Yuhao Liu

Substrate-integrated octave-tunable combline bandstop filter with surface mount varactors

This paper presents an octave-tunable two-pole bandstop filter with tuning range of 0.56-1.18 GHz (2.1:1 tuning ratio). The bandstop filter is designed with two highly loaded combline resonators with surface mounted solid state varactors. Theoretical analysis and modeling along with full wave simulation is presented in agreement with measured data. The measured peak attenuation in the stopband is approximately 27 dB at 1.18 GHz and is approximately 7 dB at 0.56 GHz. However, a minimum attenuation of at least 10 dB is maintained above 0.65 GHz (1.82:1 tuning ratio).

High-Efficiency Micromachined Sub-THz Channels for Low-Cost Interconnect for Planar Integrated Circuits

This paper presents for the first time the design, fabrication, and demonstration of a micromachined silicon dielectric waveguide based sub-THz interconnect channel for a high-efficiency, low-cost sub-THz interconnect, aiming to solve the long-standing intrachip/interchip interconnect problem. Careful studies of the loss mechanisms in the proposed sub-THz interconnect channel are carried out to optimize the design. Both theoretical and experimental results are provided with good agreement. To guide the channel design, a new figure of merit is also defined. The insertion loss of this first prototype with a 6-mm-long interconnect channel is about 8.4 dB at 209.7 GHz, with a 3-dB bandwidth of 12.6 GHz.

Low-loss and Broadband G-Band Dielectric Interconnect for Chip-to-Chip Communication

This paper presents a novel dielectric waveguide based G-band interconnect. By using a new transition of microstrip line to dielectric waveguide, the interconnect achieves low insertion loss and wide bandwidth. The measured minimum insertion loss is 4.9 dB with 9.7 GHz 1-dB bandwidth. Besides, the structure is based on standard micromachined processing and easy to integrate with conventional packaging.

Extension of the Hot-Switching Reliability of RF-MEMS Switches Using a Series Contact Protection Technique

This paper presents a design methodology to drastically improve the hot-switching reliability of contact-type radio frequency microelectromechanical system (RF-MEMS) switches. In the proposed design, sacrificial contacts are placed in parallel with low-resistance contacts to significantly reduce the electric field across the latter. The lower field strength drastically reduces the contact degradation associated with field-induced material transfer. Theoretical and numerical modeling shows that the proposed protection scheme introduces minimal, if any, impact on the RF performance of the switch. To realize the protection scheme, we introduce a novel mechanical design that allows the correct protection actuation sequence to be realized using a single actuator and bias electrode. As a demonstration, several 0-40-GHz RF-MEMS switches are fabricated using a robust copper sacrificial layer technique. Compared with unprotected switches, the protected switch design exhibits over 100 times improvement in the hot-switching lifetime. In particular, we demonstrate a 100-150 million cycle lifetime at 1-W hot switching and 50 million cycles at 2-W hot switching before catastrophic failure, measured in an open-air lab environment. Further optimization of the structural design and contact materials is likely to further increase the hot-switching lifetime.

High-Power High-Isolation RF-MEMS Switches With Enhanced Hot-Switching Reliability Using a Shunt Protection Technique

This paper presents a shunt protection technique to improve the hot-switching reliability of metal-contact radio-frequency microelectromechanical systems (RF-MEMS) switches. The proposed technique places shunt protection contacts in front of the main contact of an RF-MEMS metal contact switch to block RF signal while the main contact is switching ON or OFF. The shunt protection contact creates a local cold-switching condition for the main contact to increase the lifetime of the switch under hot-switching condition. The shunt protection technique can also increase the overall isolation of the switch. To demonstrate the technique, RF-MEMS switches with and without shunt protection were fabricated using all metal process. Compared with the unprotected switch, the protected switch has longer lifetime under hot-switching condition. The protected switch has >100-million cycles and up to 500-million cycles lifetime under the 1-W hot-switching condition, measured in open-air laboratory environment. Besides, the isolation of the shunt-protected switch is 70 dB at 1.0 GHz and 36 dB at 40 GHz, and the insertion loss is 0.30 dB at 1.0 GHz and 0.43 dB at 40 GHz.

Design of low phase-noise voltage-controlled oscillator using tunable evanescent-mode cavity

In this paper, a low phase-noise voltage-controlled oscillator using tunable evanescent-mode cavity is designed, fabricated, and measured. The oscillator is tuned by lumped element varactors placed on the top surface of a substrate-integrated evanescent-mode cavity. The tuning range of the oscillator is 783.6-976.8 MHz with peak output power of 6.97 dBm at 943.2 MHz. Over the tuning frequency the oscillator has a phase noise from -103.8 to -119.4 dBc/Hz at 100 kHz offset frequency and from -141.8 to -152.3 dBc/Hz at 1 MHz offset frequency. The resonator is compatible with RF MEMS tuner to yield a higher resonator Q and better phase noise performance.

Single-actuator shunt-series RF-MEMS switch

This paper presents the design and experimental validation of a novel high isolation RF MEMS ohmic contact switch. The bending mechanics of a single cantilever beam is used to realize the typical series/shunt switch design to improve high isolation. In the OFF state the switch exhibits an isolation of 20 dB at 10 GHz and 14.7 dB at 20 GHz. When shunt contact is closed the isolation improves to 33 dB at 10 GHz and 22.3 dB at 20 GHz. In the ON state the insertion loss is 0.03 dB at 10 GHz and 0.10 dB at 20 GHz. In addition to the excellent loss/isolation performance, the switch holds great promise for improving power handling capability under hot-switching conditions.

Monolithic AlN MEMS-CMOS resonant transformer for wake-up receivers

A monolithic piezoelectric MEMS-CMOS resonant transformer that can be used in ultra-low-power high-efficiency RF sensing applications is presented for the first time. The MEMS-CMOS resonant transformer is based on a 59 MHz 2-port Aluminum Nitride (AlN) Contour Mode Resonator (CMR) bonded to a 0.18 μm NMOS-based rectifier for voltage boosting and RF-to-DC conversion. The integrated device is fabricated in a foundry-based process by conductive eutectic wafer bonding. To amplify the voltage, the AlN CMR is designed to attain a large quality factor (Q=1150) and a relatively low dielectric capacitance (C0=1.51 pF) in relation to the number of rectifier stages (n=20). As a result, a ten-fold voltage gain MEMS-CMOS resonant transformer is demonstrated in this work.

A novel RF-MEMS shunt capacitive switch design for dielectric charging mitigation

This paper reports on the design, fabrication, and measurement of a new electromechanical implementation for the mitigation of dielectric charging on the signal line and substrate for RF-MEMS shunt switches. Electrostatically shielded, externally-positioned, dielectric-less actuation electrodes with mechanical stoppers are fabricated above the MEMS bridge to isolate the RF and substrate dielectrics from the DC biasing electric fields. In the ON-state, the switch exhibits a measured insertion loss of -0.32dB at 10GHz and -0.69 dB at 20GHz. In the OFF-state, the measured isolation is 15dB at 10GHz and 24dB at 20GHz.

Micromachined silicon channels for THz interconnect

This paper, for the first time, presents planar silicon process compatible interconnect channels, which can be extended to THz frequencies for high performance interconnect systems to fill the long-standing intra-/inter- chip interconnect gap.