Not only a voltage controlled oscillator (VCO) is one of the most significant component of every telecommunication system, but also it has been widely used in many other high-speed systems. In fact, a VCO has an important role in system operation, in other word, VCO is the heart of a system which gives existence to it. Nowadays, designing a high performance VCO for different applications is a challenging task for engineers. Moreover, up to now many designs and solutions have been proposed by the scientists to improve the performance of VCOs to be exploited in different cutting-edge applications. In this paper I will give a brief overview of the new techniques in designing high performance VCOs. Furthermore, the results of the proposed solutions have been compared with each other to see which method has advantages over the others.