Chin Sheng Chang

A novel compact ring dual-mode filter with adjustable second-passband for dual-band applications

In this letter, a novel compact ring dual-mode with adjustable second-passband for dual-band applications are presented. A ring resonator with two different geometric dimensions are derived and designed to have identical fundamental and the first higher-order resonant frequencies, and to establish appropriate couplings in the structure. Moreover, the proposed filter has smaller size as compared with the basic topology of stopband filters and stepped-impedance-resonator (SIR) filters. The measured filter performance is in good agreement with the simulated response.

A novel cross-shape DGS applied to design ultra-wide stopband low-pass filters

This letter presents a novel low-pass filter with an ultra-wide stopband. The proposed filter is comprised of a new cross-shape defected ground structure (CSDGS). By using this structure, the filter not only supports conventional DGS performances with a sharp rejection, but also exhibits an ultra-wide stopband. For the deigned low-pass filter, an insertion loss of less than 2dB from dc to 3.5GHz and the rejection is better than 20dB from 4.3 to 15.8GHz. Predicted performances show widened and deepened stopband beyond the low passband. Furthermore, it is confirmed by measurement.

A four-stage Ku-band 1 watt PHEMT MMIC power amplifier

In this paper, a Ku-band 1 watt AlGaAs/InGaAs/GaAs PHEMT MMIC power amplifier for VSAT ODU (outdoor unit) applications is demonstrated. This four-stage amplifier is designed to fully match for a 50 ohm input and output impedance. With 7 V and 700 mA DC bias condition, the amplifier has achieved 30 dB small-signal gain, 30.8 dBm 1-dB gain compression power with 24.5% power-added efficiency (PAE) and 31.3 dBm saturation power with 27.5% PAE from 14 to 17 GHz.

A fully matched 8W X-band PHEMT MMIC high power amplifier

A X-band 8-watt AlGaAs/InGaAs/GaAs PHEMT MMIC power amplifier for the active phase radar applications is demonstrated. This amplifier is designed to fully match 50 ohm input and output impedance. With 8 volts and 850 mA DC bias condition, 17.5 dB small-signal gain, 39.3 dBm (8.5 watt) 2-dB gain compression power with 33.7% power-added efficiency and 40 dBm (10 watt) saturation power from 9.3 to 10.4 GHz can be achieved.

A compact bandpass filter with enhanced stopband characteristics by an asymmetric cross-shape defected ground structure

In this paper, we present an effective technique to enhance stopband bandwidth for a bandpass filter by using an asymmetric, cross-shape defected ground structure (CSDGS). A single CSDGS can provide a higher attenuation rate near passband and broader stopband bandwidth. Moreover, with the asymmetric CSDGS, two different resonant frequencies can be excited and controlled independently, resulting in synthesizing a passband. The synthesized bandpass filter can be modeled by parallel LC resonant circuits in connection with T-networks. The bandwidth and insertion loss of this bandpass filter at 4.2 GHz is 28.6% and -1.44 dB, respectively, and 20 dB rejection in the stopband is up to four times the central frequency. All the synthesized bandpass filters have been measured and are in good agreement with simulated results

High reliability in low noise InGaP gated PHEMTs

This work presents a study on the high reliability of noise characteristics of InGaP low noise PHEMTs, which was demonstrated through DC and thermal stress. The devices that we used were In/sub 0.49/Ga/sub 0.51/P/In/sub 0.15/Ga/sub 0.85/ As/GaAs low noise pseudomorphic high electron mobility transistors (PHEMTs) with the gate dimensions of 0.25 /spl times/ 160 /spl mu/m/sup 2/. The DC-stress conditions are 1) V/sub DS/ = 6V, V/sub GS/ = 0V and 2) I/sub G/ = -8 mA (50mA/mm). The ranging of thermal-stress is from 100/spl deg/C to 250/spl deg/C. The noise characteristics were measured at 12 GHz and DC bias condition is V/sub DS/ = 2V, I/sub DS/ = 10 mA. The key noise-effect parameters of devices are the deep-trap behaviour in device, source/gate resistances, gate to source capacitance and intrinsic transconductance. We showed the very small variation of minimum noise figure, NF/sub min/ and associated power gain, G/sub a/ after DC and thermal stress by explaining the variation of these key parameters to demonstrate the high reliability in InGaP low noise PHEMTs.

A Self-bias Ku-band 1-Watt PHEMT Power Amplifier MMIC With A Compact Source Capacitor

In this paper, the design of a self-bias 1.8 mm AlGaAs/InGaAs/GaAs PHEMT with a compact source capacitor for operation in Ku-band frequency is described. Based on the proposed device, a self-bias Ku-band 1-W two-stage power amplifier MMIC is also demonstrated. Under single bias condition of 8 V and 630 mA, the self-bias MMIC possesses 14.2 dB small-signal gain, 30.2 dBm output power at 1-dB gain compression point with 19.2% power added efficiency and 31.3 dBm saturated output power with 22.5% power added efficiency at 14 GHz. With the performance comparable to the dual-bias MMIC counterpart, the proposed self-bias MMIC is more attractive to system designers on VSAT applications.

A Single-bias 2W PHEMT MMIC by Gate Zero-Bias Technique for C Band Applications

A single supply, fully matched high linearity 2W power amplifier utilizing the gate zero-bias power PHEMT technology is developed for 5.8GHz WLAN applications. At Vgs= 0 V, Vds= 5 V, the power amplifier with 33dBm of peak P1dB, 25% of PAE, 12.8dB small-signal gain can be seen. Moreover, high-linearity with 43dBm third-order intercept point at a single carrier output power level of 23dBm is also achieved.

A Gate Zero-Bias 2W PHEMT Power Amplifier Operating at 3.5 GHz

A single supply 2W MMIC power amplifier, operating between 3.3GHz and 3.8GHz by implementing AlGaAs/InGaAs/GaAs PHEMT for the applications of WiMax, is demonstrated. Using the gate zero-bias configuration, i.e., VGS=0 and IDSS, one can use only one single bias instead of dual bias in the depletion mode PHEMTs. This two-stage amplifier is designed by using a zero gate bias configuration i.e., VGS=0 and at saturated drain current IDSS, for class A power amplifier operation. The two-stage MMIC amplifier possesses the characteristics of 25.9dB small-signal gain and 34.0dBm 1-dB gain compression power. Moreover, with a single carrier output power level of 2ldBm, very high linearity with a 47dBm third-order intercept point operating at 3.5GHz is also achieved.

High linearity power amplifier for PHS base station using a 50 mm AlGaAs/InGaAs/GaAs PHEMT

A high linearity, high efficiency 1.9 GHz power amplifier sub-system using a 50 mm AIGaAs/InGaAs/GaAs PHEMT for PHS 500 mW base station is demonstrated. Under 10 V and 3.8 A bias condition, the output stage amplifier has achieved 12.5 dB small-signal gain, 43.7 dBm PldB with 43% PAE and 44 dBm saturated output power with 41% PAE. For the amplifier sub-system, the ACPR at 600 KHz and 900 KHz offset from 1.906 GHz when operating at 38.5 dBm output power with /spl Pi//4-DQPSK signal are better than 75 dBc and 79 dBc, respectively.