Abstract: A mixer converts input power at high-frequency RF into output power at a different and much lower frequency IF, with the assistance of another high-frequency oscillator (LO). Typically, a very low IF frequency requires an LO that approximates the RF frequency. However, a subharmonic mixer facilitates low IF with LO frequencies significantly lower than the RF frequency. This balanced odd-subharmonic mixer consists primarily of a four-port BALUN and a pair of diodes. The diodes terminate two ports of the BALUN connecting in series and in anti-parallel to the remaining external BALUN ports. The external BALUN ports constitute the RF and the LO high-frequency mixer ports. The mixer's lower-frequency IF port also connects to the diodes, comprising a separate channel that is co-linear with one BALUN external port, and coupling capacitively to the other. All three mixer ports meet at a mixing chamber (part of the BALUN) where the diodes are located.