  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.
