News Column

Patent Issued for RF Switches

June 4, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- Acco Semiconductor, Inc. (Sunnyvale, CA) has been issued patent number 8731485, according to news reporting originating out of Alexandria, Virginia, by VerticalNews editors.

The patent's inventor is Masliah, Denis A. (St.-Germain en Laye, FR).

This patent was filed on July 19, 2013 and was published online on May 20, 2014.

From the background information supplied by the inventors, news correspondents obtained the following quote: "The present invention relates generally to semiconductor devices and more particularly to radio frequency (RF) switches for use in RF applications.

"FIG. 1 illustrates an exemplary transceiver 100 of the prior art coupled to an antenna 110. The transceiver 100 includes a switch 120, such as a solid-state single pole double throw switch, configured to switch between a power amplifier 130 and a receiver amplifier 140. The transceiver 100 further includes filters 150 disposed between the switch 120 and the antenna 110.

"In the prior art, the antenna 110 is sometimes coupled to multiple circuits each comprising a switch 120, power amplifier 130, and receiver amplifier 140, where each such circuit is dedicated to a particular frequency band. Here, the transceiver 100 handles one or more high bands and/or one or more low bands, for example. In these instances the filters 150 selectively remove frequencies outside of the particular frequency band to which the circuit is dedicated.

"Most of the power being produced by the power amplifier 130 is at some desired frequency, however, some power also goes into harmonics of that primary frequency. Accordingly, another function of the filters 150 is to remove the higher harmonics of the transmitted signal so that the antenna 110 only transmits at the desired frequency.

"In operation, the transceiver 100 transmits an RF signal by coupling the power amplifier 130 to the antenna 110 and receives an RF signal by coupling the receiver amplifier 140 to the antenna 110. It will be appreciated, however, that since the power amplifier 130 and the receiver amplifier 140 are both coupled to the same switch 120, the switch 120 can unintentionally couple the high-power transmitted RF signal onto the receiver transmission line 160, an effect known as parasitic leakage.

"Additionally, the switch 120 needs to be able to handle the high voltages produced by the power amplifier, in the range of about 15 to 30 volts. Such voltages are too high for metal oxide semiconductor (MOS) switches to withstand."

Supplementing the background information on this patent, VerticalNews reporters also obtained the inventor's summary information for this patent: "Exemplary articles of manufacture of the present invention comprise semiconductor devices, transceivers, and communication devices. In various embodiments, the articles of manufacture are implemented entirely on silicon substrates using Complementary Metal Oxide Semiconductor (CMOS) technologies. An exemplary article of manufacture comprises a power amplifier, a receiver amplifier, and first and second transmission lines. The first transmission line extends between the power amplifier and an antenna port, and the second transmission line extends between the receiver amplifier and the antenna port. The exemplary embodiment also comprises first and second valves. The first valve is configured to change an impedance of the first transmission line and the second valve is configured to change an impedance of the second transmission line. In the exemplary embodiment the first and second valves are controllable such that when one is open the other is closed. In various embodiments, the article of manufacture additionally comprises control logic configured to oppositely control the first and second valves. In those embodiments in which the article of manufacture comprises a communications device, for example, the article of manufacture can further comprise an antenna coupled to the antenna port.

"In various embodiments, the first valve and/or the second valve can include a double-gate semiconductor device that is controllable to couple and decouple the valve to and from ground in order to switch the valve on and off, respectively. Also in various embodiments, the first transmission line includes a transmission line segment and the first valve and/or the second valve can include first and second lines both joined to the first transmission line at a node. In these embodiments, the first line includes a first line segment disposed along the segment of the transmission line, and the second line includes a second line segment disposed along the segment of the transmission line.

"The exemplary article of manufacture, in some embodiments, does not include a filter between the power amplifier and the antenna to remove harmonics of the primary frequency since the overall circuit gives rise to a strong attenuation of frequencies on the first transmission line at frequencies above the primary frequency of the power amplifier even while the attenuation around the operating frequency on the first transmission line is inconsequential. In various embodiments, the first and/or second valves have an insertion loss of less than 0.5 dB. Also in various embodiments, the first valve can provide at least 22 dB of isolation at the primary frequency of the power amplifier.

"The present invention also provides methods for alternately sending and receiving with an antenna. An exemplary method comprises alternatingly transmitting RF signals from a power amplifier to an antenna and receiving RF signals from the antenna. More specifically, the step of transmitting the RF signals from the power amplifier to the antenna is performed over a transmitter transmission line while simultaneously impeding the RF signals on a receiver transmission line coupled between the receiver amplifier and the antenna. Similarly, the step of receiving RF signals from the antenna is performed over the receiver transmission line while simultaneously impeding RF signals from the power amplifier on the transmitter transmission line. In various embodiments, a CMOS device switches from the power amplifier transmitting RF signals to the antenna over the transmitter transmission line to the receiver amplifier receiving RF signals from the antenna over the receiver transmission line.

"In some embodiments impeding the RF signals on the receiver transmission line includes maintaining a first valve, disposed between the receiver transmission line and ground, in an on state. Likewise, in some embodiments, impeding RF signals from the power amplifier on the transmitter transmission line includes maintaining a second valve, disposed between the transmitter transmission line and ground, in an on state. In some of these embodiments, the first and/or second valves include a double-gate semiconductor device and the step of maintaining the valve in the on state includes controlling the gates of the double-gate semiconductor device such that the double-gate semiconductor device conducts between a source and a drain thereof. Controlling the gates of the double-gate semiconductor device such that the double-gate semiconductor device does not conduct between the source and the drain turns the valve off, removing the impedance from the valve on the respective transmission line allowing either transmission from the power amplifier to the antenna, or reception by the receiver amplifier from the antenna."

For the URL and additional information on this patent, see: Masliah, Denis A.. RF Switches. U.S. Patent Number 8731485, filed July 19, 2013, and published online on May 20, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=41&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=2005&f=G&l=50&co1=AND&d=PTXT&s1=20140520.PD.&OS=ISD/20140520&RS=ISD/20140520

Keywords for this news article include: Electronics, Acco Semiconductor Inc..

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Source: Electronics Newsweekly


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