Low-Loss Single and Differential Semi-Coaxial Interconnects in Standard CMOS Process

[[abstract]]The low-loss single semi-coaxial (S-SC) and differential semi-coaxial (D-SC) interconnects based on a standard 0.18-mum CMOS process are presented for the first time. Compared to the attenuation constant (alpha) reported for microstrip and CPW interconnects in CMOS process, the S-SC line shows the lowest loss of 0.90 dB/mm at 50 GHz. The D-SC line also presents a very low differential-mode alpha of ~1.00 dB/mm at high frequencies. The characteristics of D-SC lines for differential-mode and common-mode are also investigated in details based on the measured mixed-mode S-parameters[[fileno]]2030121030007[[department]]電機工程學

Microwave characteristics of liquid-crystal tunable capacitors

[[abstract]]This letter investigates the microwave characteristics of the liquid crystal tunable capacitors for the first time. With the dielectric anisotropy properties, the liquid crystal capacitors present very different characteristics compared to the semiconductor or MEMS tunable capacitors. A quality factor of 310 with a control voltage of 5 V was achieved at 4 GHz. A tuning range of 25.3% for the control voltages from 0 to 5 V was obtained at 5 GHz. The results demonstrate the potential applications of liquid crystals as dielectric materials for capacitors with high quality factors and wide tuning ranges at high frequencies, particularly suitable for the future flexible electronics with transparent substrates.[[fileno]]2030121010007[[department]]電機工程學

A comparison of low-frequency noise characteristics and noise sources in NPN and PNP InP-based heterojunction bipolar transistors

[[abstract]]Low-frequency noise characteristics of NPN and PNP InP-based heterojunction bipolar transistors (HBTs) were investigated. NPN HBTs showed a lower base noise current level (3.85 /spl times/ 10/sup -17/ A/sup 2//Hz) than PNP HBTs (3.10 /spl times/ 10/sup -16/ A/sup 2//Hz), but higher collector noise current level (7.16 /spl times/ 10/sup -16/ A/sup 2//Hz) than PNP HBTs (1.48 /spl times/ 10/sup -16/ A/sup 2//Hz) at 10 Hz under I/sub C/=1 mA, V/sub C/=1 V. The NPN devices showed a weak dependence I/sub C//sup 0.77/ of the collector noise current, and a dependence I/sub B//sup 1.18/ of the base noise current, while the PNP devices showed dependences I/sub C//sup 1.92/ and I/sub B//sup 1.54/, respectively. The dominant noise sources and relative intrinsic noise strength were found in both NPN and PNP InP-based HBTs by comparing the noise spectral density with and without the emitter feedback resistor. Equivalent circuit models were employed and intrinsic noise sources were extracted. The high base noise current of PNP HBTs could be attributed to the exposed emitter periphery and higher electron surface recombination velocity in P-type InP materials, while the relatively high collector noise current of NPN HBTs may be due to the noise source originating from generation-recombination process in the bulk material between the emitter and the collector.[[fileno]]2030121010006[[department]]電機工程學

Options for silicon based modulators

This paper provides an overview of modulators developed in the projects “HELIOS”, and “UK Silicon Photonics”, projects. We report low power cascaded modulators, integration with a modulator driver via wire bonding and via integration with BiCMOS technology