Abstract:
A system includes a control board, a controlled board, and a connector connecting the control board to the controlled board. The control board includes a processing unit that configures the reference voltage signals, a non-volatile memory that stores information about the reference voltage signals, and a DAC that outputs the reference voltage signals in accordance with instructions from the processing unit. The controlled board includes: first and second voltage reference devices that receive first and second reference voltage signals, respectively, and a radio-frequency device that receives a first frequency signal and a second frequency signal and outputs a third frequency signal based on one of the first and second reference voltage signals. The connector includes an analog line for providing reference voltage signals to the first and second voltage reference devices and a digital line for providing control signals to activate one of the first and second voltage reference devices.

Description:
RELATED APPLICATION 
       [0001]    The present invention claims priority to U.S. Provisional Application No. 61/755,382, “A SYSTEM OF MULTIPLE VOLTAGE REFERENCES USING A SINGLE ANALOG LINE,” filed Jan. 22, 2013, which is hereby incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to wireless communication system and wireless communication radio frequency (RF) equipment, and in particular, relates to a system of providing multiple voltage references to a RF device using a single analog line. 
       BACKGROUND 
       [0003]    Modern RF devices, such as mixers, upconverters, downconverters, power amplifiers and the latest highly integrated multifunction ICs, often require operation mode tuning using multiple independent voltage references (VREF). In some circumstances, the reference voltages need to be re-adjusted at runtime for various operation environments such as temperature, frequency, power level, etc. Such devices are usually calibrated during product manufacturing, for example, individually calibrated for each manufactured unit, and the values of the reference voltages are stored inside the on-board electrically erasable programmable read-only memory (EEPROM). 
         [0004]    A most common approach to provide multiple reference voltages to the controlled device is illustrated in  FIG. 1 , where a digital-to-analog converter (DAC) with multiple channels is used. 
         [0005]    In a modular design approach, a CPU/MPU with a DAC are disposed on one board referred as the “control board”, while the controlled device, such as mixers, upconverters, etc., are disposed on a different board referred as the “controlled board”. The physical interface between the control board and the controlled board is predefined so that the same type of the control board can be connected to different predefined types of the controlled board.  FIG. 2  depicts a structure of a revised system to provide reference voltage to a mixer on a controlled board. 
         [0006]    However, a connector of the control board has a limited and fixed number of analog lines determined by the original design of the controlled board. Future revisions or new types of the controlled board may require more reference voltages than originally designed. Therefore, the interface of a current controlled board may not be able to provide enough analog lines to meet the new design requirements.  FIG. 3  depicts a compatibility problem of the revised system to provide reference voltage to a mixer on a controlled board. Note that the mixer needs two reference voltage signals but the control board can only provide one. 
       SUMMARY 
       [0007]    The present invention provides a cost effective method to provide two different reference voltages from the control device using a single analog line, a single digital line, and two erasable programmable read-only memory (EEPROM) disposed on the controlled board. 
         [0008]    In accordance with some embodiments, a system of providing multiple voltage references to a radio-frequency device using a single analog line includes a control board, a controlled board, and a connector connecting the control board to the controlled board. The control board includes: a processing unit that configures the reference voltage signals; a non-volatile memory that stores information about the reference voltage signals; and a digital-to-analog converter (DAC) that outputs the reference voltage signals in accordance with instructions from the processing unit. The controlled board includes: a first voltage reference device that receives a first reference voltage signal; a second voltage reference device that receives a second reference voltage signal; and a RF device that receives a first frequency signal and a second frequency signal, and outputs a third frequency signal based on one of the first and second reference voltage signals. The connector includes an analog line reference voltage signals to the first and second voltage reference devices and a digital line for providing control signals to the first and second voltage reference devices. 
         [0009]    In accordance with some embodiments, a method of providing multiple voltage references to a radio-frequency device using a single analog line includes the steps of setting the analog line voltage level to be a first reference voltage signal; instructing a first voltage reference device to memorize the first reference voltage signal by sending a first digital control signal to a digital line; providing the first reference voltage signal to the RF device via the first voltage reference device; re-setting the analog line voltage level to be a second reference voltage signal; instructing a second voltage reference device to memorize the second reference voltage signal by sending a second digital control signal to the digital line, wherein the second digital control signal is different from the first digital control signal; and providing the second reference voltage signal to the RF device via the second voltage reference device. The RF device is configured to receive a first frequency signal and a second frequency signal, and output a third frequency signal based on one of the first and second reference voltage signals. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    Different aspects of the present invention as well as features and advantages thereof will be more clearly understood hereinafter because of a detailed description of embodiments of the present invention when taken in conjunction with the accompanying drawings, which are not necessarily drawn to scale. Like reference numerals refer to corresponding parts throughout the several views of the drawings. 
           [0011]      FIG. 1  depicts a structure of a conventional system to provide N reference voltages to a mixer. 
           [0012]      FIG. 2  depicts a structure of a revised system to provide reference voltage to a mixer on a controlled board. 
           [0013]      FIG. 3  depicts a compatibility problem of the revised system to provide reference voltage to a mixer on a controlled board. 
           [0014]      FIG. 4  depicts a structure of a system of providing multiple voltage references to a mixer using a single analog line in accordance with some embodiments of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0015]    Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous non-limiting specific details are set forth in order to assist in understanding the subject matter presented herein. It will be apparent, however, to one of ordinary skill in the art that various alternatives may be used without departing from the scope of the present invention and the subject matter may be practiced without these specific details. For example, it will be apparent to one of ordinary skill in the art that the subject matter presented herein can be implemented on many types of outdoor radios systems. 
         [0016]      FIG. 1  depicts a structure of a conventional system to provide N reference voltages to a mixer. The system includes a CPU/MPU  101 , an EEPROM  102 , a DAC  103  with N multiple analog lines, and a mixer  104 . The CPU/MPU  101  configures the voltage for each of the DAC  103  outputs using data stored in the EEPROM  102 . Further, the DAC  103  is configured to provide the reference voltage, for example, V REF1  to the mixer  104  through one of the analog lines. The mixer  104  receives a first frequency signal F 1  and a second frequency signal F 2 , and generates a third frequency signal F 3  based on the reference voltage V REF1 . 
         [0017]      FIG. 2  depicts a structure of a revised system to provide a reference voltage to a mixer on a controlled board. The revised system includes a control board  201 , a controlled board  203 , and a connector  202  to connect the control board  201  to the controlled board  203 . A CPU/MPU  204 , an EEPROM  205 , and a DAC  206  are disposed on the control board  201 , and a mixer  207  is disposed on the controlled board  203 . The DAC  206  provides a reference voltage V REF1  to the mixer  207  via an analog line. The mixer  207  receives a first frequency signal F 1  and a second frequency signal F 2 , and generates a third frequency signal F 3  based on the reference voltage V REF1 . 
         [0018]      FIG. 3  depicts a compatibility problem of the revised system to provide reference voltage to a mixer on a controlled board. The connector  302  connecting the control board  301  and the controlled board  302  has a limited number of the analog lines determined by the original design of the controlled board  303 . As illustrated in  FIG. 3 , the control board  301  cannot provide a second reference voltage V REF2  to the mixer  307  due to the limited number of the analog lines at the physical interface of the controlled board  303 . 
         [0019]      FIG. 4  depicts a structure of a system of providing multiple voltage references to a mixer using a single analog line in accordance with some embodiments of the present invention. The system includes a control board  401 , a controlled board  403 , and a connector  402  that connects the control board  401  to the controlled board  403 . A CPU/MPU  404 , an EEPROM  405 , and a DAC  406  are disposed on the control board  401 , and a first voltage reference device (EPVR device #1)  407 , a second voltage reference device (EPVR device #2)  408 , and a mixer  409  are disposed on the controlled board  403 . As shown in  FIG. 4 , the DAC  406  provides reference voltages to the first voltage reference device  407  and the second voltage reference device  408  via a single analog line. The first voltage reference device  407  and the second voltage reference device  408  are configured to provide a first reference voltage signal V REF1  and a second reference voltage signal V REF2  to the mixer  409 , respectively. Note that there is an inverter  410  before the second voltage reference device  408 . The mixer  409  receives a first frequency signal F 1  and a second frequency signal F 2 , and generates a third frequency signal F 3  based on the first reference voltage signal V REF1  and the second reference voltage signal V REF2 . 
         [0020]    In some embodiments, the voltage reference device is an electronically programmable voltage reference device (EPVR). The EPVR is an integrated circuit (IC) that can read and memorize the level of the input analog signal, and provide a memorized level of signal on the analog output even when the voltage level of the input analog signal changes, or after the input analog signal is removed. 
         [0021]    In some embodiments, the analog line within the connector  402  and between the control board  401  and the controlled board  403  is only used during a short time period for the reference voltages configuration. The voltage level at the analog line is initially set to be the first reference voltage signal V REF1 . Once the voltage level at the analog line is initially set, the CPU/MPU  404  sends a first digital control signal to the first voltage reference device (EPVR device #1)  407  through the digital line within the connector  402  to memorize the initially set voltage level, and to provide the first reference voltage signal V REF1  to the mixer  409 . In some embodiments, after the first reference voltage signal V REF1  is configured, the voltage level at the analog line is changed to the second reference voltage signal V REF2 . By resetting the digital line to its original state, the CPU/MPU  404  sends a second digital control signal to the second voltage reference device (EPVR device #2)  408  through the digital line within the connector  402  to memorize the newly set voltage level, and to provide the second reference voltage signal V REF2  to the mixer  409 . In this example, the second digital control signal is different from (e.g., opposite to) the first digital control signal. After both the first reference voltage signal V VREF1  and the second reference voltage signal V REF2  are configured, the DAC  406  at the control board  401  can be shutdown to preserve power. The digital line will remain in its current state until the next reconfiguration of the reference voltage. 
         [0022]    In some embodiments, when at least two digital lines are available between the control board and the controlled board, one more DACs may be directly disposed on the controlled board, which will be programmable via an inter-integrated circuit (I 2 C) interface. 
         [0023]    The key advantages of this invention include:
       Multiple reference voltages configuration using a single analog line.   Reduced power consumption of the control board.   Ability to reconfigure reference voltage at any moment.   Easy reference voltage configuration process.       
 
         [0028]    While particular embodiments are described above, it will be understood it is not intended to limit the invention to these particular embodiments. On the contrary, the invention includes alternatives, modifications and equivalents that are within the spirit and scope of the appended claims. Numerous specific details are set forth in order to provide a thorough understanding of the subject matter presented herein. But it will be apparent to one of ordinary skill in the art that the subject matter may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the embodiments. 
         [0029]    The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the description of the invention and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms “includes,” “including,” “comprises,” and/or “comprising,” when used in this specification, specify the presence of stated features, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, operations, elements, components, and/or groups thereof. 
         [0030]    As used herein, the term “if” may be construed to mean “when” or “upon” or “in response to determining” or “in accordance with a determination” or “in response to detecting,” that a stated condition precedent is true, depending on the context. Similarly, the phrase “if it is determined [that a stated condition precedent is true]” or “if [a stated condition precedent is true]” or “when [a stated condition precedent is true]” may be construed to mean “upon determining” or “in response to determining” or “in accordance with a determination” or “upon detecting” or “in response to detecting” that the stated condition precedent is true, depending on the context. 
         [0031]    Although some of the various drawings illustrate a number of logical stages in a particular order, stages that are not order dependent may be reordered and other stages may be combined or broken out. While some reordering or other groupings are specifically mentioned, others will be obvious to those of ordinary skill in the art and so do not present an exhaustive list of alternatives. Moreover, it should be recognized that the stages could be implemented in hardware, firmware, software or any combination thereof. 
         [0032]    The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.