Analysis and Design of a Phase-Tunable Source Injection-Coupled LC Quadrature Oscillator

This paper presents the design and analysis of phase-tunable injection-coupled quadrature oscillator (PT-IC-QO). Like other LC QOs, the mismatches between LC tanks are the main source of phase error in this oscillator. Using tail current in network coupling is novel approach to design new IC-QO. One of the advantages using added extra tail current in coupling network is control of coupling factor and also that it drastically reduces supply noise over classic IC-QO. Analysis and simulation result show that phase error can be controlled and cancelled simply by using tunable tail current in network coupling while that is difficultly controlled in the previse work. The basic idea of the presented design to reduce phase error due to tank mismatches is its compensation with an intentional mismatch between \(I\hbox {/}Q\)-side injection current. Based on the equations, a new tunable source-injected QO is proposed which is able to cancel the phase errors up to \(\pm 20^\circ \), without undesirable impact on phase noise. To evaluate the proposed analysis and consequent designed quadrature oscillator, a 5.4-GHz CMOS PT-QO is designed and simulated using the practical \(0.18\,\upmu \hbox {m}\) TSMC CMOS technology.     

A CMOS Quadrature LC Oscillator using Automatic Phase/Amplitude Calibration

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.     

On the quadrature accuracy of in-phase coupled quadrature LC oscillator

In this article, closed-form equations are proposed for phase and amplitude errors of an in-phase coupled quadrature LC oscillator. First of all, the injected current from coupling network to switching one is analytically calculated in a novel approach. Then, fundamental equations are obtained to derive phase and amplitude errors which are results of mismatches of the tank's inductors, capacitors and resistors. The analysis shows that the LC tank's phase of this oscillator has a negligible deviation from zero that is desirable and causes low phase noise. Also, the study indicates that in-phase coupling of this structure generates an injection current that reduces the output current magnitude. In the following, a mechanism is proposed to compensate the phase error, using intentional mismatch in tail currents. Moreover, In contrast to previous works, there is not a considerable trade-off between phase error and phase noise; meaning phase noise is almost stable while phase error dramatically decreases. Next, Many simulations have been done in TSMC 0.18 μm to evaluate the proposed analytical equations and efficiency of the presented approach. Finally, all of these tests confirm the high accuracy of equations and capability of the mentioned technique.     

高性能超低功耗的4.224GHz正交LC VCO

采用Jazz0.18μm RF CMOS工艺设计并实现应用于MB-OFDM超宽带频率综合器的4.224GHz电感电容正交压控振荡器。通过解析的方法给出了电感电容正交压控振荡器的模型,并推导出简洁的公式解释了相位噪声性能与耦合因子的关系。测试结果显示,核心电路在1.5V电源电压下,消耗6mA电流,频率调谐范围为3.566~4.712GHz;在主频频偏1MHz处的相位噪声为-119.99dBc/Hz,对应的相位噪声的FoM(Figure-of-Merit)为183dB;I、Q两路信号等效的相位误差为2.13°。     

Low voltage low-phase-noise SB-QLCO using second harmonics coupling technique

A switched biasing quadrature oscillator with LC tanks (SB-QLCO) is proposed to achieve low voltage and low phase noise. In this work, coupling devices, capacitors, don’t contributes any noise and this second harmonics coupling technique leads to low voltage. The proposed QLCO was simulated in 0.18 μm CMOS process. Simulating results showed a phase noise of ?126 dBc/Hz at an offset of 1 MHz and a phasenoise figure of merit of 193 dB while consuming 6 mA from a 0.8 V power supply.     

A quadrature RC-oscillator with capacitive coupling

In this paper the capacitive coupling in quadrature RC-oscillators is investigated. The capacitive coupling has the advantages of being noiseless with a small area penalty and without increasing the power dissipation. The results show that a phase error below 1° and an amplitude mismatch lower than 1% are obtained with a coupling capacitance about 20% of the oscillator׳s capacitance value. Due to this kind of coupling, the phase-noise improves by 3 dB (to −115.1 dBc/Hz @ 10 MHz) and the increase of power requirement is only marginal leading to a figure-of-merit of −154.8 dBc/Hz. This is comparable to the best state-of-the-art RC-oscillators, yet the dissipated power is about four times less. We present calculations of frequency, phase error and amplitude mismatch that are validated by simulations. The theory shows that phase error is proportional to the amplitude mismatch, indicating that an automatic phase error minimization based on the amplitude mismatches is possible. The measurements on a 2.4 GHz voltage-controlled quadrature RC-oscillator with capacitive coupling fabricated in 130 nm CMOS circuit prototypes validate the theory.     

A symmetrical 6-GHz fully integrated cascode coupling CMOS LC quadrature VCO

A fully symmetrical integrated quadrature LC oscillator with a wide tuning range of 1.2GHz is presented. The quadrature voltage-controlled oscillator (QVCO) is implemented using a symmetrical coupling method which has been used to produce the large tuning range with a low control voltage and to achieve good phase noise performance in 0.18/spl mu/m complementary metal oxide semiconductor technology. The measured phase noise at 1MHz offset from the center frequency (5.5GHz) is -115 dBc/Hz. The QVCO draws 3.2mA from a 1.8V supply. The equivalent phase error between I and Q signal was at most 0.5/spl deg/.     

A new robust capacitively coupled second harmonic quadrature LC oscillator

A study of some reported superharmonic LC quadrature voltage-controlled oscillator (LC-QVCO) is performed in which it is shown that robustness of the quadrature oscillation varies depending on the coupling configuration. Next, a new superharmonic LC-QVCO is proposed in which the common source node in either of two identical cross-connected LC-VCOs is coupled via a capacitor to the node common between the two varactors in the LC-tank of the other LC-VCO. As a result of connecting common mode nodes, the currents flowing through the two coupling capacitors are comprised of only the even harmonics. In the proposed coupling configuration there exists a closed loop through which the second harmonic signals circulate. A qualitative argument is presented to justify the robustness of the quadrature nature of the proposed QVCO by applying the Barkhausen phase criterion to the second harmonic signals in the loop. Since the coupling devices are only two capacitors, no extra noise sources and power consumption are added to the core VCOs. A Monte-Carlo simulation showed that the phase error of the proposed QVCO caused by device mismatches is no more than 1°. Also, generalizing this method to several numbers of VCOs in a loop, multiphase signals can be generated. The proposed circuits were designed using a 0.18-μm RF CMOS technology and simulation results are presented.     

An automatic phase error compensating multiphase LC oscillator: analysis and design

In this work a self phase error compensating multiphase LC oscillator is proposed. Mismatches in LC tanks are considered as the main source of phase errors. Considering this, an analytical approach is proposed to find a relationship between phase errors and their corresponding coupling factors as a necessary condition for phase error cancellation then a self compensating circuit is proposed accordingly. The compensation circuit first detects the phase errors then employs them in a current tuner to change each stage coupling factor to reduce phase errors. The building blocks of the proposed circuit are investigated and the transistor level implementation of each one is presented afterwards. The theoretical results are evaluated and confirmed through simulations using ADS software in 0.18 μm CMOS technology. Simulation results show that not only phase errors are reduced with respect to the previous methods but also this procedure does not impose any further power consumption and phase noise to the circuit.     

A Comprehensive Analysis of Quadrature Signal Synthesis in Cross-Coupled RF VCOs

This paper presents a linear model for cross-coupled quadrature voltage-controlled oscillators (QVCOs) together with a simple generalized proof for the condition of quadrature oscillation. The analysis provides insight into the oscillation mechanism and the previously observed frequency shift when the magnitude and phase of the coupling signal are deliberately modified by a complex coupling coefficient K_c. It is demonstrated that the steady-state oscillation condition G_MR_p=1 holds only if G_M is replaced by an effective large-signal transconductance G_Meff that is a function of the coupling transconductance G _Mc and the imaginary part of K_c. Closed-form expressions for the phase imbalance and amplitude error in presence of mismatch between the LC tank circuits as well as device transconductances are also derived. We introduce the new concept of quadrature resistance/quadrature conductance (R_quad/G_quad), an incremental element synthesized by the coupling transistors, and show that its magnitude is responsible for the frequency shift and quadrature oscillation. A one-port model of the QVCO is studied and the loading effect of G_quad on the tank is examined. Particularly, it is shown that G_quad degrades the open-loop quality factor and worsens the phase noise. The analysis in this paper can be applied to most QVCO topologies presented in the literature     

Analysis and design of an optimally coupled 5-GHz quadrature LCoscillator

A 5-GHz quadrature LC oscillator has been realized, in which the two LC stages are coupled with phase shifters. Analysis on the behavioral level shows that an N-stage LC oscillator is optimally coupled when each stage is connected with phase shifters providing ±180°/N phase shift. Simulation of the 5-GHz two-stage quadrature LC oscillator reveals a 4.3-dB reduction in phase noise compared to a quadrature LC oscillator without phase shifters. Measurements of the 5-GHz quadrature LC oscillator, made in a 30-GHz f _T process, show a phase noise lower than -113 dBc/Hz, with a resonator quality factor of only 4 and an oscillator core power dissipation of 21.2 mW     

Effects of active Q enhancement on oscillator phase noise: an analysis

This article describes the effects of active Q enhancement on the performance of monolithic LC oscillator. Phase noise being the most important parameter for oscillators used in communication circuits, a lot of research efforts have been put in the direction of improving phase noise of fully on-chip LC oscillators over the past few years. Poor quality factor (Q) of on-chip passive components, specially that of spiral inductors limit the phase noise performance of LC oscillators. Use of active Q enhancement techniques has been proposed to improve phase noise but has not been proved by rigorous theory or supported by conclusive measurement results and thus require further investigation. In this article, it has been shown that active Q enhancement using transformer coupling, in fact, degrades the phase noise. The conclusion was reached based on theoretical analysis supported by simulation results.     

Low-power CMOS LC QVCO using zero-biased transistor coupling of MWCNT network-based VCO structure

This paper presents design, analysis and implementation of a 2.4 GHz QVCO (Quadrature Voltage Controlled Oscillator), for low-power, low-voltage applications. Cross coupled LC VCO (Inductor–Capacitor Voltage Controlled Oscillator) topology realized using integration of a micro-scaled capacitor and a MWCNT (Multi-Wall Carbon Nano-Tube) network based inductor together with the CMOS circuits is utilized together with MOS transistors as coupling elements to realize QVCO. With the passive coupling achieved from the MOS transistors, power consumption is minimized while maintaining a small chip area. The variable capacitors and the inductors are designed using ANSYS and imported through DAC components in ADS (Advanced Design software). Accurate simulation of the QVCO is performed in the software environments and the results are provided. The measurement results show that the QVCO provides quadrature signals at 2.4 GHz and achieves a phase noise of −130 dBc/Hz 1 MHz away from the carrier frequency. The VCO produces frequency tuning from 2.1 GHz to 2.60 GHz (20.83%) with a control voltage varying from 0 to 0.3 V. It achieves a peak to peak voltage of 0.59 V with an ultra low power consumption of 3.8 mW from a 0.6 V supply voltage. The output power level of the QVCO is −10 dBm, with an improved quality factor of 45. The phase error of the QVCO is measured as 3.1°.     

CMOS active transformers and their applications in voltage-controlled quadrature oscillators

This paper introduces CMOS active transformers synthesized using MOS transistors only. The proposed active transformers are evolved from their active inductor counterparts and offer a number of attractive characteristics as compared with spiral transformers including a tunable coupling ratio, large and tunable self and mutual inductances, high and tunable quality factors, and a small silicon area consumption. The characteristics of the proposed active transformers including the tunability of the self and mutual inductances, power sensitivity, noise, and quality factor are investigated both analytically and numerically using simulation. The application of the proposed active transformers is exemplified using a 1.6 GHz quadrature VCO implemented in TSMC-0.18 μm 1.8 V CMOS technology and analyzed using SpectreRF from Cadence Design Systems with BSIM3v3 device models. The total transistor area and power consumption of the VCO are 107 μm² and 10.8 mW, respectively. The phase noise of the VCO is −114.6 dBc/Hz at 1 MHz frequency offset.     

A 1-V 17-GHz 5-mW CMOS Quadrature VCO Based on Transformer Coupling

A 1-V 17-GHz 5-mW quadrature voltage-controlled oscillator (QVCO) based on transformer coupling is presented. Transformer coupling between two LC tank oscillators is proposed to achieve quadrature outputs with improved performance in terms of high frequency, wide tuning range, low phase noise, and low power as compared to existing active-coupling QVCOs. Implemented in a 0.18-mum CMOS process, the proposed QVCO measures a frequency tuning range of 16.5% at 17 GHz and phase noise of -110 dBc/Hz at 1 MHz offset while consuming 5 mA from a 1-V power supply and occupying a core area of 0.37 mm².     

A new constant-<Emphasis Type="Italic">Q</Emphasis> CMOS active inductor with applications to low-noise oscillators

This paper investigates the dependence of the quality factor of CMOS active inductors on the signal swing of the inductors and its impact on the phase noise of LC-tank oscillators employing the active inductors. A new CMOS active inductor with a nearly constant quality factor is proposed. Two 4-GHz LC oscillators with and without constant-Q active inductors have been implemented in UMC-0.13 μm 1.2 V CMOS technology and analyzed using SpectreRF from Cadence with BSIM3V3 device models. Simulation results demonstrate the phase noise of the oscillator with the constant-Q active inductor is −118dBc/Hz at 1 MHz frequency offset.     

Quadrature receiver mismatch calibration

This article introduces nonlinear regression techniques to estimate gain and phase mismatches between the in-phase (I) and quadrature (Q) branches of a quadrature receiver. Under modest assumptions, the system intrinsically follows a nonlinear regression model. The algorithm is effective, easily implemented, customizable, and requires few assumptions. Large-sample, jackknife, and bootstrap techniques provide on-line error assessment and parameter inference     

Comparative study of gigahertz CMOS LC quadrature voltage-controlled oscillators with relevance to phase noise

This review paper presents a comparative study of published integrated submicron CMOS quadrature voltage-controlled oscillator designs, based on LC resonator tanks operating at gigahertz frequencies. Although special reference to phase noise reduction is made, the comparison also concerns issues such as power consumption, tuning range and the phase accuracy of the quadrature signals. The effect of supply voltage reduction on the choice of the oscillator topology is also included in the discussion.     

Source-injection parallel coupled LC-QVCO

A simple source-injection parallel-coupled (SIPC) LC quadrature voltage controlled oscillator (QVCO) in which the additional noise contributions of the coupling transistors are nearly zero is proposed. The proposed topology is suitable for low phase noise and low supply voltage operation since it involves no additional transistor stacking. Compared to the conventional LC-QVCO, the SIPC topology designed for 2.4 GHz operation shows 19-12 dB improvement in phase noise at 10 kHz-1 MHz frequency offset, from the simulations based on 0.25 /spl mu/m CMOS technology.     

Single-VCO multi-band DTV frequency synthesizer with a divide-by-3 frequency divider for quadrature signal generation

A multi-band frequency synthesizer for In-phase and Quadrature (I/Q) LO signal generation in Digital TV tuners is presented. Using divisor numbers other than powers of 2 (2 ⁿ ) for quadrature generation, reduces the required frequency range of the VCO, hence the number of VCO circuits, in multi-band frequency synthesizers. In the proposed synthesizer, VHF, UHF and L-band frequencies are covered with only one VCO. This is achieved by using a novel divide-by-3 circuit which produces precise I/Q LO signals. The VCO tuning range in this design is 2,400–3,632 MHz which is covered by a 6-bit switched-capacitor bank. A fast adaptive frequency calibration block selects the closest VCO frequency to the target frequency by setting the coarse-tuning code prior to the start of phase lock. A programmable charge pump is used to reduce variations in PLL characteristics over the frequency range. The synthesizer has been fabricated in a 0.18 μm CMOS technology and the die area is 1.7 × 1.6 mm². It consumes 27 mA from a 1.8 V power supply. Measurement results show operation of the proposed divide-by-3 circuit over the entire VCO frequency range. The synthesizer quadrature output phase noise for UHF and VHF bands is <−131dBc/Hz at 1.45 MHz offset.