• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.10
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• pp.124-129
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• 1990

This paper describes a new method to eliminate some selected harmonics (5,7,11) in PWM waveforms using Walsh and related orthogonal functions. Previous analyses of PWM waveforms are based on the nonlinear equations requiring iterative solution methods which are not practical in real-time systems. In addition, synthesis of low harmonics waveform at high power system is not easy to implement with power electronic hardware. The goal of this paper is to achieve the harmonics elimination in a PWM waveform by replacing the nonlinear equations in Fourier analysis with linear algebraic equations resulting from the use of orthogonal Walsh equation. This paper also describes how to synthesize low ordered harmonic waveforms with practical power electronic hardware. Walsh and Radmacher functions are easily manipulated by Harmuth's array generator, and those algorithms are accurate, computationally efficient and faster than algorithm based on Fourier analysis. In addition, this method is simulated to synthesize periodic PWM waveforms. From the experi-mental results, it is shown that single-phase PWM waveform are identified with the proposed method. And these methods are also extended to three-phase PWM waveforms in this paper.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.37 no.4
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• pp.28-34
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• 2000

In this paper, a continuous-time filter for low voltage and high frequency applications using fully-balanced current integrators is presented. As the balanced structure of integrator circuits, the designed filter has improved noise characteristics and wide dynamic range since even-order harmonics are cancelled and the input signal range is doubled. Using complementary current mirrors, bias circuits are simplified and the cutoff frequency of filters can be controlled easily by a single DC bias current. As a design example, the 3rd-order lowpass Butterworth filter with a leapfrog realization is designed. The designed fully-balanced current-mode filter is simulated and examined by SPICE using 0.65${\mu}{\textrm}{m}$ CMOS n-well process parameters. The simulation results show 50MHz cutoff frequency, 69㏈ dynamic range with 1% total harmonic distortion(THD), and 4㎽ power dissipation with a 3V supply voltage.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.1
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• pp.73-77
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• 2012

In this article, we designed a wide bandpass filter in order to apply microwave reflectometry for KSTAR. The proposed wide bandpass filter consists of a metamaterial structure which is to get a wide band, a lower insertion loss, and a high skirt. This is applied to VCO's output to enhance the linearity. A pass band is 18-28 GHz and the out of pass band is stopped over 20 dB. To confirm of the metamaterial, we suggest a dispersion diagram. The proposed filter in lower band and upper band of pass band is respectively a left handed and right handed characteristics. A group delay is below 0.5 ns.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.9
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• pp.1019-1024
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• 2012

In this paper, a UWB antenna using a SIR(Step Impedance Resonator) that eliminate signal interference at 5 GHz WLAN as the first rejection band and adjust the second rejection band is proposed. Unlike the unit impedance resonator, the second harmonic of SIR is decided according to step impedance. Therefore, To adjust the second rejection band, SIR is applied to UWB antenna. Also, the equivalent circuit of the antenna at first rejection band is presented and the equivalent modeling values of the SIR and the coupling value is obtained. The proposed antenna is satisfied to cover full UWB band with return losses less than -10 dB and has band rejection characteristic in 5 GHz WLAN band. The radiation patterns show +y directivity characteristics in H-plane and the group delay variations are within 1.0 ns.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.5 s.120
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• pp.486-495
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• 2007

In this paper, we present the design procedure of BPF(Band Pass Filter) for the suppression of LO(Local Oscillator) harmonics. The required suppression at given harmonics is the key issues in such a filter design, while the bandwidth and the suppression of the unwanted signals are more important in the conventional RF filter design. In LO filter design the bandwidth is used for the minimization of the insertion loss for the desired signal. In addition, we propose the novel tuning procedure based on Momentum to consider the unknown parasitic effects, which usually are not included in the circuit design step and results in undesirable and frustrating tuning after fabrication.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.6
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• pp.539-546
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• 1999

A new integrated single-stage zero current switched(ZCS) quasi resonant convertedQRC) for the IX)wer f factor correction(PFCl converter is introduced in this paper. The power factor correction can be achieved by t the discontinuous conduction mod$\varepsilon$(DCM) operation of an input current. The proposed converter has the c characteristics of the good IX)wer factor, 10씨 line current harmonics, and tight output regulation. Furthern10re, t the ringing effect due to the output capacitance of the main switch can be eliminated by use of‘ active clamp c circuit. Therefore, the proIX)sed converter is expecttc'(] to be suitable for a compact power converter with a t tightly regulated output voltage requiring a switching frequency of more than several hundrtc'(]s kHz.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.8
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• pp.2968-2974
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• 2010

Nowadays, the PV systems have been focused on the grid connection between the power source and the grid. The PV inverter can be considered as the core of the whole system because of an important role in the grid-interfacing operation. An important issue in the inverter control is the load current regulation. In the literature, Proportional Integral (PI) controller, which is normally used in the current-controlled Voltage Source Inverter (VSI), cannot be a satisfactory controller for an AC system because of the steady-sate error and the poor disturbance rejection, especially in high-frequency range. Compared with conventional PI controller, Proportional Resonant (PR) controller can introduce an infinite gain at the fundamental frequency of the AC source; hence it can achieve the zero steady-state error without requiring the complex transformation and the de-coupling technique. Theoretical analyses of both PI and PR controller are presented and verified by simulation and experiment. Both controller are implemented in a 32-bit fixed-point TMS320F2812 DSP processor and evaluated on a 3kW experimental prototype PV Power Conditioning System (PCS). Simulation and experimental results are shown to verify the controller performances.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.7
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• pp.771-777
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• 2008

In this paper, a frequency doubler using modified time-delay technique is proposed. A voltage controlled delay line (VCDL) in the proposed frequency doubler compensates the group delay time mismatching between input and delayed signal. With the group delay time matching and waveform shaping using the adjustable Schmitt triggers, the unwanted fundamental component($f_0$) and the higher order harmonics such as third and fourth are diminished excellently. In result, only the doubled frequency component($2f_0$) appears dominantly at the output port. The frequency doubler is designed at 1.15 GHz of $f_0$ and fabricated with TSMC $0.18\;{\mu}m$ CMOS process. The measured output power at $2f_0$ is 2.67 dBm when the input power is 0 dBm. The obtained suppression ratio of $f_0,\;3f_0$, and $4f_0$ to $2f_0$ are 43.65, 38.65 and 35.59 dB, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.1 s.116
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• pp.37-43
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• 2007

In this.paper, we introduce design and implementation results of the single balanced diode mixer for European point-to-point microwave radio in order to improve flatness performance. When a resonator such as RF filter is integrated with a mixer, impedance characteristic of 50 ohm is maintained only in RF band, not in LO band resulting deterioration of flatness performance because of LO power variation on the diode. In the paper, we suggest a design method of mixer integrated with image rejection filter and LO harmonic filter to have a better performance of flatness using embedding electrical length between filter and mixer's port. Frequency specification of fabricated mixer is $21.2{\sim}22.6\;GHz$ for RF, $19.32{\sim}20.72\;GHz$ for LO and 1.88 GHz+/-50 MHz for IF, respectively. Measured results show conversion loss of 8.5 dB, flatness of 2 dB, input PldB of 8 dBm, IIP3 of 15 dBm under LO power level of 10 dBm. Return losses of RF, LO and IF port are under -12 dB, -10 dB and -5 dB, respectively. Isolations of LO/RF and LO/IF are 20 dB and 50 dB, respectively.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.7 s.349
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• pp.162-169
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• 2006

A Micorstrip Bandpass Filter Using DBRs for WLAN ($2.3{\sim}2.4GHz$) applications is designed and an EBG structure is employed in the ground plane of the filter to suppress the stopband responses of the filter. The number of DBRs is chosen as two in consideration of low insertion loss and small size of two filter. The center frequency of the filter to be designed is 2.35GHz and its bandwidth is 140MHz. The responses of two kinds of DBR filters (one with EBG and the other without EBG) are calculated and compared with the measurements. The experimental results are in good agreement with the calculations: The bandwidth and insertion loss of the filter with EBG structure are 3.8% and 1.7dB respectively, while those of the filter without EBG structure are 7% and 1.23dB. It is shown that the insertion loss of the filter is increased and its bandwidth is deceased due to the EBG structure. Also the stopband responses of the filters with EBG structures are shown to be much improved compared with those without EBG.