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  Millimeter wave switchUSPTO Application #: 20060028293Title: Millimeter wave switch Abstract: A switch selectively provides one of a first input signal at a first frequency and a second input signal at a second frequency to an output terminal with low insertion loss and high isolation between the first and second input signals. The first input signal is received at a first input terminal and the second input signal is received at a second input terminal. A switching element electrically connects the first input terminal and the output terminal to provide the first input signal to the output terminal in a first state and isolates the first input terminal from the output terminal in a second state. A bias line is electrically connected to provide a control signal to the switching element to select between the first state and the second state. An AC coupled transmission line is electrically connected to the second input terminal and electrically connected between the switching element and the output terminal. The control signal is provided through the AC coupled transmission line when the switching element is in the first state to isolate the second input terminal from the output terminal and provide the first input signal to the output terminal. The second input signal is provided DC coupled to the output terminal through the AC coupled transmission line when the switching element is in the second state. (end of abstract) Agent: Agilent Technologies, Inc. Legal Department, Dl 429 - Loveland, CO, US Inventors: Adam E. Robertson, Lon A. Dearden USPTO Applicaton #: 20060028293 - Class: 333104000 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20060028293. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] Switches have long been used in electrical circuit designs to isolate a portion of an electrical circuit. In its simplest form, a switch operates to allow a signal to pass from an input terminal to an output terminal in a "closed" position and to prevent the signal from passing from the input terminal to the output terminal in an "open" position. [0002] In the microwave and mm-wave frequency range, switches are used in instrumentation, communications, radar, fiber optic and many other systems that require high-frequency switching. For example, a switch can be used for pulse modulation, port isolation, transfer switching, high-speed switching, replacement of mechanical parts and other switch applications. [0003] There a number of commercially available high-frequency switches on the market today. However, these switches have all failed to simultaneously obtain high switch isolation greater than 15 dBm, high power handling above 24 dBm and low insertion loss of a fraction of a dB from DC to mm-wave frequencies. For example, high-frequency switches employing field-effect transistors (FETs) typically are unable to handle high frequencies in the mm-wave range and/or high power above 24 dBm. In the alternative, FET-based solutions may have high insertion loss. In addition, waveguide-based switches are difficult to integrate and lack the required bandwidth coverage to DC. Furthermore, coupling-based diplexers typically have poor isolation and high insertion loss at the cross-over frequency. [0004] Therefore, what is needed is a switch capable of achieving high switch isolation, high power handling and low insertion loss from DC to mm-wave frequencies. SUMMARY OF THE INVENTION [0005] Embodiments of the present invention provide a switch for selectively providing one of a first input signal at a first frequency and a second input signal at a second frequency to an output terminal. The first input signal is received at a first input terminal and the second input signal is received at a second input terminal. A switching element electrically connects the first input terminal and the output terminal to provide the first input signal to the output terminal in a first state and isolates the first input terminal from the output terminal in a second state. A bias line is electrically connected to provide a control signal to the switching element to select between the first state and the second state. An AC coupled transmission line is electrically connected to the second input terminal and electrically connected between the switching element and the output terminal. The control signal is provided through the AC coupled transmission line when the switching element is in the first state to isolate the second input terminal from the output terminal and provide the first input signal to the output terminal. The second input signal is provided DC coupled to the output terminal through the AC coupled transmission line when the switching element is in the second state. [0006] In one embodiment, the switching element is a series switching element and a shunt switching element is connected to the AC coupled transmission line. The control signal is provided to the shunt switching element through the AC coupled transmission line when the series switching element is in the first state to isolate the second input terminal from the output terminal and provide the first input signal to the output terminal through the AC coupled transmission line. The shunt switching element is separated from the AC coupled transmission line by a distance less than or equal to 70 .mu.m. However, it should be understood that in other embodiments, the separation distance is designed to maintain sufficient isolation. In a further embodiment, the shunt switching element includes two shunt switching elements. A first shunt switching element is connected to a first portion of the AC coupled transmission line connected between the series switching element and ground through the first shunt switching element and a second shunt switching element is connected to a second portion of the AC coupled transmission line connected between the output terminal and the second input terminal. [0007] In another embodiment, the AC coupled transmission line is a capacitive element having a first plate and a second plate separated by a dielectric. The first plate is formed of a first metal layer and the second metal plate is formed of a second metal layer. In a further embodiment, the AC coupled transmission line is a quarter wavelength transmission line to make the shunt switching element appear as an open circuit to the first input signal and a short circuit to the second input signal. In still a further embodiment, the first input signal is at a first frequency greater than or equal to 20 GHz and the second input signal is at a second frequency between DC and 20 GHz. [0008] Advantageously, embodiments of the present invention uses a simplistic biasing scheme by using a single bias line for all switching elements and biasing the shunt switching elements through the second metal layer of the AC coupled transmission line. In addition, the power handling of the switch is improved to at least 33 dBm when using PIN diodes. Moreover, low insertion loss and high isolation is achieved by placing the shunt switching elements as close as possible to the AC coupled transmission line. Likewise, improved isolation is achieved by using two shunt switching elements on either side of the AC coupled transmission line. Furthermore, the invention provides embodiments with other features and advantages in addition to or in lieu of those discussed above. Many of these features and advantages are apparent from the description below with reference to the following drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0009] The disclosed invention will be described with reference to the accompanying drawings, which show exemplary embodiments of the invention and which are incorporated in the specification hereof by reference, wherein: [0010] FIG. 1 is a block diagram of an exemplary DC to mm-wave frequency switch, in accordance with embodiments of the present invention; [0011] FIG. 2 is a schematic diagram of an exemplary DC to mm-wave frequency switch, in accordance with embodiments of the present invention; [0012] FIG. 3A is a schematic diagram of a circuit model for the switch in a forward bias condition; [0013] FIG. 3B is a schematic diagram of a circuit model for the switch in a zero bias or reverse bias condition; [0014] FIG. 4 is a circuit layout of the switch, in accordance with embodiments of the present invention; [0015] FIG. 5 is a cross-sectional view of the switch of FIG. 4, in accordance with one embodiment of the present invention; [0016] FIG. 6 is a cross-sectional view of the switch fabricated using an integrated circuit design; [0017] FIG. 7 is a flow chart illustrating an exemplary process for fabricating the switch, in accordance with embodiments of the present invention; and [0018] FIG. 8 is a flow chart illustrating an exemplary process for operating the switch, in accordance with embodiments of the present invention. DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS [0019] FIG. 1 is a block diagram of an exemplary DC to mm-wave frequency switch 100, in accordance with embodiments of the present invention. The switch 100 is a part of a switching system 10. For example, in one embodiment, switching system 10 can be an output switch of a 44 GHz up-converter. System 10 includes two signal sources 20 and 30. A first signal source 20 supplies a first signal at a first frequency to a first input terminal 110 of switch 100. A second signal source 30 supplies a second signal at a second frequency to a second input terminal 120 of switch 100. Switch 100 selectively provides the first signal or the second signal to an output terminal 130 of switch 100. In one embodiment, the first frequency is a high frequency greater than or equal 20 GHz and the second frequency is a low frequency between DC and 20 GHz. However, it should be understood that in other embodiments, the first and second frequencies can be any two frequencies from which switch 100 selects. [0020] FIG. 2 is a schematic diagram of an exemplary DC to mm-wave frequency switch 100, in accordance with embodiments of the present invention. Switch 100 includes input terminals 110 and 120 and output terminal 130. A series switching element 240 is connected to first input terminal 110. Series switching element 240 is shown as a single PIN diode. However, it should be understood that in other embodiments, additional PIN diodes can be added to form series switching element 240. In addition, it should be understood that other circuit elements can be used as series switching element 240. For example, series switching element 240 can include one or more P-N diodes, Schottky diodes, field-effect transistors (FETs), PNP transistors, NPN transistors or any other type of circuit element. Continue reading... Full patent description for Millimeter wave switch Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Millimeter wave switch patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Millimeter wave switch or other areas of interest. ### Previous Patent Application: Circuit for connection of at least two signal sources with at least one signal output Next Patent Application: Line-doubler delay circuit Industry Class: Wave transmission lines and networks ### FreshPatents.com Support Thank you for viewing the Millimeter wave switch patent info. 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