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We present an X-band bi-directional transmit/receive module (TRM) for a phased array system utilized in radar-based sensor systems. The proposed module, comprising a 6-bit phase shifter, a 6-bit digital step attenuator, and bi-directional gain amplifiers, is fabricated using 65-nm CMOS technology. By constructing passive networks in the phase-shifter and the variable attenuator, the implemented TRM provides amplitude and phase control with 360° phase coverage and 5.625° as the minimum step size while the attenuation range varies from 0 to 31.5 dB with a step size of 0.5 dB. The fabricated T/R module in all of the phase shift states had RMS phase errors of less than 4° and an RMS amplitude error of less than 0.93 dB at 9–11 GHz. The output 1dB gain compression point (OP1dB) of the chip was 5.13 dBm at 10 GHz. The circuit occupies 3.92 × 2.44 mm2 of the chip area and consumes 170 mW of DC power.

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In this paper, we present a phased-array transceiver chip operating in full X-band (8-12 GHz) in 65-nm CMOS technology. The presented transceiver for the transmit/receive module (TRM) consists of a 6-bit passive phase shifter, a 6-bit attenuator, a bi-directional gain amplifier (BDGA), and a single pole double throw (SPDT) switch connected to the internal power amplifier (PA) and the low-noise amplifier (LNA) to serve as a duplexer. A 64-bit SPI scan-chain is integrated for digital TRM control. The transmitter achieves greater than 15 dB of power gain with 11.84 dBm at the output 1-dB compression point (OP1dB). To achieve a wideband operation of the passive phase shifter, we assigned two different resonant frequencies for the phase leading and lagging networks and aligned the slopes of their phase responses to have the desired phase shifts at the center frequency. The RMS phase error is less than 5 • , and the RMS amplitude error is less than 0.45 dB for all phase and attenuation states within 8-12 GHz while dissipating 216 mW dc power from a 1 V power supply. The receiver shows greater than 15 dB of power gain and has a noise figure (NF) of less than 8.4 dB for the entire X-band. The RMS phase error and the RMS amplitude error are less than 5 • and 0.45 dB, respectively, for all control states within 8-12 GHz. The receiver consumes 110 mW with a 1 V power supply. The transceiver chip occupies an area of 4 × 1.88 mm 2 .

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We investigated the effects of recovery schemes on the characteristics of GaN Schottky diodes damaged by inductively coupled Cl2/H2/normalAr/CH4 plasma etching. The recovery schemes included N2 plasma exposure, N2 plasma plus annealing at 600°C in N2, and annealing at 700°C in N2. Ga-deficient GaN surface layers were observed after etching the GaN, and the Ga/N stoichiometry at the surface was most strongly affected by the Cl2 flow rate among the process variables. The samples annealed at 700°C showed a clear improvement in diode characteristics and a complete restoration of the Ga/N ratio from ca. 0.87 to ca. 1.0 at the surface layers, as measured by Auger electron spectroscopy. For all other damage-recovery schemes, the samples showed no significant enhancement in diode characteristics and incomplete restoration of Ga/N stoichiometry at the surface layers. © 2001 The Electrochemical Society. All rights reserved.

We examined the effects of gate recess process conditions on the electrical characteristics of 0.1-µm-gate-length metamorphic high-electron-mobility transistors (MHEMTs) by the comparative analysis of small-signal parameters. When the wide-gate-recess method is adopted, significant reductions in gate-to-drain conductance and gate-to-drain capacitance were obtained compared with those obtained by the of narrow-gate-recess method. These differences in small-signal parameters are due to the removal of the entire n+ cap layer and corresponding dissimilarity in gate structure when the wide-gate-recess method is used. The wide-gate-recess method produced ∼1/2 drain-source saturation current and extrinsic transconductance compared with the narrow-gate-recess method. In contract to the DC performances, a markedly enhanced S21 gain of 3.5 dB and an f max of 447 GHz were obtained from the MHEMTs processed by the wide-gate-recess method. This high f max is responsible for the proper selection of the gate recess method for what and is one of the best data thus far reported for 0.1-µm-gate-length MHEMTs.

This paper describes Monolithic Microwave Integrated Circuits (MMICs) for an X-band radar transceiver front-end implemented in 0.25 μm GaN High Electron Mobility Transistor (HEMT) technology. Two versions of single pole double throw (SPDT) T/R switches are introduced to realize a fully GaN-based transmit/receive module (TRM), each of which achieves an insertion loss of 1.21 dB and 0.66 dB at 9 GHz, IP1dB higher than 46.3 dBm and 44.7 dBm, respectively. Therefore, it can substitute a lossy circulator and limiter used for a conventional GaAs receiver. A driving amplifier (DA), a high-power amplifier (HPA), and a robust low-noise amplifier (LNA) are also designed and verified for a low-cost X-band transmit-receive module (TRM). For the transmitting path, the implemented DA achieves a saturated output power (Psat) of 38.0 dBm and output 1-dB compression (OP1dB) of 25.84 dBm. The HPA reaches a Psat of 43.0 dBm and power-added efficiency (PAE) of 35.6%. For the receiving path, the fabricated LNA measures a small-signal gain of 34.9 dB and a noise figure of 2.56 dB, and it can endure higher than 38 dBm input power in the measurement. The presented GaN MMICs can be useful in implementing a cost-effective TRM for Active Electronically Scanned Array (AESA) radar systems at X-band.