Abstract: This patent describes a method and system which overcomes the LO-leakage problem during modulation and demodulation, common to direct conversion and similar RF transmitters and receivers. This problem is solved using a virtual local oscillator (VLO™) signal which emulates mixing with a local oscillators (LO) signal. The VLO signal is constructed using complementary mixing signals that suppress mixing power in the bandwidth of the input signal, and within the bandwidth of the output frequency. Specifically, mixing is done in two or more stages, using time-varying mixing signals ?1 and ?2 which satisfy the following criteria: ?1*?2 having significant power at the frequency of the LO being emulated, one of ?1 and ?2 having minimal power around the frequency of the output signal y(t), and the other of ?1 and ?2 having minimal power around the center frequency, fRF, of the input signal x(t).

Abstract: This patent describes a method and system which overcomes the LO-leakage problem of direct conversion and similar RF transmitters and receivers. To solve this problem a virtual LO™ signal is generated which emulates mixing with a local oscillator (LO) signal. However, the virtual local oscillator (VLO) signal is constructed using signals that do not contain a significant amount of power (or no power at all) at the wanted output RF frequency, so there is no LO component to leak to the output. The invention also does not require sophisticated filters or large capacitors as other designs in the art, so it is fully integratable.

Abstract: This patent describes a method and system which overcomes the LO-leakage problem of direct conversion and similar RF transmitters. To solve this problem a virtual LO™ signal is generated within the baseband which is tuned to the incoming RF signal. The virtual local oscillator (VLO) signal is constructed using signals that do not contain a significant amount of power (or no power at all) at the wanted output RF frequency. Any errors is generating the virtual LO signal are minimized using a closed loop correction scheme.

Abstract: Valve operator having a weighted powering assembly that is substantially supported and balanced on a generally upright elongated key that drivingly engages a rotatable valve nut.

Abstract: Valve operator having a weighted powering assembly that is substantially supported and balanced on a generally upright elongated key that drivingly engages a rotatable valve nut.

Abstract: This patent describes a method and system which overcomes the LO-leakage problem during modulation and demodulation, common to direct conversion and similar RF transmitters and receivers. This problem is solved using a virtual local oscillator (VLO™) signal which emulates mixing with a local oscillators (LO) signal. The VLO signal is constructed using complementary mixing signals that suppress mixing power in the bandwidth of the input signal, and within the bandwidth of the output frequency. Specifically, mixing is done in two or more stages, using time-varying mixing signals &phgr;1 and &phgr;2 which satisfy the following criteria: &phgr;1 * &phgr;2 having significant power at the frequency of the LO being emulated, one of &phgr;1 and &phgr;2 having minimal p ower around the frequency of the output signal y(t), and the other of &phgr;1 and &phgr;2 having minimal power around the centre frequency, fRF, of the input signal x(t).

Abstract: A signal convertor for modulating or demodulating an input signal x(t), comprising: a synthesizer for generating wideband mixing signals &phgr;1 and &phgr;2, which vary irregularly over time, where &phgr;1*&phgr;2 has significant power at the frequency of a local oscillator signal being emulated; a first mixer coupled to said synthesizer for mixing said input signal x(t) with said mixing signal &phgr;1 to generate an output signal x(t) &phgr;1; and a second mixer coupled to said synthesizer and to the output of said first mixer for mixing said signal x(t) &phgr;1 with said mixing signal &phgr;2 to generate an output signal x(t) &phgr;1 &phgr;2.