The present invention relates generally to communications, and more
specifically to a method and apparatus for generating local oscillator
signals used for up- and down-conversion of RF (radio frequency) signals.
A major problem in the design of modulators and demodulators, if the
leakage of local oscillator (LO) signals into the received signal path.
The invention presents a number of highly integratable circuits which
resolve the LO leakage problem, using regenerative divider circuits
acting on oscillator signals which are running at a multiple or fraction
of the frequency of the desired LO signal, to generate in-phase (I) and
quadrature (Q) mixing signals. Embodiments of these circuits also use
harmonic subtraction and polyphase mixers, as well as virtual local
oscillator TM (VLO) mixing signals. VLO mixing signals are signal pairs
which emulate local oscillator signals by means of complementary
mono-tonal and multi-tonal mixing signals.