Lih-Shan Chen

Investigation in Open Circuited Metal Lines Embedded in Defected Ground Structure and Its Applications to UWB Filters

A novel method for notch implementation in ultrawideband (UWB) bandpass filter (BPF) using open circuited metal lines embedded in a defected ground structure (DGS) is proposed. Distinct from traditional notch implementation, the proposed method uses the additional metal lines with half waveguide length embedded in defected ground structure to produce additional notch band behavior based on the DGS bandpass behavior. Furthermore, the equivalent circuit model of the proposed UWB BPF with notch implementation is established for explaining the circuit behaviors more explicitly. In this way, the proposed circuit has a very small size, only amounting to 0.41 by 0.22 guided wavelength at the center frequency of 6.85 GHz. The experimental filter has a notch band frequency of 5.5 GHz, with two observable attenuation poles at 1.65 and 11.36 GHz, respectively. The measured BPF insertion loss is less than 1.0 dB throughout the passband of 3.1 to 10.6 GHz, and the variation of group delay is less than 0.2 ns in this band, except for the notched band.

Low-Temperature Sintering of Microwave Dielectrics (Zn,Mg)TiO3

Dielectrics (Zn,Mg)TiO3, having a high dielectric constant and a near zero temperature coefficient of resonant frequency are promising materials for microwave applications. In this work, Bi2O3 was added to (Zn,Mg)TiO3 as a low-temperature-sintering dopant. The addition of Bi2O3 significantly improved the densification of (Zn,Mg)TiO3, which were densified below 1000°C. In addition, the decomposition temperature of (Zn,Mg)TiO3 increased as the magnesium substitution increased. Microwave dielectric properties of (Zn,Mg)TiO3 ceramics depend on crystalline structure. By properly adjusting the amount of magnesium, a small temperature coefficient of resonant frequency was obtained for (Zn,Mg)TiO3 dielectrics.

A New Approach of Dual-Band Filters by Stepped Impedance Simplified Cascaded Quadruplet Resonators with Slot Coupling

This paper presents novel approaches for dual-band bandpass fllter design utilizing stepped impedance simplifled cascaded quadruplet resonators (SI-SCQRs) with slot coupling. A pair of SI- SCQRs forms a cross coupled dual-band flltering path to provide high selectivity passband response, and a slot coupling structure provides SI-SCQRs with another flltering path for improving and controlling the performances of the dual-band fllter such as insertion loss and bandwidth. Measured insertion losses are 0.26dB and 1.2dB, and return losses are better than 16.3dB and 15.2dB at the flrst and second

Characterization of Embedded Spiral Inductors in Co-Fired Ceramic Substrates

Embedded planarized inductors can be fabricated using the low-temperature co-fired ceramic technique. Larger inductance is obtained when using a spiral pattern, because the mutual inductance between adjacent conductors has a positive sign. In addition, because of their simple geometry and easy fabrication, spiral-type inductors are widely used. For embedded five- and ten-turn spiral coils, the inductances of about 0.3 and 1.2 µH were obtained, respectively. The value of inductance was almost unchanged in the frequency range between 500 kHz and 40 MHz. The quality factor reaches a peak with increasing frequency and then falls. The peak values (about 10 MHz) of the five- and ten-turn spiral coils are about 20 and 32, respectively.

A Low Power Consumption and Wide-Band Input Matching CMOS Active Balun for UWB System Applications

This work presents an ultra-wideband (UWB) active balun (balanced-to-unbalanced) with current-reused technique for wideband input matching and low power consumption by using standard 0.18 μm CMOS processes. The proposed circuit, using parallel common gate and common source structure, can efficiently improve the input-matching bandwidth for up to 10 GHz. Besides, the proposed circuit has good gain imbalance and phase imbalance from 3.1 GHz to 10.6 GHz. The proposed active balun achieved 4 ± 1 dB gain with amplitude (gain) imbalances less than 0.5 dB, phase differences of 180° ± 2°, 11.7 mW power consumption at 1.8 V supply voltage from 3.1 GHz to 10.6 GHz, and the chip size including pads is 0.76 × 0.73 mm2.

Miniaturized Wideband Ring-Type Bandpass Filters with Upper Stopband Characteristic

A new class of wideband ring-type microstrip bandpass filter is proposed under smaller size of three quarters waveguide length section. One via hole is placed at perpendicular position in a squared ring, whereas two short-circuited sections are formed in the ring-type microstrip bandpass filter similar to a dual-mode ring filter in shape, thereby making up a three quarters waveguide length ring-type microstrip bandpass filter. By adjusting the short-circuited sections, the bandwidth of the center frequency can be controlled easily. As a pair of open-circuited stubs is placed between the two ports, two extra resonances can be used to improve the out-of-band performance. Afterwards, a novel microwave microstrip filter has been successfully fabricated with the lower insertion loss S 21 of 0.48 dB, return loss S 11 of 30 dB, 3 dB bandwidth of 80%, and central frequency of 2.4 GHz. Simulated and measured results show good wideband filtering performance with widened upper stopband outside the wide passband.

Characterization of Internal Capacitors Based on Glass-Added Barium Titanate

Barium–calcium–aluminum–borosilicate glass is added as a sintering promoter to reduce the sintering temperature of barium titanate. The dielectric properties of the glass-added barium titanate-based internal capacitors are investigated. The dielectric constants of the composites were found to increase with sintering temperature. A capacitance of about 2.3 nF/cm2 with the dissipation factor of 2.9% is obtained for a 20 wt% glass-added BaTiO3 internal capacitor after being cofired with low dielectric constant ceramic substrate at 950°C. The percent change of capacitance is confined within ±10% and the dissipation factor is stable in the measured temperature range.

Controlling the Frequency of Simultaneous Switching Noise Suppression by Using Embedded Dielectric Resonators in High-Impedance Surface Structure

This work presents a novel design for high-impedance surface (HIS) embedded dielectric resonator (DR) structures to e-ciently control bandwidth of suppression simultaneous switching noise (SSN) in high speed digital printed circuit boards (PCBs). The proposed structure is designed by periodically embedding high dielectric constant materials into the substrate between a continuous power plane and a middle patch. A conventional HIS structure has only one resonance frequency to produce stopband while the proposed structure has two resonances to widen the suppression bandwidth. The i30dB stopband of the proposed structure is about two times wider than that of a conventional HIS structure. The excellent SSN suppression behavior was verifled by measurements and simulations.

Dielectric Properties of Internal Capacitors in Co-fired Ceramic Substrates

Dielectric properties of barium titanate-based internal capacitors characterized by capacitance, dissipation factor, and temperature change in capacitance are reported. A capacitance of about 10 nF/cm2 with the dissipation factor of 2.3% is obtained for the BaTi0.975O3+2 wt% LiF internal capacitor after being co-fired with low dielectric constant ceramic substrates at 900°C. The percent change of capacitance is confined within ±10%. The dissipation factor is stable and decreases with increasing temperature.

Simultaneous Switching Noise Suppression Using Nickel-Ferrite Thin Films

In this article, magnetic materials are employed to eliminate the ground bounce noise or simultaneous switching noise in high-speed digital circuits. The nickel film, deposited on a sapphire substrate by RF-sputter, was applied to suppress simultaneous switching noise. The proposed structure can efficiently restrain the simultaneous switching noise with broadband (totally 16GHz), and the ground bounce noise can be significantly lessened over 90%. Besides, the proposed structure does not produce undesired resonant peaks in the lower frequencies, and the electromagnetic interference problems are solved.