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Open AccessArticle

Design of Dual-Mode Local Oscillators Using CMOS Technology for Motion Detection Sensors

Microwave Embedded Circuit & System (MECAS) Lab., School of Electrical Engineering, Chung-Ang University, 84 Heukseok-ro, Dongjack-gu, Seoul 06974, Korea
Integrated Radar Lab., Department of Electronic Engineering, KwangWoon University, 20 Gwangun-ro, Nowon-gu, Seoul 01897, Korea
Author to whom correspondence should be addressed.
Sensors 2018, 18(4), 1057;
Received: 13 February 2018 / Revised: 22 March 2018 / Accepted: 31 March 2018 / Published: 1 April 2018
(This article belongs to the Special Issue Sensors for Microwave Imaging and Detection)
Recently, studies have been actively carried out to implement motion detecting sensors by applying radar techniques. Doppler radar or frequency-modulated continuous wave (FMCW) radar are mainly used, but each type has drawbacks. In Doppler radar, no signal is detected when the movement is stopped. Also, FMCW radar cannot function when the detection object is near the sensor. Therefore, by implementing a single continuous wave (CW) radar for operating in dual-mode, the disadvantages in each mode can be compensated for. In this paper, a dual mode local oscillator (LO) is proposed that makes a CW radar operate as a Doppler or FMCW radar. To make the dual-mode LO, a method that controls the division ratio of the phase locked loop (PLL) is used. To support both radar mode easily, the proposed LO is implemented by adding a frequency sweep generator (FSG) block to a fractional-N PLL. The operation mode of the LO is determined by according to whether this block is operating or not. Since most radar sensors are used in conjunction with microcontroller units (MCUs), the proposed architecture is capable of dual-mode operation by changing only the input control code. In addition, all components such as VCO, LDO, and loop filter are integrated into the chip, so complexity and interface issues can be solved when implementing radar sensors. Thus, the proposed dual-mode LO is suitable as a radar sensor. View Full-Text
Keywords: CMOS; dual-mode; local oscillator (LO); FMCW radar; motion detection; sensor CMOS; dual-mode; local oscillator (LO); FMCW radar; motion detection; sensor
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Ha, K.-W.; Lee, J.-Y.; Kim, J.-G.; Baek, D. Design of Dual-Mode Local Oscillators Using CMOS Technology for Motion Detection Sensors. Sensors 2018, 18, 1057.

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