In this paper, considering the nonlinear effects in two ports consisting of transistor, a general method is proposed for estimating the amplitude of high-frequency ring oscillators. The proposed method can be generalized to various structures that can be disassembled into similar two ports. Moreover, in each CMOS process, a design procedure can be followed to obtain the desired output power and frequency. This is the first time that the frequency and amplitude of oscillator are related to each other in a system of nonlinear equations. First, considering the maximum achievable oscillation frequency, the analysis of ring oscillator structure is performed for the given output power. The results show that the proposed structure operates at 7 to 18% higher oscillation frequency compared with conventional structures. In the next step, assuming that the oscillator structure and passive network topology are known, another system of nonlinear equations is defined for designing the oscillator for the given frequency and amplitude of oscillation. Finally, the implicit solution, which includes the passive network elements connecting to the transistor, is obtained.The results of equations follow the simulation results with an acceptable error (1% frequency error and about 5% amplitude error). /journal/cta 84 84 102 analysis). 3-9 Although most of the mentioned analyses are successful to a large extent in their intended frequency range, there exist some issues when it comes to amplitude analysis of high-frequency oscillators:A: Since the active device model is much more complicated at high frequencies, the order of differential equations describing its structure is higher, and this practically inhibits the analysis.B: The existing methods are not general, and for each individual structure, a specific process must be contemplated. However, one prefers to use a generalized method for analyzing various oscillators.The milestone of these efforts was where the researchers avoided the mentioned issue and focused on the use of twoport network parameters of transistor, and in this way, they were able to provide a new formulation for optimal oscillator designs. Accordingly, amplitude analysis of high-frequency oscillators near the f max of transistor is a subject that has been rarely investigated. It is worth mentioning that the designing of an optimal oscillator with emphasis on the optimization of the output power has been thoroughly investigated in Gilmore and Rosenbaum. 10 In more precise words, for given dimensions of an active device, some conditions are imposed on the passive network parameters [Y] and [S] so that the oscillator can operate at its maximum possible output power. Recently, Momeni and Afshari showed that it is possible to approach an optimal oscillator design by separating ring structures into the building two ports and analyzing them. 11 Using another approach, Sharma and Krishnaswamy designed a high-frequency ring oscillator with the maximum power gain in each stage. 12 However, these methods are based on smal...
