MEMS Oscillator를 탑재한 우주발사체용 위성항법수신기 성능 향상

학위논문(박사) -- 서울대학교대학원 : 공과대학 기계항공공학부, 2021.8. 박찬국.In this dissertation, the environmental and performance results of TCXO (temperature controlled crystal oscillator) and MEMS (micro electro mechanical system) oscillator are presented. The test results for each oscillator are compared, and based on the test results for the GNSS receiver to which each oscillator is applied, the replaceability of TCXO with MEMS oscillator is discussed. TCXO is a component that supplies a fixed and stable reference frequency by using a quartz crystal with a piezo electric effect, and it has low phase noise, high Q factor fitted for a resonator. The TCXO is widely used in precise clock and timing equipment as well as GNSS receivers. Through many temperature tests during development, the high level of frequency stability over temperature can be achieved by the surrounding compensation circuit. MEMS oscillator drastically reduced its size and weight by introducing micro scale manufacturing and packaging technology and uses silicon as a resonator. This reduction in size and weight makes MEMS oscillator robust under physical stress such as vibration and shock. However, silicon, which is used as a resonator of MEMS oscillator, has lower frequency stability over temperature compared to a quartz crystal, and relatively high phase noise occurs as the complex compensation circuit is required. Despite its advantages, the MEMS oscillator has not been widely used so far due to the tendency to use existing TCXOs. Electronic devices in space launch vehicles experience significant vibration, acceleration, and shock at the flight events such as lift-off, engine shutdown, stage, and pairing separation. And the performance tests under these physical stresses to verify operability should be conducted. In the pyrotechnic shock test, the GNSS receiver equipped with TCXO as a reference oscillator cannot maintain signal tracking, making the position fix fail. This phenomenon was caused by a sudden change in frequency output of TCXO due to the shock, and to address this issue, a MEMS oscillator, which is known to be robust in harsh environmental and stress conditions, was chosen to be utilized as a reference frequency oscillator instead of TCXO. To use the MEMS oscillator as a reference frequency of a GNSS receiver, the pyrotechnic shock, vibration, and temperature test for the MEMS oscillator itself were performed before assemble the GNSS receiver. In order to check the behavior of the GNSS receiver under the reference frequency change, the test using a signal generator, which simulates the reference frequency change without physical shock, was performed. After the test for the MEMS oscillator itself, the test of the GNSS receiver with the MEMS oscillator was conducted. The GNSS receiver can maintain signal tracking and calculate position normally under the pyrotechnic shock test, and the vibration and temperature tests are done without any issues. In environmental and performance tests, there are no problems due to the high phase noise of the MEMS oscillator, and the navigation accuracy was not much different from the existing GNSS receiver with TCXO.본 학위논문에서는 온도보상 수정발진기와 멤스 발진기에 대한 환경시험 및 성능시험 결과를 제시한다. 또한 각각을 탑재한 위성항법수신기에 대한 검증시험을 통해 위성항법수신기에 널리 사용되고 있는 온도보상 수정발진기를 물리적인 충격에 강인한 멤스 발진기로 대체하고자 한다. 온도보상 수정발진기는 압전성질을 지닌 쿼츠를 이용하여 안정적이고 정확한 주파수를 출력하는 부품으로 위상잡음과 손 실이 작아 기준주파수로 적합하다. 온도보상 수정발진기는 이미 정밀시계와 시각장치에 많이 이용되고 있으며, 위성항법수신기에도 널리 사용되고 있다. 단순한 수정진동자는 주변 온도에 민감하게 반응하지만 온도보상 수정발진기는 주변 온도를 측정하는 보상회로가 삽입되어 높은 온도 안정성을 보인다. 멤스발진기는 멤스 기술과 반도체 생산 기술에서 파생된 제조 기술을 바탕으로 온도보상 수정발진기와 비교해서 크기와 무게를 크게 줄였다. 크기가 작아짐에 따라 물리적인 충격과 진동에 강하나 출시 초기에는 높은 위상잡음과 온도변화에 의해 주파수 안정성이 낮아 제한적인 용도에만 사용되어 왔다. 최근 반도체 제작기술의 발달로 멤스 발진기도 온도보상 수정발진기 수준의 잡음 성능을 보이며, 시스템과의 일체화가 더욱 쉬워 응용분야가 넓어지고 있다. 우주발사체의 전자탑재물은 엔진 점화 혹은 페어링 분리와 같은 이벤트가 있을 때마다 강한 진동, 가속도 및 충격을 겪는다. 따라서 전자탑재물 제작시 온도, 진동, 가속도 및 충격과 같은 환경시험 을 수행하는데 온도보상 수정발진기를 탑재한 위성항법수신기가 파이로 충격시험시 항법신호를 놓치는 놓치는 문제가 발생하였다. 이 현상은 위성항법수신기에 탑재된 온도보상 수정발진기의 출력주파수가 충격에 의해 급격히 변하였기 때문이며 이를 위해서 여러 종류의 온도보상 수정발진기를 시험해보았으나 해결이 어려웠다. 멤스 발진기의 위성항법수신기 적용가능성을 확인하기 위해 먼저 파이로 충격환경 하에서 기존 수신기 추적루프에 대한 분석을 제시한다. 그리고 멤스 발진기에 대해 기존에 수행했던 온도, 진동 및 파이로 충격시험을 수행하고 온도보상 수정발진기와 주파수 출력을 비교하였다. 물리적인 환경인 진동과 파이로 충격 이외에 온도에 대해서도 멤스 발진기는 온도보상 수정발진기에 비해 좋은 주파수 안정성을 보였다. 멤스 발진기 자체의 환경시험 이후 위성항법수신기에 탑재하여 동일한 환경에서의 동작 성능을 확인하였고, 온도보상 수정발진기가 탑재된 기존의 위성항법수신기와 비교하여 성능차이가 없었으며 파이로 충격시험에서는 항법신호를 놓치지 않고 연속적인 항법을 수행하였다. 앞서 수행된 시험을 바탕으로 멤스 발진기를 위성항법수신기에 탑재하는데는 문제가 없음이 확인되어 온도보상 수정발진기를 대체할 수 있을 것으로 판단된다.Chapter 1 Introduction . 1 1.1 Motivation and Background 1 1.2 Objectives and Contributions . 4 1.3 Organization of the Dissertation . 5 Chapter 2 Oscillators for Timing Source 6 2.1 Barkhausen Criterion 7 2.2 TCXO . 9 2.2.1 TCXO Fundamentals . 10 2.2.2 TCXO Oscillator model 14 2.2.3 Pierce Oscillator Design Example . 19 2.2.4 TCXO in GNSS receivers . 23 2.3 MEMS Oscillator . 29 2.3.1 Electrostatic MEMS Oscillator model 33 Chapter 3 Environmental Test Results of Oscillators . 41 3.1 Oscillator Behavior under Environmental Stress . 43 3.1.1 Vibration and Acceleration Sensitivity 44 3.1.2 Temperature Sensitivity . 49 3.1.3 Pyrotechnic Shock . 56 3.2 Frequency Stability during the Temperature Test . 60 3.3 Frequency Stability during the Vibration Test 64 3.4 Frequency Stability in Pyrotechnic Shock Test 70 Chapter 4 Simulation with GNSS Receiver under Reference Frequency Change . 74 4.1 Tracking Loop of GNSS Receiver 75 4.2 GNSS Receiver Operation under the Change of Reference Frequency 86 4.3 False Frequency Lock 96 Chapter 5 Environmental Test Results of GNSS Receiver . 103 5.1 Navigation Performance during the Temperature Test . 105 5.2 Navigation Performance during the Vibration Test 108 5.3 Navigation Performance during the Pyrotechnic Shock Test 111 Chapter 6 Conclusion 115 Bibliography 117박

Analog Temperature Control Circuit for a Thin-Film Piezoelectric-on-Substrate Microelectromechanical Systems Oscillator

The objective and motivation for this project is to design a low-power, low-noise oven-control circuit to optimize the stability of a MEMS oscillator. MEMS oscillators can be fabricated using conventional semiconductor manufacturing methods and can often be assembled in packages smaller than those of traditional crystal oscillators. However, one of their largest disadvantages currently is their high temperature coefficient of frequency (TCF), causing MEMS oscillators to be especially sensitive to temperature changes. Hence, this project focuses on designing a printed circuit board that will allow the user to manually tune a current passing through a resonator wire-bonded to the board to elevate the resonator temperature. This will ensure that the device\u27s resonance frequency stays largely constant and that the oscillator provides a very stable signal

RF MEMS reference oscillators platform for wireless communications

A complete platform for RF MEMS reference oscillator is built to replace bulky quartz from mobile devices, thus reducing size and cost. The design targets LTE transceivers. A low phase noise 76.8 MHz reference oscillator is designed using material temperature compensated AlN-on-silicon resonator. The thesis proposes a system combining piezoelectric resonator with low loading CMOS cross coupled series resonance oscillator to reach state-of-the-art LTE phase noise specifications. The designed resonator is a two port fundamental width extensional mode resonator. The resonator characterized by high unloaded quality factor in vacuum is designed with low temperature coefficient of frequency (TCF) using as compensation material which enhances the TCF from - 3000 ppm to 105 ppm across temperature ranges of -40˚C to 85˚C. By using a series resonant CMOS oscillator, phase noise of -123 dBc/Hz at 1 kHz, and -162 dBc/Hz at 1MHz offset is achieved. The oscillator’s integrated RMS jitter is 106 fs (10 kHz–20 MHz), consuming 850 μA, with startup time is 250μs, achieving a Figure-of-merit (FOM) of 216 dB. Electronic frequency compensation is presented to further enhance the frequency stability of the oscillator. Initial frequency offset of 8000 ppm and temperature drift errors are combined and further addressed electronically. A simple digital compensation circuitry generates a compensation word as an input to 21 bit MASH 1 -1-1 sigma delta modulator incorporated in RF LTE fractional N-PLL for frequency compensation. Temperature is sensed using low power BJT band-gap front end circuitry with 12 bit temperature to digital converter characterized by a resolution of 0.075˚C. The smart temperature sensor consumes only 4.6 μA. 700 MHz band LTE signal proved to have the stringent phase noise and frequency resolution specifications among all LTE bands. For this band, the achieved jitter value is 1.29 ps and the output frequency stability is 0.5 ppm over temperature ranges from -40˚C to 85˚C. The system is built on 32nm CMOS technology using 1.8V IO device

Harnessing nature's timekeeper: a history of the piezoelectric quartz crystal technological community (1880-1959)

In 1880, French brothers Jacques and Pierre Curie discovered the phenomenon of piezoelectricity in naturally occurring quartz crystal, sometimes referred to as 'nature's timekeeper.' By 1959, tens of millions of devices that exploited quartz crystal's piezoelectric character were being used in the technologies of radio, telephony, and electronic timekeeping. This dissertation analyzes the rapid rise of quartz crystal technology in the United States by looking at the growth of its knowledge base as reflected primarily in patents and journal articles. The major finding of this analysis is that the rise of quartz crystal technology cannot be fully understood by looking only at individuals, institutions, and technological factors. Rather, this work posits that the concept of technological community is indispensible in explaining rapid technological growth and diffusion that would otherwise seem inexplicable. In the late 1920s, and again in the early 1940s, the knowledge base of quartz crystal technology experienced exponential growth, partly due to U.S. government patronage and enlightened regulation. However, as this study shows, quartz crystal engineers, scientists, and entrepreneurs could not have mobilized as quickly and effectively as they did unless a vibrant technological community already existed. Furthermore, the United States' ability to support such a thriving community depended in part on an early 20th century American culture that displayed an unmatched enthusiasm for democratic communications media, most especially broadcast radio and universal telephone service. Archival records, professional journal articles, government reports, manufacturer catalogs, and U.S. patents have been used to document this history of the quartz crystal technological community. This dissertation contributes to the literature on technological communities and their role in facilitating technological and ecomonic growth by showing that though such communities often form spontaneously, their growth may be nurtured and stimulated through enlightened government regulation. As such, this dissertation should be of interest to scholars in the fields of history of technology, business history, management studies, and public policy.Ph.D.Committee Chair: Usselman, Steven; Committee Member: Ceccagnoli, Marco; Committee Member: Giebelhaus, August; Committee Member: Hunt, William; Committee Member: Krige, Joh

RF Electronics: design and simulation

[Extract] The material presented in this book evolved from teaching analogue electronics courses at James Cook University over many years. When I started teaching electronics design, computer simulation tools were non-existent and most of the design optimisation was done by replacing components in hardware. It was a big step forward when EESOF became available in the mid 1980's. The computer simulation tools have progressed enormously since then. Early in my career, I was given the following advice for designing electronic circuits. "Get the circuit to work and then start taking components out. Put back the one that stops the circuit from working." This is a silly statement, since in a proper design removing any component will stop if from working, but it does illustrate the goal of any designer: Design a circuit that will work first time, according to specification. It must do so reliably and at as low a cost as possible. Since labour is expensive, the circuits also should not require any adjustments after manufacture in order that they meet the specifications

Performance Analysis of MEMS Based Oscillator for High Frequency Wireless Communication Systems

The frequency oscillator is a basic component found in many electrical, electronic, and communications circuits and systems. Oscillators come in a variety of shapes and sizes, depending on the frequency range employed in a given application. Some applications need oscillators that generate low frequencies and other applications need oscillators that generate extremely high and high frequencies. As a result of the expansion and speed of modern technologies, new oscillators appeared that operating at extremely high frequencies. Most wireless communication systems are constrained in their performance by the accuracy and stability of the reference frequency. Because of its compatibility with silicon, micro-electro-mechanical system (MEMS) is the preferred technology for circuit integration and power reduction. MEMS are a rapidly evolving area of advanced microelectronics. The integration of electrical and mechanical components at the micro size is referred to as a MEMS. MEMS based oscillators have demonstrated tremendous high frequency application potential in recent years. This is owing to their great characteristics such as small size, integration of CMOS IC technology, high frequency-quality factor product, low power consumption, and cheap batch manufacturing cost. This paper's primary objective is to describe the performance of MEMS oscillator technology in high-frequency applications, as well as to discuss the challenges of developing a new MEMS oscillator capable of operating at gigahertz frequencies

Evolution of timekeeping from water clock to quartz clock -- the curious case of the Bulova ACCUTRON 214 the first transistorized wristwatch

The technological discoveries and developments since dawn of civilization that resulted in the modern wristwatch are linked to the evolution of Science itself. A history of over 6000 years filled with amazing technical prowess since the emergence of the first cities in Mesopotamia established by the \v{S}umer civilization. Usage of gears for timekeeping has its origin in the Islamic Golden Age about 1000 years ago. Although gears have been known for over 2000 years such as found in the Antikythera Mechanism. Only in the seventeenth century springs started to be used in clock making. In the eighteenth century the amazing \textit{Tourbillon} was designed and built to increase clock accuracy. In the nineteenth century the tuning fork was used for the first time as timebase. Wristwatches started to become popular in the beginning of the twentieth century. Later in the second half of the twentieth century the first electronic wristwatch was designed and produced, which brings us to the curious case of the Bulova \textit{ACCUTRON} caliber 214 the first transistorized wristwatch, another marvel of technological innovation and craftsmanship whose operation is frequently misunderstood. In this paper the historical evolution of timekeeping is presented. The goal is to show the early connection between Science and Engineering in the development of timekeeping devices. This linked development only became common along the twentieth century and beyond.Comment: 18 pages, 9 figure