• Title/Summary/Keyword: Single frequency

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A Differential Voltage-controlled Oscillator as a Single-balanced Mixer

  • Oh, Nam-Jin
    • International journal of advanced smart convergence
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    • v.10 no.1
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    • pp.12-23
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    • 2021
  • This paper proposes a low power radio frequency receiver front-end where, in a single stage, single-balanced mixer and voltage-controlled oscillator are stacked on top of low noise amplifier and re-use the dc current to reduce the power consumption. In the proposed topology, the voltage-controlled oscillator itself plays the dual role of oscillator and mixer by exploiting a series inductor-capacitor network. Using a 65 nm complementary metal oxide semiconductor technology, the proposed radio frequency front-end is designed and simulated. Oscillating at around 2.4 GHz frequency band, the voltage-controlled oscillator of the proposed radio frequency front-end achieves the phase noise of -72 dBc/Hz, -93 dBc/Hz, and -113 dBc/Hz at 10KHz, 100KHz, and 1 MHz offset frequency, respectively. The simulated voltage conversion gain is about 25 dB. The double-side band noise figure is -14.2 dB, -8.8 dB, and -7.3 dB at 100 KHz, 1 MHz and 10 MHz offset. The radio frequency front-end consumes only 96 ㎼ dc power from a 1-V supply.

Volumetric Blood Velocity Measurement on Multigate Pulsed Doppler System based on the Single Channel RF Sampling using the Optimized Sampling Factor (최적화된 샘플링 인수를 갖는 단일 채널 RF 샘플링 방식의 다중점 펄스 도플러 시스템을 사용한 혈류 속도분포 측정)

  • 임춘성;민경선
    • Journal of Biomedical Engineering Research
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    • v.19 no.2
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    • pp.143-152
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    • 1998
  • In this paper, we present the performances of a Doppler system using single channel RF(Radio Frequency) sampling. This technique consists of undersampling the ultrasonic blood backscattered RF signal on a single channel. Conventional undersampling method in Doppler imaging system have to use a minimum of two identical parallel demodulation channels to reconstruct the multigate analytic Doppler signal. However, this system suffers from hardware complexity and problem of unbalance(gain and phase) between the channels. In order to reduce these problems, we have realized a multigate pulsed Doppler system using undersampling on a single channel, It requires sampling frequency at $4f_o$(where $f_o$ is the center frequency of the transducer) and 12bits A/D converter. The proposed " single-Channel RF Sampling" method aims to decrease the required sampling frequency proportionally to $4f_o$/(2k+1). To show the influence of the factor k on the measurements, we have compared the velocity profiles obtained in vitro and in vivo for different intersequence delays time (k=0 to 10). We have used a 4MHz center frequency transducer and a Phantom Doppler system with a laminar stationary flow. The axial and volumetric velocity profiles in the vessel have been computed according to factor k and have been compared. The influence of the angle between the ultrasonic beam and the flow axis direction, and the fluid viscosity on the velocity profiles obtained for different values of k factor is presented. For experiment in vivo on the carotid, we have used a data acquisition system with a sampling frequency of 20MHz and a dynamic range of 12bits. We have compared the axial velocity profiles in systole and diastole phase obtained for single channel RF sampling factor.ng factor.

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Pretreatment Characteristics and Specific Methanogenic Activity of Municipal Sewage Sludge by Dual Frequency Sonication (이중주파수 초음파를 이용한 도시하수슬러지의 전처리 특성 및 비메탄활성도에 관한 연구)

  • Jung, Byung-Gil;Jang, Seong-Ho;Sung, Nak-Chang
    • Journal of Environmental Science International
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    • v.16 no.2
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    • pp.211-218
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    • 2007
  • The objectives of this study have been carried out to investigate the solubilization of municipal sewage sludge by single and dual frequency ultrasonic pretreatment, and the methane production characteristics of pretreated sewage sludge by specific methanogenic activity test for sewage sludge reduction. The waste activated sludge was collected from thickened tank of Suyoung sewage treatment plant in Busan city, and its concentration was adjusted to 1.0% total solids. Ultrasonic frequency was varied 15, 20, 15+20 kHz, and acoustic density was used a maximum 176W/L. The dual frequency ultrasonic pretreatment was found to be more effective than single frequency ultrasonic in the solubilization rate and methane production. The $SCOD_{Cr}/TCOD_{Cr}$, rate were 15.2%, 13.9%, 17.0% with single frequency of 15 kH2, 20 kHz, dual frequency of 15+20 kHz, respectively. The application of dual frequency ultrasound for sewage sludge pretreatment can be interest for sewage treatment plants having problems in sludge treatment and disposal.

Advanced SOGI-FLL Scheme Based on Fuzzy Logic for Single-Phase Grid-Connected Converters

  • Park, Jin-Sang;Nguyen, Thanh Hai;Lee, Dong-Choon
    • Journal of Power Electronics
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    • v.14 no.3
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    • pp.598-607
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    • 2014
  • This paper proposes a frequency-locked loop (FLL) scheme for a single-phase grid-connected converter. A second-order generalized integrator (SOGI) based on fuzzy logic (FL) is applied to this converter to achieve precise phase angle detection. The use of this method enables the compensation of the nonlinear characteristic of the frequency error, which is defined in the SOGI scheme as the variation of the central frequency through the self-tuning gain. With the proposed scheme, the performance of the SOGI-FLL is further improved at the grid disturbances, which results in the stable operation of the grid converter under grid voltage sags or frequency variation. The PSIM simulation and experimental results are shown to verify the effectiveness of the proposed method.

Representative Nutrients Contents and Nutritional Adequacy Evaluation of Single-Dish Meal for Middle School Students (일부 지역 중학생 대상 일품요리의 대표영양가 산출 및 영양적정성 평가)

  • Lee, Gisun;Kim, Youngnam
    • Korean Journal of Community Nutrition
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    • v.23 no.2
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    • pp.93-101
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    • 2018
  • Objectives: With the increasing number of single households and so-called Honbab-jok, those who eat alone, people tend to enjoy convenient and simple meals, such as single dish meals. This study was performed to provide data on the energy and nutrient content, and nutritional adequacy of single-dish meal. Methods: From the literature reviews, 61 types of single-dish meals were selected, and divided into 4 groups (steamed rice, noodle, porridge, and sandwich burger), and a further 11 sub-groups (bibimbab, fried rice, topped rice, rolled rice/ warm noodle, cold noodle, seasoned noodle, dukgook/ porridge/, and sandwich, burger). In addition, 382 junior high school students from Gyeonggi, Sejong, Jeonbuk, and Chungnam areas were recruited for the survey. The survey questionnaires were composed of the characteristics, preference, and intake frequency of single-dish meals. The representative energy content (arithmetic mean) of single-dish meals were calculated, and compared with the energy contents of preference and intake frequency-weighted values adjusted. The representative nutrient contents, energy contribution ratio, and INQ (index of nutritional quality) of a single-dish meal were calculated for a nutritional adequacy evaluation. Results: The study subjects considered a single-dish meal as tasty, simple and fast to prepare, inexpensive, nutritious, and no low calorie food. The preference scores of all but 1 sub-group of singledish meals were ${\geq}5.00$ (5.00~5.97), and 1 sub-group (porridge) was 4.67 on a 7-point scale. The intake frequency of 11 sub-groups were 0.31~1.71/week, porridge was the lowest at 0.31 and warm noodles was the highest at 1.71. Fried rice, rolled rice, and warm noodle' intake frequency were ${\geq}1/week$. The representative energy of steamed rice, noodle, sandwich burger were 443, 429, and 428 kcal, respectively, and that of porridge was 264 kcal. Less than 5% differences in the representative energy of 4 groups were observed when adjusted for the preference or intake frequency-weighted values. The energy contribution ratio of macro-nutrients calculations showed that porridge was a high carbohydrate and low fat food, whereas sandwich burger were high fat and low carbohydrate foods. The INQ of calcium and vitamin C were less than 1.0 in all 4 food groups, but the INQ of protein and thiamin were > 1.0 in all 4 single-dish food groups. Conclusions: The representative energy in the 4 groups of single-dish meal was 264~450 kcal, which is a rather low calorie meal, and the energy contribution ratio of macro-nutrients were inadequate. The protein and thiamin levels were sufficient but the calcium and vitamin C levels were insufficient in all 4 groups of a single-dish meal judged by the INQ. The additional intake of fruits and milk dairy products between meals with a single-dish meal, supply of calcium and vitamin C may increase, which will result in an improved nutritional balance.

Selective Extraction of a Single Optical Frequency Component from an Optical Frequency Comb (광 주파수 빗으로부터 단일 광 주파수 성분의 선택적 추출)

  • Han Seb Moon
    • Korean Journal of Optics and Photonics
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    • v.34 no.6
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    • pp.225-234
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    • 2023
  • Mode-locked pulse lasers have a temporal periodicity up over a short period of time. However, in the time-frequency domain, a pulsed laser with temporal periodicity is described as an optical frequency comb with constant frequency spacing. Each frequency component of the optical frequency comb in the frequency domain is then a continuous-wave (CW) laser with hundreds of thousands of single-frequency-component CW lasers in the time domain. This optical frequency comb was developed approximately 20 years ago, enabling the development of the world's most precise atomic clocks and precise transmission of highly stable optical frequency references. In this review, research on the selective extraction of the single-frequency components of optical frequency combs and the control of the frequency components of optical combs is introduced. By presenting the concepts and principles of these optical frequency combs in a tutorial format, we hope to help readers understand the properties of light in the time-frequency domain and develop various applications using optical frequency combs.

Integrity Monitoring for Drone Landing in Urban Area using Single Frequency Based RRAIM

  • Jeong, Hojoon;Kim, Bu-Gyeom;Kee, Changdon
    • Journal of Positioning, Navigation, and Timing
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    • v.11 no.4
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    • pp.317-325
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    • 2022
  • In this paper, we developed a single frequency-based RRAIM to monitor integrity of the UAM landing vertically in urban area with only low-cost single-frequency GPS receiver. Conventional dual-frequency RRAIM eliminates ionospheric delay through a combination of frequencies. In this study, ionospheric delay was directly modeled. Drift error of residual ionospheric delay is modeled using the previously studied result on ionospheric rates of change. To verify the performance of the proposed RRAIM algorithm, a simulation of vertical landing UAM in urban area was conducted. It was assumed that the protection level at the initial position was calculated through SBAS correction data. During vertical landing, integrity monitored by receiver alone without external correction data. In the 60 sec simulation, the protection level of the proposed RRAIM compared to the conventional RRAIM was calculated to be 140% due to the accumulated ionospheric delay error. Nevertheless, it was confirmed that the final vertical protection level meeting the requirements of LPV-200, which cannot be achieved with single frequency GPS receiver alone.

Effects of Consecutive whole Body Vibration Exercise using Heel Raise Posture on Neuromuscular Response during Single-leg Stance (뒤꿈치 들기 자세를 이용한 전신진동 운동이 외발서기 시 근신경 반응에 미치는 영향)

  • Kim, Dae Dong;Lee, Myeounggon;Youm, Changhong
    • Korean Journal of Applied Biomechanics
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    • v.31 no.2
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    • pp.104-112
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    • 2021
  • Objective: This study aimed to analyze the effects of consecutive whole body vibration through heel raise posture on the center of pressure and electromyography of anterior tibial muscle, lateral gastrocnemius and soleus muscles during single-leg stance. Method: The subjects of this study included 30 healthy males in their 20's, with the following inclusion criteria: no history of orthopaedic medical history, no participation in regular exercises, no history of whole body vibration exercise, and right leg being the dominant leg. The experimental procedure involved pretreatment measurement of eye open single-leg stance, application of whole body vibration for 30 seconds, post-treatment measurement (3 measurements in total). Static and dynamic movements have been measured over 2 separate experiments, with 72 hours gap between the experiments. Static movement involved maintaining single-leg heel raise posture for 30 seconds while applying whole body vibration, and dynamic movement involved heel raise (15 repetitions over 30 seconds) while applying whole body vibration. The strength of applied whole body vibration was 35 Hz frequency and 2~4 mm amplitude. Results: As the single-leg posture after static heel raise posture, mediolateral velocity of the center of pressure at post 2 and post 3 were significantly reduced compared to the pre-treatment measurement. In addition, the percentage for reference voluntary contraction in anterior tibial muscle and soleus and median frequency at anterior tibial muscle and lateral gastrocnemius muscle at post 3 were significantly decreased compared to the pre-treatment value. As the single-leg posture after dynamic heel raise posture, the mediolateral 95% edge frequency of the center of pressure and median frequency at anterior tibial muscle, lateral gastrocnemius muscle, and soleus muscle at post 3 were significantly reduced compared to the pre-treatment value. Conclusion: Acute whole body vibration via static and dynamic heel raise posture have positive effect on mediolateral posture control during single-leg stance.

Implementation of Self-frequency Synchronizing Circuit using Single-sideband Up-converter and Image Rejection Mixer (단측파대 상향변환기와 이미지제거 혼합기를 이용한 자기동조회로의 구현)

  • Yeom, Seong-Hyeon;Kim, Tae-Young;Kim, Tae-Hyun;Park, Boem-June
    • Journal of the Korea Institute of Military Science and Technology
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    • v.13 no.6
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    • pp.1058-1063
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    • 2010
  • In this paper, we designed self-frequency synchronizing circuit using image rejection mixer(IRM) and single-sideband(SSB) up-converter which can effectively eliminate the image frequencies occurred in multi-channel super-heterodyne receivers and help us to match inter-channel phase. Also the self-frequency synchronizing circuit simplifies system because there need no extra devices for making intermediate frequency(IF) by creating the local signal within several nanoseconds by means of generating the same frequency of IF signal and modulating radio frequency(RF) signal. We adopt the limiting amplifier for the purpose of protecting the circuit from spurious signals which come from the front end side having wide instantaneous bandwidth characteristics and constantly injecting same level into the input local signal of IRM. The IRM we fabricated has image rejection ratio of 27dB, which is good over 7dB for foreign company's. Also, the SSB up-converter we fabricated has 1dB compression point of 18dBm, which is good over 16dB for foreign company's. And the size is compact about one-forth.