This paper reports on the development of a highly stable miniaturized Oven Controlled Crystal Oscillator (OCXO) in the size of 9.7 × 7.5 mm consisting of heater-embedded ceramic package. The embedded heater layer establishes a symmetrical thermal field to achieve good temperature uniformity, which maintains the oven stability and reduce the power consumption. In addition, the SC-cut crystal is utilized for the proposed miniaturized OCXO to further improve the temperature stability, aging, and phase noise. As a result, this 9.7 × 7.5 mm OCXO has achieved temperature stability of ±3 ppb across −40 to 85 °C. Furthermore, we also demonstrated the proposed miniaturized OCXO could be complied with Stratum 3E requirements.

Highly Stable Miniaturized OCXO with Heater-Embedded Ceramic Package

An oscillator includes a resonation element, a first package that houses the resonation element and airtightly sealed, a circuit element that is positioned outside the first package and electrically connected to the resonation element, and a second package that houses the first package and the circuit element and sealed in a depressurized state. In addition, the first package includes a first base having a first recessed portion, and a first lid joined to the first base so as to close an opening of the first recessed portion, and the second package includes a second base having a second recessed portion and a second lid joined to the second base so as to close an opening of the second recessed portion. The circuit element is attached to the first base, and the first base is attached to the second base.

Oscillator, electronic apparatus, and vehicle

Quartz crystal resonators are the key component of various kinds of electronic systems because they provide the reference frequency source of the system running clocks. However, the frequency stability is often affected by the temperature. Therefore, the frequency-temperature ( f-T ) characteristic modeling has been an important research topic in the frequency control field. The classic f-T modeling method omits the system dynamics and may lead to a large frequency compensation error in the case of rapid temperature changing. To deal with this issue, this article proposes a dynamic f-T modeling method based on improved echo state network (ESN), called residual scaled ESN (RSESN). In the proposed method, the residual modeling framework is designed for purposes of good physical understandability and high prediction precision. This framework uses the static polynomial f-T model to depict the approximated data relationship and applies the complicated network model to compensate the detailed dynamic error. To estimate the dynamic errors, one effective dynamic modeling tool, ESN, is introduced to build the dynamic compensation model for f-T characteristic of quartz crystal resonators. For a better fitting performance, the ESN activation limitations are analyzed and the scaled echo states are constructed in the improved ESN model. The modeling and testing results on the real experiment data show that the proposed method can capture the dynamic information effectively and provide better frequency deviation predictions. 

Dynamic Frequency–Temperature Characteristic Modeling for Quartz Crystal Resonator Based on Improved Echo State Network

A temperature compensated oscillator includes a resonator element, an oscillation circuit, and a temperature compensation circuit. Assuming an observation time as T, an MTIE value at 0.1 s<τ≤1 s is 1.3 ns or less, an MTIE value at 1 s<τ≤10 s is 1.3 ns or less, an MTIE value at 10 s<τ≤100 s is 1.8 ns or less, an MTIE value at 100 s<τ≤1000 s is 2.9 ns or less, a TDEV value at 0.1 s<τ≤10 s is 47 ps or less, a TDEV value at 10 s<τ≤100 s is 65 ps or less, and a TDEV value at 100 s<τ≤1000 s is 94 ps or less.

Temperature compensated oscillator and electronic device

This work presents an ultra-miniature oven controlled crystal oscillator (OCXO) using a hermetically sealed ceramic package with the size of $7.0\ \text{mm} \times 5.0\ \text{mm}$ . The oven structure combined within a heater-embedded ceramic package and a low thermal conductivity bonding adhesive provides excellent thermal performance, achieving temperature stability within ±10 ppb across −40 to 95°C. Hermeticity is accomplished with a seam-welded lid to a kovar ring on the ceramic substrate. In addition, a $2.5\ \text{mm} \times 2.0\ \text{mm}$ SC-cut crystal is utilized to further improve the temperature stability, aging, gravity sensitivity, and phase noise performance that can be compliance with Stratum 3E specifications. The proposed ultra-miniature OCXO provides more robust and smaller package alternative for 5G outdoor applications, such as remote radio heads (RRHs), active antenna unit (AAU), and small cells.

A Novel Miniature OCXO Using Hermetically Sealed Ceramic Package

An oven controlled crystal oscillator consisting of heater-embedded ceramic package includes a substrate, a crystal package, a crystal blank, a metal lid, a first IC chip, and a cover lid. The crystal package is mounted on the substrate, and a central bottom of the crystal package is provided with the first IC chip. The crystal blank is mounted in the crystal package and sealed by the metal lid. The crystal package has an embedded heater layer establishing a symmetric thermal field with respect to the first IC chip and the crystal blank. Alternatively, a heater-embedded ceramic carrier substrate is arranged between the first IC chip and the crystal blank to establish a symmetric thermal field with respect to the first IC chip and the crystal blank. The cover lid is combined with the substrate to cover the crystal package and the metal lid.

Oven controlled crystal oscillator consisting of heater-embedded ceramic package

This paper reports on the development of a high-stability miniaturized Oven Controlled Crystal Oscillator (OCXO) in the size of 9.7 mm × 7.5 mm based on the analog oscillation circuit combined with the conventional temperature sensing circuit using a thermistor and related discrete electrical components. The finite element method (FEM) is implemented to optimize the oven stability of the oven structure. As a result, a highly stable oven performance less than ±1°C variation within the ambient temperature ranging from −40 to 85°C is both numerically analyzed and experimentally demonstrated. Consequently, this result implies that the frequency stability of the miniaturized OCXO can achieve less than ±20 ppb using an AT-cut crystal.

Wan-Lin Hsieh

Papers

Oven controlled crystal oscillator consisting of heater-embedded ceramic package

Highly Stable Miniaturized OCXO with Heater-Embedded Ceramic Package

Development of high-stability miniaturized oven controlled crystal oscillator