Designing Quadrature VCO in a Wide Range Frequency

The 5G network has been created to solve the limitation of communication coverage in large areas. One of the challenges of the 5G is the construction of quadrature oscillators in a wide range of high frequencies. Phase error and amplitude imbalance cause a decrease in the image rejection ratio (IRR), which affects the communication error vector magnitude (EVM). The quadrature phases are generated by a one-stage poly-phase filter (PPF) whose resistors consist of four N-type MOSFETs in triode mode, each of its four gate ends is set by a voltage. The feedback circuit constantly adjusts the center frequency of the PPF according to the input frequency by changing the resistance of the MOSFETs. In this research, the circuit is simulated in the advanced design system software environment in the frequency range of 2 to 6 GHz with a central frequency of 4 GHz, which has reduced the quadrature phase error to less than 1 to 9 degrees. Then, the governing mathematical equations of the circuit were extracted and the network function of the circuit was designed in the Simulink MATLAB environment. The main advantage of the Simulink method is the high speed of simulation.