Reed Parker

A Temperature-Stable Film Bulk Acoustic Wave Oscillator

This letter reports a passively temperature-compensated CMOS oscillator utilizing a film bulk acoustic resonator. The resonator exhibiting an f ldr Q product of 2-4 X 1012 s-1 is composed of molybdenum, aluminum nitride, and a compensation material that has a positive temperature coefficient of Youngs modulus. The 604-MHz oscillator consumes 5.3 mW from a 3.3-V supply and achieves excellent phase noise performances of -102, -130, and -149 dBc/Hz at 1, 10, and 100 kHz carrier offsets, respectively. The oscillators temperature-dependent frequency drift is less than 80 ppm over a temperature range of -35degC to +85degC.

Method of Extracting Unloaded Q Applied Across Different Resonator Technologies

When comparing different resonator technologies, it is essential that fundamental properties such as the unloaded Q be accurately portrayed. Important Figure-of-Merit (FOM) numbers for resonators include operating frequency, coupling coefficient (kt2), Q, and the products - - kt2*Q and f*Q. Three of the five Figures of Merit depend on an accurate evaluation of unloaded Q. Using a new equation for Q (derived from first principles), we can measure both Q and the coupling coefficient for a variety of resonator technologies and compare the relative performance metrics of each technology.

After 60 years: A new formula for computing quality factor is warranted

A new formulation for computing the unloaded quality factor (Q) of a resonator or of any terminated electromagnetic or piezoelectric cavity from its measured S parameters is proposed. This formulation, based on the work of Dicke, and Bode, computes Q at a continuum of frequencies from below the resonant frequency (fs) to above the anti-resonant frequency (fp). Sixty years ago Dicke and Beringer derived a pair of formulations for Q in terms of the measured impedance (Z) and admittance (Y). The new formulation has two important advantages over Dickes formulations: (1) Even for resonators that are free of spurious resonances - whose S-parameters are near ideal -- Dickes Z and Y based formulations yield erroneous Q values over a range of frequencies (called ldquodead zonesrdquo) in the vicinity of the frequencies at which the functions Z and Y are singular (at fp and fs respectively). Since the S parameters of such an ideal resonator do not have any singularities, the new Q formulation provides reliable Q values over the full range of frequencies. (2) For non-ideal resonators exhibiting spurious lateral-mode resonances in certain frequency ranges, both the new and Dicke formulations report Q values that are clearly erroneous since they oscillate from positive to negative. Dicke does not explain why his formulation breaks down in such regions nor have we found such an explanation in the literature. In contrast to this, this work explains why the S parameter based Q formula is invalidated over regions of frequency space in which ln(mag(S)) fluctuates wildly. We show that in such regions that pre-conditioning of the S-parameter data with a Gaussian window average is useful in yielding a meaningful value for Q. We propose that the S parameter based Q formulation, being devoid of ldquodead zonesrdquo should be used as a standard by which piezoelectric resonators fabricated in different technologies e.g. FBAR, SAW, BAW be compared.

An ultra-miniature, low cost single ended to differential filter for ISM band applications

We present a filter for the 2.4 GHz ISM band that has both filtering and balun functionality to deliver a single ended to differential (SE2DE) filter response and 4:1 impedance transformation. We integrate the balun and filter response into a single chip using two FBAR resonators stacked one on top of the other and separated by a thin, low acoustic impedance material. True SE2DE behavior is achieved by dividing the bottom FBAR into two 100 Ohm resonators and hooking them in parallel to present a 50 Ohm impedance to the endpoint. The two 100 Ohm resonators forming the top of the stack are connected in series to present a differential output impedance of 200 Ohms. Since the entire device is not much larger than a single 50 Ohm resonator, the total die size is extremely small (much smaller than a typical FBAR half ladder filter utilizing 4 to 8 resonators).

11E-3 A Thermally Stable CMOS Oscillator Using Temperature Compensated FBAR

This paper presents a passively temperature compensated CMOS oscillator utilizing Film Bulk Acoustic Resonator (FBAR). The resonator exhibiting f-Q product of 2~3times1012 sec-1 is comprised of molybdenum (Mo), aluminum nitride (AlN), and a compensation material that has positive temperature coefficient of Youngs modulus. The 600 MHz oscillator consumes 6.6 mW from a 3.3 V supply and achieves an excellent phase noise performance of -102 dBc/Hz, -132 dBc/Hz, and -151 dBc/Hz at 1 kHz, 10 kHz, and 100 kHz carrier offset, respectively. The oscillators temperature-dependent frequency drift is less than 80 parts per million (ppm) over a temperature range of -35 to +85degC.

Low jitter FBAR based chip scale precision oscillator

We present a FBAR oscillator that operates at 628MHz, achieves low jitter <;50fs and good frequency stability all while fitting in a small package of 1.1 × 0.9 × 0.25 mm3. The chip-scale oscillator employs a feedback circuitry in the encapsulating lid of a FBAR resonator and makes use of a differential Colpitts oscillator design fabricated in 0.6μm CMOS technology. To achieve the frequency precision required for a reference oscillator, we demonstrate the ability to tune the oscillator over 700ppm using a switched capacitor scheme to compensate for manufacturing tolerances. For achieving frequency stability over temperature and packaging stress, the FBAR resonators used in these oscillators employ silicon dioxide layer temperature compensation and a stress relieved structure respectively. The measured integrated jitter (12kHz to 20MHz) for the oscillators with a supply voltage of 3.3V across a wafer is 33fs with a far from carrier phase noise of -170dBc/Hz .The median current draw from the supply is 16.5mA and the output power measured at a 50ohm load using a balun is 0dBm.These oscillators are suitable for co-integration as reference clocks in high speed communication ICs where size and performance are paramount.

Manufacturing and reliability of chip-scale packaged FBAR oscillators

We present a robust, chip-scale packaged FBAR oscillator that is compatible with high volume manufacturing. The oscillators extremely small size (area <; 1 mm2, thickness = 0.23 mm) combined with an SMT-compatible pad design enables integration of the timing function in-package with a companion ASIC. We have measured tens of thousands of oscillators operating at a native frequency of 2.6 GHz and observe mean jitter less than 10 fsec (12 kHz to 20 MHz offset), with many devices better than 8 fsec. The mean phase noise is -158 dBc/Hz at 800 kHz offset and -118 dBc/Hz at 10 kHz offset. The device draws 18 mA at 3.3V, and the phase noise at all frequency offsets remains within 1 dB over the temperature range from -40 to 125°C. Far from carrier noise is set by the power delivered to the resonator. Due to the ability of the resonator to remain linear at high power, far-from-carrier phase noise is as low as -165 dBc/Hz. The sensitivity to acceleration of these oscillators is better than 0.1 ppb/g. Hermeticity tests carried out on the chip-scale package indicate that the oscillators behave with the same level of integrity as our standard FBAR filters. Preliminary studies on aging have determined an upper bound on frequency drift. Including contributions from supply and load sensitivity, temperature, and aging, total frequency drift is less than +/-200 ppm.

Sub-10 fs jitter S-band oscillators and VCOs in a 1×1×0.23 mm3 chip scale package

We present a fourth-design generation Free Running Oscillator and Voltage Controlled Oscillator using integrated bipolar circuitry in the lid wafer with a temperature-compensated FBAR resonator in the base wafer. The goal is to produce a high frequency, low-noise oscillator. Because there are ~15,000 oscillators per wafer, we can develop very sensitive testing procedures to study the oscillator behavior. For example, we have determined our frequency measurement accuracy and precision to be ~ 0.2 parts-per-million (1 σ), and our phase sensitivity floor to be less than -180 dBc/Hz. Measurements on package hermeticity, suggest that the oscillators behave with the same level of integrity as our standard FBAR filters.

Effects of FBAR resonator dissipated power on discrete oscillator phase noise

We present single-ended and balanced configurations of modified Colpitts voltage controlled oscillators utilizing zero drift FBARs that are compatible with high volume manufacturing. These oscillators have been built with resonators spanning frequencies between 384 MHz and 3900 MHz, demonstrating that temperature compensated FBAR is useful over a decade frequency range for oscillator applications. Over the 1 GHz to 2.5 GHz range, we have observed mean jitter less than 10 fsec (integrated over a 12 kHz to 20 MHz offset), with the best devices demonstrating performance of 5.5 fs. The resonator is 27,000 square microns in a .43 × .35 × .23 mm package. The oscillators are designed to support a temperature range from -40 to 85°C. Due to the ability of the resonator to remain linear at dissipated power values up to 25 mW, far-from-carrier phase noise as low as -185 dBc/Hz @ 10 MHz has been achieved.

A 400µW differential FBAR sensor interface IC with digital readout

A low-power sensor interface IC suitable for a differential frequency measurement application is demonstrated. The circuit is used in a FBAR sensor system which includes a sensor and a reference FBAR. The sensor signal is processed and a digital output representing the sensor input is transmitted using a two wire serial interface. The architecture is entirely digital and benefits from scaling to advanced nodes. The IC is implemented in a 130nm CMOS process and consumes 400μW from a 0.75V supply.