2N-order sub-harmonic frequency modulator having high carrier suppression ratio and direct conversion transmitter using the same

摘要

Disclosed herein is a 2^N-order sub-harmonic frequency modulator and direct conversion transmitter using the same. The direct conversion transmitter includes a digital modulation unit, a D/A conversion unit, a DC correction and low pass filter unit, a local oscillator, a poly phase signal generation unit, a 2^N-order sub-harmonic I/Q frequency modulation unit, a power amplification unit, and an antenna. The digital modulation unit digitally modulates a base-band signal and then outputs I and Q component signals. The D/A conversion unit converts the I and Q component signals into analog I and Q component signals. The DC correction and low pass filter unit adjusts DC interfaces of the analog I and Q component signals, passes low frequency components of the analog I and Q component signals and generates I and Q components of a base-band signal. The local oscillator generates a sine wave signal with a frequency of F_TX/2^N. The poly phase signal generation unit generates a poly phase signal with 2^N+1 phases. The frequency modulation unit mixes the I and Q components with the poly phase signal with 2^N+1 phases to generate an output signal with a frequency of F_TX. The power amplification unit amplifies the output of the frequency modulation unit to a required level. The antenna radiates the output signal of the power amplification unit.