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چکیده
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This paper proposes a Dual-Coupled CMOS LC Quadrature Oscillator (DC-QO) which composed of two coupling networks. Two LC oscillators coupled via both active (source-injection) coupling and passive (noiseless inductive and capacitive) coupling in the proposed QO. Therefore, coupling ratio increased and the main mismatches in LC tank would be more controllable. In this way, strong coupling performance reduces the phase-sensitivity versus mismatches. The combination of two coupling techniques provides stronger coupling operation, however doesn’t effect on the phase noise performance. Since applied active coupling in the tail of proposed QO inject current from each side own outputs, so in zero-crossing points there is no injection . Also, the applied passive coupling uses noiseless elements (inductor and capacitor), therefore the phase noise performance isn’t degraded. Simulation results show that phase noise is desirable with low power consumption while phase error has been controlled, so the trade-off between phase noise and phase error cancelled. To evaluate the validity of proposed QO, a designed DC-QO simulated using the practical 0.18 m TSMC CMOS technology at 3.07 GHz fundamental-frequency. The DC-QO consumes3.371 mW from a 1.8V power supply, phase noise is -129.9 (dBc/Hz) @1 MHz and -138.5 (dBc/Hz) @3 MHz offset frequencies with the quality factor (Q=9.4) and is desirable. The Figure of Merit (FOM) of -193.363 (dBc/Hz) achieved. The obtained experimental results confirm the reliablity of the proposed DC-QO.
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