• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
• /
• 2001.11a
• /
• pp.464-468
• /
• 2001

In this paper, we propose a robust watermarking technique that accepts time scaling, pitch shift, add noise and a lot of lossy compression such as MP3, AAC, WMA. The technique is developed based on digital filtering. Being designed according to critical band of HAS (human auditory system), the digital filters nearly affect audio quality. Furthermore, before implementing digital filtering, wavelet transform decomposes the audio signal into several signals that is composed of specific frequencies. Designed digital filters scan the decomposed signal. The designed digital filter, band-stop filter, distorts and eliminates specific frequencies of audio signals. Watermarking detection can be accomplished by FFT (Fast Fourier Transform). Firstly, segments of audio signal are transformed by FFT. Then, the obtained amplitude spectrum by FFT is summed repeatedly. Finally the watermark detector can find filters used to watermark encoding based on eliminating frequencies. The suggested technique can embed 4bits/s in a robust manner.

• ETRI Journal
• /
• v.25 no.5
• /
• pp.345-355
• /
• 2003

In this paper, we propose a method for designing a class of M-channel, causal, stable, perfect reconstruction, infinite impulse response (IIR), and parallel uniform discrete Fourier transform (DFT) filter banks. It is based on a previously proposed structure by Martinez et al. [1] for IIR digital filter design for sampling rate reduction. The proposed filter bank has a modular structure and is therefore very well suited for VLSI implementation. Moreover, the current structure is more efficient in terms of computational complexity than the most general IIR DFT filter bank, and this results in a reduced computational complexity by more than 50% in both the critically sampled and oversampled cases. In the polyphase oversampled DFT filter bank case, we get flexible stop-band attenuation, which is also taken care of in the proposed algorithm.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.7 no.3
• /
• pp.166-176
• /
• 2007

Radio frequency (RF) microelectromechanical systems (MEMS) have been pursued for more than a decade as a solution of high-performance on-chip fixed, tunable and reconfigurable circuits. This paper reviews our research work on RF MEMS switches and switching circuits in the past five years. The research work first concentrates on the development of lateral DC-contact switches and capacitive shunt switches. Low insertion loss, high isolation and wide frequency band have been achieved for the two types of switches; then the switches have been integrated with transmission lines to achieve different switching circuits, such as single-pole-multi-throw (SPMT) switching circuits, tunable band-pass filter, tunable band-stop filter and reconfigurable filter circuits. Substrate transfer process and surface planarization process are used to fabricate the above mentioned devices and circuits. The advantages of these two fabrication processes provide great flexibility in developing different types of RF MEMS switches and circuits. The ultimate target is to produce more powerful and sophisticated wireless appliances operating in handsets, base stations, and satellites with low power consumption and cost.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.18 no.2
• /
• pp.260-267
• /
• 2014

In this paper, the unit cell of LH structure using microstrip transmission line and chip capacitor is devised, and the reactive components of equivalent circuit are extracted from the proposed unit cell. And then, we have analyzed for the unit cell parameters and applied the characteristics to the wideband high pass filter design. This filter cascading several unit cells with high pass property has been implemented on microstrip transmission line, and the performance has been the band rejection characteristics of 62.9 dB in the stop band to 0~2.18 GHz and less than the insertion loss of 1.17 dB in the pass band from 3.0G Hz to 12.75 GHz.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.3
• /
• pp.1734-1739
• /
• 2014

In this paper, microstrip low pass filter using transmission line with the modified DCRLH structure is designed and fabricated to be removed a spurious resonant mode, and a deep attenuation in stop band. The low pass filter is composed of shunt open-stub to get a deep attenuation and series short-stub to eliminate the spurious harmonics in stop band. In this way, the spurious harmonics occurring on the higher order frequency are suppressed and the filter performance is improved. Insertion loss and VSWR of the fabricated microstrip low pass filter in the passband from DC to 1.5 GHz is 1.26 dB and 1.65, and attenuation on the stopband from 1.84 GHz to 2.18 GHz is less than -100 dB. And also this filter has a good performance for 20 watt power test.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2018.05a
• /
• pp.55-56
• /
• 2018

In this paper, a method for analyzing the dielectric constant of a planar substrate is proposed. To this end, a band-stop filter was created by adding a H-shaped resonant aperture to the ground plane of a microstrip transmission line. A planar substrate of 2 mm thickness was placed behind the ground plane of the microstrip transmission line and the change of the resonant frequency with the change of the dielectric constant of the substrate was investigated. It can be seen that the change ratio of the frequency to the reference resonant frequency is larger than that of the conventional complementary split ring resonator structure.

• Korean Journal of Optics and Photonics
• /
• v.18 no.3
• /
• pp.190-195
• /
• 2007

A novel optical coupling filter with finite-thickness metal-strip gratings printed on optical planar dielectric slabs is proposed, and Bragg conditions of the device are rigorously evaluated by using Modal Transmission-Line Theory (MTLT). The numerical results reveal that the guiding structures have filtering properties due to a leaky-wave stop-band while conventional DFB guiding structures consisted of dielectric gratings depend on a feedback-wave stop-band. Consequently, it shows that the optical coupling titter dependent on the leaky-wave filtering characteristics can be compounded of such optical devices as LD and optical fiber.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.45 no.1
• /
• pp.103-109
• /
• 2008

In this papaer, a new type of ${\lambda}_g/4$ short stub band pass filter and ${\lambda}_g/2$ open stub band pass filter are purposed. Both are designed using FSCS technique for harmonic suppression. The proposed filters that used FSCS technique and a broadband stop filter is integrated to band pass filter to suppress the harmonics. The BSF are also placed between stubs so that the size is larger than prevent as compared to conventional one. The propose filters have center frequency of 5.8 GHz, bandwidth of 50% and harmonics suppressin is 120% has in bandwith. The measurement results in the case of ${\lambda}_g/4$ short stub filter, insertion loss of 0.5 dB, return loss of 14 dB are achieved and in the case of ${\lambda}_g/2$ open stub filter, loss of 0.8 dB, return loss of 14.4 dB are achieved. The simulation results and the measurement results are almost the same.

• Journal of electromagnetic engineering and science
• /
• v.11 no.3
• /
• pp.207-212
• /
• 2011

This paper presents a CPW-fed antenna with three slots. The proposed antenna can operate at 1.9~2.1 GHz and 2.9~3.3 GHz which are generated by the two rectangular slots, and 4.5~11.6 GHz which is generated by the main patch. The semicircle-slot is used as a band-notched filter to stop at a desired band (5.150~5.825 GHz) limited by IEEE 802.11a or HIPERLAN/2 applications. The currents concentrate around corresponding slots at the desired band. The proposed antenna is very small in size, with overall dimensions of $27{\times}32{\times}1\;mm^3$ etched onto an FR4-printed circuit board (PCB).

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.4 no.1
• /
• pp.13-21
• /
• 1967

A low pass filter is synthesized with R, C and negative impedance converters(NIC). The filter has a 4-th order elliptic function, which gives best magnitude approximation with equi-ripple characteristics both in pass and stop band. And experimental investigations have been made on the effect of the anticipated deviation of the NIC conversion factor and of possible loaded operation. Through the study, it has been cocluded that: 1. For minimum pole-zero sensitivity with respect to the NIC conversion factor, the network of a parallel RC-NIC configuration is preferable and the Horowitz polynomial decomposition method is applied in the synthesis procedure. 2. A few percentage variation of the NIC conversion factor changes the frequency and amplitude characteristics of the filter by nearly negligible amount. 3. With a load resistance below the critical value, the filter turns into an oscillator.