1. Statement of the Technical Field
The inventive arrangements relate to switches, such as broad-band, low-loss radio frequency (RF) microelectromechanical systems (MEMS) switches.
2. Description of Related Art
Communications systems, such as broadband satellite communications systems, commonly operate at anywhere from 300 MHz (UHF band) to 300 GHz (mm-wave band). Such examples include TV broadcasting (UHF band), land mobile (UHF band), global positioning systems (GPS) (UHF band), meteorological (C band), and satellite TV (SHF band). Most of these bands are open to mobile and fixed satellite communications. Higher frequency bands typically come with larger bandwidths, which yield higher data rate operation. Switching devices used in these types of systems need to operate with relatively low losses, e.g., less than one decibel (dB) of insertion loss, at these ultra-high frequencies.
Miniaturized switches such as monolithic microwave integrated circuit (MMIC) and MEMS switches are commonly used in broadband communications systems due to stringent constraints imposed on the components of such systems, particularly in satellite-based applications. Currently, the best in class switches operate at 40 GHz with culumative attributes such as insertion losses of approximately 0.6 dB, return losses of approximately 13 dB, and isolation levels of approximately 40 dB.
Three-dimensional microstructures can be formed by utilizing sequential build processes. For example, U.S. Pat. Nos. 7,012,489 and 7,898,356 describe methods for fabricating coaxial waveguide microstructures. These processes provide an alternative to traditional thin film technology, but also present new design challenges pertaining to their effective utilization for advantageous implementation of various devices such as miniaturized switches.
Embodiments of switches include a ground housing; a first electrical conductor, and a second electrical conductor spaced apart from the first electrical conductor. The first and second electrical conductors are suspended within the ground housing on electrically-insulative supports. The switches further include a contact element having an electrically-insulative first portion, an electrically-conductive second portion, and an electrically-insulative third portion. The first and third portions of the contact element adjoin the second portion. The contact element is configured for movement between a first position at which the second portion of the contact element is spaced apart and electrically isolated from the first and second electrical conductors, and a second position at which the second portion of the contact element contacts the first and second electrical conductors.
Other embodiments of switches include a ground plane, and a housing electrically connected to the ground plane and having one or more inner surfaces that define a channel. The switches also include a first and a second electrical conductor suspended within the channel, spaced apart from the one or more inner surfaces of the housing by a first air gap, and spaced apart from each other by a second air gap. The switches further include a contact element mounted on the ground plane and being operative to move between a first position at which an electrically-conductive portion of the contact element is spaced part and electrically isolated from the first and second electrical conductors by respective third and forth air gaps, and a second position at which the electrically-conductive portion of the contact element contacts the first and second electrical conductors and bridges the second air gap to establish electric contact between the first and second electrical conductors. The contact element further includes a first electrically insulative portion configured to electrically isolate the electrically-conductive portion of the contact element from the ground plane.
In accordance with further aspects of the inventive concepts claimed herein, processes for making switches include selectively depositing a first layer of an electrically-conductive material on a substrate to form at least a portion of a ground plane and an actuator. The processes further include selectively depositing a second layer of the electrically-conductive material on the first layer and the substrate to form or further form the actuator, a portion of a housing, and a portion of a mount for a contact element configured to electrically connect a first and a second electrical conductor on a selective basis when actuated by the actuator. The processes also include selectively depositing a portion of a third layer of the electrically-conductive material on the first and second layers and the substrate to form or further form the housing, the actuator, the mount, the contact element, and the first and second electrical conductors.
Embodiments will be described with reference to the following drawing figures, in which like numerals represent like items throughout the figures and in which:
The invention is described with reference to the attached figures. The figures are not drawn to scale and they are provided merely to illustrate the instant invention. Several aspects of the invention are described below with reference to example applications for illustration. It should be understood that numerous specific details, relationships, and methods are set forth to provide a full understanding of the invention. One having ordinary skill in the relevant art, however, will readily recognize that the invention can be practiced without one or more of the specific details or with other methods. In other instances, well-known structures or operation are not shown in detail to avoid obscuring the invention. The invention is not limited by the illustrated ordering of acts or events, as some acts may occur in different orders and/or concurrently with other acts or events. Furthermore, not all illustrated acts or events are required to implement a methodology in accordance with the invention.
The figures depict a MEMS switch 10. The switch 10 can selectively establish and disestablish electrical contact between a first and second electronic component (not shown) electrically connected thereto. The switch 10 has a maximum height (“z” dimension) of approximately 1 mm; a maximum width (“y” dimension) of approximately 3 mm; and a maximum length (“x” dimension) of approximately 3 mm. The switch 10 is described as a MEMS switch having these particular dimensions for exemplary purposes only. Alternative embodiments of the switch 10 can be scaled up or down in accordance with the requirements of a particular application, including size, weight, and power (SWaP) requirements.
The switch 10 comprises a contact portion 12, an actuator portion 14, and a contact element in the form of a shuttle 16, as shown in
The switch 10 comprises a substrate 26 formed from a dielectric material such as silicon (Si), as shown in
The contact portion 12 of the switch 10 includes an electrically-conductive ground housing 28 disposed on the ground plane 27, as illustrated in
The contact portion 12 further includes an electrically-conductive first inner conductor 34 and an electrically-conductive second inner conductor 36 each having a substantially rectangular cross section, as shown in
The first and second inner conductors 34, 36 are positioned within the channel 30, as shown in
The first inner conductor 34 and the surrounding portion of the ground housing 28 define an input port 42 of the contact portion 12. The second inner conductor 36 and the surrounding portion of the ground housing 28 define an output port 44 of the contact portion 12. The first electronic device can be electrically connected to the input port 42. The second electronic device can be electrically connected to the output port 44. The first and second electronic devices can be integrated with the respective input and output ports 42, 44 by, for example, hybrid integration methods such as wire-bonding and flip-chip bonding.
The first and second inner conductors 34, 36 are each suspended within the channel 34 on electrically-insulative tabs 37, as illustrated in
The shuttle 16 has an elongated body 52 that extends substantially in the “y” direction, as shown in
The switch 10 includes a first mount 56a and a substantially identical second mount 56b. The first mount 56a is disposed on the portion of the ground plane 27 associated with the contact portion 12 of the switch 10, as shown in
The first and second mounts 56a, 56b each include a base 62 that adjoins the ground plane 27, and a beam portion 64 that adjoins the base 62. Each base 62 is formed as part of the second and third layers of the electrically-conductive material. The beam portions 64 are formed as part of the third layer of the electrically-conductive material. It should be noted that the configuration of the beam portions 64 is application-dependent, and can vary with factors such as the amount of space available to accommodate the beam portions 64, the required or desired spring constant of the beam portions 64, etc. Accordingly, the configuration of the beam portions 64 is not limited to that depicted in
An end of the first portion 53a of the shuttle 16 adjoins the beam portion 64 of the first mount 56a, as depicted in
The beam portions 64 are configured to deflect so as to facilitate movement of the shuttle 16 in its lengthwise direction, i.e., in the “y” direction. In particular, the shuttle 16 is in its open position when the beam portions 64 are in their neutral, or un-deflected positions, as depicted in
The second portion 53b of the shuttle 16 includes two projections in the form of fingers 74, as shown in
Movement of the shuttle 16 to its closed position causes each of the fingers 74 to traverse and close the associated air gap 76 as the finger 74 moves into contact with its associated first or second inner conductor 34, 36 as shown in
The air gaps 44, 76 act as a dielectric insulator that electrically isolates the first inner conductor 34 from the second inner conductor 38 when the shuttle 16 is in its open position. As shown in
By bridging the air gaps 76 when the shuttle 16 is in the closed position, as shown in
The second portion 53b of the body 52 adjoins the electrically-insulative first and third portions 53a, 53c of the body 52, as depicted in FIGS. 1 and 3-6B. The first portion 53a electrically isolates the second portion 53b from the electrically-conductive first mount 56a. The third portion 53c electrically isolates the second portion 53b from the electrically-conductive fourth portion 53d. Thus, electrical isolation of the signal path through the switch 10 is achieved by way of the air gaps 50 between the first and second inner conductors 34, 36 and the adjacent internal surfaces of the ground housing 28; and by way of the first and third portions 53a, 53c of the shuttle 16.
The actuator portion 14 of the switch 10 includes a body 80, a first lead 82a, and a second lead 82b, as shown in
The top portion 88 of the body 80 includes a first half 90a and a second half 90b, as depicted in
The fourth portion 53d of the body 52 of the shuttle 16 includes six projections in the form of fingers 96 that extend substantially in the “x” direction as illustrated in
The first and second leads 82a, 82b of the actuating portion 14 are disposed on the substrate 26 as shown in
Subjecting the first and second leads 82a, 82b to a voltage causes the shuttle 16 to move from its open to its closed position, and to remain in the closed position, due to the resulting electrostatic attraction between the shuttle 16 and the actuator portion 14, as follows. As discussed above, the first portion 53a of the shuttle 16 adjoins the beam portion 64 of the first mount 56a, and the fourth portion 53d of the shuttle 16 adjoins the beam portion 64 of the second mount 56b, so that the shuttle 16 is suspended from the first and second mounts 56a, 56b. The beam portions 64 are in their neutral or un-deflected positions when the shuttle 16 is in its open position, as depicted in
Subjecting the first and second leads 82a, 82b of the actuator portion 14 to a voltage potential results in energization of the fingers 92, as discussed above. The energized fingers 92 act as electrodes, i.e., an electric field is formed around each finger 92 due the voltage potential to which the finger 92 is being subjected. Each of the energized fingers 92 is positioned sufficiently close to its associated finger 96 on the grounded shuttle 16 so as to subject the associated finger 96 to the electrostatic force resulting from the electric field around the finger 92. The electrostatic force attracts the finger 96 to its corresponding finger 92.
The net electrostatic force acting on the six fingers 96 urges the shuttle 16 in the “+y” direction. The beam portions 64 of the first and second mounts 56a, 56b, which were in their neutral or un-deflected state prior to energization of the fingers 92, are configured to deflect in response to this force as shown in
The relationship between the amount of deflection and the voltage applied to the actuator portion 14 is dependent upon the stiffness of the beam portions 64, which in turn is dependent upon factors that include the shape, length, and thickness of the beam portions 64, and the properties, e.g., Young's modulus, of the material from which the beam portion 64 are formed. These factors can be tailored to a particular application so as to minimize the required actuation voltage, while providing the beam portion 64 with sufficient strength for the particular application; with sufficient stiffness to tolerate the anticipated levels shock and vibration; and with sufficient resilience to facilitate the return of the shuttle 16 to its open position when the voltage potential to the actuator portion 14 is removed.
The actuator portion 14 can have a configuration other than that described above in alternative embodiments. For example, suitable comb, plate, or other types of electrostatic actuators can be used in the alternative. Moreover, actuators other than electrostatic actuators, such as thermal, magnetic, and piezoelectric actuators, can also be used in the alternative.
As discussed above, electrical isolation of the signal path through the switch 10 is achieved by way of the air gaps 50 between the first and second inner conductors 34, 36 and the adjacent internal surfaces of the ground housing 28; and by way of the first and third portions 53a, 53c of the shuttle 16. The electrical isolation is believed to result in very favorable signal-transmission characteristics for the switch 10. For example, based on finite element method (FEM) simulations, the insertion loss of the switch 10 at 40 GHz is predicted to be approximately 0.09 dB, which is believed to be an improvement of at least approximately 85% over the best in class switches of comparable capabilities. The return loss of the switch 10 at 40 GHz is predicted to be approximately 24 dB, which is believed to be an improvement of at least approximately 85% over the best in class switches of comparable capabilities. The isolation of the switch 10 at 40 GHz is predicted to be approximately 40 dB, which is approximately equal to the isolation achieved by the best in class switches of comparable capabilities.
Moreover, because the switch 10 incorporates a relatively large amount of copper in comparison to other types of MEMS switches, which typically are based on thin-film technologies, the switch 10 is believed to have substantially higher power-handling capability and linearity, with respect to the transmission of both DC and RF signals, than other types of switches of comparable size. Also, the configuration of the switch 10 makes it capable of being monolithically integrated into systems through the routing of micro-coax lines. Moreover, the switch 10 can be fabricated or transferred onto a suite of various exotic substrates.
The switch 10 and alternative embodiments thereof can be manufactured using known processing techniques for creating three-dimensional microstructures, including coaxial transmission lines. For example, the processing methods described in U.S. Pat. Nos. 7,898,356 and 7,012,489, the disclosure of which is incorporated herein by reference, can be adapted and applied to the manufacture of the switch 10 and alternative embodiments thereof.
The switch 10 can be formed in accordance with the following process which is depicted in
Electrically-conductive material is subsequently deposited on the unmasked, i.e., exposed, portions of the substrate 26 to a predetermined thickness, to form the first layer of the electrically-conductive material as shown in
The second layer of the electrically conductive material forms portions of the sides of the ground housing 28; another portion of each leg 86; another portion of the first and second leads 82a, 82b; and a portion of each of the first and second mounts 56a, 56b. A second photoresist layer 100 is applied to the partially-constructed switch 10 by patterning additional photoresist material in the desired shape of the second photoresist layer over the partially-constructed switch 10 and over the previously-applied first photoresist layer, utilizing a mask or other suitable technique, so that so that the only exposed areas on the partially-constructed switch 10 and the partially-constructed cover 100 correspond to the locations at which the above-noted portions of the switch 10 are to be located, as shown in
The dielectric material that forms the tabs 37 is deposited and patterned on top of the previously-formed photoresist layer as shown in
The third layer of the electrically conductive material forms additional portions of the sides of the ground housing 28; the second and fourth portions 53b, 53d of the body 52 of the shuttle 16; additional portions of each of the first and second mounts 56a, 56b; and the top portion 88 of the body 80 of the actuator portion 14. A third photoresist layer 102 is applied to the partially-constructed switch 10 by patterning additional photoresist material in the desired shape of the third photoresist layer over the partially-constructed switch 10 and over the second photoresist layer, utilizing a mask or other suitable technique, so that so that the only exposed areas on the partially-constructed switch 10 correspond to the locations at which the above-noted components are to be located, as shown in
The fourth and fifth layers of the electrically conductive material form, respectively, additional portions of the sides of the ground housing 28, and the top of the ground housing 28. The fourth and fifth layers are formed in a manner similar to the first, second, and third layers. In particular, the fourth and fifth layers are formed by applying additional photoresist material to the previously-formed layers, utilizing a mask or other suitable technique, to form fourth and fifth photoresist layers 104, 106 as shown respectively in FIGS. 13A/13B and 15A/15B, and then depositing additional electrically-conductive material to the exposed areas to form the fourth and fifth layers as shown respectively in FIGS. 14A/14B and 16A/16B. The upper surfaces of the newly-formed portions of the switch 10 can be planarized after the application of each of the fourth and fifth layers.
The photoresist material remaining from each of the masking steps can then be released or otherwise removed after the fifth layer has been applied as depicted in
This application is a continuation-in-part of and claims priority to copending non-provisional application Ser. No. 13/592,435, filed on Aug. 23, 2012, and is hereby incorporated by reference in its entirety.
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Number | Date | Country | |
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20140054143 A1 | Feb 2014 | US |
Number | Date | Country | |
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Parent | 13592435 | Aug 2012 | US |
Child | 13672863 | US |