JP2010530657A - Multi-antenna beamforming system for transmitting constant envelope signals decomposed from variable envelope signals - Google Patents

Abstract

  Embodiments in this disclosure relate to a multi-antenna beamforming system for transmitting a constant envelope signal decomposed from a variable envelope signal. The variable envelope signal is broken down into two constant envelope signals. Each constant envelope signal is separately amplified by a power amplifier and transmitted through a separate antenna. A beam steering delay can be added to the constant envelope signal transmission path to direct the beam to the receiver location. The transmitted constant envelope signals are combined through spatial outphasing so that the receiving antenna receives the variable envelope signal.

Description

BACKGROUND Constant envelope signals are a popular method for transmitting radio or airborne radio frequency (RF) signals. For a constant envelope signal, the carrier envelope does not change in response to changes in the modulation signal. In other words, the maximum and minimum amplitudes of a constant envelope signal are maintained at a constant level. Constant envelope signaling schemes are advantageous in that they are efficient in terms of transmit power. The reason is that the constant envelope signal allows the transmitter power amplifier to operate at or near the saturation level, which corresponds to the level at which the power amplifier operates at maximum efficiency. . Furthermore, due to the fact that the amplitude is maintained at a constant level, the power amplifier need only provide a stable amount of amplification. Thus, there is less nonlinearity and signal distortion associated with amplification of constant envelope signals.

  In contrast, a variable envelope signal has an envelope that changes over time. A variable envelope signal can transmit a larger amount of data with the same occupied frequency bandwidth over a given amount of time compared to a constant envelope signal. This results in improved spectral efficiency. Unfortunately, power amplifiers for amplifying variable envelope signals operate at average power levels that are significantly lower than their maximum power. This means that the power amplifier operates almost at a less than ideal level. This reduces the power efficiency of these variable envelope power amplifiers. Furthermore, power amplifiers for variable envelope signals change the amplitude of the signal by changing the amount, depending on the instantaneous amplitude of the signal. The greater the change in the amplitude of the signal, the greater the nonlinear amplification. This non-linear amplification results in distortion in the variable envelope signal and non-idealities in the channel. Such distortion and non-idealities can cause errors in the receiver. The received data can be corrupted and the transmitted distortion signal will experience spectral recovery.

  Therefore, wireless communication designers face a dilemma. The designer can achieve a constant envelope signal that is very efficient from a power point of view and is also less susceptible to distortion. However, the trade-off is that a constant envelope signal cannot transmit data as fast as a variable envelope signal. Variable envelope signals have better spectral efficiency, which is a reduction in power efficiency and increased sensitivity to signal distortion and non-idealities that can eventually lead to receiver errors and unacceptable out-of-band spectral emissions. Obtained at the expense.

  The accompanying drawings, which are incorporated in and form a part of this specification, illustrate the embodiments discussed below, and together with this description serve to explain the principles of the disclosure.

2 shows an example of a system for transmitting variable envelope signals as two constant envelope signals through two transmit antennas. FIG. 4 shows a vector diagram used to illustrate the decomposition process used to perform spatial outphasing. Fig. 5 shows a constellation for a transmitting antenna that transmits a constant envelope signal and a constellation for a receiving antenna that receives an equal variable envelope signal. Figure 5 shows a graph of output power and efficiency as a function of input power for a typical transmitter power amplifier. Fig. 2 shows a multi-antenna system with a number N of transmit antennas for transmitting a number N of constant envelope signals representing an initial variable envelope signal. Fig. 2 shows a phased array antenna system for transmitting a constant envelope signal decomposed from a variable envelope system. 6 is a flowchart illustrating steps for multi-antenna beam forming processing for transmitting a constant envelope signal decomposed from a variable envelope signal. FIG. 3 shows a system diagram for an embodiment in a multi-antenna system for transmitting a decomposed constant envelope signal. FIG. 3 shows a system diagram for an embodiment in a multi-antenna system for transmitting a decomposed constant envelope signal.

DETAILED DESCRIPTION Embodiments in this disclosure relate to a multi-antenna beamforming system. Initially, the variable envelope signal is decomposed into two constant envelope signals via a process known as outphasing. The outphasing process provides two signals of constant amplitude but variable phase (eg, “phasor fragments”) to represent a single signal of variable phase and amplitude. Each of the two constant envelope signals is amplified by a power amplifier and then transmitted wirelessly as an RF signal by a transmit antenna. Since the power amplifier amplifies the constant envelope signal, transmit power efficiency is achieved while any non-linearity associated with the power amplifier is minimized. Two constant envelope RF signals propagate in the air and are received by one or more receive antennas. The combination of two constant envelope RF signals received by one or more receive antennas produces a variable envelope signal that matches that of the initial variable envelope signal before being decomposed. The received variable envelope signal provides excellent spectral efficiency. Thereby, the advantages associated with constant and variable envelope signaling are realized, while their drawbacks are overcome. In one embodiment, a delay may be introduced into the transmission path of one or more antennas to help direct the transmitted signal to a specified receiver antenna location.

Referring now to FIG. 1, an example system for transmitting a variable envelope signal as two constant envelope signals through two transmit antennas is shown. The variable envelope signal X (t) varies in both amplitude and phase. The variable envelope signal X (t) is decomposed into two constant envelope signals _Xc1 and _Xc2 . This is accomplished by inputting the variable envelope signal X (t) to the two mixers 101 and 104. Mixer 101, by changing the phase of X (t) signal by phi _1, and generates a constant envelope signal Xc1. The constant envelope signal Xc1 has a constant amplitude, but its phase changes as a function of X (t). The constant envelope signal Xc1 is input to the power amplifier 102. The power amplifier 102 amplifies the constant envelope signal Xc 1, and then the constant envelope signal Xc 1 is wirelessly transmitted to the receiving antenna 107 as an RF signal by the antenna 103. In the same way, the mixer 104 changes the phase of the variable envelope signal X (t) by φ ₂ to generate a constant envelope signal Xc2. The constant envelope signal Xc2 has a constant amplitude, but its phase changes as a function of X (t). The constant envelope Xc2 signal is input to the power amplifier 105. The power amplifier 105 amplifies the constant envelope signal Xc2, and then the constant envelope signal Xc2 is transmitted by the antenna 106 to the receiving antenna 107 wirelessly as an RF signal. The two RF signals transmitted by the transmitting antennas 103 and 106 are combined by superposition in the air propagation, and the receiving antenna 107 receives a variable envelope signal corresponding to the original variable envelope signal X (t). This type of coupling in air propagation of at least two constant envelope signals to form a variable envelope signal is referred to herein as “spatial outphasing”.

  In this embodiment, it is not necessary to have a physical adder circuit that adds two constant envelope signals together before RF transmission. The constant envelope signals are amplified separately by separate power amplifiers, and each of the amplified constant envelope signals is transmitted wirelessly by their own dedicated antenna. In other embodiments, any number of phase delay circuits, mixers, amplifiers, converters, switches, and other components of different types and designs can be used to perform the decomposition process. Furthermore, no changes or modifications are necessary from the receiver side. This provides for a standard blind solution whereby a multi-antenna system for transmitting a constant envelope signal decomposed from a variable envelope signal operates for virtually any conventional receiving system.

  FIG. 2 shows a vector diagram used to illustrate the decomposition process used to perform spatial outphasing. Three vectors are shown. One vector represents the variable envelope signal X (t). The length of the X (t) vector represents the amplitude of the variable envelope signal. The angle of the X (t) vector represents the phase of the variable envelope signal. The amplitude and phase of the variable envelope signal can vary. Thus, the length and angle of the X (t) vector can vary. The X (t) vector can be decomposed into two vectors Xc1 and Xc2. The Xc1 and Xc2 vectors represent constant envelope signals. For a constant envelope signal, the amplitude does not change. The amplitude of the constant envelope signal is indicated by the length of the Xc1 and Xc2 vectors. Therefore, the lengths of the Xc1 and Xc2 vectors are kept constant. The angles of the Xc1 and Xc2 vectors represent their respective phases. By applying vector operations so that the result is an X (t) vector when the Xc1 vector is combined with the Xc2 vector, the angles (φ1 and φ2) for the Xc1 and Xc2 vectors can be calculated . Any change in the phase of the variable envelope signal is represented by a corresponding change in the angle of the X (t) vector. This means the following: That is, the angles φ1 and φ2 of the Xc1 and Xc2 vectors are changed in response to changes in the angle of the X (t) vector (eg, φ1 decreases while φ2 increases or φ1 Φ2 increases while decreasing). The lengths of the Xc1 and Xc2 vectors need not be changed and can be kept constant. Thus, a change in the phase of the variable envelope signal is represented by changing the phases of the two corresponding constant envelope signals.

  Any change in the amplitude of the variable envelope signal is represented by a corresponding change in the length of the X (t) vector. This in turn changes the angle of the constant envelope accordingly, as represented by the angles of the Xc1 and Xc2 vectors. For example, if the amplitude of the variable envelope signal decreases, this would be represented by a shorter X (t) vector. The shorter X (t) vector decomposition involves changing the angles φ1 and φ2 of the Xc1 and Xc2 vectors. In particular, the angles φ1 and φ2 are increased when the length of the X (t) signal decreases. The lengths of the Xc1 and Xc2 vectors cannot be shortened because they represent a constant envelope signal with a constant amplitude. Conversely, when the amplitude of the variable envelope signal increases, the angles φ1 and φ2 of the constant envelope vectors Xc1 and Xc2 are decreased. Thus, any change in the amplitude of the variable envelope signal is represented by changing the phase of the two corresponding constant envelope signals. Thus, a change in the amplitude or phase of the variable envelope signal is represented by changing the phase of the resolved pair of constant envelope signals. Additional explanations of decomposition and outphasing can be found in Behzad Razavi, RF Microelectronics, Prentice Hall PTR, November 6, 1997 (see Section 9.5.4 relating to "linear amplification with nonlinear components" (LINC)).

  The transmitting antenna transmits a constant envelope signal, while the receiving antenna receives a variable envelope signal. This is illustrated in FIG. 3, which shows a constellation for the transmit antenna and a constellation for the receive antenna. The constellation for one of the two transmit antennas is shown as 301. The symbols are placed equidistant from the center, which indicates that a constant envelope signal having a constant amplitude is being transmitted. The phase of the constant envelope signal can vary as indicated by the various symbols located along the same radius R1 in the constellation. The constellation for the other transmit antenna is shown as 302. The constellation 302 has a constant radius R2. In one embodiment, R1 = R2. In other embodiments, R1 and R2 can be different. The symbols of constellation 302 are arranged equidistant from the center by radius R2. This indicates that a constant envelope signal having a constant amplitude but changing phase is being transmitted by the other transmit antenna.

  A constellation for the receiving antenna is shown as 303. The constellation 403 places symbols along circles with different radii (R3, R4 and R5). Different radii indicate that the amplitude of the received signal changes over time. Furthermore, the symbols are arranged along various points of the circle. This means that the phase of the received signal also changes over time. Thus, constellation 303 represents the received variable envelope signal. The two transmitted signals having constellations 301 and 302 are combined in the air through a process referred to herein as spatial outphasing and leads to an antenna that receives a signal corresponding to constellation 303 that characterizes the variable envelope signal. Thus, a higher data rate (eg, larger bits / second) is received by the receive antenna compared to a receiver that simply receives a constant envelope signal. Furthermore, since the transmitter power amplifier amplifies a constant envelope signal rather than a variable envelope signal, the nonlinearity of the power amplifier is minimized. Therefore, the reception constellation 303 is uniform and reception errors are minimized. Note that because the transmitter power amplifiers are amplifying constant envelope signals (ie, Xc1 and Xc2), these amplifiers can operate at or near their saturation levels. This means that the transmitter power amplifiers are operating at or near their maximum efficiency. FIG. 4 shows a graph of output power and efficiency as a function of input power for a typical transmitter power amplifier. For a constant envelope signal, the amplitude is constant. Thus, the average power for a constant envelope signal is approximately equal to its maximum power. This corresponds to higher efficiency. Conversely, since the amplitude of the variable envelope signal changes over time, its average power is less than that of its maximum power. Its average power falls from its peak. This results in lower power efficiency. For a typical power amplifier, the efficiency for a variable envelope signal can be 5%, whereas the typical efficiency for a constant envelope signal can be 50%. Thus, by decomposing a variable envelope signal into a constant envelope signal, embodiments of the present disclosure can improve power amplifier efficiency by a factor of 10 or more.

In other embodiments, more than two transmit antennas are used. In one embodiment, the variable envelope signal is decomposed into three or more constant envelope signals, each of which is separately amplified by a power amplifier and transmitted wirelessly as an RF signal by a transmit antenna. FIG. 5 shows a multi-antenna system having a number N of transmit antennas for transmitting a number N of constant envelope signals representing the initial variable envelope signal. The initial variable envelope signal X (t) is simultaneously input to several N mixers. The number N of mixers independently changes the phase by φ ₁ to φ _n . The outputs from the mixer are a number N of constant envelope signals X _{c1 to} X _cN . Each constant envelope signals of the number N is amplified by the number N of the power amplifier PA ₁ ~PA _N, then transmitted as an RF signal by the number N of antennas. There may be cost, power, signal integrity and / or bandwidth reasons for the decomposition and out-of-fading of more than two constant envelope signals.

The multi-antenna system of the above embodiment can be applied to an environment where the receiving antenna is equidistant from each of the transmitting antennas. If one or more of the transmit antennas are located further away from the receive antenna than the other transmit antennas, the constant envelope signal corresponding to the transmit antenna (s) located further away will reach the receive antenna Will take longer. This additional delay can cause errors in phase. One solution is to introduce additional delay (s) into the transmission path (s) corresponding to the closer transmit antenna (s) so that their constant envelope signal is further reduced by the constant envelope signal of the further transmit antenna. Synchronize with it and try to reach it “on time” together. For example, if there are two transmit antennas where one transmit antenna is driven by X _c1 (t) and the other transmit antenna is driven by X _c2 (t), the sum at the receive antenna is 2 It is accurate if the delay from the transmit antenna is the same. This occurs at one angle. However, the transmitted signal can be directed to any desired angle. This can be achieved by adjusting the delay of one transmitted constant envelope signal. The delay can be adjusted by feedback from the receiver to the transmitter. For example, X _c2 (t) can be kept constant in amplitude while its phase is adjusted. The phase adjustment can direct the transmitted signal to any desired angle according to the following equation:
X _TX1 (t) = X _C1 (t)
X _TX2 (t) = X _C2 (t-delay (θ))
X _RX (t) = X _C1 (t) + X _C2 (t) = X (t)

  In one embodiment, a phased array antenna system is used to transmit a decomposed and out-faded constant envelope signal. Typically, a phased array antenna system transmits multiple RF signals using multiple antennas. By incrementally adding delays to the individual transmit paths for each successive antenna, the phased array antenna system can direct or direct the beam to a specific location on the receive antenna. This beam forming function is desirable for security reasons. Furthermore, directivity is advantageous. This is because more RF power can be directed to the receiving antenna, which increases the distance over which data can be reliably transmitted. You can have such a transmitter with feedback from the receiver. The receiver location information is fed back to the transmitter, allowing the transmitter to adjust the delay to compensate for the receiver location. Feedback of the receiver position is performed for mobile or portable receiver applications. Alternatively, if the transmitter and receiver positions are fixed, the delay can be calculated based on the fixed position and stored in the memory of the transmitter system. The location information can also be input from the user or downloaded from the network. Embodiments of the present disclosure can be applied to a phased array antenna system.

For example, FIG. 6 shows a phased array antenna system for transmitting a constant envelope signal decomposed from a variable envelope system. The variable envelope signal X (t) is input to the constant envelope decomposition block 601. The constant envelope decomposition block 601 decomposes the variable envelope signal X (t) into two constant envelope signals X _C1 and X _C2 according to the outphasing decomposition process described in detail above. After constant envelope decomposition, beam steering delays are introduced into the X _C1 and X _C2 signal paths, after which they are amplified by a power amplifier. More specifically, one of the X _C1 signal paths 602 does not have any additional beam steering delay. The X _C1 signal is input to the power amplifier 606. Power amplifier 606 amplifies the X _C1 signal for RF transmission by transmit antenna 610. The X _C1 signal is also transmitted through an additional number N of transmission paths in the phased array antenna system. An additional beam steering delay is added to each of the number N of X _C1 paths. The beam steering delay increases incrementally for each successive _XC1 transmission path. Last transmission path 604 of the X _C1 signal has an additional beam steering delay of φ _2N-2. The X _C1 signal with φ _2N−2 additional beam steering delay is amplified by power amplifier 608 and then transmitted as RF signal by antenna 612. In one embodiment, a Δ delay is incorporated into the phase (eg, φ ₁ -φ _2N-2 ).

For the _XC2 signal, one of the transmission paths 603 has an additional beam steering delay of φ1. X _C2 signal having an additional beam steering delay φ1 is input to the power amplifier 607, power amplifier 607 amplifies the signal, then the signal is transmitted wirelessly by the antenna 611. _XC2 signals are also transmitted on an additional number N of transmission paths in the phased array antenna system. An additional beam steering delay is added for each of a number N of _XC2 paths. The beam steering delay increases incrementally for each successive _XC2 transmission path. X _C2 signal of the last transmit path 605 includes an additional beam steering delay of φ _{2N-1. X C2} signal with additional beam steering delay phi _2N-1 is amplified by the power amplifier 609, then transmitted as an RF signal by the antenna 613.

  A phased array antenna system can have multiple transmit paths, power amplifiers, and transmit antennas for transmitting constant envelope signals. However, for purposes of illustration and description, only four multiple transmission paths, power amplifiers and transmit antennas are shown in detail in FIG. By increasing the number of transmission paths, power amplifiers and transmission antennas in the phased array antenna system, its gain is increased, thereby extending its transmission range. By selectively controlling the beam steering delay, the beam can be directed to any position corresponding to the receiving antenna. In other words, the beam can be electronically directed to the receiving antenna.

  FIG. 7 is a flowchart illustrating the steps of a multi-antenna beam forming process for transmitting a constant envelope signal decomposed from a variable envelope signal. First, in step 701, a variable envelope signal is generated. In step 702, the variable envelope signal is decomposed into at least two constant envelope signals. The amplitude of the constant envelope signal is kept constant, but their phase varies depending on the amplitude and phase of the variable envelope signal. In step 703, one or more delays are added to one or more transmit signal paths corresponding to one or both of the constant envelope signals. Step 703 is optional and is used to direct the beam to a known location of the receiving antenna. For implementation in a phased array antenna system, the delay is continuously timed relative to continuous antennas. In step 704, once a delay (if any) is added, each of the transmission paths associated with the constant envelope signal is amplified by a separate power amplifier. The amplified constant envelope signal is then transmitted as a RF signal from a separate antenna in step 705. Since the decomposition works exactly for one angle, the transmitter needs to know the position of the receiver and based on this it must compensate in advance. Therefore, feedback from the receiver to the transmitter is performed. This feedback is shown in steps 706 and 707. In step 706, the receiver estimates the angle at which it is located relative to the transmitter. In step 707, the receiver sends angle information back to the transmitter.

  8A and B show system diagrams for an embodiment of a multi-antenna system for transmitting a decomposed constant envelope signal. The multi-antenna system 802 can transmit and receive data from the network 801 (eg, the Internet) via the I / O interface 803. The I / O interface 803 is also coupled to a user interface 810 that allows a user to enter data and commands into the multi-antenna system 802 and also display data from the multi-antenna system 802. You will be able to get Any data designated for transmission by the transmitter 806 is initially processed as a variable envelope signal. Data can be input from a user via UI 810, obtained via network 801, read from memory 805, or generated as generated by processor 804. The variable envelope signal is then processed by an out-fading decomposition block 807, which outputs a constant envelope signal. For beam steering, at block 808, a delay is added to several signals of the constant envelope signal. The constant envelope signal is then amplified by a power amplifier at block 809. The amplified constant envelope signal is directed to one or more receive antennas and transmitted wirelessly. An example of a receiving system is shown as 811. The receiving system 811 has a receiver 812, which is designed to receive and demodulate a variable envelope signal. The processor 813 processes the received data. The data can then be stored in memory 814, transmitted via I / O interface 815 for display or playback at user interface 817, or transmitted over network 816. Further, the processor 813 of the receiving station 811 can send the position information back to the transmitter 806 of the multi-antenna system 802. This position information is used to adjust the delay of delay circuit 808 to compensate for the position of receiving system 811. This information can be transmitted back over the air, especially for mobile or portable receiver applications. Alternatively, the location information can be entered by the user, stored in memory, or downloaded from a network or server.

  In one embodiment, the multi-antenna system directly generates a constant envelope signal without having to actually generate any variable envelope signal. A constant envelope signal is modeled after an imaginary or virtual variable envelope signal. Note that this system supports any type of point-to-point or multicast data communication. The distance between the transmitter and the receiver can be as short as 10 times the distance between the transmit antennas and can be as far away as is actually supported by the power amplifier and multiple antennas. Any type of variable envelope signal (eg, differential quadrature phase shift keying, spread spectrum signal, etc.) and any type of constant or nearly constant envelope signal (eg, frequency shift keying, quadrature frequency division multiplexing, etc.) It can be used in various embodiments of multi-antenna systems. Furthermore, multi-antenna systems are not limited by frequency. It can work in any frequency range. In addition, the multi-antenna system can be used in a wide variety of applications (eg, as a repeater for transmitting high-definition television signals, high-speed digital data links, audio / voice / mobile communications, etc.). .

  In conclusion, a multi-antenna beamforming system for transmitting a constant envelope signal decomposed from a variable envelope signal is disclosed. In the foregoing specification, embodiments of claimed subject matter have been described with reference to numerous specific details that may vary from implementation to implementation. Accordingly, the only and exclusive indication of what is claimed subject matter and what is intended by the applicant to be claimed subject matter is the set of claims originating from this application, including any subsequent amendments A set of claims in a specific form from which such claims originate. Thus, no limitation, element, property, feature, advantage or attribute that is not expressly recited in a claim should limit the scope of such claim in any way. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

Claims (21)

A circuit for decomposing the variable envelope signal into at least a first constant envelope signal and a second constant envelope signal;
A first amplifier coupled to the circuit for decomposing the variable envelope signal, the first amplifier amplifying the first constant envelope signal;
A first antenna coupled to the first amplifier for transmitting an amplified first constant envelope signal;
A second amplifier coupled to the circuit for decomposing the variable envelope signal, the second amplifier amplifying the second constant envelope signal;
A second antenna coupled to the second amplifier for transmitting an amplified second constant envelope signal;
Including a transmission circuit.   And further including at least one delay circuit for delaying the second constant envelope signal by a specified amount of time so that a variable envelope signal results from the superposition of the first and second envelope signals at the position of the receiving antenna. The transmission circuit according to claim 1.   3. The transmission circuit of claim 2, wherein the delay circuit includes at least one mixer that adds a phase delay to a transmission path in one of the first constant envelope signal and the second constant envelope signal. At least three delay circuits for delaying the first constant envelope signal and the second constant envelope signal to direct a beam to the position of the receiving antenna;
At least four amplifiers for amplifying the first constant envelope signal and the second constant envelope signal;
The transmission circuit according to claim 1, further comprising at least four antennas for transmitting the first constant envelope signal and the second constant envelope signal.   The transmission of claim 1, wherein the first constant envelope signal and the second constant envelope signal have a phase that causes a receiving antenna to receive the variable envelope signal when transmitted as an RF signal. circuit.   The transmission circuit according to claim 1, wherein the first amplifier and the second amplifier include a power amplifier operating in a saturated state. A method for transmitting an RF signal comprising:
Generating a first signal having a constant amplitude and a variable phase;
Amplifying the first signal;
Transmitting the first signal wirelessly;
Generating a second signal having a constant amplitude and a variable phase;
Amplifying the second signal;
Transmitting the second signal wirelessly;
Including
The method wherein the first signal and the second signal are decomposed from a third signal having a variable amplitude and a variable phase.   The method of claim 7, further comprising adding a delay to the second signal, the delay being added to transmit the first signal and the second signal to a known location of a receiver. Method.   8. The method of claim 7, further comprising adding a plurality of delays to a plurality of transmission paths for transmitting the first signal and the second signal in a phased array antenna system. Amplifying the first signal in a saturated state of the first power amplifier;
Amplifying the second signal in a saturated state of a second power amplifier;
The method of claim 7, further comprising:   Spatially outphasing the third signal, wherein the first signal and the second signal are wireless such that the receiver receives a wireless signal with variable amplitude and variable phase. The method of claim 7, wherein A method for transmitting a signal wirelessly, comprising:
Decomposing the variable envelope signal into a first constant envelope signal and a second constant envelope signal;
Amplifying the first constant envelope signal;
Wirelessly transmitting the amplified first constant envelope signal through the first antenna;
Amplifying the second constant envelope signal;
Wirelessly transmitting the amplified second constant envelope signal through a second antenna;
Including methods.   The method of claim 12, further comprising adding a beam steering delay to direct the beam to the position of the receiving antenna.   Spatially outphasing the variable envelope signal, wherein the first constant envelope signal and the second constant envelope signal generate an RF signal to generate an RF signal corresponding to the variable envelope signal. The method of claim 12, wherein the coupling is via superposition. A multi-antenna system for transmitting a constant envelope signal decomposed from a variable envelope signal,
A processor for generating the variable envelope signal having variable amplitude and variable phase;
An outphasing decomposition circuit coupled to the processor for generating at least a first constant envelope signal and a second constant envelope signal, wherein the first constant envelope signal and the second constant envelope signal are An outphasing decomposition circuit having a constant amplitude and a variable phase that together represent a variable envelope signal;
A first power amplifier coupled to the out-phasing decomposition circuit for amplifying the first constant envelope signal;
A first antenna coupled to the first power amplifier for wireless transmission of the first constant envelope signal;
A second power amplifier coupled to the out-phasing decomposition circuit for amplifying the second constant envelope signal;
A second antenna coupled to the second power amplifier for wireless transmission of the second constant envelope signal;
Including multi-antenna system. A plurality of delay circuits coupled to the out-fading decomposition circuit for adding a beam steering delay to a transmission path of the first constant envelope signal and the second constant envelope signal;
A plurality of power amplifiers coupled to the plurality of delay circuits for amplifying the delayed first constant envelope signal and the delayed second constant envelope signal;
A plurality of antennas for wireless transmission of amplified and delayed first constant envelope signal and second constant envelope signal;
The multi-antenna system according to claim 15, further comprising:   The multi-antenna system according to claim 16, wherein the plurality of delay circuits include a plurality of adders for adding the delay to the first constant envelope signal and the second constant envelope signal.   The multi-antenna system of claim 16, wherein the plurality of delay circuits, a plurality of power amplifiers, and a plurality of antennas comprise a phased array antenna system that electronically directs a beam to a receiver location.   The multi-antenna system of claim 15, wherein the wireless transmission of the first constant envelope signal and the wireless transmission of the second constant envelope signal are combined as an RF signal.   The multi-antenna system of claim 15, wherein the wireless transmission of the first constant envelope signal and the wireless transmission of the second constant envelope signal can be received by a variable envelope signal receiver.   16. The multi-antenna system of claim 15, wherein the wireless transmission of the first constant envelope signal and the wireless transmission of the second constant envelope signal establish point-to-point communication with a receiver.

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