A 28 GHz T/R integrated circuit (IC) using common-leg circuit in 65 nm CMOS technology is presented. The proposed common-leg T/R IC is composed of single pole double throw (SPDT) and double pole double throw (DBDT) switches, 5-bit phase shifter, and 5-bit attenuator, uni-directional amplifiers for the transmit and receive modes. The measured gains for the transmit and receive modes are 3.5 and 1 dB at 26-30 GHz, respectively. The design provides full phase control range of 360°with least significant bit (LSB) of 11.25°, and attenuation control range of 23 dB with LSB of 1 dB. The proposed common-leg T/R IC has the maximum RMS phase error of 7°, and amplitude error of 0.6 dB at 26-30 GHz. The saturated output power for the transmit mode is 0 dBm, and the input P1dB for the receive mode is −20 dBm at 28 GHz. The chip core size is 1.3 × 0.8 mm 2. The DC current is 130 mA for the transmit mode and 98 mA for the receive mode at 2.5 V supply voltage.
A bulk-micromachined corner cube retroreflector (CCR) was designed and fabricated for free-space optical communications with ultra-low voltage operation and negligible power consumption. The proposed CCR was comprised of a bulk-micromachined vertical mirror which has two mutually orthogonal reflective surfaces and a horizontal mirror with piezoelectric actuator. The fabricated vertical and horizontal mirrors have sizes of 300 µm × 300 µm and 150 µm × 150 µm, respectively. The vertical mirror was fabricated using a double silicon-on-insulator wafer and the anisotropic wet etching of a (1 1 0) silicon wafer. The horizontal mirror was comprised of two supporting and one actuating lead zirconate titanate (PZT) cantilevers. The supporting cantilevers were utilized for the accurate angular alignment of the mirror by balancing and isolating the residual stresses occurring in the PZT cantilevers. The bottom-actuated mirror exhibited an angular displacement of 1.37° at an applied voltage of 5 V. The fabricated CCR exhibited a good angular misalignment of less than 0.35° and switching characteristics with an off-to-on-state transition of 163 µs and on-to-off-state transition of 276 µs at a rectangular input voltage and switching frequency of 10 V and 1 kHz, respectively. The fabricated CCR also exhibited a cutoff frequency of 2.5 kHz and could be digitally modulated up to about 5 kb s−1.
Oxide thin films were etched in a magnetically enhanced reactive ion etch system. The effects of CF 4 flowrate on etch rate, profile anisotropy and microtrench depth (MD) were examined. Apart from the direct current bias, important radicals such as F or CF collected with optical emission spectroscopy correlated with the etch rate and profile anisotropy. The etch rate was dominated by [F] driven etching rather than polymer deposition. In particular, the MD was strongly dependent on the profile angles. Typical MD occurred at positive profile angles. Larger positive profile angles resulted in a deeper MD, possibly due to enhanced ion collision with the sidewall. Profile angle variations played a crucial role in the interpretation of predicted MD variations with the radio frequency power.
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