Patent ID: 12218702

DETAILED DESCRIPTION

In various embodiments, an integrated circuit having transceiver circuitry may further include switch circuitry to enable both a transmit path and a receive path to use a single off-chip filter. The switch circuitry may be dynamically controlled depending on mode of operation (e.g., receive or transmit) to programmably and dynamically direct appropriate receive or transmit signals to such off-chip filter. In a transmit direction, this single off-chip filter may couple between a transmit driver and a transmit power amplifier. And in a receive direction, this single off-chip filter may couple between a receive port and an on-chip amplifier. Such switch circuitry may be implemented with minimal insertion loss that has minimal effect on system performance.

With embodiments, a single off-chip filter may provide sufficient suppression of spurs for transmit signals, and in a receive mode may provide filtering of blocking signals and enhancing immunity. Although embodiments are not limited in this regard, implementations of a transceiver that include such switching circuitry may be used in a variety of different device types including sub-gigahertz (GHz) industrial scientific and medical (ISM) devices, such as may operate at a frequency range of somewhere between approximately 850 megahertz (MHz) and 925 MHz.

In some implementations, there may be multiple receive modes, including a so-called rural mode which may be used in an environment in which there are relatively few blocking or other interfering signals. In a rural mode, switching circuitry may be controlled to provide a receive path in which an incoming RF signal received via an antenna is provided first to a low noise amplifier (LNA) and then to an off-chip filter. Instead in a so-called urban mode, which may be active when a device is in an urban or other highly congested environment in which there may be potentially many blocking or interfering signals, switching circuitry may be controlled such that an incoming RF signal received via an antenna is first provided to the off-chip filter before being provided to the LNA.

By such control, a receiver implementation may realize a good noise figure in a rural environment while the same receiver, differently configured, may realize good blocking in an urban environment. Note also it is possible in both transmit and receive modes for the off-chip filter to be bypassed. Still further, in some situations for a transmit mode an external power amplifier also may be bypassed when a transmit RF signal is received within the RF front end circuit with sufficient power for a given environment. For example, in certain countries, e.g., Japan, an ISM device may have regulatory requirements that limit its output power to 13 dBm (or 14 dBm in Europe). In such an implementation, the external power amplifier can be bypassed. Also in such cases, if a RF signal output from SoC110is greater than a certain power level (e.g., 10 dBm), the off-chip filter may be bypassed, to avoid damage that could occur from providing it a signal that exceeds its capability.

Referring now toFIG.1, shown is a high level block diagram of a portion of a device such as an IoT device incorporating an embodiment. As illustrated inFIG.1, IoT device100may be any type of IoT device that has wireless communication capabilities. In one or more embodiments, IoT device100may operate with a radio that uses the same frequency band for transmit and receive (half duplex), as opposed to cellular, which has different frequency for uplink and downlink. While embodiments may vary, the IoT device may be a metering device, an actuator device, a sensor device, wireless microcontroller (MCU), wireless camera, wireless speaker, wireless microphone, wireless lighting controller, lightbulb, or so forth.

In the high level shown inFIG.1, a system on chip (SoC)110couples via an RF front end circuit150to an antenna180, which may be used for both transmit and receive operations. Of course in other implementations, there may be separate antennas for receive and transmit. In the embodiment ofFIG.1, SoC110may be implemented in one integrated circuit (IC) and RF front end circuit150implemented in another IC. In other cases, both of these components may be implemented in a single IC. In typical cases, the circuitry of SoC110may be implemented on one semiconductor die and the circuitry of RF front end circuit150may be implemented on a different semiconductor die, whether implemented in separate ICs or in the same IC package. Further, while the specific implementation ofFIG.1includes an SoC, in other cases, some other type of digital processor such as a baseband processor and/or application processor may be present.

Starting with SoC110, a digital circuit120is present, which may perform the overall processing of the device. Although embodiments are not limited in this regard, the processing may include activities such as performing sensing, metering, controller functionality, actuator functionality or so forth. To enable wireless communication, digital information may be provided from digital circuit120to an analog circuit130. In general, analog circuit130may include transceiver circuitry having transmit and receive paths including signal processing circuitry that perform various processing, including digital-to-analog conversion (in the transmit direction) and analog-to-digital conversion (in the receive direction), upconversion and downconversion, filtering, amplification and so forth.

Analog circuit130may transform the digital signals to analog form and further perform upconversion and other signal processing to generate RF signals. As seen inFIG.1, analog circuit130may optionally include a power amplifier (PA)132that may amplify the incoming RF signals and output them to RF front end circuit150.

In a receive direction, incoming receive signals that are received in SoC110couple to analog circuit130. As further shown optionally a LNA134may be provided for gain control, before additional signal processing is performed. This signal processing may include, e.g., filtering, further gain control, and downconversion to result in digital signals that are provided to digital circuit120.

RF front end circuit150also has transceiver circuitry including transmit and receive paths. With respect to the transmit path, incoming RF signals received from SoC110couple through switch circuitry155. Understand that switch circuitry155is shown at a high level, logically as a single block. In practice, a number of different switches may be implemented within RF front end circuit150to perform the configurable switching and communication of receive and transmit signals according to different modes, as described further herein. That is, while switch circuitry155is shown as a single block, the multiple physical switch instantiations may be located throughout RF front end circuit150. Also, by way of switch circuitry155, both receive and transmit paths may leverage a single RF filter170coupled to RF front end circuit150, thus reducing bill of materials (BOM) costs. In various embodiments, RF filter170may be implemented as a surface acoustic wave (SAW) filter. While for purposes of discussion, this RF filter is generally referred to herein as a SAW filter, understand that any type of RF filter, including various bandpass or low pass filters can be used.

With respect to the transmit path, RF signals to be transmitted may couple through switch circuitry155to SAW filter170(optionally), back through switch circuitry155and to a PA160for further amplification, before being output (through additional circuitry in switch circuitry155) to antenna180.

In a receive path, incoming RF signals received by antenna180couple into switch circuitry155. Such receive RF signals, before or after gain control in a LNA165, may be filtered by SAW filter170, and pass further through switch circuitry155and thereafter be sent to SoC110, and more specifically to analog circuit130. Understand that while shown in the high level ofFIG.1with a single LNA165, in some cases there may be multiple LNAs that can be controllably coupled with SAW filter170. For example, a received RF signal may pass through a first LNA, then through SAW filter170, and then through a second LNA before being provided to SoC110. And such multiple LNAs can be controlled to be bypassed, such that none, one, or both such LNAs may be part of a receive path.

In some cases, SoC110may provide an output signal at a power level of approximately zero dBm, which can be amplified both within PA132of analog circuit130of SoC110and PA160(or in cases, PA160may be bypassed). Note that in some cases, SAW filter170may be designed to only withstand approximately 10 dBm of power, such that in the transmit direction the transmit RF signal may be filtered in SAW filter170prior to further amplification.

As further shown inFIG.1, SoC110may include a microcontroller unit (MCU)135. Among its duties, MCU135sends mode control signals to RF front end circuit150. As seen, these signals may be provided to a controller158(which may be implemented as a microcontroller, finite state machine or so forth). In response to such control signals, controller158may dynamically configure and reconfigure switch circuitry155to operate in a given one of a transmit or receive mode (as RF front end circuit150can only operate in a transmit or receive direction at any given time). Still further, in various implementations there may be multiple receive modes and potentially multiple transmit modes available and which may entail different configurations of switch circuitry155. Understand while shown at this high level in the embodiment ofFIG.1, many variations and alternatives are possible.

Referring now toFIG.2, shown is a schematic diagram illustrating further details of a switch arrangement in accordance with an embodiment. As shown inFIG.2, a device200shows a more detailed view of a switch circuit implementation. In general, device200may be a similar IoT device as device100ofFIG.1, and thus to the extent that the same numbering conventions are used inFIG.2(although of the “200” series rather than the “100” series ofFIG.1), like components are shown and in some cases are not further discussed below.

At a high level, device200includes an SoC210, an RF front end circuit250, a SAW filter270, and an antenna280. SoC210is shown in the illustration ofFIG.2as having a transmit power amplifier232and a receive LNA234.

In the transmit direction, PA232outputs a differential RF signal that couples through a differential impedance match circuit240(formed of inductors L1, L2and capacitors C1, C2). The matched differential RF signal is converted to single-ended form via a balun245. The resulting single-ended transmit RF signal couples to RF front end circuit250via a transmit port B, which also may be used as a test port.

In the transmit direction, RF front end circuit250includes a transmit signal path including various switches and other circuitry to process and direct the transmit RF signal to its destination, namely, antenna280. More specifically, with reference toFIG.2, the transmit RF signal may couple through switches SW1and SW2(either with attenuation via an attenuator268using additional switch SW7, or unattenuated) to be directed to SAW filter270(via off-chip ports D and E, respectively). In an embodiment SAW filter270may be a bandpass filter configured to pass a band appropriate for a given device (e.g., between 875 and 950 MHz). After being filtered in SAW filter270, the filtered transmit RF signal couples through switch SW3and to power amplifier (PA)260, before being output through matching circuitry263(including inductor L4and capacitors C5, C6). From there, the amplified transmit RF signal couples through switch SW4and is output from RF front end circuit250and through a low pass filter (LPF)275to antenna280coupled to a port A. In an embodiment, LPF275may be a third order low pass harmonic filter having a typical loss level of approximately 0.5 dB. Note that the position of LPF275and SAW filter270may not be swapped, as in some use cases, the RF signal level that passes through LPF275would cause damage to SAW filter270.

Still with reference toFIG.2, in a receive direction, incoming RF signals pass through antenna280and LPF275and into RF front end circuit250. In the receive direction, the incoming receive RF signal couples through switch SW4and, depending upon mode, either directly to LNA265(via switch SW8) or via switch SW3to SAW filter270(and thereafter through switches SW2and SW8) and then to LNA265. This determination may be based on whether filtering is desired before or after amplification in LNA265.

As seen, it is further possible for the amplified receive RF signal output by LNA265to pass through switches SW5and SW3to SAW filter270. In yet other cases, SAW filter270may be bypassed in the receive direction, such that the amplified receive RF signal is provided directly from switches SW4and SW8through LNA265and through switches SW5and SW6, and thereafter off-chip through an impedance matching circuit245formed of inductor L3and capacitor C3to SoC210, and more specifically, to LNA234.

Still further it is possible in the receive direction for attenuation to occur via attenuator268that couples between switch SW2and switch SW7and in turn, provides the attenuated receive RF signal to SoC210through switch SW6. While switches SW1-SW8are illustrated inFIG.2as various single pole multiple throw (P/T switches), other types of switches may be used.

Of course while shown with this particular implementation with the above-described paths through RF front end circuit250, switching circuitry may take various forms to enable transmit and receive paths to share a single SAW filter, reducing costs and complexity. Furthermore, it is possible by way of different control of the various switches to enable both transmit and receive RF signals to pass through the respective transmit and receive paths in different orders.

Still referring toFIG.2, controller258may dynamically configure the various switches to enable operation in a desired transmit or receive mode, as well as sub-modes that may be available in a given implementation. To this end, controller258receives incoming front end control signals from SoC210(more specifically from MCU235).

In response to these control signals, controller258may control the various switches as described above. In a particular embodiment, MCU235may output four front end mode control signals. Controller258, based at least in part on these control signals, may dynamically configure the switches of RF front end circuit250accordingly. With four control lines being provided to controller258, there may be sufficient programmability for 16 different modes, with approximately half of these modes available for transmit operations and half available for receive operations. Or certain states can be reserved for other modes such as testing or measurement modes.

Referring now toFIG.3, shown is a flow diagram of a method in accordance with an embodiment. As shown inFIG.3, method300is a method for controlling switch circuitry of an RF front end circuit such as may be performed by a controller or other hardware circuit within the RF front end circuit. In some cases, the controller may execute instructions stored in a non-volatile memory. In an embodiment, this non-volatile memory may be implemented as a non-transitory storage medium that can store instructions and data. Such non-volatile memory may store instructions, including instructions for receiving mode control signals and controlling switch circuitry in response to the mode control signals, as described herein.

As illustrated, method300begins by receiving front end control signals from a processor (block310). As discussed above, there may be a plurality of control lines that provide control signals to indicate a desired mode and sub-mode, namely transmit or receive mode, and potential sub-modes including any bypass modes, urban/rural modes or so forth. Next at block320, the front end control signals may be decoded, e.g., in the controller of the RF front end circuit.

Still with reference toFIG.3, control passes to block330where switch circuitry of the RF front end circuit may be dynamically configured based at least in part on these decoded signals. In an embodiment as inFIG.2, the single pole multiple throw switches may be controlled to provide a selected connection between a common port and a given one of the available throw ports. At this point the RF front end circuit is appropriately configured for operation in a given mode. As such, at block340RF signals may be communicated through the RF front end circuit via this configured switch circuitry. In this way, transmit or receive RF signals may pass through at least some of the switch circuitry according to a desired path such that the RF signals may optionally pass through a single external SAW filter, which may be used for both transmit and receive modes. Understand while shown at this high level in the embodiment ofFIG.3, many variations and alternatives are possible.

Embodiments may be implemented in many different devices. Referring now toFIG.4, shown is a block diagram of a representative IoT device400that includes SAW filter circuitry as described herein. In the embodiment shown inFIG.4, IoT device400may be any connected device to provide a variety of different functionality. In the high level shown inFIG.4, IoT device400includes an integrated circuit405, e.g., a microcontroller, wireless transceiver that may operate according to one or more wireless protocols (e.g., WLAN-OFDM, WLAN-DSSS, Bluetooth, among others), or other device that can be used in a variety of use cases, including sensing, metering, monitoring, embedded applications, communications, applications and so forth, and which may be particularly adapted for use in an IoT device. In turn, integrated circuit405couples to a front end module490including switching circuitry492in accordance with an embodiment to enable both transmit and receive paths to leverage a single off-chip SAW filter485.

In the embodiment shown, integrated circuit405includes a memory system410which in an embodiment may include a non-volatile memory such as a flash memory and volatile storage, such as RAM. In an embodiment, this non-volatile memory may be implemented as a non-transitory storage medium that can store instructions and data. Such non-volatile memory may store instructions, including instructions for generating control signals (e.g., in the form of the front end mode control signals discussed above) for use in controlling switching of switching circuitry492as described herein.

Memory system410couples via a bus450to a digital core420, which may include one or more cores and/or microcontrollers that act as a main processing unit of the integrated circuit. In turn, digital core420may couple to clock generators430which may provide one or more phase locked loops or other clock generator circuitry to generate various clocks for use by circuitry of the IC.

As further illustrated, IC405further includes power circuitry440, which may include one or more voltage regulators. Additional circuitry may optionally be present depending on particular implementation to provide various functionality and interaction with external devices. Such circuitry may include interface circuitry460which may provide interface with various off-chip devices, sensor circuitry470which may include various on-chip sensors including digital and analog sensors to sense desired signals, such as for a metering application or so forth.

In addition as shown inFIG.4, transceiver circuitry480may be provided to enable transmission and receipt of wireless signals, e.g., according to one or more of a local area or wide area wireless communication scheme, such as Zigbee, Bluetooth, IEEE 802.11, IEEE 802.15.4, cellular communication or so forth via connection to front end module490, in turn coupled to an antenna495. Understand while shown with this high level view, many variations and alternatives are possible.

Note that an IoT device leveraging an embodiment may be, as two examples, an IoT device of a home or industrial automation network or a smart utility meter for use in a smart utility network, e.g., a mesh network in which communication is according to an IEEE 802.15.4 specification or other such wireless protocol.

Referring now toFIG.5, shown is a high level diagram of a network in accordance with an embodiment. As shown inFIG.5, a network500includes a variety of devices, including smart devices such as IoT devices, coordinator devices and remote service providers. In the embodiment ofFIG.5, a mesh network505may be present, e.g., in a building having multiple IoT devices5100-n. Such IoT devices may include a single SAW filter and switching circuitry as described herein, to enable transmit and receive paths to leverage this single SAW filter. As shown, at least one IoT device510couples to a coordinator device530that in turn communicates with a remote service provider560via a wide area network550, e.g., the internet. In an embodiment, remote service provider560may be a backend server of a utility that handles communication with IoT devices510. Understand while shown at this high level in the embodiment ofFIG.5, many variations and alternatives are possible.

While the present disclosure has been described with respect to a limited number of implementations, those skilled in the art, having the benefit of this disclosure, will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations.