High isolation switch with notch filter

A switching method and apparatus that provides high isolation between circuit arms of a mobile communication device by attenuating noise over a defined frequency range using a switched shunt LC notch filter.

BACKGROUND

1. Field of Invention

The present invention relates generally to mobile communication devices. More particularly, at least one embodiment of the invention relates to high isolation switches for use in mobile communication devices.

2. Discussion of Related Art

Mobile communication devices, such as cellular phones, two-way radios, etc., having a transceiver for transmitting and receiving communication signals generally include a radio frequency (RF) switch to switch the antenna between a receive path and a transmit path. In addition, RF switches can be used to provide operation of the device in more than one frequency band. For example, multiple different communication standards, such as the Global System for Mobile (GSM) communication standard (utilized frequently in Europe and Asia) and the Code Division Multiple Access (CDMA) communication standard (utilized frequently in the United States) exist for cellular phone use, and these different standards require operation in different frequency bands. There is a growing demand for cellular phones and other mobile communication devices to be compatible with more than one communication standard. Therefore many devices include separate circuits to accommodate different communication standards, and use an RF switch to selectively alternate between the different circuits to operate the device in a desired mode.

These RF switches are generally located in close proximity to the antenna of the communication device. Accordingly, high isolation switches are desired as it is important to limit noise leakage and/or harmonic interference between the transmit and receive paths, or between different transmit or different receive paths in the device. In addition, it is desirable that the switch have low loss associated therewith to reduce power consumption and preserve battery life in a mobile device. Furthermore, because mobile communication devices are typically small, the components are located in very close proximity to one another, making electronic isolation, and therefore noise reduction, more important since there may be little isolation resulting from physical separation of the components. Furthermore, because many mobile communication devices are generally low power devices, even a relatively low level of noise may result in power loss that negatively impacts the performance of the device, and therefore good isolation between components is desirable.

SUMMARY OF INVENTION

An RF switch that provides high isolation between circuit arms while maintaining linearity and limiting noise, interference and power loss between circuit arms is desired. Accordingly, aspects and embodiments are directed to a switching method and apparatus that is compact, efficient and which provides very high isolation between circuit arms of a mobile communication device using a switched shunt LC notch filter. Using an LC notch filter with a relatively low number of components in a high isolation switch may allow the switch to limit noise, interference, and power loss between circuit components while maintaining good linearity across the desired operating frequency ranges, as discussed further below. Additionally, by utilizing a high-integration, well developed technology such as CMOS, the size of the high isolation switch may be kept relatively small. Furthermore, by allowing a user to tune the level of attenuation of the LC notch filter by adjusting the value of one component, as also discussed below, the high isolation switch may be easily configurable responsive to the needs of the user.

According to one embodiment, a high isolation radio frequency (RF) switch comprises an input, an output, a switching circuit coupled in series between the input and the output, the switching circuit configured to selectively couple the input to the output responsive to a control signal, at least one shunt circuit coupled between the input and a ground, and at least one LC notch filter switchably coupled to the input in a shunt configuration. The at least one LC notch filter comprises a series combination of a switch, at least one capacitor and at least one inductor, and is configured to attenuate signals within a stop band range of frequencies determined by a value of the at least one capacitor and a value of the at least one inductor.

In one example of the high isolation RF switch the at least one capacitor is connected in series between the switch and the input, and wherein the at least one inductor is connected in series between the switch and ground. In another example, the switch of the at least one LC notch filter comprises a plurality of series connected transistors. The switching circuit may comprise, for example, at least one transistor coupled in series between the input and the output, the at least one transistor configured to selectively couple the input to the output responsive to the control signal. In one example in which the high isolation RF switch is an absorptive switch, the switch further comprises a termination circuit selectively coupled in series between the input and the switching circuit. The termination circuit may comprise, for example, at least one resistor and at least one transistor, and may be configured to selectively couple the resistor into and out of connection between the input and the switching circuit. In one example, the shunt circuit comprises at least one transistor coupled in series between the input and ground, wherein the at least one transistor is configured to selectively couple the input to ground responsive to a shunt control signal. In one example, the at least one inductor includes at least one bondwire inductor. In another example, the at least one capacitor includes one of a variable capacitor and a switchable bank of capacitors. In another example, the value of the at least one capacitor and the value of the at least one inductor are matched.

According to another embodiment, a radio frequency (RF) device comprises a first RF transmission line, a second RF transmission line, an output, a first switching arm coupled between the output and the first RF transmission line, the first switching arm configured to selectively couple the first RF transmission line to the output for a first mode of operation of the RF device, and a second switching arm coupled between the output and the second RF transmission line, the second switching circuit configured to selectively couple the second RF transmission line to the output for a second mode of operation of the RF device. The RF device further comprises a first LC notch filter switchably coupled to the first switching arm in a shunt configuration, the first LC notch filter comprising a series combination of a first capacitor, a first inductor, and at least one first transistor. The at least one first transistor is configured to activate the first LC notch filter in the second mode of operation of the RF device. The first LC notch filter is configured to attenuate signals within a first range of frequencies determined by a value of the first capacitor and a value of the first inductor, the first range of frequencies being selected to include noise frequencies in the first switching arm during the second mode of operation of the RF device.

In one example, the RF device further comprises at least one shunt circuit coupled between the first RF transmission line and ground. The at least one shunt circuit may comprise, for example, at least one transistor coupled in series between the first RF transmission line and ground, wherein the at least one transistor is configured to couple the first RF transmission line to ground in the second mode of operation of the RF device, responsive to a control signal. In one example, the first inductor includes at least one bondwire inductor. In another example, the first capacitor includes one of a variable capacitor and a switchable bank of capacitors. In another example, the value of the first capacitor and the value of the first inductor are matched. In another example in which the first switching arm is an absorptive switching arm, the RF device further comprises a termination circuit selectively coupled in series between the first RF transmission line and the first switching arm. The RF device may further comprise a second LC notch filter switchably coupled to the second switching arm in a shunt configuration, the second LC notch filter comprising a series combination of a second capacitor, a second inductor, and at least one second transistor, wherein the at least one second transistor configured to activate the second LC notch filter in the first mode of operation of the RF device. In one example, the second LC notch filter is configured to attenuate signals within a second range of frequencies determined by a value of the second capacitor and a value of the second inductor, the second range of frequencies being selected to include noise frequencies in the second switching arm during the first mode of operation of the RF device. In another example, the first RF transmission line is configured to transmit signals to the output, via the first switching circuit, in the first mode of operation of the RF device, and the second RF transmission line is configured to receive signals from the output, via the second switching circuit, in the second mode of operation of the RF device. In one example, the first RF transmission line is configured to carry GSM signals in the first mode of operation of the RF device, and the second RF transmission line is configured to carry CDMA signals in the second mode of operation of the RF device.

Still other aspects, embodiments, and advantages of these exemplary aspects and embodiments, are discussed in detail below. Moreover, it is to be understood that both the foregoing information and the following detailed description are merely illustrative examples of various aspects and embodiments, and are intended to provide an overview or framework for understanding the nature and character of the claimed aspects and embodiments. Any embodiment disclosed herein may be combined with any other embodiment in any manner consistent with at least one of the objectives, aims, and needs disclosed herein, and references to “an embodiment,” “some embodiments,” “an alternate embodiment,” “various embodiments,” “one embodiment” or the like are not necessarily mutually exclusive and are intended to indicate that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment. The appearances of such terms herein are not necessarily all referring to the same embodiment.

DETAILED DESCRIPTION

Aspects and embodiments are directed to a switching method and apparatus to provide high isolation (e.g. in excess of 40 dB) between circuit arms of a mobile communication device by specifically attenuating noise over a defined frequency range using an LC notch filter. Because of the relatively small number of components needed to implement the LC notch filter, the high isolation switch may be able to limit noise, interference and power loss between circuit arms while maintaining good linearity and a small circuit footprint. The size of the high isolation switch may also be kept small by utilizing Complementary Metal Oxide Semiconductor (CMOS) technology, for example, to provide a high integrated, relatively inexpensive device. Additionally, the level of attenuation of the LC notch filter may be easily configured by adjusting the value of one or more components of the LC notch filter, as discussed in more detail below. Thus, the high isolation switch may be easily configured to meet the specific needs of a user, providing a flexible, low cost, and high performance solution.

It is to be appreciated that embodiments of the methods and apparatus discussed herein are not limited in application to the details of construction and the arrangement of components set forth in the following description or illustrated in the accompanying figures. The methods and apparatus are capable of implementation in other embodiments and of being practiced or of being carried out in various ways. Examples of specific implementations are provided herein for illustrative purposes only and are not intended to be limiting. In particular, acts, elements, and features discussed in connection with any one or more embodiments are not intended to be excluded from a similar role in any other embodiments.

Referring toFIG. 1A, there is illustrated a block diagram of one example of a non-absorptive switch100which may be used within a mobile communication device to selectively switch between different circuits in a device. For example, the switch may be used to switch between a transmit circuit and a receive circuit, or between different transmit or different receive circuits used for different communications standards. In the illustrated example, the switch100is a single pole, double throw (SPDT) switch including a first switching arm102and a second switching arm104which selectively couple first and second circuits112,116, respectively, to an antenna106. As discussed above, the circuits112,116may be transmit and/or receive circuits, which may be used, for example, to accommodate different frequency bands and/or comply with two different transmissions standards, such as CDMA and GSM which operate in different frequency ranges. Additional examples of transmission standards include Wideband Code Division Multiple Access (WCDMA), Wireless Local Area Network (WLAN), Worldwide Interoperability for Microwave Access (WiMAX), High-Speed Downlink Packet Access (HSDPA), High-Speed Uplink Packet Access (HSUPA) and Long Term Evolution (LTE). Switches such as switch100may be used to select between circuits designed for any of these or other transmission standards.

In one embodiment, the switch100is configured to activate either the first circuit112or the second circuit116by selectively coupling either circuit to the antenna106. Assuming activation of the first circuit112is desired, a control signal applied on the first control line117will operate the first switching arm102to connect the first circuit112to the antenna106, and a control signal over the second control line118will operate the second switching arm104to decouple the second circuit116from the antenna106and thereby “deactivate” the second circuit116. Alternatively, assuming activation of the second circuit116is desired, a control signal over the second control line118will operate the switching arm104to connect the second circuit116to the antenna106and a control signal over the first control line117will operate the switching arm102to decouple the first circuit112from the antenna106and deactivate the first circuit112.

According to another embodiment, the switch100may be an absorptive switch. In this example, a termination circuit108is coupled to the antenna106, as illustrated inFIG. 1B. Referring toFIG. 1B, in the illustrated example, the termination circuit108is coupled between the switch100and the antenna106in a shunt configuration. However, according to another embodiment, the termination circuit108may be coupled in series between the switch100and the antenna106. The termination circuit108, controlled by signals on a termination control line (not shown), may be configured to provide line termination at the antenna106to reduce noise or interference. In one example, the termination circuit108provides a 50 Ohm or 75 Ohm termination. The termination circuit108also can include or function as an Electrostatic Discharge (ESD) suppression network.

As discussed above, it may be highly desirable to limit interference between the two circuits112,116, and switching arms102,104of the switch100, and therefore to isolate the first circuit112from the second circuit116. One conventional method of providing isolation between an activated arm (e.g., the first arm102) and a deactivated arm (e.g., the second arm104) of the switch100includes the use of electrical shunts. An electrical shunt may be added to either circuit arm102,104to redirect unwanted noise to ground before the noise can propagate to other circuit components and create interference. However, particularly depending on the technology used within the mobile communication device, the isolation provided solely by shunts may be limited. For example, as the operating frequency of the device increases, the ability to achieve high levels of isolation using shunts decreases. Although additional, parallel-connected shunts can be added to increase isolation, it has been found that the amount of isolation provided by each additional shunt decreases dramatically, and that additional shunts beyond three are generally ineffective. Furthermore, each additional shunt affects the performance of the switching arm, reducing linearity and degrading the signal, particularly at high frequencies (e.g., above 1 GHz). As a result, the total amount of isolation that can be achieved using the shunt method is limited, particularly at higher frequencies. Switches providing approximately 3-4 dB of isolation may be relatively easy to implement using shunts; however, for a high isolation switch (e.g., greater than 55 dB isolation between arms), a different technique is needed, as discussed further below.

Another type of technology and an alternative to CMOS which may be used in mobile communication devices is pseudomorphic High Electron Mobility Transistors (pHEMT). Typically, the package size of a pHEMT-based device is significantly larger and consequently more expensive than a similar device implemented in CMOS. For example, unlike a CMOS-based device, a pHEMT-based device may be unable to provide integrated control functionality within the device and may require external control circuitry. As a result, the package size of the pHEMT-based device may be relatively large. Therefore, CMOS is generally a preferred technology for mobile communications devices. Although electrical shunts can be used to achieve higher levels of isolation with pHEMT devices than in CMOS devices, the addition of several shunts to obtain a desired level of isolation adds to the already larger size of the pHEMT device, making pHEMT switches undesirable for many mobile communications devices.

Thus, there is a need for a small, relatively inexpensive, CMOS-based RF switch capable of providing very high isolation between different circuits and/or switch arms at high frequencies, while maintaining linearity and limiting noise, interference, and power loss between the switched circuits. Accordingly, aspects and embodiments of the invention are directed to a high isolation switch that incorporates the use of a switched shunt notch filter to provide very high isolation between switching arms.

Referring toFIG. 2, there is illustrated one example of a switching arm200of a high isolation switch including an LC notch filter in accordance with one embodiment. The switching arm200corresponds to either one of the switching arms102,104inFIG. 1A. In the illustrated example, the switching arm200is non-absorptive; however, absorptive switches may also be implemented, as discussed further below. The switching arm200includes a switch circuit202coupled between an input204and the antenna106. The input204may be coupled to one of the circuits112,116ofFIG. 1A. According to one embodiment, the switch is an RF switch; however, it is to be appreciated that the switch is not limited to the RF or any other particular range of frequencies. The switch circuit202comprises a plurality of transistors216coupled in series between the input204and the antenna106which provide the switching function. The plurality of transistors216may include any number of transistors, not limited to the number illustrated inFIG. 2. According to one embodiment, when activation of the arm200is desired, a control signal212(corresponding to control signal117or118inFIG. 1, for example) is provided to operate the switch circuit202to couple the input204to the antenna106. The control signal212is provided to the gates of the plurality of transistors216to activate the transistors and allow current to flow from the input204, through the plurality of transistors216, to the antenna106. When deactivation of the arm200is desired, the control signal212is provided to the gates of the plurality of transistors216to deactivate the transistors and prevent current flow between the input204and the antenna206.

As discussed above, the switching arm200further includes a switchable LC notch filter208coupled between the input204and ground206and situated between the input204and the switch circuit202, as shown inFIG. 2. The switching arm200also includes at least one shunt circuit210coupled between the input204and ground206, as discussed in more detail below. The LC notch filter208in combination with the at least one shunt circuit210may provide very high isolation, for example, in excess of 64 dB at 1 GHz, as discussed further below.

According to one embodiment, the at least one shunt circuit210includes a plurality of transistors214coupled in series between the input204and RF ground206. The plurality of transistors214may include any number of transistors, and is not limited to the number shown inFIG. 2. In the illustrated example, the shunt circuit210is coupled between the first and second transistors of the switch circuit202. However, it is to be appreciated that the shunt circuit210may be coupled to a different location in the switch circuit202, and that additional shunts may be included and may be coupled to different points of the switch circuit202(e.g. between any two of the plurality of transistors216).

As discussed above, even when the arm200is deactivated, it is possible for noise from arm200to interfere with a different, activated arm (not shown). Accordingly, upon deactivation of the arm200, a control signal224is provided the plurality of transistors214of the shunt circuit210to activate the transistors and allow current to flow from the input204to ground206. By allowing current to flow from the input204to RF ground206, at least a portion of the unwanted noise in the arm200may be directed to ground before it can propagate to other circuit components. Upon activation of the arm200, a control signal224is provided to the plurality of transistors214to deactivate the transistors and prevent current flow through the shunt circuit210, thereby allowing the signal from the input204to pass to the antenna106. The control signals212and224operate in concert, such that when the transistors216are active, the transistors214are switched OFF, and when the transistors216are turned OFF, the transistors214are turned ON.

The configuration of shunts within the arm200may depend on the type and power level of the signal passing through the switch circuit202. For example, when the arm200is activated and the transistors214are deactivated, the transistors214of the shunt circuit210may be configured to accommodate and maintain the voltage at the input204across the shunt circuit210. To accommodate a signal on the input204with a relatively high voltage swing, the number (“stack height”) of the transistors214may be relatively high to prevent drain-to-source breakdown of the transistors214and consequently current flow in the shunt circuit210from the input204to RF ground206. For example, assuming a signal on the input204has a voltage swing of >30V peak-to-peak and the transistors have a drain-to-source breakdown voltage (BVDSS) of 3V; a stack height of >10 transistors coupled in series may be used to prevent breakdown. Conversely, when the circuit needs only to maintain a signal on the input204with a relatively low voltage swing, the stack height of the transistors214may be relatively low.

In another embodiment, when the arm200is deactivated and the transistors214are activated, the transistors214may be configured to provide a matching resistance to external circuitry to limit reflections in the arm200. It is to be appreciated that if the shunt circuit210does not provide a low enough resistance to ground or an appropriately matched resistance, the shunt circuit210may create “notches” in the insertion loss of the arm200, meaning that at certain frequencies (in the “notches”), the insertion loss is poor, due to signal reflections. As such, it may be necessary to balance the prevention of drain-to-source breakdown with the prevention of reflections. For instance, in examples where the stack height of the transistors214is relatively high to accommodate high signal voltage on the input204, the width of the transistors214may be increased to compensate for the added resistance of the additional transistors and thereby maintain a matching resistance.

As discussed above, in order to provide a switch with high isolation and a relatively small circuit footprint, in one embodiment, a switchable LC notch filter208is used to provide further isolation in addition to that provided by the shunt214. According to one embodiment, the LC notch filter208includes a capacitor220, an inductor222, and a plurality of transistors218coupled in series between the capacitor220and the inductor222, as shown inFIG. 2. The inductor222is coupled between the plurality of transistors218and ground206. The LC notch filter208has a center resonance frequency, and is designed to pass all frequencies except those within a “notch” (or stop band) centered on a center resonance frequency. Thus, signals at frequencies within the stop band are attenuated. The capacitor220and inductor222are used to tune the notch filter to the desired operating center resonance frequency. The quality factor (Q) of the LC notch filter208is defined as the center frequency of the filter divided by the bandwidth of the filter. The bandwidth is defined as the frequency range between the frequency of the upper 3 dB roll-off point of the filter and the frequency of the lower 3 dB roll-off point of the filter. In other words, the Q factor represents the size (width) of the stop band in relation to the center frequency. The plurality of transistors218are used to switch the notch filter208ON and OFF and also to set the Q of the filter. When the switching arm200is active, a control signal226is provided to the gates of the plurality of transistors218to turn the notch filter OFF, and when the arm200is deactivated the notch filter is turned ON to isolate the deactivated arm. Thus, the control signals212,224and226operate in concert such that when the transistors216are turned ON, the transistors214and218are turned OFF and when the transistors216are turned OFF, the transistors214and218are turned ON. The number (stack height) and size of the transistors218are selected to accommodate a high signal voltage on the input204as discussed above in conjunction with transistors214, and to achieve a desired Q for the filter208. Accordingly, it is to be appreciated that the plurality of transistors218may include any number of transistors, not limited to the number shown inFIG. 2.

Still referring toFIG. 2, the center frequency of the notch or stop band of the filter208is primarily determined by the values of the capacitor220and the inductor222. The level of attenuation provided by the filter to signals within the stop band (i.e., the “depth” of the notch) is determined by the relationship between capacitor220and the inductor222, for a given resistance of the transistors218. In order to achieve a deep notch, and therefore very high attenuation of signals in the stop band, the values of the capacitor220and inductor222should be matched, i.e., have approximately the same impedance magnitude. Tuning of the capacitor220and inductor222values to select both a desired center frequency and notch depth may be achieved by making one or both of the elements variable. For example, according to one embodiment where the value of the capacitor220is fixed, the value of the inductor222may be tuned or matched with the value of the capacitor220to provide the desired notch depth (i.e. desired attenuation) within the stop band of the filter. According to another embodiment where the value of the inductor222is fixed, the value of the capacitor220may be tuned or matched with the value of the inductor222to provide the desired notch depth (i.e. desired attenuation) within the stop band of the filter.

In one embodiment, the inductor222is realized using one or more bondwires to ensure a high Q inductor. In particular, the inductor222may be implemented as double (parallel) bondwires for repeatability. In these embodiments, the capacitor220may be a variable capacitor to allow tuning of the center frequency and/or notch depth of the filter208. For example, the capacitor220may be a variable capacitor, such as a varactor, or may be implemented as a bank of switchable capacitors. Thus, a switchable notch filter with a tunable Q, based on the stack height and size of the switching transistors218, and a tunable operating frequency and notch depth may be implemented using only a few components, namely an on-chip capacitor220, a switch (the plurality of transistors218) and one or more bondwire inductors222. The notch filter may therefore be very small, but provide very good isolation because the notch can be made very deep. The filter208may be tuned based on knowledge of likely frequencies of noise from the other arm of the switch200and thus may be configured to attenuate specific frequencies of noise arising in the deactivated arm200which would otherwise interfere with signals in the activated arm (not shown) of the switch. In addition, as will be appreciated by those skilled in the art, given the benefit of this disclosure, additional LC notch filters may be included in the switching arm200, connected in parallel with the notch filter208, to provide multiple stop bands and therefore wider-band isolation. However, it is also to be appreciated that as additional circuitry is coupled to the input204, the load characteristics of the line may change. Therefore the level of isolation provided by the arm200may need to be balanced with the design specifications of the switch100.

It is further to be appreciated that in implementation of the switching arm200, resistors (not shown) may be coupled to each of the transistors214,216,218,226illustrated inFIG. 2, as will be understood by those skilled in the art, given the benefit of this disclosure. For example, a resistor may be coupled across the source and drain of each transistor to provide voltage balance while the arm200is deactivated. A resistor may also be coupled between a DC gate bias (not shown) and the gate of each transistor to maintain a constant gate to source bias voltage during the transition of the arm200from an activated to deactivated state. Additionally, a common resistor may also be used to couple to all of the individual gate resistors to the DC gate bias.

Referring toFIG. 3, there is illustrated a graph300of isolation (in dB) provided by an example of the switching arm200over a range of frequencies from about 1 GHz to 3 GHz. In this example, the switching arm200provides greater than 40 dB isolation over the measured frequency range. Table 1 below includes example values of isolation provided between switching arms200of an embodiment of the switch as measured at three example frequencies.

The noise that can be seen on trace301inFIG. 3, particularly in the vicinity of reference302, is due to limitations in the printed circuit board on which the test switch was fabricated. In a practical implementation, noise may be due to nonlinear circuits (for example, amplifiers, diodes, etc.) coupled to the input204. The results illustrated inFIG. 3provide confirmation that embodiments of the switch incorporating the notch filter208discussed above can provide very high levels of isolation at high frequencies. In particular, as demonstrated by the above example, embodiments of the switch can achieve isolation of greater than 60 dB at 1 GHz, 52 dB at 2 GHz and 42 dB at 3 GHz between an activated arm and a deactivated arm of the switch. These levels of isolation are significantly higher than the levels of isolation that can be achieved using only shunts without an LC notch filter.

As discussed above, embodiments of the switch100may be absorptive or non-absorptive. Referring toFIG. 4, there is illustrated an arm400of a high isolation absorptive switch in accordance with one embodiment. The switching arm400is similar to the non-absorptive switching arm200discussed above with reference toFIG. 2, and includes a termination circuit402. According to one embodiment, the termination circuit402includes a resistor404and a transistor406. The value of the resistor404may be selected such that the impedance presented to the input204by the switching arm400is a certain desired value. For example, where the impedance presented by the switching arm400is desired to be approximately 50 Ohms, the resistor404is a 45 Ohm resistor, accounting for the impedance added by components202,208, and210. However, it is to be appreciated that the resistor value will vary with the desired value of the total impedance of the switching arm400and the impedance presented by the components202,208, and210and therefore the value of the resistor404is not limited to 45 Ohms. The transistor406is used as a switch to switch the resistor404into or out of connection between the input204and the switch circuit202depending on whether the switching arm400is inactive or active, respectively.

Referring toFIG. 5, there is illustrated a block diagram of one example of an Integrated Circuit (IC) chip layout of a Single Pole Double Throw (SPDT) high isolation switch500, corresponding to the switch100discussed above, in accordance with one embodiment. As discussed above, the SPDT switch500includes two arms502,504which are selectively coupled to an antenna connection512to which the external antenna106may be connected. In examples in which the switch500is an absorptive switch, the switch arms502,504are also coupled to a termination circuit522corresponding to the termination circuit108as discussed above with reference toFIG. 1B.

In the illustrated example, each of the arms502,504includes a switch circuit514, LC notch filter508, and at least one shunt circuit510. The switch500further includes input connection pads506to receive a signal from circuits102and104as discussed above with reference toFIGS. 1A and 1B. Each switch circuit514corresponds to the switch circuit202discussed above, and comprises the plurality of transistors216coupled between the respective input connection506and antenna connection512. The shunt circuits510each correspond to the shunt circuit210discussed above, and are connected between the respective transmit line506and ground526. The LC notch filter508corresponds to the LC notch filter208as discussed above with reference toFIG. 2and includes the inductor222(not shown inFIG. 5), a capacitor516, a plurality of transistors518, and at least one inductor connection520to which the inductor222may be connected. As discussed above, in one embodiment, the inductor222is realized using one or more bondwires coupled to the at least one inductor connection520. In particular, the inductor222may be implemented as a double bondwire for manufacturing repeatability.

Referring toFIG. 6, there is illustrated a block diagram of another example of an Integrated Circuit (IC) chip layout of an absorptive high isolation switch600, corresponding to the switch100discussed above, in accordance with one embodiment. The switch600is comparable to the switch500described in relation toFIG. 5, and includes additional DC power supply integration and a termination line connection. According to one embodiment, each arm502,504of the switch600includes a first DC power supply input602and a second DC power supply input604. In one example, each DC power supply input602,604may be coupled to an external power supply (not shown) capable of providing DC power to the high isolation switch600. According to another embodiment in which the switch600is an absorptive switch, the switch600may also include a termination line connection606. In this example, the termination line connection606is configured to be coupled to an external termination control line (not shown) which is capable of providing control signals to operate the termination circuit522.

Referring toFIG. 7, there is illustrated a diagram of another example of an Integrated Circuit (IC) chip layout700of a high isolation switch701, corresponding to the switch100discussed above, in accordance with one embodiment. The switch701is comparable to the switch600described with respect toFIG. 6. The chip700includes the switch701and multiple external connections to a Printed Circuit Board (PCB). For example, in examples where the switch701is used to switch between different transmit lines (e.g., from transmitter circuits configured for different frequency bands, as discussed above), each input connection506of the switch701is coupled to an external transmission line704on the PCB702. Each external transmission line704may be coupled to additional external circuitry (not shown) configured to transmit or receive signals from the antenna106, via the switch701. The antenna connection512is coupled to an antenna line710on the PCB702. The antenna line710may be coupled to the external antenna106configured to transmit signals from one of the transmission lines704via the switch701or receive signals to provide to one of the transmission lines704via the switch701.

Each DC power supply input602,604is coupled to a DC power line712on the PCB702. Each DC power line712may be coupled to an external DC power source (not shown) configured to provide DC power to the components of the switch701. According to one embodiment, a first external DC power source (not shown) may be configured to provide a first DC power level to the first DC power supply input602and a second external DC power source (not shown) may be configured to provide a second DC power level to the second DC power supply input604. In examples in which the switch is an absorptive switch, a termination line connection606is coupled to a termination control line714on the PCB702. The termination control line714may be coupled to external circuitry (not shown) configured to control the operation of the termination circuit522for absorptive embodiments of the switch701.

Still referring toFIG. 7, each of the inductor connections520are coupled to a grounded portion718of the PCB720via a bondwire inductor716. As illustrated, the switch701includes two bondwire inductors716; however, it should be appreciated that any number of inductors may be used. The bondwire inductors716correspond to the inductor222of the LC notch filter208as discussed above with reference toFIG. 2. A user may adjust the operating frequency and notch depth of the filter208by tuning the value of the capacitor516. Each RF ground526of the switch701also may be coupled to a grounded portion718of the PCB702. According to one embodiment, the multiple external connections of the switch701may be coupled to the PCB via a Multi-Chip Module (MCM).

As described herein, the components of the high isolation switch of the current invention are CMOS devices. However, it is to be appreciated that the high isolation switch of the current invention may be developed using other types of mobile communication technology, such as, for example, pHEMT.

As described herein, the high isolation switch of the current invention is utilized as a single pole, double throw (SPDT) switch with two arms. However, it should be appreciated that the high isolation switch of the current invention may be utilized as any type of switch. For example, the high isolation switch may be configured as a single pole, single throw switch (SPST) with one arm, a double pole, single throw switch (DPST) with two arms, a double pole, double throw switch (DPDT) with four arms, a single pole, twelve throw switch (SP12T) with twelve arms, or numerous other configurations, as will be recognized by those skilled in the art, given the benefit of this disclosure. The high isolation switch may be configured to select between many different types of circuits and/or transmission lines. For example, as discussed above, the switch may be used to select between different transmit lines, different receive (Rx) lines, or a combination of transmit and receive lines.