Abstract:
A low power super regenerative receiver and a method of reducing the power consumption of the low power super regenerative receiver are provided. The super regenerative receiver includes: an oscillator having a start-up time period starting oscillation that varies according to an existence of an input signal; and a power controller supplying power within the start-up time period of the oscillator.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     This application claims the benefit of Korean Patent Application Nos. 10-2007-0129172, filed on Dec. 12, 2007, 10-2008-0111207, filed on Nov. 10, 2008, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a super regenerative receiver, and more particularly, to a super regenerative receiver which reduces average power consumption by periodically turning on/off the power in correspondence with the power state of an oscillator which periodically turning on/off. 
     The present invention is derived from a research project supported by the Information Technology (IT) Research &amp; Development (R&amp;D) program of the Ministry of Information and Communication (MIC) and the Institute for Information Technology Advancement (IITA) [2005-S-106-03, Development of Sensor Tag and Sensor Node Techniques for RFID/USN]. 
     2. Description of the Related Art 
     Super regenerative receivers are known for their moderate sensitivity and low cost. Super regenerative receivers have been widely applied to remote control toys, alarm systems, and monitors. 
     Super regenerative receivers detect a signal based on a start-up time of an oscillator. The start-up time depends on the power and frequency of a signal received by an antenna. Even without the input signal, the oscillator may oscillate due to the thermal noise very slowly. 
     Conventional super regenerative receivers may be classified into two categories; general super regenerative receivers for over-sampling an input signal and synchronous super regenerative receivers for over-sampling an input signal only once. 
     SUMMARY OF THE INVENTION 
     It is required to further reduce power consumption of a receiver due to a demand to extend the lifetime of a wireless sensor network. However, current receiver architectures cannot meet such a low power requirement without degrading sensitivity. Conventional general super regenerative receivers and synchronous super regenerative receivers have difficulties in further reducing power consumption with currently available technologies. 
     The present invention provides a method of controlling duty cycle power as a quenching means in a super regenerative receiver so as to reduce average power consumption of the super regenerative receiver while maintaining selectivity and sensitivity thereof. The method comprises adjusting a duty cycle ratio, and periodically turning off the power of the super regenerative receiver, thereby reducing the power consumption of the super regenerative receiver. 
     According to an aspect of the present invention, there is provided super regenerative receiver comprising: an oscillator having a start-up time period starting oscillation that varies according to an existence of an input signal; and a power controller supplying power within the start-up time period of the oscillator. 
     The power controller may use a duty cycle to supply power, and a duty cycle ratio between a clock off period and clock on period of the duty cycle is changed by adjusting the frequency of the duty cycle. 
     The super regenerative receiver may further comprise: an insulation amplifier injecting a signal into the oscillator and providing reverse isolation of the input signal from the oscillator; an envelope detector detecting an envelope of the oscillator; and an amplifier amplifying the envelope, wherein the power controller is connected to the insulation amplifier, the oscillator, the envelope detector, and the amplifier. 
     A power off period may be extended until the frequency of the duty cycle is the same as a data rate of the input signal. 
     According to another aspect of the present invention, there is provided a method of reducing power consumption of a super regenerative receiver comprising an oscillator having a start-up time period starting oscillation that varies according to an existence of an input signal, wherein the method comprises: controlling power by supplying the power to the super regenerative receiver within the start-up time period of the oscillator. 
     The super regenerative receiver may further comprise: an insulation amplifier injecting a signal into the oscillator and providing reverse isolation of the input signal from the oscillator; an envelope detector detecting an envelope of the oscillator; and an amplifier amplifying the envelope, wherein the controlling of the power comprises: supplying the power to the insulation amplifier, the oscillator, the envelope detector, and the amplifier within the start-up time period of the oscillator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
         FIGS. 1A and 1B  are, respectively, block and timing diagrams of a conventional super regenerative receiver; 
         FIGS. 2A and 2B  are, respectively, block and timing diagrams of a conventional synchronous super regenerative receiver; 
         FIGS. 3A and 3B  are, respectively, block and timing diagrams of a super regenerative receiver for controlling a duty cycle, according to an embodiment of the present invention; 
         FIGS. 4A and 4B  are, respectively, block and timing diagrams of a super regenerative receiver for sequentially controlling a duty cycle, according to an embodiment of the present invention; and 
         FIG. 5  is a block diagram of a super regenerative receiver according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. Like reference numerals refer to the like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of the present invention. 
       FIGS. 1A and 1B  are, respectively, block and timing diagrams of a conventional super regenerative receiver  100 . Referring to  FIGS. 1A and 1B , the conventional super regenerative receiver  100  over-samples an input signal  101 . In this case, a quench frequency is required to be much greater than an input signal data rate R. A cut-off frequency of a low pass filter  140  is much larger than the input signal data rate R and much smaller than the quench frequency in order to remove a quench signal from a signal that passes through an envelope detector  130 . 
     Therefore, the quench frequency must be at least twice as large as the input signal data rate R. The input signal  101  that has passed through the low pass filter  140  is consequently demodulated, is amplified in a baseband amplifier  150 , and is recovered as a digital signal  161  by a slicer  160 . 
       FIGS. 2A and 2B  are, respectively, block and timing diagrams of a conventional synchronous super regenerative receiver  200 . Referring to  FIGS. 2A and 2B , the synchronous super regenerative receiver  200  samples an input signal only once. In this case, a quench frequency is almost the same as the input signal data rate R that rapidly increases. In more detail, the conventional synchronous super regenerative receiver  200  may receive a greater number of bits than the conventional super regenerative receiver  100  shown in  FIGS. 1A and 1B  during the same period of time, thereby increasing a data transmission rate. 
     The conventional super regenerative receiver  100  shown in  FIGS. 1A and 1B  expresses data of 1 bit through at least several clock cycles by over-sampling an input signal of 1 bit and performing at least several clock cycles. Meanwhile, the conventional synchronous super regenerative receiver  200  shown in  FIGS. 2A and 2B  expresses data of 1 bit by sampling the input signal of 1 bit only once, thereby receiving a much greater number of bits compared to the conventional super regenerative receiver  100  shown in  FIGS. 1A and 1B  during the same period of time, so that a data transmission rate increases. 
     A data rate loop filter  270  of the conventional synchronous super regenerative receiver  200  is used to synchronize the input data and quench signal. 
     A basic process performed by a super regenerative receiver of the present invention comprises periodically turning on and off the overall power of the super regenerative receiver, unlike the conventional concept of the conventional super regenerative receivers shown in  FIGS. 1 and 2  of periodically turning on and off an oscillator. 
     The average power consumption of the super regenerative receiver of the present invention is further reduced by extending a period when the power of the super regenerative receiver is turned off. The period when the power of the super regenerative receiver is turned off may be extended until the input signal data rate R is the same as a clock frequency of a control signal for controlling the overall power. Hereinafter, the super regenerative receiver of the present invention will be described. 
       FIGS. 3A and 3B  are, respectively, block and timing diagrams of a super regenerative receiver  300  for controlling a duty cycle, according to an embodiment of the present invention. 
     Referring to  FIG. 3A , the power of the super regenerative receiver  300  periodically turns on and off, unlike the conventional method of periodically turning on and off an oscillator  320 . In more detail, the super regenerative receiver  300  detects a signal during a start-up period when the oscillator  320  starts oscillating. 
     The power of the super regenerative receiver  300  turns off while the oscillator  320  is turned off, thereby reducing the consumption power from a power supply. Furthermore, the average power consumption of the super regenerative receiver  300  is further reduced by extending a period during which the overall power of the super regenerative receiver  300  is turned off. 
     The amount of power consumed by the super regenerative receiver  300  may be adjusted by controlling a ratio of the duty cycle frequency of power control clocks  372  and  472 . The ratio of the duty cycle frequency may be controlled by adjusting the duty cycle frequency. In more detail, the duty cycle frequency of the power control clocks  372  and  472  is extended so that the duty cycle frequency is the same as that of an input data rate. The input data rate is the number of bits transmitted for a second. 
     The super regenerative receiver  300  comprises an insulation amplifier  310 , an oscillator  320 , an envelope detector  330 , an amplifier  340 , a slicer  350 , and a power controller  360 . 
     The insulation amplifier  310  provides reverse isolation between the oscillator  320  and an antenna and injects a signal into the oscillator  320 . 
     The oscillator  320  detects the signal based on a start-up time difference. The oscillator  320  is adjusted by a quench signal generator (see  FIGS. 1A and 2A ) for generating a signal that blocks the oscillator or the power controller  360 . 
     The envelope detector  330  detects an envelope of the oscillator  320 . 
     The amplifier  340  amplifies an envelope signal of the oscillator  320  so that the oscillator  320  properly operates. 
     The slicer  350  recovers a digital signal from the envelope signal amplified by the amplifier  340 . 
     The power controller  360  is connected to the insulation amplifier  310 , the oscillator  320 , the envelope detector  330 , and the amplifier  340 , and generates a duty cycle signal to turn on and off the overall power of a circuit. 
     Only when the power controller  360  turns on the power of the super regenerative receiver  300 , is the signal received by the antenna injected into the oscillator  320  through the insulation amplifier  310 . Then, the oscillator  320  samples the signal injected by the insulation amplifier  310  and starts oscillating. 
     The oscillator  320  starts oscillating a small signal before the power controller  360  turns on the power of the super regenerative receiver  300 . Even after the amplifier  340  amplifies the envelope signal of the oscillator  320 , a signal level lower than a reference voltage is maintained. 
     Referring to  FIG. 3B , an RF input  371  is a OOK modulated RF signal. The power control clock  372  is a duty cycle power control signal of the power controller  360 . 
     The converted digital signal that passes through the slicer  350  is “0”. However, when the antenna receives an input signal, the oscillator  320  oscillates much faster before the overall power of the super regenerative receiver  300  turns off ( 373   a ). In this case, the oscillated signal has a very large amplitude and is saturated. The digital signal is detected as ‘1’ ( 374   a ). 
       FIGS. 4A and 4B  are, respectively, block and timing diagrams of a super regenerative receiver  400  for sequentially controlling a duty cycle, according to an embodiment of the present invention. The super regenerative receiver  400  is an improvement of the super regenerative receiver  300  shown in  FIG. 3A . The elements shown in  FIG. 4A  corresponding to those shown in  FIG. 3A  are substantially identical or similar to each other and thus a detailed description thereof will not be repeated here. 
     A duty cycle signal  473  for adjusting the power on and off of an oscillator  420  is generated by a power control clock  472 . The duty cycle signal  473  is smaller than the power control clock  472 . 
     In more detail, the duty cycle signal  473 , via a delay unit  461 , is applied to the oscillator  420 , so that other elements of the super regenerative receiver  400  are turned on and are stabilized before the oscillator  420  samples an input signal. 
     The delay unit  461  delays a power control clock input by the power controller  460 , generates the delayed power control clock, and generates the power control clock from the oscillator  420  through an AND gate  462 . (in claims: “a delay unit connected to the power controller and delaying the power supplied by the power controller”—same as description of delay unit  461  above? YES!!) In more detail, the super regenerative receiver  400  uses the delay unit  461  to turn other elements on and stabilize them before the oscillator  420  samples the input signal. 
     The super regenerative receiver  400  may further comprise a calibration circuit (not shown) for adjusting an oscillation frequency and a Q factor of the oscillator  420  in order to improve the performance thereof. 
     In this case, during calibration and detection periods, the super regenerative receiver  400  is turned on and adjusts the Q factor and oscillation frequency. During the detection period, the super regenerative receiver  400  performs the operation described above with reference to  FIG. 4  without the calibration circuit. An example of the calibration circuit is a digital calibration circuit. The calibration circuit is a circuit for detecting an oscillating frequency, if the frequency is deviated, adjusting a capacitance component of the oscillator  420 , and allowing the oscillator  420  to oscillate at a predetermined frequency. 
     The calibration period is a period when the oscillator  420  oscillates at the predetermined frequency while the super regenerative receiver  400  is turned off. In more detail, the calibration period excludes the detection period and a period when the super regenerative receiver  400  is turned on. Furthermore, the detection period is a period when the oscillator  420  oscillates in a steady state and detects a signal that passes through an envelope detector. 
       FIG. 5  is a block diagram of a super regenerative receiver  500  according to an embodiment of the present invention. 
     Referring to  FIG. 5 , the super regenerative receiver  500  comprises an oscillator  530  and a power controller  510 . 
     The oscillator  530  depends on whether an input signal has an oscillation start-up time or not. The power controller  510  controls the supply of power to an insulation amplifier  520 , an oscillator  530 , an envelope detector  540 , and an amplifier  550  only within the start-up period of the oscillator  530 . 
     Alternatively, the super regenerative receiver  500  may further comprise a delay unit (not shown) as described with reference to  FIGS. 4A and 4B . 
     The delay unit having one end connected to the power controller  510  and another end connected to the oscillator  530 , supplies power to the oscillator  530  after the power controller  510  stably powers up the insulation amplifier  520 , the envelope detector  540 , and the amplifier  550 . 
     However, the present invention is not limited thereto and other elements for realizing the super regenerative receiver  500  may be connected to the power controller  510  and may be turned on and off in order to reduce power consumption. 
     The present invention can also be embodied as computer readable code on a computer readable recording medium. The computer readable recording medium is any data storage device that can store data which can be thereafter read by a computer system. Examples of the computer readable recording medium include read-only memory (ROM), random-access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, optical data storage devices, and carrier waves. The computer readable recording medium can also be distributed network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. 
     The present invention uses a power controller used as a quenching means in a super regenerative receiver to reduce average power consumption of the super regenerative receiver while maintaining selectivity and sensitivity of the super regenerative receiver. Furthermore, by adjusting the duty cycle ratio of the power controller, it is possible to easily adjust the average power consumption of a wakeup receiver so as to meet requirements of the wakeup receiver. The present invention is also suitable for any other low data rate or low power applications. 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.