Abstract:
A system for enhancing power efficiency of a wireless device is disclosed. In one embodiment, the wireless device includes a transmitter having a transmitter antenna and configured to transmit a signal, as well as an energy receiver having a plurality of energy receiver antenna elements positioned across one or more surfaces of the wireless device. The energy receiver antenna elements are each configured to receive a portion of the signal, convert the portion of the signal into power, and provide the power to one or more components of the wireless device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. provisional application having Ser. No. 61/798,551, filed on Mar. 15, 2013, which is hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This disclosure relates generally to electrical circuits, and more particularly to a radio frequency (RF) transmission apparatus with reduced power consumption. 
         [0004]    2. Description of Related Prior Art 
         [0005]      FIG. 1 , panel A, depicts a top view of a conventional wireless communication device  100 . Common wireless communication devices include cellular phones, wireless networking devices, wireless handsets, personal digital assistants (PDAs), laptop and desktop computers, routers, and key fobs. As shown, the wireless communication device  100  includes a battery  102 , a digital signal processor (DSP)  104 , a transceiver  106 , a power amplifier  108 , an antenna  110 , and other electronic circuitry  112 . The battery  102  provides direct current (DC) power to other device components. The digital signal processor (DSP)  104  manipulates communication signals between analog and digital signal processing domains, while the transceiver  106  up and down converts the communication signals between low frequencies and RF frequencies. The power amplifier  112  amplifies a power of the signal output from the transceiver to drive a transmission signal into the antenna  110 . In turn, the antenna  110  transmits the transmission signal into free space. A receiver of another wireless communication device (not shown) may receive the radiated signal through a receiver antenna and process the received signal, thus allowing wireless communication of information between the wireless communication device  100  and the other wireless communication device. 
         [0006]    Panel B depicts a side view of the conventional wireless communication device  100 . As shown, the antenna  110  and electronic circuitry components  140  (e.g., the DSP  104 , the transceiver  106 , etc.) are mounted on a substrate  130  such as a printed circuit board (PCB). In addition, the wireless communication device  100  includes an electrical shield  150  which can serve two purposes: (1) preventing internally generated electrical signals from radiating out to affect the function of other components; and (2) preventing externally generated electrical signals from radiating in to affect the function of the components  140 . 
         [0007]      FIG. 2  depicts an enclosure of a convention wireless communication device. Panel A shows a wireless phone device  200  and panel B shows a wireless tablet device  250 . As illustrated in panel A, the wireless phone device  200  includes antenna(s)  210  for transmitting and/or receiving radio frequency signals. The wireless phone device  200  further includes a key pad  220  for tactile input and a display screen  230  for display and/or tactile input. Although a physical key pad  220  is shown, the wireless phone device  200  may alternatively include a virtual key pad (not shown), which is a software component that permits key stokes to be made via, e.g., a touch screen. In addition, the wireless phone device  200  includes casing which holds all the electronic components and component mounting substrates of the wireless phone device  200 . The casing may also electrically isolate the internal components of the wireless phone device  200  from the exterior. A back cover (not shown) of the wireless phone device  200  may also include casing made from various materials. Similarly, the wireless tablet device  250  includes antenna(s)  260 , a key pad  270  (or a virtual keypad), and a display screen  280  which may generally perform the same functions as the antenna(s)  210 , the key pad  220 , and the display screen  230  of the wireless phone device  200 . In addition, the wireless tablet device  250  may also include a casing that encloses electronic components and component mounting substrates and electrically insulates these components, as well as a back cover. 
       SUMMARY OF INVENTION 
       [0008]    Embodiments of the invention described herein enable radio frequency (RF) transmission devices to receive transmission power that is radiated onto the surfaces of the devices. In one embodiment, a wireless device is provided. The wireless device includes a transmitter having a transmitter antenna and configured to transmit a signal. The wireless device also includes an energy receiver having a plurality of energy receiver antenna elements positioned across one or more surfaces of the wireless device. The energy receiver antenna elements are each configured to receive a portion of the signal, convert the portion of the signal into (DC) power, and provide the (DC) power to one or more components of the wireless device. 
         [0009]    In another embodiment, a wireless device is provided that includes a transmitter having a transmitter antenna and an energy receiver antenna. The transmitter antenna is configured to transmit a signal. The wireless device also includes an energy receiver having a receiver antenna and configured to receive a portion of the signal, convert the portion of the signal into power, and provide the power to one or more components of the wireless device. The receiver antenna is configured as a weakened antenna which does not efficiently receive the portion of the signal. 
         [0010]    In yet another embodiment, a wireless device is provided that includes a transmitter having a transmitter antenna and an energy receiver having first and second receiver antennas. The transmitter antenna is configured to transmit a signal. The first and second receiver antennas are configured to receive a portion of the signal, convert the portion of the signal into power, and provide the power to one or more components of the wireless device. Frequency centers of the transmitter antenna and the first receiver antenna are matched, while frequency centers of the transmitter antenna and the second receiver antenna are not matched. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
           [0012]      FIG. 1  illustrates top and side views of a conventional wireless device. 
           [0013]      FIG. 2  depicts an enclosure of a convention wireless communication device. 
           [0014]      FIG. 3  is a block diagram of a wireless communication device configured to receive power from its own transmissions, according to an embodiment. 
           [0015]      FIG. 4  illustrates matched energy receiver antennas substantially covering the surface of a wireless communication device, according to an embodiment. 
           [0016]      FIG. 5  illustrates mismatched energy receiver antennas substantially covering the surface of a wireless communication device, according to an embodiment. 
           [0017]      FIG. 6  illustrates combining matched and mismatched energy receiver antennas to substantially cover the surface of a wireless communication device, according to an embodiment. 
           [0018]      FIG. 7  illustrates use of energy receiver antennas as electrical shields in a wireless communication device, according to an embodiment. 
       
    
    
       [0019]    For clarity, identical reference numbers have been used, where applicable, to designate identical elements that are common between figures. It is contemplated that features of one embodiment may be incorporated in other embodiments without further recitation. 
       DETAILED DESCRIPTION 
       [0020]      FIG. 3  depicts a wireless communication device  302  configured to receive power from its own transmissions, according to an embodiment. As shown, the wireless communication device  302  includes direct current (DC) power source(s)  306  that provide power to a modulator  310 , power amplifier(s)  312 , and components performing other functions of the wireless communication device transmitter (TX)  308  which may include a transmit processor having a time variant transmit carrier frequency or frequencies (Fc or Fc(s)). The wireless communication device  302  further includes (optional) regulators  314 ,  316 ,  318  that respectively provide correct voltage and/or current regulation to the components  308 , the modulator  310 , and the power amplifier(s)  312 . The modulator  310  may include a voltage controlled oscillator and phase lock loop to select a given transmit frequency from a range of possible transmit frequencies. The power amplifier  312  amplifies a power of a modulated signal output from the modulator  310 . The output of the power amplifier  312  (also referred to herein as “TX signal power”) is transmitted through a transmit antenna  328  into free space. Remote receiver antenna(s)  332  may then receive the radiated signal and process the received signal, thus allowing wireless communication of information between the wireless device  302  and the remote wireless device  340 . 
         [0021]    RF transmit (TX) signal power radiated by transmit antenna(s)  328  may be high in order to compensate for the distance from remote receiver antenna(s)  332  and to compensate for any signal power lost due to DC power signal(s) circuitry objects blocking the signal path. As is well known, RF signal power degrades by distance squared. For example, if transmit antenna(s)  328  transmit 1-2 Watts of RF signal power, the remote receiver antenna(s)  332  might only receive a few uW of RF signal power. This low level of RF signal power is typically enough for functional wireless communication. 
         [0022]    As shown, the wireless communication device  302  includes an energy receiver  320  that includes an energy receiver (ERX) antenna  330  and energy receiver circuitry element(s)  322  configured to receive a time variant communication signal and alternating current (AC) to DC converter(s)  324  configured to convert the received communication signal into DC power. That is, RF transmission signal power generated by the transmit antenna(s)  328  is received and converted into DC power which can provide electrical power to the wireless device  302  for operation and/or battery charging. The energy receiver  320  further includes a DC power management circuit  326  that can provide proper voltage levels of DC power to circuits (or components) within the wireless communication device  302 . 
         [0023]    As shown, the energy receiver antenna(s)  330  are placed within a short, fixed distance D short (s) from transmit antenna(s)  328 . Because the distance between the transmit antenna(s)  328  and the energy receiver antenna(s)  330  is short, a substantial amount of transmission signal power can be received at the energy receiver antenna(s)  330  and converted for DC power use. One approach for receiving and converting such transmission signal power is described in U.S. Pat. No. 8,416,721, which is hereby incorporated by reference in its entirety. 
         [0024]      FIG. 4  illustrates matched energy receiver antennas substantially covering the surface of a wireless communication device  400 , according to an embodiment. As shown in panel A, the wireless communication device  400  includes transmit antenna(s)  402  and one or more matched energy receiver antenna(s)  404  covering a surface of the wireless phone device  400 . Illustratively, the frequency of the energy receiver antenna(s)  404  are deliberately matched to the transmission frequency of the wireless device&#39;s  400  own transmit antenna(s)  402 . Panel B illustrates a graph of the transmission signal power spectral envelope density versus frequency in the wireless communication device  400  having energy receiver antenna(s)  404  matching the frequency of transmit antenna(s)  402 . As shown, the frequency  401  of the energy receiver antenna is matched to the frequency center of the transmit antenna. The matching of the frequency of the energy receiver antenna(s)  404  to the transmission frequency of the transmit antenna(s)  402  permits the energy receiver antenna(s)  404  to most efficiently receive the transmission power radiated onto the surface of the wireless phone device  400 . 
         [0025]    In one embodiment, the surface of the wireless device  400  may be maximally covered by energy receiver antenna(s)  404 , except for areas needed for other critical functions, such as the screen, key pad, and transmit/receiver antennas. In another embodiment, energy receiver antenna(s)  404  may also be placed under the key pad, screen, etc. Trial and error and/or antenna software simulation may be used to determine the spacing needed between energy receiver antenna(s)  404  and transmit antenna(s)  402  to prevent interference to the transmission and receiving functions required by the wireless device  400 . More specifically, an effective distance between the energy receiver antenna(s)  404  and the transmit/receiver antenna(s) may be determined based on various optimization factors, such as maximizing the energy received, with the least amount of interference to the transmission, and placing the energy receiver antenna(s) at an effective distance to the transmit antenna(s)  404 . 
         [0026]    Experience has shown that, in a particular embodiment, a 34% power consumption reduction was achieved when the surface of a typical wireless device was covered with matched antenna(s), with the entire back surface and the left, right, and bottom sides covered with matched antenna(s) and only the keypad, screen and half an inch within the transmit/receiver antenna being left un-covered. Further, no significant transmission/reception signal impairment was measured. 
         [0027]      FIG. 5  illustrates mismatched energy receiver antennas substantially covering the surface of a wireless communication device  500 , according to an embodiment. As shown, the wireless communication device  500  includes antenna(s) for transmission of signals as well as energy receiver antenna(s)  504  configured to receive transmission power from the transmit antenna(s)  502  so that the transmission power can be converted to energy for use by the wireless communication device  500 . 
         [0028]    The energy receiver antenna(s)  504  are deliberately weakened so as to not efficiently receive the transmission power radiated by the transmit antenna  502 (s). A number of organic and non-organic materials such as human tissue, printed circuit boards, wireless device casing, are capable of absorbing radiated RF transmission power to varying degrees. For example, human tissue acts as an inefficient antenna which does not match a transmit antenna frequency center. In one embodiment, the energy receiver antenna(s)  504  may be constructed from such materials. 
         [0029]    In another embodiment, energy receiver antenna(s)  504  may be deliberately weakened by shifting the frequency center of the energy receiver antenna(s)  504  away from the frequency center of the transmit antenna(s)  502  by, e.g., calibrating the energy receiver antenna(s)  504  to be mismatched with the transmit antenna(s)  502 . Panel B illustrates a graph of the transmission signal power spectral envelope density versus frequency in the wireless communication device  500  having mismatched energy receiver antenna(s)  504 . This mismatching makes the energy receiver antenna(s)  504  less efficient at receiving the transmission power radiated onto the surface of the wireless device  500 . As a result, one or more mismatched energy receiver antenna(s)  504  may be placed next to the transmit/receiver antenna  502 , at a closer distance than matched energy receiver antennas could be placed, without affecting normal RF functions. Because transmission RF power degrades by distance squared, less efficient energy receiver antennas placed closer to the transmit antenna(s)  502  may actually be equal to or more efficient than matched energy receiver antennas placed further away from the transmit antenna(s)  502 . 
         [0030]    Illustratively, the wireless device  500  is maximally covered by the mismatched energy receiver antenna(s)  504 , except for regions needed for other critical functions, such as a key pad, display screen, and transmit/receiver antenna(s). In another embodiment, energy receiver antenna(s) may also be placed underneath the key pad and/or the display screen. If necessary to prevent interference to transmission/reception functions, the spacing between the energy receiver antenna(s)  504  and transmit/receiver antennas may be obtained by trial and error and/or antenna software simulation. 
         [0031]    Experience has shown that in a particular embodiment, in which a wireless devices with non-matching transmit antennas having different communication standards/frequencies than energy receiver antennas were placed in close proximity to the energy receiver antennas, the energy receiver antennas still received non-matching transmission power which could be converted to DC power. In addition, no substantial transmission/reception signal power degradation was measured. 
         [0032]      FIG. 6  illustrates combining matched and mismatched energy receiver antennas to substantially cover the surface of a wireless communication device  600 , according to an embodiment. As shown in panel A, the wireless communication device  600  includes two rows of mismatched, and deliberately less efficient, antenna(s)  604  placed close to the wireless device&#39;s  600  transmit antenna(s)  602 . As discussed, the deliberately less efficient antenna(s)  604  may be, e.g., made of materials capable of absorbing radiated RF transmission power but not interfering with transmission or reception of RF signals. The less efficient antenna(s)  604  may also have frequency center(s) that are mismatched with frequency center(s) of the transmit antenna(s)  602 . The wireless device  600  also includes rows of matched antennas  606  placed further away from the wireless device&#39;s  600  transmit antenna(s)  602  than the mismatched antenna(s)  604  are placed. As discussed, the matched antenna(s)  606  can receive radiated transmission power more efficiently than the mismatched antennas  604 . Panel B illustrates a graph of the transmission signal power spectral envelope density versus frequency in the wireless communication device  600  having both matched energy receiver antenna(s)  606  and mismatched energy receiver antenna(s)  604 . Once again, to prevent interference to the transmission/reception functions of the wireless device  600 , the spacing needed between energy receiver antenna(s)  604 ,  606  and transmit/receiver antenna(s) may be obtained by trial and error and/or antenna software simulation. By using both mismatched antennas  604  and matched antennas  606 , it is possible to maximize the space on the surface of the wireless device  600  on which energy receiver antennas are placed. 
         [0033]      FIG. 7  depicts use of energy receiver antennas as electrical shields in a wireless communication device  700 , according to an embodiment. As shown, the wireless communication device  700  includes a transmit antenna  710  and electronic circuitry components  740  mounted on a substrate  730 . The transmit antenna  710 , electronic circuitry components  740 , and substrate  730  may be similar to the transmit antenna  110 , electronic circuitry components  140 , and substrate  130  of the wireless communication device  100 , discussed above. Rather than the electrical signal shields  150  of the wireless communication device  100 , however, the wireless communication device  700  includes energy receiver antennas  750 . The energy receiver antenna(s)  750  may have any feasible shape, including the same shape as the electrical signal shields  150 . In addition to receiving radiated transmission power, the energy receiver antenna(s)  750  may also perform the same function as the electrical signal shields  150 , namely preventing internally generated electrical signals from radiating out and affecting the function of other devices and preventing externally generated electrical signals from radiating in to affect the function of the electronic circuitry components  740 . As a result, energy receiver antennas  750  may replace electrical signal shields which are grounded. Replacing such electrical signal shields with energy receiver antennas  750  permits maximal use of available space for energy receiver antennas. 
         [0034]    Advantageously, wireless devices disclosed herein include energy receiver antennas that receive the wireless devices&#39; own transmission signals that are radiated onto the surfaces of the wireless devices. The received transmission signals are then converted to DC power that can be provided to various components of the wireless devices. Doing so reduces power consumption by the wireless devices and extends battery life. 
         [0035]    While the forgoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof.