Patent Application
20150358040
Aspects of various embodiments are directed to communications, and suppressing interference in communications.
Many communication approaches involve the transmission and reception of signals in noisy environments. For instance, many communication signals involve the use of bandwidth that is shared by two or more signals, and a communication medium that is subject to other noise. Accordingly, various forms of interference may occur, which can be undesirable.
As a specific example, one communication approach involves receiving signals with multiple antennas. Signals received on each antenna can be combined to form a combined signal representing the transmitted form of the signal. However, such approaches can be challenging to implement. For instance, different antennas may receive electromagnetic waves of differing strength, as may depend upon the orientation of the antennas. Undesired signals may be difficult or impossible to suppress, and proper signal detection can require costly duplication of circuitry for each antenna.
These and other matters have presented challenges to communications, for a variety of applications.
Various example embodiments are directed to communication apparatuses and their implementation.
According to an example embodiment, an apparatus includes two or more antennas that receive radio signals and respective circuits that electronically steer the antennas and combine signals received thereby. An analog-type mode involves directing the antennas toward a signal source using an analog portion of the signals to modify a radiation pattern of the antennas, based on at least one of estimated phase-shifts and estimated amplitude shifts of the received radio signals. In a digital-type mode, a digitally modulated portion of the signals are used to electronically direct the antennas at the signal source in a similar manner. Such approaches may generally involve beam steering, and null steering to mitigate interference. Various embodiments are directed to related methods.
In a more specific embodiment, an apparatus includes a signal source that transmits hybrid in-band on-channel ((H)IBOC) signals, and a receiver having two or more antennas that receive the (H)IBOC signals and respective circuits as above, that steer the antennas and combine the received signals.
In some implementations, the steering involves null steering to mitigate or eliminate interference, as may be present in channels adjacent a central channel in which a desired signal resides (e.g., central relative to a carrier signal). In some embodiments, the null steering is carried out by generating surrogate signals having a frequency range centered on a central frequency of the respective central channel and the respective frequencies of the interference. These surrogates can be processed with the interference to null the interference and facilitate reception of the desired signal.
The above discussion/summary is not intended to describe each embodiment or every implementation of the present disclosure. The figures and detailed description that follow also exemplify various embodiments.
Various example embodiments may be more completely understood in consideration of the following detailed description in connection with the accompanying drawings, in which:
While various embodiments discussed herein are amenable to modifications and alternative forms, aspects thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure including aspects defined in the claims. In addition, the term “example” as used throughout this application is only by way of illustration, and not limitation.
Aspects of the present disclosure are believed to be applicable to a variety of different types of apparatuses, systems and methods involving wireless communications. While not necessarily so limited, various aspects may be appreciated through a discussion of examples using this context.
Various example embodiments are directed to wireless communications involving the use of multiple antennas, with beam steering that facilitates reception (e.g., relative to noise or other unwanted signals). In a particular implementation, a radiation-pattern of a multiple receiver-antenna is electronically steered for receiving signals. The steering is accomplished in a variety of manners. For instance, steering can be based on solely (e.g., estimated) phase-shifts, or upon a combination of (e.g., estimated) phase-shifts and (e.g., estimated) amplitudes of multiple received-signals on multiple antennas. As may be characterized in one or more embodiments, steering a radiation-pattern with phase-estimations alone is referred to (digital) phase diversity, and steering a radiation-pattern with both phase estimations and amplitude estimations is referred to as (digital) beamforming. Antennas may, for example, be electronically steered in this regard using phase estimators to provide each antenna with a phase-value, such that each element in the array gets a computed phase-shift.
Various signals can be processed as discussed herein. In various embodiments, an orthogonal frequency-division multiplexing (OFDM) signal having a central portion that is centered on a carrier frequency, a lower sideband below the lowest frequency of the central portion and an upper-sideband above the highest frequency of the central portion. In more particular embodiments, (H)IBOC signals are processed in this regard. The term (H)IBOC as discussed herein refers to an IBOC signal that can be in hybrid or all-digital form. Such approaches can be implemented for the transmission of digital radio and analog radio broadcast signals simultaneously on a common frequency, and/or with a digital approach in which two digital signals are combined.
For hybrid signals including both analog and digital portions, an analog central portion of the received signal is used to perform straightforward and low latency phase-diversity and beamforming. Phase and amplitude-estimations are used to improve reception of the digitally-modulated sidebands without necessarily demodulating them. In some embodiments involving a digital mode, a null-steering approach is implemented. Electronic steering can be used for a receiver antenna in this regard to improve one or more of the suppression of distortion (e.g., a first-adjacent FM-distortion), received signal-power and, the reception quality of a desired signal.
Consistent with various embodiments, beamforming facilitates what may be referred to as a null-steering approach, for suppressing (or removing) interference such as first-adjacent FM-distortions in a hybrid mode and in an all-digital mode. Such an approach may be implemented using co-channel interference cancellation. Further, an analog central portion of an (H)IBOC-signal can be used to perform the phase-diversity and beamforming based on a (host) FM-signal. Phase and amplitude-estimations can also be used to apply main-lobe steering (phase-diversity) and null-steering (beamforming) for improved reception of digitally-modulated sidebands without actually demodulating the signals.
For general information regarding communication approaches, and for specific information regarding communication aspects that may be implemented with one or more embodiments, reference may be made to the in-band on-channel digital radio broadcasting standard for the FM-band defined by the FM-part of the NRSC-5 standard “National Radio Systems Committee (NRSC) NRSC-5-C, ‘In-band/on-channel Digital Radio Broadcasting Standard’, September, 2011”; and to “HD Radio™ Air Interface Design Description Layer 1 FM”, Doc. No.: SY_IDD—1011sG Rev. G, Aug. 23, 2011, which are fully incorporated herein by reference. Approaches as described therein may be implemented for transmitting IBOC signals as discussed herein, and as may be implemented with high definition radio broadcasting. One type of IBOC signal is the so-called “Hybrid IBOC FM” signal, which may be referred to as “Hybrid IBOC.”
A variety of signal types may be received and processed in accordance with various example embodiments. In some embodiments, hybrid signals that are a combination/addition of an analog FM-signal and a digitally-modulated signal are received, where the analog FM-signal occupies a bandwidth of 200 kHz (i.e., between −100 kHz and +100 kHz separated from the carrier-frequency), and the digitally-modulated signal occupies a bandwidth of roughly 200 kHz and is separated into a lower sideband and an upper-sideband having a bandwidth of roughly 100 kHz. The lower sideband is spectrally positioned at a distance of 100 kHz below the carrier-frequency. The upper side-band is spectrally positioned at a distance of 100 kHz above the carrier-frequency. The total power of the digitally-modulated signal is approximately a factor of hundred smaller than the power of the analog host-FM-signal. The hybrid IBOC signal can be seen as a sort of noisy FM-signal.
In various embodiments, the digitally-modulated signal uses OFDM, where the number of subcarriers can vary depending on the selected service/transmission-mode. The so-called “channel-grid” (the reserved channel-bandwidth for an analog FM-signal) is 200 kHz. As a consequence, the lower and upper digital OFDM-sidebands are using the 1st-adjacent lower and upper neighboring FM channels. Another type of IBOC signal is an all-digital implementation. For the all-digital IBOC FM-signal, the analog FM-signal is replaced by a (secondary) digitally-modulated signal. In the all-digital mode the bandwidth of the primary digital sidebands is fully expanded with lower-power secondary sidebands. For the all-digital IBOC signal, the bandwidth may be roughly 400 kHz, where approximately 100 kHz of lower and upper adjacent channels are occupied (outside the 200 kHz “channel-grid”). The number of extended frequency partitions may, for example, be 0, 1, 2, or 4 depending on the transmitted service mode.
Various embodiments are directed toward beamforming and phase-diversity approaches that combine received radio signals that originate from multiple small non-directional antennas in such a way that a large directional antenna can be simulated. This large simulated directional antenna can be pointed in an electronic way, without moving physically. For reception of signals such as (H)IBOC signals, beamforming is used to point the antenna at the desired signal-source to reduce interference and improve reception quality by “collecting” more signal-power of the desired signal. For general information regarding these approaches, and for specific information regarding approaches that may be implemented in connection with one or more embodiments herein, reference may be made to “A Primer on Digital Beamforming,” Toby Haynes, Spectrum Signal Processing, Mar. 26, 1998, which is fully incorporated herein by reference.
In connection with a more particular embodiment, and as may be implemented in accordance with one or more aspects of
In some embodiments, a central portion of the received radio signals is used to electronically direct the receive antennas at the signal source, based on estimated phase-shifts or estimated amplitude of the received signals. FM-distortions are suppressed by nulling interference in the radio signals based on lower and upper interference sidebands of the radio signals that are adjacent the central portion of the radio signals.
In various embodiments, hybrid in-band on-channel ((H)IBOC) signals are processed. In some implementations, the (H)IBOC signals have a desired signal in a central frequency range, an upper interference signal occupying a frequency range including and extending beyond an upper portion of the central frequency range, and a lower interference signal occupying a frequency range including and extending below a lower portion of the central frequency range. The lower and upper interference signals are nulled by generating surrogate signals from the desired signal, from the upper interference signal and from the lower interference signal. The antennas are electronically directed based on the surrogate signals and the interference signals, which can be used to null the interference signals.
In another implementation involving (H)IBOC signals, a central digitally modulated portion of the received radio signals having a bandwidth of roughly 600 kHz is captured, using approximately 100 kHz of lower and upper sidebands adjacent the central portion to electronically direct the receive antennas and null interference characteristics of the lower and upper sidebands. In another implementation, (H)IBOC signals having plurality of channels are processed, and co-channel interference of the (H)IBOC signals is cancelled by removing 1st adjacent FM-distortions from adjacent channels of the (H)IBOC signals. In yet another implementation with (H)IBOC signals that include a plurality of channels, co-channel interference is cancelled by removing 1st adjacent FM-distortions in a first mode, and a radiation pattern of the receive antennas is modified in the second mode based on at least one of the estimated phase-shifts and the estimated amplitude.
In some embodiments, an analog central portion of received signals is used to perform low latency phase-diversity and beamforming of the received radio signals, based on a host FM-signal. Main-lobe steering and null-steering of the antennas is carried out in this regard, based on the phase and amplitude-estimations. Such approaches may, for example, be implemented in a manner commensurate with that shown in
In a particular embodiment the captured signals have a desired signal in a central frequency range, and both upper and lower interference signals. The upper interference signal occupies a frequency range including and extending beyond an upper portion of the central frequency range. The lower interference signal occupies a frequency range including and extending below a lower portion of the central frequency range. The lower and upper interference are nulled as follows. Surrogate signals are filtered from the desired signal, from the upper interference signal and from the lower interference signal. Each surrogate signal occupies a frequency range that is centered on and smaller than the signals from which the surrogate signal is filtered. The antennas are electronically directed in at least one of the first and second modes as discussed above, based on the surrogate signals and the interference signals. The upper and lower interference signals are nulled via null-steering to the respective upper and lower interference signals, based upon the surrogate signals for the upper and lower interference signals. Using this approach, reception of the desired signal is facilitated.
Another embodiment is directed to an apparatus including a signal source that transmits in-band on-channel (H)IBOC signals, two or more antennas that receive the (H)IBOC signals, a steering circuit and a combining circuit. The steering circuit electronically directs the antennas in a first (analog-type) mode toward the signal source using an analog portion of the received (H)IBOC signals to modify a radiation pattern of the receive antennas, based on at least one of estimated phase-shifts and estimated amplitude of the received (H)IBOC signals. In a second (digital-type) mode, a digitally-modulated portion of the received (H)IBOC signals is used to electronically direct the receive antennas at the signal source by modifying the radiation pattern of the receive antennas based on at least one of estimated phase-shifts or estimated amplitude of the received signals. The signals via the electronically-directed antenna are combined and provided to a radio receiver. In some implementations, four or more such antennas may be implemented and steered accordingly. Steering may involve, for example, performing low latency phase-diversity and beamforming based on a host FM-signal, and thereby applying main-lobe steering and null-steering based on the phase shift and amplitude-estimations. Further, null-steering may be implemented as discussed above, with the use of surrogates and interference signals for nulling the interference (e.g., removing 1st adjacent interference FM-signals).
Turning now to the figures,
The output of the respective antenna circuits 130, 132, 134 and 136 is provided to a summation network 140, which combines the signals from the respective antennas 110, 112, 114 and 116 to provide a combined (added) signal having a power greater than that of the individual antennas. The combined signal is provided as an output to radio receiver 150.
The various embodiments described herein may be combined in certain embodiments, and various aspects of individual embodiments may be implemented as separate embodiments. For instance, aspects of
Using such an approach, the suppression or removal of interference such as the 1st adjacent FM-distortions of a signal, as well as improvement of received signal-power of a desired signal that is transmitted in the hybrid-mode as well as in an all-digital mode, can be achieved. Phase-diversity and beamforming can be used to electronically steer a radiation pattern of multiple receive-antennas for transmitted (H)IBOC signals' patterns. In some implementations, electronically steering of a radiation-pattern is specifically based on an analog central-part of IBOC-signals transmitted in the hybrid-mode and, in an all-digital mode, is based on a digitally-modulated central-part of the IBOC-signals. The analog central-part of an (H)IBOC-signal can be used to perform straightforward and low latency phase-diversity and beamforming based on a (host) FM-signal. Thereby, the phase and amplitude-estimations can be also used to apply main-lobe steering (phase-diversity) and null-steering (beamforming) for improved reception of the digitally-modulated (OFDM-signals) sidebands without actually demodulating the OFDM-signals. In the all-digital mode, null-steering can be used to suppress 1st adjacent FM-distortions.
For beamforming with null-steering, a portion of a roughly 100 kHz wide (frequency-bin of 100 kHz) is used to obtain surrogates (representatives) for the desired-((H)IBOC)-signal, the lower 1st adjacent interference-signal, and the upper 1st adjacent interference-signal. The surrogate of the desired-signal is obtained in the frequency-bin around zero Hertz (0 kHz) between −50 kHz and +50 kHz. The surrogate of the lower 1st adjacent interference-signal is obtained in the frequency-bin around −250 kHz between −200 kHz and −300 kHz. The surrogate of the upper 1st adjacent is obtained in the frequency-bin around +250 kHz between +200 kHz and +300 kHz.
The surrogates of the desired signal and the interference signals are used in a beam-forming algorithm, which calculates/estimates the weights that maximize the signal to interference-plus-noise ratio (SINR), such as may be implemented with
Various blocks, modules or other circuits may be implemented to carry out one or more of the operations and activities described herein and/or shown in the figures. In these contexts, a “block” (also sometimes “logic circuitry” or “module”) is a circuit that carries out one or more of these or related operations/activities (e.g., beamformer, surrogate-generating or null-steering modules). For example, in certain of the above-discussed embodiments, one or more modules are discrete logic circuits or programmable logic circuits configured and arranged for implementing these operations/activities, as in the circuit modules shown in
Certain embodiments are directed to a computer program product (e.g., nonvolatile memory device), which includes a machine or computer-readable medium having stored thereon instructions which may be executed by a computer (or other electronic device) to perform these operations/activities.
Based upon the above discussion and illustrations, those skilled in the art will readily recognize that various modifications and changes may be made to the various embodiments without strictly following the exemplary embodiments and applications illustrated and described herein. For example, various aspects may be directed to using an analog-based mode without a digital mode, or using a digital mode without an analog mode. Certain embodiments described involving a particular type of signal maybe implemented with other types of signals. Further, additional antennas may be used to suit various applications. Such modifications do not depart from the true spirit and scope of various aspects of the invention, including aspects set forth in the claims.
