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Howard C. Luong

Bio: Howard C. Luong is an academic researcher from Hong Kong University of Science and Technology. The author has contributed to research in topics: CMOS & Phase noise. The author has an hindex of 35, co-authored 216 publications receiving 4414 citations. Previous affiliations of Howard C. Luong include University of California, Berkeley & Maxim Integrated.


Papers
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Journal ArticleDOI
TL;DR: In this article, a transformer-feedback voltage-controlled oscillator (TF-VCO) is proposed to achieve low-phase-noise and low-power designs even at a supply below the threshold voltage.
Abstract: A transformer-feedback voltage-controlled oscillator (TF-VCO) is proposed to achieve low-phase-noise and low-power designs even at a supply below the threshold voltage. The advantages of the proposed TF-VCO are described together with its detailed analysis and its cyclo-stationary characteristic. Two prototypes using the proposed TF-VCO techniques are demonstrated in a standard 0.18-/spl mu/m CMOS process. The first design using two single-ended transformers is operated at 1.4 GHz at a 0.35-V supply using PMOS transistors whose threshold voltage is around 0.52 V. The power consumption is 1.46 mW while the measured phase noise is -128.6 dBc/Hz at 1-MHz frequency offset. Using an optimum differential transformer to maximize quality factor and to minimize the chip area, the second design is operated at 3.8 GHz at a 0.5-V supply with power consumption of 570 /spl mu/W and a measured phase noise of -119 dBc/Hz at 1-MHz frequency offset. The figures of merits are comparable or better to that of other state-of-the-art VCO designs operating at much higher supply voltage.

309 citations

Journal ArticleDOI
TL;DR: An ultra-low power embedded CMOS temperature sensor based on serially connected subthreshold MOS operation is implemented in a 0.18 μm CMOS process for passive RFID food monitoring applications, illustrating proper sensing operation for passiveRFID applications.
Abstract: An ultra-low power embedded CMOS temperature sensor based on serially connected subthreshold MOS operation is implemented in a 0.18 μm CMOS process for passive RFID food monitoring applications. Employing serially connected subthreshold MOS as sensing element enables reduced minimum supply voltage for further power reduction, which is of utmost importance in passive RFID applications. Both proportional-to-absolute-temperature (PTAT) and complimentary-to-absolute-temperature (CTAT) signals can be obtained through proper transistor sizing. With the sensor core working under 0.5 V and digital interfacing under 1 V, the sensor dissipates a measured total power of 119 nW at 333 samples/s and achieves an inaccuracy of + 1/-0.8°C from - 10°C to 30°C after calibration. The sensor is embedded inside the fabricated passive UHF RFID tag. Measurement of the sensor performance at the system level is also carried out, illustrating proper sensing operation for passive RFID applications.

192 citations

Journal ArticleDOI
04 Oct 2010
TL;DR: This paper presents a system-on-chip passive RFID tag with an embedded temperature sensor for the EPC Gen-2 protocol in the 900-MHz UHF frequency band and proposes a dual-path clock generator to support both applications with either very accurate link frequency or very low power consumption.
Abstract: This paper presents a system-on-chip passive RFID tag with an embedded temperature sensor for the EPC Gen-2 protocol in the 900-MHz UHF frequency band. A dual-path clock generator is proposed to support both applications with either very accurate link frequency or very low power consumption. On-chip temperature sensing is accomplished with a time-readout scheme to reduce the power consumption. Moreover, a gain-compensation technique is proposed to reduce the temperature sensing error due to process variations by using the same bandgap reference of the tag to generate bias currents for both the current-to-digital converter and the clock generator of the sensor. Also integrated is a 128-bit one-time-programmable (OTP) memory array based on gate-oxide antifuse without extra mask steps. Fabricated in a standard 0.18- μm CMOS process with analog options, the 1.1-mm2 tag chip is bonded onto an antenna using flip-chip technology to realize a complete tag inlay, which is successfully demonstrated and evaluated in real-time wireless communications with commercial RFID readers. The tag inlay achieves a sensitivity of -6 dBm and a sensing inaccuracy of ±0.8° C (3 σ inaccuracy) over operating temperature range from -20°C to 30°C with one-point calibration.

172 citations

Journal ArticleDOI
TL;DR: In this paper, a two-stage CMOS voltage-controlled ring oscillator (VCO) with good phase-noise performance is presented, implemented in a 0.5/spl mu/m CMOS technology and at 2.5-V supply voltage, the VCO has a wide operating frequency range from 661.5 MHz to 1.27 GHz.
Abstract: A 900-MHz two-stage CMOS voltage-controlled ring oscillator (VCO) with good phase-noise performance is presented. Implemented in a 0.5-/spl mu/m CMOS technology and at 2.5-V supply voltage, the VCO has a wide operating frequency range from 661.5 MHz to 1.27 GHz with a peak VCO gain (K/sub VCO/) of -630 MHz/V. At 900 MHz, the phase noise of the VCO is -105.5 dBc/Hz at 600-kHz frequency offset with low power consumption of 15.4 mW. The gain and phase mismatches are less than 0.25 dB and 0.5/spl deg/, respectively, which corresponds to an image rejection of better than 31 dB. The chip area is only 125/spl times/102 /spl mu/m/sup 2/.

170 citations

Journal ArticleDOI
TL;DR: Transformer coupling between two LC tank oscillators is proposed to achieve quadrature outputs with improved performance in terms of high frequency, wide tuning range, low phase noise, and low power as compared to existing active-coupling QVCOs.
Abstract: A 1-V 17-GHz 5-mW quadrature voltage-controlled oscillator (QVCO) based on transformer coupling is presented. Transformer coupling between two LC tank oscillators is proposed to achieve quadrature outputs with improved performance in terms of high frequency, wide tuning range, low phase noise, and low power as compared to existing active-coupling QVCOs. Implemented in a 0.18-mum CMOS process, the proposed QVCO measures a frequency tuning range of 16.5% at 17 GHz and phase noise of -110 dBc/Hz at 1 MHz offset while consuming 5 mA from a 1-V power supply and occupying a core area of 0.37 mm2.

97 citations


Cited by
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Journal ArticleDOI
01 Jul 2021
TL;DR: This work rigorously discusses the fundamental changes required in the core networks of the future, such as the redesign or significant reduction of the transport architecture that serves as a major source of latency for time-sensitive applications.
Abstract: Mobile communications have been undergoing a generational change every ten years or so. However, the time difference between the so-called “G’s” is also decreasing. While fifth-generation (5G) systems are becoming a commercial reality, there is already significant interest in systems beyond 5G, which we refer to as the sixth generation (6G) of wireless systems. In contrast to the already published papers on the topic, we take a top-down approach to 6G. More precisely, we present a holistic discussion of 6G systems beginning with lifestyle and societal changes driving the need for next-generation networks. This is followed by a discussion into the technical requirements needed to enable 6G applications, based on which we dissect key challenges and possibilities for practically realizable system solutions across all layers of the Open Systems Interconnection stack (i.e., from applications to the physical layer). Since many of the 6G applications will need access to an order-of-magnitude more spectrum, utilization of frequencies between 100 GHz and 1 THz becomes of paramount importance. As such, the 6G ecosystem will feature a diverse range of frequency bands, ranging from below 6 GHz up to 1 THz. We comprehensively characterize the limitations that must be overcome to realize working systems in these bands and provide a unique perspective on the physical and higher layer challenges relating to the design of next-generation core networks, new modulation and coding methods, novel multiple-access techniques, antenna arrays, wave propagation, radio frequency transceiver design, and real-time signal processing. We rigorously discuss the fundamental changes required in the core networks of the future, such as the redesign or significant reduction of the transport architecture that serves as a major source of latency for time-sensitive applications. This is in sharp contrast to the present hierarchical network architectures that are not suitable to realize many of the anticipated 6G services. While evaluating the strengths and weaknesses of key candidate 6G technologies, we differentiate what may be practically achievable over the next decade, relative to what is possible in theory. Keeping this in mind, we present concrete research challenges for each of the discussed system aspects, providing inspiration for what follows.

529 citations

Journal ArticleDOI
14 Oct 2014
TL;DR: In this article, various ambient energy harvesting technologies (solar, thermal, wireless, and piezoelectric) are reviewed in detail and their applicability in the development of self-sustaining wireless platforms is discussed.
Abstract: In this paper, various ambient energy-harvesting technologies (solar, thermal, wireless, and piezoelectric) are reviewed in detail and their applicability in the development of self-sustaining wireless platforms is discussed. Specifically, far-field low-power-density energy-harvesting technology is thoroughly investigated and a benchmarking prototype of an embedded microcontroller-enabled sensor platform has been successfully powered by an ambient ultrahigh-frequency (UHF) digital TV signal (512-566 MHz) where a broadcasting antenna is 6.3 km away from the proposed wireless energy-harvesting device. A high-efficiency dual-band ambient energy harvester at 915 MHz and 2.45 GHz and an energy harvester for on-body application at 460 MHz are also presented to verify the capabilities of ambient UHF/RF energy harvesting as an enabling technology for Internet of Things and smart skins applications.

527 citations

01 Jan 2014
TL;DR: A benchmarking prototype of an embedded microcontroller-enabled sensor platform has been successfully powered by an ambient ultrahigh-frequency (UHF) digital TV signal where a broadcasting antenna is 6.3 km away from the proposed wireless energy-harvesting device.
Abstract: In this paper, various ambient energy-harvesting technologies (solar, thermal, wireless, and piezoelectric) are reviewed in detail and their applicability in the development of self-sustaining wireless platforms is discussed. Specifically, far- field low-power-density energy-harvesting technology is thor- oughly investigated and a benchmarking prototype of an embedded microcontroller-enabled sensor platform has been successfully powered by an ambient ultrahigh-frequency (UHF) digital TV signal (512-566 MHz) where a broadcasting antenna is 6.3 km away from the proposed wireless energy-harvesting device. A high-efficiency dual-band ambient energy harvester at 915 MHz and 2.45 GHz and an energy harvester for on-body application at 460 MHz are also presented to verify the capa- bilities of ambient UHF/RF energy harvesting as an enabling technology for Internet of Things and smart skins applications.

470 citations

Patent
29 Jul 2003
TL;DR: In this article, the authors proposed an improved apparatus for a radio communication system having a multiplicity of mobile transceiver units selectively in communication with a plurality of base transceivers which, in turn, communicate with one or more host computers for storage and manipulation of data collected by bar code scanners.
Abstract: Improved apparatus for a radio communication system having a multiplicity of mobile transceiver units selectively in communication with a plurality of base transceiver units which, in turn, communicate with one or more host computers for storage and manipulation of data collected by bar code scanners or other collection means associated with the mobile transceiver units. A network controller and an adapter which has a simulcast and sequential mode provide selective interface between host computers and base transceivers. A scheme for routing data through the communication system is also disclosed wherein the intermediate base stations are organized into an optimal spanning-tree network to control the routing of data to and from the RF terminals and the host computer efficiently and dynamically. Additionally, redundant network and communication protocol is disclosed wherein the network utilizes a polling communication protocol which, under heavy loaded conditions, requires that a roaming terminal wishing to initiate communication must first determine that the channel is truly clear by listing for an entire interpoll gap time. In a further embodiment, a criterion used by the roaming terminals for attaching to a given base station reduces conflicts in the overlapping RF regions of adjacent base stations.

445 citations

Journal ArticleDOI
TL;DR: The analysis of phase noise is extended to encompass a general harmonic oscillator, showing that all phase noise relations previously obtained for specific LC oscillator topologies are special cases of a very general and remarkably simple result.
Abstract: A harmonic oscillator topology displaying an improved phase noise performance is introduced in this paper. Exploiting the advantages yielded by operating the core transistors in class-C, a theoretical 3.9 dB phase noise improvement compared to the standard differential-pair LC-tank oscillator is achieved for the same current consumption. Further benefits derive from the natural rejection of the tail bias current noise, and from the absence of parasitic nodes sensitive to stray capacitances. Closed-form phase-noise equations obtained from a rigorous time-variant circuit analysis are presented, as well as a time-variant study of the stability of the oscillation amplitude, resulting in simple guidelines for a reliable design. Furthermore, the analysis of phase noise is extended to encompass a general harmonic oscillator, showing that all phase noise relations previously obtained for specific LC oscillator topologies are special cases of a very general and remarkably simple result.

438 citations