Proposed Structure of this dissertation presents technique of injection locking enhancement in divide by 2 injection locked frequency divider using phase shifter circuit. The ILFD’s structure is based on dual resonance 4th order LC tank CMOS cross coupled oscillator. Dual resonance resonator provides wide frequency range, however it has dual band locking range which lower band locking range regarding lower resonance frequency and higher band locking range regarding higher resonance frequency. Therefore, employed resistor in the tank contribute to overlap dual band and make a single band frequency range. With using phase shifter circuit, the ILFD exhibits wider locking range while the resistor is less than previous structure that needs higher resistor to reach an equal amount. The current generated by the phase shifter circuit with new angle toward oscillator current injects into resonator tank and produce a new locking range with new angle of locking. Differential outputs of the ILFD are connected to phase shifter’s input. When differential signals have peak value, no current flow through phase shifter circuit and when differential signals passing their transition time, an appropriate current with phase angle close to ideal phase shift angle will be produced. The effect of phase shifter current is analyzed in this work and simulation results evaluate the proposed idea. Simulations of this structure has been done using TSMC CMOS 0.18μm process with supply voltage of 0.95 V. The proposed ILFD has 7.7mA current and 7.32mW power consumption. The ILFD with phase shifter circuit provides locking range of 5.25 GHz (4.3 GHz – 9.55 GHz) and relative locking of 75.81% at incident power of 0 dBm.