Patent Publication Number: US-2020304215-A1

Title: Dispersion compensation for electromagnetic waveguides

Description:
BACKGROUND 
     As more devices become interconnected, and users consume more data, the demand on servers to supply that data has increased. Among other issues, these demands may include increased data rates, switching architectures with longer interconnects, interconnects with low raw bit-error-rates, interconnects with relatively low latency, lower cost, or lower-power solutions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts an example architecture that includes dispersion compensation, in accordance with various embodiments. 
         FIG. 2  depicts an alternative example architecture that includes dispersion compensation, in accordance with various embodiments. 
         FIG. 3  depicts an alternative example architecture that includes dispersion compensation, in accordance with various embodiments. 
         FIG. 4  depicts an alternative example architecture that includes dispersion compensation, in accordance with various embodiments. 
         FIG. 5  depicts an example dispersion compensation module, in accordance with various embodiments. 
         FIG. 6  depicts examples of group-delay in an architecture that includes dispersion compensation, in accordance with various embodiments. 
         FIG. 7  is a block diagram of an example electrical device that may include dispersion compensation in accordance with various embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings which form a part hereof, wherein like numerals designate like parts throughout, and in which is shown by way of illustration embodiments in which the subject matter of the present disclosure may be practiced. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. Therefore, the following detailed description is not to be taken in a limiting sense. 
     For the purposes of the present disclosure, the phrase “A or B” means (A), (B), or (A and B). For the purposes of the present disclosure, the phrase “A, B, or C” means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C). 
     The description may use the phrases “in an embodiment,” or “in embodiments,” which may each refer to one or more of the same or different embodiments. Furthermore, the terms “comprising,” “including,” “having,” and the like, as used with respect to embodiments of the present disclosure, are synonymous. 
     The term “coupled with,” along with its derivatives, may be used herein. “Coupled” may mean one or more of the following. “Coupled” may mean that two or more elements are in direct physical or electrical contact. However, “coupled” may also mean that two or more elements indirectly contact each other, but yet still cooperate or interact with each other, and may mean that one or more other elements are coupled or connected between the elements that are said to be coupled with each other. The term “directly coupled” may mean that two or elements are in direct contact. 
     Various operations may be described as multiple discrete operations in turn, in a manner that is most helpful in understanding the claimed subject matter. However, the order of description should not be construed as to imply that these operations are necessarily order dependent. 
     As used herein, the term “module” may refer to, be part of, or include an application-specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) or memory (shared, dedicated, or group) that execute one or more software or firmware programs, a combinational logic circuit, or other suitable components that provide the described functionality. 
     As noted, demand for increased server performance may create various interconnect-related demands. For medium range (e.g., between approximately 1 and approximately 5 meter (m) long) transmission in servers or high-performance computers, dielectric waveguides operating in the millimeter-wave (mmWave), sub-terahertz (THz), or greater, frequency range may be capable of providing performance or cost advantages versus optical or electrical interconnect fabrics. As used herein, mmWave may refer to electromagnetic signals with a frequency between approximately 30 gigahertz (GHz) and approximately 300 GHz. Sub-THz may refer to electromagnetic signals with a frequency between approximately 300 GHz and approximately 1 THz. Generally, embodiments herein may relate to communications systems that propagate electromagnetic signals with a frequency greater than approximately 30 GHz along a waveguide. 
     The desired data rate at mmWave frequencies or above may be achieved by taking advantage of the available frequency bandwidth. For example, a radio or transceiver operating over a 40 GHz bandwidth from approximately 100 GHz to approximately 140 GHz may deliver data rates of up to 56 gigabits per second (Gbps) with a quadrature phase-shift keying (QPSK) modulation scheme. The same radio may deliver over 100 Gbps over the same frequency range if a quadrature amplitude modulation-16 (QAM16) modulation scheme is used. In radio-over-waveguide applications, a waveguide operating over a broad frequency range may experience significantly different group-delay response as a function of the frequency over medium to long transmission ranges (e.g., between approximately 1 and approximately 10 m). This chromatic dispersion may inherently result in intersymbol interference (ISI) as digital signals carried on different wavelengths may travel at different speeds on the same waveguide. 
     More specifically, embodiments herein may relate to intermediate-frequency (IF) dispersion compensation (DC) architecture for medium-long reach (e.g., approximately 1-5 m long) mmWave or above waveguide channels. The DC may be based on cascaded low-order allpass filters (APFs) with a resonant group-delay response. Embodiments of the DC herein may operate at an IF that is lower than the waveguide channel frequency, which may enable low-loss, accurate filters, and efficient re-amplification if needed. Embodiments herein may further equalize an in-phase (I) and a quadrature (Q) channel, which may typically be viewed as a 4-port system, using a single 2-port analog circuit. 
     Embodiments may provide a number of advantages. One such advantage may be that the I/Q channel may be equalized using a single 2-port circuit. In legacy systems, at baseband, equalization may have required four 2-port circuits to implement a 2×2 transfer matrix. Therefore, embodiments may allow for simplified and cost-efficient manufacturing. Embodiments may also provide increased flexibility. Specifically, implementation of embodiments herein may be based on a cascade of APFs that allow compensation of channels with arbitrary dispersion. Embodiments may also allow for low-power, inherently wideband, negligible latency interconnects and are independent on the employed modulation (e.g., pulse-amplitude modulation (PAM)4, PAM8, phase-shift keying (PSK)8, QPSK, QAM16, QAM64, etc.). 
       FIG. 1  depicts an embodiment that may include DC implemented at an IF. Specifically,  FIG. 1  depicts an example architecture that includes DC, in accordance with various embodiments. Generally, it will be understood that  FIG. 1 , and other Figures herein, are intended as high-level examples for the purpose of illustrating and discussing various concepts of the present disclosure. Real-world embodiments may include more or fewer elements than are depicted in  FIG. 1 . For example, in some embodiments additional active or passive circuitry may be present, or certain elements such as various of the local oscillators may not be present. Other variations may be present in other embodiments. 
     Generally,  FIG. 1  depicts a communication architecture which may include a transmit module  100  and a receive module  105  that are communicatively coupled by a waveguide  145 . Although the transmit and receive modules  100 / 105  are discussed herein as communicating in a single direction, it will be understood that in other embodiments one or both of the transmit module  100  or receive module  105  may include elements, components, or circuitry that enable bidirectional communication with both transmit and receive functionality. That is, in other embodiments one or more of both the transmit or receive modules  100 / 105  may be referred to as a transceiver module. 
     The transmit module  100  may include a number of signal inputs  115   a  and  115   b.  The signal inputs  115   a / 115   b  may be configured to receive a signal from an active element of an electronic device of which the transmit module  100  is a part. Such an active element may be a processor such as a central processing unit (CPU), a graphics processing unit (GPU), a field programmable gate array (FPGA), a core of a multi-core processor, a memory, a serializer, or some other element of the electronic device. In some embodiments, the signal inputs  115   a / 115   b  may be configured to receive the data signal from the same active element of the electronic device, while in other embodiments the signal input  115   a  may receive the data signal from a different active element than signal input  115   b.  In some embodiments, the data signal input to signal input  115   a  may be referred to as the in-phase or “I” signal, and the data signal input to signal input  115   b  may be referred to as the quadrature or “Q” signal (or vice-versa in other embodiments). 
     The data signals from the signal inputs  115   a / 115   b  may be input to a baseband module  110  which may be configured to perform baseband processing on the first and second data signals. Generally, the baseband processing may include amplification, attenuation, filtering, time delays for skewing/de-skewing, or some other form of pulse shaping performed by digital or analog circuits to improve signal integrity or deliver the right power levels to subsequent circuits. Baseband processing may further include serialization/deserialization circuitry and modulation-demodulation circuitry (modem). Typically, the baseband module  100  may be hardware, software, firmware, circuitry, logic, or some other component, element, or combination of elements which may be configured to perform the modulation function or other functions described herein. 
     The data signals may be input to mixers which may change the frequency of the data signals to an IF by multiplying it with local oscillators (LOs), as described above. The specific LOs are not depicted in the Figures herein for the sake of lack of clutter and redundancy of the Figure. In some embodiments, the LOs coupled with mixers  120   a  and  120   b  may be in quadrature (i.e., have a phase difference of approximately 90 degrees), which may allow the signals to be combined later by a combiner such as combiner  125  through addition without incurring loss of information. 
     Specifically, the data signals received at the signal inputs  115   a / 115   b  may have a frequency bandwidth that is referred to as a “baseband bandwidth,” which may be on the order of between approximately 1 and approximately 50 GHz. Additionally, as described above, the electromagnetic signal sent through waveguide  145  may be a mmWave signal or higher with a frequency higher than approximately 30 GHz. The mixers  120   a / 120   b  may change the frequency of the data signal(s) to an IF that is between the baseband bandwidth and the frequency of the electromagnetic signal. In some embodiments, the IF may be on the order of 10-30 GHz. However, it will be understood that in other embodiments the IF may be higher or lower, dependent on factors such as the frequency of the electromagnetic signal within the waveguide  145  and the baseband bandwidth. At a high level, the frequency of the IF may be dependent on the bandwidth of the baseband signal, as well as the radio frequency (RF) module frequency. In some embodiments, the IF may be as low as approximately 10 GHz, while in other embodiments the IF may be greater than approximately 100 GHz for sub-THz applications where the RF is above 300 GHz. Generally, it will be desirable for the IF to be higher than the baseband bandwidth. 
     In terms of signal integrity, it is may be desirable for the IF to be much lower than the frequency of the electromagnetic signal because circuits may tend to present lower loss and therefore may be targeted more accurately. In the specific case of allpass filters, loss may be directly proportional to frequency for a given group-delay. For example, in some embodiments: 
     
       
         
           
             
               
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     where Q is the overall intrinsic quality factor of the circuit. On the other hand, operating at lower frequency may imply larger passive components, potentially increasing cost and making integration more difficult. Such trade-offs may be evaluated for each application and system architecture. 
     The frequency-shifted data signals may then be output from the mixers  120   a / 120   b  to a combiner  125  which may combine the signals to form a combined I/Q signal as described above 
     The combined I/Q signal may then be input to a DC module  130 . The DC module  130  may be configured to mitigate dispersion of the electromagnetic signal as it propagates along the waveguide  145  in the mmWave or higher frequency. As may be described in greater detail with respect to  FIGS. 5 and 6 , the DC module  130  may be implemented as a series of cascaded or serially-connected APFs. 
     The signal may then be output from the DC module  130  to another mixer  135 , where the signal may be upconverted to a frequency in the mmWave or greater range. The signal with the mmWave or greater frequency range may be provided to an RF module  140  which may be configured to amplify and filter the incoming mmWave signal. The RF module  140  may be hardware, software, firmware, circuitry, logic, or some other component, element, or combination of elements which may be configured to perform the modulation function or other functions described herein. 
     The RF module  140  may then facilitate transmission of the electromagnetic signal through a waveguide such as waveguide  145 . The waveguide  145  may be, for example, a silicon waveguide, a metallic-clad dielectric waveguide, a dielectric-clad dielectric waveguide, a dielectric hollow or air-filled waveguide, or some other type of waveguide. In some embodiments, the waveguide  145  may be between approximately 2 and approximately 5 meters long, while in other embodiments the waveguide may be longer or shorter. It will be understood that although  FIG. 1  (and other Figures herein) depict only a single RF module  140  of a single transmit module  100  communicatively coupled with the waveguide  145 , in other embodiments a plurality of RF modules or a plurality of transmit module may be communicatively coupled with the waveguide  145 . 
     The electromagnetic signal may be received from the waveguide  145  by a receive module  105 , which may include a number of elements that are similar to those of the transmit module. Particularly, the receive module may include a RF module  150  which may be configured to amplify the received modulated electromagnetic signal to produce a recovered mmWave signal which is then output to a mixer  155  which may be configured to change (i.e., downconvert) the frequency of the signal to an IF. In some embodiments, the IF produced by mixer  155  may be the same as the IF produced by mixers  120   a  and  120   b,  that is, the transmit and receive modules  100 / 105  may have the same IF. In other embodiments, the transmit and receive modules  100 / 105  may have different IFs. The frequency-shifted signal may be provided to a splitter  160  which may separate the first data signal (e.g., the I signal) from the second data signal (e.g., the Q signal). The first and second data signals may be provided to mixers  165   a / 165   b  which may frequency-shift the signals to a baseband frequency that is similar to the baseband frequency described with respect to transmit module  100 , and the first and second data signals (with the baseband frequencies) may be output to baseband module  168 , which may be generally similar to baseband module  110 . The baseband module  168  may be configured to perform equalization, serialization/deserialization, amplification, etc. The first and second data signals may then be output by the baseband module  168  to signal outputs  170   a / 170   b . Specifically, signal outputs  170   a / 170   b  may be communicatively coupled with one or more elements of an electronic device of which the receive module  105  is a part such as a processor, a processor core, a memory, etc. 
     Generally, in embodiments, the presence of the DC module  130  may provide a number of advantages. For example, the DC module  130  may reduce or eliminate crosstalk between the I signal and the Q signal at the baseband module  110 , compensate group-delay dispersion in the waveguide, etc. Embodiments may also allow for a relatively flat amplitude response in the mmWave electromagnetic signal at bandwidths up to approximately 10 GHz, which may be a significant increase in bandwidth compared to legacy architectures which may only exhibit a flat amplitude response in the mmWave electromagnetic signal up to approximately 4 GHz. More generally, embodiments herein may extend the useful baseband bandwidth y a factor ranging from approximately 2× to approximately 10×, depending on how many APFs may be included in the DC module  130  (as described in greater detail below). In some embodiments, it may be possible to use more APFs, or higher-order APFs, to compensate for more dispersion, enabling wider baseband bandwidths and, therefore, higher data rates. 
     Embodiments may further allow for compensated group-delay dispersion of the mmWave electromagnetic signal, which may result in relatively constant group-delay in bandwidths up to approximately 10 GHz. Additionally, in some embodiments, further baseband equalization may not be necessary. It will be understood that embodiments herein may further be scalable to different waveguides with different dispersion characteristics. 
     In embodiments herein it may be understood that, contrary to the baseband where destructive I/Q interference may occur, waveguide dispersion may be seen “as is” by IF frequencies in situations where the IF LO frequency is larger than the baseband bandwidth. Moreover, because the amplitude response of the waveguide  145  may be considered to be nearly flat, ideally little-to-no amplitude equalization may be required once dispersion is compensated. Because of this, the channel may be equalized with a single two-port analog circuit. 
       FIGS. 2-4  depict alternative example architectures which may include DC, in accordance with various embodiments. Generally, each of the architectures may include elements similar to those of the architecture of  FIG. 1 . However, in various of the architectures, the DC may be located in a different portion of the signal path between the baseband modules  110 / 168 . For example,  FIG. 2  may include transmit and receive modules  200  and  205 , which may be respectively similar to transmit and receive modules  100  and  105 . However, as may be seen, rather than placing the DC module in the signal path of the transmit module  200 , the DC module  230  (which may be similar to DC module  130 ) may be placed in the signal path of the receive module  205 . Specifically, the DC module  230  may be positioned between mixer  155  and splitter  160 , as shown in  FIG. 2 . 
     Similarly,  FIG. 3  depicts an architecture that includes transmit and receive modules  300  and  305 , which may be respectively similar to transmit and receive modules  100  and  105 . However, as may be seen, the DC module may be in the signal path of both the transmit module  300  and the receive module  305 . Specifically, as may be seen, a first DC module  330   a  (which may be similar to DC module  130 ) may be positioned in the signal path of the transmit module  300  between the combiner  125  and the mixer  135 . Additionally, a second DC module  330   b  (which may also be similar to DC module  130 ) may be positioned in the signal path of the receive module  305  between the mixer  155  and the splitter  160 . 
     Similarly,  FIG. 4  depicts an architecture that includes transmit and receive modules  400  and  405 , which may be respectively similar to transmit and receive modules  100  and  105 . However, transmit module  400  may include two separate DC modules  430   a  and  430   b , which may be respectively similar to DC module  130 . As may be seen, the DC modules  430   a  and  430   b  may be in the signal paths of the first and second data signals. That is, DC module  430   a  may be positioned between mixer  120   a  and combiner  125 , and DC module  430   b  may be positioned between mixer  120   b  and combiner  125 . 
     Generally, it will be understood that  FIGS. 1-4  are intended as example architectures, and other embodiments may vary. For example, some embodiments may include a combination of a transmit module such as transmit module  400  with a receive module such as receive module  200 . In some embodiments, DC modules may be positioned between splitter  160  and mixers  165   a / 165   b.  In some embodiments, a single DC module may span both of the signal paths between mixers  120   a / 120   b  and splitter  125 . Other embodiments may include other variations. 
       FIG. 5  depicts an example DC module  530 , in accordance with various embodiments. The DC module  530  may be similar to, for example, DC module  130  described above. Generally, the DC module  530  may include a plurality of filters such as APFs  575 . Although only 4 APFs  575  are depicted in  FIG. 5 , in other embodiments a DC module  530  may have more or fewer APFs. The connections of the APFs  575  may be referred to as “cascaded” or “serially-coupled.” In some embodiments, the DC module  530  may further include a gain equalizer  580 , which may reduce or eliminate insertion loss in the APFs  575  due to finite quality factor or process variations. However, in other embodiments the gain equalizer  580  may not be present. 
     Typically, APFs may have a unitary amplitude response for almost all frequencies, and a group-delay response which may be specified, within certain constraints given by the filter order.  FIG. 6  may depict how a cascade of second-order APFs, whose individual group-delay response shows a resonant peak at the design frequency, may be used to implement arbitrary dispersion-frequency curves. Specifically,  FIG. 6  may depict an example at  600  of group-delay using a number of individual APFs. Specifically, in the example  600 , a number of group-delay response curves  615  may be shown, which may correspond to individual ones of the APFs  575 . The example  600  may further depict an overall group-delay curve  610  for an entire DC module such as DC module  530 . 
       FIG. 6  may further depict an example  605  that depicts the total group-delay of an architecture such as the architecture of  FIG. 1 . Curve  620  may depict the group-delay without the presence of a DC module such as DC module  530 , and curve  625  may depict the group-delay with the presence of a DC module such as DC module  625 . As may be seen, the dashed vertical lines in examples  600  and  605  may represent the bandwidth of operation for the architecture, which may be significantly increased with the presence of the DC module as may be seen by comparing lines  620  and  625 . Specifically, as may be seen at  620 , in legacy embodiments the group-delay of the waveguide may decrease with a change in frequency (i.e., increasing or decreasing frequency). However, as may be seen at  625 , embodiments may equalize, over a finite bandwidth delimited by the dashed lines in examples  600 / 605  the group-delay. 
     To achieve this equalization, the staggered peaks of the lines at  615  may be designed to have larger peak delay with increasing frequency, resulting in the total DC group-delay depicted at  610 . Additionally, as may be seen at example  605 , the overall group-delay may be seen as generally independent of frequency, which may help prevent dispersion-induced ISI, transmission nulls, or I/Q crosstalk when down-conversion of the frequency to the baseband frequency occurs (e.g., by mixers  165   a / 165   b ). It will be understood that, although second-order APFs are discussed herein, embodiments may be extended to APFs with a higher or lower order, whether used as a cascadable block in a DC module such as DC module  530 , or as a DC of their own. More generally, in some embodiments, respective ones of the APFs  575  of the DC module  530  may be of a different order than another of the APFs  575 . 
     Additionally, it will be noted that embodiments or concepts herein may be applied to architectures that include waveguides with either normal (where group-delay increases with frequency) or anomalous (where group-delay decreases with frequency) dispersion. Generally, the amount of APFs with a DC module, or number of DC modules themselves, may be based on the amount of dispersion that is to be compensated for. Generally, embodiments may allow for modularity and reusability, and may be modulation-agnostic such that the design of the DC modules may be similar for different modulation schemes such as QPSK, QAM16, QAM64, etc. 
     APFs such as APFs  575  may be implemented in a variety of designs. For example, one or more of the APFs  575  may be a passive lumped circuit, an active lumped circuit, a distributed structure, etc. In some embodiments, the APFs  575  may be implemented as a circuit that includes a number of resistors, capacitors, transistors, etc. In some embodiments, one or more of the elements of the circuit may be tunable, that is, the resistance/capacitance/etc. may be variable and set by other control circuitry of the transmit or receive modules, or the electronic device of which the transmit or receive modules are a part. In some embodiments, the control circuitry may be configured to turn on, or off, certain of the APFs within a DC module so that the overall group-delay of the DC module may be changed dynamically based on characteristics of the overall architecture or the waveguide. In some embodiments, the control circuit may dynamically (i.e., on-the-fly) evaluate the received signal quality and accordingly adapt/control/tune APFs of DC modules of the transmit module or receive module. 
     In some embodiments, circuitry or parameters of various of the APFs may be mapped to group-delay peaks such as those depicted at  615  in  FIG. 6 , relating peak frequency or height to physical parameters of the circuitry of the APFs. The structures related to the APFs may then be designed as part of the transmit or receive modules of which they are a part. In some embodiments, the structures may be designed to operate at the mmWave frequency or above, however such operation may incur high insertion loss because loss may scale linearly with frequency for a specified group-delay. 
       FIG. 7  is a block diagram of an example electrical device  1800  that may include one or more DC modules, in accordance with any of the embodiments disclosed herein. A number of components are illustrated in  FIG. 7  as included in the electrical device  1800 , but any one or more of these components may be omitted or duplicated, as suitable for the application. In some embodiments, some or all of the components included in the electrical device  1800  may be attached to one or more motherboards. In some embodiments, some or all of these components are fabricated onto a single system-on-a-chip (SoC) die. 
     Additionally, in various embodiments, the electrical device  1800  may not include one or more of the components illustrated in  FIG. 7 , but the electrical device  1800  may include interface circuitry for coupling to the one or more components. For example, the electrical device  1800  may not include a display device  1806 , but may include display device interface circuitry (e.g., a connector and driver circuitry) to which a display device  1806  may be coupled. In another set of examples, the electrical device  1800  may not include an audio input device  1824  or an audio output device  1808 , but may include audio input or output device interface circuitry (e.g., connectors and supporting circuitry) to which an audio input device  1824  or audio output device  1808  may be coupled. 
     The electrical device  1800  may include a processing device  1802  (e.g., one or more processing devices). As used herein, the term “processing device” or “processor” may refer to any device or portion of a device that processes electronic data from registers and/or memory to transform that electronic data into other electronic data that may be stored in registers and/or memory. The processing device  1802  may include one or more digital signal processors (DSPs), ASICs, CPUs, GPUs, cryptoprocessors (specialized processors that execute cryptographic algorithms within hardware), server processors, or any other suitable processing devices. The electrical device  1800  may include a memory  1804 , which may itself include one or more memory devices such as volatile memory (e.g., dynamic random-access memory (DRAM)), nonvolatile memory (e.g., read-only memory (ROM)), flash memory, solid state memory, and/or a hard drive. In some embodiments, the memory  1804  may include memory that shares a die with the processing device  1802 . This memory may be used as cache memory and may include embedded dynamic random-access memory (eDRAM) or spin transfer torque magnetic random-access memory (STT-MRAM). 
     In some embodiments, the electrical device  1800  may include a communication chip  1812  (e.g., one or more communication chips). For example, the communication chip  1812  may be configured for managing wireless communications for the transfer of data to and from the electrical device  1800 . The term “wireless” and its derivatives may be used to describe circuits, devices, systems, methods, techniques, communications channels, etc., that may communicate data through the use of modulated electromagnetic radiation through a nonsolid medium. The term does not imply that the associated devices do not contain any wires, although in some embodiments they might not. 
     The communication chip  1812  may implement any of a number of wireless standards or protocols, including but not limited to Institute of Electrical and Electronics Engineers (IEEE) standards including Wi-Fi (IEEE 802.11 family), IEEE 802.16 standards (e.g., IEEE 802.16-2005 Amendment), Long-Term Evolution (LTE) project along with any amendments, updates, and/or revisions (e.g., advanced LTE project, ultra mobile broadband (UMB) project (also referred to as “3GPP2”), etc.). IEEE 802.16 compatible Broadband Wireless Access (BWA) networks are generally referred to as WiMAX networks, an acronym that stands for Worldwide Interoperability for Microwave Access, which is a certification mark for products that pass conformity and interoperability tests for the IEEE 802.16 standards. The communication chip  1812  may operate in accordance with a Global System for Mobile Communication (GSM), General Packet Radio Service (GPRS), Universal Mobile Telecommunications System (UMTS), High Speed Packet Access (HSPA), Evolved HSPA (E-HSPA), or LTE network. The communication chip  1812  may operate in accordance with Enhanced Data for GSM Evolution (EDGE), GSM EDGE Radio Access Network (GERAN), Universal Terrestrial Radio Access Network (UTRAN), or Evolved UTRAN (E-UTRAN). The communication chip  1812  may operate in accordance with Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Digital Enhanced Cordless Telecommunications (DECT), Evolution-Data Optimized (EV-DO), and derivatives thereof, as well as any other wireless protocols that are designated as 3G, 4G, 5G, and beyond. The communication chip  1812  may operate in accordance with other wireless protocols in other embodiments. The electrical device  1800  may include an antenna  1822  to facilitate wireless communications and/or to receive other wireless communications (such as AM or FM radio transmissions). 
     In some embodiments, the communication chip  1812  may manage wired communications, such as electrical, optical, or any other suitable communication protocols (e.g., the Ethernet). As noted above, the communication chip  1812  may include multiple communication chips. For instance, a first communication chip  1812  may be dedicated to shorter-range wireless communications such as Wi-Fi or Bluetooth, and a second communication chip  1812  may be dedicated to longer-range wireless communications such as global positioning system (GPS), EDGE, GPRS, CDMA, WiMAX, LTE, EV-DO, or others. In some embodiments, a first communication chip  1812  may be dedicated to wireless communications, and a second communication chip  1812  may be dedicated to wired communications. In some embodiments, the communication chip  1812  may include, or be communicatively coupled with, a transmit or receive module such as those discussed herein. 
     The electrical device  1800  may include battery/power circuitry  1814 . The battery/power circuitry  1814  may include one or more energy storage devices (e.g., batteries or capacitors) and/or circuitry for coupling components of the electrical device  1800  to an energy source separate from the electrical device  1800  (e.g., AC line power). 
     The electrical device  1800  may include a display device  1806  (or corresponding interface circuitry, as discussed above). The display device  1806  may include any visual indicators, such as a heads-up display, a computer monitor, a projector, a touchscreen display, a liquid crystal display (LCD), a light-emitting diode display, or a flat panel display. 
     The electrical device  1800  may include an audio output device  1808  (or corresponding interface circuitry, as discussed above). The audio output device  1808  may include any device that generates an audible indicator, such as speakers, headsets, or earbuds. 
     The electrical device  1800  may include an audio input device  1824  (or corresponding interface circuitry, as discussed above). The audio input device  1824  may include any device that generates a signal representative of a sound, such as microphones, microphone arrays, or digital instruments (e.g., instruments having a musical instrument digital interface (MIDI) output). 
     The electrical device  1800  may include a GPS device  1818  (or corresponding interface circuitry, as discussed above). The GPS device  1818  may be in communication with a satellite-based system and may receive a location of the electrical device  1800 , as known in the art. 
     The electrical device  1800  may include another output device  1810  (or corresponding interface circuitry, as discussed above). Examples of the other output device  1810  may include an audio codec, a video codec, a printer, a wired or wireless transmitter for providing information to other devices, or an additional storage device. 
     The electrical device  1800  may include another input device  1820  (or corresponding interface circuitry, as discussed above). Examples of the other input device  1820  may include an accelerometer, a gyroscope, a compass, an image capture device, a keyboard, a cursor control device such as a mouse, a stylus, a touchpad, a bar code reader, a Quick Response (QR) code reader, any sensor, or a radio frequency identification (RFID) reader. 
     The electrical device  1800  may have any desired form factor, such as a handheld or mobile electrical device (e.g., a cell phone, a smart phone, a mobile internet device, a music player, a tablet computer, a laptop computer, a netbook computer, an ultrabook computer, a personal digital assistant (PDA), an ultra mobile personal computer, etc.), a desktop electrical device, a server device or other networked computing component, a printer, a scanner, a monitor, a set-top box, an entertainment control unit, a vehicle control unit, a digital camera, a digital video recorder, or a wearable electrical device. In some embodiments, the electrical device  1800  may be any other electronic device that processes data. 
     EXAMPLES OF VARIOUS EMBODIMENTS 
     Example 1 includes a communications module comprising: a baseband module to process a first data signal with a first frequency; a RF module to facilitate communication of an electromagnetic signal at a second frequency, wherein the electromagnetic signal is related to the data signal; and a dispersion compensation module communicatively coupled between the baseband module and the RF module, wherein the dispersion compensation module is to process a data signal at an intermediate frequency that is between the first frequency and the second frequency. 
     Example 2 includes the communications module of example 1, wherein the dispersion compensation module includes an allpass filter. 
     Example 3 includes the communications module of example 1, wherein the dispersion compensation module includes a plurality of serially-coupled allpass filters. 
     Example 4 includes the communications module of example 1, wherein the dispersion compensation module includes a gain equalizer. 
     Example 5 includes the communications module of any of examples 1-4, wherein the baseband module is to process the first data signal and a second data signal in parallel with the first data signal. 
     Example 6 includes the communications module of example 5, wherein the data signal at the intermediate frequency is based on the first and second data signals. 
     Example 7 includes the communications module of example 5, wherein the dispersion compensation module is communicatively coupled between the baseband module and the combiner. 
     Example 8 includes the communications module of any of examples 1-4, wherein the electromagnetic signal is a millimeter-wave (mmWave) signal. 
     Example 9 includes an electronic device comprising: an active element to process a data signal; and a communications module coupled with the active element, wherein the communications module includes: a baseband module to process a first data signal with a baseband frequency and a second data signal with the baseband frequency; a RF module to facilitate communication of an electromagnetic signal at a second frequency, wherein the electromagnetic signal is based on a combination of the first data signal and the second data signal; and a dispersion compensation module communicatively coupled between the baseband module and the RF module, wherein the dispersion compensation module is to process a data signal at an intermediate frequency that is between the baseband frequency and the second frequency. 
     Example 10 includes the electronic device of example 9, wherein the communications module is a transmit module, and wherein the RF module is to facilitate transmission of the electromagnetic signal along a waveguide. 
     Example 11 includes the electronic device of example 9, wherein the communications module is a receive module, and wherein the RF module is to facilitate reception of the electromagnetic signal from a waveguide. 
     Example 12 includes the electronic device of any of examples 9-11, wherein the electromagnetic signal has a frequency of at least 30 gigahertz (GHz). 
     Example 13 includes the electronic device of any of examples 9-11, wherein the electromagnetic signal has a frequency of at least 300 gigahertz (GHz). 
     Example 14 includes the electronic device of any of examples 9-11, wherein the electromagnetic signal has a frequency of at least 1 terahertz (THz). 
     Example 15 includes a dispersion compensation module comprising: a first allpass filter with a first group-delay response related to a first dispersion characteristic of a communication channel between a baseband module and a RF module of a communications module; and a second allpass filter with a second group-delay response related to a second dispersion characteristic of the communication channel. 
     Example 16 includes the dispersion compensation module of example 15, wherein the baseband module is to process a data signal with a baseband frequency, and the RF module is to process an electromagnetic signal with a frequency greater than 30 gigahertz (GHz). 
     Example 17 includes the dispersion compensation module of example 16, wherein the dispersion compensation module is to process an intermediate signal that is related to the data signal and the electromagnetic signal, and wherein the intermediate signal has a frequency between the baseband frequency and a frequency of the electromagnetic signal. 
     Example 18 includes the dispersion compensation module of example 16, wherein the electromagnetic signal has a frequency greater than 300 GHz. 
     Example 19 includes the dispersion compensation module of any of examples 15-18, wherein the dispersion compensation module further includes a gain equalizer. 
     Example 20 includes the dispersion compensation module of any of examples 15-18, wherein the first and second allpass filters are serially-coupled with one another. 
     Example 21 includes the dispersion compensation module of any of examples 15-18, wherein a characteristic of the first allpass filter is variable based on a characteristic of the communication channel. 
     Various embodiments may include any suitable combination of the above-described embodiments including alternative (or) embodiments of embodiments that are described in conjunctive form (and) above (e.g., the “and” may be “and/or”). Furthermore, some embodiments may include one or more articles of manufacture (e.g., non-transitory computer-readable media) having instructions, stored thereon, that when executed result in actions of any of the above-described embodiments. Moreover, some embodiments may include apparatuses or systems having any suitable means for carrying out the various operations of the above-described embodiments. 
     The above description of illustrated embodiments, including what is described in the Abstract, is not intended to be exhaustive or limiting as to the precise forms disclosed. While specific implementations of, and examples for, various embodiments or concepts are described herein for illustrative purposes, various equivalent modifications may be possible, as those skilled in the relevant art will recognize. These modifications may be made in light of the above detailed description, the Abstract, the Figures, or the claims.