Device and method for reducing vibration effects on position measurement

A device (10) for reducing vibration effects on position measurement includes a receiver (12) for providing position signals (13); and a vibration control circuit (18) operative to control position information generation based on the position signals (13), to prevent position information generation during mechanical vibration of the device (10). A method for reducing vibration effects on position measurement includes receiving position signals through a receiver; and controlling position information generation based on the position signals to prevent the position information generation during mechanical vibration of the device.

BACKGROUND OF THE INVENTION

Electronic devices, such as cellular telephones, Internet appliances, personal digital assistants (PDA) and other devices are being used for more than just providing voice and visual communication between parties. Today, such electronic devices are equipped with position measurement circuitry, such as global positioning system (GPS) measurement or other non-satellite based position measurement circuitry that is capable of determining the position of the electronic device relative to a given point. For example, cellular telephones include one or more antennas for receiving voice, data and position signals, a processor which formats or otherwise filters the received signals, a vibrator for providing the user with an indication that a voice or data signal has been received and a reference signal generator, such as a temperature compensated reference oscillator or crystal oscillator that provides control signals that, among other things, control position measurement operations.

Position measurements are sensitive to small changes or variations in control signal frequency, which may be caused by mechanical vibration. Conventional methods employed to reduce the effects of vibration on position measurements include mechanically reinforcing the position measurement circuitry to the device housing or other interior portions of the device. A drawback associated with mechanical reinforcement is that it takes up relatively large amounts of space within the device housing; thereby increasing the overall size of the device. With the ever increasing importance of scaling down, or reducing, the size of mobile and non-mobile electronic devices, mechanical reinforcement impedes any size reduction efforts, and may not be achievable in very compact devices of the type preferred by consumers.

DETAILED DESCRIPTION OF THE INVENTION

A method dynamically reduces the adverse effects on efficiency caused by generating position information during mechanical vibration of the device. The position information may be generated as a result of performing a position measurement operation, such as a GPS measurement or other suitable position measurement calculation, and the vibration may be caused by the activation of a vibrator or other disturbance such as the device being dropped or shaken. In an exemplary embodiment of the present invention, a mobile communication device, such as a cellular telephone includes a receiver for providing position signals; and a vibration control circuit operative to control position information generation, such as by shutting off or otherwise deactivating a vibrator during position information generation, pausing position information generation until the vibration is terminated, or aborting position information generation based on the position signals, to prevent position information generation during mechanical vibration of the device.

Variations in control signal frequency may, for example, be caused by the electronic device being shaken, or the reference signal generator being disturbed in some fashion, while a position is being determined. For example, when a vibrator mechanically coupled to the position generator becomes active, the reference signal generator, along with the other components of the electronic device, will shake. This shaking may cause the control signal to have varying frequency characteristics. It is possible that in some devices, position measurement performance may be degraded, such as by requiring more time to calculate the position, when the device vibrates. The present invention permits an increase in the position generator's efficiency, such as by decreasing the time required to determine the position, by not performing vibration sensitive position identifying operations while vibrations occur. As a consequence, unnecessary battery consumption can be avoided, or shared resources used for position location can be allocated to other more beneficial operations while position detection performance is not optimum. An exemplary embodiment of the present invention will now be described with reference toFIGS. 1-6.

FIG. 1is a schematic block diagram of a device employing the vibration control circuit and method of the present invention. The device10can be embodied as any suitable mobile communication device including, but not limited to, a global positioning device, a cellular telephone, Internet appliance, laptop computer, palmtop computer, personal digital assistant, or a combination thereof such as a global positioning device accessory mechanically coupled to a communication device. For purposes of illustration only, a cellular telephone is exemplified, and includes: a position detector such as a position signal receiver12; a cellular transceiver14; a reference signal generator16, such as a temperature compensated reference oscillator (TCXO), a vibration control circuit18; a position measurement circuit19; and a vibrator26. The position signal receiver12may include, for example, an antenna and a filter or other suitable demodulation mechanism capable of converting position signals included as part of received satellite or non-satellite network data11, into position signals13having a format suitable for processing by the position measurement circuit19.

The position measurement circuit19generates position information20(e.g. x-y coordinates, latitude/longitude coordinates, or other suitable information) relating to the location of the device10by processing the position signals13according to a suitable (e.g. GPS) protocol. The position information20may then be provided to an application21, for example, a mapping program or display application for further use therein. Additionally, the position information20may be provided to the cellular transceiver14for transmission to a central location (not shown) for additional processing. In application, the position measurement circuit19is a software application executed by controller40, which is represented as a processor. However, it will be appreciated by one of ordinary skill in the art that the position measurement circuit19may be implemented in any suitable structure such as, but not limited to, a digital signal processor (DSP), a dedicated piece of hardware (e.g. ASIC), discrete logic circuitry, state machine or any device that manipulates signals based on operational instructions or software executing on one or more processing devices, capable of generating position information20based on the position signals13, firmware or any suitable combination thereof. The operational instructions or software would be stored in a memory (not shown), which may include a single memory device or a plurality of memory devices. Such a memory device may include any memory element that stores digital data including, but not limited to, RAM, ROM, distributed memory such as servers on a network, or CD-ROM.

The cellular transceiver14may include an antenna and/or modulation and demodulation circuitry capable of converting, for example, voice and/or image data, also present in the satellite or non-satellite network data11into cellular signals15having a format suitable for manipulation and processing by the vibration control circuit18. Voice and/or image data17may be provided by the vibration control circuit18to the cellular transceiver14for transmission over a cellular network.

The vibration control circuit18generates a processing control signal35, for example, an interrupt that controls the operation of the position measurement circuit19to prevent the position measurement circuit19from performing position information generation operations during mechanical vibrations of the device. As used herein, control includes pausing or aborting position information generation when the device10is vibrating or otherwise disturbed, or placing the vibrator26in an inactive state and allowing position information generation to occur when the vibrator26is in the inactive state. The vibration control circuit18generates a vibration control signal25, in response to a vibration event, such as receiving an incoming call alert in cellular signals15. Additionally, the vibration control circuit18can control the operation of the vibrator26, such that the vibrator is not active during position measurement operations. By preventing position information generation from being performed during periods of device vibration and controlling vibrator26operation, the position measurements performed by the position measurement circuit19are more accurate while, at the same time, preventing some wear and tear on underlying device components.

The vibration control circuit18may be implemented in any suitable structure such as, but not limited to, a DSP, an ASIC, a discrete logic circuit, a state machine or any device that manipulates signals based on operational instructions or software executing on one or more processing devices, or any suitable combination thereof. The operational instructions or software may be stored in a memory (not shown), which may include a single memory device or a plurality of memory devices. Such a memory device may include any memory element that stores digital data including, but not limited to, RAM, ROM, distributed memory such as servers on a network, or CD-ROM. In application, the vibration control circuit18is a software application being executed by the controller40, which is represented as a processor.

The vibrator26alerts the user of the device10of receipt of incoming cellular (e.g. voice and/or image) signals15. The vibrator26is switchable between an active (e.g. vibrating) state and an inactive (e.g. non-vibrating) state based on the vibration control signal25provided by the vibration control circuit18. In operation, when an incoming cellular signal15is received by the vibration control circuit18, the vibration control signal25is asserted, thereby, causing the vibrator26to vibrate which alerts the user of an incoming cellular signal15. If no cellular signal15is received, or position information generation is being performed by the position measurement circuit19, the vibration control signal25is de-asserted, thereby deactivating the vibrator26. At the conclusion of vibration sensitive operation, or position signal generation, the vibrator may be activated to alert the user of the incoming call.

Although described as including a vibrator26, it will be recognized and appreciated that there are alternate embodiments to the above illustrated embodiment. For example, the vibrator26may be replaced with a non-vibrating alert mechanism such as a light emitter or tone generator operable during position detection. Alternatively, an optional vibration detection circuit28may be operatively coupled to the vibration control circuit18. The vibration detection circuit28detects other vibration events, for example, when at least a portion of the device10is being shaken or otherwise disturbed (e.g. dropped) and provides a vibration detection signal27to the vibration control circuit18indicating such an event. In response to the vibration detection signal27, the vibration control circuit18provides the processing control signal35to the position measurement circuit19, which controls the operation of the position measurement circuit19to prevent position information generation during mechanical vibrations of the device10. Such a vibration detector can be employed in devices including, or not associated with a vibrating alert. The vibration detection circuit28may be an accelerometer or other suitable component capable of detecting mechanical vibrations of at least a portion of the device10, such as the portion of a multiple component device including a position measurement circuit.

As illustrated, the reference signal generator16is a temperature compensated reference oscillator (TCXO) that provides control signals30-32which control the timing of the vibration control circuit18, including the position measurement circuit19, the position signal receiver12and the cellular transceiver14. In application, the TCXO16provides a 26 MHz control signal30to the position signal receiver12; a 26 MHz control signal31to the cellular transceiver14and a 26 MHz control signal32to the vibration control circuit18. Although described as being a temperature compensated reference oscillator, the reference signal generator16may also be a crystal oscillator or other suitable signal generator. The TCXO16is very sensitive to vibrations or other disturbances. When the TCXO16vibrates, or is otherwise disturbed, the resulting control signals30-32deviate from normal baseline range. For example, when the TCXO16is shaken, the control signals30-32may experience low frequency modulation variations, which may have an adverse effect on the operation of the several components that are controlled by the TCXO16.

FIG. 2is a graph of sideband noise versus frequency offset in a situation where the TCXO16is shaken or otherwise disturbed without the vibration control of the present invention. As shown inFIG. 2, at the lower frequencies the control signal32provided to the vibration control circuit18exhibits a variance range, for example, from between−88 dBc at 100 hz to approximately−104 dBc at 1 Khz. Such modulation of the control signal32causes the transmission of data to the vibration control circuit18to be erratic and/or causes the position measurement circuit19to operate incorrectly. Either situation will result in an inaccurate position measurement being performed. A principal cause of TCXO16disturbance, and hence control signal modulation, is the vibrator26. The present invention substantially reduces or eliminates the adverse effects on position measurements or position information generation due to vibrations by controlling the performance of position information generation during operation of the device10such that position information generation is not performed during any vibration or disturbance conditions.

FIG. 3is a flowchart of the operating steps performed by the device10for controlling position information generation according to the present invention. The process begins at step100where a determination is made as to whether an incoming position signal is received, for example, by the position measurement circuit19polling its input for an incoming position signal. If a position signal is not received, the current device10state is maintained.

If a position signal is received, the process continues to step102, where the vibration control circuit18controls the position information generation based on the position signals to prevent position information generation during mechanical vibrations of the device10. Exemplary operating steps performed by the vibration control circuit18to control position information generation are illustrated inFIGS. 4 and 5.

FIG. 4presents the situation during the processing of the position signals by the position measurement circuit19such as when the processing is almost complete or, alternatively, position information generation is about to start. In step104the vibrator26is deactivated, for example, by the vibration control circuit18de-asserting the vibration control signal25; thereby preventing the vibrator26from vibrating during the position information generation.

In step106, position information generation is initiated or continued by the position measurement circuit19processing the position signals13provided by the position signal receiver12according to a GPS or other suitable position measurement protocol. The specifics of the GPS position measurement protocol are well known to those of ordinary skill in the art and will not be further discussed herein so as not to obscure the disclosure or deviate from the description of the present invention. Position information generation is not initiated or continued until after the vibrator26is deactivated. In this manner, position information generation is allowed to occur when the vibrator26is in the inactive state. Thus, any vibration or other disturbances caused by the vibrator26is avoided and will have no adverse effects on control signal generation and receipt or position information generation.

In step107, a determination is made as to whether position information generation is complete, for example, by detecting termination of the GPS position measurement protocol. If position information generation is not complete, the method returns to step106until position information generation is completed. As shown in step108, if the position information is complete, the vibrator26is switched to the active state, for example, by the vibration control circuit18asserting the vibration control signal25, such that the user may then be alerted as to any incoming voice or data signals.

FIG. 5presents the situation where a cellular signal15is received by the vibration control circuit18while the position measurement circuit19is processing the position signals according to a suitable position measurement protocol. In step103position information generation is paused by the vibration control circuit18sending the processing control signal35to interrupt any calculations being performed by the position measurement circuit19; thereby, allowing the incoming cellular signal15to be processed by the vibration control circuit18. Any intermediate position information generated at the time of pausing, may be stored for subsequent use. The received cellular (e.g. non-position information) signal15causes the vibration control circuit18to activate the vibrator26, by asserting the vibration control signal25, in step105in order to alert the user of the receipt of the cellular signal15or other non-position information.

In step109, a determination is made as to whether the vibrator26is to remain active, indicating that the user has not acknowledged the alert. If the alert has not been acknowledged, the method returns to step105until the alert is acknowledged. Otherwise, the method continues to step109.

In step110, position information generation is re-initiated from where earlier paused by the vibration control circuit18terminating the processing control signal35Thus, the stored intermediate position information may be used in completing the position information generation. Optionally, the stored intermediate position information may be discarded and position information generation may be performed anew using the position signals13from the position signal receiver12.

Alternatively, in step103, the position information generation may be aborted in favor of the incoming cellular signal15or other non-position information. After notifying of the user of the incoming cellular signal15in step105and acknowledgement by the same, the vibration control circuit18may restart the position information generation operation in step110.

Thus, among other advantages, the device and method of the present invention prevents vibrations caused, for example, by the vibrator26turning on or the device10being dropped or otherwise disturbed, from adversely affecting position information generation operations of the position measurement circuit19. When position information generation is being performed, the vibrator26is deactivated so as not to disturb the control signal provided by the TCXO16, or disturb the position information generation. Upon completion of position information generation, the vibrator26is activated; thereby, providing the ability to notify the user of any subsequent receipt of cellular signals15or other non-position information. Additionally, depending on how far along in the pending position measurement the position measurement circuit19is, the position information generation may be paused or aborted in favor of an incoming cellular signal15.

FIG. 6is a graph representing one example of sideband noise verses frequency. offset of the control signal provided by the TCXO16after application of the method of the present invention. Line42represents a normalized version of the sideband noise contained in the output signal of the TCXO16during operations when the vibrator26is active. As shown, at low frequencies, the sideband noise can obtain a value of approximately −24 dBc. By deactivating the vibrator26, or otherwise preventing the device10from performing position information generation during shaking, the output of the TCXO16will be improved as illustrated by line44. As shown, the maximum sideband noise provided by the TCXO16when the vibrator is dynamically controlled according to the present invention is about −34dB. Thus, in this example, the control signal noise resulting from application of the present invention is more than 5dBc less than when not controlled. As discussed above, performing GPS measurements requires a substantially stable clock at low frequency as the GPS measurements are very sensitive to even minor disturbances in the control signal. Reducing the amount of sideband distortion by more than 5dB is significant in that it results in a more stable control signal, which provides for a more readily calculated position measurement. Thus, by employing the method of the present invention, the position information generated by the position measurement circuit19can be generated more efficiently as compared to devices which do not deactivate or otherwise control the vibrator or position measurement circuitry to prevent generating position information during vibrations of at least a portion of the device.

The above detailed description of the invention and the examples described therein have been presented for the purposes of illustration and description. While the principles of the invention have been described above in connection with a specific device, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of the invention.