Automatic fuse architecture

An automatic fuse architecture is described. An incoming signal is received and detected to determine whether the signal exceeds a threshold value.

BACKGROUND

The mobile communication industry is facing an increasing demand for high data rate applications (e.g., video, multimedia, and so forth). To meet this demand, standards like High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA) are being developed within the Universal Mobile Telecommunications System (UMTS) mobile phone standard. These higher data rates generally require better signal quality between a mobile device and a base station, where the mobile device may be a mobile phone and the base station may be a cellular tower.

The signal quality and range may be enhanced by increasing the number of base stations in order to reduce the maximum distance between a given base station and the mobile device. For example, in a cellular network system, increasing the number of cellular towers effectively decreases the distance between a given mobile device in the network and the nearest cellular tower. However, this solution would be cost prohibitive due in part to the high cost of installing and maintaining additional base stations.

The range of high data rate transfer within a communication system may also be increased using a primary antenna with a diversity antenna to create two receiver chains within the mobile device. According to a typical design, the primary antenna sends and receives signals, whereas the diversity antenna is dedicated to signal reception. The diversity antenna complements the primary antenna by preventing fading, where fading is defined by a reduction of signal quality and/or transmission rate.

The diversity antenna typically experiences an isolation effect with the primary antenna. The isolation effect may reduce the TX power of the signal that is received by the diversity antenna. A diversity antenna switch associated with the diversity antenna may be designed to take advantage of this isolation effect. For example, the so-called “front end” of the switch may be optimized by omitting typical primary filter components, such as the duplex filter and external low noise amplifier (LNA). Omitting these components results in cost and space savings, as well as other benefits.

Under normal operating conditions, the lack of the duplex filter and other front end components in the diversity receiver is acceptable due to the isolation that occurs between the primary antenna and the diversity antenna, which limits the signal power received by diversity antenna. However, under certain abnormal conditions, the isolation between the primary antenna and diversity antenna can be dramatically lowered. The abnormal conditions may be caused by placing the diversity antenna too close to, or on, a metal plate or by other abnormalities that the mobile device may experience. Under these and other abnormal conditions, relatively fragile and power sensitive components, such as a Surface Acoustic Wave (SAW) filter associated with the diversity antenna, may be exposed to power levels close to, or equal to, the fully transmitted signal power. The excessive signal power may damage or even destroy these components.

DETAILED DESCRIPTION

This disclosure describes the design and use of a switch for preventing a signal from reaching power sensitive components, such as filter elements, active devices and/or passive devices and so forth, under certain abnormal conditions. Some specific examples of power sensitive components include SAW filters, tunable filters, tunable matching circuits, isolators, circulators, Low Noise Amplifiers (LNAs), mixers, Analog-to-Digital Converter (ADCs), diplexers, and so forth.

In a described implementation, a diversity antenna system has an antenna switch to direct an incoming signal to one or more filter elements, where each filter element may handle a signal related to a particular signal frequency. The antenna switch may also have a detector to sense the power of the incoming signal. If the detector detects that the signal exceeds a predetermined threshold, the signal may be prevented from reaching the filter elements by directing the signal to a termination point.

According to another implementation, a device is described that receives an incoming signal from an antenna and outputs a signal to control logic. The device also includes a detection mechanism operable to determine the power of the incoming signal from the antenna and to communicate a signal to the control logic to direct the signal to either the filter or the termination point based upon the power of the incoming signal measured by the detector.

According to yet another implementation, a method is disclosed that includes detecting an incoming signal received by an antenna. If the signal is below a predetermined threshold, the signal may be directed to a filter element. If the signal exceeds the predetermined threshold, the signal may be directed to a termination point. The techniques described herein may be implemented in a number of ways. One example environment and context is provided below with reference to the included figures and on going discussion.

Exemplary Environment

FIG. 1shows a mobile communication system100having a base station102and one or more mobile devices104or106. The mobile communication system100is representative of a cellular network, in which the base station102represents a cellular phone tower or other device capable of transmitting and/or receiving one or more radio or other wireless signals108within a cell of a cellular network. The mobile devices104and106represent cellular phones, wireless media devices, or other devices capable of receiving and/or transmitting a radio or other wireless signal108. For example, the mobile device104or106may alternatively be a personal digital assistant (PDA), a portable computing device capable of wireless communication, a media player device, a portable gaming device, and/or a wireless access point (WAP). Mobile devices104and106may be identical, with mobile device104representing a device operating under normal conditions and mobile device106representing a device operating under abnormal conditions. The abnormal conditions may be caused, for example, by placing the mobile device106too near, or on, a metal plate110, a human body, or other obstacle. For convenience, mobile device104will be used for reference and any description thereof is applicable to mobile device106, unless otherwise indicated.

The mobile device104includes an antenna112to communicate with the base station102. Antenna112may be configured to transmit and/or receive the signal108and may represent a primary antenna and/or a diversity antenna. The signal108may initially be processed by antenna components114, which may include filters, receivers, transmitters, and so forth. The antenna components may send the signal to processing circuitry116. A battery118provides power to the processing circuitry116and other components of the mobile device104. The mobile device104may also have components for user interaction, such as a display120(e.g., liquid crystal display), a keypad122, a microphone124, and/or a speaker126.

Suppose the mobile device104is operating under normal conditions at the edge of a cell, as denoted inFIG. 1as a distance “X”. The signal quality may be limited by a number of factors, including thermal noise, the noise figure of the receiver, and the channel quality (fading). The limited signal quality may limit reliable data transfer, particularly for high rate data transfers, such as may be required for video transmission as well as for communication of internet content. The signal quality may improve by decreasing the distance between the mobile device and the base station by, for example one-half, as denoted by the distance “½X” inFIG. 1. However, as described above, it is generally desired to provide an optimal signal quality regardless of the location of the mobile device104within the network.

Therefore, according to one implementation, the antenna112includes a primary antenna and a diversity antenna with antenna components114supporting the two antennas. The primary antenna sends and receives signals, whereas the diversity antenna is dedicated to signal reception. The diversity antenna complements the primary antenna by preventing fading, where fading is defined by a reduction of signal quality and/or transmission rate. One particular implementation of the dual antenna system is described next, with reference toFIG. 2.

FIG. 2shows an exemplary dual-antenna structure200with a primary antenna202and a diversity antenna204. According to this implementation, the primary antenna202transmits and/or receives signals using primary antenna components206, which may include a transmitter, receiver, filters, and so forth. The diversity antenna204is dedicated to signal reception and complements the primary antenna202by preventing fading. The diversity antenna204includes a diversity antenna switch208to direct signals to power sensitive components, such as filters, active and passive devices, and so forth. For example, the antenna switch204may direct signals to different filter elements in a Surface Acoustic Wave (SAW) filter mechanism210based on the frequency of the signal. The outputs of the primary antenna components206and/or the SAW filter mechanism210are transmitted to further circuitry of a mobile device, such as processing circuitry116(FIG. 1). Such circuitry would be within the knowledge of one of skill in the art and is not shown for the sake of simplicity. Likewise, well-known components associated with the antennas, such as so-called “matching” components in the SAW filter mechanisms, are not shown or described in detail herein as their configuration is not critical to this discussion.

The signal power at the primary antenna202may not generally be realized by the diversity antenna204due to isolation between the antennas. The extent of this isolation depends on the design of structure200. The antennas202and204may be designed for minimal isolation in order to optimize diversity performance. For example, in normal operation, approximately 10 decibel (dB) of isolation attributable to isolation may be present between the two antennas.

The diversity switch208may be designed to take advantage of the isolation effect. For example, since the diversity antenna208is affected by isolation, certain components, such as the duplex filter and external low noise amplifier (LNA), are omitted from the front end of the switch208

To illustrate isolation by way of example, a typical transmission may be transmitted at about 25 dBm (Decibel referenced to milliwatts). Considering the 10 dB isolation described above, the diversity antenna204generally receives an input power of 15 dBm. Any given filter element in the SAW filter mechanism210typically has a maximum input power of 15 dBm. Thus, the actual power input into the SAW filter mechanism210is less than, or equal to, the maximum power that can be handled by any of the filter elements in the SAW filter mechanism210. According to these normal operating conditions, the SAW filter mechanism210is capable of handling the level of power received by diversity antenna204without being damaged.

Under abnormal conditions, however, the isolation between the primary antenna202and diversity antenna204may be dramatically reduced which increases the power of the signal sent to the SAW filter mechanism210. In fact, under these abnormal conditions, the filter elements in the SAW filter mechanism210may be exposed to power levels close, or equal, to the fully transmitted power. Continuing with the example from above, the filter elements in the SAW filter mechanism210may be exposed to, for example, 25 dBm rather than the 15 dBm for which the filters in SAW filter mechanism210are designed. This excessive signal power might potentially damage or even destroy the SAW filter mechanism210.

The high power experienced at the filter elements under abnormal conditions may be addressed in several ways. According to one implementation, the filters are designed to be sufficiently robust to handle the power without degradation over time. According to another implementation, a detector212is inserted between the diversity antenna204and the SAW filter mechanism210. The detector212may have an input terminal214to receive an incoming signal from the antenna and an output terminal216connected to control logic218. The detector212may be operable to determine whether the input signal has a power that exceeds a threshold value. The threshold value may be based, for example, upon the power handling capabilities of the filter elements in the SAW filter mechanism210. If the signal power exceeds the threshold value, the detector212informs the control logic218, which prevents the signal from reaching the SAW filter mechanism210.

More particularly, the control logic218directs a switch220to send the signal received by antenna204to one of several electrical portals222. Each portal222connects to a different SAW filter element in the SAW filter mechanism210or to a termination point224, which may be a load, open, ground, or “off” mode connection. For example, six portals222are shown inFIG. 2and are configured to handle five frequency bands and the termination point224. The control logic218may be controlled by three-bit control signals generated by a signal generator226associated with a processing unit228as is well known in the art. Control logic218includes hardware, software, or a combination thereof. The three-bit control signal may include three individual digital signals. Each incoming digital signal is either high (1) or low (0), enabling multiple three-bit signal combinations including, for example: [000], [001], [011], [111], [110], [100], [010], and [101]. Each digital signal combination may direct the switching mechanism220to a different portal222in the diversity antenna switch208. Thus, for example, a three bit signal of [000] may direct the switching mechanism220such that the signal from the antenna204travels to the termination point224. A control signal corresponding to [001] may direct the switching mechanism220such that the signal is directed from the antenna204to Band I, which may correspond to a filter for handling a ˜2100 MHz frequency signal, and so forth. Of course, the switching mechanism may be directed to any number of paths by increasing the number of bits processed by the control logic218and increasing the number of portals222.

If the input signal power exceeds the threshold value, e.g., the maximum power of the filters in the SAW filter mechanism210, the detector212or the control logic218directs the switching mechanism220to a termination point224. The termination point224may be a ground, load, open circuit, or “off” mode connection. According to one implementation, the detector212may be a diode that operates either as a short or as an open circuit depending on whether the incoming signal exceeds the threshold power value. Thus, when the signal received by the detector212exceeds the threshold value, the detector sends a signal to the control logic218to direct the switch220to the termination point224. When the signal received by the detector212is below the threshold value, the detector may send no signal to the control logic218, thereby acting as an open circuit. Additionally or alternatively, the diode may connect directly to the termination point (i.e. not through the control logic) such that the detector operates as an open circuit under normal conditions and as a short to the termination point under abnormal conditions.

The termination point224, may be an “off” mode connection that sends an “off” signal back to the processing unit228. The processing unit228may render the mobile device, or a portion of the device, inoperable for a predetermined period. The predetermined period may be based upon a preselected passage of time (e.g., 30 seconds), the cessation of the abnormal condition, or the reactivation of the device by a user. Reactivation may involve pressing a power button on the device, resetting the battery, or other action by the user. The “off” mode connection may be in addition to, or as an alternative to, a load or ground termination.

Operation

FIG. 3shows an exemplary process300of detecting power incoming to a diversity antenna and, in response, preventing the power from reaching filters. This process300may be implemented with the antenna structure shown inFIG. 2, though the process is not limited to such an implementation. The process is illustrated as a collection of referenced acts arranged in a logical flow graph, which represent a sequence that can be implemented in hardware, software, or a combination thereof. In the context of software, the acts represent computer-executable instructions that, when executed, perform the recited operations. The order in which the acts are described is not intended to be construed as a limitation, and any number of the described acts can be combined in any order and/or in parallel to implement the process300.

At302, an incoming signal is received. More particularly, the signal may be received by an antenna, such as a primary antenna and/or a diversity antenna. The received signal is sent to a switch. The switch may be designed to direct the signal incoming from the antenna (e.g. the diversity antenna) to one or more ports connected to SAW filters, where each port corresponds to a different signal frequency.

At304, the signal is detected to evaluate, measure, and/or determine its characteristics. In one implementation, a detector212may be inserted in, or associated with, the antenna switch to assist in this evaluation. The detector212may include a diode to determine the signal's power.

At306, whether the power of the incoming signal exceeds a predetermined threshold value is determined. If the power does not exceed the predetermined threshold value, the signal is directed toward the SAW filters at308. However, if the power exceeds the predetermined threshold value, the signal is prevented from reaching the SAW filters at310. The signal is prevented from reaching the SAW filters by, for example, sending the signal to a termination point, such as a load, ground, open, or “off” mode connection. The process may be automatic, such that the detector acts as fuse to automatically direct the signal to the termination point if the detected power exceeds the threshold value. According to this exemplary method, SAW filters associated with the antenna switch are protected from damage or destruction.

Conclusion

Although the subject matter has been described in language specific to structural features and/or methodological steps, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as preferred forms of implementing the claims.