IQ, Image Reject, and Single Sideband Mixers Demystified

Quadrature mixers (IQ, Image Reject, and Single Sideband) are offer powerful capabilities and are critical to modern communication and electronic warfare systems. However, they are also among the most complex RF and Microwave circuits. In this webinar, Marki Microwave will deconstruct these powerful circuits by explaining:
• How ‘quadrature’ signals lead to signal cancellation without filtering
• Common compensation techniques for optimal carrier and sideband suppression
• The best and worst ways to create quadrature signals for any application

Q & A

Is it better to use a square wave to drive an IQ mixer?

We don’t expect much improvement from a square wave. First an M1/MM1 style mixer usually doesn’t show much improvement with a square wave, and MMIQ mixers are built with these. This is probably because the baluns filter the higher frequency harmonics that create the square wave. Second, the quad hybrid on the LO side would further filter the harmonics above what the LO baluns do, further reducing the square wave effect. If, however, you built an IQ mixer with a super broadband quad hybrid and a T3 mixer, then you would see improvement with a square wave.

Is it necessary to use a double balanced mixer or can you use a single balanced mixer in an IQ mixer?

You can use any mixer you like, but the mixer core determines the isolations, linearity, and spur suppressions of the IQ mixer structure. Generally a double balanced mixer is preferred because it can offer excellent isolations and spur suppressions while also providing a DC connection on the I and Q ports, which is required for tuning the isolations.

Are your mixers built on GaN or GaAs substrates? Have they ever been used in space applications?

Yes, we offer space qualified MMIC mixer products, including MMIQ mixers. See our space products page here.

Does LO level impact the conversion loss?

YES! Underdriving the LO can cause significant dips in conversion loss performance and band narrowing. LO drive requirements are dependent on the frequency plan including the frequency span of the LO