Simple Oscillator with Enlarged Tunability Range Based on ECCII and VGA Utilizing Commercially Available Analog Multiplier
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2016-04-01 |
| Journal | Measurement Science Review |
| Authors | Roman Ć otner, Jan JeĆĂĄbek, Norbert HerencsĂĄr, JiunâWei Horng, Kamil Vrba |
| Institutions | Chung Yuan Christian University, College of Polytechnics Jihlava |
| Citations | 15 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: High-Frequency Tunable Oscillator
Section titled âTechnical Documentation & Analysis: High-Frequency Tunable OscillatorâExecutive Summary
Section titled âExecutive SummaryâThis research demonstrates a highly tunable, high-frequency oscillator design achieving independent electronic control of both the Condition of Oscillation (CO) and the Frequency of Oscillation (FO). The results highlight the potential for high-speed analog circuits but underscore critical material limitations that 6CCVD diamond substrates are uniquely positioned to solve.
- Performance Achieved: Experimental FO tunability range of 3.7 MHz to 27.1 MHz, significantly exceeding the typical 10 MHz limit for simple oscillator structures.
- Key Innovation: Utilization of a voltage-mode multiplier (AD835) as a Variable Gain Amplifier (VGA) with dual polarity (±A), enabling crucial extension of the FO control range.
- Control Mechanism: Independent electronic control of CO (via current gain B of the ECCII) and FO (via voltage gain A of the VGA).
- Material Challenge: The discrete solution exhibits high power consumption (300 mW) and extreme sensitivity to parasitic capacitance (estimated at ~20 pF), which causes large deviations from ideal frequency calculations.
- 6CCVD Value Proposition: Integrating this high-power, high-frequency design onto 6CCVDâs Electronic Grade Single Crystal Diamond (SCD) substrates mitigates thermal load and minimizes dielectric parasitics, enabling stable operation and frequency scaling beyond the 27.1 MHz limit.
- Application Potential: Ideal for integration into high-frequency signal sources, short wave/medium wave transmitters, and digital amplitude keying systems.
Technical Specifications
Section titled âTechnical SpecificationsâThe following data points were extracted from the experimental verification and comparative analysis (Table 1, âprop.â row).
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Measured FO Range | 3.7 - 27.1 | MHz | Achieved experimental tunability range. |
| Calculated Ideal FO Range | 5.4 - 48.2 | MHz | Based on ideal component values and A range (-0.94 to 3.71). |
| Maximum THD | 3.7 | % | Total Harmonic Distortion across the full FO range. |
| Narrower THD Range | < 1.5 | % | Achieved in the 7 MHz to 20 MHz range. |
| Power Consumption | 300 | mW | High consumption for the discrete solution. |
| Output Voltage Fluctuation | Max 30 | mVp-p | Change in output level across the FO range (175-205 mVp-p). |
| Working Capacitors (C) | 33 | pF | Selected for high-frequency operation. |
| Estimated Parasitic Capacitance | ~20 | pF | Value comparable to working capacitors, causing large FO deviation. |
| Active Elements Used | 2/4 | Discrete | ECCII- (EL2082), DT (OPA860), AD835 Multiplier. |
| CO Control Parameter | B | N/A | Current gain controllable by DC voltage (VSETB). |
| FO Control Parameter | A | N/A | Voltage gain controllable by DC voltage (VSETA). |
Key Methodologies
Section titled âKey MethodologiesâThe experimental design focused on modifying a simple ECCII-based oscillator structure to achieve independent electronic control and extended tunability using high-speed commercial components.
- Circuit Modification: The basic ECCII oscillator (Fig. 2) was modified by inserting a Variable Gain Amplifier (VGA) into the feedback loop to decouple the Condition of Oscillation (CO) and Frequency of Oscillation (FO) equations.
- Active Element Selection: Commercially available, high-speed discrete components were utilized:
- ECCII- (EL2082) for current control (gain B).
- âDiamond Transistorâ (DT) OPA860 used as a current inverter and voltage buffer.
- AD835 high-speed voltage-mode four-quadrant multiplier used as the VGA (gain A).
- High-Frequency Component Selection: Low-value passive elements were chosen to target operation in the tens of MHz range (C1 = C2 = 33 pF, R1 = 120 + 95 Ω, R2 = 220 Ω).
- Tunability Extension: The AD835 VGA was operated with dual polarity (±A), allowing the numerator of the FO equation (Equation 5) to drop below 1, significantly extending the lower limit of the tunable frequency range.
- Amplitude Stabilization: A simple Automatic Gain Control (AGC) circuit was implemented using two BAT42 diodes (2xBAT42) to stabilize the output amplitude during the tuning process.
- Parasitic Analysis: A non-ideal model (Fig. 5) was developed to estimate the impact of parasitic capacitances (~20 pF) from active element terminals and PCB traces on the real FO.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe successful replication and scaling of this high-frequency, high-power oscillator design require materials that minimize parasitic effects and manage thermal outputâchallenges inherent to the discrete solution presented. 6CCVDâs MPCVD diamond materials are the optimal platform for next-generation integration.
Applicable Materials
Section titled âApplicable MaterialsâThe high operating frequency (up to 27.1 MHz) and significant power density (300 mW) demand a substrate with superior thermal and dielectric properties to maintain stability and linearity.
| 6CCVD Material | Recommendation | Rationale for Application |
|---|---|---|
| Electronic Grade Single Crystal Diamond (SCD) | Primary Recommendation | Highest thermal conductivity (> 2000 W/mK) for managing the 300 mW power dissipation. Ultra-low dielectric loss tangent minimizes parasitic capacitance (the paperâs primary limitation), allowing the circuit to approach the ideal calculated FO range (up to 48.2 MHz). |
| High-Purity Polycrystalline Diamond (PCD) | Alternative for Larger Scale | Available in larger dimensions (up to 125mm wafers). Excellent thermal properties and low dielectric constant suitable for integrated high-frequency modules where size scaling is critical. |
| Boron-Doped Diamond (BDD) | For Integrated Resistors | If the design is integrated, BDD films can be used to create highly stable, high-power integrated resistors (R1, R2) directly on the substrate, replacing discrete passive elements and further reducing parasitic inductance/capacitance. |
Customization Potential
Section titled âCustomization Potentialâ6CCVD offers specialized fabrication services essential for integrating and optimizing high-frequency analog circuits like the proposed oscillator.
- Custom Dimensions: We provide diamond plates and wafers up to 125mm (PCD) and SCD up to 500”m thick, allowing for the integration of complex multi-chip modules or monolithic microwave integrated circuits (MMICs).
- Precision Polishing: Our SCD material is polished to an ultra-smooth finish (Ra < 1nm), critical for high-quality thin-film metalization and minimizing surface scattering losses at high frequencies.
- Advanced Metalization: The integration of active components (ECCII, VGA) requires robust interconnects. 6CCVD offers in-house metalization services including Au, Pt, Pd, Ti, W, and Cu, tailored for high-speed wire bonding and flip-chip integration.
- Laser Cutting & Shaping: Custom laser cutting services ensure precise component dimensions and alignment necessary for minimizing parasitic effects in high-frequency layouts.
Engineering Support
Section titled âEngineering SupportâThe research paper noted that parasitic analysis is âhighly requiredâ and that minimal deviation between expected and real values is a major challenge. 6CCVDâs in-house PhD team specializes in diamond material science and high-frequency device integration.
- Parasitic Mitigation: We provide consultation on material selection and substrate design to minimize the impact of parasitic capacitance and inductance, helping engineers bridge the gap between ideal calculation (48.2 MHz) and measured performance (27.1 MHz).
- Thermal Management: Our experts assist in designing thermal stacks utilizing diamondâs superior conductivity to manage the high power density (300 mW) and ensure frequency stability across varying operating temperatures.
- Application Extension: We offer support for extending this research into advanced applications, such as high-power RF signal generation or integrated sensor systems requiring highly stable, tunable sources.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract This work presents an example of implementation of electronically controllable features to an originally unsuitable circuit structure of oscillator. Basic structure does not allow any electronic control and has mutually dependent condition of oscillation (CO) and frequency of oscillation (FO) if only values of passive elements are considered as the only way of control. Utilization of electronically controllable current conveyor of second generation (ECCII) brings control of CO independent of FO. Additional application of voltage amplifier with variable gain in both polarities (voltage-mode multiplier) to feedback loop allows also important enlargement of the range of the independent FO control. Moreover, our proposal was tested and confirmed experimentally with commercially available active elements (âDiamond transistorâ, current-mode multiplier, voltage-mode multiplier) in working range of tens of MHz.