Radio device having dynamic intermediate frequency scaling

Methods and apparatuses are provided for dynamic frequency scaling of an intermediate frequency (IF) signal within a radio device.

BACKGROUND

The subject matter disclosed herein relates to electronic devices, and more particularly to methods and apparatuses for use in a radio device.

2. Information

Wireless communication systems are fast becoming one of the most prevalent technologies in the digital information arena. Satellite and cellular telephone services and other like wireless communication networks may already span the entire globe. Additionally, new wireless systems (e.g., networks) of various types and sizes are added each day to provide connectivity among a plethora of devices, both fixed and portable. Many of these wireless systems are coupled together through other communication systems and resources to promote even more communication and sharing of information. Indeed, it is not uncommon for some devices to be enabled to communicate with more than one wireless communication system and this trend appears to be growing.

Another popular and increasingly important wireless technology includes navigation systems and in particular satellite positioning systems (SPS) such as, for example, the global positioning system (GPS) and other like Global Navigation Satellite Systems (GNSS). SPS radios, for example, may receive wireless SPS signals that are transmitted by a plurality of orbiting satellites of a GNSS. The SPS signals may, for example, be processed to determine a global time, a range or pseudorange, an approximate or accurate geographical location, altitude, and/or speed associated with a device having the SPS radio.

SUMMARY

Methods and Apparatuses are provided for dynamic frequency scaling of an intermediate frequency (IF) signal within a radio device.

In accordance with one exemplary aspect, a method may be provided that includes receiving an RF signal, and based, at least in part, on an environment parameter, selectively frequency down-converting the received RF signal to either a corresponding first intermediate frequency (IF) signal having a first center frequency, or a corresponding second IF signal having a second center frequency, wherein the second center frequency is greater than the first center frequency. Here, the environment parameter may be related to an environment internal and/or external to a device.

For example, in certain implementations, the method may include frequency down-converting the received RF signal to the corresponding first IF signal if the environment parameter is less than a threshold parameter, and/or frequency down-converting the received RF signal to the corresponding second IF signal if the environment parameter is equal to or greater than the threshold parameter. In some example implementations, the threshold parameter may be programmably and/or dynamically established, and/or at least one of the first center frequency and/or the second center frequency is programmably and/or dynamically established in certain example implementations, the method may include accessing a first local oscillator (LO) signal operatively enabled for use in frequency down-converting the received RF signal to the corresponding first IF signal, accessing a second LO signal operatively enabled for use in frequency down-converting the received RF signal to the corresponding second IF signal.

In accordance with another exemplary aspect, an apparatus may be provided that includes a receiver circuit operatively enabled to receive an RF signal and, based, at least in part, on an environment parameter, selectively frequency down-convert the received RF signal to either a corresponding first IF signal having a first center frequency, or a corresponding second IF signal having a second center frequency, wherein the second center frequency is greater than the first center frequency.

In accordance with yet another exemplary aspect, an apparatus may be provided that includes means for receiving an RF signal, and means for selectively frequency down-converting the received RF signal to either a corresponding first IF signal having a first center frequency, or a corresponding second IF signal having a second center frequency based, at least in part, on an environment parameter, and wherein the second center frequency is greater than the first center frequency.

In accordance with still another exemplary aspect, an article of manufacture may be provided that includes a computer readable medium having stored thereon. The computer implementable instructions, if implemented by one or more processing units, may operatively enable the processing unit(s) to access an environment parameter, and based, at least in part, on the environment parameter, selectively enable a receiver circuit operatively enabled to receive an RF signal to frequency down-convert the received RF signal to either a corresponding first IF signal having a first center frequency, or a corresponding second IF signal having a second center frequency, wherein the second center frequency is greater than the first center frequency.

In accordance with an aspect of the present description, an IF frequency may be selectively changed (even dynamically changed) in response to a wireless signaling environment and/or device operating modes. In the presence of a potential jamming wireless signal, the IF frequency may, for example, be increased to possibly avoid excessive SPS receiver desense due to jamming signal distortion (e.g., IM2distortion). In the absence of such a jamming wireless signal, the IF frequency may be decreased to reduce power consumption, for example, in certain baseband circuitry.

DETAILED DESCRIPTION

Methods and Apparatuses are provided for dynamic frequency scaling of an intermediate frequency (IF) signal within a radio device. The frequency of an IF signal may, for example, be scaled up or down in response to one or more “environment parameters”. By way of example, an environment parameter may be associated with one or more wireless signals within the environment internal and/or external to the radio device. Such wireless signals may emanate from within the radio device itself and/or from one or more other devices. It may be useful to scale the center frequency of an IF signal to provide improved performance in such a wireless environment. In another example, an environment parameter may be associated with one or more operating modes associated with the device. It may be useful to scale the center frequency of an IF signal to provide better support for one or more operating modes.

FIG. 1is a block diagram illustrating an exemplary environment100that includes a device102having at least one radio operatively enabled to provide dynamic intermediate frequency scaling in accordance with certain exemplary implementations of the present description.

Wireless environment100may be representative of any system(s) or a portion thereof that may include at least one device102enabled to transmit and/or receive wireless signals to/from at least one wireless system104. Device102may, for example, include a mobile device or a device that while movable is primarily intended to remain stationary. Thus, as used herein, the terms “device” and “mobile device” may be used interchangeably as each term is intended to refer to any single device or any combinable group of devices that may transmit and/or receive wireless signals.

With this in mind and by way of example but not limitation, as illustrated using icons inFIG. 1, device102may include a mobile device such as a cellular phone, a smart phone, a personal digital assistant, a portable computing device, a navigation device, and/or the like or any combination thereof. In other exemplary implementations, device102may take the form of a machine that is mobile or stationary. In still other exemplary implementations, device102may take the form of one or more integrated circuits, circuit boards, and/or the like that may be operatively enabled for use in another device.

Regardless of the form of device102, device102may include at least one radio operatively enabled to provide dynamic intermediate frequency scaling. The term “radio” as used herein refers to any circuitry and/or the like that may be enabled to receive wireless signals and/or transmit wireless signals. In certain implementations, two or more radios may be enabled to share a portion of circuitry and/or the like (e.g., a processing unit, memory, antenna, etc.).

By way of example but not limitation, in some of the examples presented herein device102may include a first radio that is enabled to receive wireless signals associated with at least one navigation system106(e.g., a satellite positioning system, and/or the like), and a second radio that is enabled to receive and/or transmit wireless signals associated with at least one wireless system104. Wireless system104may include, for example, a wireless communication system, such as, e.g., a wireless telephone system, a wireless local area network, and/or the like. Wireless system104may include, for example, a wireless broadcast system, such as, e.g., a television broadcast system, a radio broadcast system, and/or the like. In certain implementations, device102may be enabled only to receive wireless signals from wireless system104, while in other implementations mobile station102may be enabled only to transmit wireless signals to wireless system104.

As illustrated inFIG. 1, wireless system104may be enabled to communicate with and/or otherwise operatively access other devices and/or resources as represented simply by cloud110. For example, cloud110may include one or more communication devices, systems, networks, or services, and/or one or more computing devices, systems, networks, or services, and/or the like or any combination thereof.

Wireless system104may, for example, be representative of any wireless communication system or network that may be enabled to receive and/or transmit wireless signals. By way of example but not limitation, wireless system104may include a wireless wide area network (WWAN), a wireless local area network (WLAN), a wireless personal area network (WPAN), a wireless metropolitan area network (WMAN), a Bluetooth communication system, WiFi communication system, Global System for Mobile communications (GSM) system, Evolution Data Only/Evolution Data Optimized (EVDO) communication system, Ultra Mobile Broadband (UMB) communication system, Long Term Evolution (LTE) communication system, Mobile Satellite Service-Ancillary Terrestrial Component (MSS-ATC) communication system, and/or the like.

The term “network” and “system” may be used interchangeably herein. A WWAN may be a Code Division Multiple Access (CDMA) network, a Time Division Multiple Access (TDMA) network, a Frequency Division Multiple Access (FDMA) network, an Orthogonal Frequency Division Multiple Access (OFDMA) network, a Single-Carrier Frequency Division Multiple Access (SC-FDMA) network, and so on. A CDMA network may implement one or more radio access technologies (RATs) such as cdma2000, Wideband-CDMA (W-CDMA), to name just a few radio technologies. Here, cdma2000 may include technologies implemented according to IS-95, IS-2000, and IS-856 standards. A TDMA network may implement Global System for Mobile Communications (GSM), Digital Advanced Mobile Phone System (D-AMPS), or some other RAT. GSM and W-CDMA are described in documents from a consortium named “3rd Generation Partnership Project” (3GPP). Cdma2000 is described in documents from a consortium named “3rd Generation Partnership Project 2” (3GPP2). 3GPP and 3GPP2 documents are publicly available. A WLAN may include an IEEE 802.11x network, and a WPAN may include a Bluetooth network, an IEEE 802.15x, for example. Such location determination techniques described herein may also be used for any combination of WWAN, WLAN, WPAN, WMAN, and/or the like.

Wireless system104may, for example, be representative of any wireless broadcast system that may be enabled to at least transmit wireless signals. By way of example but not limitation, a wireless broadcast system may include a MediaFLO system, a Digital TV system, a Digital Radio system, a Digital Video Broadcasting-Handheld (DVB-H) system, a Digital Multimedia Broadcasting (DMB) system, an Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) system, and/or other like systems and/or related broadcast techniques.

Device102may be enabled to at least receive wireless signals from at least one navigation system106which is illustrated inFIG. 1as a satellite positioning system (SPS) having a plurality of SPS signal transmitting satellites106-1,106-2,106-3, . . . ,106-x.Those skilled in the art will recognize that navigation system106may include additional transmitting and/or other supporting resources in addition to or instead of the satellites as illustrated.

In certain implementations, navigation system106may be enabled to provide other non-navigation related services (e.g., communication services, or the like). As such, in certain implementations device102may be enabled to transmit wireless signals to navigation system106.

The space vehicles (SVs) of navigation system106may each be enabled to transmit a unique SPS signal of which, at least a portion, may be received by device102and used in some manner for navigation, for example, to determine a time, a range, a location, a position, etc. The specific navigation signaling and location determining techniques may vary depending on the navigation system(s) being used. Such SVs may be enabled to transmit one or more signals at the same and/or at different carrier frequencies. For example, a GPS satellite may be enabled to transmit L1C/A and L1C signals in the same band, as well as, the L2C and L5signals at other carrier frequencies, etc. Furthermore, such SPS signals may include encrypted signals.

A SPS typically includes a system of transmitters positioned to enable entities to determine their location on or above the Earth based, at least in part, on signals received from the transmitters. Such a transmitter typically transmits a signal marked with a repeating pseudo-random noise (PN) code of a set number of chips and may be located on ground based control stations, user equipment and/or space vehicles. In a particular example, such transmitters may be located on Earth orbiting SVs. For example, a SV in a constellation of Global Navigation Satellite System (GNSS) such as Global Positioning System (GPS), Galileo, Glonass or Compass may transmit a signal marked with a PN code that is distinguishable from PN codes transmitted by other SVs in the constellation. In accordance with certain aspects, the techniques presented herein are not restricted to global systems (e.g., GNSS) for SPS. For example, the techniques provided herein may be applied to or otherwise enabled for use in various regional systems, such as, e.g., Quasi-Zenith Satellite System (QZSS) over Japan, Indian Regional Navigational Satellite System (IRNSS) over India, Beidou over China, etc., and/or various augmentation systems (e.g., an Satellite Based Augmentation System (SBAS)) that may be associated with or otherwise enabled for use with one or more global and/or regional navigation satellite systems. By way of example but not limitation, an SBAS may include an augmentation system(s) that provide integrity information, differential corrections, etc., such as, e.g., Wide Area Augmentation System (WAAS), European Geostationary Navigation Overlay Service (EGNOS), Multi-functional Satellite Augmentation System (MSAS), GPS Aided Geo Augmented Navigation or GPS and Geo Augmented Navigation system (GAGAN), and/or the like. Such SBAS may, for example, transmit SPS and/or SPS-like signals that may also be interfered with by certain wireless communication signals, etc. Thus, as used herein an SPS may include any combination of one or more global and/or regional navigation satellite systems and/or augmentation systems, and SPS signals may include SPS, SPS-like, and/or other signals associated with such one or more SPS.

To estimate its location, device102may determine pseudorange measurements to SVs that are “in view” of its receiving radio using well known techniques based, at least in part, on detections of PN codes in signals received from the SVs. Such a pseudorange to a SV may be determined based, at least in part, on a code phase detected in a received signal marked with a PN code associated with the SV during a process of acquiring the received signal at the receiving radio. To acquire the received signal, device102may, for example, be enabled to correlate the received signal with a locally generated PN code associated with a SV. For example, device102may correlate such a received signal with multiple code phase and/or Doppler frequency shifted versions of such a locally generated PN code. Detection of a particular code phase and/or Doppler frequency shifted version yielding a correlation result with the highest signal power may indicate a code phase associated with the acquired signal for use in measuring pseudorange as discussed above.

Thus, in certain implementations, device102may be enabled to determine its location in such a manner or other like manner without additional support from other devices or resources. In other implementations, however, device102may be enabled to operate in some manner with one or more other devices or resources, as for example represented by cloud110connected to wireless system104, to determine its location and/or to support other navigation related operations. Such navigation techniques are well known.

In certain implementations, device102may be enabled to receive SPS signals from one or more GNSSs, such as, for example, GPS, Galileo, GLONASS, Compass, or other like system that uses a combination of these systems, or any SPS developed in the future, each referred to generally herein as a SPS. As used herein, an SPS will also be understood to include pseudolite systems.

Pseudolites are ground-based transmitters that broadcast a PN code or other ranging code (similar to a GPS or CDMA cellular signal) modulated on an L-band (or other frequency) carrier signal, which may be synchronized with GPS time. Each such transmitter may be assigned a unique PN code so as to permit identification by a remote receiver. Pseudolites may be useful in situations where signals from an orbiting SV might be unavailable, such as in tunnels, mines, buildings, urban canyons or other enclosed areas. Another implementation of pseudolites is known as radio-beacons. The terms “satellite” and “SV”, as used herein, are interchangeable and intended to include pseudolites, equivalents of pseudolites, and possibly others. The term “SPS signals”, as used herein, is intended to include SPS-like signals from pseudolites or equivalents of pseudolites.

A receiver circuit within device102may be enabled to acquire a wireless signal. For example, a receiver circuit may receive a wireless signal (e.g., radio frequency (RF) signal) and down-convert the RF signal to a corresponding intermediate frequency (IF) signal and then further process the intermediate signal (if needed) to identify information that may be included within the wireless signal. Such an IF signal may have a center frequency that is scaled in some manner, in accordance with an aspect of the present description, to account to certain environmental conditions and/or the operation of device102. For example, environment100may include other devices such as transmitter120that may transmit (intentionally or unintentionally) wireless signals121that may interfere in some manner with device102as it attempts to acquire SPS signal107. By selectively scaling (changing) the center frequency of the IF signal in the presence and/or absence of such a potential jamming signal(s), device102may improve performance in some manner. In other instances, device102may be operated in certain modes in which selective frequency scaling of the IF signal (up and/or down) may prove beneficial.

With this dynamic intermediate frequency scaling capability in mind, attention is drawn next toFIG. 2, which is a block diagram illustrating certain features of an exemplary device102.

Device102may, for example, include at least one receiver circuit202that may be enabled to receive at least one RF signal222. RF signal222may, for example, include an SPS signal, and/or the like.

Receiver circuit202may, for example, include and/or otherwise be operatively coupled to a control circuit204. InFIG. 2the control circuit is shown as being within the receiver circuit. In other implementations all or part of the control circuit may be outside of the receiver circuit.

As illustrated in this example, receiver circuit202may also include a frequency down-converting circuit220, a signal generating circuit228, and a signal processing circuit226.

In this example, receiver circuit202may be enabled to selectively frequency down-convert received RF signal222to a corresponding intermediate frequency signal224, based, at least in part, on an environment parameter212. For example, based, at least in part, on environment parameter212, receiver circuit202may be enabled to selectively frequency down-convert received RF signal222to either a corresponding first IF signal having a first center frequency, or a corresponding second IF signal having a second center frequency. Here, for example, the second center frequency may be greater than the first center frequency. The resulting IF signal224may then be further processed in some manner by signal processing circuit226. It is noted for clarification that the use of “first IF signal” and “second IF signal” as used herein is not intended to describe initial and subsequent signals, for example as might occur in a typical two-stage receiver design.

In this example implementation, the selective frequency down-conversion process may be orchestrated by control circuit204, which may initiate, indicate, and/or otherwise operatively establish the selected IF frequency to frequency down-converting circuit220and/or signal generating circuit228.

As illustrated in this example, control circuit204may include one or more processing units206and memory208. In certain implementations, an article of manufacture may be accessed by control circuit204and may include a computer readable medium210upon which computer implementable instructions211may be stored.

Here, for example, processing unit206may be implemented within one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, electronic devices, other devices units designed to perform the functions described herein, and/or combinations thereof.

Memory208may include any type of memory that may be enabled to store information in the form of data. Some examples include a random access memory (RAM), a read only memory (ROM), a static memory, a dynamic memory, etc. Such stored information may include, for example, instructions211that may be implemented by processing unit206, and/or data associated with communications, location signals, measurements, parameters, location data, and/or the like. Such information may be stored on computer readable medium210which may be operatively coupled to one or more of processing unit206and/or memory208, for example. As illustrated inFIG. 2, for example, memory208may store data associated with environment parameter212, a threshold parameter214, a first center frequency216, a second center frequency218, and/or other like operational information. For example, memory208may also include data associated with one or more device operating modes238.

By way of example but not limitation, computer readable medium210may be included in an article of manufacture and may include some form of memory, one or more optical data storage discs, one or more magnetic storage disks or tapes, etc.

In certain example implementations, receiver circuit202may be enabled to frequency down-convert RF signal222to a first IF signal if environment parameter212is less than threshold parameter214, and a second IF signal if environment parameter212is equal to or greater than threshold parameter214. By way of example but not limitation, signal generating circuit228may be enabled to generate a local oscillator (LO) signal230that may be used by frequency down-converting circuit220to frequency down-convert RF signal222to produce corresponding IF signal224. Thus, in certain example implementations, signal generating circuit228may include circuitry that may be dedicated to generate a first LO signal for use in producing a first IF signal and additional circuitry that may be dedicated to generate a second LO signal for use in producing a second IF signal. In other example implementations, signal generating circuit228may be programmed to selectively generate either the first or the second LO signals, for example, based on and/or otherwise associated with first center frequency216or second center frequency218, respectively.

Control circuit204may, for example, be configured to receive and/or otherwise establish environment parameter212based on information associated with at least one of transmitter circuit232, a received wireless signal236(e.g., as identified here through a detector circuit234), and/or device operating mode238. By way of example but not limitation, in certain implementations environment parameters212may include or otherwise be associated with a transmitter power, a transmitter frequency (e.g., possibly coarse frequency information, band of operation, etc.), a transmitter bandwidth (e.g., as may be conveyed by a mode of operation such as 1× vs. WCDMA), and/or the like.

By way of example but not limitation, transmitter circuit232may be co-located with at least a portion of receiver circuit202as part of device102. Indeed, in certain implementations portions of transmitter circuit232and receiver circuit202may be implemented via a transceiver circuit (not shown). Transmitter circuit232may be enabled to transmit wireless signal105(seeFIG. 1), for example. In certain example implementations, environment parameter212may be established in some manner to identify an existing operation and/or expected operation of transmitter circuit232. For example, if transmitter circuit232is, or is about to begin, transmitting wireless signal105, then environment parameter212may be established accordingly. Here, for example, it may be beneficial to scale (e.g., switch) from a first IF signal to a second IF signal within receiver circuit202if transmitter circuit232is, or is about to begin, transmitting wireless signal105. Conversely, it may be beneficial to switch from a second IF signal to a first IF signal within receiver circuit202if transmitter circuit232is not transmitting wireless signal105.

In certain implementations, at least one threshold parameter214may be associated in some manner with transmitter circuit232. For example, threshold parameter214may be associated with a threshold signal power level and environment parameter212may be associated with a signal power level at which transmitter circuit232may be transmitting (or may soon be transmitting) wireless signal105. Hence, receiver circuit202may be enabled to frequency down-convert RF signal222to a first IF signal if environment parameter212is less than threshold parameter214, or a second IF signal if environment parameter212is equal to or greater than threshold parameter214.

By way of example but not limitation, detector circuit234may be co-located with at least a portion of receiver circuit202as part of device102. Indeed, in certain implementations portions of detector circuit234and receiver circuit202may be implemented together and/or be of similar design (e.g., detector circuit234may be associated with a receiver, a transceiver, etc. (not shown)). Detector circuit234may be enabled to receive and/or otherwise detect the presence of wireless signal236. For example, wireless signal236may include one or more of wireless signals105and/or121(seeFIG. 1). In certain example implementations, environment parameter212may be established in some manner to identify an existing presence and/or expected presence of wireless signal236. For example, if detector circuit234detects that wireless signals are being and/or may be transmitted then environment parameter212may be established accordingly. Here, for example, it may be beneficial to switch from a first IF signal to a second IF signal within receiver circuit202if detector circuit234detects that certain wireless signaling may occur. Conversely, it may be beneficial to switch from a second IF signal to a first IF signal within receiver circuit202if detector circuit234no longer detects or expects such wireless signaling to occur, e.g., in the immediate future. In certain implementations, threshold parameter214may be associated in some manner with detector circuit234. For example, threshold parameter214may be associated with a threshold signal power level and environment parameter may be associated with a signal power level associated with wireless signaling within the environment that may adversely affect the performance of receiver circuit202. Hence, receiver circuit202may be enabled to frequency down-convert RF signal222to a first IF signal if environment parameter212is less than threshold parameter214, and a second IF signal if environment parameter212is equal to or greater than threshold parameter214.

In another example, threshold parameter214may be associated with a maximum wireless signaling time period and environment parameter may be associated with a time measurement since wireless signaling was last detected. Here, receiver circuit202may be enabled to frequency down-convert RF signal222to a first IF signal if environment parameter212is greater than threshold parameter214, and a second IF signal if environment parameter212is equal to or less than threshold parameter214.

In other example implementations, threshold parameter214and/or environment parameter212may be associated with and/or identify certain frequencies, bands, channels, etc., associated with the wireless signaling that may be of interest when determining whether to scale the IF signal.

In certain example implementations, environment parameter212may be established in some manner to identify an existing and/or expected device operating mode238. By way of example but not limitation, device operating mode238may be associated with at least one of a device power consumption mode, a device communication mode, and/or a device navigation mode. It may be beneficial, for example, to switch from a first IF signal to a second IF signal within receiver circuit202depending on the device operating mode238. Thus, for example, if a device power consumption mode is intended to reduce power consumption then it may be beneficial to switch from a second IF signal to a first IF signal within receiver circuit202. Conversely, if a device power consumption mode is intended to no longer reduce power consumption (e.g., device may have been connected to charging and/or other like power source) then it may be beneficial to switch from a first IF signal to a second IF signal within receiver circuit202.

In another example, a device communication mode may identify pending transmission via transmitter circuit232, and/or identify that the device may be communicating in accordance with a specific transmission and/or reception mode. For example, for an initiating, testing, emergency, and/or other like communication mode it may be beneficial to employ a specific IF signal within receiver circuit202. In still another example, a device navigation mode may identify that the device may be operating in accordance with a specific navigation mode in which case it may be beneficial to select a specific IF signal within receiver circuit202.

In certain implementations, control circuit204may consider a variety of environment parameters212and/or threshold parameters214, for example, according to one or more algorithms or formulas to determine whether and/how to scale the frequency of an IF signal224.

Attention is drawn next toFIG. 3, which illustrates an exemplary method300that may be implemented to scale the IF frequency of a received a wireless signal. Method300may, for example, include at block302initially receiving at least one RF signal. At block304, method300may include selectively frequency down-converting the received RF signal to a corresponding IF signal having a selected center frequency within a range of frequencies and/or a plurality of frequencies. For example, at block304, method300may include selectively frequency down-converting the received RF signal to either a corresponding first IF signal having a first center frequency, or a corresponding second IF signal having a second center frequency based, at least in part, on at least one environment parameter. Here, for example, the second center frequency may be greater than the first center frequency.

As illustrated at block306, the environment parameter may be established. The environment parameter may, for example, be programmably and/or dynamically established. Environment parameter212(seeFIG. 2) may, for example, be associated with transmitter circuit that may be co-located in device102which also includes receiver circuit202enabled to receive RF signal222in accord with block302. Environment parameter212may, for example, be associated with received wireless signal236which may be detected and/or otherwise received by detector circuit234. Environment parameter212may, for example, be associated with at least one device operating mode238such as, e.g., a device power consumption mode, a device communication mode, a device navigation mode, and/or other like device operating modes.

In certain example implementations, block304may include frequency down-converting the received RF signal to the corresponding first IF signal if the environment parameter is less than a threshold parameter, or frequency down-converting the received RF signal to the corresponding second IF signal if the environment parameter is equal to or greater than the threshold parameter. Conversely, in other example implementations, block304may include frequency down-converting the received RF signal to the corresponding first IF signal if the environment parameter is equal to or greater than a threshold parameter, or frequency down-converting the received RF signal to the corresponding second IF signal if the environment parameter is less than the threshold parameter.

As illustrated at block308, the threshold parameter may, for example, be programmably and/or dynamically established. As illustrated at block310, at least one of the first center frequency and/or the second center frequency may, for example, be programmably and/or dynamically established. In certain exemplary implementations, the first center frequency may be between 0 Hz and 100 KHz. In certain exemplary implementations, the second center frequency may be greater than 0 Hz.

Block304may, for example, include accessing a first LO signal enabled for use in frequency down-converting the received RF signal to the corresponding first IF signal, and/or accessing a second LO signal enabled for use in frequency down-converting the received RF signal to the corresponding second IF signal. In certain implementations, block304may include establishing either the first LO signal and/or the second LO signal. By way of example, either the first LO signal and/or the second LO signal may be established, at least in part, using dedicated signal generating circuits and/or the like. In other example implementations, the first LO signal and/or the second LO signal may be established, at least in part, using a programmable signal generating circuit and/or the like (e.g., a phase-locked loop (PLL) that may be programmed to selected frequencies, etc.).

Reference is made next toFIG. 4, which is a block diagram illustrating certain features of an exemplary receiver circuit202that may, for example, be implemented in the environment ofFIG. 1and/or device ofFIG. 2.

Receiver circuit202as illustrated inFIG. 4has a digital low IF (LIF) architecture, with a single I/Q down-conversion stage and dual-channel ADC to digitize I and Q analog signals. The analog I/Q signals may, for example, include bandpass signals with nonzero center frequency. Final down-conversion to 0 Hz (if needed) may, for example, be implemented within signal processing circuit226(seeFIG. 2).

In this example implementation, the architecture may be enabled to degenerate to a zero IF (ZIF) receiver in the case where the IF frequency equals 0 Hz. From an RF/analog architecture standpoint, in certain instances a very low IF frequency (e.g., up to tens of kHz or even perhaps greater than 100 kHz) may not be significantly different from an IF frequency of exactly 0 Hz. References to ZIF operation herein may thus include such very low IF frequencies.

In accordance with an aspect of the present description, the IF frequency may be selectively changed (even dynamically changed) in response to the wireless signaling environment and/or device operating modes. In the presence of a potential jamming wireless signal, the IF frequency may, for example, be increased to possibly avoid excessive SPS receiver desense due to jamming signal distortion (e.g., IM2distortion). In the absence of such a jamming wireless signal, the IF frequency may be decreased to reduce power consumption, for example, in certain baseband circuitry.

Those skilled in the art should recognize that, given an amplitude (and possibly phase) modulated jamming signal aJ(t)cos(ωJt+θJ(t)) at the receiver input, for example, an IM2distortion may be identified with a term at the down-converting circuit output that may be proportional to aJ(t)2. IM2distortion may be produced by one or a combination of several circuit mechanisms. A direct mechanism may be the inherent second order nonlinearity of FET switches that may be included in a mixer core, and/or possibly exacerbated by transistor mismatch. Another mechanism may be coupling of the jamming signal from an input port of a mixer to a LO port, resulting possibly in jamming signal self-mixing. Another exemplary possibility may be that in down-conversion a jamming signal's second harmonic may be generated by LNA nonlinearity; e.g., if a LO duty cycle is not exactly 50 percent, it too may have a second harmonic component that down-converts (e.g., to baseband) the high frequency term in an LNA output.

The jamming signal of principal concern in certain example implementations may include a transmitter circuit (e.g., cellular, etc.) that may be co-located with the receiver circuit (e.g., SPS receiver) within the device. For example, in certain device operating modes, it may be desirable to operate the SPS receiver simultaneously with the cellular transceiver. Such operation may, however, pose an especially difficult problem in a frequency division duplex (FDD) system such as CDMA2000, wherein the transmitter circuit may be radiating continuously while in a connected state. Unfortunately, in many designs, a fraction of the output power may couple into the SPS receiver circuit which may degrade performance.

ComparingFIG. 2toFIG. 4, receiver circuit202is illustrated as an exemplary SPS receiver in which control circuit204(FIG. 2) may be implemented, at least in part, by IF control400ofFIG. 4. Also, signal generating circuit228(FIG. 2) may be implemented, at least in part, by the arrangement circuits such as TCXO414, PLL416, Loop filter418, VCO420, and/or LO generator422.

PLL416may be enabled to provide a timing signal to loop filter418. Loop filter418in turn provides a tuning signal to VCO420which may be enabled to provide feedback to PLL416and also a timing signal to LO generator422. LO generator422may be enabled to provide I and Q LO signals to IQ mixer408.

Here, for example, TCXO414may be enabled to provide a timing signal to PLL416. TCXO414is meant to be inclusive of a variety of reference oscillator types. For example, the reference may have a frequency tuning control (VCTCXO), or it may be a simpler crystal oscillator (XO) with neither frequency control nor temperature compensation circuits.

InFIG. 4, SPS signal107may be received via antenna402. Antenna402may be coupled to provide the received SPS signal as input signal to an RF filter404that may be enabled to attenuate energy outside the received SPS signal. RF filter404may be coupled to a low noise amplifier (LNA)406that may be enabled to amplify the received SPS signal. LNA406may be coupled to IQ mixer408which may be coupled to baseband filter (BBF)410and LO generator422. IQ mixer408may be enabled to down-convert the RF signal from LNA406to corresponding I and Q IF signals in accordance with the LO signal(s) from LO generator422. BBF410may then further remove out-of-band energy from the I and Q IF signals which may then be digitized by analog to digital converter (ADC)412. The corresponding digital I and Q data from ADC412may then be further processed in some manner by signal processing circuit226(FIG. 2). For example, signal processing circuit226may be enabled to process SPS signals accordingly to support at least the determination of location and/or navigation information.

IF control400may be enabled to selectively control and/or otherwise program BBF410, ADC412, and/or PLL416, for example, based upon environment parameter212(seeFIG. 2). For example, environment parameter212may be based on information about instantaneous transmitter output power associated with transmitter circuit232(FIG. 2). By way of example but not limitation, in certain chipsets that tightly integrate the SPS receiver with the cellular transceiver, such information may be readily available to software that controls the SPS receiver.

IF control400may be implemented through hardware, firmware, software, and/or a combination thereof. Programmable controls in the BBF, ADC, and PLL blocks may be exposed to a processing unit, for example, via registers, etc. within an integrated circuit.

Also shown inFIG. 4, receiver circuit202may include (optional) a bias control430that may be enabled to provide for dynamic bias scaling. Here, for example, bias control430may be enabled to adjust certain RF circuit parameters (e.g., LNA IP3, LO phase noise floor) to be robust in the presence of a strong jamming signal, and in the absence of such a jamming signal may re-adjust such parameters to reduce power consumption.

Bias control430may, for example, represent a central bias generation that provides bias current/voltage to LNA406, IQ mixer408, and LO generator422. Here, for example, LNA406, IQ mixer408, and LO generator422may have local bias generation circuits. Bias control430may, for example, represent software (programmable) control of integrated circuit registers, and/or the like. All or part of bias control430may be included within control circuit204(FIG. 2), for example.

In certain implementations signal generating circuit228and frequency down-converting circuit220may include one or more switches (not shown) that may, for example, selectively determine a LO signal to use in frequency down-converting an RF signal to a corresponding IF signal. In other implementations, it may be desirable to have an implementation that may avoid the use of such switches or other like switching circuitry.

With this in mind and by way of further example, reference is now made toFIG. 5, which shows an example implementation of a portion of a frequency down-converting circuit500that may be implemented in receiver circuit202ofFIG. 2.

As illustrated inFIG. 5, an RF signal502may be provided to a low phase noise down-converter504via buffer526and a low power down-converter506via buffer540. Down-converters504and506may be coupled to a VCO512via buffers516and530, respectively. VCO512may also be coupled to a PLL (not shown) via buffer514. Down-converter504may include, for example, mixers524and528each being coupled to buffer526. Down-converter504may include a phase divider518coupled to buffer516and providing corresponding signals to buffers520and522, wherein buffer520is coupled to mixer524and buffer522is coupled to mixer528. Down-converter506may include, for example, mixers538and542each being coupled to buffer540. Down-converter506may include a phase divider532coupled to buffer530and providing corresponding signals to buffers534and536, wherein buffer534is coupled to mixer538and buffer536is coupled to mixer542. An I output508may be provided by mixer528or542, and a Q output510may be provided by mixer524or538.

The output RF signal502of the LNA (not shown) may be provided to both down-converters through separate buffers526and540, with only one buffer526or540being active at any point in time. The non-active buffer526or540may present a high impedance to the LNA. Similarly, the output of the VCO512may be provided to both down-converters through separate buffers516and530, with only one buffer516or530being active at any point in time. Here, for example, the non-active buffer516or530may be configured to minimize loading of VCO512. Additionally, the output of VCO512may be provided to the PLL (not shown) via buffer514.

The outputs of the mixers may be tied together and/or provided to baseband filter circuits (not shown), for example. In its non-active state, the output of an RF input buffer526or540may be configured in a high impedance state to minimize the additional load presented to the output of the active down-converter.

Besides the cellular transmitter(s), other transmitters may be co-located with the SPS receiver and present similar difficulties during simultaneous operation. Examples of other transmitters and possible sources for jamming signals include Bluetooth and 802.11 wireless LAN. In chipsets that integrate such transceiver(s) with an SPS receiver, information about transmitter output power may be available to software that controls the SPS receiver.

As mentioned, in certain implementations, the selected IF signal frequency may influence power consumption within a device. For example, after down-conversion, certain analog circuits may be enabled to filter and amplify the baseband signal before passing it to the ADC. Assuming a fixed baseband gain requirement, the DC current required by such circuits tends to increase with bandwidth. Thus, at higher bandwidths, a higher device ωTmay be necessary to produce the required signal gain, and higher ωTmay be achieved by increasing bias current. For an exemplary CMOS FET implementation in a long channel approximation, the device ωTmay be proportional to (∝) the device transconductance, and the device transconductance may be proportional to the square root of the bias current. For an SPS signal with bandwidth B, the maximum frequency component of the signal at the down-converting circuit output may be fm=fIF+B/2. Thus, for example, if ωT∝fm, then it may be that IDC∝fm2=O(fIF2). Note that this quadratic growth of bias current with IF frequency may become a linear relationship for short channel devices. While an exact mathematical relationship between bias current and IF frequency may be implementation specific, it may be for most implementations that a bias current may increase as a function of IF frequency.

In certain example implementations, a DC current drain associated with ADC412operating at sufficiently high sampling frequencies may be dominated by dynamic switching current. Such current may, for example, increase linearly with the sampling frequency fs. According to the well-known Nyquist criterion, to avoid aliasing distortion the sampling frequency should be greater than twice the maximum frequency component fmof the signal, here, at the input of ADC412(assuming the IF frequency is small enough to rule out subsampling architectures). Thus, a choice of IF frequency may clearly influence the required sampling frequency. A higher IF frequency may yield a baseband signal with higher maximum frequency component. For example, a higher IF frequency may use higher baseband signal frequency components, higher sampling frequency, and/or higher DC current.

For an SPS signal with bandwidth B, the maximum frequency component at the input of ADC412may be fm=fIF+B/2. Thus, a sampling frequency may need to satisfy fs>2fm=2fIF+B. Consequently, the DC current may scale as IDC=O(fs)=O(fIF).

In addition to ADC412, other digital circuits (e.g., following ADC412) may need to be clocked at the sampling rate, and as such may require a DC current that scales in direct proportion to the IF frequency. Furthermore, although a crossover point at which dynamic current may dominate the total current consumption of ADC412may occur at quite a high sampling frequency, that crossover point will be very low for CMOS digital circuits.

In addition to a possible increase in sampling frequency, other ADC related changes may be recommended when the IF frequency is increased. For example, in ZIF mode ADC412may have a lowpass sigma delta architecture, with quantization noise transfer function having a zero at DC. In LIF mode it may be advantageous to switch to a bandpass sigma delta architecture, shifting the zero in the noise transfer function into the signal passband.

Reference is made next toFIG. 7, which includes four graphs that illustrate dynamic intermediate frequency scaling in accordance with an implementation and which may, for example, be implemented in the environment ofFIG. 1and/or device ofFIG. 2. More specifically,FIG. 7illustrates various BBF frequency responses in connection with dynamic IF scaling.

Line702inFIG. 7(a) may be associated with an exemplary narrowband lowpass filter, with bandwidth approximately equal to the SPS signal bandwidth. For example, a GPS C/A code receiver may utilize a filter with a bandwidth of ˜2 MHz. This BBF may provide an appropriate choice in ZIF mode. Since it provides no frequency separation from a jamming signal's IM2product, this configuration may be appropriate when a cellular transmitter or the like is inactive, and/or when radiated power may be sufficiently low enough that possible IM2interference power may not raise the thermal noise floor of the SPS receiver. Certain benefits of this example configuration may include a simple filter design and/or a relatively low DC power consumption.

As illustrated by line704inFIG. 7(b), the IF frequency has been increased, here for example to provide frequency separation from jamming signal IM2represented by line706. Such an IM2product may have a center frequency of 0 Hz, and its two-sided bandwidth may be twice the jamming signal bandwidth. Such an IM2product may also have a substantial DC component, as shown. If the SPS signal has bandwidth BSPSand the co-located transmitter bandwidth is BTX, then to avoid the IM2interference one may select an fIF>BTX+BSPS/2. In the example illustrated inFIG. 7(b), the IF frequency has been chosen as 5*1.023=5.115 MHz, which may be high enough for a GPS C/A code receiver (BSPS≈2.05 MHz) to avoid the IM2product generated by WCDMA reverse link (BTX≈3.84 MHz). Note that this choice of IF frequency may not, however, be high enough to avoid an IM2interference generated by possible adjacent channel emissions, e.g., associated with a WCDMA transmitter output, but that interference may have a much lower power level.

In certain example implementations, the choice of IF frequency may be dynamically selected based, at least in part, on the basis of a transmitter bandwidth. For example, an IF frequency may not need to be as high during a CDMA 1× voice call (BTX≈1.23 MHz) as during a WCDMA voice call. A lower IF frequency may enable reduced power consumption.

The BBF inFIG. 7(b) illustrates an exemplary translation of the narrowband response, such that the SPS signal may remain aligned with the filter center. Note, that such a resulting filter response may not be symmetrical in positive and negative frequencies; as this may be a complex filter.

FIG. 6shows an example of how such a filter600may be implemented, at least in part. Here, filter600may have an input602and an output608, with components604,606and610arranged there between. In this example, H(s)=(Ava)/(s+a) may be the transfer function of a 1st-order active filter with voltage gain Avand real pole at s=−a. With the complex multiplier jβ in the feedback path, e.g., via amplifier610, the overall response may be one of a 1st-order filter606with pole shifted off the real axis to the point s=−a+jAvaβ. To align the filter response with the SPS signal, the gain β may be chosen to satisfy Avaβ=2πfIF. The complex multiplier may be implemented, for example, by swapping I and Q components: Given a signal pair (I, Q) at the amplifier610input, the signal pair at the output may be (−βQ, βI).

One drawback of the filter inFIG. 7(b) may be the additional circuit complexity required to implement a complex filter. Moreover, the center frequency of the filter may require on-chip tuning to ensure alignment with the signal. With this in mind,FIG. 7(c) shows an alternative filter response (line708) that may be used with the same IF frequency. Here the complex filter may be replaced by a lowpass filter with wide bandwidth. This filter may not reject the IM2distortion product at all, so ADC412may be enabled to provide sufficient dynamic range to pass such distortion without saturation. The IM2product may then be subsequently removed, for example, by a digital filter and/or the like, after ADC412(e.g., within signal processing circuit226(seeFIG. 2)).

FIG. 7(d) illustrates a modified filter (line710) with the addition of a notch at DC, as may, for example, be accomplished by AC coupling the down-converter output. Such a notch may reject a large portion of the IM2product, which may relax ADC412dynamic range requirements in certain implementations. If the selected IF frequency704has a high enough center frequency, the notch may be fairly wide, which may also affect ADC dynamic range requirements.

Reference is made once again toFIG. 4. IF control400may, for example, be implemented, at least in part, using a software state machine and/or the like. An interrupt may be generated based, at least in part, on environment parameter212. For example, an interrupt may be generated by a DSP controlling transmitter circuit232when the transmitter produces or is about to produce output power that exceeds a corresponding threshold parameter214. Upon receiving such interrupt, processor unit206may initiate changes in IF signal frequency and/or receiver bias (e.g., switch the receiver circuit into high linearity mode). In certain implementations, such operational changes may be related to other aspects of transmitter circuit232and/or receiver circuit202, for example, such operational changes may occur based on band and/or channel of the transmitting signals.

In the absence of a strong jamming signal, receiver circuit202may be enabled as a ZIF receiver, which may reduce power consumption. In the presence of a strong jamming signal, the state machine may, for example, be enabled to initiate a transition to a LIF mode. Here, in certain implementations, the IF frequency in a LIF mode may be a function of transmitter band and/or channel, and/or transmitter bandwidth. For example, the IF frequency may be higher during 15 MHz LTE traffic in an AWS band than during 5 MHz LTE traffic in the AWS band.

Time and/or power hysteresis may be considered in certain implementations, for example, to possibly prevent the state machine from excessive toggling between states due to output power fluctuations. Since they may not carry great urgency, transitions to a state having a lower IF frequency might not be initiated by interrupt, but instead by low rate polling of output power, and/or other like measures.

Another exemplary interrupt generation mechanism may use digital logic and/or the like that may be enabled to consider in some manner a received signal strength (e.g., RSSI) from a cellular receiver (not shown). In certain other implementations it may be more beneficial, however, to consider transmitter output power, due to potentially different fading characteristics in uplink and downlink channels.

In certain other implementations, a more elaborate interrupt generation mechanism may be provided, for example, using analog and/or digital hardware and/or the like to provide detector circuit234in the form of a general-purpose jamming signal detector. Such a general-purpose jamming signal detector may be advantageous in certain implementations because it may enable an SPS receiver state to be adjusted not only on the basis of internally generated jamming signals, but also in response to external jamming signals. Furthermore such a jamming signal detector may not need to be coupled to a cellular transceiver and/or other like transmitter circuits.

In certain implementations receiver circuit202may need to be designed to consider possible discontinuities that may be introduced by changes of linearity state (e.g., via bias control430) and/or when the IF frequency is adjusted (e.g., via IF control400). Since PLL416may be reprogrammed and/or otherwise affected when the IF frequency changes, the PLL may unlock which may lead to an SPS signal outage while the PLL settles to its new frequency. Such a signal interruption should be limited to a few hundred microseconds, which should generally not adversely affect SPS receiver performance. For example, a GPS C/A code receiver may coherently integrate the signal for 20 ms; a signal outage of 0.2 ms in every coherent sum may degrade acquisition sensitivity by only ˜0.04 dB. Hysteresis may be implemented within the state machine to reduce the frequency of interruptions and/or prevent such interruptions from happening. While PLL416may be unlocked, the LO frequency may swing far outside the SPS band. It could potentially swing through a strong jamming signal, which in that instant may fall into the SPS receiver passband. Thus there may be a potential for strong interference to be injected into the SPS signal integration, degrading the signal-to-noise ratio (e.g. C/No). This possibility may be avoided, for example, by blanking the SPS receiver while the PLL is unlocked. When blanked, the I/Q samples passed to the signal processing circuit226(which may, e.g., include one or more correlator(s)) may be forced to zero or to some other small value. The state of the SPS receiver may be operatively frozen while it is blanked. For example, to prevent external interference from perturbing digital automatic gain control (AGC), the state of an amplitude estimator and/or the like (not shown) that drives AGC may be operatively frozen.

Those skilled in the art will recognize that other blanking methods may be implemented. For example, an SPS receiver LNA may be de-energized while the PLL is unlocked, thus attenuating any jamming signals that might be mixed into the signal band by the swinging VCO.

When switching between different filter configurations as depicted in the example graphs inFIG. 7, and particularly when switching between narrowband and wideband filters, the group delay through the SPS receiver may change. Any such changes in group delay should be compensated somewhere in the SPS receiver, to prevent degradation in fix accuracy. For example, a group delay jump of 1 ns corresponds to a jump of ˜30 cm in a pseudorange measurement. Jumps in group delay may be compensated, for example, by software in certain implementations. In other implementations, dedicated digital hardware may be used instead. For example, a tapped delay line (not shown) consisting of N registers updated at rate 1/T and/or the like may be used to implement a programmable delay of 0 to NT in coarse time steps. Fine group delay compensation may be implemented with a linear interpolation filter (not shown), which may be enabled to shift the location of the interpolation nodes. Such a shift of interpolation points is equivalent to a group delay shift.

In an exemplary LIF architecture, the image rejection ratio (IRR) of receiver circuit202may be determined, at least in large part, by the amplitude and phase imbalance of the LO. Unlike in the classical superheterodyne architecture, the RF filter may not be required to provide any suppression in the image band. An IRR of better than 20 dB may be achievable, and such an IRR may be sufficient provided that no strong jamming signals lie in the image band. Such a condition may be promoted by placing an upper bound on the IF frequency so that the image band lies in the same satellite radio navigation band as the desired signal.

For example, the GPS L1signal with carrier frequency 1575.42 MHz lies in the band 1559-1610 MHz allocated worldwide to satellite radio navigation. A C/A code receiver may have a passband of width 2 MHz centered at 1575.42 MHz, in which case the image band may also be 2 MHz wide. If this C/A code receiver is a low IF receiver using low side injection, the image band may be enabled to lie within 1559-1610 MHz, e.g., if a maximum allowed IF frequency is 7.71 MHz. For a low IF receiver using high side injection, a corresponding maximum allowable IF frequency may be 16.79 MHz. Here, for example, as the GPS signal is located left of band center, there may be more room to fit an image band on the high side.

In accordance with certain example implementations, methods and apparatuses may be implemented to frequency down-convert a received RF signal to a corresponding first IF signal to effect or otherwise enable a reduction in receiver power consumption, and/or frequency down-convert a received RF signal to a corresponding second IF signal to effect or otherwise enable improved receiver performance in the possible presence of jamming RF signals.

Thus, by way of example but not limitation, a trigger for lowering an IF frequency may include a directive to operate in a low power mode, in which there may be a performance degradation in the presence of jammers. Such a directive may be user initiated, for example when enabling an airplane mode (which disables the co-located transceiver), or at other times. Such a directive may be initiated by software instructions/modules that may be enabled to monitor a battery level or the like, such that if the battery level drops below a threshold level then the SPS receiver may enter a mode to conserve power.

Thus, in certain implementations, IF switching may be implemented based, at least in part, on transmitter power, band, and/or bandwidth. Such IF switching may be implemented to save power, for example, when the robustness of a LIF receiver may be overkill or otherwise excessive. Here, such power savings may be opportunistic, in the sense that one may save power as the environment dictates. Thus, a trigger for switching between LIF and ZIF may be inherently related to the transmitter.