Jahyeon Lee

Balun-BPF using magnetically coupled interdigital-loop resonators

In this paper, we proposed the Balun-BPF(band pass filter) using the magnetically coupled resonators. The proposed Balun-BPF is a deformation of the transformer which operates like the ideal Balun in low frequency. The conventional coupled-resonator filter design theory was used for the design of a Balun-BPF. Moreover, the Interdigital-loop resonator was used to miniaturize the Balun-BPF. This Balun-BPF operated in a 2.4∼2.5 GHz band, generally used in the wireless communication. Experimental measurements are also presented to validate the theory and EM simulations.

Compact chip monopole antenna with parasitic patch for GPS applications

A chip monopole antenna with a parasitic patch is proposed for GPS applications. To reduce the dimensions of the antenna, the chip monopole antenna is composed of stacked meander, helix structures, and a parasitic patch. The impedance and radiation characteristics of the antenna are investigated. The measured results show that the proposed antenna, having compact dimensions of 3.6 × 5 × 1.3 mm, has a bandwidth of 60 MHz (1.53–1.59 GHz) and a maximum radiation gain of 0.53 dBi.

A dual-band bandpass filter using dual and triple-mode resonators

A compact microstrip dual-band bandpass filter with a controllable bandwidth for each passband is presented in this paper. Each passband is independently designed using two different dual and triple-mode resonators. The proposed dual-band bandpass filter has five transmission zeros. Two transmission zeros are generated by each dual-mode resonator. An additional transmission zero is generated through input/output port coupling. The dual-band bandpass filter application is designed for a 2.4/5 GHz WLAN. Experimental measurements are presented in order to validate the theory.

Compact dual-mode interdigital-loop resonator and filter application

A novel compact dual-mode resonator is proposed. This proposed dual-mode resonator was composed of the following features: the series capacitance is inserted for miniaturization and its effect was also analyzed, and open stub was applied on symmetric plan for dual-mode behavior. Using this dual-mode resonator, dual-band bandpass filter of 0.2 λg by 0.28 λg (at odd mode resonance) for WLAN application was designed and fabricated providing an excellent verification on the attractive features of the filter, such as compact size and extra transmission zeros without increase order of filter.

An Enhanced Skirt Characteristics Triple-Mode Filter

This paper presents a compact microstrip triple-mode filter with enhanced skirt characteristics. The presented triple-mode filter configuration supports three transmission poles and three transmission zeros within the nearby passband. Two of transmission zeros are generated by a triple-mode resonator itself, and the third one is generated by small cross-couplings between the I/O ports. Each resonance condition and the transmission zero generation conditions are analyzed using an equivalent circuit. The bandpass filter is designed for a 2.4 GHz WLAN. The filter was fabricated with a relative dielectic constant of 3.5 and a thickness of 0.76 mm. The fabricated filter has a small size (7.9 mm×7.2 mm, i.e., 0.107λg×0.098λg, where λg is guided wavelength at a center frequency) and shows high performing skirt characteristics.

A Method for Improving Stopband Characteristics of a Dual-Band Filter

This paper presents a simple and effective method for improving stopband rejection characteristics of previously studied dual-band filters. Small electric couplings were applied to the symmetrically positioned shunt resonators, which di-vided each transmission zero into two transmission zeros without any effect on passbands. We were able to achieve improved stopband rejection characteristics by these additional transmission zeros. For the filter application, we de-signed a dual-band filter with improved stopband characteristics using microstrip quasi-lumped elements. The electric couplings that control the location of transmission zeros are controlled by the distance between symmetric open stubs of the filter. The filter was fabricated with a relative dielectric constant of 3.5 and a thickness of 0.76 mm. The fabri-cated filter has a small size (14.6×13.2×0.76 mm) and a low insertion loss when compared with conventional filters. Key words: Dual-Band Filter, Electric-Coupling, Quasi-Lumped Elements, Transmission Zero.

A Filter Synthesis Method for Multi-Band Filter Design

In this paper, we presented a new LC prototype synthesis method for the multi-band filter. For synthesis a multi-band filter with the required frequency response, we proposed the diagram of poles and zeros, also, we proposed the opti- mization process for finding the combination of optimized poles and zeros. From the transfer and reflection functions calculated from poles and zeros, we performed the quasi-elliptic LC prototype synthesis of multi-band filter. Using the proposed LC prototype synthesis method of multi-band filter, dual-band filter operating at GSM(880 960 MHz) and ISM(2,400 2,500 MHz) and triple-band filter operating at GSM(880 960 MHz) and ISM(2,400 2,500, 5,725 5,850 MHz) were designed and fabricated.

Capacitively I/O coupling structure for magnetically coupled resonator filters

A novel capacitively I/O coupling structure for coupled resonator filters is presented, analyzed theoretically, and demonstrated experimentally. A novel I/O coupling structure, adds two transmission zeros to the filter response. The bandpass filter uses second order magnetically coupled resonators with two transmission zeros to obtain lower insertion loss than a conventional cross-coupled microstrip filter. The two zeros are close to the passband, such that the selectivity and out-of-band rejection of the filter are significantly increased. The design is verified by experimental results.

Design of Multi-Layer Dual-Band Bandpass Filter Using Aperture-Coupling

In this paper, a multi-layer dual-band bandpass filter using aperture-coupling is proposed. Two coupling paths are formed with the two apertures which exist between two dual-mode resonators. The coupling coefficients can be adjusted without changing the shape of resonators. The bandwidth of the second passband can be adjusted without affecting the bandwidth of the first passband using the size of an aperture between stubs of the dual-mode resonator. The aperture coupling mechanism is theoretically analysed. The dual-mode bandpass filter for the 2.4 GHz WLAN, 3.5 GHz WiMax was designed and fabricated. The fabricated filter shows centered 2.45 GHz and 3.5 GHz with 9 % and 8 % of the bandwidth.

Compact Triple-Mode Resonator and Triple-Mode Filter Design

In this paper, we present a compact triple-mode resonator. The resonator itself can provide three transmission poles and one transmission zero. The resonance condition of each mode is analyzed theoretically, and the transmission zero is generated by open stub. Using this proposed resonator, a compact three pole bandpass filter for 2.4 GHz WLAN application with one transmission zero is designed and fabricated. The fabricated triple-mode filter shows 3 dB bandwidth of 15.8 % with the center frequency 2.4 GHz and less then 1.17 dB in 2.4~2.5 GHz passband. The size of fabricated triple-mode filter including the feed lines is 15.9 mm9.7 mm and very compact compared with previous reported triple-mode filter.