• Journal of Advanced Navigation Technology
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• v.23 no.2
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• pp.134-141
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• 2019

Radar systems are divided into the pulse Doppler (PD) radar and the frequency modulated continuous wave (FMCW) radar depending on the transmission waveform. In particular, the PD radar is advantageous for long-range target detection, and the FMCW radar is suitable for short-range target detection. In this paper, we present design and implementation results for a multi-mode radar signal processor (RSP) that can support both PD and FMCW radar systems to detect unmanned aerial vehicles (UAVs) at short distances as well as long distances. The proposed radar signal processor can be implemented based on Altera Cyclone-IV FPGA with 19,623 logic elements, 9,759 registers, and 25,190,400 memory bits. The logic elements and registers of the proposed radar signal processor are reduced by approximately 43% and 30%, respectively, compared to the sum of logic elements and registers of the conventional PD radar and FMCW radar signal processor.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.6
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• pp.140-146
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• 1989

In many situations, radar targets are embedded in a clutter environment and clutter rejection is required. The clutter is unwanted radar echoes and may arise owing to reflections from ground and weather disturbances and statistical properties of the clutter vary with range and azimuth as well as time. That is, adaptive signal processing is required. In this paper, a clutter suppression algorithm based on the clutter whitening filter (WF) and doppler filter bank(DFB) is described which provides improved performance compared with conventional nonadaptive clutter suppression algorithm that is the cascaded moving target indicator (MTI) and (DFB). The clutter whitening filter algorithm is based on the Burg's maximum entropy method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.2
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• pp.166-176
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• 2000

In this paper, the LEO system signal degradation is mainly due to fading and doppler shift, so that the analysis of the signal degradation and compensation techniques are very important. This paper propose a Kalman filter based two step Automatic Frequency Control(AFC) to combat large and time variant frequency offset in low earth orbit satellite communication systems. The proposed Kalman AFC method estimates a frequency offset in two steps, I. e., coarse and fine estimations, extending the frequency acquisition range to even for than the symbol rate. Furthermore, it can track well a time variation of frequency offset. It is shown that the proposed compensator is able to compensate for doppler shift more than several KHz.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.2
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• pp.125-131
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• 2000

A high resolution Laser Doppler Vibrometer(LDV) developed using electronic fringe counting method. The fringe pattern signal obtained via analog signal processing is divided into two. One was converted to a TTL signal with a ZCD(zero-crossing detector) and then counted to calculate the displacement due to the vibration. The other was directed to the A/D converter to get a high resolution of about $\lambda/320$ with the phase comparison method. The data obtained with the A/D converter was used in the displacement calculation and the result was displayed on a LCD pane. In this study, a Laser Doppler Vibrometer with measurement range of $0.32\mum~129\mum$ and displacement resolution of 2nm, about $\lambda/320$ , was developed. And this LDV can be used to measure the dynamic of microsize devices such as MEMS(Micro Electro-Mechanical Systems) and to diagnose high capacity electric equipment such as circuit breakers and transformers, of which resonant frequencies are changed when they are damaged.

• Korean Journal of Veterinary Research
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• v.45 no.3
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• pp.423-427
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• 2005

Color Doppler imaging (CDI) was carried out to evaluate the anesthetics effect on ophthalmic circulation using CDI-derived resistive index (RI) values. CDI was preformed on 24 dogs, and RI values were calculated for the medial long posterior ciliary artery (mLPCA) and ophthalmic artery (OA) before and after administration of anesthetics. After administration of benoxinate or acepromazine, a significant change of the mLPCA RI was not found. But, a significant decrease of the RI following ketamine (p < 0.001) or xylazine (p < 0.01) administration could be observed as compared with the self-control. Mean RI value of OA also showed this same trend. Intraocular pressure was significantly decrease following benoxinate (p < 0.01), acepromazine (p < 0.01), and xylazine (p < 0.001) administration within normal range. The results suggest that some anesthetics influence on ophthalmic vascular resistance. Therefore, chemical restraint was carefully used in clinical application of CDI-derived RI measurement. Particularly, benoxinate and acepromazine is useful chemical restraint without a change of the ophthalmic vascular resistance.

• Proceedings of the KOSOMBE Conference
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• v.1993 no.11
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• pp.51-54
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• 1993

The purpose of this research is to investigate the relationship between the blood flow and autonomic nervous system which regulates the circulation system. After the oral glucose tolerance test(GTT) the velocity changes of the blood flow were measured from the normal, hyperglycemia and diabetic neuropathy using the laser doppler. The FFT analyses showed that the spectrums were concentrated around the particular bands(0.02-0.166Hz, 0.8-1.1Hz) for the normal, while almost uniform distribution of the spectrums was observed for the abnormal. The blood glucose affects the compliance of the blood vessels and viscosity and finally causes the resistance problem in the blood vessels. An index PG was introduced, which was determined by the ratio of the change or the integral power spectrum in the range between 0.02 and 0.166Hz to change of the blood glucose before and after GTT. The index shows 1.0. 0.3 and 0.1 for the normal, hyperglycemia and diabetic neuropathy, respectively. As a conclusion, this spectrum analysis shows the potential of checking the progress or the diabetic, also car be used to evaluate the vasomotion which are regulated by the autonomic nervous system.

• Restorative Dentistry and Endodontics
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• v.24 no.4
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• pp.560-569
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• 1999

Blood supply rather than nerve supply implies pulp vitality. To evaluate pulp vitality clinically, electric pulp test and thermal test which are based on sensory nerve response have been used in addition to many auxiliary data such as past dental history, visual inspection, radiographic examination, percussion, palpation and transillumination test. However, reactivity of the nerves to the stimulation is not synonymous with normalcy. Therefore measurement of pulpal blood flow using a laser Doppler flowmeter became a new trial to test the pulp vitality. The purpose of the present study was to evaluate normal pulpal blood flow level of maxillary teeth in adult to provide a guideline in determining the vitality of dental pulp. Pulpal blood flow was measured in maxillary central and lateral incisors, canines, first and second premolars and first molars of seventy nine adults of 22 - 30 years old using a laser Doppler flowmeter (PeriFlux 4001, Perimed Co., Stockholm, Sweden, 780 nm infrared laser, 1mW). For directly-made splints, silicone rubber impressions were taken directly from the mouth. For indirectly-made splints, alginate impressions were taken from the mouth and stone cast were made. After making depressions on the buccal surfaces of the cast teeth to indicate the hole positions, second impressions with vinyl polysyloxane putty were taken from the cast. Holes for the laser probes were made at the putty impressions 4mm above the gingival level. Laser probe (PF416 dental probe, 1.5mm) was inserted in the prepared hole and the splint was set in the mouth. After 10 minutes of patient relaxing, pulpal blood flow was recorded for 5 minutes on each tooth. The recorded flow was saved in the computer and calculated with a software 'Perisoft' version 5.1. Pulpal blood flow was also recorded in six teeth of five individuals with no response to electric pulp test and cold test, with periapical radiolucency, or with history of root canal treatment to compare with nonvital teeth. The difference between the mean flow values of each group of teeth were analyzed using one-way ANOVA and Duncan's Multiple Range test. The results were as follows: 1. The average pulpal blood flow values of all the tested teeth of each location were between 9 - 16 Perfusion Unit. Pulpal blood flow value was highest in maxillary lateral incisors, followed by first premolars, second premolars, canines, central incisors, and then first molars (p<0.01). 2. In six anterior teeth, indirectly-made splint group showed higher pulpal blood flow values than directly-made splint group (p<0.01). In posterior teeth, however, there was no significant flow value difference between directly-made splint group and indirectly-made splint one (p>0.05). 3. Teeth with vital pulps showed higher signal values than teeth with nonvital pulps (p<0.01), and the flow photographs showed heartbeat-synchronous fluctuations and vasomotions, while those were absent in non vital tooth.

• Korean Journal of Remote Sensing
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• v.10 no.2
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• pp.1-15
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• 1994

Since Seasat SAR mission in 1978, SAR has become one of the most important surface imaging tools in satellite remote sensing SAR achieves high resolution by signal processing synthesizing a larger aperture. Therefore, SAR signal processing along with antenna technology has been centered upon SAR technologies. Thus interpreters of SAR imagery as well as those who involved in signal processing require the knowledge of the principal SAR processing algorithm. Although the conventional range-Doppler approach has been widely adopted by many SAR processors, azimuth compression including the range migration has been problematic. The recent development of the wavenumber domain approace is able to provide high precision SAR focusing algorithm. Compared with the wavenumber domain algorithm derived by applying Born (first) approximation, the transfer function of the conventional range-Doppler algorithm accounts only for the first order approximation of the exact transfer function. The results of a simulation and an actual test using airborne C-band SAR configuration demonstrate the dxcellent performance of the wavenumber domain algorithm.

• ETRI Journal
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• v.36 no.5
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• pp.799-807
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• 2014

In this paper, we design a rake-based cellular radar receiver (CRR) scheme to detect a moving target located in a multipath environment. The modules of Doppler filter banks, threshold level test, and target detection module are newly introduced into the conventional rake receiver so that it can function as a radar system. The proposed CRR tests the Doppler-shift frequency and signal-to-noise ratio of the received signal against predefined threshold levels to determine detection and then calculates target velocities and ranges. The system performance is evaluated in terms of detection probability and the maximum detection range under a Nakagami-n channel that reflects the multipath environment.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.2
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• pp.199-206
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• 2013

In general, radial velocity of a target can be obtained by acquiring doppler frequency shift in case of a doppler radar, or can be obtained by acquiring range rate in case of a pulse radar. Then radial velocity can be converted to tangential velocity using aspect angle or position variation per unit time. These two ways have the same meaning in physically, but result in different uncertainty finally. In this paper, it is described not only the two transformation procedures to calculate tangential velocity from radar measurement data, but also the result of combined uncertainty comparison between these two procedures.