• ETRI Journal
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• v.32 no.3
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• pp.457-459
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• 2010

A low-power down-sampling mixer in a low-power digital 65 nm CMOS technology is presented. The mixer consumes only 830 ${\mu}W$ at 1.2 V supply voltage by combining an NMOS and a PMOS mixer with cascade transistors at the output. The measured gain is (19 ${\pm}$1 dB) at frequencies between 100 MHz and 3 GHz. An IIP3 of -5.9 dBm is achieved.

• Journal of Positioning, Navigation, and Timing
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• v.3 no.3
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• pp.91-97
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• 2014

A direct RF sampling method refers to a technique that directly converts a passband signal to an intermediate band or a baseband without using a mixer. This method is less complicated than an existing RF receiver because a mixer is not used. It uses digital processing after sampling, and thus can flexibly process signals in a number of bands using software. In this process, it is important to select an appropriate sampling frequency so that a number of signals can be converted to an intermediate band that is easy to process. In this study, going beyond previously studied direct RF sampling frequency selection methods, conditions that need to be additionally considered during receiver design were examined, and the structure of a direct RF sampling receiver that satisfies these conditions was suggested.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.11
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• pp.1280-1287
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• 2012

The 3.2~6.5 GHz wideband YTO(YIG Tuned Oscillator) module is designed, fabricated and measured. To improve the phase noise characteristic of the YTO module, offset PLL(Phase Locked Loop) structure with sampling mixer is applied. This YTO module is composed of sampling mixer, phase detector, loop filter, current driver, and YTO. The phase noise of the fabricated YTO module is measured as -100 dBc/Hz at 10 kHz offset frequency, which approximates the predicted result at the center frequency of 4.5 GHz. This YTO module presents over 10 dB improved phase noise compared to conventional PLL module from operating frequency.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.15 no.2
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• pp.173-180
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• 2017

In this study, air sampling locations in the stack of the Advanced Fuel Science Building (AFSB) at the Korea Atomic Energy Research Institute (KAERI) were assessed according to the ANSI/HPS N13.1-1999 specification. The velocity profile, flow angle and $10{\mu}m$ aerosol particle profile at the cross-section as functions of stack height L and stack diameter D (L/D) were assessed according to the sampling location criteria using COMSOL. The criteria for the velocity profile were found to be met at 5 L/D or more for the height, and the criteria for the average flow angle were met at all locations through this assessment. The criteria for the particle profile were met at 5 L/D and 9 L/D. However, the particle profile at the cross-section of each sampling location was found to be non-uniform. In order to establish uniformity of the particle profile, a static mixer and a perimeter ring were modeled, after which the degrees of effectiveness of these components were compared. Modeling using the static mixer indicated that the sampling locations that met the criteria for the particle profile were 5-10 L/D. When modeling using the perimeter ring, the sampling locations that met the criteria for particle profile were 5 L/D and 7-10 L/D. The criteria for the velocity profile and the average flow angle were also met at the sampling locations that met the criteria for the particle profile. The methodologies used in this study can also be applied during assessments of air sampling locations when monitoring stacks at new nuclear facilities as well as existing nuclear facilities.

• Journal of Advanced Navigation Technology
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• v.4 no.1
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• pp.36-44
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• 2000

A frequency-shifting technique that uses a digital filter in order to interpolate a bandpass-sampled signal at a low-pass position is investigated. The discussion focuses on the derivation of the required digital filter. It is shown that second-order bandpass sampling offers more flexibility than first-order bandpass sampling in the sense of sampling frequency choice. It is also shown that the well-known quadrature-sampling method for frequency-shifting is a special case of the general second-order sampling technique. The advantages of the mixer-free digital quadrature demodulations are increased flexibility for sampling frequency choice and high precision for I/Q component extraction, and this type of modulation can be applied for modern radar signal processing with high performance.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.9
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• pp.9-18
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• 1998

A single RF transceiver chip for an extended GSM handset application was designedm, fabricated and evaluated. A RFIC was fabricated by using silicon BiCMOS process, and then packaged in 80 pin TQFP of $10 {\times} 10 mm^{2}$ in size. As a result, it was achieved guite reasonable integraty and good RF performance at the operation voltage of 3.3V. This paper describes development results of RF receiver section of the RFIC, which includes LNA, down conversion mixer, AGC, switched capacitor filter and down sampling mixer. The test results show that RF receiver section is well operated within frequency range of 925 ~960 MHz, which is defined on the extended GSM specification (E-GSM). The receiver section also reveals moderate power consumption of 67 mA and minimum detectable signal of -105 dBm.

• Journal of electromagnetic engineering and science
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• v.8 no.1
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• pp.17-22
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• 2008

It is presented that sampling rates for behavioral modeling of quasi-memory less nonlinear devices can be far less than the Nyquist rate of the input signal. Although it has been believed that the sampling rate of nonlinear device modeling should be at least the Nyquist rate of the output signal, this paper suggests that far less than the Nyquist rate of the input signal can be applied to the modeling of quasi-memoryless nonlinear devices, such as frequency multipliers. To verify, a QPSK signal at 820 MHz were applied to a frequency tripler, whereby the device can be utilized as an up-converting mixer into 2.46 GHz with the aid of digital predistortion. AM-AM, AM-PM and PM-PM can be successfully measured regardless of sampling rates.

• Journal of Broadcast Engineering
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• v.21 no.5
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• pp.803-815
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• 2016

In this paper, we design a direct radio frequency (RF) sampling receiver for multiband GNSS signals and demonstrate its performance. The direct RF sampling is a technique that does not use an analog mixer, but samples the passband signal directly, and all receiver processes are done in digital domain, whereas the conventional intermediate frequency (IF) receiver samples the IF band signals. In contrast to the IF sampling receiver, the RF sampling receiver is less complex in hardware, reconfigurable, and simultaneously converts multiband signals to digital signals with an analog-to-digital (AD) converter. The reconfigurability and simultaneous reception are very important in military applications where rapid change to other system is needed when a system is jammed by an enemy. For simultaneous reception of multiband signals, the sampling frequency should be selected with caution by considering the carrier frequencies, bandwidths, desired intermediate frequencies, and guard bands. In this paper, we select a sampling frequency and design a direct RF sampling receiver to receive multiband global navigation satellite system (GNSS) signals such as GPS L1, GLONASS G1 and G2 signals. The receiver is implemented with a commercial AD converter and software. The receiver performance is demonstrated by receiving the real signals.

• JSTS:Journal of Semiconductor Technology and Science
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• v.11 no.4
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• pp.256-261
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• 2011

We demonstrate 3-Gb/s wireless link using a 60-GHz receiver front-end fabricated in $0.25-{\mu}m$ SiGe:C bipolar complementary metal oxide semiconductor (BiCMOS) and a mixed-mode quadrature phase-shift keying (QPSK) demodulator fabricated in 60-nm CMOS. The 60-GHz receiver consists of a low-noise amplifier and a down-conversion mixer. It has the peak conversion gain of 16 dB at 62 GHz and the 3-dB intermediate-frequency bandwidth of 6 GHz. The demodulator using 1-bit sampling scheme can demodulate up to 4.8-Gb/s QPSK signals. We achieve successful transmission of 3-Gb/s data in 60 GHz through 2-m wireless link.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.485-490
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• 2004

Sawtooth mixing device used in a non-premixed burner is evaluated for flame stabilization and NO$_{x}$ reduction. Three mixers with different blade angles are tested. Methane is delivered through the fuel jet and air passes through the co-flow annulus. The flame mode changes (attached flame, lifted flame and extinction) against the fuel flow speed are measured, and the stability diagram is drawn. Moreover, by traversing thermocouple and sampling probe in the flame, the distribution of temperature and NO$_{x}$ mole fraction are measured. With the change in blade angle, flame shape, flame stabilization, the distribution of temperature and NO$_{x}$ mole fraction are changed considerably.rably.