Patent Publication Number: US-2020279469-A1

Title: Radio frequency detector

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application Ser. No. 62/812,183, which was filed on Feb. 28, 2019, and U.S. Provisional Application Ser. No. 62/859,749, which was filed on Jun. 11, 2019, the entireties of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to implementations of a radio frequency (RF) detector. In particular, the present invention is directed to implementation(s) of a wearable radio frequency detector. 
     BACKGROUND 
     Increasing use of wireless technology in consumer and household electronics has resulted in significantly elevated levels of environmental microwave radiation in recent years. These elevated levels of microwave radiation are beginning to produce physiological effects in the general public. These effects are manifesting as physiological symptoms (e.g., conscious sensations, disrupted sleep, etc.) as well as cellular damage (e.g., DNA strand breaks, elevated cell apoptosis, etc.). 
     Accurately monitoring broad microwave bands (e.g., 1 GHz to about 12 GHz) has typically required specialized antennas connected to large and expensive lab test equipment. Low cost, small, battery powered microwave detectors have only recently become available. These detectors have limited detection bandwidth (a few GHz), poor response linearity across the measurement range, and are too large to conveniently carry. 
     To continuously monitor elevated microwave radiation levels in modern urban environments; a wide bandwidth, high linearity, physically small detector with all-day battery life provides the ideal solution. A combination of these features in a single device has not, to date, been attainable. 
     Accordingly, it can be seen that needs exist for the radio frequency detector disclosed herein. It is to the provision of a radio frequency detector that is configured to address these needs, and others, that the present invention is primarily directed. 
     SUMMARY OF THE INVENTION 
     Implementations of a wearable radio frequency (RF) detector are provided. The wearable RF detector is configured to monitor environmental electromagnetic radiation and comprises a high sensitivity, high linearity RF detection circuit that is paired with a compact, broadband, non-resonant antenna. This combination enables a physically small, yet accurate, detector to be built. An electronic circuit that includes efficient physical electronics, a power management logic, and the use of leading-edge battery technology enables the radio frequency detector to operate for a full day and to remain small enough to be “wearable” (e.g., a wrist watch, a pendant, etc.). By combining the aforementioned elements into a convenient and unobtrusive wearable device, continuous monitoring of electromagnetic radiation in a wearer&#39;s surrounding environment becomes practical. 
     An exemplary implementation of the wearable radio frequency detector comprises: an electronic circuit configured to monitor environmental electromagnetic radiation within a frequency band of interest; the electronic circuit comprises a radio frequency detection circuit and a non-resonant antenna that lacks resonant modes in the frequency band of interest; wherein the radio frequency detection circuit, in conjunction with the non-resonant antenna, facilitates the monitoring of environmental electromagnetic radiation within the frequency band of interest. 
     In some implementations, the electronic circuit is contained within a housing that includes a wristband. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a block diagram of a wearable radio frequency detector constructed in accordance with the principles of the present disclosure. 
         FIGS. 2-6  illustrate the wearable radio frequency detector shown in  FIG. 1 , or portions thereof. 
         FIG. 7  illustrates a partial enlarged view of  FIG. 1 , wherein an example power management logic for the wearable radio frequency detector is shown. 
     
    
    
     Like reference numerals refer to corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a block diagram of a wearable radio frequency (RF) detector  100  constructed in accordance with the principles of the present disclosure. The RF detector  100  is configured to monitor environmental electromagnetic radiation (e.g., microwaves). 
     Integration of the circuit components into a physically compact space with minimal interference is a significant challenge for an RF measurement device. Typically, antenna size and spacing requires an RF measurement device to be physically large (handheld or larger). One or more implementations of the wearable RF detector  100  solve these challenges by carefully packaging circuit components around a non-resonant antenna  110 . Further, selection of low electro-magnetic emission (EMI) circuit components combined with mechanical packaging that places the antenna  110  in an “open sky” position on the face of the detector  100  enables good performance in a much smaller space than existing devices (note antenna  110  location in  FIGS. 2 and 4 ). An example of this physical integration is shown in  FIGS. 2-6 . Integrating the circuit components in a way that minimizes physical size and maximizes RF measurement performance is described in detail below. 
     In some implementations, the configuration of the non-resonant antenna  110  is key to designing a wearable RF detector  100  that is both physically small and broad in frequency response, typically exceeding one order of magnitude in the microwave band (e.g., below 1 GHz to above 10 GHz). For flat response across a frequency band, the non-resonant antenna  110  is designed to lack resonant modes in the frequency band of interest. It is only resonant at significantly higher frequencies that are out of the measurement band. Resonant modes are typically employed to yield high-sensitivity, narrow-frequency, in-band response (e.g., as required by WiFi and Bluetooth devices), as this improves narrow-band performance. Using an antenna  110  that lacks significant resonant gain for in-band measurement is a counter-intuitive approach that flattens the in-band frequency response without requiring a complex antenna, frequency selective filtering circuitry, or a combination thereof. 
     To achieve high sensitivity, despite the low gain of the non-resonant antenna  110  design, a high-sensitivity/low-noise RF detection circuit  160  is employed. This RF detection circuit  160  includes a high-gain, low-noise, broad-band amplifier  162  connected to a high-sensitivity, high-speed, low-noise analog-to-digital converter  128 . This RF detection circuit  160  provides a simple, compact, and cost-effective means of measuring electromagnetic radiation with a band of interest (e.g., the microwave band, or a portion thereof). 
     Further, the non-resonant design of the antenna  110  has the added benefit of low gain and provides for consistent measurement regardless of the orientation of the RF detector  100 . This is especially important for a wearable RF detector  100 , as its orientation is tied to a wearer&#39;s body position. 
     In some implementations, the wearable RF detector  100  comprises a housing  102  with a wristband  106  (see, e.g.,  FIGS. 2-6 ), the housing  102  contains an electronic circuit  108  configured to monitor environmental electromagnetic radiation. 
     As shown in  FIG. 1 , in some implementations, the electronic circuit  108  of the wearable RF detector  100  may comprise a microprocessor  120  that includes a nonvolatile memory, I/O (input/output) devices (e.g., LED indicators  130 , a haptic feedback device  132 , and a ON/OFF switch  134 ), a power system  150 , and RF measurement components (e.g., an RF detection circuit  160 ) that use at least one non-resonant antenna  110 , or a suitable combination thereof. In some implementations, the wearable RF detector  100  may further comprise I/O (input/output) interfaces (e.g., a SD card slot  138 , a USB port  140 , a near field communication (NFC) device  142 ) and/or a GPS subsystem  170 . In some implementations, one or more components of the electronic circuit  108  may be mounted on a printed circuit board (PCB) and conductively connected together thereby (see, e.g.,  FIG. 2 ). 
     The microprocessor  120  of the electronic circuit  108  is configured to enable the wearable RF detector  100  to perform the functions that are implied and/or specified herein. In some implementations, the nonvolatile memory may be an integral part of the microprocessor  120 , or a discrete component. 
     As shown in  FIGS. 1 and 7 , in some implementations, the microprocessor  120  includes an adaptive power management algorithm  122  that may be stored in the nonvolatile memory. This power management algorithm  122  uses measured RF values, local device  100  motion (an onboard accelerometer being used to detect motion), and, in some implementations, global device  100  movement (a GPS subsystem  170  being used to track movement) to set RF measurement frequency and period, as well as the corresponding sleep/low-power time between RF measurements. This adaptive power management algorithm  122  is useful because continuous measurement of high speed/high bandwidth electromagnetic radiation is energy intensive. The necessary analog amplifier circuits and high-speed digital processing necessitate careful power management to achieve good battery life, especially with compact/low capacity batteries. 
     As shown in  FIG. 1 , one or more I/O controllers  124  may be provided to interface an I/O device (e.g., LED indicators  130 , a haptic feedback device  132 , and a ON/OFF switch  134 ) with one or more components (e.g., the microprocessor  120 ) of the electronic circuit  108 . 
     In some implementation, RF calibration constants  126  may be stored in the nonvolatile memory of the microprocessor  120 . The RF calibration constants  126  provide a calibrated baseline used by the microprocessor  120  to correct for environmental factors (e.g., temperature) that can affect the accuracy of RF measurements recorded by the RF detector  100 . In this way, consumer grade (i.e., cheaper) electrical components can be used to assemble the electronic circuit  108 . 
     In some implementations, the electronic circuit  108  may include an analog-to-digital convertor  128  that facilitates high precision analog measurement of electromagnetic radiation detected by the non-resonant antenna  110 . In some implementations, the analog-to-digital convertor  128  may be an integral part of the microprocessor  120 , or a discrete component. 
     As shown in  FIGS. 1, 2, and 6 , in some implementations, the electronic circuit  108  of the RF detector  100  may include four light emitting diodes (LEDs)  130  that are visible through openings  103  in the face of the housing  102 . The LEDs  130  provide visual feedback to the wearer regarding the power of electromagnetic radiation being measured by the RF detector  100 . In some implementations, the number of LEDs  130  illuminated acts as a power level indicator for in-band frequencies being detected, each illuminated LED  130  corresponding to a relative order of magnitude (˜10 dBs). In some implementations, the electronic circuit  108  may include more than four or less that four LEDs  130 . 
     As shown in  FIG. 1 , in some implementations, the electronic circuit  108  includes a haptic feedback device  132  since wearable detectors are the least obtrusive when they provide non-visual indicators, such as haptic feedback (e.g., vibration). The user is provided with haptic feedback when electromagnetic radiation having a power level that meets, or exceeds, a set threshold value is measured by the RF detector  100 . The threshold value that triggers haptic feedback is set during manufacture of the RF detector  100 , but, in some implementations, the threshold value can be set by the user. In some implementations, the wearable RF detector  100  provides haptic feedback via a linear resonant actuator (LRA)  132 . LRAs provide high amplitude vibration with minimal power consumption. Also, unlike brushed motor eccentric rotating mass (ERM) actuators, LRAs are brushless and emit no electro-magnetic interference (EMI) that could interfere with measurement of electromagnetic radiation by the RF detector  100 . Additionally, the haptic feedback device  132  (i.e., the LRA) is packaged below the circuit board ground plane, under all active measurement elements (see, e.g.,  FIGS. 3 and 5 ). 
     As shown in  FIGS. 1-2, and 4 , the electronic circuit  108  includes an ON/OFF switch  134  that can be used to turn the RF detector ON and OFF. In some implementations, the face of the housing  102  includes a flexible contact member  104  that a wearer can press to toggle the ON/OFF switch  134  (see, e.g.,  FIG. 6 ). 
     As shown in  FIG. 1 , in some implementations, the electronic circuit  108  may include a Secure Digital (SD) card slot  138 . In this way, removable non-volatile memory cards  138   a  can be used to expand the overall memory of the electronic circuit  108  and/or to update the system (i.e., makes changes to the microprocessor  120  and/or the nonvolatile memory) of the RF detector  100 . 
     As shown in  FIG. 1 , in some implementations, the electronic circuit  108  may include a Universal Serial Bus (USB) port  140 . The USB port  140  may be used to charge the system battery  154  (discussed in greater detail below) and/or to connect an external device (e.g., a personal computer) to the electronic circuit  108  of the RF detector  100 . The external device may be used to collect data stored in the nonvolatile memory of the RF detector  100  and/or to update the system (i.e., makes changes to the microprocessor  120  and/or the nonvolatile memory). 
     As shown in  FIG. 1 , in some implementations, the electronic circuit  108  may include a near-field communication (NFC) device  142 . The NFC device  142  may be used to collect data stored in the nonvolatile memory of the RF detector  100  and/or to wirelessly update the system (i.e., makes changes to the microprocessor  120  and/or the nonvolatile memory). In some implementations, communication protocol(s) for the NFC device  142  are stored in the nonvolatile memory of the electronic circuit  108 . 
     As shown in  FIGS. 1 and 7 , in some implementations, the power system  150  of the RF detector  100  includes a USB charger circuit  152 . The USB charger circuit  152  works in conjunction with the USB port  140  to charge the system battery  154 . In some implementations, the system battery  154  may be a button cell, or another electrochemical cell having a suitable form factor. 
     As shown in  FIGS. 1 and 7 , in some implementations, the power system  150  of the electronic circuit  108  may include a switch-mode power supply (SMPS)  156  that acts as a high efficiency regulator. In some implementations, the SMPS  156  has a very lower power draw/low parasitic draw (e.g., under 10 micro amps) and is configured to keep the electronic circuit  108  of the RF detector  100  active using a minimal amount of system power. 
     As shown in  FIGS. 1 and 7 , in some implementations, the electronic circuit  108  of the RF detector  100  may include a linear regulator  158  that is positioned between the power source (i.e., the SMPS  156 ) and the RF measurement components (e.g., the RF detection circuit  160  and the broadband frequency counter  164 ). The linear regulator  158  acts as a low-noise power source for the RF measurement components of the electronic circuit  108 , thereby allowing for accurate RF measurement. The linear regulator  158  is used because a power supply (e.g., the SMPS  156 ) generates noise that can negatively impact the accuracy of RF measurement. In some implementations, the linear regulator  158  may be configured to supply power to the GPS subsystem  170 . 
     As shown in  FIGS. 1 and 7 , in some implementations, the electronic circuit  108  of the RF detector  100  may include a second linear regulator  159  that is positioned between the power source (i.e., the SMPS  156 ) and the microprocessor  120 . The linear regulator  159  acts as a low-noise power source for the microprocessor  120 , thereby allowing for accurate RF measurement. 
     As shown in  FIG. 1  in some implementations, the RF measurement components of the electronic circuit  108  comprise an RF detection circuit  160  that includes a broadband amplifier  162 , a broadband frequency counter  164 , and at least one non-resonant antenna  110 . 
     In some implementations, when used in conjunction with the non-resonant antenna  110 , the RF detection circuit  160  facilitates frequency measurement of the dominant carrier frequency that is in-band (i.e., the highest power carrier frequency). 
     In some implementations, the broadband amplifier  162  (which includes a log amplifier) is configured to measure a logarithmic input and to provide a linear output used to calculate power and frequency of electromagnetic radiation picked up by the non-resonant antenna  110 . In some implementations, the broadband amplifier  162  facilitates measurement of a broad-dynamic range of radio frequencies by the RF detection circuit  160 . In some implementations, the broadband amplifier  162  is a discrete component of the electronic circuit  108  (not shown). 
     In some implementations, the broadband frequency counter  164  (e.g., a prescaler circuit) is configured to facilitate measurement of, and provide additional information about, the carrier frequency of a signal. The broadband frequency counter  164  is an analog divider configured to provide a highly divided multiple of the carrier frequency to the microprocessor  120 , thereby allowing for a simple, low speed, measurement by the microprocessor  120 . In some implementations, the broadband frequency counter  164  uses a separate non-resonant antenna  112  (see, e.g.,  FIG. 1 ). In some implementations, the broadband frequency counter  164  shares the non-resonant antenna  110  with the RF detection circuit  160  (not shown). In some implementations, the electronic circuit  108  of an RF detector  100  may not include a broadband frequency counter  164  (not shown). 
     In some implementations, the maximum dimensions of a non-resonant antenna  110 ,  112  are approximately ¼ the wavelength of the highest measurement frequency and/or 1/50 the wavelength of the lowest measurement frequency. For example, the non-resonant antenna  110 ,  112  could be a rectangular patch antenna having dimensions that are 1/25 of a wavelength at 1 GHz. Implementations of the non-resonant antenna  110 ,  112  design are scaled (i.e., dimensioned) depending on the frequency band(s) being measured (e.g., the microwave band). The small size of the antenna  110 ,  112 , resulting from its intentionally non-resonant design, allows the wearable RF detector  100  to be significantly smaller than traditional designs employing industry standard broadband antennas (e.g. logarithmic-periodic antennas, or multiple frequency-selective antennas). Additionally, the antenna&#39;s  110 ,  112  lack of resonance in the measurement band allows it to be packaged in close proximity to nearby electronic elements without the significant performance degradation that typically occurs due to de-tuning effects. This proximity can be as little as 1/100 the wavelength for the frequency band being measured (e.g., approximately 3 mm at 1 GHz). 
     As shown in  FIG. 1 , in some implementations, the electronic circuit  108  may include a GPS subsystem  170 . In some implementations, the use of a GPS subsystem  170  allows localization and time-stamping of electromagnetic power and frequency measurements, thereby providing the user with a rich dataset that can be used to map areas both geographically and temporally. This enables the wearable RF detector  100  to track changes in microwave radiation in a given environment across time. This data could be used for medical research, real-estate valuation, etc. 
     Although not shown in the drawings, it will be understood that suitable wiring connects the electrical components of the wearable RF detector  100  disclosed herein. 
     Reference throughout this specification to “an embodiment” or “implementation” or words of similar import means that a particular described feature, structure, or characteristic is included in at least one embodiment of the present invention. Thus, the phrase “in some implementations” or a phrase of similar import in various places throughout this specification does not necessarily refer to the same embodiment. 
     Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. 
     The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the above description, numerous specific details are provided for a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that embodiments of the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations may not be shown or described in detail. 
     While operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results.