Patent Application
20130029614
Embodiments of the invention relate generally to antenna switch controllers, and more particularly, to negative-charge-pump-based antenna switch controllers utilizing battery supplies.
As wireless communication evolves, there is an increased demand to support multiple standards in a single cellular device. Each standard can require multiple power amplifiers (PAs) and low noise amplifiers (LNAs) in order to cover multiple bands. Because those PAs and LNAs may have to transmit and receive a radio frequency (RF) signal through a shared antenna, an antenna switch is an essential component for selecting a communications block for transmission or reception of an RF signal. Accordingly, a multi-port antenna switch is the one of the key building blocks in the RF front-end circuits for multi-standard cellular devices.
As the market drives integration of multiple standards and multiple bands into a single device, the complexity of the control scheme increases as does requirements for antenna switch performance. However, conventional technologies used for antenna switches such as GaAs pHEMT and silicon-on-sapphire (SOS) are expensive and have significant disadvantages in integration. Accordingly, there is an opportunity for systems, methods, and apparatuses for negative charge-pump-based antenna switch controllers utilizing battery supplies.
According to an example embodiment, there is a CMOS antenna switch controller. The antenna switch controller may include a plurality of antenna switches commonly connected to one or more antennas, where each of the plurality of antenna switches includes a plurality of stacked transistors, where one of the plurality of antenna switches is enabled when transmitting or receiving one or more radio frequency (RF) signals via the one or more antennas; a voltage generator that receives an external supply voltage from a battery, wherein the voltage generator generates an internal supply voltage, where the internal supply voltage remains constant despite fluctuations in the external supply voltage from the battery; a clock buffer that generates clock signals from the constant internal supply voltage; and a charge pump that receives the clock signals and generates a constant negative voltage, where the constant negative voltage is for biasing of one or more of the plurality of antenna switches that are disabled.
According to another example embodiment, there is a method for an antenna switch controller. The method may include providing a plurality of antenna switches commonly connected to one or more antennas, where each of the plurality of antenna switches includes a plurality of stacked transistors, where one of the plurality of antenna switches is enabled when transmitting or receiving one or more radio frequency (RF) signals via the one or more antennas; receiving, by the voltage generator, an external supply voltage from a battery, and generating a respective internal supply voltage, wherein the internal supply voltage remains constant; generating, by a clock buffer, clock signals from the constant internal supply voltage; and receiving, by a charge pump, the clock signals and generating a constant negative voltage, wherein the constant negative voltage is for biasing one or more of the plurality of antenna switches that are disabled.
Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
Embodiments of the invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.
Embodiments of the invention may provide systems, methods, and apparatuses for negative-charge-pump-based antenna switch controllers utilizing battery supplies. Example antenna switch controllers may be fabricated using various silicon-based processes, including silicon-on-insulator (SOI) processes utilizing SOI substrates. In addition, example antenna switch controllers may utilize complementary metal-oxide-semiconductor (CMOS) technology. Likewise, example antenna switch controllers can control multiple transmit (TX) and/or receive (RX) switches with an antenna, thereby providing for single pole multiple throw (SPMT) antenna switch controllers. Accordingly, example antenna switches in accordance with example embodiments of the invention may be referred to as CMOS SPMT antenna switch controllers.
Example CMOS SOI RF antenna switch controllers in accordance with embodiments of the invention may provide for one or more of the following features: multi-band operation, high power level handling, and integration with other devices and circuits. In an example embodiment of the invention, a CMOS SOI RF antenna switch controller may be integrated with a plurality of receiver (RX) switches and/or transmitter (TX) switches. Example antenna switch controllers may generate stable and constant internal supply voltages and negative voltages from a varying supply voltage available from a battery supply, according to an example embodiment of the invention. As an example, an antenna switch controller may include one or more output drivers to provide constant control voltages to example antenna switch blocks, thereby providing for high RF performance. In an example embodiment of the invention, an example RF switch controller can be operated from a battery because its power supply can vary within a range, perhaps 3.0V to 5.0V, without performance degradation of the antenna switches and without any transistor reliability problems, according to an example embodiment of the invention.
It will be appreciated that the switch controller can provide at least three constant control voltage levels to one or more example antenna switches in accordance with an example embodiment of the invention. For example, these constant control voltage levels can include a negative voltage, a zero voltage, or a positive voltage. A negative voltage can be utilized to turn off an example antenna switch, as described herein. For example, during a transmit (TX) mode when one of the antenna switches is active, one or more other antenna switches may be turned off using an example negative voltage provided from the switch controller. The use of a negative voltage can ensure that the transistors in the off-state antenna switches remain off even with large RF signals being transmitted to the antenna.
On the other hand, in some embodiments, an antenna switch may be turned off using a zero voltage from the switch controller. For example, during a receive (RX) mode when one of the antenna switches is active, one or more other antenna switches may be turned off using an example zero voltage provided from the switch controller. In this case, the zero voltage may be sufficient because the RF signals being received may be relatively small, and are thus unlikely to disrupt any of the off-state transistors in the off-state antenna switches.
In addition, in some embodiments, an antenna switch may be turned on using a positive voltage from the switch controller. For example, when an antenna switch is active during either a TX mode or an RX mode, the transistors of the antenna switch may be turned on using the positive voltage for the switch controller, thereby providing a main signal path between the antenna and the respective transmit or receive blocks, according to an example embodiment of the invention.
It will be appreciated that the example antenna switches and the antenna switch controllers described herein are by way of example only. Many variations of these antenna switches and antenna switch controllers are available without departing from example embodiments of the invention.
Example Antenna Switch Controller
An RF CMOS antenna switch controller in accordance with an example embodiment of the invention now will be described in further detail with reference to
In general, the plurality of antenna switch blocks 101a-n may include at least one TX antenna switch block or at least one RX antenna switch block. For example, as shown in
As introduced above, an example antenna switch controller 105 can control the operations of the antenna switch blocks 101a-n, including enabling (turning ON) or disabling (turning OFF) the antenna switch blocks 101a-n. In general, the antenna switch controller 105 can receive a battery voltage (Vbat) 120, for example, from the battery of a cellular phone or other mobile device. Responsive to logic inputs 122 indicating a mode of operation (e.g., TX or RX and associated standard), the antenna switch controller 105 can generate a plurality of stable and constant DC control voltages (e.g., VG,TX1-n, VG,SH1-n, Vn,SH1-n, VB1-n) for controlling each of the antenna switch blocks 101a-n. It will be appreciated that maintaining stable and constant DC control voltages in view of a potentially fluctuating battery voltage (Vbat) 120 may be needed to ensure that one or more antenna switch blocks 101a-n remain in their desired mode of operation (e.g., enabled or disabled). For example, maintaining stable and constant DC control voltages can ensure that certain antenna switch blocks 101a-n remain disabled (OFF), when another antenna switch block 101a-n is enabled (ON) to deliver or receive large RF signals using the antenna 103. In an example embodiment, the example DC control voltages can remain stable and constant in the range of substantially 3.0V-5.0V, although other ranges, for example 2.5V-5.0V, can be supported without departing from example embodiments of the invention. In an example embodiment of the invention, one or more of control voltages can be a negative voltage, a zero voltage, or a positive voltage, as described herein.
The example antenna switch controller 105 of
The logic decoder 107 may provide control signals to operate the output driver 106 to provide various DC control voltages to operate respective antenna switch blocks 101a-n. The main negative and bias voltage generator block 108 and the sub negative and bias voltage generator block 109 may provide supply voltages to support the output driver 106 in providing various DC control voltages, including positive, negative, and zero voltages, according to an example embodiment of the invention.
In
In addition, the CMOS antenna switch 201 may include a plurality of stacked transistor switches 202a-n capable of selectively connecting the main signal path between a resistance and ground (GND). In
When transmitting a high power RF signal through one antenna switch block, it may be important to turn other switch blocks completely off to meet stringent RF switch linearity requirement. However, where the plurality of stacked transistor switches 203a-n comprise NMOS transistors, a zero voltage turn-off voltage for the transistor switches 203a-n may not be sufficient to meet linearity requirements. In this case, a negative turn-off voltage may be desired. Accordingly, the ON-state bias voltages for transistor switches 203a-n may be set to be a positive voltage (e.g., +2.3V) at the gate, and zero voltage (0V) at the body of transistor switches 203a-n. On the other hand, the OFF-state bias voltages for transistor switches 203a-n may be a negative voltage (e.g., −2.0V) for both the gate and body of the NMOS transistor. It will be appreciated that the output driver 106 can provide these control bias voltages as respective TX/RX gate control voltage 220 and a TX/RX body control voltage 225 to the respective gates and bodies of the plurality of transistor switches 203a-n. One of ordinary skill will appreciate that the example values of these negative, positive, and zero control bias voltages provided by the output driver 106 can be varied without departing from example embodiments of the invention.
With respect to the plurality of transistor switches 202a-n, the ON-state bias voltages for transistor switches 202a-n may be set to be a positive voltage (e.g., +2.3V) at the gate, and zero voltage (0V) at the body of transistor switches 202a-n. On the other hand, the OFF-state bias voltages for transistor switches 202a-n may be a negative voltage (e.g., −2.0V) for both the gate and body of the NMOS transistor. It will be appreciated that the output driver 106 can provide these control bias voltages as respective TX/RX shunt gate control voltage 225 and a TX/RX body control voltage 230 to the respective gates and bodies of the plurality of transistor switches 202a-n. One of ordinary skill will appreciate that the example values of these negative, positive, and zero control bias voltages provided by the output driver 106 can be varied without departing from example embodiments of the invention.
Turning now to the
Turning now to
Turning now to
In an example embodiment of the invention, transistors 403, 404 may be configured as a first CMOS switch; transistors 406, 407 may be configured as a second CMOS switch; and transistors 402, 405 may comprise a third CMOS switch.
The first CMOS switch comprising transistors 403, 404 may be connected between positive supply voltage VDD,on and ground (0V). More specifically, the source of PMOS transistor 404 may be connected to the positive supply voltage VDD,on while the source of NMOS transistor 403 may be connected to ground. The drains of transistors 404, 403 may be connected together to provide the output of the first CMOS switch. The gates of the transistors 404, 403 may likewise be connected together to provide the input of the first CMOS switch. In an example embodiment of the invention, the operation of the first CMOS switch may be controlled by the control input signal Vint.
The second CMOS switch comprising transistors 406, 407 may be connected between ground (0V) and a negative supply voltage Vss1. More specifically, the source of PMOS transistor 406 may be connected to ground (0V) while the source of NMOS transistor 407 may be connected to the negative supply voltage Vss1. The drains of transistors 406, 407 may be connected together to provide the output of the second CMOS switch. The gates of the transistors 406, 407 may likewise be connected together to provide the input of the second CMOS switch. In an example embodiment of the invention, the operation of the second CMOS switch may be controlled by the control input signal Vinb, which is used by the level shifter 408 to derive the control input signal VISO. In an example embodiment of the invention, an example level shifter 408 may convert a positive control signal Vinb (from 0V to VDD,in2) to a negative signal (from Vss2 to 0V) for use as the control input signal VISO.
The third CMOS switch comprising transistors 402, 405 may be connected between the outputs of the first and second CMOS switches. More specifically, the source of PMOS transistor 402 may be connected to the output of the first CMOS switch while the source of NMOS transistor 405 may be connected to the output of the second CMOS switch. The drains of transistors 402, 405 may be connected together to provide the output of the third CMOS switch, which may likewise be the output voltage (Vout)of the output driver 401. The gates of the transistors 402, 405 may likewise be connected together to provide the input of the third CMOS switch. In an example embodiment of the invention, the operation of the second CMOS switch may be controlled by the control input Vinm.
As shown in
To have a positive output voltage (e.g., VDD,on) from the output driver 401, the input control logic signals Vint and Vinm should be low, and the control logic signal Vint, should be equal to high. Recall, however, that the level shifter 408 not only converts the output voltage level but inverts the logic input Vinb. As a result, NMOS transistor 403 (M2), NMOS transistor 407 (M4), and NMOS transistor 405 (M6) are turned-off and PMOS transistor 404 (M1), PMOS transistor 406 (M3), and PMOS transistor 402 (M5) are turned-on to generate a positive voltage at the output.
To have a zero output voltage from the output driver 401, the input control logic signal Vint should be low, and the control logic signals Vinm and Vinb should be equal to high. Recall, however, that the level shifter 408 not only converts the output voltage level but inverts the logic input Vinb. As a result, NMOS transistor 403 (M2), NMOS transistor 407 (M4), PMOS transistor 402 (M5) are turned-off, and PMOS transistor 404 (M1), PMOS transistor 406 (M3), and NMOS transistor 405 (M6) are turned-on to generate a positive voltage at the output.
When the clock signal CLK is high, PMOS transistor M12 503 and NMOS transistor M13 502 are turned on while PMOS transistor M11 501 and NMOS transistor M14 504 are turned off. The node B of the capacitor C2 may be connected to ground and a negative charge having a value of C2·VDD,in1 may be stored in the capacitor C2. The node A of the capacitor C1 may be connected to the output capacitor CL and the negative charge may be moved from the capacitor C1 to the output capacitor CL.
The output voltage of the negative charge pump may be −VDD,in1 because the high output voltage of the clock signal CLK may be VDD,in1 from the VRB1 block 302. If a battery voltage (VBAT) is used for the supply voltage of the clock buffer, the output voltage of the main negative charge pump may be −VBAT. Because the battery voltage (VBAT) can change from 3.0V to 5.0V, the output voltage of a main negative charge pump can also change from −3.0V to −5.0V and this case should be avoided. For this reason, using VDD,in1 in
For an exemplary purpose, 2.5V may be set for the antenna switch device's nominal operation voltage. The negative voltage (Vss1) from the charge pump 305 may be used for the turn-off voltage of the RF antenna switches and should stay between −1.5V and −2.5V for the best RF performance of the antenna switch. If Vss1 is greater than −1.5V, the harmonic performance of the antenna switch is deteriorated. If Vss1 is smaller than −2.5V, it will affect the antenna switch device's long-term reliability and even can cause device breakdown if it is much smaller than −2.5V. This is why a constant internal supply voltage is required for the antenna switch controller.
Many modifications and other embodiments of the invention set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
