SUBHARMONIC MIXERS SIMPLIFY DIGITAL-MODULATION SYSTEMS

DIRECT modulation at microwave and millimeter-wave frequencies promise s the advantages of compact size, low cost, relatively simple system d esign, and high achievable data rates. In some cases, subharmonic in-p hase/quadrature (I/Q) modulators are being used in order to overcome t he high carrier leakage that is associated with conventional fundament al modulators at microwave and millimeter-wave bands. When using subha rmonic mixers, however, caution must be taken to minimize the second h armonic associated with local-oscillator (LO)-source feedthrough from the LO to the RF output.