Patent Description:
With the demand for fast and reliable RF communications and the ever increasing amount of information contained in such RF communications, it is important to use the available frequencies and RF spectra as efficiently as possible However, the available frequencies are crowded with information and are often subject to significant interference.

Interference between various RF signals can be reduced by separating them as possible in time, space, or frequency. In some cases, such separation can also reduce or otherwise limit the amount of information that can be transmitted between a transmitter and a receiver over the available bandwidth. This can lead to diminished efficiency in data transmissions over a given communication system. United States patent application <CIT> discloses an exemplary method for demodulation of multiple received signals.

In general, this disclosure describes systems and methods related to interference reduction and signal protection in radio communications. The systems, methods and devices of this disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein.

Other features and advantages of the present disclosure should be apparent from the following description which illustrates, by way of example, aspects of the disclosure.

The details of embodiments of the present disclosure, both as to their structure and operation, may be gleaned in part by study of the accompanying drawings, in which like reference numerals refer to like parts, and in which:.

The details of embodiments of the present invention, both as to their structure and operation, may be gleaned in part by study of the accompanying drawings, in which like reference numerals refer to like parts, and in which:.

The detailed description set forth below, in connection with the accompanying drawings, is intended as a description of various embodiments and is not intended to represent the only embodiments in which the disclosure may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the embodiments. However, it will be apparent to those skilled in the art that the disclosure without these specific details. In some instances, well-known structures and components are shown in simplified form for brevity of description.

Separating signals in frequency or physical distance to minimize or reduce interference may decrease the amount of information that can be transmitted via a given communication channel or medium. If an interfering signal is received from an unknown or hostile source, separating signals in these ways may not be possible as little or no information about the interfering signal may be available.

Further, if the interfering signal is from an unknown or hostile source, when little or no information about the signal is known, separating signals in these ways may not be possible. Thus, reuse of bandwidth over multiple signals or overlapping transmitted signals in frequency may provide efficient use of available frequency spectra.

In some embodiments disclosed herein, certain demodulation techniques may have applications in multiple different communications systems including, but not limited to satellite communications signals and satellite command and control (C2) links, unmanned aerial vehicle (UAV) line of sight (LOS) and satellite data links, shipboard microwave and satellite communications systems, microwave communications links, GPS receivers, cellular phone communications links, cable signals, and other point-to-point or point-to-multi-point radio frequency (RF) systems that are susceptible to accidental or intentional interference. The methods and systems disclosed herein can also be used to allow blind dual-carrier signal processing to provide increased capacity for significantly higher data rates over a satellite transponder or other fixed RF bandwidth link than single carrier transmission.

<FIG> is graphical depiction of an embodiment of satellite communications between a plurality of ground stations. A communication system ("system") <NUM> depicts a plurality of ground stations <NUM>, <NUM>, <NUM> communicating with one another via a satellite <NUM>. In some embodiments, the communication system <NUM> may comprise more than three ground stations <NUM>, <NUM>, <NUM> and more than one satellite <NUM>.

Some systems may depend upon local copies of the outgoing signals for echo cancelation for interference reduction. In some systems a balanced approach to point-to-point or point-to-multipoint satellite communications may require certain signal processing at both ends of a communications link (e.g., a transmitter-receiver pair). In other systems another, an unbalanced approach may require signal processing only at one site. The communication system <NUM> of <FIG> is an example of an unbalanced approach in which the ground station <NUM>, for example, does not have a local copy of transmitted signals, as described below.

The ground station <NUM> may transmit a signal <NUM> (T1) to the satellite <NUM> that is then relayed to the ground stations <NUM>, <NUM>. The ground station <NUM> may transmit a signal <NUM> (T2) to the satellite <NUM> that is relayed to the ground station <NUM> and the ground station <NUM>. The ground station <NUM> may receive the signal <NUM> (T2) and an echo of its own transmitted signal <NUM> (T1) as a composite signal <NUM> (shown as, S1 + S2). Similarly, the ground station <NUM> may receive the signal <NUM> (T1) and an echo of its own transmitted signal <NUM> (T2) as a composite signal <NUM> (shown as, S1 + S2). As used in <FIG>, the "T" indicates a transmitted signal while the "S" indicates a corresponding signal received at one or more of the ground stations <NUM>, <NUM>, <NUM>. The "S1" and "S2" may also refer to constituent signals of a composite signal (e.g., the composite signals <NUM>, <NUM>, <NUM>).

In some embodiments, both of the ground stations <NUM>, <NUM> may have a local copy of the transmitted signals <NUM>, <NUM> to use in echo cancellation. In some cases, the removal of the self-interfering transmitted signal is accomplished using a process such as echo cancellation. In such an embodiment, the "echo" may be provided by sampling the transmit signal <NUM>, <NUM>, processing this signal through a delay line (not shown), matching phase and gain of the incoming composite signal <NUM>, <NUM> and cancelling the transmitted signal within the downlink signal to extract the additional signal within the processed frequency space. The echo cancelation may provide certain levels of interference reduction within the communication system <NUM> such that they may be able to receive and successfully demodulate the signal <NUM> and the signal <NUM> respectively.

The ground station <NUM> on the other hand does not transmit a signal of its own and thus may not have any significant echo cancelation capabilities for reception and processing of the signal <NUM> (S1) and the signal <NUM> (S2). The signal <NUM> (S1) and the signal <NUM> (S2) together, as received by the ground station <NUM>, is designated composite signal <NUM>. The composite signal <NUM> may be similar to the composite signal <NUM> and the composite signal <NUM>, being a combination of two signals, S1 + S2. In some embodiments, either or both of the signal <NUM> and the signal <NUM> can be signals of interest for the ground station <NUM>.

The composite signal <NUM> may however be subject to different forms and levels of interference due to different operating environments. In some embodiments the composite signals <NUM>, <NUM>, <NUM> may further include varying amounts of interference in addition to echo interference. In other embodiments, the one or more signals <NUM>, <NUM> found within the composite signals <NUM>, <NUM>, <NUM> may also be referred to herein as constituent signals. Thus, for example, the signal <NUM> and the signal <NUM> may be referred to as constituent signals of the composite signal <NUM>. Two modulated signals transmitted together may also be considered an additional modulation.

In some embodiments, a signal of interest (e.g., the signal <NUM> and/or the signal <NUM>) can be canceled from the composite signal <NUM>, for example, leaving a noise floor. The noise floor as used herein may generally refer to the measure of the signal created or regenerated from the sum of all the noise sources and unwanted signals within a measurement system, where noise is defined as any signal other than the signal or signals being monitored. The noise floor can describe a residual signal or remaining noise after the signal of interest (e.g., the signal <NUM>, <NUM>) is removed from the composite signal <NUM>. The noise floor can then be characterized using the interference mitigation or the interference removal methods described herein (described below in connection with <FIG>) to create a canceling signal.

In some embodiments, the noise floor may not be characterized. Accordingly, the canceling signal that has been created can be combined in a feed-forward loop with a copy of the composite signal, while compensating for frequency and amplitude variations, to reduce the noise floor. This may result in a higher signal-to-noise (SNR) ratio for the signal of interest. This can increase the potential data throughput of the signal by allowing the use of higher-order modulation schemes, and thus increase the throughput of the entire satellite <NUM>.

In some embodiments, in order to maximize the use of the available frequency spectra, the signal <NUM> and the signal <NUM> may use the same or similar bandwidth. In some embodiments, the signal <NUM> and the signal <NUM> may have the same amplitude. In some other embodiments, the signal <NUM> and the signal <NUM> may differ slightly in one or more of bandwidth, phase, and amplitude. Accordingly, the ground stations <NUM>, <NUM> may accidentally or intentionally utilize similar frequencies, bandwidths, and power levels (e.g., amplitude) to transmit their respective signals (T1, T2) for example, the signal <NUM> and the signal <NUM>. Thus, the ground station <NUM> may receive the signal <NUM> and the signal <NUM> having a significant or complete frequency overlap between the received signals. In some embodiments, there may be more than two overlapped signals, as described below in connection with <FIG>. The overlap of two or more signals of interest may present the ground station <NUM> with certain problems requiring separation and parsing of overlapped and possibly interfering signals, for example the signal <NUM>, and the signal <NUM>.

Modulation as described herein may include, but not be limited to analog or digital modulation. Some of the modulation schemes referenced herein can include but not be limited to quadrature amplitude modulation (QAM), phase shift keying (PSK), binary PSK (BPSK), quadrature PSK (QPSK), differential PSK (DPSK), differential QPSK (DQPSK), amplitude and phase shift keying (APSK), offset QPSK (OQPSK), amplitude shift keying (ASK), minimum-shift keying (MSK), Gaussian MSK (GMSK) among other types of modulation, time division multiple access (TDMA), code division multiple access (CDMA), orthogonal frequency division multiple access (OFDMA), and continuous phase modulation (CPM). Certain modulation types such as for example QAM and APSK may also differ in modulus, for example, 4QAM, 8QAM, and 16APSK, to name a few.

<FIG> is a functional block diagram of components of a communication device that may be employed within the communication system of <FIG>. As shown, communication device <NUM> may be implemented as the ground stations of <FIG>. For example the communication device <NUM> may comprise the ground station <NUM>.

The communication device ("device") <NUM> may include a processor <NUM> which controls operation of the communication device <NUM>. The processor <NUM> may also be referred to as a central processing unit (CPU). The communication device <NUM> may further include a memory <NUM> operably connected to the processor <NUM>, which may include both read-only memory (ROM) and random access memory (RAM), providing instructions and data to the processor <NUM>. A portion of the memory <NUM> may also include non-volatile random access memory (NVRAM). The instructions in the memory <NUM> may be executable to implement the methods described herein.

When the communication device <NUM> is implemented or used as a receiving node or ground station, the processor <NUM> may be configured to process information from of a plurality of different signal types. In such an embodiment, the communication device <NUM> may be implemented as the ground station <NUM> and configured to receive and parse or separate the composite signal <NUM> into its constituent signals (e.g., the signal <NUM> and the signal <NUM>). For example, the processor <NUM> may be configured to determine the frequency, bandwidth, modulation type, shaping factor, and symbol trajectory, among other transmission characteristics in order to recreate or regenerate the signals <NUM>, <NUM>. The processor <NUM> may implement various processes or methods in certain signal separation and interference reduction modules ("modules") <NUM> to effect such determinations. The modules <NUM> may also include the adaptive regenerative technology (ART) described in connection with <FIG>, below.

The processor <NUM> may further include one or more adaptive equalizers (not shown). The adaptive equalizers may be configured to estimate and characterize incoming signals in the time domain.

The processor <NUM> may comprise or be a component of a processing system implemented with one or more processors <NUM>. The one or more processors <NUM> may be implemented with any combination of general-purpose microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate array (FPGAs), programmable logic devices (PLDs), controllers, state machines, gated logic, discrete hardware components, dedicated hardware finite state machines, or any other suitable entities that can perform calculations or other manipulations of information.

The processor <NUM> may also include machine-readable media for storing software. Software shall be construed broadly to mean any type of instructions, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Instructions may include code (e.g., in source code format, binary code format, executable code format, or any other suitable format of code). The instructions, when executed by the one or more processors <NUM>, cause the processing system to perform the various functions described herein.

The communication device <NUM> may also include a housing <NUM> that may include a transmitter <NUM> and a receiver <NUM> to allow transmission and reception of data between the communication device <NUM> and a remote location. For example, such communications may occur between the ground stations <NUM>, <NUM>, <NUM>. The transmitter <NUM> and receiver <NUM> may be combined into a transceiver <NUM>. An antenna <NUM> may be attached to the housing <NUM> and electrically coupled to the transceiver <NUM>, or to the transmitter <NUM> and the receiver <NUM> independently. The communication device <NUM> may also include (not shown) multiple transmitters, multiple receivers, multiple transceivers, and/or multiple antennas.

The communication device <NUM> may also include a signal detector <NUM> that may be used in an effort to detect and quantify the level of signals received by the transceiver <NUM>. The signal detector <NUM> may detect such signal characteristics as frequency, bandwidth, symbol rate, total energy, energy per symbol, power spectral density and other signal characteristics. The signal detector <NUM> may also be include a "windowing module," (described in <FIG>) and may further be configured to process incoming data (e.g., one or more signals <NUM>, <NUM>) ensuring that the processor <NUM> is receiving a correct bandwidth-limited portion of a wireless communication spectrum in use. As a non-limiting example, certain transmissions to and from a ground station <NUM>, <NUM> can incur certain time and frequency variations by the time the transmissions are received at the satellite <NUM> and rerouted to the ground station <NUM>. Such variations may be due to Doppler shift and distance traveled, among other factors. Accordingly, the signal detector <NUM> (or windowing module) may correct the incoming signal(s) <NUM> for bandwidth and center frequency to ensure the processor <NUM> received the correct portion of the spectrum including the signal(s) <NUM>, <NUM>, <NUM>.

The communication device <NUM> may also include a digital signal processor (DSP) <NUM> for use in processing signals. The DSP <NUM> may be configured to generate a data unit for transmission. The DSP <NUM> may further cooperate with the signal detector <NUM> and the processor <NUM> to determine certain characteristics of the composite signal <NUM>.

The communication device <NUM> may further comprise a user interface <NUM> in some aspects. The user interface <NUM> may comprise a keypad, a microphone, a speaker, and/or a display. The user interface <NUM> may include any element or component that conveys information to a user of the communication device <NUM> and/or receives input from the user.

The various components of the communication device <NUM> described herein may be coupled together by a bus system <NUM>. The bus system <NUM> may include a data bus, for example, as well as a power bus, a control signal bus, and a status signal bus in addition to the data bus. Those of skill in the art will appreciate the components of the communication device <NUM> may be coupled together or accept or provide inputs to each other using some other mechanism.

Although a number of separate components are illustrated in <FIG>, one or more of the components may be combined or commonly implemented. For example, the processor <NUM> may be used to implement not only the functionality described above with respect to the processor <NUM>, but also to implement the functionality described above with respect to the signal detector <NUM> and/or the DSP <NUM>. Further, each of the components illustrated in <FIG> may be implemented using a plurality of separate elements. Furthermore, the processor <NUM> may be used to implement any of the components, modules, circuits, or the like described below, or each may be implemented using a plurality of separate elements.

<FIG> is a functional block diagram of a signal demodulator ("demodulator"). A demodulator <NUM> can receive a raw signal <NUM> a portion of which can include one or more signals of interest. For example, the ground station <NUM> may receive the raw signal <NUM> including the composite signal <NUM>, which, as noted above, can have multiple constituent signals <NUM>, <NUM>. The raw signal <NUM> may comprise an entire spectrum or spectra of frequencies in use for wireless communications (e.g., satellite communications).

The raw signal <NUM> is received by the receiver <NUM> (<FIG>) and processed by a digitizing module <NUM>. The digitizing module <NUM> can comprise one or more analog to digital (A2D) converters for translating the raw signal <NUM> from an analog signal to a digital signal. The digitizing module <NUM> can output a digitized signal <NUM>.

The demodulator <NUM> can further have a windowing module <NUM> operably coupled to the digitizing module <NUM>. As noted above, the windowing module <NUM> can be a component of the signal detector <NUM>. The windowing module <NUM> can also cooperate with the processor <NUM> and the DSP <NUM> to complete the processes described herein.

In some embodiments, the windowing module <NUM> can be configured to limit the bandwidth of (e.g., band-limit) the digitized signal <NUM> or focus on a portion of the digitized signal <NUM> to ensure the demodulator <NUM> processes the desired portion of the spectrum encompassing the signal(s) of interest. In some embodiments, the desired portion of the spectrum may contain the one or more signals of interest (e.g., the signal <NUM> and the signal <NUM>). The windowing module <NUM> can also correct the bandwidth-limited portion of the spectrum for center frequency and bandwidth such that the signal(s) of interest (e.g., the composite signal <NUM> and the signals <NUM>, <NUM>) are processed by the demodulator <NUM>. For purposes of the following description, the bandwidth limited portion of the digitized signal <NUM> limited by the windowing module <NUM> may generally be referred to herein as a windowed signal <NUM>. In some embodiments, the windowed signal <NUM> may be a digital form of the composite signal <NUM> containing multiple constituent signals (e.g., the signal <NUM> and the signal <NUM>). One or more of the constituent signals can be the signal(s) of interest.

The demodulator <NUM> can further include an interference detector <NUM>. In some embodiments, the interference detector <NUM> can be configured to receive the windowed signal <NUM> and determine the presence of the signal <NUM> and the signal <NUM>, or the composite signal <NUM>, in addition to other interfering signals. In some embodiments, two or more signals that are themselves individually modulated (e.g., QPSK, 4QAM, 16APSK, etc.) may further be considered a modulation when propagated together as the composite signal <NUM>.

The interference detector <NUM> can process incoming windowed signal <NUM> in the time domain to determine the presence of multiple interfering signals (e.g., the signal <NUM> and the signal <NUM>). The interference detector <NUM> can also process the windowed signal <NUM> in the frequency domain. In some embodiments, the interference detector <NUM> can analyze the Fourier transform of the modulus of the windowed signal <NUM> to determine the presence of multiple constituent signals. In some other embodiments, the processes conducted by the interference detector <NUM> can be implemented in software.

The interference detector <NUM> may use processes in both frequency and time to determine at least a modulation estimate and estimates of a symbol rate or clock rate. In some embodiments, the modulation estimate may be derived by multiplying the windowed signal <NUM> by itself n-times until a continuous wave (CW) is the product of the windowed signal <NUM> raised to a power of n. As used herein, the operation of multiplying a signal by itself, or raising a signal to a power of n is generally referred to as "exponentiation. " Exponentiation of the windowed signal <NUM> can be completed multiple times to determine the presence of multiple constituent signals in the time domain and the frequency domain. Accordingly, the windowed signal <NUM> may be multiplied by itself until the interference detector <NUM> (or signal detector <NUM>) determines there are one, two, or more signals present in the windowed signal <NUM>. Each of the constituent signals (e.g., the signal <NUM> and the signal <NUM>) may have a different modulation and thus produce a CW product at different powers of n. For example, exponentiation of a composite signal <NUM> having three constituent signals with three different modulation types can produce three separate CW waveforms at three different powers of n. In another example, two or more of the constituent signals can have the same modulation and thus the CW waveforms would result at the same value of n. In some embodiments, the power of n is a multiple of two.

The interference detector <NUM> can further derive a symbol rate estimate through the exponentiation function of the windowed signal <NUM>. In some embodiments, when the signal is multiplied by itself a number of times, the phase of the symbols may correlate or cancel, resulting in a CW product indicated by a single frequency in the frequency domain. This process may also yield small side lobes, (e.g., "side spurs") that are evenly spaced (e.g., in the frequency domain) about the CW frequency. The spacing of the side lobes is related to the symbol rate for the carrier of the corresponding constituent signal and may be used to estimate the symbol rate. The interference detector <NUM> can further have one or more adaptive equalizers (not shown) configured to use the exponentiation product(s) and the spacing of the "side spurs" to further refine the one or more symbol rate estimates to derive one or more actual symbol rates corresponding to the constituent signals. In some embodiments, such adaptive equalizers can run at a multiple of the symbol rate estimate(s) to derive actual symbol rates. In some embodiments, this process may be completed for each distinct value of n (e.g., power of n). The one or more actual symbol rates can correspond to the one or more constituent signals present in the windowed signal <NUM>. For example, if the composite signal has three exemplary constituent signals with three different symbol rates (as above), three separate symbol rates can be derived by the interference detector <NUM>. In an embodiment, two or more constituent signals may be present having the same symbol rate. In another embodiment, the two or more constituent signals (e.g. the signal <NUM> and the signal <NUM>) can have the same symbol rates but different modulation.

The demodulator <NUM> can further include one or more adaptive regenerators ("ART") <NUM>. The acronym "ART" as used herein stands for Adaptive Regenerative Technology" and can generally refer to the processors comprising the ART <NUM>. The ART <NUM> of <FIG> may have multiple subcomponents or modules. When one or more signals (e.g., signals of interest and interfering signals) are detected by the interference detector <NUM>, the windowed signal <NUM> may pass to a separator module <NUM> within the ART <NUM>.

The separator module <NUM> may resample the windowed signal <NUM> using the modulation estimate (from the interference detector <NUM>) at X-times the symbol rate. In some embodiments, the windowed signal <NUM> can be resampled atX-times the symbol rate for each symbol rate detected by the interference detector <NUM>, similar to the interference detector <NUM>. Thus the separator module <NUM> can sample the incoming constituent signal(s) at a high rate and derive a symbol trajectory, shaping factor, and a more accurate estimate of the modulation type of each of the constituent signals present in the windowed signal <NUM>. The separator module <NUM> can also determine the constituent signals' frequency and bandwidth, and a phase offset between each of the constituent signals (e.g., the signals <NUM>, <NUM>) within the windowed signal <NUM>. As used herein, shaping factor may generally refer to concentration or distribution of signal energy of a given constituent signal (e.g., the signal <NUM> or the signal <NUM>). In some embodiments, the shaping factor may be a root-raised cosine spectra of the windowed signal <NUM>. Shaping factor may be used when referring to the frequency domain of the windowed signal <NUM> while "pulse shaping" may be used to refer to the time domain of the windowed signal <NUM>.

The ART <NUM> can further have a regenerator module <NUM> operably coupled to the separator module <NUM>. The regenerator module <NUM> can use the symbol trajectory, coupled with the shaping factor, modulation, and phase offset of the constituent signals to regenerate, or synthesize, each of the constituent signals (e.g., the signals <NUM>, <NUM>). The regenerator module <NUM> may use the bandwidth, frequency offset, and amplitude in the synthesis, or regeneration, of each of the constituent signals, as regenerated signal <NUM>. The regenerated signal <NUM> can represent multiple signals (as indicated with an ellipsis), that is, the regenerated or synthesized versions of each of the constituent signals <NUM>, <NUM>, for example. The regenerated signal(s) <NUM> are labeled 355a, 355b indicating the multiple possible paths of signal processing. In some embodiments the synthesis of each of the regenerated signals <NUM> may be completed simultaneously or at least concurrently.

In an embodiment, the regenerator module <NUM> can have a regeneration support module <NUM>. The regeneration support module <NUM> can receive the data related to signal regeneration from the separator module <NUM> (e.g., the symbol trajectory, coupled with the shaping factor, modulation, and phase offset). The regeneration support module <NUM> can further control transmission of such signal regeneration data, and the windowed signal <NUM>, as needed, to and from a regenerator modem <NUM> and on to other portions of the demodulator <NUM>.

In some embodiments, the regenerator modem <NUM> can be located apart from the rest of the demodulator <NUM>, but communicatively coupled to the regeneration support module <NUM>. The regenerator modem <NUM> can be located off-chip, for example. The demodulator <NUM> and the regenerator modem <NUM> can be implemented in complementary electronics, but on separate components. For example, the majority of the demodulator <NUM> can be on an FPGA, while the regenerator modem <NUM> is external of that FPGA but functions as a part of the regenerator module <NUM>. The regenerator modem <NUM> can thus be included in, for example, a separate ASIC, another FPGA, a fixed function FPGA, or a discrete or standalone modem.

In some embodiments, certain waveforms such as the DVB-S2X (digital video broadcasting-satellite) may a have dynamic formats and require dedicated demodulator/modulators designed and built by a specific manufacturer. Rather than build a modem from generic components within an FPGA for application with satellite waveforms, implementing a third party device (either via a dedicated chip or FPGA module) in the FPGA of a separate chip/board provides increased flexibility to adapt the demodulator <NUM> for use with nearly any signal waveform.

The regenerator modem <NUM> can be a modem associated with a vendor-specific satellite communications radio, such as a protected modem <NUM>. The configuration of the regenerator modem <NUM> may be specific to a user, a specific range of frequencies, or a particular use associated with the protected modem <NUM>. Accordingly, the physical and operational characteristics of the regenerator modem <NUM> can vary according to the protected modem <NUM>. Thus, there may be certain advantages or efficiencies realized by configuring the demodulator <NUM> to operate with a specific protected modem <NUM>.

In some systems, a particular interference cancelation process can, for example, synthesize a first signal, having the signal having the highest signal strength. In such a process, the regenerator module <NUM> may use a power separation between high and low power signals to regenerate a high power signal in the first stage then use successive regeneration stages to synthesize the low(er) power signal(s). This first (high power) signal can be canceled or reduced from the original signal (e.g., the raw signal <NUM>) forming a residual signal (e.g., the raw signal <NUM> minus the first signal). The interference reduction process can be repeated on the residual signal to remove a signal with the next-highest signal strength and/or refine the signal quality of one or more demodulated or synthesized signals. This process can be iterated several times to further refine the signal(s) of interest. Such iterations can require additional space on integrated circuits to accommodate multiple FGPAs, for example, to accomplish the sequential, or serial, processing. Alternatively, processing time may be increased significantly if the same circuitry is tasked with the multiple iterations.

The regenerator modem <NUM> can receive the information regarding the constituent signals or the signal(s) of interest derived by the separator module <NUM> via the regeneration support module <NUM>. In some embodiments, the regenerator modem <NUM> can support faster processing than the ART <NUM>, for example. This may be referred to herein as "faster than real time," where "real time" is relative to the processing time required to synthesize signals within the ART <NUM>. In some examples, the ART <NUM> can receive or "consume" signal data at a first data rate. The regenerator modem <NUM> on the other hand can process the signal data at a second rate that is a multiple of the first rate.

In at least one embodiment, the regeneration support module <NUM> can receive, or "consume", data at a first data rate (e.g., <NUM>, <NUM>, or <NUM>). The regenerator modem <NUM> can process such data at a second data rate that is significantly faster than the first data rate, or a multiple of the first data rate (e.g., <NUM>). The multiple can be a factor of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or more, or any value in between. In some other embodiments, the processing may be faster still. For example, the ART <NUM> may consume the data at the first rate of <NUM> while the regenerator modem <NUM> can process the signal data at the second rate of, for example, <NUM>.

The faster processing provided by the regenerator modem <NUM> can allow the ART <NUM> to demodulate and (re)modulate, or synthesize, the various signals of interest (or interfering signals) faster than the data is received (e.g., consumed) at the regenerator module <NUM> (e.g., the regeneration modem <NUM>). This can allow multiple iterations or loops of signal processing (e.g., modulation, demodulation, signal regeneration) within the regenerator module <NUM> before further processing. In some embodiments, the separated aspect of the regenerator modem <NUM> from the rest of the ART <NUM> can simplify the circuit design, while increasing processing speed and efficiency. For example, the multiple iterations of modulation/demodulation within the regenerator module <NUM> may alleviate the need to repeatedly iterate the process to remove multiple signals of interest from the raw signal <NUM>.

Another possible advantage of such a configuration allows a specific demodulator <NUM> to operate with different regenerator modems <NUM>, and therefore different protected modems <NUM>. Certain manufacturers may be motivated to collaborate because increased performance may be realized from the signal cancellation methods disclosed herein when the demodulator <NUM> implements exactly what the protected modem <NUM> implements, including forward error correction (FEC) and other data processing methods. For example, FEC can be implemented to correct errors in a link, or otherwise improve link gain. Some waveforms, such as DVB-S2X, can implement FEC link gain as part of the link calculation. Such waveforms can have dynamic FEC, meaning that as the link margins change, FEC rates can also adjust.

In some embodiments, if the regenerated signal 355a is one of the constituent signals (e.g., the signal <NUM> and the signal <NUM>), the processor <NUM> may determine which of the constituent signals is/are a desired signal and protect or otherwise isolate and focus on the desired signal (e.g., the signal <NUM>). The regenerator module <NUM> can pass one or more regenerated signals <NUM> on to the inversion module <NUM>. The regenerated signal 355a can be inverted within the inversion module <NUM> and subsequently canceled from the raw signal <NUM>. Similarly, the regenerated signal 355b can be supplied back to the interference detector <NUM> or the separator module <NUM> depending on the nature of the regenerated signal 355b for additional processing for more refined versions of the regenerated signals <NUM>.

For example, if the signal <NUM> and the signal <NUM> are constituent signals of the windowed signal <NUM>, the processor may select the signal <NUM> (e.g., the regenerated signal 355a) as the desired signal and output an "interference free" version of the signal <NUM>. The "interference free" version can have a reduced or negligible interfering signal strength. In some embodiments, the signal of interest (e.g., the signal <NUM>) can be used to further characterize the noise floor of the composite signal <NUM>. The noise floor can then be canceled to increase the SNR of the signal of interest (e.g., the signal <NUM>). The various feedback loops from the regenerator module <NUM> and the cancelation module <NUM> allow one or more of the signals of interest, interfering signals, noise floor, etc. to be used to refine the signals of interest.

If the regenerated signal(s) 355a is/are not the signals of interest, they may be used for interference cancelation. The ART <NUM> can further have an inversion module <NUM> operably coupled to the regenerator module <NUM>. The inversion module <NUM> can invert the regenerated signal 355a (e.g., the signal <NUM>) and sum the inverted copy with a copy of the digitized signal <NUM> in a cancelation module <NUM>. Due to the processing time, the copy of the digitized signal <NUM> may be provided through a delay module <NUM> to provide, for example, proper phase for signal cancelation. The cancelation module <NUM> may correct the inverted copy of the interfering signal for gain and phase with the raw signal <NUM> to produce an interference free signal <NUM>. In some embodiments, the interference free signal <NUM> may be processed again to further reduce any interference present by supplying the interference free signal <NUM> from the cancelation module <NUM> to the interference detector <NUM> or the separator module <NUM>, as indicated by the dashed line. The interference free signal <NUM> may be considered a synthesized copy of the desired signal (e.g., the signal <NUM>) or a copy of the digitized signal <NUM> with the interfering signal (e.g., the signal <NUM>) canceled. The signal <NUM> and the signal <NUM> are used as primary examples herein, but each may represent multiple signals or interfering, complex modulations. In the foregoing example, the desired signal is the signal <NUM> and the signal <NUM> is the interfering signal. Thus, the signal <NUM> can represent multiple interfering signals together.

In some embodiments, the demodulator <NUM> can further have a digital to analog (D2A) converter (not shown) coupled to the cancelation module <NUM> and the regenerator module <NUM> that may convert the processed signals back into an analog signal.

In some embodiments the regeneration of each of the constituent signals (e.g., the signal <NUM> and the signal <NUM>) may be completed simultaneously or at least concurrently. Portions of the ART <NUM> can be used in an iterative sequence to refine multiple signals within the raw signal <NUM>. If multiple signals of interest are present, the synthesized, or regenerated constituent signals can be fed back to the interference detector <NUM> for further processing. For example, if the strongest signal is regenerated first, the demodulator <NUM> can refine lower-power constituent signals by removing or canceling the highest power signals, and providing the residual signal (e.g., the interference free signal <NUM>) for additional processing within the ART <NUM>. This is described in further detail in connection with, for example, <FIG>, <FIG>, and <FIG>. As described below, various configurations can be possible, routing particular versions of one or more of the regenerated signals from the regenerator module <NUM> back to the interference detector <NUM> and/or the separator module <NUM>. These various routes are shown in dashed lines. Depending on the nature of the synthesized (regenerated) signal, the demodulator <NUM> can further process the regenerated signal, the residual signal.

<FIG> is a functional block diagram illustrating an embodiment of a method for interference reduction using the demodulator of <FIG>. In general, the ART <NUM> can perform blind signal separation, signal synthesis, and signal demodulation of multiple signals concurrently or simultaneously. For convenience of description, the signal synthesis can be broken down into multiple stages, synthesizing an exemplary high power signal and then using the regenerated high power signal to extract, or estimate another low(er) power signal. The estimated low power signal can then be used to refine the high power signal. The stages can be repeated, or iterated, for any number of additional signals within the composite signal <NUM>, for example.

In a first stage <NUM>, the demodulator <NUM> can receive the composite signal <NUM>. The composite signal <NUM> can thus also be the raw signal <NUM>, received at the digitizing module <NUM>, as described above.

In the first stage <NUM>, the ART <NUM>, for example, can receive information about the constituent signals within the signal <NUM> (e.g., the signals <NUM>, <NUM>) from the interference detector <NUM>. The separator module <NUM> can then resample (e.g., oversample) the windowed signal <NUM>, allowing the ART <NUM> to perform a first demodulation <NUM> of the one or more constituent signals using, for example, the symbol trajectory, coupled with the shaping factor, modulation, and phase offset of the various constituent signals. This can result in a first estimate or a first demodulation estimate of the signal. In some examples, such as that shown in <FIG>, the signal <NUM> may be a high(est) power signal of multiple signals within the composite signal <NUM>. Thus, in the first stage <NUM>, the signal <NUM> ("H" for "high power") may be synthesized (e.g., demodulated) first, as an estimated signal H <NUM>, because the high power provides more signal strength facilitating the signal separation. The first stage <NUM> can be similar to the processes implemented at the separator module <NUM>, for example. The ART <NUM> can then perform a first remodulation <NUM> of estimated signal H <NUM> (e.g., signal <NUM>) to derive the synthesized version of the signal "H~" <NUM>. The ART <NUM> can then perform a cancelation <NUM> (at for example, the cancelation module <NUM>), removing the synthesized signal H~ <NUM> from the composite signal <NUM>. This can leave a residual signal that is an estimate of the low power signal ("L"), referred to herein as an estimated low power signal L' <NUM> (the signal <NUM>, in this example).

The first stage <NUM> can then output the synthesized high power signal H~ <NUM>, an estimate of the low power signal L' <NUM>, and the composite signal <NUM> (e.g., a copy of the composite signal <NUM> can be passed through the first stage <NUM>). These outputs can be fed to a second stage <NUM>. The second stage <NUM> can receive the outputs of the first stage <NUM> and perform a second demodulation <NUM> on the estimate of the low power signal L' <NUM>. The ART <NUM> can then perform a second remodulation <NUM> to derive a synthesized version of the low power signal L~ <NUM>. The ART <NUM> can then further perform a cancelation <NUM>, reducing or removing the low power signal L~ strength to result in a refined estimate or refined synthesized version of the high power signal H' <NUM>. The first stage <NUM> and the second stage <NUM> can thus be used in tandem in order to reduce interference to characterize and separate the various the constituent signals within the composite signal <NUM>.

In some embodiments, the first stage <NUM> and the second stage <NUM> can be used as a paired set of processes within the ART <NUM>. The first stage <NUM> and the second stage <NUM> can be repeated any number of times to further refine the synthesized high power signal H~ <NUM> and the synthesized low power signal L~, and/or any other signals present within the composite signal <NUM>.

In one example, each of the first stage <NUM> and the second stage <NUM> can be implemented in one or more of a FPGA, ASIC, or other circuitry (not shown). The individual circuits comprising the first stage <NUM> and the second stage <NUM> can then be implemented in multiple iterations for serial processing of the one or more constituent signals, concatenating the associated circuitry. The ART <NUM> can implement such serial processing for the functions of, for example, the signal separator <NUM>, the regenerator module <NUM>, the inversion module <NUM>, and the cancelation module <NUM>. However, because each pair of serial processing stages is disposed in serial circuitry, this arrangement can occupy considerable physical space.

Thus, the arrangement of the demodulator <NUM>, and more particularly the configuration of the regenerator module <NUM> as the regeneration support module <NUM> and the regenerator modem <NUM> can significantly reduce the amount of physical space required to separate, synthesize, demodulate, and protect one or more signals of interest. The faster processing speed of the regenerator modem <NUM> can provide several iterations of the demodulation-remodulation of the first stage <NUM> and the second stage <NUM> without the physical space requirements of multiple concatenated circuits for doing the same.

<FIG> is a functional block diagram illustrating another embodiment of a method for interference reduction using the demodulator of <FIG>. In some embodiments, the regenerator modem <NUM> can implement the first stage <NUM> as described above. Then in place of, or in addition to the second stage <NUM>, the demodulator <NUM> can implement an echo cancelation stage <NUM>. The echo adjustment stage <NUM> can take as an input, a copy of the estimate of the low power signal L' <NUM> perform and perform an echo adjustment <NUM>. IN some embodiments the echo adjustment <NUM> can include an adjustment in gain and/or phase, similar to echo cancelation. The output of the echo cancelation can be a synthesized version of the low power signal <NUM>, similar to synthesized version of the low power signal L~ <NUM>. The synthesized version of the low power signal <NUM> can be canceled <NUM> from the composite signal <NUM> to provide a refined version of the refined synthesized version of the high power signal <NUM>, similar to refined synthesized version of the high power signal H' <NUM>.

<FIG> is a flowchart of an embodiment of a method of signal separation using the demodulator of <FIG> and the methods of <FIG> and <FIG>. As shown, a method for signal separation ("method") <NUM> may start at block <NUM> with receiving the raw signal <NUM> (see, <FIG>). The raw signal <NUM> can also be digitized by the digitizing module <NUM> at block <NUM>. In some embodiments, the signal(s) of interest (e.g., the signal <NUM>, <NUM>) may only occupy a portion of the raw signal <NUM> spectrum. Additionally, the demodulation system <NUM> may selectively limit the amount of raw signal <NUM> regarded for signal processing. At block <NUM>, the windowing module <NUM> can adjust the bandwidth that the demodulation system <NUM> regards as the bandwidth of interest. For example, the raw signal <NUM> may be a large swath of frequencies containing not only the signal(s) of interest (e.g., the signal <NUM> and the signal <NUM>) but also various other transmissions not necessarily intended for the ground station <NUM> or other interfering transmissions. Accordingly, at the block <NUM>, the windowing module <NUM> may band limit the raw signal <NUM> (e.g., the windowed signal <NUM>, <FIG>) to focus on the bandwidth in which the signal <NUM> is expected to be received. In some embodiments, both the signal <NUM> and the signal <NUM> may be signals of interest, thus the windowing module <NUM> can band limit the raw signal <NUM> to receive both signals <NUM>, <NUM>. In some other embodiments, the windowed signal <NUM> can include more than the signals <NUM>, <NUM>. In some embodiments, little or no information may be known at the demodulator <NUM> about the signal <NUM>, the signal <NUM>, or any other interfering signals that are received. In some cases however, at least an expected bandwidth may be known.

Due to Doppler shift over long transmission distances from the ground station <NUM> or the ground station <NUM> to the satellite <NUM>, and then to the ground station <NUM>, certain time delays or shifts in frequency may result. For example, the signal <NUM> may be expected to have a center frequency of1. <NUM> (Gigahertz) and a bandwidth of <NUM> (Megahertz). Such a signal (e.g., the signal <NUM>) may be shifted in time and frequency over the long transmission path, and thus arrive at the ground station <NUM> as a portion of the composite signal <NUM> having a center frequency of <NUM> and a bandwidth of <NUM> as determined by the windowing module <NUM>. The bandwidth and center frequency of the windowed signal <NUM> may further depend on other factors determined by, e.g., the processor <NUM>.

Thus in some embodiments, the windowing module <NUM> may further adjust the bandwidth of the received portion of the spectrum (e.g., the raw signal <NUM>) to focus on the signal <NUM>. In another embodiment, the composite signal <NUM> may have one or more constituent signals (e.g., the signal <NUM> and the signal <NUM>). The windowing module <NUM> may then adjust the bandwidth of the received raw signal <NUM> to encompass the all of the constituent signals (e.g., the signals122, <NUM>). As described below in connection with <FIG>, the composite signal <NUM> may comprise multiple constituent signals <NUM>, <NUM> overlapped in frequency.

At block <NUM> the interference detector <NUM> may exponentiate the windowed signal <NUM>. The exponentiation process can include raising the windowed signal <NUM> to a power of n, or multiplying the windowed signal <NUM> by itself n number of times until a CW is the product of the power of n, where n is an integer. In some embodiments, the exponentiation can be completed in the time domain. The interference detector <NUM> can be configured to perform such an operation in small time blocks in the time domain of the windowed signal <NUM>. In some embodiments, this may be performed by software.

At decision block <NUM> the interference detector <NUM> may determine if one or more CWs are produced by the exponentiation. If not, the method <NUM> may increment the value of n at block <NUM>. The method <NUM> may then return to block <NUM> to again exponentiate the windowed signal <NUM> at n+<NUM>, for example. The exponentiation at block <NUM> may be repeated until one or more CWs are present. Each signal (e.g., signal of interest or interfering signal) present within the windowed signal <NUM> may present an individual CW product.

In some embodiments, multiple constituent signals within the composite signal <NUM> (e.g., the windowed signal <NUM>) may yield more than one CW product at different powers of n. For example, if the signal <NUM> is modulated using BPSK the continuous wave may result at n = <NUM>. As another example, if the signal <NUM> is modulated using QPSK then the CW waveform would result from a power of n = <NUM>. In some embodiments, n is a factor of <NUM>. The power index n then provides an indication of the modulation type: <NUM> = CW; <NUM> = BPSK; <NUM> = QPSK, and on to n = m. In some embodiments m may be any integer multiple of two. Certain additional processes may be required to disambiguate between QPSK and 16QAM, for instance as both may yield a CW at n = <NUM>. This is described in more detail below.

In some embodiments, the windowed signal <NUM> received by the interference detector <NUM> may be received as a data stream of symbols in I (in-phase) and Q (quadrature) form, where I represents a symbol coordinate on a real axis and Q represents a symbol coordinate on an imaginary axis. The I and Q data may further be implemented to represent polar coordinates of a given symbol. Accordingly, a complex signal can be represented as SC = Si + Sq. The signal SC is exponentiated (e.g., raised to a power n) where n can be, for example, a multiple of two: n = <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, etc. The value(s) of n can indicated one or more modulation types. The complex components of the signal SC, Si and Sq, can also be exponentiated to determine whether the modulation type has a constant amplitude. For example, at n = <NUM>, the modulation can be QPSK or QAM. In order to disambiguate between the two types, the interference detector <NUM> can produce a histogram of symbol vectors representing symbol power and phase to determine whether there are multiple power and phase states within each quadrant of I and Q. The histogram can reveal whether the modulation of SC is QPSK, 8QAM, 16QAM, or 64QAM, for example. In some embodiments, APSK (e.g., <NUM>-APSK or <NUM>-APSK) may be present. Such signals may be associated with Digital Video Broadcasting-Satellite - Second Generation (DVB-S2). In some other embodiments, the interference detector <NUM> can further distinguish MSK, GMSK, OQPSK, and 8PSK among other modulation types, such as those listed above in the description of <FIG>.

At block <NUM>, the interference detector <NUM> can also derive one or more symbol rates of the one or more constituent signals within the windowed signal <NUM>. As noted above, the interference detector <NUM> can include one more adaptive equalizers configured to use the exponentiation results to refine one or more symbol rate estimates corresponding to the one or more constituent signals. The adaptive equalizers may be operated (e.g., clocked) at a multiple of the estimated symbol rate in order to refine the symbol rate estimates into actual symbol rates that can be provided to the ART <NUM>. If at the decision block <NUM>, the interference detector <NUM> determines the presence of one or more CW products, the method proceeds to block <NUM>.

At block <NUM>, the interference detector <NUM> may provide the one or more symbol rates (from block <NUM>) and a modulation estimate based on the power factor n (from block <NUM>) to the ART <NUM>. The ART <NUM> may then resample the windowed signal <NUM> using the power factor n at X-times the symbol rate (from block <NUM>). Accordingly, the ART <NUM> may resample, or oversample, the windowed signal <NUM> at a high rate to determine a symbol trajectory(ies) and refine the modulation type(s). In the presence of multiple constituent signals, the ART <NUM> may further determine phase offset and frequency offset between the individual constituent signals. The block <NUM> may occur in multiple concurrent instances, according to the number of constituent signals. For example, <FIG> indicates three resampling blocks <NUM> corresponding to the multiple signals (e.g., the signal S1, and signal S2 through signal Sk, described below).

At block <NUM>, the ART <NUM> may further regenerate the constituent signals using one or more of the symbol trajectory, shaping factor, phase offset, frequency offset, bandwidth, and other available information about the constituent signals. The block <NUM> can include multiple iterations of the first stage <NUM> and the second stage <NUM> of the demodulation-remodulation described in connection with <FIG>. The synthesized, or regenerated signals are labeled as signal S1, signal S2, through signal Sk. The signal Sk indicates that more than two signals up to a k-number of signals may be regenerated via multiple iterations of the first stage <NUM> and the second stage <NUM>. In some embodiments the k-number of signals may be processed concurrently and thus simultaneously or concurrently demodulated.

At block <NUM>, the various regenerated constituent signals can be demodulated (e.g., the signal S1, S2, Sk). In some embodiments, the ART <NUM> can independently derive each of the constituent signals and simultaneously demodulate them even in the presence of a frequency overlap. In some embodiments, the regeneration at block <NUM> can be iterative as described above in connection with <FIG>. The iterations are indicated by the curved arrow at block <NUM>. The processing can be accomplished using the ART <NUM>, incorporating a separate circuitry for the regenerator modem <NUM>. As described above, if, for example, the strongest signal is regenerated first, and it is not a signal of interest, it can be canceled from the digitized signal <NUM>. The remaining signal, or residual signal, can be reprocessed by the interference detector <NUM> and the ART <NUM>. This can require the multiple passes through the regenerator modem <NUM> described above, for example.

In another embodiment, multiple iterations of the process of the method <NUM> can be facilitated by the regenerator modem <NUM>. Since the regenerator modem <NUM> is capable of processing data faster than data is supplied to it by the regeneration support module <NUM>, several loops or iterations of signal regeneration are possible at, for example, block <NUM>.

At decision block <NUM>, the processor <NUM> can determine whether one or more of the regenerated signals are the desired signals. Accordingly, the processor <NUM> may determine that the signal of interest (e.g., the signal <NUM>) was not yet recovered by the method <NUM>. In some embodiments this may occur because the signal of interest (e.g., the signal <NUM>) has a low power level, or a lower power level than the regenerated signals S1:Sk. For example, the method <NUM> may have been able to isolate one or more constituent signals having a higher power level than the signal of interest and determine such signals are interfering signals. If one or more of the regenerated signals is not the signal of interest, at block <NUM> one or more inverted copies of the one or more of the regenerated interfering signals may be provided to the cancelation module <NUM>. This process can be analogous to the cancelation <NUM>, <NUM> (<FIG>), for example. In some embodiments, if none of the regenerated signals at block <NUM> are the desired signal then they can be treated as interfering signals and canceled.

The cancelation module <NUM> may also take as an input, a copy of the windowed signal <NUM> that is delayed by the delay module <NUM> at block <NUM>. At block <NUM> a residual signal that has had one or more regenerated signals (not signal(s) of interest) cancelled from it may be produced. Accordingly, the windowed signal <NUM> minus the canceled interfering signals at block <NUM> may generate the desired signal (e.g., the signal <NUM>) at block <NUM>. The residual signal can result from the combination of the inverted interfering signal and the digitized signal <NUM>. The residual signal may be a version of the digitized signal <NUM> having at least one constituent signal (e.g., the interfering signal) canceled. In some embodiments this may be referred to as the noise floor. This may further enable the demodulator <NUM> to characterize the noise floor and increase the SNR of the signal of interest, the signal <NUM> for example.

If at decision block <NUM> the processor <NUM> determines that one or more of the regenerated and demodulated signals are desired signals, the method <NUM> can move to block <NUM>. At block <NUM>, the processor <NUM> may then protect the one or more desired regenerated signals. In some embodiments, the method <NUM> may result in any number of regenerated signals. In some embodiments, the undesired signals may be discarded or ignored. In some other embodiments, the undesired signals may be used to refine the desired signal by adaptive cancelation through demodulation-remodulation of the first stage <NUM> and the second stage <NUM>, or via echo adjustment/echo cancelation described in connection with <FIG>.

The method <NUM> can be iterative. Each iteration of the method <NUM> may provide successively more accurate regenerations of the constituent signals (e.g., the signals <NUM>, <NUM>). However, the processing time may be reduced, and efficiency increased using the regenerator modem <NUM>. Accordingly, by using the interference cancelation method described above, multiple signals may be overlapped in frequency, maximizing the use of available frequency spectra.

<FIG> that follow are plots of possible ways that signals may be overlapped and transmitted while maintaining sufficient distinguishing qualities such that they may be separated and demodulated as described herein. By overlapping two or more signals (e.g., the signal <NUM> and the signal <NUM>) in frequency, a communication link (e.g., the communication system <NUM>) may make more efficient use of available frequency spectra and increase data throughput.

As mentioned above, the sum of two or more modulated signals <NUM>, <NUM> can form a distinct modulation. In some embodiments, the combined signals may be mutually interfering. For a given degree of interference or noise contamination of a communication channel (e.g., in the communication system <NUM>), it is possible to communicate discrete data (digital information) nearly error-free up to a computable maximum rate through the channel. Such a maximum may be computed using Shannon's theorem. As applied to overlapped frequencies as described herein, Shannon's theorem shows that a change in signal to noise ratio of the modulated signals <NUM>, <NUM> is dependent upon the proposed modulation technique for each of the signals <NUM>, <NUM> and their underlying required energy per bit to noise power spectral density ratio (EsN0). This value can also be expressed as signal-to-noise ratio (SNR) per bit, or as a normalized SNR measure of the individual signals <NUM>, <NUM>. In some embodiments, such calculations can be useful to derive a maximum overlap and optimum bandwidth or modulation type when transmitting overlapped signals. In some other embodiments, such calculations may further be useful in separation, regeneration, and demodulation methods or techniques for overlapped signals, as described herein.

<FIG> is a plot of two signals overlapped in frequency that may be separated using the methods of <FIG>, <FIG>, and <FIG>. A plot <NUM> is shown with amplitude on the vertical (y) axis versus frequency (f) on the horizontal (x) axis. The plot <NUM> shows an embodiment of two signals such as the signal <NUM> (bounded by dashed lines) and the signal <NUM> (bounded by solid lines) that can be overlapped in frequency and demodulated by the ART <NUM>. In an embodiment, the signal <NUM> and the signal <NUM> can have a same bandwidth <NUM>. The signal <NUM> can have a center frequency <NUM> and the signal <NUM> can have a center frequency <NUM>. A difference between the center frequencies <NUM>, <NUM> may generally be referred to herein as a phase offset <NUM>.

In an embodiment, the ART <NUM> may distinguish the signal <NUM> from the signal <NUM> during resampling (e.g., the blocks <NUM>) in part due to the increased sample rate used by the separator module <NUM>. While the signal <NUM> and the signal <NUM> are only offset slightly by the phase offset <NUM>, the high resampling rate (e.g., X-times the symbol rate) allows the ART <NUM> to distinguish between multiple signals with only slight variations in center frequency, amplitude or bandwidth.

For example, the phase offset <NUM> can be a result of the phase shift between the signal <NUM> and the signal <NUM>. Accordingly, if the signal <NUM> and the signal <NUM> are both modulated with QPSK with a <NUM> degree (π/<NUM> radians) phase offset <NUM>, the QPSK constellations of each signal <NUM>, <NUM> will appear with a <NUM> degree shift in phase; the ART <NUM> can then distinguish the signal <NUM> from the signal <NUM> using the symbol trajectory and shaping factor of the signal <NUM> and the signal <NUM> to regenerate and demodulate both of the signals <NUM>, <NUM>. In some embodiments, the system <NUM> may be capable of separating, regenerating, and demodulating more than two signals at once.

<FIG> is another plot of two signals overlapped in frequency that may be separated using the methods of <FIG>. A plot <NUM> is shown with amplitude on the vertical (y) axis versus frequency (f) on the horizontal (x) axis. The plot <NUM> further shows the signal <NUM> (bounded by dashed lines) and the signal <NUM> (bounded by solid lines) with the same bandwidth <NUM> as before. The difference between the plot <NUM> and the plot <NUM>, however, is that in the plot <NUM>, the signals <NUM>, <NUM> are completely overlapped in frequency, both having a center frequency <NUM>. The plot <NUM> also shows a difference in amplitude <NUM>. The difference in amplitude <NUM> indicates that while the signal <NUM> and the signal <NUM> are share the same bandwidth <NUM> and the same center frequency <NUM>, the difference in amplitude <NUM> (e.g., a power level or received signal strength) can be sufficient to distinguish the signals <NUM>, <NUM> using the method <NUM> disclosed herein. Accordingly the ART <NUM> may separate, regenerate, and demodulate two or more frequencies with the same bandwidth <NUM> and the same center frequency <NUM> when there is a difference in amplitude <NUM>.

<FIG> is another plot of two signals overlapped in frequency that may be separated using the methods of <FIG>. A plot <NUM> is shown with amplitude on the vertical (y) axis versus frequency (f) on the horizontal (x) axis. The plot <NUM> further shows the signal <NUM> (bounded by dashed lines) and the signal <NUM> (bounded by solid lines) having a same center frequency <NUM> and the same amplitude <NUM>. The plot <NUM> further shows the signal <NUM> having a bandwidth <NUM> and the signal <NUM> having a bandwidth <NUM>. The difference in bandwidth between the signal <NUM> and the signal <NUM> can be sufficient to allow the ART <NUM> to separate, regenerate, and demodulate the signals <NUM>, <NUM>.

<FIG> is a flowchart of a method of separation and demodulation of overlapped signals using the system of <FIG>. A method <NUM> starts at block <NUM> when a ground station (e.g., the ground station <NUM> of <FIG>) receives an input (e.g., the raw signal <NUM>) having two or more constituent signals. In some embodiments, the two or more constituent signals (e.g., the signal <NUM> and the signal <NUM>) may be signals of interest. In some other embodiments the input may have one or more interfering signals.

At block <NUM> the demodulator <NUM> may detect certain interfering signals within a portion of the input (e.g., the windowed signal <NUM>). The interference detector <NUM> can derive a symbol rate for the two or more constituent signals <NUM>, <NUM> within the windowed signal <NUM>. The interference detector <NUM> can also derive a modulation estimate through exponentiation of the windowed signal <NUM> (e.g., power of n). The CW waveforms that result from the exponentiation (e.g., the power of n) may be used to determine phase offset, frequency offset, bandwidth, and time delay.

At block <NUM>, one or more adaptive equalizers can be applied to the windowed signal <NUM> at X times the symbol rate of the individual constituent signals <NUM>, <NUM> to determine the symbol trajectory, shaping factor, phase offset, frequency offset, and modulation type of the signal <NUM> and the signal <NUM>.

At block <NUM>, the demodulator <NUM> and more specifically the ART <NUM> may regenerate or synthesize the constituent signals (e.g., the signal <NUM> and the signal <NUM>) based on one or more of the bandwidth, symbol trajectory, shaping factor, modulation type, phase offset, and frequency offset. The regenerator module <NUM> can use the regenerator modem <NUM> to process the separated signals at a "faster than real time" rate in order to iteratively refine the synthesized or regenerated constituent signals as noted above in connection with <FIG>, <FIG>, and <FIG>. The ART <NUM> can consume, or take in sequential portions (e.g., first portion, second portion, third portion, etc.) at a first data rate. Each portion can represent snapshots of the signal (e.g., the digitized signal <NUM>) in time. Each portion can be delivered sequentially to the regenerator module <NUM> in addition to the signal information derived by the signal separator <NUM>. The regenerator modem <NUM> can process the portions of the digitized signal <NUM> at a second rate that is faster than the first rate. Thus the iterative demodulation/remodulation associated with <FIG> and <FIG>, for example, can be performed multiple times on the first portion in the time required for the demodulator <NUM> to receive a subsequent, second portion of the incoming signals. This can reduce the time and amount of circuitry required to conduct iterative signal enhancement and interference mitigation.

At decision block <NUM>, the processor <NUM> can determined if the regenerated signals are signals of interest. If the regenerated signals are signals of interest, the method <NUM> can proceed to block <NUM>.

At block <NUM>, the demodulator <NUM> can demodulate each of the constituent signals. In some embodiments, the constituent signals can be demodulated simultaneously. In some other embodiments, the adaptive regeneration as disclosed in the method <NUM> can occur independent of time delay. Due to the adaptive equalization and the resampling at X-times the symbol rate, a more accurate estimation of the constituent signals can be generated at a faster rate than by interference cancelation alone. In some embodiments, the steps indicated in block <NUM>, block <NUM>, and block <NUM> can be executed in software. In some embodiments, the steps indicated in block <NUM> and block <NUM> can be executed in firmware.

If at decision block <NUM> the signals are not signals of interest, the regenerated signals (e.g., the block <NUM>) can be deemed interfering signals. Accordingly, at block <NUM>, the demodulator <NUM> (<FIG>) can cancel the interfering signals from the windowed signal <NUM>. The method <NUM> can the proceed to block <NUM> and outputting at least one signal of interest.

In some embodiments, the method <NUM> can be repeated or iterated as needed to demodulate or separate constituent signals. For example, such iterations can be accomplished at a rate that is "faster than real time" by incorporating the regenerator model <NUM>. As described above, the regenerator modem <NUM> can process the data at a rate that may be several multiples of the rate at which the data is consumed at the ART <NUM>. The method <NUM> can be combined with the method <NUM> and the method <NUM> to effect additional interference cancelation by canceling one or more constituent signals from a time delayed copy of the raw signal to determine a residual signal (e.g., block <NUM> of <FIG>) and re-process the residual signal using the method <NUM>.

The methods described herein may be implemented in hardware, software, firmware, or any combination thereof. Such methods may be implemented in any of a variety of devices such as general purposes computers, wireless communication device handsets, or integrated circuit devices having multiple uses including application in wireless communication device handsets and other devices. Any features described as modules or components may be implemented together in an integrated logic device or separately as discrete but interoperable logic devices. If implemented in software, the methods may be realized at least in part by a computer-readable data storage medium comprising program code including instructions that, when executed, performs one or more of the methods described above. The computer-readable data storage medium may form part of a computer program product, which may include packaging materials. The computer-readable medium may comprise memory or data storage media, such as random access memory (RAM) such as synchronous dynamic random access memory (SDRAM), read-only memory (ROM), non-volatile random access memory (NVRAM), electrically erasable programmable read-only memory (EEPROM), FLASH memory, magnetic or optical data storage media, and the like. The techniques and methods additionally, or alternatively, may be realized at least in part by a computer-readable communication medium that carries or communicates program code in the form of instructions or data structures and that can be accessed, read, and/or executed by a computer, such as propagated signals or waves.

The program code may be executed by a processor, which may include one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, an application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry, as described in connection with <FIG>. Such a processor may be configured to perform any of the methods and functions described in this disclosure. A general purpose processor may be a microprocessor; but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. Accordingly, the term "processor," as used herein may refer to any of the foregoing structure, any combination of the foregoing structure, or any other structure or apparatus suitable for implementation of the methods described herein.

Although embodiments of the disclosure are described above for particular embodiment, many variations are possible For example, the numbers of various components may be increased or decreased, modules and steps that determine a supply voltage may be modified to determine a frequency, another system parameter, or a combination of parameters. Additionally, features of the various embodiments may be combined in combinations that differ from those described above.

Those of skill will appreciate that the various illustrative blocks and modules described in connection with the embodiment disclosed herein can be implemented in various forms. Some blocks and modules have been described above generally in terms of their functionality How such functionality is implemented depends upon the design constraints imposed on an overall system. Skilled persons can implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the disclosure. In addition, the grouping of functions within a module, block, or step is for ease of description. Specific functions or steps can be moved from one module or block or distributed across to modules or blocks without departing from the disclosure.

Claim 1:
A method for separating a first signal from a second signal of a plurality of constituent signals within a composite signal, the method comprising:
receiving (<NUM>), at a first clock rate, a first portion of the composite signal spanning a first period of time;
exponentiating (<NUM>), by one or more processors (<NUM>), the first portion to detect the first signal and the second signal within the composite signal and determine,
a first modulation estimate of the first signal,
a second modulation estimate of the second signal, and
at least one symbol rate;
resampling (<NUM>), by the one or more processors (<NUM>), the first portion based on the first modulation estimate and the second modulation estimate at x-times the at least one symbol rate to determine at least one symbol trajectory, at least one modulation type, and offset information between the first signal and the second signal, x being an integer greater than zero;
and characterized in further comprising:
determining (<NUM>), by a regenerator modem (<NUM>) disposed off-chip, a synthesized first signal and a synthesized second signal representing the first signal and the second signal within the first period of time at a second clock rate, the second clock rate being a multiple of the first clock rate;
wherein determining a synthesized first signal and a synthesized second signal comprises:
generating, by the regenerator modem (<NUM>), a first demodulation estimate based on the resampling;
remodulating, by the regenerator modem (<NUM>), the first demodulation estimate based on the at least one modulation type to form the synthesized first signal;
canceling, by the regenerator modem (<NUM>), the synthesized first signal from the first portion to form a first residual signal including an estimate of the second signal;
demodulating, by the regenerator modem (<NUM>), the first residual signal to form a second demodulation estimate; and
remodulating, by the regenerator modem (<NUM>), the second demodulation estimate to form the synthesized second signal;
canceling, by the one or more processors (<NUM>), the synthesized second signal from the first portion to form a first refined synthesized first signal,
and repeating, within the regenerator modem (<NUM>), the demodulating and the remodulating to form a refined synthesized second signal and a second refined synthesized first signal, at the second clock rate.