In addition, simulations of various active inductors were performed using cadence 6.16 environment, which makes it easy to depict the high-performance active inductor in an insightful research perspective. The simulation results showed the variation in the performance of different active inductor models in terms of quality factor, current consumption, inductance adjustment and frequency range.
L IST OF T ABLES
INTRODUCTION
- Motivation 1.2 Objective
- Definition 1.3.2 History
- Applications 1.4 Research Overview
- Thesis Layout
- Motivation
- Objective
- ISM Band
- Definition
- History
- Applications
- Research Overview
- Software Used
These active inductor circuits would save area and add easy inductance value adjustability. The ISM bands were first established at the ITU International Telecommunication Conference in Atlantic City, 1947.
SPIRAL AND ACTIVE INDUCTOR
Spiral Inductors
- Planar spiral inductors 2.1.2 Stacked spiral inductors
- Figures of merit of the inductors 2.2 Characteristics of Spiral Inductors
Active Inductors
- Advantages of active inductors
- Planar spiral inductors
- Stacked spiral inductors
- Layout of spiral inductors
- Figures of merit of the inductors
W is the width of the spiral and s is the spacing between the turns of the spiral. It is seen that the inductance of stacked spiral inductors increases approximately linearly with the increase in the number of spiral layers of the inductors.
Characteristics of Spiral Inductors
Large and tunable inductance: The inductance of CMOS active inductors is inversely proportional to the transconductance of the transistors that synthesize the inductors. Coarse tuning of the inductance of active inductors is usually achieved in this way.
CMOS ACTIVE INDUCTOR TOPOLOGIES
- Lossless Single- Ended Gyrator-C Active Inductors
- Lossy Single-Ended Gyrator-C Active Inductors 3.4 Lossy Floating Gyrator-C Active Inductors
- Performance Parameters of Active Inductors .1 Frequency range
- Quality factor
- Power consumption
- Implementation of Single-Ended Active Inductors .1 Basic Gyrator-C active inductors
- Yodprasit-Ngarmnil active inductor 3.7.2 Lin-Payne active inductor
- Thanachayanont-Payne active inductor 3.7.4 Weng-Kuo Cascode active inductors
- Lossless Floating Gyrator-C Active Inductors
- Lossy Single-Ended Gyrator-C Active Inductors
- Lossy Floating Gyrator-C Active Inductors
- Performance Parameters of Active Inductors
- Frequency range
- Implementation of Single-Ended Active Inductors
- Basic Gyrator-C active inductors(Common Source & Common Drain)
- Basic Gyrator-C active inductors(Common Source & Common Gate)
- Different Active Inductor Models
- Yodprasit-Ngarmnil active inductor
That is why the final name of the network is active lossless Gyrator-C inductor. To simplify the analysis, we continue to assume that the transconductances of the transconductors are constant. The limited input and output resistances of the gyrator-C network transconductors, however, have no effect on the inductance of the active inductor.
The self-resonant frequency of an active inductor is determined by the cutoff frequency of the transconductors that make up the active inductor. The finite input and output impedances of transconductors consisting of active inductors result in a limited quality factor. It is also seen that Rp has no effect on the frequency range of the active inductor.
The sensitivity of the quality factor of the active inductor with respect to Rs and Rp is examined individually in Figure 3.9. We see that Q1 governs the nature of the active inductor and is then generally used to measure the quality factor of active inductors.
VgM3
Lin-Payne active inductor
This minimum supply voltage for the outer transistor is higher with a quantitative comparison with the inner transistor branch.
Thanachayanont-Payne active inductor
The former is at the expense of breaking down and should be kept away in this way. Thus, cascode designs can successfully improve the frequency range of active inductors by lowering the lower limit of the frequency range of active inductors.[29]. Weng-Kuo cascode active inductor negates the limitation that the inductance and the quality factor cannot be changed.
The simplified schematic of the active Weng-Kuo inductor is shown in Figure 3.14 where gm1 is proportional to J1+J3 while gm3 is only proportional to J1.
OSCILLATOR
General Concept
Classification
- Feedback oscillator 4.2.2 Relaxation oscillator
Further Classifications
Operation of Oscillator
- The Hartley oscillator 4.6.3 The Armstrong oscillator
Ring Oscillator
V out Oscillator
- Relaxation oscillator
- Further Classification
- Oscillators With RC Feedback Circuits
- The Wien-Bridge oscillator
- The Phase-Shift oscillator
- Twin-T oscillator
- Oscillators With LC Feedback Circuits
- The Colpitts oscillator
- The Hartley oscillator
- The Armstrong oscillator
- Voltage Controlled Oscillator(VCO)
The circuit gain must be equal to (or greater than) unity and. ii) The phase shift around the circuit must be zero. The voltage gain around the positive feedback loop must be greater than 1 so that the amplitude of the output can be built up to a desired level. Consideration of the LC network shows that its attenuation (from amplifier output to input) is.
As in the case of the Colpitts circuit, the oscillation frequency is the resonant frequency of the phase shift network. The oscillation frequency is determined by the inductance of the primary winding (Lpri) parallel to C1.[49][51]. Varying the DC input voltage adjusts the output frequency of the signal produced.
Tuning Gain: The gain of the voltage controlled oscillator is measured in volts per Hz (or V/MHz, etc.). The voltage controlled oscillator gain affects some of the general loop design considerations and calculations.
LC VOLTAGE CONTROLLED OSCILLATOR (VCO)
- Introduction
- General LC tank VCO 5.1.2 Cross coupled LC VCO
- LC Tank Properties 5.3 Phase Noise
- Figure of Merit
- LC VCOs With Spiral Inductor Drawbacks 5.6 LC VCOs With Active Inductors
- LC VCOs with Lin-Payne active inductors
- LC VCOs with Wu Current-Reuse active inductors
- General LC tank VCOs
- Cross coupled LC VCOs
- LC Tank Properties
- Phase Noise
- LC VCOs With Spiral Inductors Drawbacks
- LC VCOs With Active Inductors
- LC VCOs with Lin-Payne active inductors
- LC VCOs with Wu Current-Reuse Active Inductors
The voltage gain of the delay stage is given by Av = −gmZ, where Z is the LC tank impedance. This is because for an ideal LC tank, the impedance of the tank is infinite at the resonant frequency. The resistance of the negative resistor can be adjusted by varying the DC bias current.
The characteristics of the LC tank therefore play an important role in the overall performance of the VCO. The most quoted expression of power of the single sideband phase noise of a VCO is stated as [59]. This region is identified as the 1/f3 region and affects the phase noise of the oscillators the most.
This negative resistance is used to cancel out the parasitic resistances of the active inductors. The high level of the phase noise is mainly due to the use of the active inductors and the tail current source of the negative resistor.
PROPOSED ACTIVE INDUCTOR BASED VCO
- Applied formula
- Choosing (W/L) ratio for
MOSFETs used in Active Inductor 6.2 Schematic Representation of Active Inductor
- Barkhausen criteria 6.3.2 Conditions
- Choosing the configuration
- Choosing W/L ratios and applied voltages
- Schematic Representation of Proposed Active Inductor Based VCO
- Weng-Kuo Active Inductor
- Choosing (W/L) ratio for MOSFETs used in Active Inductor
- Schematic Representation of Active Inductor
- Active Inductor Based VCO
- Barkhausen criteria
- Conditions
- Schematic Representation of Proposed Active Inductor Based VCO
But an increase in W/L causes an improvement in drain to source current (Ids), which will increase power consumption. So the optimal value of the W/L ratio is 15 μm/100 nm, which is relatively larger than others to amplify the Q factor and self-resonance frequency. The higher value of the W/L ratio will result in an increase in the drain-to-source current.
M5: M5 is the replacement of the current source J3 which is used to tune the inductance and Q-factor independently. This back-to-back configuration, also called a coupled transistor pair will act as a negative resistor to provide high voltage gain by overcoming the ohmic loss of the LC tank. M7: M7 is used as a bias current source to control the resistance of the connected transistors.
Vcontrol=0V to 0.8V is used to tune both the capacitance of the Mcap and the oscillation frequency. Mcaps are MOS capacitors and M7 at the tail of the network act as bias current sources for Mneg.
SIMULATION RESULTS
- Comparison of different models 7.2 Oscillator
- Simulation
- Active Inductor simulation &
- VCO simulation & performance analysis
Performance Comparison
Comparative Analysis of Active Inductors
- Simulation
- Comparison of different models
Frequency(GHz)
After exceeding the self-resonant frequency or cut-off frequency, the Q-factor becomes negative as the inductance of the inductor becomes negative. On the contrary, in Figure 7.2, arising loss from parasitic resistance increases due to insertion of MOS device, which degrades the quality factor. Despite this drawback, the insertion of the MOS improves the frequency range as well as the inductance.
Nevertheless, using MOS as a power source in circuits has no significant influence, as the quality factor for it turns out to be 0.5806, which is much lower compared to others. Lin-Payne active inductor replacing ideal current source with saturated MOS maximizes frequency range with low voltage space. But Weng-Kuo offers a wider frequency range than Thanachynont-Payne, namely 7.5 GHz and 11.87 GHz.
In addition, Weng-Kuo is preferable to other models that have the property of tuning the quality factor and inductance independently, which became possible after introducing an additional current source into the circuit. Although the power consumption of this active inductor is more than Thanachynont-Payne (1.08 mW and 8.38 mW) and the amount is 10.71 mW due to the additional current source, it is very favorable with the increase of the factor of quality with numerical values 4,263 and 2,373.
Frequency(GHz)0
Oscillator
- Active Inductor simulation & performance analysis
- VCO simulation & performance analysis
The cross-connected pair MOS (Mneg) is used to provide negative resistance to start oscillation with a large voltage gain. A MOS (M7) current source is used to regulate the resistance of the cross-connected MOS transistors. MOS Mcap together with the control voltage source Vcontrol is used to set the oscillation frequency of the oscillator.
The charts below show the characteristics of the inductor such as quality factor, inductance, and impedance. To obtain sinusoidal oscillation and determine the performance parameter, transient analysis, pss and pnoise with 5 harmonics were performed. A parameter called figure of merit (FOM) is introduced to characterize the performance of the VCO.
The VCO provides a stable oscillation voltage along with a high output power, which are the extraordinary highlights of the VCO. The frequency range includes the Bluetooth operating frequency, and the low variation of the FOM demonstrates the stability of the VCO's performance.
Performance comparison
The VCO has a low power consumption and a higher figure of merit (FOM) consumption, outperforming the other designed VCOs mentioned.
CONCLUSION
- Analytical Observation
- Frequency Range .1 Applications
- Future Scope
- Frequency Range
- Applications
From the beginning of our research, we focused on the simulation and comparative analysis of different designs of active inductors based on the C gyrator for different applications. Power consumption, frequency range are also significant parameters for practical RF applications which depend on the frequency range, power consumption of inductors. Since we are concerned about frequency range, adaptability and power consumption of inductors, it was very effective to work on active inductor over coil inductor. Therefore, in this paper we emphasized on choosing the best active inductor model For this purpose, our research methodology was advanced by considering different topologies such as Yodprasit-Ngarmnil Active Inductor, Lin-Payne Active Inductor, Thanachayanont-Payne Active Inductor, Weng-Kuo Active Cascode. Inductor.
Under these configurations, from theoretical analysis, it seemed that Weng-kuo based active inductor would show better tunability for designing voltage controlled oscillator for inserting additional current source which ensured tunability of quality factor and inductance independently. From the simulation results, we found that the quality factor of Weng-Kuo based active inductor was much higher than that of the other topologies. Based on this analysis, we decided to use Weng-kuo based active inductor for VCO design. To obtain sinusoidal oscillation and determine the performance parameter, transient analysis, pss and pnoise with 5 harmonics have been performed.
In this research work, comparative analysis was performed among different active inductor models, and all active inductor models were based on the basic gyrator-C topology following configuration 8.1, where the forward path is common-source configured and the feedback path is common-drain configured. In the future, the simulation of the later basic gyrator-C active inductor can be performed to analyze its performance parameters such as current consumption, quality factor, frequency range, etc., and for this configured active inductor, a new design of VCO can be obtained, whether to check comparative performance with the previously designed voltage controlled oscillator models with the new one.
