Multitone signal generator using noise-shaping technique

A novel technique for analysing and designing a high performance multitone signal generator is presented. The proposed multitone signal generator is based on two parallel integration units and four coefficients. In order to avoid having coefficients that are extremely small, two of the coefficients remain constant while the others are variable. Theoretical analysis illustrates that the coefficients and the initial values of integration units determine the oscillation frequency and amplitude, respectively. A 4th-order leapfrog sigma-delta modulator following the resonator to shape the noise floor is proposed for constructing the signal generator. A useful technique called time division multiplexing (TDM) is adopted for generating multitone oscillations because of the reduced hardware overhead. An example is used to demonstrate that a two-tone oscillator using the TDM technique achieves an SNR of over 90 dB within the 20 kHz baseband. The proposed multitone oscillator can be used in high-resolution signal processing systems such as self-test applications, telecommunications, and arbitrary signal generation.