Patent Application
20100266068
This invention relates to communication systems for receiving and transmitting data and, more particularly, to receiving data service information on sub-carriers within an FM broadcast channel.
For many electronic devices, such as cellular phones and portable devices, it is often desirable to have data communications. For example, many portable devices receive data services over FM broadcast channels. RDS/RBDS (radio data system/radio broadcast data system) is one such service that uses a 57 kHz sub-carrier within an FM broadcast channel to provide data such as traffic information. Microsoft DirectBand is another such service that uses a 67.75 kHz sub-carrier within an FM broadcast channel to provide data such as traffic, weather, gas prices and other information. In addition to this 67.75 kHz sub-carrier, DirectBand radio uses QPSK (Quadrature Phase Shift Keying) modulation and a data rate of 12 kbps. It is also noted that DirectBand is based upon Microsoft's earlier Smart Personal Objects Technology (SPOT), which has been utilized, for example, in smart watches.
RDS/RBDS and DirectBand are examples of information that is sent out on FM channels using modulated SCA (Subsidiary Communications Authorization) sub-carriers. These modulated sub-carriers are included in the FM channel broadcast transmission, and they can be received and demodulated using appropriate circuitry configured for reception of the particular SCA sub-carriers. U.S. Pat. No. 7,272,375, which is hereby incorporated by reference in its entirety, provides an example of low-IF FM receiver architectures that can receive and process RDS/RBDS data.
Prior DirectBand receivers in portable devices utilized a chipset including an application chip and a DirectBand custom radio receiver chip. The application chip operates as a CPU (central processing unit) and is based upon an ARM processor. The DirectBand radio receiver chip was made specifically for the DirectBand and is how the MSN DirectBand service connects to the watch.
The DirectBand receiver solution is relatively expensive, large, complex to manufacture and relatively non-integrated with many external components. As such, there is a need for a more efficient data receiver solution for DirectBand.
Low-IF terrestrial data receivers and related communication systems and methods are disclosed that provide efficient solutions for reception of data services in FM broadcast channels. In particular, systems and methods are provided for data service information modulated on a 67.65 kHz sub-carrier, for example, using QPSK modulation. Intermediate data service information is output by the data receiver, and this intermediate data service information takes the form of demodulated digital I/Q signals provided through a digital interface of the data receiver. As such, partial digital signal processing is provided by the data receiver and the remaining digital processing is provided by a host processor.
It is noted that the appended drawings illustrate only exemplary embodiments of the invention and are, therefore, not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
Low-IF terrestrial data receivers and related communication systems and methods are disclosed that provide efficient solutions for reception of data services in FM broadcast channels.
The low-IF terrestrial receivers and related systems and methods described here are designed to receive FM radio broadcast channel, perform FM demodulation and stereo decoding of the FM multiplex (MPX) signal to provide audio outputs, and perform decoding of Subsidiary Communications Authorization (SCA) sub-carriers multiplexed with the main stereo channel to provide ancillary music/data services. An example of these data services are RDS/RBDS and DIRECTBAND. More particularly, the solutions described herein provide a more efficient solution for receiving DirectBand data services.
With respect to the digital processing of the DirectBand data signals provided by the DSP 304 within the low-IF FM data receiver 302, it is noted that in one embodiment, the DSP 304 can perform FM demodulation and demodulation of the DirectBand QPSK modulated sub-carrier. For this embodiment, the FM data receiver 302 then outputs digital, demodulated I and Q (i.e., in-phase and out-of-phase) digital data signals through the digital output interface to the host processor 208. The host processor 208 then processes this intermediate digital I/Q data to obtain fully processed DirectBand data.
Examples of digital serial interfaces that could be used include the following: I2S interface (Inter-IC Sound Interface) and similar bit-stream formats, as well as time division multiplexing (TDM) streams. Other digital serial interfaces could also be used. If desired, the digital serial interface can also be programmed to support one or more of the following options on the basic serial protocol: (1) master or slave mode, (2) programmable clock and word select polarity (rising or falling edge), (3) slot length (number of bits per time slot), (4) word length (bits per word): always less than or equal to the time slot length, (4) first-bit data delay with respect to the word select, (5) left/right alignment of word inside slot, (6) bit order: most-significant-bit first or least-significant-bit first, and/or (7) bit mask/pad/rotate function. It is further noted that in master mode the integrated FM data receiver is configured to generate the bit clock and word select lines with the serial data lines to the host processor. In slave mode, the integrated FM data receiver is configured to accept external bit clock and word select lines in generating the serial data line outputs.
Advantageously, the low-IF data receiver solutions described herein partition the DirectBand processing between the FM data receiver 302 and the host processor 208 thereby eliminating the need for the additional ARM processor and integrated circuit in
It is further noted that the digital processing provided in the integrated FM data receiver 302 can include digital filter, tuning and demodulation of the data service information in the received FM broadcast channel. In such an embodiment, the integrated FM data receiver 302 outputs digital demodulated data service information through a digital interface for the integrated FM data receiver 302. The host processor 208 can then provide further digital processing in the form of digital decoding of the digital demodulated data service information to produce fully processed (e.g., demodulated and decoded) data service information. It is noted, therefore, that the data service information can be coded using a desired coding scheme, and the DSP 308 within the host processor 208 can be configured to provide appropriate decoding of this coded information. The fully processed output data 210 can then represent demodulated and decoded data service information. It is again noted that the DSP 308 can be implemented using a wide variety of circuitry, including programmed microcontrollers, digital cores and/or other processors or circuitry, as desired.
An example of low-IF FM receiver architectures that could be utilized for the low-IF FM data receivers are described in U.S. Pat. No. 7,272,375, which is hereby incorporated by reference in its entirety. For example, receive path circuitry within an integrated FM receiver can receive an RF signal spectrum representing an FM broadcast channel including data service information on a sub-carrier and can output digital signals representing the data service information. A DSP within the integrated FM receiver can then process the data service information to produce intermediate data service information. This intermediate data service information can then be output through a digital interface to an external device such as a host processor. The DSP can be implemented utilizing a wide variety of circuitry, including a microcontroller programmed to implement the desired partial processing.
Further modifications and alternative embodiments of this invention will be apparent to those skilled in the art in view of this description. It will be recognized, therefore, that the present invention is not limited by these example arrangements. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the manner of carrying out the invention. It is to be understood that the forms of the invention herein shown and described are to be taken as the presently preferred embodiments. Various changes may be made in the implementations and architectures. For example, equivalent elements may be substituted for those illustrated and described herein, and certain features of the invention may be utilized independently of the use of other features, all as would be apparent to one skilled in the art after having the benefit of this description of the invention.
