Wireless communication and radar systems are under continuous pressure to reduce size, weight, and power while increasing dynamic range and bandwidth. The quest for higher performance in a smaller package motivates the use of IQ mixers: mixers that can simultaneously mix ‘in-phase’ and ‘quadrature’ components (sometimes called complex mixers).
System designers use IQ mixers to eliminate or relax the requirements for filters, which are typically the largest and most expensive components in RF & microwave system designs. IQ mixers use phase manipulation to suppress signals instead of bulky, expensive filters.
The goal of this application note is to introduce IQ, single sideband (SSB), and image reject (IR) mixers in both theory and practice. We will discuss basic applications, the concepts behind them, and practical considerations in their selection and use. While we will focus on passive diode mixers (of the type Marki sells), the concepts are generally applicable to all types of IQ mixers and modulators.