• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.4
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• pp.634-641
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• 2000

A switchable VCO for DECT handset is designed and fabricated. In dual mode radios, a single VCO is desired to operate at two different frequencies to meet the requirement of two mode(Tx, Rx). The three design types of switchable VCO are switched resonator VCO, switched mode VCO and dual band VCO. In this paper, we use the switched resonator VCO type using pin diode switch to change the total amount of capacitance in the tank circuit. At the bias condition of 3 V and 13mA, the output power and phase noise are better than6.5dBm and -104dBc/Hz at 25khz offset from the carrier, respectively , across the operating frequency range. From these results, the fabricated switched VCO is applicable to the DECT handset.

• Journal of electromagnetic engineering and science
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• v.2 no.2
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• pp.117-123
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• 2002

This paper describes the design for the resistive FET mixer with low If for the 4-Ch DBF(Digital Beam Forming) receiver This DBF receiver based on the direct conversion method is generally suitable for high-speed wireless mobile communications. A radio frequency(RF), a local oscillator(LO) and an intermediate frequency(If) considered in this research are 2.09 GHz, 2.08 CHz and 10 MHz, respectively. This mixer is composed of band pass filter, a low pass filter and a DC bias circuit. Super low noise HJ FET of NE3210S01 is considered in design. The RE input power, LO input power and Vcs are used -10 dBm, 6 dBm and -0.4 V, respectively. In the 4-Ch resistive FET mixer, the measured If and harmonic components of 10 MHe, 20 MHz and 2.087 CHz are about -19.2 dBm, -66 dBm and -48 dBm, respectively The If output power observed at each channel of 10 MHz is about -19.2 dBm and it is higher 28.8 dBm than the maximum harmonic component of 2.087 CHz. Each If output spectrum of the 4-Ch is observed almost same value and it shows a good agreement with the prediction.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.4
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• pp.415-425
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• 1997

Although FHSS has many advantages over conventional digital radio communication system, field application has been so far hampered due to its complicated synchronization. In this paper, a new FHSS system is proposed which one FH signal modulated with GMSK and one chip delayed FH signal than former are sent from transmitter, and this is recovered by matching process at a heterodyne correlator in receiver; thus eliminates synchronization as a whole. Through analysis and experiment, we assure that there is possibility in this. The exper- imental result from 915~929 MHz bandwidth with 31 chips is investigated in the environment of AWGN.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.5
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• pp.672-679
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• 1999

This paper describes the design method of active bandpass filters which employ active impedance inverters. Several authors have reported active bandpass filters. However, the functional description of the active blocks in the filters have not been throughly studied. In this paper, the active inverter block of the bandpass filter has is analyzed in the view point of filter design. The designed 3-pole bandwidth filter has its insertion gain of 24 dB at the center frequency of 865 MHz with 75 MHz bandwidth. The noise figure of the active bandpass filter is less than 2.5 dB within its passband.

• Journal of electromagnetic engineering and science
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• v.7 no.2
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• pp.83-90
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• 2007

In this paper, the formulation of the protection ratio based upon a composite fade margin and availability is newly presented for the detailed planning of frequency coordination in the microwave relay system network, and computed results for co-channel and adjacent channel protection ratios are illustrated over an actual system with 6.2 GHz. It is shown that the protection ratio to assure a quality of service can be expressed in terms of the composite fade margin, noise-to-interference ratio, net filter discrimination, and system parameters. In addition, the net filter discrimination, depending upon the transmitter spectrum mask and the overall receiver filter characteristic, has been examined to investigate the effect of the adjacent channel protection ratio caused by the adjacent channel interference. Regarding simulated results for 6.2 GHz, 60 km, 64-QAM, and N/I=6 dB at the bit error rate of $10^{-6}$, composite fade margin and co-channel protection ratio yield 25.14 and 50.3 dB, respectively. Also, the net filter discrimination of 26.5 dB and the adjacent channel protection ratio of 23.8 dB are obtained at the first adjacent channel of 30 MHz. The proposed method provides some merits in view of a comprehensive and practical application with more detailed and various system parameters needed to access the criteria for making the proper frequency coordination.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2028-2030
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• 1999

In this paper, partial discharge(PD) was generated under the two types of needle -plane electrodes in the air. Using a monopole antenna to detect the radiated electromagnetic waves by stream of charge between the electrodes. the progress of partial discharge was studied. To analyze the progress of PD, statistical re-search was introduced. It was executed by personal computer and it can be possible to visualize the progress of PD. The t-test was used for lower voltage applied. The population of background noise spectrum and applied voltage spectrum showed the difference. The new method was introduced to analyze the spectrum. According tho the magnitude of applied voltage, the different statistical methods were used. The results obtained from this work will provide the useful information on partial discharge in time to come.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.4
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• pp.100-109
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• 2005

This paper introduce electromagnetic environmental requirements, test procedures and test results for the Command Telemetry Unit(CTU), which is engineering qualification model for communication satellite in geostationary earth orbit. Also, through debugging of the CTU during the Electro Magnetic Compatibility(EMC) tests, this paper evaluates characteristics of noise generated by the CTU. It is also obtained that better EMC performance can be acquired by improving electrical power converter module of the CTU.

• International Journal of Railway
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• v.4 no.4
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• pp.93-96
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• 2011

The basic element of the EMS suspension is the electromagnet system, which suspends the vehicle without contact by attracting forces to the rails at the guideway. The suspension of a vehicle by attractive magnetic forces is inherently unstable and consequently it is continuously adjusted by the strength of the suspending electromagnet from rail irregularity and bending of the guideway. In order to improve reliable tracking, it needs to get feedback signals without measurement delay time. In this paper the concept of feedback control system with Kalman Filter in EMS is proposed. The input signals in the feedback control system are an air-gap and an acceleration signal. The air-gap signal with noise from the gap sensor is transformed to the filtered air-gap signal y without measurement delay time by using Kalman Filter. The filtered air-gap signal is transformed to a relative velocity and a relative acceleration signal. Then it multiplies these values by gain matrix in order to get the actuator's reference voltage value. The simulation results show that the dynamic responses of the suspension system can be improved by reducing the influence of measurement delay time of air-gap signals.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.5
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• pp.715-722
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• 2000

In this paper, the PLDRO is designed and implemented for X-band. It is comprised of tunable high Q resonator with a varactor diode for frequency tuning, loop filter and a 1/8 prescaler which up to 10GHz. Also, it is implemented a TCXO and a VCO signal into the phase detector and achieved a highly stable signal source. From the measurement, the designed PLDRO has the output power of 2.5dBm at 8GHz and phase noise of -64.33dBc at 10KHz offset from carrier. Its characteristic is 26 dBc. This PLDRO has much better temperature stability.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.1
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• pp.52-60
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• 1997

A 23GHz 2-stage LNA was designed using MPIE numerical analysis and microwave CAD EEsof softwares. The basic circuit was designed by EEsof tools but analyzed more precisely using numerical MPIE tools and modified. The matching sections of the input and output terminals were designed with paralledl coupled filter-type lines, these matching sections perform impedance matching and DC blocking, more over have the advantages of small discontinuities and small errors in the design process. The FET chip is directly attached to the ground metal. The designed LNA gives 15.2dB gain and 2.7dB noise figure. without considering 1.8dB loss of connectors. These results validate our design process and matching schemes and fabrication technologies over the 20GHz frequency range.