微磁通閘感測器之交流調變電路設計與量測分析

磁感測器或磁強計(magnetometer)的量測系統有許多皆為低頻及微弱的訊號，因此，需要對這些訊號進行某些形式的調變工作，才能將量測訊號帶離雜訊區，使正確的量測訊號被解析出來。微磁通閘感測器感應訊號經方波相位調變(square wave modulation)後，再經由混波器和移相電路解調變，即可將真實相位訊號解析出來。本論文電路設計能偵測磁通閘感測器或巨磁阻等磁感測器之第一或第二諧波對外磁場之響應，並以數位移相電路調整相位，配合類比諧波偵測電路之運作，整體電路架構可分為數位移相電路、類比諧波偵測電路及交流驅動電路，感應訊號透過類比諧波偵測驅動電路，能使磁感測器的響應轉換為正比於外加磁場的輸出電壓。電路設計採用國家晶片設計中心(CIC)所提供之TSMC 0.18 μm 1P6M CMOS製程技術完成設計，並對晶片電路進行量測與分析，也將晶片電路與磁通閘感測器結合量測，當激發頻率25 kHz及激發電流111 mA，測得焊線式微磁通閘的電壓轉移率為0.744 V/T；使用儀器測定的結果為2.289 V/T，此差異的原因可能是電路放大率過大、或高頻干擾使訊號飽和失真。待這些問題改進後，未來可將驅動電路與感測器之激磁線圈整合在同一顆晶片上，實現系統化晶片 (systems-on-chip，SOC)之磁場感測器。

關鍵字

磁通閘感測器；數位移相電路；調變解調變技術

並列摘要

Most of the measurement of the magnetometer is considered low frequency and weak signals. For this reason, it needs to process some modulation to these signal to extract the correct signal from the noise region. The pick-up signal from the micro fluxgate sensor takes the processes of the square wave modulation, mixer and phase-shift circuit demodulation to obtain real phase signals. The circuit design in this paper can take the first and second harmonic wave response form fluxgate and GMR sensors exposed to the ambient magnetic field, use the digital phase-shift circuit as the main phase tuning mechanism of analogous harmonic wave sensing circuit. The whole structure of circuit include the digital phase-shift circuit, analogous harmonic wave sensing circuit and AC drivering circuit. The pick-up signal in passed to the analog harmonic wave sensing circuit to transform the response of magnetometer into the output voltage proportional to the ambient magnetic field. The circuit design use the fabrication process of TSMC 0.18 μm 1P6M CMOS provided by CIC, and followed by comprehensive measurements and analyses. Moreover, we integrate the circuit chip and the fluxgate sensor to measure the sensing result. The results show that the sensitivity can achieve 0.744 V/T when excitted by 111 mA current at 25 kHz, which is the one-third of the result of 2.289 V/T measured by instruments. This can be attributed to that the amplification ratio is too large or the signal distortion by high frequency. If the problem can be solved, the circuit and be integrated with the sensor on the same chip to realize a SOC magnetic sensor.

並列關鍵字

fluxgate sensor ； digital phase shifter ； modulation and demodulation techniques

參考文獻

[2] Andrea Baschirotto, Enrico Dallago, Massimo Ferri, Piero Malcovati, Andrea Rossini, Giuseppe Venchi, “A 2D micro-fluxgate earth magnetic field measurement systems with fully automated acquisition setup,” Measurement, Volume 43, Issue 1, January 2010, Pages 46-53.

[3] James Lenz, Alan S. Edelstein, "Magnetic Sensors and Their Applications," IEEE Sensors Journal, Vol. 6, No. 3, pp. 631-649 (2006).

[5] P. Ripka and M. Janŏsek, "Advances in magnetic field sensors," IEEE Sensors Journal, vol. 10, pp. 1108-1116 (2010).

[6] D. Robbes, "Highly sensitive magnetometers—a review," Sensors and Actuators A 129, 86–93 (2006).

[7] 台灣區電機電子工業同業公會，http://www.teema.org.tw/industry-information-detail.aspx?infoid=2592

國際替代計量

微磁通閘感測器之交流調變電路設計與量測分析

全文下載

主題瀏覽