Design of the two-tone oscillators by using sigma-delta technique

In this paper, a novel technique for analyzing and designing a high performance two-tone oscillator is presented. The proposed two-tone oscillator begins with two parallel integration units and four coefficients. In order to avoid having coefficients that are too small, two of the coefficients remain constant while the others are variable. The analysis illustrates that the coefficients and the initial values of integration units determine the oscillation frequency and amplitude, respectively. A 4^th-order leapfrog sigma-delta modulator that follows the resonator to shape the noise floor is proposed for constructing the oscillator. A useful technique called the time-division multiplexing (TDM) is adopted for generating two-tone oscillation because of the great hardware overhead. An example is used to demonstrate that a two-tone oscillator with the TDM technique can achieve a SNR over 90 dB within the 20 kHz base-band. The proposed two-tone oscillator can be used in high-resolution signal processing systems such as self-test applications, telecommunications, and arbitrary signal generation.