Patent ID: 8306484
Filing Date: 2012-11-06
Classification: H04B

Abstract:
1. A direct-conversion transmitter with resistance to local oscillator pulling effects comprises: a local oscillation circuit having a two point voltage-controlled oscillator and a phase locked loop electrically connected with the two point voltage-controlled oscillator, wherein the two point voltage-controlled oscillator enables to output a local oscillation signal and comprises an injection port, a matching circuit electrically connected with the injection port, a voltage modulation port, an LC resonator electrically connected with the matching circuit and the voltage modulation port, a Colpitts capacitor unit electrically connected with the LC resonator, and an active circuit electrically connected with the LC resonator and the Colpitts capacitor unit; a quadrature modulator electrically connected with the local oscillation circuit and applied for receiving the local oscillation signal to generate a modulation transmit RF signal; a power amplifier electrically connected with the quadrature modulator and applied for receiving the baseband modulation signal to generate a transmission signal; a first variable analog delay device electrically connected with the power amplifier and applied for receiving the transmission signal to generate a delay signal; a variable analog attenuator electrically connected with the first variable analog delay device and applied for receiving the delay signal to generate a first modulation signal, which serves as a relative self-dependent modulation interference; an inner self-injection loop comprising a second variable analog delay device, a first phase shifter electrically connected with the second variable analog delay device and a first variable gain amplifier electrically connected with the first phase shifter, wherein the local oscillation signal is fed to the inner self-injection loop to generate a second modulation signal; and a power combiner electrically connected with the variable analog attenuator and the inner self-injection loop and applied for receiving the first modulation signal and the second modulation signal to generate a mixed signal, wherein the mixed signal is fed to the injection port of the two point voltage-modulated oscillator.