Yoo Hwan
Yoo Hwan Kim, Yongin-Si KR
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20100321120 | FRACTIONAL-N FREQUENCY SYNTHESIZER AND METHOD THEREOF - The present relates to a fractional-N frequency synthesizer improving noise characteristics and a method thereof. The fractional-N frequency synthesizer includes a reference oscillator that generates a reference frequency signal; a sigma-delta modulator that generates a desired decimal value based on the reference frequency signal; a divider that divides a voltage controlled oscillation frequency signal; first to M phase/frequency detectors that detect a difference in phase and frequency between the reference frequency signal and the divided voltage controlled oscillation frequency signal; first to M charge pumps that are connected to each of the phase/frequency detectors in series and charges or pumps charge amount according to output signals from each of the phase/frequency detectors; a loop filter that controls the amount of supplied current based on output signals from the charge pumps to filter low-pass frequency components; and a voltage controlled oscillator that is oscillated in response to the output signal from the loop filter and generates voltage controlled oscillation frequency signals. | 12-23-2010 |
20110032011 | AUTO FREQUENCY CALIBRATOR, METHOD THEREOF AND FREQUENCY SYNTHESIZER USING IT - The present invention relates to and auto frequency calibrator, a method thereof, and a frequency synthesizer using it. The auto frequency calibrator includes a capacitor bank selector that is operated as an open loop and compares a frequency signal having integer-divided reference frequency with the reference frequency signal to select a capacitor bank corresponding to an output frequency; and a capacitor bank controller that is operated as a closed loop when the capacitor bank is selected and compares the output voltage corresponding to the output frequency with a preset voltage range to control the capacitor bank selected in the capacitor bank selector. | 02-10-2011 |
Yoo Hwan Kim, Gyeonggi-Do KR
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20130082777 | BIAS CONTROLLING APPARATUS - The present invention includes: a temperature compensation circuit for generating a digital signal corresponding to a temperature of a transistor and outputting a compensation bias current obtained by adding a control current to a reference bias current or by subtracting the control signal from the reference bias current using the generated digital signal; a characteristics compensation circuit for detecting a characteristics error of a mirror transistor connected to the transistor in parallel and for outputting a compensation signal to compensate the characteristics error; and a bias compensation circuit for compensating a bias power applied to the transistor using the compensation bias current and the compensation signal to output the compensated bias power. The present invention is capable of improving the performance of the transistor. | 04-04-2013 |
20130141167 | POWER AMPLIFIER - Disclosed herein is a circuit for preventing an element from being damaged although output impedance of a final transistor is changed in a power amplifier. The power amplifier includes: a power stage amplifying a signal; a transformer connected to an output terminal of the power stage and coupling a signal output from the power stage; and a controller controlling a bias voltage from the power stage according to the coupled signal. Although output impedance is changed, damage to the power amplifier can be prevented. Also, the power amplifier can be automatically controlled to maintain performance thereof by sensing an operational state in which output impedance is normal. | 06-06-2013 |
Yoo Hwan Kim, Suwon KR
Yoo Hwan Kim, Suwon-Si KR
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20150118976 | RADIO FREQUENCY SWITCHING CIRCUIT WITH ADVANCED ISOLATION CHARACTERISTICS - A radio frequency switching circuit may include a first switching circuit unit including first to n | 04-30-2015 |