A 55-GHz direct-conversion RF transmitter with high linearity and quadrature mismatch calibration is presented. The RF transmitter comprises a power amplifier, image-rejection quadrature mixer, baseband amplifier, and quadrature VCO. To achieve a highly linear output power per die area, we employ a distributed active transformer-based two-way power-combining power amplifier, and a pFET-based passive mixer. The I/Q mismatch calibration is implemented for a high image-rejection ratio. The amplitude mismatch is calibrated by tuning the gate biases of the mixer switching FETs, and the phase mismatch is calibrated by 3-bit switched capacitor tuning at the LO buffer LC load. Realized in 40 nm CMOS with a die area of $\boldsymbol{1.6}\times \boldsymbol{0.7}\ \mathbf{mm}^{2}$ , the RF transmitter exhibits $\mathbf{OP}_{\mathbf{1dB}}$ of $+\boldsymbol{12.8}\mathbf{dBm}, \mathbf{P}_{\mathbf{sat}}$ of +13.9 dBm, IRR of -45.2 dBc, LOFT of -36.3 dBc. The $\mathbf{OP}_{1\mathbf{dB}}$ per die area is 17 W/mm 2 .
A 28GHz RF transmitter is designed in 65nm CMOS for 5G millimeter-wave radio applications. The transmitter is based on a direct-conversion quadrature up-conversion architecture for achieving small silicon area and low power dissipation. The image suppression is improved by adopting I/Q LO mismatch calibration at the LO driving buffer of mixer. The power amplifier is designed in a differential type with cross-coupled neutralized capacitors for stability and reverse-isolation improvement. Combined schematic and EM simulation results show that the transmitter gives the power gain of 37 dB, OP1dB of +5.8 dBm, and P sat of +11.6 dBm. The total transmitter consumes 111 mW from a 1.2 V supply and occupies 1.78 mm 2 .
In a low-voltage low-power wideband CMOS VCO that employs a capacitor array bank for realizing multiple discrete sub-band tuning curves, the tank Q factor can be temporarily degraded during the sub-band switching. This can lead to a momentary oscillation quenching and a possible loss of lock in a phase-locked loop synthesizer. This work proposes a sequential capacitor switching scheme as well as a current boosting technique to alleviate the temporary Q degradation and thus achieving more robust subband switching in a low-power wideband CMOS VCO. Realized in 65 nm CMOS and tested with a 1 V supply, a wideband (1.82-2.53 GHz) and low-power (0.55 mW) VCO that employs a 5-bit capacitor array with the proposed switching technique demonstrates a very robust sub-band switching operation, and thus guarantees stable operation in PLL synthesizers.
A fractional-N PLL synthesizer is designed in 65 nm CMOS general process for Bluetooth low-energy applications. For low-power consumption, the PLL synthesizer is designed in a single 1-V supply. The tuning range of PLL Synthesizer is 1.9-2.7 GHz to cover the ISM band for 1/5-fRF sliding-IF receiver. The simulated VCO phase noises at 1 MHz offset are -110 and -120 dBc/Hz at 2.7 and 1.9 GHz, respectively. With a fast VCO frequency calibration process included, the total lock time of the synthesizer is 12 μs. The synthesizer dissipates 3 mW from 1 V supply voltage.
방사능 오염 토양 복원을 위해 실험실 규모의 동전기 복원장치를 제작하여 가동 하던 중 토양 내 존재하던 금속이온의 용출로 금속 산화물이 발생하여 음극의 전류 흐름을 차단하는 문제가 발생하였다. 전류의 차단으로 토양 내 우라늄 제거 능력이 상실되어 이러한 문제를 해결하는 해결 방안을 모색하여 개선된 동전기 복원 장치를 제작하였다. 개선된 실험실 규모 동전기 복원 장치를 이용하여 토양복원 실험을 25 일간 수행 하였을 때 우라늄 잔류 농도는 0.81 Bq/g으로 약 96.8%의 제거 효율을 보였으며, 초기 우라늄 농도 50 Bq/g 일 때 우라늄 규제 해제 농도인 1 Bq/g 이하로 제거 되기 까지는 34 일의 복원 기간이 필요하고, 초기 우라늄 농도 75 Bq/g, 100 Bq/g 일 때 각 42 일, 49 일이 필요한 것으로 나타났다. The original pilot-scale electrokinetic equipment suitable to soil contamination characteristics of Korean nuclear facility sites was manufactured for the remediation of soil contaminated with uranium. During the experiment with the original electrokinetic equipment, many metal oxides were generated and were stuck on the cathode plate. The uranium removal capability of the original electrokinrtic equipment was almost exhausted because the cathode plate covered with metal oxides did not conduct electricity in the original electrokinetic equipment. Therefore, the original electrokinetic equipment was improved. After the remediation experience for 25 days using the improved electrokinetic remediation equipment, the removal efficiency of uranium from the soil was 96.8% and its residual uranium concentration was 0.81 Bq/g. When the initial uranium concentration of soil was about 50 Bq/g, the electrokinetic remediation time required to remediate the uranium concentration below clearance concentration of 1.0 Bq/g was about 34 days. When the initial uranium concentration of soil was about 75 Bq/g, the electrokinetic remediation time required to remediate below 1.0 Bq/g was about 42 days. When the initial uranium concentration of soil was about 100 Bq/g, the electrokinetic remediation time required to remediate below 1.0 Bq/g was about 49 days.
α-Gallium oxide, with its large band gap energy, is a promising material for utilization in power devices. Sapphire, which has the same crystal structure as α-Ga2O3, has been used as a substrate for α-Ga2O3 epitaxial growth. However, lattice and thermal expansion coefficient mismatches generate a high density of threading dislocations (TDs) and cracks in films. Here, we demonstrated the growth of α-Ga2O3 films with reduced TD density and residual stress on microcavity-embedded sapphire substrates (MESS). We fabricated the two types of substrates with microcavities: diameters of 1.5 and 2.2 μm, respectively. We confirmed that round conical-shaped cavities with smaller diameters are beneficial for the lateral overgrowth of α-Ga2O3 crystals with lower TD densities by mist chemical vapor deposition. We could obtain crack-free high-crystallinity α-Ga2O3 films on MESS, while the direct growth on a bare sapphire substrate resulted in an α-Ga2O3 film with a number of cracks. TD densities of α-Ga2O3 films on MESS with 1.5 and 2.2 μm cavities were measured to be 1.77 and 6.47 × 108 cm-2, respectively. Furthermore, cavities in MESS were certified to mitigate the residual stress via the redshifted Raman peaks of α-Ga2O3 films. Finally, we fabricated Schottky diodes based on α-Ga2O3 films grown on MESS with 1.5 and 2.2 μm cavities, which exhibited high breakdown voltages of 679 and 532 V, respectively. This research paves the way to fabricating Schottky diodes with high breakdown voltages based on high-quality α-Ga2O3 films.
A 54-862-MHz single-chip CMOS transceiver with a single LC voltage-controlled oscillator (VCO) fractional- N synthesizer is developed for TV-band white-space communications and cognitive radio applications. The transceiver is based on a single-conversion zero-IF architecture with integrated harmonic filtering capability. A combined harmonic rejection mixer and coarse RF tracking filter significantly lessens the in-band harmonic emission problem in the transmitter, as well as the harmonic mixing problem in the receiver. A fractional- N phase-locked loop (PLL) with only a single LC VCO and a wideband multimodulus local oscillator (LO) generator seamlessly covers the entire band. A wideband semi-dynamic divide-by-1.5 circuit is adopted in the LO generator to reduce the VCO tuning range requirement by 25 %. A pseudoexponential capacitor bank structure in the LC VCO substantially reduces the KVCO and fstep variations across the total band, which is beneficial for maintaining the PLL loop stability and dynamics over the wide band. The transceiver is implemented in 0.18-μ m CMOS, and operates with a single 1.8-V supply. The transmitter delivers a nominal output power of -3 dBm, and exhibits OP 1 dB of >; +6.4 dBm, OIP 3 of >; +15.9 dBm, and error vector magnitude (EVM) of <; -34.7 dB for 64-QAM signal. The image and carrier leakage calibration circuits suppress the leakage components below -41 dBc across the entire band. The receiver achieves about 100-dB gain dynamic range, 3.5-6.9-dB noise figure, <; -29-dB EVM, and -43.4/-59.7-dBc third/fifth harmonic mixing suppression. The synthesizer and LO generator achieves the integrated phase noise <; 0.8 rms degree over the entire band.
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