Patent Publication Number: US-11658717-B2

Title: Multi-beam antenna system with a baseband digital signal processor

Description:
RELATED APPLICATIONS 
     The present invention is a continuation application of U.S. application Ser. No. 17/480,147 filed 21 Sep. 2021. The Ser. No. 17/480,147 application is a continuation application of U.S. application Ser. No. 17/258,345, filed on 6 Jan. 2021, which is a U.S. National Stage under 35 USC 371 patent application, claiming priority to Serial No. PCT/US2019/041627, filed on 12 Jul. 2019, which claims priority from U.S. provisional application No. 62/697,518, filed on 13 Jul. 2018, the entirety of both of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This disclosure relates generally to communication systems, and more specifically to a multi-beam antenna system with a baseband digital signal processor. 
     BACKGROUND 
     An antenna array (or array antenna) is a set of multiple antenna elements that work together as a single antenna to transmit or receive radio waves. The individual antenna elements can be connected to a receiver and/or transmitter by circuitry that applies an appropriate amplitude and/or phase adjustment of signals received and/or transmitted by the antenna elements. When used for transmitting, the radio waves radiated by each individual antenna element combine and superpose with each other, adding together (interfering constructively) to enhance the power radiated in desired directions, and cancelling (interfering destructively) to reduce the power radiated in other directions. Similarly, when used for receiving, the separate received signals from the individual antenna elements are combined with the appropriate amplitude and/or phase relationship to enhance signals received from the desired directions and cancel signals from undesired directions. 
     SUMMARY 
     One example includes a phased-array antenna system. The system includes antenna elements each including an element adjustment circuit and a radiating element. A beamforming network receives a carrier signal and generates element carrier signals. A baseband DSP generates a plurality of composite beamforming data signals associated with a respective one of the antenna elements and is generated based on combining individual beamforming data signals. Each of the individual beamforming data signals is associated with a respective beam and is based on combining a data signal associated with the respective beam with an antenna weight associated with the respective beam and the respective one of the antenna elements. The element adjustment circuit modulates the associated composite beamforming data signal onto the respective element carrier signal to generate a respective element signal that is provided to the respective radiating element, such that the beams are generated from the antenna elements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates an example of an antenna system. 
         FIG.  2    illustrates an example of a baseband digital signal processor. 
         FIG.  3    illustrates an example of an antenna element. 
         FIG.  4    illustrates an example of a PSK modulation scheme. 
         FIG.  5    illustrates an example of an APSK modulation scheme. 
         FIG.  6    illustrates an example of a method for transmitting a plurality of beams from a phased-array antenna system. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure relates generally to communication systems, and more specifically to a multi-beam antenna system with a baseband digital signal processor. An antenna system can be arranged as a phased-array antenna system that includes a plurality of antenna elements. The antenna system can include a beam source that provides a carrier signal to a beamforming network. The beamforming network can distribute a respective element carrier signal to each of the antenna elements based on the carrier signal. The antenna system includes a baseband digital signal processor (DSP) that is configured to generate a plurality of combined beamforming data signals that are each associated with a respective one of the antenna elements. The combined beamforming data signals are each generated based on a respective one of a plurality of beamforming signals and a plurality of data signals. Each of the data signals can correspond to a separate respective one of beams that are transmitted from the phased-array antenna system via the antenna elements. 
     For example, the baseband DSP can modulate the beamforming signals as complex weights onto each of the data signals to generate a set of modulated data signal. The baseband DSP can add each of the modulated data signals associated with a given one of the antenna elements to generate the combined beamforming data signals. The combined beamforming data signals can be polar coordinate converted to provide the combined beamforming data signals as including a phase portion and an amplitude portion to each of the antenna elements. As an example, the combined beamforming data signals can be provided as a phase-shift keying (PSK) code or an amplitude phase-shift keying (APSK) code. The phase portion and the amplitude portion can thus each be provided to at least one digital-to-analog converter (DAC) of a respective element adjustment circuit of the respective antenna element. The DAC(s) can convert the phase portion and the amplitude portion into at least one respective analog signal that is modulated onto the element carrier signal (e.g., via at least one of a phase-shifter and a variable gain amplifier (VGA)). Therefore, the element adjustment circuit can generate an element signal that is provided to a radiating element for transmission of the multiple beams from the antenna elements. 
       FIG.  1    illustrates an example of an antenna system  10 . The antenna system  10  can correspond to a phased-array antenna system, or can correspond to a single reticle of an antenna system that includes multiple substantially identical reticles. The antenna system  10  can thus transmit a plurality N of element signals as a plurality Y of separate beams, demonstrated in the example of  FIG.  1    as beams B 1  through B Y , in directions (e.g., in any of a variety of angles between 0° and approximately 60°) that is based on a relative phase of the element signals, as described in greater detail herein. 
     The antenna system  10  includes a beam source  12  that is configured to generate a carrier signal BS, such as based on a local oscillator configured to generate a reference signal at a predetermined frequency. As an example, the beam source  12  can be configured as a programmable synthesizer configured to provide the carrier signal BS at a predetermined frequency. The carrier signal BS is provided to a carrier signal port of a beamforming network  14  that is configured to generate a plurality N of element carrier signals ES, demonstrated in the example of  FIG.  1    as element carrier signals ES 1  through ES N , where N is a positive integer, at a plurality of element carrier signal ports. For example, the beamforming network  14  can be implemented as stages of divider circuits. The number of stages can vary from embodiment to embodiment. As an example, each divider circuit can be implemented as a power divider circuit, such as a Wilkinson power divider, a hybrid coupler, a directional coupler, or nearly any other circuit that can divide signals. As an example, N can be equal to sixty-four for a given reticle. The element carrier signals ES are provided to a respective plurality N of antenna elements  16  that can be formed in an array (e.g., a beamforming array). As described in greater detail herein, the antenna elements  16  can each be configured to transmit a respective element signal via a radiating element in a phase-shifted and/or amplified manner relative to each other to implement beamforming. 
     In addition, the antenna system  10  includes a beamforming controller  18  and a data controller  20 . The beamforming controller  18  is configured to generate a plurality Y of beamforming signals BF 1  through BF Y , where Y corresponds to the number of beams B 1  through B Y  to be transmitted from the antenna system  10 . Each of the beamforming signals BF can correspond to a set of complex antenna weights that defines phase and/or amplitude information to be applied to the element signals by the element adjustment circuits (described in more detail below) to form a given one of the beams B 1  through B Y  to be transmitted from the antenna system  10 . For example, based on the arrangement of the array of antenna elements  16  and the desired direction of the respective beams B 1  through B Y  to be transmitted from the antenna system  10 , the beamforming controller  18  can calculate the beamforming signals BF 1  through BF Y  in any of a variety of ways (e.g., in response to one or more control signals (not shown)). Additionally, the directions of the beams B 1  through B Y  can change (e.g., relative to each other) based on the operation of the beamforming controller  18 . 
     Therefore, the beamforming signals BF can collectively define the beamforming information associated with the aggregate transmission of the element signals to provide transmission directions of the beams B 1  through B Y  in respective predetermined directions for each of the multiple beams B 1  through B Y  to be transmitted from the antenna system  10 . As an example, the beamforming controller  18  can be configured as a processor or application specific integrated circuit (ASIC) configured to generate the beamforming signals BF in response to one or more commands associated with a desired transmission direction of the beams B 1  through B Y  formed by the element signals. The data controller  20  is configured to generate a plurality of data signals DS, demonstrated in the example of  FIG.  1    as data signals DS 1  through DS Y , where Y corresponds to the number of beams B 1  through B Y  to be transmitted from the antenna system  10 . For example, the data signals DS 1  through DS Y  can correspond to information data signals that are each modulated into the aggregate transmitted element signals. 
     In the example of  FIG.  1   , the beamforming signals BF 1  through BF Y  and the data signals DS 1  through DS Y  are demonstrated as being provided to a baseband digital signal processor (DSP)  22 . The baseband DSP  22  is configured to modulate the beamforming signals BF 1  through BF Y  and the data signals DS 1  through DS Y  to generate combined beamforming data signals ΦA, demonstrated as ΦA 1  through ΦA N , that are each provided to a respective one of the antenna elements  16 . Each of the combined beamforming data signals ΦA can include phase and amplitude information to provide beamforming for each of the data signals DS. For example, and as described in greater detail herein, the combined beamforming data signals ΦA can be generated in the digital domain to be modulated into the respective element carrier signals ES at the respective antenna elements  16 , such that the antenna elements  16  can transmit multiple beams B 1  through B Y  corresponding to the respective data signals DS 1  through DS Y  based on the phase and amplitude information associated with the beamforming signals BF 1  through BF Y . While the quantity Y is demonstrated for both the data signals DS 1  through DS Y  and the beamforming signals BF 1  through BF Y , it is to be understood that the beamforming controller  18  and the data controller  20  are not limited to providing an equal number of data signals DS and beamforming signals BF. For example, the same data signal DS can be transmitted via multiple beams B. 
     In the example of  FIG.  1   , the antenna elements  16  each include an element adjustment circuit  24 . The element adjustment circuit  24  can modulate the combined beamforming data signals ΦA into the respective element carrier signals ES to generate the respective element signal for transmission. For example, the element adjustment circuit  24  can include at least one digital-to-analog converter (DAC) to convert a respective at least one of a phase portion and an amplitude portion of the combined beamforming data signals ΦA into a respective at least one analog signal. The element adjustment circuit  24  can include a respective at least one of a phase-shifter and a variable gain amplifier (VGA) to adjust the phase and/or amplitude of the respective element carrier signal ES based on the analog signal(s) to generate the respective element signal. Therefore, the element signal can be transmitted from each of the respective antenna elements  16  (e.g., via a radiating element) to provide transmission of multiple independent beams B 1  through B Y  concurrently in a phased-array manner. 
     For example, each of the beams B 1  through B Y  can be associated with a respective one of the data signals DS 1  through DS Y , and the complex baseband signal of the respective data signal DS can be part of the individual beamforming data signal that is generated for each antenna element  16 . As a result, the complex baseband signal can be common across the antenna elements  16 , and thus does not affect the direction of the respective beam B. Accordingly, the direction of each of the beams B 1  through B Y  can be determined by the set of antenna weights corresponding to that respective one of the beams B 1  through B Y . The multiplication of the complex baseband signal by the set of antenna weights, when used to generate and subsequently transmit the element signals, can (e.g., via constructive interference) result in the respective one of the beams B 1  through B Y  being formed in the desired direction and containing the associated data signal DS based on the superposition of all of the element signals associated with the respective antenna elements  16 . Each of the beams B 1  through B Y  can be formed in this manner to allow beams associated with different data signals (e.g., the data signals DS 1  through DS Y ) to be transmitted simultaneously in different directions from the antenna system  10  via the antenna elements  16 . 
     By implementing the modulation of the data signals DS and the beamforming signal BF together via the baseband DSP  22 , the combined beamforming data signals ΦA can be generated in the digital domain. Therefore, the digital combined beamforming data signals ΦA are modulated onto the analog element carrier signals ES in the antenna elements  16  to provide for concurrent transmission of multiple separate and independent beams B 1  through B Y  from the antenna system  10 . Furthermore, by digitally combining the data signals DS and the beamforming signals BF via the baseband DSP  22 , the antenna system  10  can achieve concurrent transmission of the multiple independent beams B 1  through B Y  in a more hardware efficient manner as opposed to typical antenna systems that transmit multiple beams B 1  through B Y . For example, a phased-array antenna system that transmits multiple independent beams B 1  through B Y  by concurrently combining modulated analog signals at each of the associated antenna elements requires significantly more hardware, and thus a significant increase in cost and physical space. However, as described herein, by digitally modulating the data signals DS and the beamforming signal BF together via the baseband DSP  22 , the phase and/or amplitude information of each of the multiple beams B 1  through B Y  is already digitally combined before being provided to the antenna elements  16 . As a result, the antenna elements  16  need not include respective sets of combining hardware, which thus provides for a more simplified and efficient beam combining scheme to provide transmission of the multiple beams B 1  through B Y  from the phased-array antenna system  10 . 
       FIG.  2    illustrates an example of a baseband DSP  50 . The baseband DSP  50  can correspond to the baseband DSP  22  in the example of  FIG.  1   . Therefore, reference is to be made to the example of  FIG.  1    in the following description of the example of  FIG.  2   . 
     The baseband DSP  50  includes a first modulator  52  and a second modulator  54  that each correspond to separate beams B 1  and B 2  to be transmitted from the antenna system  10 . The first modulator  52  is configured to receive the first data signal DS 1  and to convert the first data signal DS 1  into a complex baseband signal, demonstrated in the example of  FIG.  2    as DSC 1 . Similarly, the second modulator  54  is configured to receive the second data signal DS 2  and to convert the second data signal DS 2  into a complex baseband signal, demonstrated in the example of  FIG.  2    as DSC 2 . For example, the complex baseband signals DSC 1  and DSC 2  can each include in-phase and quadrature-phase channels that collectively form a complex phasor. In the example of  FIG.  2   , the baseband DSP  50  includes only two modulators  52  and  54 , thus rendering Y=2 by example. However, it is to be understood that the baseband DSP  50  can include more than two modulators, each corresponding to a separate one of the beams B 1  and B 2  concurrently transmitted from the antenna system  10 . 
     The complex baseband signals DSC 1  and DSC 2  are demonstrated as each being modulated by N separate antenna weights W that can also correspond to complex phasors associated with beamforming information. In the example of  FIG.  2   , the antenna weights W are demonstrated as numbering in a quantity N for each of the modulators  52  and  54 , with N corresponding to the number of antenna elements  16 , as provided in the example of  FIG.  1   . The baseband DSP  50  is demonstrated as receiving a first set of antenna weights W 1,1  through W 1, N  corresponding to the first modulator  52  and a second set of antenna weights W 2, 1  through W 2, N  corresponding to the second modulator  54 . For example, each of the beamforming signals BF can correspond to a set of the antenna weights corresponding to a respective one of the separate beams B 1  and B 2  to be transmitted from the antenna system  10 . For example, the first beamforming signal BF 1  can correspond to the antenna weights W 1, 1  through W 1, N , and the second beamforming signal BF 2  can correspond to the antenna weights W 2, 1  and W 2, N . 
     In the example of  FIG.  2   , the baseband DSP  50  includes a first set of digital multipliers  56  and a second set of digital multipliers  58 . The first set of digital multipliers  56  are configured to multiply the complex baseband signal DSC 1  by each of the antenna weights of the first set of antenna weights W 1, 1  through W 1, N . Similarly, the second set of digital multipliers  58  are configured to multiply the complex baseband signal DSC 2  by each of the antenna weights of the first set of antenna weights W 2, 1  through W 2, N . Therefore, the digital multipliers  56  and  58  provide the modulation of the complex baseband signals DSC 1  and DSC 2  with the respective sets of antenna weights W. In the example of  FIG.  2   , the first set of digital multipliers  56  generate a set of individual beamforming data signals M 1, 1  through M 1, N  corresponding to a product of the complex baseband signal DSC 1  and the respective first set of antenna weights W 1, 1  through W 1, N . Similarly, the second set of digital multipliers  58  generate a set of individual beamforming data signals M 2, 1  through M 2, N  corresponding to a product of the complex baseband signal DSC 2  and the respective first set of antenna weights W 2, 1  through W 2, N . As an example, the individual beamforming data signals M 1, 1  through M 1, N  and M 2, 1  through M 2, N  can correspond to complex phasors each including an in-phase portion and a quadrature-phase portion. 
     The baseband DSP  50  also includes a set of adders  60  that are each configured to add one of the individual beamforming data signals M 1, 1  through M 1, N  with a corresponding one of the individual beamforming data signals M 2, 1  through M 2, N . Therefore, each of the adders  60  generates a combined beamforming data signal, demonstrated in the example of  FIG.  2    as combined beamforming data signals CP 1  through CP N , that each correspond to a sum of a set of one of the individual beamforming data signals M 1, 1  through M 1, N  and a corresponding one of the individual beamforming data signals M 2, 1  through M 2, N  that is associated with the modulators  52  and  54 , and thus each of the separate beams B 1  and B 2  to be transmitted from the antenna system  10 . Similar to as described previously, the combined beamforming data signals CP 1  through CP N  can correspond to complex phasors including an in-phase portion and a quadrature-phase portion. Therefore, each of the combined beamforming data signals CP 1  through CP N  includes data and beamforming information associated with each of the separate beams B 1  and B 2  to be transmitted from the antenna system  10 . The combined beamforming data signals CP 1  through CP N  are provided to polar converters  62  that are configured to convert the combined beamforming data signals CP 1  through CP N  to a polar coordinate system to generate the respective combined beamforming data signals ΦA 1  through ΦA N . Accordingly, each of the combined beamforming data signals ΦA 1  through ΦA N  can include phase and amplitude portions corresponding to each of the data signals DS 1  and DS 2 . The combined beamforming data signals ΦA 1  through ΦA N  are thus provided to the antenna elements  16 , as described previously in the example of  FIG.  1   , for modulation of the respective element carrier signals ES for transmission of each of the separate beams B 1  and B 2 . 
       FIG.  3    illustrates an example of an antenna element  100 . The antenna element  100  can correspond to one of the antenna elements  16  in the example of  FIG.  1   . Particularly, the antenna element  100  is demonstrated in the example of  FIG.  3    as “ANTENNA ELEMENT X”, where X corresponds to a given one of the N antenna elements  16 . Therefore, reference is to be made to the examples of  FIGS.  1  and  2    in the following example of  FIG.  3   . As an example, the antenna element  100  can be fabricated as a multi-layer integrated circuit. 
     The antenna element  100  includes an element adjustment circuit  102  that is configured to modulate a respective one of the element carrier signals, demonstrated in the example of  FIG.  3    as ES X , with a respective combined beamforming data signal ΦA to generate a respective element signal, demonstrated in the example of  FIG.  3    as AES X . In the example of  FIG.  3   , the combined beamforming data signal ΦA is demonstrated as being separated into a phase portion, demonstrated as Φ X , and an amplitude portion A X . The phase portion Φ X  thus corresponds to the phase information associated with the respective combined beamforming data signal ΦA X , and thus the desired phase of the resultant respective element signal AES X . Similarly, the amplitude portion A X  thus corresponds to the amplitude information associated with the combined beamforming data signal ΦA X , and thus the desired amplitude of the resultant respective element signal AES X . 
     In the example of  FIG.  3   , the element adjustment circuit  102  includes at least one DAC. In the example of  FIG.  3   , the at least one DAC includes a first DAC  104 , demonstrated as “PH-DAC”, and a second DAC  106 , demonstrated as “A-DAC”. The first DAC  104  is configured to convert the phase portion Φ X  of the combined beamforming data signal ΦA X  into a first analog signal ALG 1 . In the example of  FIG.  3   , the first analog signal ALG 1  is provided to a phase-shifter  108  that is configured to modulate the respective element carrier signal ES X  based on the first analog signal ALG 1 . As an example, the phase-shifter  108  can be configured as a vector modulator, such that the phase-shifter  108  can provide a phase-shift of the respective element carrier signal ES X  based on the phase information associated with the phase portion Φ X  of the combined beamforming data signal ΦA X . 
     Similarly, the second DAC  106  is configured to convert the amplitude portion A X  of the combined beamforming data signal ΦA X  into a second analog signal ALG 2 . The second analog signal ALG 2  is provided to a variable gain amplifier (VGA)  110  that is configured to modulate the respective element carrier signal ES X  based on the second analog signal ALG 2 . As an example, the VGA  110  can provide amplification of the respective phase-shifted element carrier signal ES X  based on the amplitude information A X  of the combined beamforming data signal ΦA X  to generate the respective element signal AES X . 
     The element signal AES X  is thus provided from the element adjustment circuit  102  to a power amplifier (PA)  112 , and can thus be transmitted from the antenna element  100  via a radiating element  114 . As a result, the respective element signal AES X  can be transmitted along with the remaining element signals AES from the respective other antenna elements  100  in a relatively phase-shifted manner that defines a transmission direction of the aggregate beams B 1  through B Y  (e.g., B 1  and B 2 ). Accordingly, the aggregate beams can propagate the data signals DS 1  through DS Y  (e.g., DS 1  and DS 2 ) modulated onto the aggregate beams (e.g., via the respective element signals AES) in directions that are based on the respective beamforming signals BF (e.g., the antenna weights W 1, 1  through W 1, N  and antenna weights W 2, 1  through W 2, N ). 
     As described previously, the combined beamforming data signals ΦA can include phase information, and can also include amplitude information, such as to generate a modulation scheme associated with a specific type of data constellation. As a first example, the combined beamforming data signal ΦA can include phase information only, such as to generate a phase-shift keying (PSK) modulation scheme associated with one or more of the transmitted beams B 1  through B Y . As another example, the combined beamforming data signal ΦA can include both phase information and amplitude information, such as to generate an amplitude phase-shift keying (APSK) modulation scheme associated with one or more of the transmitted beams B 1  through B Y . 
       FIG.  4    illustrates an example diagram  150  of a PSK modulation scheme. The diagram  150  demonstrates a circle with eight separate states arranged in 45° intervals about a constellation, as defined by a three-bit code, and thus demonstrates an 8-PSK code. Therefore, the three bits of the data code can correspond to the angle of a data code about the constellation. However, as an example, fewer or additional PSK modulation codes can be implemented based on the data controller  20 . 
       FIG.  5    illustrates an example diagram  200  of an APSK modulation scheme. The diagram  200  demonstrates two concentric circles, each with eight separate states arranged in 45° intervals about a constellation. The diagram  200  thus demonstrates a 16-APSK code, as defined by a four-bit data code. In the example of  FIG.  5   , the most significant bit determines a distance from center of the code, and thus the three additional bits dictate the angle of the code in the constellation. However, as an example, fewer or additional APSK modulation codes can be implemented by the data controller  20 . 
     In view of the foregoing structural and functional features described above, a methodology in accordance with various aspects of the present invention will be better appreciated with reference to  FIG.  6   . While, for purposes of simplicity of explanation, the methodology of  FIG.  6    is shown and described as executing serially, it is to be understood and appreciated that the present invention is not limited by the illustrated order, as some aspects could, in accordance with the present invention, occur in different orders and/or concurrently with other aspects from that shown and described herein. Moreover, not all illustrated features may be required to implement a methodology in accordance with an aspect of the present invention. 
       FIG.  6    illustrates an example of a method  250  for transmitting a plurality of beams (e.g., the beams B 1  through B Y ) from a phased-array antenna system (e.g., the antenna system  10 ). At  252 , a plurality of element carrier signals (e.g., the element carrier signals ES) are generated via a beamforming network (e.g., the beamforming network  14 ) in response to a carrier signal (e.g., the carrier signal BS). At  254 , each of a plurality of data signals (e.g., the data signals DS) associated with the respective plurality of beams (e.g., the beams B 1  through B Y ) is combined with each of a plurality of beamforming signals (e.g., the beamforming signals BF) to generate a plurality of individual beamforming data signals (e.g., the individual beamforming data signals M) via a baseband DSP (e.g., the baseband DSP  22 ). Each of the plurality of beamforming signals can be associated with a respective one of a plurality of antenna elements (e.g., the antenna element  16 ) and one of the plurality of beams. 
     At  256 , a plurality of sets of the individual beamforming signals are combined to generate a plurality of composite beamforming data signals (e.g., the combined beamforming data signals ΦA) that are each associated with a respective one of the plurality of antenna elements via the DSP. At  258 , each of the plurality of combined beamforming data signals are modulated onto a respective one of the plurality of element carrier signals to generate a respective one of a plurality of element signals (e.g., the element signal AES X ). At  260 , each of the plurality of element signals are provided to a respective radiating element (e.g., the radiating element  114 ) associated with a respective plurality of antenna elements to transmit the plurality of beams from the plurality of antenna elements. 
     What have been described above are examples of the present invention. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present invention, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present invention are possible. Accordingly, the present invention is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims. Additionally, where the disclosure or claims recite “a,” “an,” “a first,” or “another” element, or the equivalent thereof, it should be interpreted to include one or more than one such element, neither requiring nor excluding two or more such elements. As used herein, the term “includes” means includes but not limited to, and the term “including” means including but not limited to. The term “based on” means based at least in part on.