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Theory for Pseudo-Butterworth Filter Response and Its Application to Bandwidth Tuning
Nam, Seunggoo,Lee, Boyoung,Lee, Juseop Professional Technical Group on Microwace Theory a 2017 IEEE Transactions on Microwave Theory and Techniqu Vol. No.
<P>This paper presents a new class of filter responses called pseudo-Butterworth filter response. A detailed mathematical analysis on the pseudo-Butterworth response has been carried out. In addition, the comparison between the typical complete Butterworth response and the new pseudo-Butterworth response is provided. The theory for the pseudo-Butterworth filter response indicates that bandwidth tuning maintaining excellent return loss performance can be executed adjusting not all coupling structures of a filter. As an example, a bandwidth tuning method for a second-order filter is presented. For verifying the presented bandwidth tuning theory, a second-order substrateintegrated waveguide (SIW) resonator filter has been designed, fabricated, and measured. As an example of applications to higher order filters, a theory for the fourth-order pseudo-Butterworth responses and a bandwidth tuning method for the fourth-order filters have been developed. A fourth-order filter has also been fabricated and measured for verifying the presented bandwidth tuning technique.</P>
Reconfigurable Bandpass Filter With Resonators in Cul-De-Sacs for Producing Notches
Seunggoo Nam,Boyoung Lee,Beyoungyoun Koh,Juseop Lee IEEE 2017 IEEE transactions on components, packaging, and ma Vol.7 No.9
<P>We present a new design method for bandpass filters capable of adjusting center frequencies, bandwidths, and notches. For designing such filters, filter topologies employing frequency-tunable resonators in cul-de-sacs are developed. The cul-de-sac resonators are mainly responsible for constructing notches, while the resonators in main paths form passbands. For verifying the presented design method, we have designed two bandpass filters. Each filter consists of two different resonator types: microstrip-line resonators for forming passbands and substrate-integrated waveguide resonators for producing notches. The measured results of the two designed filters show that frequency-tunable notches can be placed next to the passbands without producing unwanted resonant peaks that are usually observed in bandpass-bandstop filter cascades. This indicates that the filters designed using the presented topologies can replace bandpass-bandstop filter cascades.</P>
Compact 28 GHz Folded Butler Matrix Using Low-Temperature Co-fired Ceramics
Nam Seunggoo,최세환,Ryu Jongin,이재영 한국전자파학회 2022 Journal of Electromagnetic Engineering and Science Vol.22 No.4
This paper introduces a miniaturized Butler matrix design method using a folded structure. The Butler matrix was fabricated in multilayers using low-temperature co-fired ceramics (LTCC) and designed to operate at 28 GHz. The conventional one-plane Butler matrix has a major disadvantage in that the length and volume of the system inevitably have to be increased. By using the proposed folded structure, the length can be reduced more than two times compared to the general one-layer Butler matrix. In order to minimize the loss of the Butler matrix, it was designed in a stripline structure by forming a ground plane on the upper and lower surfaces of each layer. A signal is transmitted between the layers through via holes. A 4 × 4 Butler matrix was fabricated and measured for the demonstration of the proposed concept. The proposed Butler matrix was measured through a precisely calibrated antenna chamber with closed cell absorbers. The dimensions of the fabricated Butler matrix are 14 mm × 20 mm × 1.52 mm. The beam of the fabricated Butler matrix can be properly steered in a total of four directions.
$K$ -Band Substrate-Integrated Waveguide Filter Using TM21 Mode With Enhanced Stopband Attenuation
Lee, Boyoung,Nam, Seunggoo,Koh, Beyoungyoun,Lee, Juseop THE INSTITUTE OF ELECTRICAL ENGINEERS 2017 IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS Vol.27 No.8
<P>In this letter, we present a method for enhancing the stopband attenuation performance of a K-band TM21 mode filter using substrate-integrated waveguide resonators. To improve the stopband response, we suppress and move spurious resonant peaks and produce transmission zeros. The step-by-step procedure of the proposed three-step method is shown in detail. The measurements show that when using the presented method, the filters exhibit better stopband performances than those in which the presented steps are not followed.</P>
Boyoung Lee,Seunggoo Nam,Beyoungyoun Koh,Changsoo Kwak,Juseop Lee Professional Technical Group on Microwace Theory a 2015 IEEE Transactions on Microwave Theory and Techniqu Vol. No.
<P>In this paper, we present a K-band substrate-integrated waveguide resonator bandpass filter structure. The filter uses an antisymmetric mode of the resonator for the first time. A design method for the external coupling structure of the resonator utilizing the antisymmetric mode is described. In addition, a methodology for suppressing neighboring resonances close to the passband is demonstrated. This method can enhance stopband attenuation performance without additional loss. The proposed filter can tune the center frequency by adjusting tuning components. In order to verify the proposed filter structure and design method, we have fabricated and measured a K-band filter and demonstrated higher order filter design.</P>
Third-Order Frequency-Agile Substrate-Integrated Waveguide Filter With a Pair of Transmission Zeros
Lee, Boyoung,Nam, Seunggoo,Lee, Tae-Hak,Lee, Juseop THE INSTITUTE OF ELECTRICAL ENGINEERS 2017 IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS Vol.27 No.6
<P>In this letter, we present a third-order frequency-agile substrate-integrated waveguide (SIW) filter with a pair of transmission zeros. In addition, a relationship between the symmetric and asymmetric topologies for having same frequency responses is derived in this letter so that the coupling values of the asymmetric filter topology can be directly obtained from those of the symmetric one. For practical implementation, we also present a new methodology for physical implementation of a source-to-multiresonator coupling for frequency-tunable SIW resonator structure. The filter has been fabricated and measured for verifying the presented filter topology.</P>
Single-Filter Structure With Tunable Operating Frequency in Noncontiguous Bands
Boyoung Lee,Seunggoo Nam,Tae-Hak Lee,Chang-Soo Ahn,Juseop Lee IEEE 2017 IEEE transactions on components, packaging, and ma Vol.7 No.1
<P>In this paper, we present a frequency-tunable substrate-integrated waveguide bandpass filter of which the operating frequency band can be switched between S-band and X-band. One of unique features of the presented filter is that a single-filter structure can replace a filter bank composed of an S-band filter, an X-band filter, and two switches at input and output ports for selecting one of two filters. In addition, the filter can tune the center frequency in each band. This paper provides the design method, fabrication, and measurement of the presented filter structure.</P>
Bandwidth Tuning of Resonator Filter Using Reduced Number of Tunable Coupling Structures
Lee, Boyoung,Nam, Seunggoo,Lee, Juseop Professional Technical Group on Microwace Theory a 2019 IEEE transactions on microwave theory and techniqu Vol.67 No.4
<P>This paper presents a new bandwidth tuning theory for Butterworth-response resonator filters. The presented theory shows that the bandwidth of odd-order Butterworth filters can be varied by adjusting only two interresonator coupling structures while maintaining a perfect impedance matching at the center frequency. In other words, this paper presents an analytic approach to reduce the number of tunable coupling structures when designing a bandwidth-tunable resonator filter. Theories for third- and fifth-order direct-coupled filters are discussed in detail, and it is shown that only two interresonator coupling structures are required to be tunable. In addition, for verifying the new bandwidth tuning method, a fifth-order cylindrical cavity filter has been designed, fabricated, and measured. The fabricated filter has an 11:1 bandwidth tuning range.</P>