Seong-Sik Myoung

Bandwidth-Compensation Method for Miniaturized Parallel Coupled-Line Filters

This paper proposes a bandwidth-compensation method for miniaturized filters based on short-ended parallel coupled lines. Capacitive loading of such coupled lines is a relatively simple means of reducing the line lengths. In this study, a method is developed that predicts exactly the degree of reduction in the fractional bandwidth due to miniaturization. Using this method, the fractional bandwidth of the prototype coupled line filter can be adjusted, enabling miniaturized filters to maintain the targeted fractional bandwidth. The proposed bandwidth-compensation method applies for any type of filters with coupled lines realized with various transmission lines, with uniform or nonuniform line lengths. Experimental results are also presented that verify the validity of the method.

Mismatch Detection and Compensation Method for the LINC System Using a Closed-Form Expression

This paper proposes a simple and straightforward path mismatch detection method with a closed-form expression for linear amplification with nonlinear components (LINC) system implementation. In this work, a test vector signal set with three phase differences and one amplitude difference is employed to detect the amplitude and phase mismatches at the same time. The proposed method can predict the exact mismatch value without any iterations, because the mismatch value has a unique solution with a closed-form expression with the proposed test signal set. Moreover, the sensitivity of the proposed method to the measurement noise is also analyzed for practical implementation of LINC system. The LINC system is realized with the proposed mismatch detection method and the performance is evaluated with a IEEE 802.16 WiMAX signal, which has 7 MHz channel bandwidth and 16-QAM. The error vector magnitude (EVM) of -37.4 dB is obtained through performance testing, which meets the performance requirement of -24 dB EVM. The proposed mismatch detection method is validated to improve the LINC system performance.

Effect of Group Delay in RF BPF on Impulse Radio Systems

This paper presents an analysis of the effects of RF filter characteristics on the system performance of an impulse radio. The impulse radio system transmits modulated pulses having very short time duration. Information can be extracted in the receiver side based on the cross-correlation between received and reference pulses. Accordingly, the pulse distortion due to in-band group delay variation can cause serious degradation in system performance. In general, RF band pass filters inevitably cause non-uniform group delays to the signal passing through the filter that are proportional to its skirt characteristic due to its resonance phenomenon. In this work, a small signal scattering parameter, S 21 , which is a frequency domain parameter, and its Fourier transform are utilized to characterize the output pulse waveform under the condition that the input and output ports are matched. The output pulse waveform of the filter is predicted based on the convolution integral between the input pulse and filter transfer function, and the analysis result is compared with previously reported experimental result. The resulting bit error rate performances in a bi-phase modulation and a pulse position modulation based impulse radio system are also calculated. Moreover, improvement of system performance by the pulse shaping method, a potential solution for pulse waveform distortion, is analyzed.

Impact of group delay in RF BPF on impulse radio systems

This paper presents analysis results of the effects of RF filter characteristics on the system performance of impulse radio. The impulse radio system transmits modulated pulses having very short time duration and information can be extracted in receiver side based on cross-correlation between received and transmitted pulses. Accordingly, the pulse distortion due to in-band group delay variation can cause serious system performance degradation. In general, RF bandpass filters inevitably cause group delay difference to the signal passing through the filter which is proportional to its skirt characteristic due to its resonance phenomenon. For time as well as frequency domain analysis, small signal scattering parameter S/sub 21/ and its Fourier transform are used to characterize output pulse waveform under the condition that the input and output ports are matched. The output pulse waveform of the filter is predicted based on convolution integral between input pulse and filter transfer function, and resulting BER (bit error rate) performances in the BPM (bi-phase modulation) and PPM (pulse position modulation) based impulse radio system are calculated.

A Novel 10 GHz Super-Heterodyne Bio-Radar System Based on a Frequency Multiplier and Phase-Locked Loop

This paper presents a novel 10GHz bio-radar system based on a frequency multiplier and phase-locked loop (PLL) for non-contact measurement of heartbeat and respiration rates. In this paper, a 2.5GHz voltage controlled oscillator (VCO) with PLL is employed as a frequency synthesizer, and 10GHz continuous wave (CW) signal is generated by using frequency multiplier from 2.5GHz signal. This paper also presents the noise characteristics of the proposed system, and the analysis result shows that the same signal-to-noise-ratio (SNR) performance can be achieved with the proposed system based on the frequency multiplier compared with the conventional system with identical carrier frequency. The experimental results shows excellent vital-signal measurement up to 100cm without any additional digital signal processing (DSP), thus proving the validity of the proposed system.

Co-planar waveguide filter with ground perforation for ultra-wideband system

In this paper, a compact co-planar waveguide band-pass filter is proposed for ultra-wideband (UWB) communication systems by utilizing perforation in the ground layer. An aperture compensation technique is developed to control the coupling strength, since UWB filters require a strong coupling strength due to its wide bandwidth (> 50%). The coupling strength appears frequency-distributed and its maximum value rapidly rises as the aperture widens. Then, a pair of capacitively loaded line sections is inserted between two identical parallel coupled lines to formulate a new planar band-pass filter with multi-pole band-pass behavior. The predicted and measured results show attractive properties of the proposed filter with a pass-band of 3.1 to 5.0 GHz (50%), |S/sub 11/| < -18 dB, group delay 800 psec, insertion loss < 1 dB, and the size of 9 /spl times/ 9 mm/sup 2/.

A RECONFIGURABLE ACTIVE ARRAY ANTENNA SYSTEM WITH THE FREQUENCY RECONFIGURABLE AMPLIFIERS BASED ON RF MEMS SWITCHES

In this paper, a frequency reconflgurable active array antenna (RAA) system, which can be reconflgurable at three difierent frequency bands, is proposed. The proposed RAA system is designed with a novel frequency reconflgurable front-end ampliflers (RFA) with the simple reconflgurable impedance matching circuits (RMC) with the MEMS switches. With the MEMS switch, the RFA is realized without any performance sacriflce especially linear characteristic. The proposed RAA antenna system is composed of the RMC, RFA with the RMC, 2 £ 2 array of reconflgurable antenna elements (RAE), as well as a reconflguration control board (RCB) for MEMS switch control, and the validity of the proposed RMC, RFA, as well as RAA system which is presented with the experimental results.

Mismatch detection and compensation algorithm with the closed form solution for the LINC system implementation

This paper proposes a path mismatch detection and compensation algorithm with the closed form solution for LInear Amplification with Non-linear Components (LINC) system implementation. The LINC system has a merit of using the high efficient amplifier. However, the performance degradation is extremely sensitive to the path mismatch such as amplitude as well as phase mismatch of transfer functions of two signal paths. In this work, a method with the closed form solution is developed that predicts the exact mismatch value without iterations. The LINC system is realized with the proposed mismatch detection and compensation algorithm. The performance was evaluated using the Orthogonal Frequency Division Modulation (OFDM) signal, which has 7 MHz channel bandwidth. The 20 dB Adjacent Channel Power Ratio (ACPR) improvement was obtained with the proposed detection algorithm.

A miniaturization method of parallel coupled-line filters using lumped capacitors and grounding

This paper proposes a new miniaturization method of the parallel coupled-line filter by using lumped capacitors and grounding. The proposed method can dramatically reduce the size of the resonators in the parallel coupled line filter. In addition to the size reduction, an excellent suppression of spurious harmonic responses, which are inherent in this type of filter, is achieved with improved skirt characteristics. To show the validity of the proposed method a filter, which has a center frequency of 900 MHz and an FBW of 10%, is scaled down to half its original dimension. The measured result shows a high level of agreement with the theory.

Bandwidth Enhanced Miniaturization Method of Parallel Coupled-Line Filter

This paper proposes a bandwidth-compensated miniaturization method of filters based on short-ended parallel coupled lines. Capacitive loading of such coupled lines is a relatively simple means of reducing the line lengths. In this work, a method is developed that predicts exactly the degree of reduction in the fractional bandwidth due to miniaturization. Using this method, the fractional bandwidth of the prototype coupled line filter can be adjusted, enabling miniaturized filters to maintain the targeted fractional bandwidth. The proposed bandwidth-compensation method applies for any type of filters with coupled lines realized with various transmission lines. Experimental results are also presented that verify the validity of the method.