design lumped element of atceramic and coilcraft by awr microwave office & ansoft desinger.

But I only have result of I.L. 2dB, R.L. 10dB.

Please advise to me.

Thank you.

Hi HOHOH,

For a wide band inpedance match you need a Minimum Loss Pad, which has an acceptable return loss on both (50 and 75 ohm) ports. These devices has a typical insertion loss of 5.7 dB. There are Minicircuits coaxial devices (BMP5075 for example), but they have a smd model too : ALMP5075 with characteristics up to 3GHz. But you also can prepare a simple Gamma circuit with 2 resistors

Look at the link below:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/972

For a wide band bias tee, look to the following reference:

http://www.qsl.net/n9zia/wireless/ps/bias_tee.ps
../imgqa/eboard/Antenna/rf-m2qriqwzbn5.jpg

Combining these 2 circuits, you will have good results.
For your bandwidth (I supose the 75 ohm section is for the SAT IF band, and you want to power your 75 ohm device, and measure the characteristics with a 50 ohm analyser), you can use printed inductors instead of wire wounded.

regards,

Al