RFFC5071A| RF Balun for wide frequency band usage

RF Solutions RF All Other (switches, controls, attenuators, ..)
1

Hi Qorvo team

We are having a doubt, regarding the selection of the BALUN impedance ratio for the Mixer RFFC5071A.

From the datasheet, we could understand that for low frequencies (<2.7GHz), Mixer output BALUN of impedance ratio of 1:4 (200 ohm differential) is best suited. While for higher frequencies (>4.5GHz), impedance ratio of 1:1 (50 ohm differential) is beneficial.

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We want to know what the BALUN impedance ratio for wideband applications should be, such as 500MHz - 6/8GHz, where both the low frequencies and the high frequencies are involved.

Should a BALUN with 1:2 impedance ratio be fine in order to strike a balance between voltage gain and parasitic capacitance?

Also, can we use the Mixer Input side BALUN as one having 1:2 impedance ratio (100ohm differential)?

We could not find any reference circuit of this Mixer for such a wide band of frequencies that could have helped us in BALUN selection for the same.

2

For very wideband applications up to 6GHz I’d recommend on the mixer output a 1:1 balun. Ideally this should have a DC port, as the 3V supply needs to be routed through the balun to the mixer output pins. Otherwise wideband inductors would need to be used for the supply. Using a 1:1 balun on the output trades conversion gain for gain flatness. A 4:1 balun on the output would give good gain at low frequency, but the frequency roll off would be severe.
On the mixer input you can use either 1:1 or 2:1 balun, since the mixer input impedance is around 75R.
More detail in these app notes.
https://www.qorvo.com/products/d/da000737
https://www.qorvo.com/products/d/da000739