|||||||||||||||||||||||||||lllllllllllllll|l|||||||||||||||||lll|ll||ll||ll
`USOOSS41607A
`5,541,607
`[11] Patent Number:
`[19]
`United States Patent
`
`
`Reinhardt Jul. 30, 1996 [45] Date of Patent:
`
`[54] POLAR DIGITAL BEAR/{FORMING NIETHOD
`AND SYSTEM
`
`[75]
`
`Inventor: Victor S. Reinhardt, Rancho Palos
`Verdes, Calif.
`
`[73] Assignee: Hughes’Electronics, Los Angeles,
`Cahf'
`
`'
`
`[21] APPL N05 349/642
`.
`.
`[22] Filed'
`Dec. 5’ 1994
`[51]
`Int. Cl.6 .............................. HOIQ 3/22;H01Q 3/24;
`H01Q 3/26
`[52] US. Cl. ............................. 342/372; 342/157; 342/31
`[58] Field of Search ..................................... 342/372, 157,
`342/81
`
`[56]
`
`References Cited
`
`U-S- PATENT DOCWENTS
`4,965,588 10/1990 Lenormand et al.
`................... 342/372
`4,983,981
`1/1991 Feldman ............. 342/372
`5,093,667
`3/1992 Andn'cos ................................. 342/372
`
`Primary Examiner—Theodore M. Blum
`Attorney, Agent, or Finn—Elizabeth E. Leitereg; Terje Gud-
`mestad; W. K. Benson-Low
`
`[57]
`
`ABSTRACT
`
`A system and method for polar digital beamfonning of at
`least one independent transmit beam is disclosed. A com-
`puter generates a digital signal representing both pointing
`and modulation information which is communicated to a
`plurality of subarray controllers which generate the polar
`weighting signals corresponding to the appropriate antenna
`element for transmitting. The complex weighting signals
`may be generated by summing a sequence of complex
`multiplications or by simply inverting the real and imaginary
`components of the weighting signal for particular modula-
`“on scheme A Phasor may be used in conjunction with an
`attenuator to modulate a local carrier signal. Alternatively,
`phasors are utilized without attenuators to increase the
`efliciency of the power amplifiers. The antenna architecture
`disclosed permits a single set of phasors and attenuators to
`be utilized per antenna element regardless of the number of
`beams to be generatcd-
`
`18 Claims, 3 Drawing Sheets
`
`
`
`
`gubarrlay
`64
`
`
`‘ ontro er
`
`Subarrayl
`
`
`RF
`---‘------—--- —----~---—.—
`Local
`46
`Z
`
`
`Oscillator
`_______________-_,
`ll
`
`44
`
`40
`
`ZTE, Exhibit 1014-0001
`
`I L
`
`l l
`
`.<‘5n
`
`
`
`ZTE, Exhibit 1014-0001
`
`

`

`US. Patent
`
`Jul. 30, 1996
`
`Sheet 1 of 3
`
`5,541,607
`
`18
`
`
` Splitter Signal
`
`1____"1___
`_Comple)_(
`l
`
`
`Weighting Circuit
`,l
`I
`
`
`Modulator
`
`||
`
`I;a
`
`TMJUL 0,!
`
`
`
`mm Dm'
`
`
`571W 2
`
`ZTE, Exhibit 1014-0002
`
`ZTE, Exhibit 1014-0002
`
`

`

`US. Patent
`
`,
`
`Jul.30, 1996
`
`Sheet20f3
`
`5,541,607
`
`RF
`Local
`Oscillator
`
`N-Way
`Power
`
`Splitter
`to An and on
`
`Modulation
`Sm(t)'Data Bus
`5n1(t)
`Storage Registers
`
`70
`
`PoPinting Weights
`Pmn Data Bus
`Pmn .
`Storage RegIsters
`
`:
`
`;
`I
`
`72
`
`Multiplier Forms M Complex Products
`Ymn = Sn1(t)xpmn
`
`Accumulators forms Vn(t)
`Vtn(t)= EYmn
`
`Cartesian to Polar Look- up Table Conversions Vt(t)
`
`ZTE, Exhibit 1014-0003
`
`ZTE, Exhibit 1014-0003
`
`

`

`US. Patent
`
`Jul. 30, 1996
`
`Sheet 3 of 3
`
`5,541,607
`
`lnput Data Stream
`Sm(t) Data Bus
`
`90
`
`Pointing Weights
`Pmn Data Bus
`
`92
`
`I
`
`I
`
`l'\ll
`
`-::.0o
`
`Smlt)
`Storage Registers
`
`Change Sign of Real and Imaginary
`Parts of Pmn to Form Ymn
`
`Accumulatorsformthn(t)
`
`7
`
`50'
`
`58’
`
`48’
`
`
`
`a,
`Subarray
`5
`‘ m Controller
`—————————————————
`46’
`.
`_________________
`
`Vn(t)= ZYmn
`62’
`
`aI
`
`Subarray
`
`!
`
`I
`
`Computer
`
`40!
`
`ZTE, Exhibit 1014-0004
`
`.
`
`64’
`
`‘
`
`RF
`Local
`Oscillator
`
`60’
`
`N-Way
`Power
`Splitter
`
`ZTE, Exhibit 1014-0004
`
`

`

`5,541,607
`
`1
`POLAR DIGITAL BEAMFORMJNG METHOD
`AND SYSTEM
`
`TECHNICAL FIELD
`
`This invention relates to transmit phased array antennas
`and more particularly to a method and system of digital
`bearnforming using a polar element weighting configuration.
`
`BACKGROUND ART
`
`A beamsteered transmit phased array antenna allows
`electronic steering of the antenna beam direction. This type
`of antenna system includes a number of individual antenna
`elements spaced in a regular array. The beam direction of the
`antenna (i.e., pointing direction) is controlled by the relative
`phases of the signals radiated by the individual antenna
`elements. As is known, phased arrays may be used to
`produce highly directional radiation patterns. Furthermore,
`performance characteristics normally associated with anten-
`nas having large areas can be achieved with a phased array
`antenna having a comparatively smaller area. Conventional
`transmit phased array antennas utilize two basic architec-
`tures: analog beamforming (ABF) and digital beamforming
`(DBF).
`The basic analog bearnforrning approach found in the
`prior art is illustrated in FIG. 1. This system comprises a
`local radio-frequency (RF) oscillator 10 and an associated
`signal modulator 12 to produce an RF signal expressed in
`complex form as:
`
`S(t)-SAD-CU)
`
`(l)
`
`10
`
`15
`
`20
`
`25
`
`30
`
`where Sb(t) is the complex carrier provided by the RF
`oscillator and given by:
`
`35
`
`C(t)—A,e"°v'
`
`(2)
`
`where Sb(t) is the complex baseband waveform generated by
`the signal modulator. The signal S(t) is then distributed to n
`subarrays 141 to 14,, by a splitter 16. Each subarray consists
`of a digitally controlled complex weighting circuit 18, a
`power amplifier 20, and an antenna element 22. Each
`complex weighting circuit produces a controlled phase and
`amplitude shift in its corresponding subarray RF signal. The
`signal is then amplified by power amplifier 18 and radiated
`by antenna element 22.
`If each complex weight is represented by P", then the
`signals at the output of each weighting circuit may be
`represented by Pn-S(t). The far field radiation pattern will
`depend upon the number and type of antenna elements, the
`spacing of the array, and the relative phase and magnitude of
`the excitation currents applied to the various antenna ele—
`ments. Generally, the electric field (E—field) generated by the
`entire phased array is of the form:
`
`E(k) = F(k)S(r) Ze‘fk‘nnPn
`n
`
`(3)
`
`where k is the wave vector, r” is the position of the nth
`element, and F(k) is proportional to the E-field generated by
`a single element. The sum in (3) is maximized in the
`direction of k when
`
`Pnueik‘"
`
`(assuming approximately equal magnitudes for all the P").
`Thus,
`the phased array can be electronically steered by
`manipulating the complex weights P".
`
`45
`
`50
`
`55
`
`65
`
`2
`One of the advantages of a phased array is that a number
`of beams in can be sent from the same aperture. However,
`to accomplish this, ABF requires the same number In sets of
`local oscillators, signal modulators, power splitters, and
`weighting circuits. At the input of each subarray power
`amplifier, the m beams are combined to produce a single
`radiation signal out of each antenna element. The various
`beam signals then combine in phase in m different directions
`so as to produce an m-beam output. The resultant E-field of
`the far field signal is given by:
`
`E(k) 2 F(k) 2 e'ik‘m 2‘. PMSMO)
`n
`m
`
`(5)
`
`which represents m independent beams in the far field.
`In digital beamforrrring (DBF), the beam pointing infor—
`mation represented by the complex weights and the modu-
`lation information are generated digitally. For one beam, the
`operation of the complex weighting circuit on the modulated
`RF signal can be represented as the multiplication of a
`complex modulation function by a complex weighting num-
`ber. For multiple beams,
`these In complex products are
`summed to produce a single complex number for each
`subarray. This signal may be represented by:
`
`V,.(t) = )3 PMS,,m(t)
`m
`
`(6)
`
`where S,,m(t) is either Sm(t) or Sb_m(t). One or more digital
`to analog (D/A) converters are then utilized to produce an
`analog representation of V"(t) for each individual antenna
`element. Thus, only a single Set of digitally controlled
`complex weighting circuits is required thereby eliminating
`much of the hardware required to generate a similar signal
`using ABF techniques. The disadvantage of DBF is that a
`large number of complex multiplications (m-n) and complex
`additions (n) must be performed at a rate equal
`to the
`modulation rate. This requires the use of a high speed
`processor which typically consumes a great deal of power.
`Two implementations of DBF have been utilized in the
`prior art: baseband Cartesian DBF and intermediate fre-
`quency (IF) DBF. Cartesian DBF uses a linear in-phase and
`quadrature (I-Q) modulator and two (2) D/A converters for
`each complex weighting circuit. The IF DBF technique
`utilizes D/A converters to directly produce the modulated
`subarray signals at the intermediate frequency. Upconverters
`are then required to convert these signals to RF signals. Both
`Cartesian DBF and IF DBF are characterized by complex
`implementations which require a significant amount of
`power. These implementations are not cost efiective unless
`a very large number of beams are required.
`
`SUMMARY OF THE INVENTION
`
`therefore, an object of the present invention to
`It is.
`provide a multiple—bearn phased array antenna which digi-
`tally generates pointing and modulation information and
`utilizes a simple polar architecture.
`A further object of the present invention is to provide a
`multiple-beam phased array antenna which utilizes a single
`set of phasors and attenuators per antenna element.
`Another object of the present invention is to provide a
`multiple-beam phased array antenna which utilizes a single
`set of phasors without attenuators for each antenna element.
`Yet another object of the present invention is to provide a
`multiple-beam phased array antenna which utilizes previ-
`ously developed phasors, attenuators, and digital Applica-
`tion Specific Integrated Circuits (ASICs) to implement polar
`digital beamforming.
`
`ZTE, Exhibit 1014-0005
`
`ZTE, Exhibit 1014-0005
`
`

`

`5,541,607
`
`3
`In carrying out the above objects and other objects and
`features of the present invention, a a method for digital
`beamforming of at least one independent transmit beam
`includes generating a modulation signal representing infor-
`mation to be transmitted in at least one independent transmit
`beam, generating a pointing signal representing a beam
`pointing direction for the transmit beam(s), and generating
`a weighting signal for each of the plurality of antenna
`elements based on the modulation signal and the pointing
`signal. Each weighting signal is then converted to a corre—
`sponding attenuation signal and a corresponding phase sig-
`nal which is utilized to control each of a plurality of phasors
`to modulate a carrier signal. The modulated carrier signal is
`then applied to a corresponding antenna element for trans-
`mission.
`
`A system is also provided for implementing the steps of
`the method.
`
`The above objects and other objects, features, and advan—
`tages of the present invention will be readily appreciated by
`one of ordinary skill in the art from the following detailed
`description of the best mode for carrying out the invention
`when taken in connection with the accompanying drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 illustrates a prior art transmit phased array antenna
`using an analog beamforming architecture;
`FIG. 2 is a block diagram illustrating a multiple-beam
`phased array antenna system according to the present inven-
`tion;
`FIG. 3 is a block diagram of a multiple-beam phased array
`antenna utilizing polar digital beamforming according to the
`present invention;
`FIG. 4 is a functional block diagram illustrating the
`functions performed by the subarray controllers of FIG. 3 for
`a general modulation scheme;
`FIG. 5 is a functional block diagram illustrating the
`functions performed by the subarray controllers ofFIG. 3 for
`simplified modulation schemes; and
`FIG. 6 is a functional block diagram illustrating a sim-
`plified multiple-beam phased array antenna implementing
`polar digital beamforming utilizing phasors without attenu-
`ators.
`
`BEST MODES(S) FOR CARRYING OUT THE
`INVENTION
`
`Referring now to FIG. 2, a block diagram of a multiple—
`beam phased array antenna system utilizing a polar digital
`beamforming architecture is shown. Digital data signals D1
`to Dm represent data to be transmitted over a communication
`channel via a multiple-beam phased array antenna. Data
`signals D1 to D", are communicated to a computer 30 which
`controls a polar digital bearnforrning (PDBF) array module
`32. Computer 30 combines the data signals and generates
`appropriate control signals so that the combined data signal
`components are distributed and transmitted by antenna ele-
`ments 34. The transmitted radiation pattern, indicated gen-
`erally by reference numeral 36, includes various transmitted
`beams B1 to Bm which are received by receivers R1 to Rm.
`The receivers may be located at distant sites separated by
`thousands of kilometers or more. The receivers utilize the
`received signals to generate reconstructed signals D1' to Dm'.
`Referring now to FIG. 3, a block diagram illustrating a
`multiple-beam phased array antenna architecture utilizing
`polar digital beamforming (PDBF) is shown. This architec-
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`6O
`
`65
`
`4
`ture reduces the complexity required to implement DBF
`which results in a considerable reduction in power consump-
`tion compared to previous implementations, as explained in
`greater detail below.
`With continuing reference to FIG. 3, digital computer 40
`includes storage 42 in communication with microprocessor
`44. Storage 42 includes any of the well known storage media
`such as volatile and non—volatile memory, magnetic storage
`devices, internal storage registers, or the like. Storage 42
`contains a predetermined set of instructions executed by
`microprocessor 44 for performing various computations and
`comparisons to elfect the PDBF architecture of the present
`invention. Of course, the present invention may be imple-
`mented with various combinations of hardware and software
`as would be appreciate by one of ordinary skill in the art.
`As also illustrated in FIG. 3, computer 40 communicates
`via digital data communication lines 46 with subarrays S1 to
`S”. Typical communications include data streams or digi-
`tized modulation information, as well as beam pointing
`angles or complex weighting circuit values. Each subarray
`81 to Sn includes a subarray controller 48, a phasor 50, an
`attenuator 52, a power amplifier 54, and an antenna element
`56. Preferably, a digitally switched phasor and attenuator are
`utilized to implement phasor 50 and attenuator 52. Also
`preferably, the digitally switched phasors and attenuators are
`implemented with gallium arsenide (GaAs) field-effect tran—
`sistors (FET’s) due to their high-speed operation (modula-
`tion rates exceeding 1 GHz) and low drive power require-
`ments. However, several other implementations of phasors
`and attenuators are possible. For example, switched phasors
`and attenuators may be implemented with diodes and relays
`or analog phasors and attenuators controlled D/A converters
`may be used. These alternative implementations, however,
`require more power than the preferred implementation.
`With continuing reference to FIG. 3, each subarray con—
`troller 48 communicates with a corresponding phasor 50 and
`attenuator 52 via digital data communication paths 58.
`Digital data communication paths are indicated with a
`double line in the figures. A local oscillator 60 provides a
`carrier signal C(t) to power splitter 62 via RF communica—
`tion path 64, as indicated by a single line in the figures.
`In operation, carrier signal C(t) is split n ways by power
`splitter 62 while maintaining phase coherence of the signal.
`In the preferred embodiment, a distributed computing
`approach is utilized to determine the necessary complex
`subarray weights from data or modulation information and
`the desired pointing angles or weights for each beam. Thus,
`each subarray controller 48 determines a corresponding
`complex weighting value and switches its associated phasor
`50 and attenuator 52. Preferably, the subarray controllers are
`implemented with complementary metal—oxide semi-con-
`ductor (CMOS) gate arrays or programmable logic devices
`to minimize direct-current (DC) power consumption. Uti-
`lizing currently available CMOS devices, DC power levels
`of a few milliwatts per weighting circuit can be achieved.
`Thus, in the preferred embodiment, each subarray con-
`troller 48 is responsive to a baseband signal for beam in
`Snm(t) as well as azimuth and elevation information which
`is distributed to all the subarray controllers by computer 40.
`Each subarray controller then individually generates point—
`ing vectors PM, for an associated antenna element 56. The
`corresponding pointing vector is multiplied and summed
`with an associated baseband signal Sm“) to form a digital
`representation of Vn(t) as defined in Equation (6). This
`representation is converted to a polar representation having
`an amplitude A,,(t), and a phase 4),,(t) such that:
`
`ZTE, Exhibit 1014-0006
`
`ZTE, Exhibit 1014-0006
`
`

`

`5,541,607
`
`V..(t)=An(t)ee’¢'"“)
`
`(7)
`
`S
`
`Each subarray controller 48 then communicates a digital
`word representing the amplitude A,,(t)
`to an associated
`attenuator 52, and a digital word representing the phase mm
`to an associated phasor 50, to modulate the amplitude and
`phase of the RF carrier signal C(t). Thus, the baseband
`modulation information and the pointing information are
`impressed upon the carrier by the attenuators and phasors.
`Utilizing distributed processing to compute the complex
`subarray weights has two primary advantages. First, utiliz-
`ing n subarray controllers as a parallel processor simplifies
`the task of performing the required complex multiplications
`and additions needed every modulation change. This is
`extremely important since the total number of operations per
`second is significant. For example, for an application with
`only 10 beams, 1000 antenna elements, and a modulation
`symbol rate of 10 MHz, requires 1011 complex multiplica-
`tions each second. However, since there is one (1) subarray
`controller for each antenna element, each subarray controller
`must perform only 10" complex multiplications per second.
`The second advantage to a distributed processing archi-
`tecture is the reduction in the volume of high speed data
`which must be cormnunicated to the various element of the
`phased array since processing is done locally at each ele-
`ment. This reduction in volume contributes significantly to
`the reduced DC power consumption since high speed data
`lines require transmission line drivers which require sub-
`stantial DC power compared to other elements in the system.
`Using the previous example with 10 bits per symbol, a
`centralized processing architecture would require commu-
`nication of 10l2 bits per second (bps) from a central pro-
`cessor to each of the 1000 subarrays. Utilizing a distributed
`architecture as illustrated in FIG. 3 requires a communica—
`tion rate of only 109 bps between computer 40 and subarrays
`S1 to S".
`In an alternative embodiment, a centralized processing
`architecture is utilized which may be appropriate for par-
`ticular applications. In a centralized architecture, a central
`computer generates pointing vectors PM, for each antenna
`element, and multiplies and sums the PM, with the S,!m(t) to
`form the digital representation of Vn(t). The Vn(t) signal is
`then communicated to each subarray S1 to Sn which utilizes
`a simplified digital controller to control a digital attenuator
`and a digital phasor. However, this implementation requires
`significantly more DC power as described above.
`Referring now to FIG. 4, a functional block diagram
`illustrating the functions performed by each subarray con-
`troller 48 of FIG. 3 in implementing a general modulation
`scheme is shown. Components illustrated with phantom
`lines correspond to those components of FIG. 3 having like
`reference numerals. The modulation information Sm(t) is
`communicated by computer 40 to subarray controller 48 via
`digital communication path 46 and stored in storage regis-
`ters 70. Similarly, pointing weights for each of the m beams
`is stored in registers 72. Using this data, a pipelined multi-
`plier 74 forms M complex products which may be repre-
`sented by:
`
`Ym=5m(f)><Pm
`
`(8)
`
`A pipelined accumulator 76 sums the M complex products
`to produce the final complex weight represented by Vn(t)
`where:
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`Vn(t) = Z Yum
`m
`
`(9)
`
`65
`
`The multiplications performed by pipelined multiplier 74 are
`implemented utilizing a sequence of shifts and adds to
`
`6
`reduce the power consumption of the system.
`With continuing reference to FIG. 4, the complex weight
`Vn(t) is converted from a Cartesian representation to a polar
`attenuation An and phase ‘1’" utilizing an appropriate Look-up
`table 78. To correct for imperfections in the analog hard-
`ware, calibration oifsets Arm and 4)", are subtracted by
`subtracter 80. The corrected digital representations of the
`attenuation An and phase ‘1’" are communicated to attenuators
`50 and phasors 52, respectively, via digital communication
`paths 58.
`Rather than sending the beam pointing information as
`complex pointing weights PM, as illustrated in FIG. 4, this
`information may be sent to the subarrays as a pointing angle
`such as azimuth and elevation for each beam. When pointing
`angles are communicated, each subarray controller must
`compute the pointing weights by using an additional mul-
`tiplication process (not shown) similar to that previously
`described. Either method of communicating pointing infor-
`mation results in reduced data rates as compared to previous
`implementations. For example, given 10 pointing updates
`per second, 10 bits of information for each beam, and the
`additional parameters of the previous example, a commu-
`nication rate of 106 bps would be required to send complex
`pointing weights while a communication rate of 103 bps
`would be required to send pointing angles.
`Referring now to FIG. 5, a functional block diagram
`illustrating the functions performed by each subarray con-
`troller 48 of FIG. 3 for implementing a simplified modula-
`tion scheme is shown. In some applications, a further
`simplification may be made by utilizing digital bi-phase shift
`keyed (BPSK) modulation or digital quadra—phase shift
`keyed (QPSK) modulation. If a BPSK scheme is utilized, the
`original data may be communicated to the various subarray
`controllers utilizing 1 bit per symbol (2 bits per symbol for
`QPSK) so as to reduce the data rate by approximately a
`factor of 10 (factor of 5 for QPSK). The subarray controller
`48 generates the complex modulation from the input data.
`Subarray controller 48 receives an input data stream Sm(t)
`which is stored in storage registers 90. Similarly, complex
`pointing weights Pm are communicated to subarray con-
`troller 48 and are stored in storage registers 92. For both
`BPSK and QPSK modulation, the complex modulation is
`implemented at block 94 by reversing the sign of the real and
`imaginary components of the complex pointing weights.
`This reduces the complex multiplication operation to a
`simple sign reversal operation (i.e. inverting each signal
`component). Thus, the complexity of the subarray control-
`lers and the associated DC power consumption is also
`reduced by about a factor of 10. Utilizing BPSK or QPSK
`modulation, the DC power consumption of the entire PDBF
`array is about the same as that of an ABF implementation
`while providing a significant reduction in complexity,
`weight, and cost which is proportional to the number of
`beams rn. By sending the original data instead of the
`complex modulation, similar reductions in complexity may
`be obtained with other forms of digital modulation including
`16QAM and SPSK, among others.
`With continuing reference to FIG. 5, an accumulator 96
`forms the complex weight Vn(t) which is converted to a
`polar attenuation and phase by block 98. Calibration offsets
`are subtracted by block 100 to adjust for differences in the
`analog components of the attenuators and phasors. Block
`102 then communicates the corrected attenuation and phase
`information to an associated phasor and attenuator (not
`shown), respectively.
`Referring now to FIG. 6, a functional block diagram
`illustrating a simplified multiple-beam phased array antenna
`
`ZTE, Exhibit 1014-0007
`
`ZTE, Exhibit 1014-0007
`
`

`

`5,541,607
`
`7
`is shown. The antenna architecture illustrated in FIG. 6
`implements polar digital beamforrning utilizing phasors
`without attenuators. The system of FIG. 6 includes compo-
`nents indicated with primed reference numerals which func—
`tion in an analogous manner to those components of FIG. 3
`having corresponding unprimed reference numerals.
`With continuing reference to FIG. 6, each subarray con-
`troller 48‘ performs functions similar to those illustrated in
`FIG. 4 and FIG. 5 utilizing only the phase information. Thus,
`the complexity of the array is reduced even further by
`eliminating the attenuators. Eliminating attenuation infor-
`mation reduces the beam signal in the far field by about 1 to
`2 decibels (dB) while the side lobes of the beam are
`increased by a few dB. However, this implementation allows
`power amplifiers 56'
`to be operated at maximum power
`where they are most efficient in converting DC power into
`RF power. This increase in efliciency more than offsets the
`l to 2 dB loss in the transmitted beam signal.
`It should be understood,
`that while the forms of the
`invention herein shown and described include the best mode
`contemplated for carrying out the invention, they are not
`intended to illustrate all possible forms thereof. It should
`also be understood that the words used are descriptive rather
`than limiting, and that various changes may be made without
`departing from the spirit and scope of the invention dis—
`closed.
`What is claimed is:
`1. For use with a phased array antenna having a plurality
`of subarrays each including a phasor and an antenna ele-
`ment, a method for digital beamforrning of at least one
`independent transmit beam, the method comprising the steps
`of:
`
`generating a modulation signal representing information
`to be transmitted via the at least one independent
`transmit beam;
`generating a pointing signal representing a beam pointing
`direction for the at least one independent
`transmit
`beam:
`
`combining the modulation signal and the pointing signal
`to generate a weighting signal for each of the plurality
`of antenna elements;
`to a corresponding
`converting each weighting signal
`attenuation signal and a corresponding phase signal;
`controlling each of the plurality of phasors with its
`corresponding phase signal to modulate a carrier signal;
`and
`
`applying the modulated carrier signal to a corresponding
`antenna element so as to transmit the at least one
`independent transmit beam.
`2. The method of claim 1 wherein each of the plurality of
`subarrays further includes an attenuator, the method further
`comprising:
`controlling each of the plurality of attenuators with its
`corresponding attenuation signal to modulate the car-
`rier signal before performing the step of applying the
`modulated carrier signal to the corresponding antenna
`element.
`
`3. The method of claim 2 further comprising modifying
`each of the attenuation signals before the step of controlling
`the plurality of attenuators so as to adjust for dilIerences
`among the plurality of attenuators.
`4. The method of claim 3 wherein modifying each of the
`attenuation signals comprises subtracting a corresponding
`compensation value from each of the attenuation signals.
`5. The method of claim 1 wherein the step of combining
`the modulation signal and the pointing signal to generate a
`weighting signal comprises the steps of:
`
`10
`
`15
`
`20
`
`25
`
`30
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`35
`
`40
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`45
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`50
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`55
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`60
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`65
`
`8
`generating a plurality of complex products each repre-
`senting the modulation signal multiplied by a corre-
`sponding component of the pointing signal; and
`determining a complex sum of the plurality of complex
`products.
`6. The method of claim 1 further comprising modifying
`each of the phase signals before the step of controlling the
`plurality of phasors so as to adjust for difierences among the
`plurality of phasors.
`7. The method of claim 6 wherein modifying each of the
`phase signals comprises subtracting a corresponding com-
`pensation value from each of the phase signals.
`8. The method of claim 1 wherein the step of generating
`a pointing signal
`includes generating a pointing signal
`representing a plurality of complex pointing weights each
`having a real component and an imaginary component and
`wherein the step of combining the modulation signal and the
`pointing signal to generate a weighting signal comprises the
`steps of:
`inverting each of the plurality of real components and
`imaginary components; and
`determining a complex sum of the plurality of inverted
`real and imaginary components.
`9. For use with a phased array antenna having a plurality
`of subarrays each including a phasor and an antenna ele—
`ment, a system for digital beamforming of at least one
`independent transmit beam, the system comprising:
`means for generating a modulation signal representing
`information to be transmitted via the at
`least one
`independent transmit beam;
`means for generating a pointing signal representing a
`beam pointing direction for the at least one independent
`transmit beam;
`means for combining the modulation signal and the
`pointing signal to generate a weighting signal for each
`of the plurality of antenna elements;
`means for converting each weighting signal to a corre-
`sponding attenuation signal and a corresponding phase
`signal;
`means for controlling each of the plurality of phasors with
`its corresponding phase signal to modulate a carrier
`signal; and
`to a
`means for applying the modulated carrier signal
`corresponding antenna element so as to transmit the at
`least one independent transmit beam.
`10. The system of claim 9 wherein each of the plurality of
`subarrays further includes an attenuator, the system further
`comprising:
`means for controlling each of the plurality of attenuators
`with its corresponding attenuation signal to modulate
`the carrier signal.
`11. The system of claim 10 further comprising:
`means for modifying each of the attenuation signals so as
`to adjust for differences among the plurality of attenu—
`ators.
`12. The system of claim 11 wherein the means for
`modifying each of the attenuation signals comprises means
`for subtracting a corresponding compensation value from
`each of the attenuation signals.
`13. The system of claim 9 wherein the means for com—
`bining the modulation signal and the pointing signal to
`generate a weighting signal comprises:
`means for generating a plurality of complex products each
`representing the modulation signal multiplied by a
`corresponding component of the pointing signal; and
`
`ZTE, Exhibit 1014-0008
`
`ZTE, Exhibit 1014-0008
`
`

`

`5,541,607
`
`10
`independent transmit beam and a pointing direction
`therefor;
`
`9
`means for determining a complex sum of the plurality of
`complex products.
`14. The system of claim 9 further comprising means for
`modifying each of the phase signals so as to adjust for
`difl‘erences among the plurality of phasors.
`15. The system of claim 14 wherein the means for
`modifying each of the phase signals comprises means for
`subtracting a corresponding compensation value from each
`of the phase signals.
`16. The system of claim 9 wherein the means for gener-
`ating a pointing signal
`includes means for generating a
`pointing signal representing a plurality of complex pointing
`weights each having a real component and an imaginary
`component and wherein means for combining the modula-
`tion signal and the pointing signal to generate a weighting
`signal comprises:
`means for inverting each of the plurality of real compo-
`nents and imaginary components; and
`means for determining a complex sum of the plurality of
`inverted real and imaginary components.
`17. A system for digital beamforming of at least one
`independent transmit beam, the system comprising:
`a computer for generating a first digital signal represent-
`ing information to be transmitted by the at least one
`
`10
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`15
`
`20
`
`a plurality of subarray controllers in communication with
`the computer for generating a second digital signal
`having an attenuation component and a phase compo-
`nent, the second digital signal being based on the first
`digital signal;
`a plurality of phasors each in communication with a
`corresponding one of the plurality of subarray control-
`lers and responsive to the phase component of the
`second digital signal;
`means for distributing a carrier signal to each of the
`plurality of phasors for modulation thereby; and
`means for transmitting the modulated signal in commu—
`nication with each of the plurality of phasors.
`18. The system of claim 17 further comprising:
`a plurality of attenuators each in communication with a
`corresponding one of the plurality of subarray control-
`lers and responsive to the attenuation component of the
`second digital signal.
`*
`*
`
`*
`
`*
`
`*
`
`ZTE, Exhibit 1014-0009
`
`ZTE, Exhibit 1014-0009
`
`