Abstract:
A passive amplifier for use with enhanced power supplies, signal preamplifiers and power amplifiers in communications systems particularly in mobile phones, laptop computers and other battery-powered and battery-limited devices. The passive amplifier can be used as an attachment to electric appliances or other power consuming equipment to significantly reduce the electric power requirements of such equipment. These passive amplifiers do not require an outside source of power and can be used to elevate battery power outputs and serve as either low noise signal preamplifiers or transmit power amplifiers for higher performance and extended battery life. Passive amplifier technology is either electromagnetic or dielectric in nature with component parts limited to inductive, capacitive and resistive components. Dielectric amplifier prototypes have gain values in the range of the 10 dB level so as to be useful in communications applications and power amplification.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is based on and claims priority to U.S. Provisional Patent Application Ser. No. 61/438,469 filed Feb. 1, 2011. 
     
    
     BACKGROUND 
       [0002]    Wireless communications systems have been deployed by several companies, such as HierComm, Inc., in the 5 GHz band and are currently operating profitably and growing. A companion 4.9 GHz band wireless public safety network with both mobile and fixed capabilities has also been recently deployed and is in operation. One type of low noise signal preamplifier has been used to great effectiveness and is the basis for an issued US patent, High Gain Antenna and Magnetic Preamplifier, U.S. Pat. No. 7,528,795 B2, May 5, 2009, the disclosure of which is incorporated herein by reference. 
         [0003]    Despite the early success of the above broadband commercial and public safety networks, it has become clear that further growth in performance and cost effectiveness depended on the development of better low noise preamplifiers that would further increase radio range by improving the sensitivity of radio receivers. In mobile battery power source dependent applications, the need for low power usage amplifiers was particularly important to extend battery life. Work on a magnetic low noise amplifier led to the patent referenced above. The work described above to provide a low power usage amplifier also led to the dielectric amplifier technology of the present disclosure. 
         [0004]    Although the low power usage amplifier was initially proposed for communications applications as described above, a second major market exists in the electric power (energy) saving market. The same passive dielectric amplifier may be designed for operation in the 60 Hz frequency band and used to save energy through attachment to electric power consuming appliances, such as refrigerators, electric heaters and lighting fixtures. In an embodiment of an amplifier with demonstrated power gains of 4 to 1, a 500 watt appliance with an attached passive dielectric amplifier would consume only 125 watts. 
       SUMMARY 
       [0005]    The present disclosure relates to passive amplifiers for application as energy saving power supplies, signal preamplifiers and power amplifiers in communications systems particularly in mobile phones, laptop computers and other battery-powered and battery-limited devices. The passive amplifiers also have application as an energy saving attachment to an electric appliance These passive amplifiers do not require an outside source of power and can be used to elevate battery power outputs and serve as either low noise signal preamplifiers or transmit power amplifiers for higher performance and extended battery life. 
         [0006]    Passive amplifier technology as proposed here is either electromagnetic or dielectric in nature with component parts limited to inductive, capacitive and resistive components. Dielectric passive amplifiers are particularly desirable because of their easier extension to higher frequency RF and microwave communications and their potential for miniaturization. The basic dielectric amplifier technology has been proven theoretically and by simulation and bench experimentation. The dielectric amplifier prototypes developed in accordance with the present disclosure are able to increase the gain of the amplifier to at least the 10 dB level so as to be useful in communications applications. 
         [0007]    Currently, the basic dielectric amplifier function of the disclosure has been verified theoretically and by follow-on simulation and bench experimentation. Single stage prototypes were designed, constructed and tested at 60 Hz and 100 kHz. Simulation studies have been carried out at 100 kHz, 915 MHz and 2.4 GHz. Paper designs have been completed up to 5.8 GHz. In each case, the dielectric amplifier has demonstrated significant power gain without the need for an outside power source. The only requirement is an input signal in communications applications or a lower power input in electric appliance applications. 
         [0008]    Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The drawings illustrate the best mode presently contemplated of carrying out the disclosure. In the drawings: 
           [0010]      FIG. 1  is a circuit schematic of a prior art passive voltage amplifier; 
           [0011]      FIG. 2  is a circuit schematic of a passive amplifier of the present disclosure that incorporates the load and positive feedback into the amplification circuit; 
           [0012]      FIG. 3  is a simulation circuit for the circuit diagram of  FIG. 2 ; 
           [0013]      FIG. 4  is a graphic illustration of the input and output voltage source illustrating the amplification of the signal by the passive amplifier of the present disclosure; 
           [0014]      FIG. 5  is a schematic illustration including the dielectric amplifier in a positive feedback circuit; and 
           [0015]      FIG. 6  is a circuit diagram of a power combiner. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The original concept of a dielectric passive amplifier was derived from a reference in a text,  The Science of Radio , by Professor Paul J. Nahin of the University of New Hampshire [Nahin 2001]. In the referenced article, the article describes a circuit that provides a voltage gain greater than unity made up of only passive resistor and capacitor components, as illustrated in  FIG. 1 . A mathematical proof and a voltage gain formula for the circuit shown in  FIG. 1  are also provided along with an Electronics Workbench simulation in the referenced text. An example circuit with an input voltage at 1.882 GHz is displayed in the text and test results shown. A typical maximum voltage gain for the circuit of  FIG. 1  of 1.15 is recorded. A fatal weakness of the Nahin circuit shown in  FIG. 1  is its inability to drive a typical 50 ohm (or 75 ohm) communications load  13  connected across terminals  10  and  12 . When an external 50 ohm load  13  is applied across terminals  10  and  12 , the voltage gain disappears and becomes a loss. The circuit also is mismatched with a typical 50 ohm communications source. The present disclosure has solved both of these problems by integrating a 50 ohm resistor and an input impedance (Z) matching circuit into the circuit design. With this change, the dielectric circuit element is able to provide 50 ohm impedance matching on both the input and output of the circuit element. 
         [0017]      FIG. 2  illustrates the circuit schematic of a first embodiment of a passive dielectric amplifier  15  of the present disclosure. As illustrated in  FIG. 2 , a load resistance  14  is included as part of the circuit and forms part of the voltage divider including the resistor  16 . Unlike the embodiment shown in  FIG. 1 , the load resistance  14  forms part of the voltage divider rather than being connected across the terminals  10  and  12  shown in  FIG. 1 . In the embodiment shown in  FIG. 2 , the load resistor  14  is a 28 ohm resistor to serve a 500 watt, 120 volt load in an appliance energy saving application while the resistor  16  is a 1200 ohm resistor. 
         [0018]    A pair of capacitors  18 ,  20  are connected to voltage source  22  through an inductor  24 . Positive feedback is created through feedback line  26  which is connected to inductor  28  that forms part of a divider network with inductor  30 . The voltage source  22  is connected to the junction between the inductors  28  and  30  through resistor  32 . By incorporating the resistive load  14  directly into the circuit rather than connecting the resistive load across an output terminal, the passive amplifier of the present disclosure allows the load to be driven unlike the prior embodiment disclosed in  FIG. 1 . 
         [0019]      FIG. 3  illustrates an alternate embodiment of the passive amplification circuit of  FIG. 2 . The embodiment shown in  FIG. 3  is meant for simulation purposes only and includes an operational amplifier  34  contained in the feedback network. Since the operational amplifier  34  requires power to operate, it is clear that the circuit in  FIG. 3  is for simulation purposes only and is not meant to be a circuit implemented as part of a functioning amplifier. Similar components are referred to by common reference numerals with respect to  FIGS. 2 and 3 . In the embodiment of  FIG. 3 , the operational amplifier  34  is positioned between the feedback line  26  and the voltage source  22 . 
         [0020]      FIG. 4  illustrates the simulation output of the schematic circuit illustration of  FIG. 3 , As can be seen in  FIG. 4 , the output  36  across the resistance  14  is amplified relative to the voltage input signal  37 . The output signal  36  is recorded at the output terminal  38  of  FIG. 3  while the input signal  37  is right from the 60 Hz voltage source  22 . 
         [0021]    By incorporating the load resistance  14  as part of the voltage divider, the amplifier of the disclosure incorporates a range of dielectric amplifier circuit elements all of which provide a voltage gain. These designs include amplifier circuits at 60 Hz, 100 kHz, 915 MHz, 2.4 GHz, 4.9 GHz and 5.8 GHz. Circuit simulations were carried out at all of these frequencies to verify the voltage gain, which is about 4.5 in the sample output of these simulations shown in  FIG. 4 . Thus, the amplifier circuit can be used in power supply applications with input voltages having a frequency range between 50 Hz and 500 kHz. In communication applications, the amplifier can be used with inputs having a frequency range between 500 kHz and 10 GHz. 
         [0022]    With this verification of the dielectric circuit element design, a proposed program can be designed to enhance the voltage/current/power gain of the new dielectric amplifier to a level where it will be extremely useful in communications. It plans to accomplish this gain enhancement in two parallel complementary efforts:
       1. Developing multi-stage, cascaded dielectric amplifier circuits;   2. Employing positive feedback technology to increase the voltage/power gain of a single stage dielectric amplifier circuit.       
 
         [0025]    A multi-stage version of the dielectric amplifier element has promise of increasing the demonstrated 15% voltage gain and 32% power gain of a single dielectric amplifier element to a 6 dB power amplifier in a five-stage configuration. A 10-stage configuration has the potential of creating a 10.9 dB power amplifier. 
         [0026]    The objectives of the present design are twofold:
       1. Extend the current proven dielectric amplifier element technology to power gain levels of 10 dB or greater using cascaded multi-stage power amplifier configurations.   2. Extend the same dielectric technology to higher power gains for power supply enhancement using positive feedback techniques.       
 
         [0029]      FIG. 5  illustrates a detailed implementation of the positive feedback version of the dielectric amplifier with an R-C circuit  50  incorporating the resistive load (R) from  FIG. 1  shown as the output section of the amplifier. An output voltage from the R-C circuit  50  is fed back to a power combiner  52  along feedback line  54  as a positive input to the power combiner  52 . The power combiner  52  combines this feedback with the input signal along line  56  to form a positive feedback amplifier. 
         [0030]    An impedance matching circuit  58  is required for the input signal or power source available on input line  60  (Z-Match Circuit  1 ) to match the source for efficient power transfer to the amplifier. A similar impedance matching circuit (Z-Match Circuit  2 )  62  is required to match the output of the power combiner  52  with the R-C circuit  50 . These impedance matching circuits  50 ,  62  are well known highpass or lowpass (L-C) matching networks with resonance characteristics. 
         [0031]      FIG. 6  provides a detailed circuit diagram of the power combiner  52  which is a dual primary, single secondary transformer  64  wound on a high permeability, zinc manganese ferrite toroid core  66 . Zinc manganese ferrite cores  66  are useful in the frequency range 10 kHz to 500 kHz. Other ferrite or non-ferrite core materials may be used in other frequency ranges. Various core materials would also be used for a range of amplifier power levels. The transformer is wound in parallel, so that the two primary inputs are added in the secondary winding. 
       Technical Approach 
       [0032]    As previously stated, appropriate parameters have been calculated to have the single stage circuit of  FIG. 2  provide a 15% voltage gain and 32% power gain over a wide range of frequency bands. For amplifier application, the proposed technical approach would cascade multiple dielectric circuit elements suitably matched to avoid loading into a higher gain multi-stage amplifier. In the modified circuit configuration, the input and output impedances are essentially resistive and virtually identical in value, so that quarter-wave microstrips will provide very low loss impedance matching. Given the parameters involved, development of a cascaded element multi-stage circuit can be readily accomplished. 
         [0033]    The technical approach employing positive feedback to enhance power gain for lower frequency power supply enhancement is more complex but easily understandable. The gain equation for a positive feedback amplifier differs significantly from the conventional negative feedback amplifier [Bode 1945]. 
         [0000]    
       
         
           
             
               Positive 
                
               
                   
               
                
               Feedback 
                
               
                   
               
                
               Gain 
             
             
               G 
               = 
               
                 μ 
                 / 
                 
                   ( 
                   
                     1 
                      
                     
                       - 
                     
                      
                     μβ 
                   
                   ) 
                 
               
             
           
         
       
       
         
           
             
               Negative 
                
               
                   
               
                
               Feedback 
                
               
                   
               
                
               Gain 
             
             
               G 
               = 
               
                 μ 
                 / 
                 
                   ( 
                   
                     1 
                     + 
                     μβ 
                   
                   ) 
                 
               
             
           
         
       
     
       Where 
       [0000]    
       
         
           
             G—closed loop voltage gain 
             μ—forward gain 
             β—feedback gain 
           
         
       
     
         [0037]    From the above, it can be shown that in a negative feedback configuration, any set of positive gain parameters will result in a reduced closed loop gain. The positive feedback is more complex. Any positive product of μβ greater than two (2.0) will also reduce gain and invert the signal. Gain enhancement is achieved with μβ product values in the range of 0.1 to 1.9. μβ product values exceeding 1.1 will invert the signal. The quantity μβ is often designated as the feedback factor. Feedback factors in the range of 0.9 to 1.1 are usually unstable. A practical range of feedback factor values is 0.5 to 0.85. Example of close loop gain values are shown below. 
         [0000]    
       
         
               
               
               
             
           
               
                   
               
               
                 μβ 
                 Voltage Gain 
                 Power Gain 
               
               
                   
               
             
             
               
                 0.85 
                 6.67 (8.2 dB) 
                 16.4 dB 
               
               
                 0.70 
                 3.33 (5.2 dB) 
                 10.4 dB 
               
               
                 0.50 
                 2.00 (3.0 dB) 
                  6.0 dB 
               
               
                   
               
             
          
         
       
     
         [0038]    To achieve a voltage gain of 8.2 dB with a forward μ gain of 1.15 in a dielectric amplifier element, a feedback gain β of 0.74 would be required. 
         [0039]    Positive feedback circuits are traditionally considered unstable and sometimes equivalent to oscillators. Positive feedback, however, can be a very useful technology for amplifier gain enhancement. It has been used for over 100 years in classic magnetic power control amplifiers which were pioneered by the U.S. Navy after World War II [Geyger, 1957]. While different in operating principle from classic magnetic amplifiers, currently available magnetic amplifiers still employ positive feedback circuits. It is also important to point out that analytical techniques developed for the design of negative feedback amplifiers, such as Bode plots, can also be used to insure stability in positive feedback circuits. 
         [0040]    In the transmit power amplification, the principal advantage will be equal or higher power with little or no additional battery power consumption. In low noise figure preamplifiers, the advantage will relate to lowered receiver sensitivity resulting from the inherently quiet nature of such circuits. Battery life extension will take the form DC/AC/DC conversions since the amplifier operates only in AC. Any conversion losses will be more than compensated by the power gain of the low frequency power amplifier. 
       Communications Applications 
       [0041]    Although passive dielectric amplifiers, as described here, are believed to have a wide range of communications applications, they will probably have their greatest impact on mobile Ad Hoc networks where peer-to-peer transmissions predominate, such as an Ad Hoc communications system at 4.9 GHz for public safety application. From a market size point of view, the use of the passive dielectric amplifiers will be most valuable in mobile phone networks where battery life is limited. Passive amplifier technology will improve such mobile networks by:
       1. Extending transmission range with higher transmission output powers and with greatly reduced battery power consumption.   2. Extending transmission range with improved receiver sensitivity from low noise preamplifiers as described above.   3. Extending battery life through power amplification as described above.       
 
         [0045]    All three of the above improvements are also targets for the passive magnetic amplifier of the present disclosure. As previously stated, however, dielectric amplifiers have much greater potential for higher frequency UHF and microwave communications and lend themselves to miniaturization for lighter weight in mobile applications. In addition to the above improvements for mobile communications devices, passive dielectric amplifiers will also be very useful in fixed remote battery-based relay stations in the new relay-based network architectures. 
         [0046]    Aside from applications in communications, other needs for longer life power sources exist in the world of unmanned air vehicles (UAVs) and more particularly Micro Air Vehicles (MAVs) which employ rechargeable Li-ion batteries as power sources. Extension of battery life using the proposed dielectric power amplifier could greatly extend the range and operating time of such MAVs for enhanced military effectiveness. 
         [0047]    The amplifier of the present disclosure can be used for both the transmit power amplifier and the power amplified battery power source. Both uses will be of a form suitable for portability and demonstrations at selected locations. Both the cascaded multi-stage and the positive feedback gain enhancement technologies will be employed for both objectives with the purpose of selecting which is most suitable for each application. 
       Other Applications 
       [0048]    Although the passive dielectric amplifier shown in the Figures is described as being particularly useful in a wide range of communications applications, it should be understood that the amplifier could also be utilized in various other types of situations in which a fixed load is being driven by a power supply or an AC power source in a commercial building or place of residence. The dielectric amplifier shown in the drawing of  FIG. 2  is a very low power consuming amplifier, which has application in almost any embodiment in which a load is driven by a battery power supply. An entire class of applications for the dielectric amplifier is available for low power consumption operating at 60 Hz. 
       Conclusions 
       [0049]    Passive dielectric amplifier technology could have a profound impact on communications in the coming years. As modern communications systems become more mobile, there is a greater need for more efficient use of power sources. The most critical step in dielectric amplifier development, the proof of passive dielectric voltage amplification, has already been demonstrated theoretically, by simulation and bench experimentation. The proposed next research steps here, multi-stage amplification and positive feedback gain enhancement, while challenging have a relatively high probability of success.