Mixers that are used to down-convert from a received radio frequency signal at high frequency to an intermediate signal at a lower frequency, at which filtering and amplification are more convenient, and to perform the reverse operation for transmission. Microwave mixers based on high-frequency diodes, generally connected in-groups of four to form a "quad", and are widely used in microwave and cellular communications. These microwave mixers are available in different bands like double balanced communication band and broadband, triple balanced mixers for wide applications.