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Summary: This study developed a local oscillator (LO) with low phase noise and low power consumption. The proposed oscillator core comprises a pair of cross‐coupled transistors, which are fed by another pair of transistors that injects current at moments close to the peak of output voltage. The position of the current injection transistors, which are inserted in series with the cross‐coupled transistors, affects the waveform of current injected into an inductive–capacitive (LC) tank. Installing a capacitor on the source node of the cross‐coupled transistors increases the current injected into the LC tank and thereby augments the output voltage amplitude and power efficiency of the LO. The resonator phase shift and Q can be corrected by adjusting the source capacitance, which filters noise. These changes reduce the phase noise to −123.4 dBc/Hz at a frequency offset of 1 MHz and improve oscillator performance with a figure of merit equal to −193.5 dBc/Hz. To evaluate the LC tank, a 5 GHz LO was simulated at 1.8 V power supply and 2.5 mW power consumption. The simulation was conducted using a practical 0.18 complementary metal–oxide–semiconductor model manufactured by the Taiwan Semiconductor Manufacturing Company. The simulation results confirmed the analytical findings. [ABSTRACT FROM AUTHOR]

In this paper, an analytic approach for the estimation of the phase and amplitude error in series coupled LC quadrature oscillator (SC-QO) is proposed. The analysis results show that imbalances in source voltage of coupling transistor because of mismatches between LC tanks are the main source of the phase and amplitude error in this oscillator. For compensation of the phase and amplitude error, a phase and amplitude-tunable series coupled quadrature oscillator is designed in this paper. A phase shift generation circuit, designed using an added coupling transistor, can control the coupling transistor source voltage. The phase and amplitude error can simply be controlled and removed by tuning the phase shifter, while this correction does not have undesirable impact on phase noise. In fact, the proposed SC-QO generates a phase shift in the output current, which reduces the resonator phase shift (RPS) and improves phase noise. The phase and amplitude tunable SC-QO is able to correct the phase error up to ±12°, while amplitude imbalances are reduced as well. To evaluate the proposed analysis, a 4.5-GHz CMOS SC-QO is simulated using the practical 0.18-μm TSMC CMOS technology with a current consumption of 2 mA at 1.8-V supply voltage. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this paper, a new method for computing the amplitude and frequency of differential ring oscillators (ROs) is proposed. The analysis is performed in two separate parts. In the first of these, equations are derived with the assumption of a sinusoidal waveform of outputs, while in the other, the outputs are assumed to be exponential. It is shown that the derived equations for frequency and amplitude are sufficiently exact. In addition, conditions in which sinusoidal and exponential output occur are thoroughly discussed. In the instances in which the results did not satisfy the necessary conditions for sinusoidal output, the output is assumed to be exponential. Moreover, the related analytical equations are written, and the new expressions for frequency and amplitude of ROs are derived. Analytical results are confirmed by simulation results, using the Taiwan Semiconductor Manufacturing Company 0.18 µm technology model. The simulation results indicate the high level of accuracy of the proposed model. [ABSTRACT FROM AUTHOR]

In this paper, a novel LC quadrature oscillator (QO) is presented that can simply and automatically cancel the phase and amplitude errors raised by mismatches in LC tanks; the major source of phase and amplitude errors. The design is based on method of using unequal coupling factors in a parallel quadrature oscillator (P-QO). This method shows how we can cancel phase and amplitude errors simultaneously by choosing appropriate inversely proportional coupling factors. To cancel the errors, the proposed circuits first sense the phase error and increase or decrease the difference between the coupling factors accordingly. When tuning tail currents, the coupling factors can be simply adjusted. The entire system has a block diagram like a PLL. The dynamics of the proposed circuit is analyzed, and it is shown how the phase and amplitude error is canceled in response to an imposed LC tank mismatch. To evaluate the circuit, a QO has been designed to oscillate at 5 GHz with 1.8 V supply and 6.2 mA current consumption. The circuit has been simulated using TSMC 0.18 CMOS practical model where all the results confirm the analytical results. [ABSTRACT FROM AUTHOR]