Oscillators – With frequency adjusting means – Variable inductance device
Reexamination Certificate
1999-07-16
2001-02-06
Pascal, Robert (Department: 2817)
Oscillators
With frequency adjusting means
Variable inductance device
C334S071000, C336S130000
Reexamination Certificate
active
06184755
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to inductors. More particularly, the present invention relates to a micromechanical variable inductor and circuits for use therewith.
BACKGROUND OF THE INVENTION
Inductors and variable inductors are useful and/or required circuit elements in a variety of important applications and products. For example, inductors and variable inductors are necessary elements of many RF-wireless products. In particular, they are used for matching and loading low noise amplifiers, power amplifiers and mixers, as well as for providing frequency- selective resonant circuits in variable-frequency oscillators in such RF-wireless products.
In a typical cellular telephone, inductors, and other “passive” components (e.g., capacitors and resistors) may occupy over 90 percent of the circuit-board space, and outnumber active devices by more than ten-to-one. As the functionality of such a telephone continues to be integrated into progressively fewer chips, the passive components that are not easily integrated have come to dominate the board-level design. Thus, it would be desirable to fabricate semiconductor-integrable passive components.
Several difficulties have impeded the development of such semiconductor-integrable passive components. Regarding inductors, important performance parameters for RF applications include the “quality factor,” Q, (i. e., the relative absence of resistive losses) and obtaining a suitably high self-resonant frequency. Unfortunately, a performance improvement in one of such parameters is typically obtained at the expense of the other parameter. For example, increasing the size of an inductor will typically reduce resistive losses, but it will also lower its resonant frequency.
In the prior art, active circuits are typically used to “tune” or vary inductance in integrated circuits. Such an approach has several disadvantages, including degraded phase noise, relatively high power requirements and limited dynamic range.
A prior-art implementation of variable inductor that is described to be useful for silicon-based RF integrated circuit applications has been disclosed by Pehlke, et al in “Extremely High-Q Tunable Inductor for Si-Based RF Integrated Circuit Applications,” 1997 IEEE Int'l Electron Devices Meeting, at 3.4.1-3.4.4., Washington, D.C., Dec. 7-10, 1997. That tunable inductor uses a variable-phase shifter to vary Q and inductance. While reported performance was good, the presence of the phase shifter is undesirable.
SUMMARY OF THE INVENTION
A variable/tunable inductor is disclosed wherein the geometry of the inductor is altered to vary inductance. More particularly, in accordance with the illustrated embodiments and in contrast with the prior art, the present inductors comprise at least two elements that support spatial electromagnetic coupling and means for varying a geometrical relationship thereof. Varying the geometrical relationship between such elements varies the inductance of the inductor.
In one embodiment, a variable inductor in accordance with the present teachings comprises a ground plane, an electrically-conductive planar loop spaced therefrom, and means for varying a geometrical relationship between the ground plane and the loop. In another embodiment, a variable inductor comprises two electrically-conductive planar loops that are spaced from each other and means for varying a geometrical relationship between the two loops.
In the illustrated embodiments, the geometrical relationship that is varied is the spacing between the loop and the ground plane or the spacing between the two loops. In various embodiments, the spacing is varied by creating a differential movement between the relevant elements.
In the illustrated embodiments, such differential movement is generated (1) by restraining the movement of one of the elements or (2) by varying a parameter/property of the two elements such that the elements respond differently to an actuating stimulus. The varied parameter may include, without limitation, element (e.g., loop) thickness, material of fabrication, and structural implementation. In the illustrated embodiments, the actuating stimulus includes temperature, electrostatic force, electromechanical impulsion and magnetic force.
In further embodiments, the present invention comprises resonant circuits incorporating such variable inductors, and oscillators including such resonant circuits.
REFERENCES:
patent: 1608993 (1926-01-01), Pfanstiehl et al.
patent: 1861869 (1932-06-01), Long
patent: 1961783 (1934-06-01), Roder
patent: 2308863 (1943-01-01), Craymer
patent: 2448642 (1948-09-01), Wilburn
patent: 2685070 (1954-07-01), Childs
Gammel et al. “Design, Test and Simulation of Self-Assembled, Micromachined RF Inductors,” SPIE vol. 3680, pp. 581-591, Part of the Symposium on Design, Test and Microfabrication of MEMS and MOEMS, Mar.-Apr. 1999, Paris, France.
Young et al. “A Low-Noise RF Voltage-Controlled Oscillator Using On-Chip High-Q Three-Dimensional Coil Inductor and Micromachined Variable Capacitor,” Tech. Dig., pp. 128-131, Solid State Sensor and Actuator Workshop, Jun. 8-11, 1998, Hilton Head Island, South Carolina.
Fan et al., “Universal MEMS Platforms for Passive RF Components: Suspended Inductors and Variable Capacitors,” IEEE Proc., pp. 29-33, Eleventh Annual Int'l. Conf. MEMS, Jan. 25-29, 1998, Heidelberg, Germany.
“MEMS Technology Pursued for the Development of Micromachined Silicon Variable Inductors and Latching Accelerometers,” Elec. Design, Jun. 23, 1997.
Pehlke et al., “Extremely High-Q Tunable Inductor for Si-Based RF Integrated Circuit Applications,” IEEE Proc., pp. 63-66, Int'l. Electron Devices Meeting, Dec. 7-10, 1997, Washington, D.C.
Barber Bradley P.
Gammel Peter L.
Lubecke Victor M.
Choe Henry
DeMont & Breyer LLC
Lucent Technologies - Inc.
Pascal Robert
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