Systems and methods for incorporating millimeter waves (mmwaves) into low frequency wireless devices

Abstract

Systems and methods for incorporating mmWaves into low frequency wireless devices in accordance with embodiments of the invention are illustrated. One embodiment includes a system that can be connected to antenna ports of wireless devices to provide wireless devices with millimeter wave (mmWave) communication over the air capabilities. The system includes at least one RX antenna and at least one TX antenna, where the RX and TX antennas are positioned at a distance from each other and configured to mutually couple with each other to generate a feedback loop, wherein the distance is determined by a desired resonant frequency of a mmWave resonance signal to be generated by the feedback loop, wherein the mmWave resonance signal is mixed with a received low frequency radio frequency (RF) signal to generate a mmWave transmit signal.

Description

Systems and Methods for Incorporating Millimeter Waves (mmWaves) into Low Frequency Wireless Devices CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The current application claims the benefit of and priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 63 / 579,753 entitled “Systems and Methods for Incorporating Millimeter Waves into Wireless Devices” filed August 30, 2023, the disclosure of which is hereby incorporated by reference in its entirety for all purposes. FIELD OF THE INVENTION

[0002] The present invention generally relates to millimeter waves (mmWave) and, more specifically, incorporating mmWave technology into low frequency wireless devices. BACKGROUND

[0003] Millimeter wave (mmWave) is the band of spectrum with wavelengths between 10 millimeters (30 GHz) and 1 millimeter (300 GHz). It is also known as the extremely high frequency (EHF) band. mmWave band may have a low coverage range as it may be affected by the surrounding environment, but it can offer extremely high bandwidth and high speeds for high-speed wireless communications. mmWave has huge potential in applications such as connected vehicles and the Internet of Things (IoT).

[0004] Wireless devices are electronic gadgets designed to connect, share, and interact with other devices and users over a network, typically the Internet. These devices are often equipped with sensors, software, and network connectivity, enabling them to collect and process data and often take actions or make decisions based on that data. They are commonly found in various settings, including homes, workplaces, and as part of wearable technology. Examples of wireless devices include thermostats, lighting systems, speakers, cameras, and even refrigerators.

[0005] Communication between wireless devices can be facilitated through a range of wireless technologies, each operating within specific frequency bands. Wi-Fi, one of the most common methods, operates on the 2.4 GHz and 5 GHz bands and is used for high- speed data transmission over short to medium distances. Other communicationtechnologies include RFID (Radio Frequency Identification), which operates across various frequency bands like 125 kHz, 13.56 MHz, and UHF bands (860-960 MHz) and is used for identification, access control, and inventory management. LoRa (Long Range) technology is designed for long-range, low-power communication in IoT applications, functioning within the 433 MHz, 868 MHz (Europe), and 915 MHz (USA) bands. Their ability to communicate and automate tasks makes them integral to the growing ecosystem of the Internet of Things (IoT). SUMMARY OF THE INVENTION [KPPB to complete when claims are finalized]

[0006] Systems and methods for incorporating mmWaves into low frequency wireless devices in accordance with embodiments of the invention are illustrated. One embodiment includes a system that can be connected to antenna ports of wireless devices to provide wireless devices with millimeter wave (mmWave) communication over the air capabilities. The system includes at least one RX antenna and at least one TX antenna, where the RX and TX antennas are positioned at a distance from each other and configured to mutually couple with each other to generate a feedback loop, wherein the distance is determined by a desired resonant frequency of a mmWave resonance signal to be generated by the feedback loop, wherein the mmWave resonance signal is mixed with a received low frequency radio frequency (RF) signal to generate a mmWave transmit signal.

[0007] In another embodiment, the system includes a diplexer configured to receive the low frequency RF signal from an IoT (Internet of Things) wireless device.

[0008] In a further embodiment, the diplexer includes two ports connected together using a transmission line.

[0009] In still another embodiment, the diplexer further includes a third port having a bow-tie structure that isolates the third port from the feedback loop.

[0010] In a still further embodiment, the system further includes a mixer configured to generate the mmWave transmit signal from the TX antenna by intermodulating the mmWave resonance signal generated by the feedback loop with the received low frequency RF signal.

[0011] In yet another embodiment, the mixer is a low noise amplifier (LNA) that is further configured to modulate a mmWave signal received at the RX antenna and convert the received mmWave signal to a low frequency RF signal.

[0012] In a yet further embodiment, the LNA is driven to resonance based on a noise signal in the system when the attenuation of the noise signal is smaller than the gain of the LNA.

[0013] In another additional embodiment, the LNA resonates at a desired frequency determined based upon the positioning of the RX and TX antennas.

[0014] In a further additional embodiment, the system further includes an RF choke configured to downconvert received mmWave signals to an intermediate frequency (IF) band, an IF amplifier configured to boost the voltage levels of received IF signals, a comparator configured to reduce noise of the received IF signals, and a low power processor to process the received IF signals.

[0015] In another embodiment again, the received low frequency RF signals include radio frequency identification (RFID), Bluetooth Low Energy (BLE), and WiFi signals. In a further embodiment again, the generated mmWave transmit signal is transmitted directionally using directional beams.

[0016] In still yet another embodiment, the loop gain is higher than one.

[0017] In a still yet further embodiment, each of the RX and TX antennas are rectangular in shape comprising two length edges and two width edges.

[0018] In still another additional embodiment, each of the RX and TX antennas has two resonant frequencies, wherein the two resonant frequencies include a main resonant frequency and a secondary resonant frequency.

[0019] In a still further additional embodiment, at the main resonant frequency, the length edge of each of the RX and TX antennas has an electrical field with a sinusoidal distribution and the width edge of each of the RX and TX antennas has an electrical field with uniform distribution.

[0020] In still another embodiment again, each of the RX and TX antennas are positioned such that the width edges of both antennas face each other, and are displaced along the width edges such that, at the main resonant frequency, the peaks and nodes ofthe electric field on each of the RX antenna’s width edge match the peaks and nodes of the electric field of the width edge of each of the TX antenna.

[0021] In a still further embodiment again, each of the RX and TX antennas are positioned such that the coupling is weak at the secondary resonant frequency.

[0022] In yet another additional embodiment, the mutual coupling is reduced by increasing the distance between the RX and TX antennas.

[0023] In a yet further additional embodiment, the number of RX and TX antennas is increased to increase transmission range.

[0024] In yet another embodiment again, the at least one RX antenna receives a modulated mmWave signal from an mmWave access point (AP).

[0025] In a yet further embodiment again, the received mmWave signal is downconverted to a low frequency RF signal by mixing the received mmWave signal with a resonating mmWave signal in the feedback loop.

[0026] One embodiment includes a method for upconverting low frequency RF signals to mmWave signals in wireless devices. The method includes generating a mmWave resonance signal, and receiving a low frequency RF signal from an IoT wireless device. The method further includes intermodulating the generated mmWave resonance signal with the received low frequency RF signal to generate a mmWave transmit signal, and transmitting the mmWave transmit signal.

[0027] Additional embodiments and features are set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the specification or may be learned by the practice of the invention. A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings, which forms a part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The description and claims will be more fully understood with reference to the following figures and data graphs, which are presented as exemplary embodiments of the invention and should not be construed as a complete recitation of the scope of the invention.

[0029] FIG.1 illustrates an implementation of an mmPlug module in a wireless device network in accordance with an embodiment of the invention.

[0030] FIGs. 2A-B illustrate a circuit architectures of an mmWave plug-and-play module “mmPlug” in accordance with an embodiment of the invention.

[0031] FIGs. 3A-D illustrate antenna configurations to achieve mutual coupling and resonance at the required mmWave frequency in accordance with an embodiment of the invention.

[0032] FIG.4 illustrates frequency components of intermodulation in accordance with an embodiment of the invention.

[0033] FIG.5 illustrates a diplexer in accordance with an embodiment of the invention.

[0034] FIG.6 illustrates a circuit architecture of a standalone transceiver incorporating a “mmPlug” module in accordance with an embodiment of the invention.

[0035] FIG. 7 illustrates a flowchart of a process for converting low frequency RF signals in wireless devices to mmWave signals in accordance with an embodiment of the invention.

[0036] Fig. 8 illustrates mmWave resonating signals at around 28.17 GHz created using a single LNA while leveraging the mutual coupling of antennas in accordance with an embodiment of the invention.

[0037] Fig. 9 illustrates the end-to-end performance of mmPlug in an off-the-shelf Long-Range Radio (LoRa) implementation in accordance with an embodiment of the invention. DETAILED DESCRIPTION

[0038] The Internet of Things (IoT) has become one of the most important technologies in recent years. IoT can enhance efficiency, convenience, and connectivity in daily life, as IoT allows wireless devices to create a global communication network where the devices can exchange data with each other through the internet and act on the exchanged data to refine and optimize the operations of these devices. By interconnecting devices, IoT can provide users with seamless automation and control, allowing users to manage everything from home appliances to industrial machinery remotely, which can lead to improved energy efficiency, cost savings, and a morepersonalized user experience. IoT-driven data collection and analysis can also provide valuable insights that can optimize processes, improve decision-making, and even enhance safety in various sectors, from healthcare to transportation.

[0039] Current wireless devices mostly operate at lower frequency bands of the wireless spectrum, ranging from a few hundred megahertz (MHz) to a few gigahertz (GHz). Even though they are operable at lower frequencies, operation in these frequency bands can impact the performance and usability of these devices in the long run. One main limitation arising from operating at the lower frequency bands is the limited data capacity due to the crowded spectrum. Low-frequency bands are often heavily used by various electronic devices, particularly in urban areas, which may lead to interference and reduced capacity for multiple devices to operate simultaneously. There are many other types of technologies operating at these lower frequencies, such as radio frequency identification (RFID), Bluetooth Low Energy (BLE), and WiFi. This crowded spectrum can result in degraded signal quality and communication congestion, which can hinder the efficiency of all devices. Localization accuracy of the wireless devices may also suffer from the crowed lower frequency bands.

[0040] On the other hand, millimeter wave (mmWave) band ranges from 24 GHz to 300 GHz, and it can be used to provide wireless devices with large bandwidths in a higher frequency spectrum, which allows for better network capacity, low interference, and Space Division Multiple Access (SDMA). As a less-occupied frequency spectrum, mmWave can improve the efficiency and effectiveness of communication between wireless devices. Systems and methods in accordance with embodiments of the invention can enhance the performance of current wireless devices by utilizing a plug-and-play module named “mmPlug” that can be connected to the antenna port of any existing and future wireless devices and allowing it to operate in mmWave band. mmPlug modules can enable existing and future wireless devices to bypass congestion issues when operating at lower frequency bands by communicating using the mmWave spectrum. Wireless devices connected to mmPlug modules can benefit from the advantages of operating at mmWave frequencies, such as the availability of high network capacity, accurate localization, and the ability to perform space division multiplexing by exploiting the sparse mmWave multipath and the directionality of mmWave antennas.

[0041] In numerous embodiments, mmPlug modules include a low noise amplifier (LNA), which is an RF component, as the only active element. With most of the elements on mmPlug being passive, mmPlug modules in accordance with several embodiments can operate while consuming very little power. This can help wireless devices with improved power consumption and management. Traditionally, high mutual coupling is undesired in transmitter and receiver systems. mmPlug modules in accordance with many embodiments, however, leverages the high mutual coupling between a pair of antennas to create a feedback loop to power the LNA, allowing the LNA to resonate at a minimal power cost.

[0042] An implementation of mmPlug modules in a wireless device network in accordance with an embodiment of the invention is illustrated in Fig. 1. Multiple wireless device nodes, each equipped with an mmPlug module, can connect to an mmWave Access Point (AP) to enjoy communication at the mmWave band. In many embodiments, mmPlug modules provide wireless devices with the ability to communicate directionally using directional beams instead of omnidirectional beams. By using directional beams, wireless devices using mmPlug modules can reduce interference from other devices in the network and allow for better seamless communication with the other devices. Moreover, operating at the mmWave band can reduce the strain on a single mmWave AP, meaning that the AP can support different communication protocols (such as LoRa, WiFi, etc.). mmPlug modules can operate as plug-and-play devices and can be easily connected to wireless devices (instead of their antenna). mmPlug modules in accordance with various embodiments can enable both uplink and downlink communication and have on-board mmWave antennas. Additionally, due to the directional property of mmWave communication, mmWave APs can perform space division multiplexing. This can allow multiple nodes to communicate with an AP simultaneously without creating any interference for other devices.

[0043] Although a specific example of an implementation of mmPlug modules in a wireless device network is illustrated in this figure, any of a variety of implementations can be utilized to provide current wireless devices with communication capabilities at the mmWave band similar to those described herein as appropriate to the requirements of specific applications in accordance with embodiments of the invention.Module Design

[0044] Circuit architectures of an mmPlug plug-and-play module in accordance with an embodiment of the invention are illustrated in Figs. 2A-B. mmPlug modules in accordance with various embodiments are designed with simplicity and energy efficiency as their top priorities in order for this module to be practical, and ubiquitously deployable. As illustrated in Fig.2A, mmPlug modules in accordance with many embodiments include at least one RX antenna 210 and at least one TX antenna 220, which are both passive in the circuit. Both RX and TX antennas in accordance with several embodiments can be patch antennas. mmPlug modules in accordance with several embodiments further include a mixer 230. In some embodiments, the mixers may include an LNA. mmPlug modules can further include an mmWave isolator 240. Isolators in accordance with many embodiments include a diplexer that is also a passive element. Fig. 2B illustrates a specific circuit architecture of the mmPlug module including both the LNA and the diplexer. Passive elements can be built using only metal traces on a printed circuit board. In several embodiments, the coupling between the antennas creates a feedback loop that can cause the LNA to resonate at the desired mmWave frequency.

[0045] In numerous embodiments, mmPlug modules leverage mutual coupling between the module's antennas to convert low-frequency radio frequency (RF) signals into high-frequency mmWave band signals and vice versa. Traditionally, mutual coupling between antennas is a concept that may degrade antenna efficiency. However, mmPlug modules can utilize the inherent resonance of the LNA as a zero-cost oscillator to perform the up-conversion into high-frequency mmWave band signals.

[0046] Although a specific example of an mmPlug module is illustrated in this figure, any of a variety of implementations can be utilized similar to those described herein as appropriate to the requirements of specific applications in accordance with embodiments of the invention.

[0047] In the uplink mode, the low frequency RF signal can be fed to the loop through the isolator such as a diplexer. In selected embodiments, diplexers can work as an mmWave isolator to ensure that the mmWave signal does not leak to the wireless device while the lower frequency signals pass through the diplexer. Due to the high loop gain, invarious embodiments, the LNA can get saturated very quickly and operate in a strong non-linear mode. The LNA can then mix the low frequency RF signal with the mmWave resonance signal, which generates a resulting mmWave signal that is modulated by the low frequency RF signal. mmPlug modules in accordance with selected embodiments may utilize an external mixer instead of a saturated LNA to mix the low frequency RF signal with the mmWave resonance signal. One skilled in the art can recognize that other techniques / mechanisms for amplifying and mixing may be used other than LNA. In some embodiments, the TX antenna transmits the modulated mmWave signal.

[0048] In the downlink mode, mmPlug modules may operate in a fashion that is similar to its operation in the uplink mode. In many embodiments, the RX antenna receives a modulated mmWave signal from an mmWave AP. The nonlinearity of the LNA can mix the received signal with the resonating mmWave signal, resulting in a modulated signal at a low-frequency band. Finally, the diplexer at the output of the LNA can pass the low- frequency signal to the wireless device. Leveraging Mutual Coupling of Antennas

[0049] In many embodiments, mmWave modules generate a mmWave carrier signal by leveraging the mutual coupling between the TX and RX antenna to form a feedback loop in the module, where the RX antenna is connected to the input of the LNA and the output of the LNA is connected to the TX antenna. mmWave modules in accordance with several embodiments can use the noises from the wireless devices to form the feedback loop and make the LNA resonate at a desired frequency, where the desired frequency can be adjusted based on the positioning of the antennas. In many embodiments, mmPlug modules can enhance their transmission range by incorporating larger arrays of antennas.

[0050] In selected embodiments, mutual coupling between the antennas generates an attenuated version of the carrier signal at the output of the LNA to the input. As long as the attenuation is smaller than the gain of the LNA, a small noise signal, such as a thermal noise, is capable of creating the resonating carrier signal. Mutual coupling can be controlled to not impact the receiving and radiating performance of the antennas. The amount of coupling can be adjusted through the spacing and relative location of twoantennas to obtain a loop gain that is higher than one. In certain embodiments, the mutual coupling may be reduced by increasing the distance between the antennas, meaning that less signal power will be fed back to the input of the LNA from its output.

[0051] In order to configure mmPlug modules such that the frequency of the resonating signal is at the desired mmWave frequency, systems and methods in accordance with various embodiments account for the scattering parameters (S- parameters) of the antennas. S-parameters may be used to define the relationship between different ports of an RF component (or a system) in terms of amplitude and phase. In general, Snm represents the power transferred from port m to port n of a system. For example, S21represents the power transferred from port 1 to port 2, and S11represents the power which is reflected by port 1 of the system. Well-designed antenna systems typically have low S11 at their operating frequency, meaning that they can radiate most of the power without reflecting it back to the circuit system. The frequency of the resonating signal can be determined by the frequency response of the antennas. The antennas can effectively function like a filter that passes the signal at a specific mmWave band and attenuates the signals at other bands, allowing the frequency of the resonating signal to be the one at which there is the highest mutual coupling between the antennas and also the antennas resonate. Some narrow-band antennas may resonate and radiate at two frequencies, f1and f2. Most narrow-band antennas have a rectangular shape with width W and length L. The resonant frequencies of these rectangular narrow-band antennas can be determined by L and W / 2.

[0052] Antennas in accordance with many embodiments are designed to have a main resonant frequency f1at the required mmWave carrier frequency such that the LNA can resonate at the required frequency. In many embodiments, antennas are designed such that they do not resonate at f2. Antennas may be positioned in a manner that facilitates such resonance. Antenna configurations to achieve mutual coupling and resonance at the required mmWave frequency in accordance with an embodiment of the invention are illustrated in Figs. 3A-D. Fig. 3A demonstrates the mutual coupling (S21) between two antennas which are placed next to each other. The coupling is strong at both S1and S2, which is not desired since it may cause the LNA to resonate at S2. A desirable way wouldbe to position the antennas such that their coupling (S21) is strong at f1 but weak at f2, as illustrated in Fig.3B.

[0053] In several embodiments, the peaks and nodes of the electric field on one antenna’s width edge match the peaks and nodes of the electric field of the width edge of a second antenna in order to have a strong coupling between antennas. In antennas such as microstrip antennas, a non-resonating edge may have a uniform electrical field distribution, while the resonating edge may have a sinusoidal distribution. This means that at f1, the width edge W has an electrical field with uniform distribution, and the length edge L has an electrical field with sinusoidal distribution, as shown in Fig. 3A. Similarly, at f2, edge L has an electrical field with uniform distribution, while edge W has an electrical field with sinusoidal distribution as shown in Fig. 3B. Hence, to reduce the coupling at f2 while keeping the coupling at f1, antennas may be positioned such that their W edges are facing each other with some displacement. In certain embodiments, one of the antennas may be shifted along the X-axis such that the antennas partly face each other as shown in Figs. 3C and 3D. At f2, the field’s peaks and nodes of one antenna do not match the peaks and nodes of the other antenna, which reduces the coupling at that frequency. At the same time, this shift does not impact the coupling of antennas at f1since, at that frequency, the electric field on the facing edge is linear, and even with a shift, the peaks and nodes of the electric fields of the first antenna and second antenna match as shown in Fig.3C.

[0054] In many embodiments, mmPlug modules upconvert low frequency RF signals to mmWave for uplink, and downconvert mmWave signals to the original low frequency RF frequency for downlink. The received mmWave signals in accordance with numerous embodiments are multiplied by the carrier signal (i.e., the resonant signal created by the LNA and antenna loop) to generate the low frequency RF signal. This multiplication may be performed using the intermodulation caused by the non-linear behavior of the LNA. LNAs are typically operated in a fairly linear region. However, the loop gain (including both LNA gain and the antennas’ mutual coupling) in several embodiments is larger than one, and thus, the oscillating signal may continue growing in amplitude until the LNA enters saturation mode. In saturation, the LNA acts as a strong non-linear component, which can intermodulate the low frequency RF signal with the resonating mmWave signal.

[0055] The Taylor expansion of a non-linear function may be utilized to analyze the output of the LNA. In particular, any non-linear function (Ψ) can be written as follows: ଶ ^ ^ ^ ଶ ^ where^are the Taylor coefficients of function Ψ. Consider two signals sc, which is the resonant frequency of the loop, and sAP, which is the received mmWave signal from the AP. When the sum of these signals is present at the input of the non-linear LNA, the resulting output can be presented as follows using Taylor expansion: ଶ ^ ^ ^^ ^ ^ ^ ^ ^^ ଶ ^ ^^ ^ ^ ^^ In the Taylor expansion, higher order coefficients a3 to an are typically very small and hence can be ignored. As a result, the signal at the output of the LNA can be approximated as: ଶ ଶ ^ ^^ ^ ^ ^ ^ ^^ ଶ ^ ଶ ^^ ଶ ^ ^^ Frequency of theinvention are illustrated in Fig. 4. As shown in Fig. 4, the nonlinear behavior of the saturated LNA can act as a strong non-linear component that intermodulates the AP’s mmWave signal (at fAP) with the loop’s resonating signal (at fc) by multiplying the receiving mmWave signal (sAP) with the oscillating mmWave signal (sC) which results in a signal at the difference of their frequencies fAP - fC with some other high-frequency components which are filtered out. Hence, by choosing the AP’s frequency (fAP) to be equal to fC+ fIoTand filtering the other high-frequency components, the resulting signal can be exactly at the wireless device’s operating frequency (fIoT). In a similar manner, mmPlug modules in accordance with several embodiments can also upconvert the low frequency RF signal to transmit a mmWave signal. By injecting a signal at fIoTinto the loop resonating at fc, a signal at the AP’s frequency of fc + fIoT can be generated and transmitted via the antennas.

[0056] mmWave generated by mmPlug modules may need stabilizing as the modules do not use any reference clock or frequency stabilization technique. Hence, the frequency of the signal may suffer from a large Carrier Frequency Offset (CFO), which can vary by as much as 100 KHz even over a short time interval (such as the duration of a packet). This frequency variation requires correction, since otherwise it would cause a high packet error rate.

[0057] In the uplink, mmPlug’s module may transmit both the mmWave signal and the low frequency RF signal (s(t)) at the mmWave band. Since both these two signals suffer from the same CFO variation, the AP can simply eliminate the CFO by mixing these two signals. In particular, we take the square of the received signals, which results in: ଶ ^ ଶ ଶ ଶ ^^ ^ ଶ ଶ ଶ ^ ^ ^ where is the varying mmWave frequency,^is the wireless device’s operating frequency, and is the wireless device’s modulated signal. The output of the squared signal in many embodiments has a low-frequency component at^which is the down converted low frequency RF signal without any CFO. Hence, the signal may be extracted using a low pass filter and resolve the CFO variation in the uplink communication.

[0058] For the downlink, the AP may also be utilized to mitigate the CFO variation. As illustrated earlier, the mmPlug module typically transmits its carrier signal. APs in accordance with several embodiments capture this signal and use it to transmit the downlink signal with the same CFO variation as the mmPlug module. Hence, the received signal at the mmPlug module may have the same CFO variation as the module’s mmWave signal, and thus the intermodulated signal is CFO-free at the wireless device’s original band. Diplexers

[0059] One design concern for the mmPlug module is that it needs to enable a wireless device to feed its low-frequency RF signals into the loop during up-conversion and extract the low-frequency RF signals from the loop during down-conversion without impacting the loop itself. The wireless device node’s RF impedance may load mmPlug module’s loop impedance and reduce the loop gain, preventing the LNA and antennas from resonating. In many embodiments, mmPlug modules include mmWave isolators such as diplexers to isolate the impedance of the wireless device node. Diplexers in accordance with several embodiments are a compact and passive component. An example diplexer in accordancewith many embodiments of the invention is illustrated in Fig. 5. The diplexer can have three ports, as demonstrated in Fig. 5. Ports one and two may be connected together using a transmission line, allowing any signal of any frequency to pass through them. In many embodiments, the third port includes a bow-tie structure, which is a combination of two open-ended transmission lines. The length of the bow tie and its location along the main transmission line can be designed in a way that isolates the third port of the diplexer from the loop at mmWave frequency. Hence, mmWave signals can pass from port one to port two without entering into port three. At lower frequencies, however, the third port may not be isolated, and hence, the low-frequency signal can pass from the main transmission line connecting ports one and two to the third port and vice versa.

[0060] In many embodiments, diplexers are integrated into mmPlug modules such that port one is connected to the LNA output, port two is connected to the TX antenna, and port three is connected to the wireless device. Diplexers can isolate the wireless device from the mmWave loop and hence can help prevent the wireless device from interfering with the loop’s resonant frequency while enabling both uplink and downlink communication, as described above.

[0061] Although a specific example of a diplexer is illustrated in this figure, any of a variety of diplexers can be utilized similar to those described herein as appropriate to the requirements of specific applications to isolate wireless devices from mmWave signals in accordance with embodiments of the invention.

[0062] An example of a standalone transceiver incorporating an mmPlug in accordance with an embodiment of the invention is illustrated in Fig. 6. In these embodiments, the mmPlug can be used as both the transmitter and receiver. Standalone transceivers in accordance with many embodiments include at least one RX antenna 610, at least one TX antenna 620, an LNA 630, an RF choke 640, an intermediate frequency (IF) amplifier 650, a comparator 660, and a low-power processor 670. As a receiver, mmPlug in this configuration can down-convert the mmWave band signal to the IF where the signal is passed to the IF receiver section. In many embodiments, this architecture allows for a General-Purpose Input / output (GPIO) port of a low-power processor to be used instead of using a power-hungry Analog to Digital Converter (ADC). As the required signal level of a GPIO port is in the millivolt (mV) range while the received signal level isin the range of microvolt (µV), in some embodiments, an IF amplifier is used to boost the signal power and a comparator to provide the signal in a level proper for the GPIO port. The data of the received mmWave band signal can be given to the GPIO port of a low- power processor, and if the signal level is higher than a pre-set threshold, the data may be designated as symbol “1.” If the signal level is lower than the threshold, it may be designated as symbol “0”. The comparator can act like a 1-bit ADC, which helps reduce the noise effect and keeps power consumption extremely low compared to that of a conventional receiver. In many embodiments, this architecture does not detect the signal phase, so it may only be used for on-off keying (OOK) modulation.

[0063] In the uplink mode of this architecture, the GPIO port of the same low-power processor may be used. The dedicated GPIO port is connected to the biasing port of the LNA, and the output of the GPIO may be either high or low. The output of the GPIO port can control the LNA, and when the data is “1”, the LNA is switched on so mmPlug can transmit a sine wave at the mmWave band. When the data is “0”, the LNA switches off, so there is no sine wave transmission at the mmWave band. This architecture can generate an OOK modulated signal at mmWave band without using a Digital to Analog Converter (DAC) so it can save a significant amount of power consumed.

[0064] Although a specific example of a standalone transceiver incorporating an mmPlug plug-and-play module is illustrated in this figure, any of a variety of standalone transceiver circuits incorporating mmPlug modules can be utilized to convert low- frequency RF signals into high-frequency mmWave band signals and vice versa similar to those described herein as appropriate to the requirements of specific applications in accordance with embodiments of the invention. Up-conversion Process

[0065] A process for up-converting low frequency RF signals in wireless devices to mmWave signals in accordance with an embodiment of the invention is illustrated in Fig. 7. Process 700 generates (710) a mmWave resonance signal. In numerous embodiments, the mmWave resonance signal is generated by reshaping the signal created by the mutual coupling of the two antennas on the mmPlug module. Process 700 receives (720) a low frequency RF signal from a wireless device. In certain embodiments,this low frequency RF signal is received through the diplexer. Process 700 (730) intermodulates the generated mmWave resonance signal with the received low frequency RF signal from a wireless device. In several embodiments, the received low frequency RF signal is converted from its lower RF band to the higher mmWave band through this modulation. Process 700 transmits (740) the modulated mmWave signal. At step 740, the wireless devices can begin communicating with other wireless devices at the mmWave frequency bands.

[0066] While specific processes for up-converting low-frequency RF band signals into high-frequency mmWave band signals in wireless devices are described above, any of a variety of processes can be utilized to up-convert low frequency RF signals as appropriate to the requirements of specific applications. In certain embodiments, steps may be executed or performed in any order or sequence not limited to the order and sequence shown and described. In a number of embodiments, some of the above steps may be executed or performed substantially simultaneously where appropriate or in parallel to reduce latency and processing times. In some embodiments, one or more of the above steps may be omitted. Results

[0067] Fig. 8 illustrates mmWave resonating signals at around 28.17 GHz created using a single LNA while leveraging the mutual coupling of antennas in accordance with an embodiment of the invention. Fig. 8 demonstrates that mmPlug has successfully created an mmWave signal by using a single LNA and leveraging the antennas’ mutual coupling. While there are small deviations from 28 GHz, which stem from the fabrication accuracy and tolerance, these slight deviations in the resonant frequency can be compensated by adjusting the AP’s carrier frequency in practice such that the frequency difference is exactly the frequency of the low frequency RF band. Moreover, by adjusting the biasing voltage of the LNA in an mmPlug module, the resonate frequency can be slightly (up to 80 MHz) adjusted during the installation stage. The frequency of the generated mmWave signal may not be very stable and can vary over time. The variations can be compensated by capturing the down-converted signal received at the mmWave AP.

[0068] Fig. 9 illustrates the end-to-end performance of mmPlug in an off-the-shelf Long-Range Radio (LoRa) implementation in accordance with an embodiment of the invention. The mmPlug module is connected to the antenna port of the LoRa module, and the signal-to-noise ratio (SNR) and received signal strength indicator (RSSI) were measured at different distances. Fig. 9 demonstrates that the SNR at the AP is higher than -8 dB even when the node is 30 m away from the AP. This SNR is enough for LoRa to enable a packet error rate (PER) of less than 10^-5 using a LoRa spreading factor of 8 or higher. In addition, the measured RSSI at the node is higher than -80 dBm even when the node is 30 m away from the AP. This RSSI is more than enough to establish LoRa communication with less than 10^−5 PER. Fig. 9 implies that even for longer distances, mmPlug can enable off-the-shelf LoRa modules to successfully communicate to an mmWave AP without making any changes to the LoRa module’s protocol, chipset, or firmware.

[0069] Although specific methods of converting low-frequency RF band signals into high-frequency mmWave band signals and vice versa are discussed above, many different conversion methods can be implemented in accordance with many different embodiments of the invention. It is therefore to be understood that the present invention may be practiced in ways other than specifically described, without departing from the scope and spirit of the present invention. Thus, embodiments of the present invention should be considered in all respects as illustrative and not restrictive. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their equivalents.

Claims

WHAT IS CLAIMED IS:

1. A system that can be connected to antenna ports of wireless devices to provide wireless devices with millimeter wave (mmWave) communication over the air capabilities, the system comprising: at least one RX antenna and at least one TX antenna, where the RX and TX antennas are positioned at a distance from each other and configured to mutually couple with each other to generate a feedback loop, wherein the distance is determined by a desired resonant frequency of a mmWave resonance signal to be generated by the feedback loop, wherein the mmWave resonance signal is mixed with a received low frequency radio frequency (RF) signal to generate a mmWave transmit signal.

2. The system of claim 1, further comprising a diplexer configured to receive the low frequency RF signal from an IoT (Internet of Things) wireless device.

3. The system of claim 2, wherein the diplexer includes two ports connected together using a transmission line.

4. The system of claim 3, wherein the diplexer further includes a third port having a bow-tie structure that isolates the third port from the feedback loop.

5. The system of claim 1, further comprising a mixer configured to generate the mmWave transmit signal from the TX antenna by intermodulating the mmWave resonance signal generated by the feedback loop with the received low frequency RF signal.

6. The system of claim 5, wherein the mixer is a low noise amplifier (LNA) that is further configured to modulate a mmWave signal received at the RX antenna and convert the received mmWave signal to a low frequency RF signal.

7. The system of claim 6, wherein the LNA is driven to resonance based on a noisesignal in the system when the attenuation of the noise signal is smaller than the gain of the LNA.

8. The system of claim 6, wherein the LNA resonates at a desired frequency determined based upon the positioning of the RX and TX antennas.

9. The system of claim 1, further comprising: an RF choke configured to downconvert received mmWave signals to an intermediate frequency (IF) band; an IF amplifier configured to boost the voltage levels of received IF signals; a comparator configured to reduce noise of the received IF signals; and a low power processor to process the received IF signals.

10. The system of claim 1, wherein the received low frequency RF signals include radio frequency identification (RFID), Bluetooth Low Energy (BLE), and WiFi signals.

11. The system of claim 1, wherein the generated mmWave transmit signal is transmitted directionally using directional beams.

12. The system of claim 1, wherein the loop gain is higher than one.

13. The system of claim 1, wherein each of the RX and TX antennas are rectangular in shape comprising two length edges and two width edges.

14. The system of claim 13, wherein each of the RX and TX antennas has two resonant frequencies, wherein the two resonant frequencies include a main resonant frequency and a secondary resonant frequency.

15. The system of claim 14, wherein at the main resonant frequency, the length edge of each of the RX and TX antennas has an electrical field with a sinusoidal distribution and the width edge of each of the RX and TX antennas has an electrical field with uniformdistribution.

16. The system of claim 15, wherein each of the RX and TX antennas are positioned such that the width edges of both antennas face each other, and are displaced along the width edges such that, at the main resonant frequency, the peaks and nodes of the electric field on each of the RX antenna’s width edge match the peaks and nodes of the electric field of the width edge of each of the TX antenna.

17. The system of claim 16, wherein each of the RX and TX antennas are positioned such that the coupling is weak at the secondary resonant frequency.

18. The system of claim 1, wherein the mutual coupling is reduced by increasing the distance between the RX and TX antennas.

19. The system of claim 1, wherein the number of RX and TX antennas is increased to increase transmission range.

20. The system of claim 1, wherein the at least one RX antenna receives a modulated mmWave signal from an mmWave access point (AP).

21. The system of claim 20, wherein the received mmWave signal is downconverted to a low frequency RF signal by mixing the received mmWave signal with a resonating mmWave signal in the feedback loop.

22. A method for upconverting low frequency RF signals to mmWave signals in wireless devices, the method comprising: generating a mmWave resonance signal; receiving a low frequency RF signal from an IoT wireless device; intermodulating the generated mmWave resonance signal with the received low frequency RF signal to generate a mmWave transmit signal; and transmitting the mmWave transmit signal.

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