Abstract:
An RF electronics module includes a grounding plate, a non-conductive substrate, a number of conductive vias, RF PA circuitry, and RF power detection circuitry. The non-conductive substrate is over the grounding plate. The conductive vias extend parallel to one another from a surface of the non-conductive substrate opposite the grounding plate through the non-conductive substrate to the grounding plate. The RF PA circuitry is coupled to the grounding plate through a first one of the conductive vias. The RF power detection circuitry is coupled to a second one of the conductive vias and configured to measure a signal induced in the second one of the conductive vias due to electromagnetic coupling with the first one of conductive vias. The first one of the conductive vias is adjacent to the second one of the conductive vias.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional patent application serial No. 61/929,108, filed Jan. 19, 2014, the disclosure of which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    The present disclosure relates to radio frequency (RF) electronics modules, and in particular to power detection circuitry configured to measure an output power of RF power amplifier (PA) circuitry in an RF electronics module through electromagnetic coupling between adjacent conductive vias in the RF electronics module. 
       BACKGROUND 
       [0003]    As radio frequency (RF) communications technology continues to evolve, the demands placed on RF power amplifier (PA) circuitry used to transmit RF signals proportionally increase. Strict requirements for noise, spectral masking, and transmit power mandated by modern RF communications standards combined with efficiency and reliability concerns generally demanded for consumer electronics require exceptionally high performance RF PA circuitry. One way to increase the performance of RF PA circuitry is by using a feedback loop of some kind. To implement a feedback loop for RF PA circuitry, a measurement of an RF output signal produced at an output of the RF PA circuitry must first be obtained. Generally, direct measurements of an RF output signal result in a reduction in the magnitude of the RF output signal and further may introduce noise and/or distortion into the RF output signal. Accordingly, RF power couplers are generally used to extract a portion of the RF output signal, which may then be used in a feedback loop to increase the performance of the RF PA circuitry. 
         [0004]      FIG. 1  shows RF PA circuitry  10  including a conventional RF power coupler  12 . The RF PA circuitry  10  includes an RF input node  14 , an RF output node  16 , and an RF PA  18  coupled between the RF input node  14  and the RF output node  16 . Generally, the RF PA  18  includes one or more connections to ground as shown in  FIG. 1 . The conventional RF power coupler  12  includes a coupled port  20 , an isolated port  22 , and a coupling line  24 . The isolated port  22  of the conventional RF power coupler  12  is coupled to ground via an isolation resistor R IS . The coupling line  24  is arranged so that it runs parallel to an output line  26  of the RF PA circuitry  10 . Electromagnetic coupling between the coupling line  24  and the output line  26  induce a signal at the coupled port  20  of the conventional RF power coupler  12  that is proportional to an RF output signal RF_OUT on the output line  26 . The electromagnetic coupling generally has a minimal effect on the RF output signal RF_OUT, thereby allowing for an accurate measurement of the RF output signal RF_OUT without significant interference therewith. 
         [0005]    Generally, the length l CL  of the coupling line  24  is a quarter wavelength (λ/4) of a frequency of interest to be measured by the conventional RF power coupler  12 . Providing the coupling line  24  with a length l CL  that is a quarter wavelength of a frequency of interest generally results in satisfactory electromagnetic coupling between the coupling line  24  and the output line  26 , while failing to significantly interfere with the RF output signal. Further, the coupling line  24  with a length l CL  that is a quarter wavelength of a frequency of interest also results in a 90° phase shift in the RF output signal. 
         [0006]      FIG. 2  shows a top view of a printed circuit board (PCB)  28  including the RF PA circuitry  10  and the conventional RF power coupler  12 . As shown in  FIG. 2 , the RF input node  14  is located at a termination of a first conductive trace  30  on top of the PCB  28 , while the RF output node  16  is located at a termination of a second conductive trace  32  on top of the PCB  28 . The second conductive trace  32  correlates to the output line  26  discussed above with respect to  FIG. 1 . The RF PA  18  is a wirebond component including a first wirebond  34  connected to the first conductive trace  30  and a second wirebond  36  connected to the second conductive trace  32 . While a wirebond component is shown for exemplary purposes, flip chip components or components utilizing any other packaging technology may also be used along with the PCB  28 . The RF PA  18  may be mounted to the PCB  28  via a die flag  38 , which may connect the RF PA  18  to a grounding plate (not shown) on a bottom side of the PCB  28 . The conventional RF power coupler  12  is implemented with a third conductive trace  40 . The third conductive trace  40  includes a portion that runs parallel to the second conductive trace  32  and correlates with the coupling line  24  discussed above with respect to  FIG. 1 . Notably, the portion of the third conductive trace  40  that runs parallel to the second conductive trace  32  has a length l CL  that is about a quarter wavelength of a frequency of interest to be measured by the conventional RF power coupler  12 , as discussed above. The coupled port  20  is located at a first end of the third conductive trace  40 , while the isolated port  22  is located at an opposite end of the third conductive trace  40 , and may connect to ground through a via into the PCB  28  to a ground plate (not shown) located on an opposite surface of the PCB  28 . 
         [0007]    While the conventional RF power coupler  12  is capable of indirectly measuring an RF output signal RF_OUT without significantly interfering therewith, the quarter wavelength coupling line  24  often results in the conventional RF power coupler  12  consuming a relative large area in the RF PA circuitry  10 . Further, implementing the conventional RF power coupler  12  requires providing additional components in the conventional RF power coupler  12 , thereby increasing the cost of the RF PA circuitry  10 . Accordingly, there is a need for a compact RF power coupler that is easy to implement at a low cost. 
       SUMMARY 
       [0008]    The present disclosure relates to radio frequency (RF) electronics modules, and in particular to power detection circuitry configured to measure an output power of RF power amplifier (PA) circuitry in an RF electronics module through electromagnetic coupling between adjacent conductive vias in the RF electronics module. In one embodiment, an RF electronics module includes a grounding plate, a non-conductive substrate, a number of conductive vias, RF PA circuitry, and RF power detection circuitry. The non-conductive substrate is over the grounding plate. The conductive vias extend parallel to one another from a surface of the non-conductive substrate opposite the grounding plate through the non-conductive substrate to the grounding plate. The RF PA circuitry is coupled to the grounding plate through a first one of the conductive vias. The RF power detection circuitry is coupled to a second one of the conductive vias and configured to measure a signal induced in the second one of the conductive vias due to electromagnetic coupling with the first one of conductive vias. The first one of the conductive vias is adjacent to the second one of the conductive vias. By measuring the signal induced in the second one of the conductive vias due to electromagnetic coupling with the first one of the conductive vias, the RF power detection circuitry is capable of indirectly measuring an output power of the RF PA circuitry while utilizing minimal area in the RF electronics module. 
         [0009]    In one embodiment, a method includes providing an RF electronics module including a grounding plate, a non-conductive substrate, a number of conductive vias, and RF PA circuitry. The non-conductive substrate is over the grounding plate. The conductive vias extend parallel to one another from a surface of the non-conductive substrate opposite the grounding plate through the non-conductive substrate to the grounding plate. The RF PA circuitry is coupled to the grounding plate through a first one of the conductive vias. The method further includes measuring a signal induced in a second one of the conductive vias adjacent to the first one of the conductive vias to determine an output power of the RF PA circuitry. By measuring the signal induced in the second one of the conductive vias due to electromagnetic coupling with the first one of the conductive vias, the RF power detection circuitry is capable of indirectly measuring an output power of the RF PA circuitry while utilizing minimal area in the RF electronics module. 
         [0010]    Those skilled in the art will appreciate the scope of the disclosure and realize additional aspects thereof after reading the following detailed description in association with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The accompanying drawings incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure. 
           [0012]      FIG. 1  shows radio frequency (RF) power amplifier (PA) circuitry including a conventional RF power coupler. 
           [0013]      FIG. 2  shows details of the RF PA circuitry and the conventional RF power coupler shown in  FIG. 1 . 
           [0014]      FIG. 3  shows RF PA circuitry including an RF power coupler according to one embodiment of the present disclosure. 
           [0015]      FIG. 4  shows details of the RF PA circuitry and the RF power coupler shown in  FIG. 3  according to one embodiment of the present disclosure. 
           [0016]      FIG. 5  is a graph illustrating a relationship between an RF output signal and a coupled RF signal according to one embodiment of the present disclosure. 
           [0017]      FIG. 6  shows the RF PA circuitry and the RF power coupler shown in  FIG. 3  further including RF power detection circuitry according to one embodiment of the present disclosure. 
           [0018]      FIG. 7  shows details of the RF power detection circuitry shown in  FIG. 6  according to on embodiment of the present disclosure. 
           [0019]      FIG. 8  shows the RF PA circuitry and the RF power coupler shown in  FIG. 3  integrated into a feedback loop according to one embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    The embodiments set forth below represent the necessary information to enable those skilled in the art to practice the disclosure and illustrate the best mode of practicing the disclosure. Upon reading the following description in light of the accompanying drawings, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims. 
         [0021]    It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present disclosure. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
         [0022]    Relative terms such as “below” or “above” or “upper” or “lower” or “horizontal” or “vertical” may be used herein to describe a relationship of one element, layer, or region to another element, layer, or region as illustrated in the Figures. It will be understood that these terms and those discussed above are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures. 
         [0023]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including” when used herein specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
         [0024]    Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
         [0025]      FIG. 3  shows RF PA circuitry  42  including an RF power coupler  44  according to one embodiment of the present disclosure. The RF PA circuitry  42  includes an RF input node  46 , an RF output node  48 , an RF PA  50 , and a first conductive via  52  coupling the RF PA  50  to ground. The RF power coupler  44  includes a second conductive via  54 , which is adjacent to the first conductive via  52  coupling the RF PA  50  to ground, a coupled port  56 , and an isolated port  58 . The isolated port  58  of the RF power coupler  44  is directly connected to ground. The second conductive via  54  is in close enough proximity to the first conductive via  52  such that the two conductive vias are electromagnetically coupled. Accordingly, at least a portion of RF signals passing through the first conductive via  52  coupling the RF PA  50  to ground are transferred to the second conductive via  54  in the RF power coupler  44  as a coupled RF signal RF_C. 
         [0026]    In operation, an RF input signal RF_IN is provided at the RF input node  46  and delivered to the RF PA  50 . The RF PA  50  amplifies the RF input signal RF_IN to a level appropriate for transmission, for example, from an antenna (not shown), and provides the amplified signal as an RF output signal RF_OUT at the RF output node  48 . Since the RF PA  50  is grounded through the first conductive via  52 , a grounding signal RF_G proportional to the RF output signal RF_OUT is passed through the first conductive via  52 . As discussed above, a portion of the grounding signal RF_G is electromagnetically coupled to the second conductive via  54  in the RF power coupler  44  and provided as a coupled RF signal RF_C. Notably, the coupled RF signal RF_C is proportional to the RF output signal RF_OUT and therefore may be used to measure one or more aspects thereof. 
         [0027]    Using the second conductive via  54  in the RF power coupler  44  to indirectly measure one or more aspects of the RF output signal RF_OUT allows the RF power coupler  44  to remain extremely compact. In one embodiment, the second conductive via  54  in the RF power coupler  44  may be about ten times smaller than a quarter wavelength of the frequency of interest to be measured by the RF power coupler  44 . In an additional embodiment, the second conductive via  54  may be about twenty times smaller than a quarter wavelength of the frequency of interest to be measured by the RF power coupler  44 . In yet another embodiment, the second conductive via  54  may be about twenty five times smaller than a quarter wavelength of the frequency of interest to be measured by the RF power coupler  44 . In general, the area required by the RF power coupler  44  is significantly smaller than that of a conventional RF power coupler, generally requiring up to 25 times less area to implement than conventional solutions. 
         [0028]      FIG. 4  shows a cross-section of a physical implementation of the RF PA circuitry  42  according to one embodiment of the present disclosure. The RF PA circuitry  42  is implemented on a first surface  60  of a printed circuit board (PCB)  62 . The RF input node  46  is located at a termination of a first conductive trace  64  on the PCB  62 . The RF output node  48  is located at a termination of a second conductive trace  66  on the PCB  62 . The RF PA  50  is implemented as a wire bond component coupled to the PCB  62  via a conductive die flag  68 , however, any suitable packaging technology may be used without departing from the principles of the present disclosure. Wire bonds  70  connect the RF PA  50  to the first conductive trace  64  and the second conductive trace  66 . The coupled port  56  of the RF power coupler  44  is shown as a third conductive trace  72  on the first surface  60  of the PCB  62 . The first conductive via  52  connects the conductive die flag  68  to a grounding plate  74  opposite the first surface  60  of the PCB  62 . Additional conductive vias may also connect the conductive die flag  68  to the grounding plate  74 , but are not labeled. The second conductive via  54  connects the third conductive trace  72  to the grounding plate  74 . Notably, the second conductive via  54  is adjacent to the first conductive via  52  such that the first conductive via  52  and the second conductive via  54  are electromagnetically coupled. Accordingly, the coupled RF signal RF_C is obtained as discussed above with respect to  FIG. 3 . 
         [0029]    In one embodiment, a distance D CV  between the first conductive via  52  and the second conductive via  54  is less than about 280 um. In an additional embodiment, the distance D CV  between the first conductive via  52  and the second conductive via  54  is less than about 130 um. In general, the minimum distance D CV  between the first conductive via  52  and the second conductive via  54  will be limited by the fabrication process used for the PCB  62 . 
         [0030]      FIG. 5  is a graph illustrating the relationship of various frequency components of the RF output signal RF_OUT to the coupled RF signal RF_C. As shown in  FIG. 5 , at the fundamental frequency f o  of the RF output signal RF_OUT, the coupled RF signal RF_C has a linear relationship with the square root of the RF output signal RF_OUT. At the second harmonic 2f 0  of the RF output signal RF_OUT, the coupled RF signal RF_C also has a relatively linear relationship with the square root of the RF output signal RF_OUT. As the order of the harmonic increases, the relationship of the coupled RF signal RF_C to the square root of the RF output signal RF_OUT becomes more exponential and less linear, as shown in  FIG. 5 . In general, there is a defined relationship between the RF output signal RF_OUT and the coupled RF signal RF_C at various frequency components thereof, thereby allowing one to use the coupled RF signal RF_C to indirectly measure and approximate the RF output signal RF_OUT. 
         [0031]      FIG. 6  shows the RF PA circuitry  42  according to an additional embodiment of the present disclosure. The RF PA circuitry  42  shown in  FIG. 6  is substantially similar to that shown in  FIG. 3 , but further includes RF power detection circuitry  76  connected to the RF power coupler  44 . The RF power detection circuitry  76  is configured to receive and condition the coupled RF signal RF_C to provide an RF detection voltage signal RF_DET. In one embodiment, the RF power detection circuitry  76  filters the coupled RF signal RF_C to isolate one or more frequency components thereof. In an additional embodiment, the RF power detection circuitry  76  amplifies the coupled RF signal RF_C. In general, the RF power detection circuitry  76  conditions the coupled RF signal RF_C in one or more ways to provide the RF detection voltage signal RF_DET. 
         [0032]      FIG. 7  shows details of the RF power detection circuitry  76  according to one embodiment of the present disclosure. The RF power detection circuitry  76  includes filtration and amplification circuitry  78  and envelope detection circuitry  80 . The filtration and amplification circuitry  78  includes filtering circuitry  82  and an operational amplifier  84 . The filtering circuitry  82  includes a first resistor R 1  connected between the coupled port  56  of the RF power coupler  44  and a first filtering node  86 . A first filtering capacitor C 1  is coupled in series with a second filtering resistor R 2  and a third filtering resistor R 3  between the first filtering node  86  and a first input  88  to the operational amplifier  84 . A fourth filtering resistor R 4  is coupled between the first filtering node  86  and ground. A second input  90  to the operational amplifier  84  is also coupled to ground. 
         [0033]    The envelope detection circuitry  80  includes an envelope detection diode D_ET including an anode coupled to an output of the operational amplifier  84  and a cathode coupled to an output node  92  of the RF power detection circuitry  76 . Further, the envelope detection circuitry  80  includes an envelope tracking capacitor C_ET and an envelope tracking resistor R_ET coupled between the output node  92  of the RF power detection circuitry  76  and ground. 
         [0034]    In operation, the filtration and amplification circuitry  78  acts as a bandpass filter, isolating a desired frequency band of the coupled RF signal RF_C and amplifying it. The envelope detection circuitry  80  tracks an envelope of the output signal from the operational amplifier  84  to provide the RF detection voltage signal V_DET. Notably, the details of the RF power detection circuitry  76  shown in  FIG. 7  are merely exemplary. That is, the RF power detection circuitry  76  can be implemented in any number of ways and perform any type of signal conditioning on the coupled RF signal RF_C without departing from the principles of the present disclosure. 
         [0035]      FIG. 8  shows the RF PA circuitry  42  including an analog feedback loop  94  according to one embodiment of the present disclosure. The feedback loop  94  includes the RF power coupler  44 , the RF power detection circuitry  76 , an error amplifier  96 , and a variable gain amplifier  98 . The error amplifier  96  includes a first input connected to the RF power detection circuitry  76  and a second input connected to a reference voltage V_REF. An output of the error amplifier  96  is connected to the variable gain amplifier  98  such that gain control signal G_C controls a gain of the variable gain amplifier  98 . 
         [0036]    In operation, the coupled RF signal RF_C is delivered to the RF power detection circuitry  76 , where it is conditioned as desired and provided as the RF detection voltage signal RF_DET. The RF detection voltage signal RF_DET is then compared to the reference voltage V_REF by the error amplifier  96 . The resulting gain control signal G_C is provided to the variable gain amplifier  98 , which is coupled between the RF input node  46  and the RF PA  50 . By changing the gain of the variable gain amplifier  98 , the output power of the RF PA  50  may also be adjusted. Accordingly, the feedback loop  94  may control one or more aspects of the operation of the RF PA  50  to increase the performance thereof. Additional embodiments may use an analog to digital (A/D) converter to implement the power control digitally. 
         [0037]    Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein and the claims that follow.