Patent Publication Number: US-2016226544-A1

Title: Adaptive wireless baseband interface

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of the priority date of U.S. Provisional Patent Application Ser. No. 62/112,023, titled, Adaptive Wireless Baseband Interface, filed Feb. 4, 2015. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to a wireless communications device having RF and signal processing elements, and including an adaptive interface for digital signal transfer between a digital front end module (FEM) and a baseband processor and, more particularly, to a wireless communications device having RF and signal processing elements, and including an adaptive interface for digital signal transfer between a digital FEM and a baseband processor, where the interface by-passes a currently existing analog-to-digital converter (ADC) and a digital-to-analog converter (DAC) in the processor or provides signal flow between the digital FEM and a high speed I/O port on the baseband processor. 
     2. Discussion of the Related Art 
     A conventional wireless communications device, such as a cellular telephone, generally will include an analog front end module (FEM) in which analog RF signal processing is performed for both signals received by the device and signals transmitted by the device. Thus, the analog FEM will include processing elements for analog signals received by the device, such as a low noise amplifier (LNA), band-pass filters, RF down-conversion circuits, etc. Likewise, the analog FEM will include processing elements for analog signals transmitted by the device, such as RF up-conversion circuits, band-pass filters, high power amplifiers (HPA), etc. 
     A conventional wireless communications device will generally also include a baseband processor that receives the analog receive signals from the analog FEM and that sends the analog transmit signals to the analog FEM. The baseband processor includes an analog-to-digital converter (ADC) and a digital-to-analog converter (DAC) to perform the conversion from analog to digital for the receive signals and the conversion from digital to analog for the transmit signals. The baseband processor will also include the necessary digital circuit elements for message recovery and de-modulation of the receive signal, and signal processing for various signals such as audio or video messages. 
     A conventional wireless communications device will generally also include an application processor that is the interface between the user of the device and the baseband processor. For example, the application processor may include software and circuits for converting inputs, such as text and audio signals, from the user to a suitable digital signal to be processed by the baseband processor, and will receive the digital messages recovered by the baseband processor, and convert the messages to the appropriate format to be understood by the user. 
     Digital software-defined radio architectures exist in the art, such as in certain military radios having multi-band waveforms. The current trend is to provide such digital software-defined radio architectures for automotive applications, which necessarily would need to be much lower cost than military radios. Such wireless communications devices that are configured to operate in the digital domain typically would include a digital FEM that provides flexibility and software definable processing, and a baseband processor that operates exclusively in the digital domain and be able to receive digital signals from the FEM and send digital signals to the FEM for transmission purposes. In these designs, the analog-to-digital conversion for the receive signals and the digital-to-analog conversion for the transmit signals is performed in the digital FEM. 
     SUMMARY OF THE INVENTION 
     The present disclosure describes a wireless communications device that includes a digital FEM that provides digital receive signals to a baseband processor and receives digital transmit signals from the baseband processor. The baseband processor can be an existing baseband processor for mobile wireless devices that employ an analog FEM that includes an ADC for converting analog receive signals to digital signals for baseband processing and a DAC for converting digital transmit signals to analog signals. In a first embodiment, the ADC and the DAC in the existing baseband processor operate as a signal pass-through, where digital transmit signals from the baseband processor pass directly through the DAC to the digital FEM and digital receive signals from the digital FEM pass directly through the ADC to other digital components within the baseband processor. In a second embodiment, the digital receive signals from the digital FEM by-pass the ADC in the baseband processor and the digital transmit signals from the baseband processor to the digital FEM bypass the DAC. In a third embodiment, digital receive signals from the digital FEM are provided to an existing digital I/O port in the baseband processor and digital transmit signals from the baseband processor are provided from a digital I/O port to the digital FEM. 
     Additional features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is schematic block diagram of a wireless communications device including a conventional baseband processor and a digital FEM; and 
         FIG. 2  is a schematic block diagram of a wireless communications device including a baseband processor, where an ADC and a DAC have been removed. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The following discussion of the embodiments of the invention directed to a wireless communications device including a digital FEM and a conventional baseband processor is merely exemplary in nature, and is in no way intended to limit the invention or its applications or uses. For example, the discussion herein has particular application for a wireless mobile communications device on a vehicle. However, as will be appreciated by those skilled in the art, the wireless mobile communications device of the invention well have other applications. 
     As will be discussed in detail below, the present invention proposes a wireless communications device including a digital FEM and a conventional baseband processor having a known configuration typically being employed in a wireless communications device having an analog FEM of the type discussed above. As will be discussed, operation of the baseband processor will be re-configured so that digital receive signals from the digital FEM are able to be processed by the baseband processor and digital transmit signals provided by the baseband processor are sent to the digital FEM, thus eliminating the need for significant redesign of the conventional baseband processor for the digital FEM. The wireless communications device can be any such device, such as a cellular device, cognitive radio, TV whitespace devices, etc. 
       FIG. 1  is a schematic block diagram of a wireless communications device  10  that is able to process both transmit signals and receive signals, such as cellular signals. The device  10  can be any device, such as a hand-held mobile unit or a wireless device, such as a radio, on a vehicle  44 . The device  10  includes a digital FEM  12  that provides digital signal processing for the transmit and receive signals, where analog receive signals are received by an antenna  14  and analog transmit signals are transmitted by the antenna  14 . The digital FEM  12  includes any suitable and all necessary analog and digital front end processing circuitry for a wireless device, such as band-pass filters, circulators for isolating the receive and transmit signals, down-converters, up-converters, switches, modulators, DACs, ADCs, low noise amplifiers, power amplifiers, etc. 
     The device  10  also includes a baseband processor  16  of the type discussed above that provides data recovery, power conditioning, signal modulation, signal de-modulation, etc. The communications device  10  also includes an application processor  18  that receives the receive signals from the baseband processor  16  and provides signals to be transmitted to the baseband processor  16 , where the application processor  18  provides a control interface between the baseband processor  16  and the user, as also discussed above. 
     The baseband processor  16  is of a conventional type, and includes a central processing unit (CPU)  20  that performs basic digital functions in the processor  16 , such as clocking functions, message scheduling functions, etc. The baseband processor  16  also includes a modulator  26  that provides digital signal modulation for the transmit signal, and a de-modulator  28  for de-modulating the receive signal to remove information and message bits therefrom. The baseband processor  16  also includes a memory  30  for storing the digital bits to be transmitted or received, and a power management circuit  32  for providing power management and conditioning. The baseband processor  16  also includes a host computer  22  that runs the various application levels in the processor  16  and provides signal transformation for an interface to the application processor  18 . Further, the baseband processor  16  includes an interface  24  intended to represent the many input/output (I/O) ports coupled to the baseband processor  16 , such as USB ports, that allow other electronic devices (not shown) to be coupled thereto to provide, for example, software updating, software down-loading, testing, etc. 
     Further, since the baseband processor  16  is of a conventional type that would normally be used with an analog FEM (not shown) as discussed above, the baseband processor  16  includes an ADC  34  that converts analog receive signals from the analog FEM to digital signals to be processed by the digital components of the baseband processor  16 , and a DAC  36  that converts digital signals processed by the baseband processor  16  to analog signals to be sent to the analog FEM for transmission in the known devices. In the embodiments discussed herein where the analog FEM has been replaced with the digital FEM  12 , and where the digital FEM  12  provides analog to digital conversion and digital to analog conversion, the already existing ADC  34  and DAC  36  in the processor  16  are not used. 
     In a first embodiment, the ADC  34  and the DAC  36  only operate as pass-through elements in the processor  16  and do not provide any digital and analog signal conversion. For example, the digital signals to be transmitted may have been sent from the modulator  26  to the DAC  36  in the device employing an analog FEM to convert the digital signals to analog signals for transmission. However, in this embodiment, the digital transmit signals are still provided to the DAC  36 , but the DAC  36  is re-configured so that it outputs the same digital signal that it receives. Thus, the modulated digital signals from the modulator  26  are sent directly to the digital FEM  12  where they are converted to an analog signal for transmission. Likewise, in the analog FEM design, the ADC  34  may have converted the analog signals from the analog FEM to digital signals that would then be provided to the de-modulator  28  to remove the bits. However, in this embodiment, the digital receive signals are provided to the ADC  34  directly from the FEM  12 , where the ADC  34  is reconfigured so that it outputs the same digital signal that it receives from the digital FEM  12 , where the analog signals received by the antenna  14  are converted to the digital signals in the FEM  12 . 
     In another embodiment, the baseband processor  16  can be re-configured so that the digital receive signals from the digital FEM  12  completely by-pass the ADC  34 , such as through a test port  46 , and be directly sent to the de-modulator  28 . Likewise, the baseband processor  16  can be re-configured so that the transmit signals from the modulator  26  completely by-pass the DAC  36  and be provided directly to the digital FEM  12 , such as through the test port  46 , as digital signals. 
       FIG. 2  is a schematic block diagram of a wireless communications device  40  that is similar to the wireless device  10 , where like elements are identified by the same reference number. In this embodiment, the baseband processor  16  has been replaced with a baseband processor  42 , where the ADC  34  and DAC  36  have been eliminated to specifically show that they are not used in the device  40 , although they still may be present in the baseband processor  42  if it is an already existing device that could be used in connection with an analog FEM. In this embodiment, the digital receive signals from the digital FEM  12  are provided to one or more of the interface I/O ports  24  in the baseband processor  42  and the digital transmit signals from the baseband processor  42  are provided to the digital FEM  12  from one of the interface I/O ports  24 . The I/O ports  24  would route the digital receive signals from the digital FEM  12  to the de-modulator  28  and the transmit signals from the modulator  26  would be sent to the interface I/O port  24  to be sent to the digital FEM  12 . 
     For certain communications devices there may be a need to provide additional signal conditioning and/or formatting between the digital FEM  12  and the baseband processor  16  or  42  depending on the capabilities and signal requirements of the FEM  12  and the baseband processor  16  or  42 . The additional signal conditioning can be accomplished by including one or more dedicated circuits between the FEM  12  and the baseband processor  16  or  42 , such as a digital signal processing (DSP) chip. For example, the circuit could provide digital signal formatting, such as converting digital signals from serial to parallel, formatting signals, converting digital formats, such as USB, SPI, etc., and/or scaling the signal to appropriate time and amplitude scales. For the embodiments discussed above, a dedicated circuit or chip  38  can be provided between the FEM  12  and the baseband processor  16  or  42  to perform one or more of these functions. 
     As will be well understood by those skilled in the art, the several and various steps and processes discussed herein to describe the invention may be referring to operations performed by a computer, a processor or other electronic calculating device that manipulate and/or transform data using electrical phenomenon. Those computers and electronic devices may employ various volatile and/or non-volatile memories including non-transitory computer-readable medium with an executable program stored thereon including various code or executable instructions able to be performed by the computer or processor, where the memory and/or computer-readable medium may include all forms and types of memory and other computer-readable media. 
     The foregoing discussion discloses and describes merely exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the spirit and scope of the invention as defined in the following claims.