Patent ID: 8442459
Filing Date: 2013-05-14
Classification: H03C,H03G

Abstract:
1. A transmitter that generates and outputs a transmission signal based on inputted data, the transmitter comprising: a signal generating section that generates an amplitude signal and a frequency signal, based on an amplitude component and a phase component, which are obtained by performing signal processing on the inputted data; an angle modulation section that performs angle modulation on the generated frequency signal, so as to output an angle modulated signal; an amplitude amplification section that outputs an amplified signal in accordance with a magnitude of the generated amplitude signal; a low pass filter section which attenuates a radio frequency component included in the amplified signal output from the amplitude amplification section, so as to output an attenuated signal; an amplitude modulation section which receives the angle modulated signal output from the angle modulation section, and which performs amplitude modulation on the received angle modulated signal using the attenuated signal output from the low pass filter section, so as to output a modulation signal; and a controlling section that changes an amount of the attenuation performed on the radio frequency component by the low pass filter section in accordance with at least one of: (i) a modulation method of the inputted data; (ii) a modulation condition of the inputted data; (iii) a reception band; (iv) an output power of the modulation signal; and (v) a frequency of the modulation signal, wherein the low pass filter section includes: a variable inductor that is inserted between the amplitude amplification section and the amplitude modulation section in series; and a variable capacitor that grounds an output side of the variable inductor, and wherein the controlling section includes a pre-defined look-up table for selecting a most suitable capacitor value according to the modulation method of the inputted data and the reception band, and changes a value of at least the variable capacitor according to the look-up table, so as to change the amount of the attenuation performed on the radio frequency component by the low pass filter section.