Hongjong Park

A Broadband GaN pHEMT Power Amplifier Using Non-Foster Matching

Non-Foster matching is applied to design a multi- octave broadband GaN power amplifier (PA) in this paper. The bandwidth limitation from high-Q interstage matching is overcome through the use of negative capacitor, which is realized with a negative impedance converter (NIC) using the cross-coupled GaN FETs. For high power operation over the entire bandwidth, the natural interstage matching is optimized for the upper subfrequency band and the lower subfrequency band is compensated for by the negative capacitance presented by non-Foster circuit (NFC). Detailed analysis is presented to understand the frequency and power limits of NIC circuits for PA applications. Two negative impedance matched PAs (NMPAs) are fabricated with 0.25- μm GaN pHEMT process. The implemented PA with 2× combining shows the output powers of 35.7-37.5 dBm with the power added efficiencies of 13-21% from 6 to 18 GHz. The 4× combining PA achieves over 5 W output power from 7 to 17 GHz. The NFC boosts the efficiencies and power below 12 GHz to achieve broadband performance without using any lossy matching or negative feedback. To our knowledge, this is the first demonstration of NIC-based broadband amplifiers with multi-watt-level output power.

6-18 GHz Reactive Matched GaN MMIC Power Amplifiers with Distributed L-C Load Matching

A commercial 0.25 μm GaN process is used to implement 6–18 GHz wideband power amplifier (PA) monolithic microwave integrated circuits (MMICs). GaN HEMTs are advantageous for enhancing RF power due to high breakdown voltages. However, the large-signal models provided by the foundry service cannot guarantee model accuracy up to frequencies close to their maximum oscillation frequency (Fmax). Generally, the optimum output load point of a PA varies severely according to frequency, which creates difficulties in generating watt-level output power through the octave bandwidth. This study overcomes these issues by the development of in-house large-signal models that include a thermal model and by applying distributed L-C output load matching to reactive matched amplifiers. The proposed GaN PAs have successfully accomplished output power over 5 W through the octave bandwidth.

A 6–18 GHz GaN pHEMT power amplifier using non-foster matching

Non-Foster matching is applied to design a multi-octave broadband GaN power amplifier (PA) in this work. The bandwidth limitation from high-Q interstage matching is mitigated through the use of negative capacitor, which is realized with a negative impedance converter (NIC). Detailed analysis is presented to understand the frequency and power limits of NIC circuits for PA application. A 6-18 GHz power amplifier fabricated with 0.25-μm GaN pHEMT process shows the output power reaching 35.7-37.5 dBm with 13-21% PAE. The NIC boosts the efficiencies and power below 11 GHz to achieve broadband performance without the use of any lossy matching circuits or negative feedback. To our knowledge, this is the first demonstration of NIC-based broadband amplifiers with Watt-level output power.

A 6–18 GHz GaN distributed power amplifier using reactive matching technique and simplified bias network

Two-stage reactively matched gain cells are applied to design a high-gain multi-octave distributed power amplifier (DPA) in this paper. The proposed reactively matched distributed amplifier (RMDA) structure shows a high gain and high output power performance within a small die size. The DC bias network of each section is simplified to implement the proposed structure in an MMIC and the design guide for the bias network is provided. A 6–18 GHz GaN DPA fabricated with the commercial 0.25-µm GaN HEMT process shows output power reaching 40.3–43.9 dBm with 16–27% PAE. To the best of our knowledge, this is the first demonstration of a GaN DPA using reactively matched gain cells, and it exhibits excellent small-signal gain and RF power performance capabilities among other reported GaN PAs with a multi-octave bandwidth up to the Ku-band.

RF parametric study on AlGaN/GaN HEMTs on Si-substrate for millimeter-wave PA

Size-optimized AlGaN/GaN HEMTs on Si-substrate are investigated for millimeter-wave power amplifier (PA) MMICs. The number of finger (2, 4, 8) and the unit finger width (25, 37.5, 50, 75, 100 μm) of devices are split in the AlGaN/GaN HEMTs process on Si-substrate. For searching the best suitable size for millimeter-wave PA, the RF performances such as Fmax and MAG (Maximum Available Gain) are investigated through S-parameter measurements and small signal model parameter extractions. Moreover, thermal resistances are extracted through pulsed IV measurement to evaluate thermal degradation on GaN HEMTs. Through these experiments and parametric analyses, 4×37.5 μm or 8 × 37.5 μm GaN HEMTs show the best RF performance keeping not larger thermal resistances (Rth). Thermal resistance and MAG are dependent on the gate pitch of GaN HEMTs. The selection of the proper gate pitch parameter of device is expected to bring the optimal power device performance in the millimeter-wave frequencies.

A 100~110 GHz LNA and A Coupler Using Standard 65 n CMOS Process

본 논문에서는 상용 65 n CMOS 공정을 이용하여 100～110 GHz에서 동작하는 저잡음 증폭기와 커플러를 구현하였다. 제작된 LNA는 3단 공통 소스 FET로 구성되었다. 단위 공통 소스 셀의 높은 이득 특성을 얻기 위해 이를 고려한 레이아웃을 하였다. 또한, 저잡음 특성과 충분한 이득을 얻기 위해 성능을 최적화시켰다. 커플러는 CMOS 공정의 multimetal을 이용한 broadside 커플러로 구성하였다. Density rule을 만족시키기 위한 metal strip을 사용해 이에 의한 영향을 고려해 커플러 동작이 가능하도록 설계하였다. 제작된 저잡음 증폭기의 측정 결과, 100 GHz에서 5.64 dB, 110 GHz에서 6.39 dB의 이득과 10 % 이상의 3-dB 대역폭, 11.66 dB의 잡음 지수를 얻었다. 커플러는 100～110 GHz 대역에서 2～3 dB의 삽입 손실, 1 dB 이하의 magnitude mismatch와 5° 이하의 phase mismatch를 얻었다.

A Highly Efficient Multi-Mode Balanced Power Amplifier for W-CDMA Handset Applications

A highly efficient multi-mode balanced power amplifier(PA) structure is proposed for W-CDMA handset applications. The proposed PA has 2-stage amplifier configuration and the stage-bypass and load impedance switching techniques were applied to enhance power efficiency at medium power level as well as low output power level. Using the two techniques, four highly efficient power modes were realized. To demonstrate the usefulness of the proposed structure, a GaAs HBT balanced PA module was designed, fabricated, and measured.