This paper presents a novel concept of a millimeter-wave waveguide switch based on a microelectromechanical (MEMS)-reconfigurable surface with insertion loss and isolation very similar to high performance but bulky rotary waveguide switches, despite its thickness of only 30 m. A set of up to 1470 micromachined cantilevers arranged in vertical columns are actuated laterally by on-chip integrated MEMS comb-drive actuators, to switch between the transmissive state and the blocking state. In the blocking state, the surface is reconfigured so that the wave propagation is blocked by the cantilever columns short-circuiting the electrical field lines of the TE mode. A design study has been carried out identifying the performance impact of different design parameters. The RF measurements (60-70 GHz) of fabricated, fully functional prototype chips show that the devices have an isolation between 30 and 40 dB in the OFF state and an insertion loss between 0.4 and 1.1 dB in the ON state, of which the waveguide-assembly setup alone contributes 0.3 dB. A device-level yield analysis was carried out, both by simulations and by creating artificial defects in the fabricated devices, revealing that a cantilever yield of 95% is sufficient for close-to-best performance. The actuation voltage of the active-opening/active-closing actuators is 40-44 V, depending on design, with high reproducibility of better than 0.0605 V . Lifetime measurements of the all-metal, monocrystalline-silicon core devices were carried out for 14 h, after which 4.3 million cycles were achieved without any indication of degradation. Furthermore, a MEMS-switchable waveguide iris based on the reconfigurable surface is presented.Index Terms-Microelectromechanical (MEMS) components and techniques, MEMS switches, microwave switch, millimeter-waves, reconfigurable surface, Radio frequency MEMS (RF MEMS), waveguide switch.
This paper presents for the first time a novel concept of a MEMS waveguide switch based on a reconfigurable surface, whose working principle is to short-circuit or to allow for free propagation of the electrical field lines of the TE10 mode of a WR-12 rectangular waveguide. This transmissive surface is only 30µm thick and consists of up to 1260 reconfiguring cantilevers in the waveguide cross-section, which are moved simultaneously by integrated MEMS comb-drive actuators. For the first fabrication run, the yield of these reconfigurable elements on the chips was 80-86%, which still was good enough for resulting in a measured insertion loss in the open state of better than 1dB and an isolation of better than 20dB for the best designs, very wideband from 62 to 75GHz. For 100% fabrication yield, HFSS simulations predict that an insertion loss in the open state of better than 0.1dB and an isolation of better than 30dB in the closed state are possible for designs with 800 and more contact points for this novel waveguide switch concept. RF MEMS; reconfigurable surface; waveguide switch
This paper presents for the first time a novel concept of a microelectromechanical systems (MEMS) waveguide switch based on a reconfigurable surface, whose working principle is to block the wave propagation by short-circuiting the electrical field lines of the TE10 mode of a WR-12 rectangular waveguide. The reconfigurable surface is only 30 µm thick and consists of up to 1260 micromachined cantilevers and 660 contact points in the waveguide cross-section, which are moved simultaneously by integrated MEMS comb-drive actuators. Measurements of fabricated prototypes show that the devices are blocking wave propagation in the OFF-state with over 30 dB isolation for all designs, and allow for transmission of less than 0.65 dB insertion loss for the best design in the ON-state for 60–70 GHz. Furthermore, the paper investigates the integration of such microchips into WR-12 waveguides, which is facilitated by tailor-made waveguide flanges and compliant, conductive-polymer interposer sheets. It is demonstrated by reference measurements where the measured insertion loss of the switches is mainly attributed to the chip-to-waveguide assembly. For the first prototypes of this novel MEMS microwave device concept, the comb-drive actuators did not function properly due to poor fabrication yield. Therefore, for measuring the OFF-state, the devices were fixated mechanically.
This paper investigates a new concept of waveguide-based W-band phase shifters for applications in phased array antennas. The phase-shifters are based on a tuneable bilateral finline bandpass filter with 22 MEMS (microelectromechanical system) switching elements, integrated into a custom-made WR-12 waveguide with a replaceable section, whose performance is also investigated in this paper. The individual phase states are selected by changing the configuration of the switches bridging the finline slot in specific positions; this leads to 4 discrete phase states with an insertion loss predicted by simulations better than 1 dB, and a phase shift span of about 270°. MEMS chips have been fabricated in fixed positions, on a pair of bonded 300 µm high resistivity silicon substrates, to prove the principle, i.e. they are not fully functional but contain all actuation and biasing-line elements. The measured phase states are 0°, 56°, 189°, and 256°, resulting in an effective bit resolution of 1.78 bits of this nominal 2-bit phase-shifter at 77 GHz. The measured insertion loss was significantly higher than the simulated value which is assumed to be attributed to narrow-band design of the devices as the influence of fabrication and assembly tolerances is shown to be negligible from the measurement results.
This paper presents a concept of a waveguide single-pole single-throw (SPST) switch based on a MEMSreconfigurable surface. A set of vertical columns, split into two groups of movable and fixed sections which can be actuated laterally by integrated MEMS comb-drive actuators, allows for the transition between the transmissive and the blocking state. In the totally-blocking state, the vertical columns inhibit the wave propagation by short-circuiting the electrical field lines of the predominant TE10 mode. The paper reports on the integration method for fabricated chips into a WR-12 waveguide by using tailor-made flanges. The RF measurement of fabricated chips show that devices have better than 30 dB isolation in the OFF state and better than 0.65 dB insertion loss in the ON state for 60-70 GHz, which is mainly attributed to the integration into the waveguide and the measurement assembly setup. The actuation voltage is 44 V, and life-time measurements were carried out for 14 hours after which 4.3 million cycles were achieved without any indication on degradation.Index Terms -RF MEMS, reconfigurable surface, waveguide switch, microwave switch.
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