Is this mixer a double balanced mixer?

By using bipolar switches, the "single balanced" CMOS mixer behaves like double balanced, suppressing RF and LO at IF output.

To get a real double-balanced mixer you need at least four switches (diodes, transistors all kind, tubes, real switches, etc.).
A single-balanced mixer have some isolation between two of the three ports, isolation which depends by the input return loss at the LO and RF frequencies.
A double-balanced mixer gives isolation between all three ports, and the isolation doesn't depends much by the input return loss.

Both simulations I gave are double balanced with 4 switches, does it not? https://www.edaboard.com/threads/is-this-mixer-a-double-balanced-mixer.412769/post-1782615

#22 was referring to #21

First simulation in post #9 is a CMOS switch mixer similar to post #1, which should be categorized as single balanced according to vfone. In contrast to a single balanced mixer, it however isolates both RF and LO from IF. CMOS switch is often considered as third mixer type in literature because it behaves more closely to an ideal frequency mixer, as stated in post #21.

vfone said:

The answer to your first question is: this is a single-balanced mixer, not a double balanced mixer.
A single-balanced mixer is a step forward from a single-device mixer, which use a single diode or a single transistor.
A single-balanced mixer provides isolation between LO and RF ports, when a single-device mixer cannot provide this isolation.
A single-balanced mixer requires at least two switching components. Two diodes or two transistors. In your case, two switches inside of the 4051 chip.

Click to expand...

Au contraire, the Gilbert cell is a Double-Balanced (DB) with 4 modulating pairs of transistors—two pairs to modulate the tail currents of two top diff amps to modulate the polarity and amplitude. Using single-ended input is still Double-Balanced (DB) but it may or may not degrade polarity gain and some unsuppressed carrier. asymmetric sidebands. It depends on your tolerance specs. The common mode(CM) signal using 1 input to a diff. amp. just relies on the CM rejection ratio (CMRR) from matching inside the IC.

FvM said:

First simulation in post #9 is a CMOS switch mixer similar to post #1, which should be categorized as single balanced according to vfone. In contrast to a single balanced mixer, it however isolates both RF and LO from IF. CMOS switch is often considered as third mixer type in literature because it behaves more closely to an ideal frequency mixer, as stated in post #21.

Click to expand...

The IF input uses a single switch to control an inverter = SPDT which controls 2 switches similar to the RF input.

Why does this appear single balanced? @vfone