Abstract:
The invention discloses a system for improving performance of the RF amplification stage of communication receivers by accounting for the signal environment of the RF amplifier. The linearity, gain and power supply voltage of the RF amplification stage of the communication receiver is adjusted to produce an optimal signal into the succeeding narrow-band amplification stage(s). The adjustment of the RF stage includes mechanisms such as adjusting the RF amplifier power supply level using a DC to DC converter. It also includes allowing distortion in the RF amplification stage if the distortion in the RF amplification stage does not affect the target signal. For example, if there were a strong signal that fell within the same band as the target signal, amplification would be allowed to be so high that it distorted the undesired signals, but not the tined signals. If the desired signal is the predominant signal, within the RF amplifier&#39;s band, then the amplifier gain may be increased only to the point where distortion is detected.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to communications devices that receive electronic communication transmissions and in particular to personal communications systems, processes and devices that minimize power consumption by adjusting amplifier linearity and dynamic range.  
           [0003]    2. Related Art  
           [0004]    Portable electronic devices have become part of many aspects of personal, business, and recreational activities and tasks. The popularity of various portable personal electronic communications systems, such as portable phones, portable televisions, and personal pagers, continues to increase. As the popularity of portable electronic systems has increased, so has the demand for smaller, lighter, and more power efficient devices.  
           [0005]    Amplification of received electronic signals is a function performed in many portable electronic systems. Amplification circuitry tend to dissipate significant amounts of power and generate significant amounts of heat. It is common practice to design the Radio Frequency (RF) amplification portion of receiver circuitry within portable electronic communication devices to worse case, or one amplifier fits all, signal environment design standards. These standards dictate that the “front end” RF amplifier be designed as a compromise between maximum amplification, and preserving linearity of nearby transmissions that are being received.  
           [0006]    Designing receiver circuitry to worse case design standards is common for several reasons. First, receiver amplifiers are designed to worst case specifications because manufacturers generally want their receiving device to have the maximum range possible without distorting the received signal of a nearby transmission. If a portable communication device has a greater range than a competing model, a significant marketplace advantage is obtained. If the communications receiver distorts nearby transmissions, however, it may be perceived as being of inferior quality.  
           [0007]    Traditionally, power savings in receiver design has received secondary emphasis in the design of portable electronics equipment. More design effort has been expended on the broadcast portions of portable communication devices because the broadcast portions of the electronics generally consume considerably more power than the receiver circuitry. Because of this higher power consumption, improving the power consumption of the broadcast may realize significant power savings. Conversely, the receiver circuitry consumes less power. Therefore, reducing the power requirements of the receiver results in less improvement. However, if RF amplifiers for the receiver circuitry could be designed to optimally amplify the signals within their bands, amplification of received signals could be accomplished more efficiently and performance improvements could be realized.  
         SUMMARY  
         [0008]    This invention addresses problems related to power consumption by dynamically adjusting the gain, range, and linearity of the receiving amplifier. The adjustment of the RF amplifier is based on the desired signal received and what portion of the overall signal the desired signal comprises. By optimally amplifying the desired signal received while minimizing power consumption, the optimal amplification is achieved.  
           [0009]    A front end communication amplifier amplifies a band of radio signals that are received by an antenna. The amplified band of signals are then downconverted. The desired signal is extracted from the band of signals and amplified prior to demodulating and decoding the information in the signal. The circuits that amplify the RF Signal are commonly designed for worst case performance, so the RF amplifier stage is designed for maximum gain and maximum linearity, even though the signal being received may not require maximum gain or linearity. The RF amplifier commonly stays in a maximum gain, maximum linearity mode even though the signal being received could be better amplified by changing the parameters of the amplifier.  
           [0010]    For example, it is desirable to amplify the signal intended to be received as much as possible in the front end, or RF amplification stages. Applying amplification at the front end is desirable because the farther down the amplification chain that a signal is amplified, generally the noisier the signal becomes. It is therefore usually advantageous to amplify a signal as much as possible in the front end of the amplification chain. Significant performance improvements of the receiving portion communications receiving devices are available if the parameters of the front end RF amplifier are tailored to the signal environment. Because of the performance improvement available there is a need for improved front end amplification control in communications receivers.  
           [0011]    Other systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims. 
       
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0012]    The invention can be better understood with reference to the following figures. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views  
         [0013]    [0013]FIG. 1 is a prior art graphical illustration of a communications receiver optimizing the power consumption.  
         [0014]    [0014]FIG. 2 is a prior art block diagram of the circuitry of a communications optimizing power consumption.  
         [0015]    [0015]FIG. 3 contains graphs of maximum linearity and maximum gain signals for different amplifier power supply levels.  
         [0016]    [0016]FIG. 4 is a group of graphical representations, of example of illustrative signals that may be within the amplification band of a wide band amplifier.  
         [0017]    [0017]FIG. 5 is a series of circuit schematics illustrating several methods of measuring amplifier parameters.  
         [0018]    [0018]FIG. 6 is a block diagram illustrating the function of a DC to DC converter.  
         [0019]    [0019]FIG. 7 is a graph illustrating the relationship between the ratio of narrow-band power and wide-band power versus the amount of desired signal present within a wide-band signal.  
         [0020]    [0020]FIG. 8 is a block diagram of an embodiment showing several variations in elements.  
     
    
     DETAILED DESCRIPTION  
       [0021]    [0021]FIG. 1 is a prior art graphical illustration of a communications receiver optimizing power consumption. A communications receiver  100 , receives four broadcasts, comprising signal A  102 , signal B  104 , signal C  106 , and signal D  108 , at an antenna  110 . The communications receiver  100 , has a frequency band selector  112 . Utilizing the selector  114 , an operator of the communications receiver  100  may select a broadcast frequency between a lower frequency limit  116  and an upper frequency limit  118 , by position the selector  114 . In this manner broadcast frequencies A  102 , B  104 , C  106 , or D  108  may be selected by positioning selector  114  on the points of the frequency band selector representing the broadcast frequencies A  102 , B  104 , C  106 , or D  108  (e.g. positions  120 ,  122 ,  124  or  126 , respectively). The communication receiver  100  receives and amplifies a frequency band between the lower frequency limit  116  and an upper frequency limit  118 , and may select a target broadcast, for example signal A  102 , B  104 , C  106 , or D  108 .  
         [0022]    [0022]FIG. 2 is a block diagram of the circuitry of a radio receiver  200 . An antenna  101  receives broadcast signals  123 , that are then passed to a wide-band amplifier  105 . The frequencies amplified by the wide-band amplifier  105  may represent different channels that the receiving unit is capable of receiving. After a signal is amplified in the wide-band amplifier  105 , the amplified signal is passed to an image rejection mixer  107 . The image rejection mixer  107  accepts the signal from the wide-band amplifier  105  and multiplies it with a frequency from a local oscillator  106 , in order to translate the received signal to a lower frequency. The image rejection mixer  107  rejects one of the image frequencies produced by the mixing process.  
         [0023]    The translated frequency from the image rejection mixer  107  is then passed to a band-pass filter  109  that may be used to select the desired individual broadcast signal to be received. By selecting a individual broadcast signal and mixing it with a local oscillator signal, thereby translating it to a frequency that may be used by the narrow-band amplifier, the individual broadcast signal is acquired. The filtered signal from the band-pass filter  109  is then coupled through the coupling capacitor  111  and provided to the narrow-band amplifier  113 . The narrow-band amplifier  113  may then amplify the desired signal. The narrow-band amplifier  113  may be designed to be able to amplify the bandwidth of the selected communications channel. Conversely, the wide-band amplifier  105  may be designed to concurrently amplify a much wider bandwidth of signals to include several channels.  
         [0024]    The output of the narrow-band amplifier  113  is coupled into the demodulator  115 , which extracts the information from the signal coupled into it. The output of the demodulator  115 , such as an audio signal, is then coupled into an audio amplifier  117 . The output from the audio amplifier  117  is then connected to a speaker  119  to generate sounds for perception by users.  
         [0025]    The gain of the wide-band amplifier  105  may be fixed or controlled by an automatic gain control (AGC). If the gain of the wide-band amplifier is fixed, the gain will be selected at a high enough value so that weak signals might be effectively amplified, yet at a low enough value so that strong signals will not saturate the amplifier. If the gain is set by an AGC circuit, then the amplifier may attempt to regulate the amplification in such a way that the maximum amplification may be applied without distorting the signal coupled to it. An AGC circuit may commonly attempt to achieve maximum amplification without distorting the signal coupled into it, for example, by maintaining the largest signal in its band at a point just below the point where the signal would distort. In other words, the AGC commonly functions by measuring the largest signal within the band-pass of the amplifier and trying to maintain the signal at an amplitude less than an amplitude that may cause distortion. One of the difficulties is that an AGC commonly may measure the strongest signal within the band and not necessarily the signal that is the selected signal of interest.  
         [0026]    [0026]FIG. 3 illustrates the amplification and distortion of signals. The graph  201  depicts a signal  205  that is being output from an amplifier, such as a wide-band amplifier. The signal  205  is approaching the limit of the output range of the amplifier. Typically the output range of such an amplifier is limited by it&#39;s power supply. In the illustrated graph  201 , the power supply voltage of the amplifier is V MAX    215 . The amplified waveform  205  approaches the V MAX  limit within a few percent. As excursions of the waveform  205  approach V MAX    215 , the waveform  205  is distorted by the amplifier. The result of amplifying a waveform approaching the power supply limits of an amplifier is nonlinearity of the resultant signal  205 . The resulting amplified signal may become nonlinear because, in the regions near the maximum and minimum power supply voltages, the amplifier is nearing its saturation or cutoff regions and the gain of the amplifier is decreasing. An amplifier&#39;s characteristics are commonly substantially non-linear in the operating regions near saturation and cut off.  
         [0027]    If the amplitude of the waveform is reduced so that the output waveform excursions no longer approach the limits of the amplifier power supply, the waveform may be linearly amplified similar to waveform  207 . The excursion of the waveform  207 , between 10% and 90% of the power supply voltage V MAX    215 , is in the linear operation region of the amplifier. The maximum value of the signal does not approach the power supply voltages V MAX    215  or V MIN    217 . Therefore, the waveform  207  may be undistorted as shown in FIG. 2. The illustrative waveform  207  occupies the full undistorted range of the amplifier, and hence the waveform  207  is amplified linearly. In contrast, a waveform may occupy only a relatively small portion of the possible of the possible peak to peak amplitude. Such a waveform, which occupies only a relatively small portion of the maximum amplifier range, is shown as waveform  213 . The waveform  213  may occupy less than a full range output range of the amplifier, either because the amplifier cannot amplify it further or because a signal of the magnitude of waveform  213  is all that is needed to drive the next stage of amplification. If the signal  213  occupies only a relatively small range of the amplifier&#39;s capability, then there may be nothing to be gained by having a range of V MAX    215  for a power supply voltage. The power supply voltage may be reduced, as shown in graph  209 , and the amplified waveform  213  may range between 10% and 90% of the reduced power supply voltage  211  and be amplified without distortion. By reducing the power supply voltage in this manner, the power consumed by the amplifier is reduced, but the signal quality may remain the same, that is undistorted.  
         [0028]    [0028]FIG. 4 contains graphical representations of example signal environments that may be encountered within a communication receiver. The target signal, which is the signal selected to be received, may be a strong signal requiring little amplification or it may be a weak signal requiring maximum amplification. Even if maximum amplification is applied to the target signal, the target signal may be so weak that the full dynamic range of the amplifier cannot be used, i.e. the target signal may be so weak that it may only be amplified to the point where it occupies part of the dynamic range of the RF input amplifier. The target signal may be such a predominating signal that other signals in the band may be ignored as negligible. The target signal may also be of an intermediate strength when compared to other signals in the band. That is, the target signal may be of a similar magnitude as non target signals within the amplification band of the wide-band RF amplifier.  
         [0029]    A wide-band amplifier may be defined as an amplifier that may amplify a wide band of RF signals, consisting of more than one simultaneous broadcast signal. Many examples of communications equipment have a first stage of amplification that is a wide-band amplifier. As an example, a modem FM radio may receive a 20 MHz bandwidth from approximately 88 MHz to 108 MHz. To amplify signals received in this 20 MHz bandwidth, a wide band amplifier may be utilized. A wide band amplifier, generally will amplify all signals within its bandwidth. Individual broadcast signals of FM stations occupy significantly less than the 20 MHz FM bandwidth, so many individual FM stations may transmit within the 20 MHz FM bandwidth. Individual broadcast signals of FM stations may be selected by multiplying the 20 MHz FM bandwidth with a local oscillator signal. The local oscillator signal will translate all of the RF frequencies within the bandwidth of the wide band and then couple the resultant signal band into a narrow band amplifier. By selecting the local oscillator frequency of different broadcast signals, individual FM stations may be selected from the FM band and translated into the bandwidth of a narrow-band amplifier, e.g. narrow-band amplifier  113 . The narrow band amplifier, which generally has a bandwidth limited so as to amplify only one broadcast signal, will then amplify only the selected broadcast signal.  
         [0030]    [0030]FIG. 4 illustrates a situation similar to the FM band example, where a wide-band frequency range may contain several individual transmission signals within the wide-band range. For purpose of illustration, all the figures will be discussed relative to the illustrative communication receiver arrangement of FIG. 2.  
         [0031]    In FIG. 4, graph  301  illustrates the frequency response of Band-Pass Amplifier  105 . A band-pass amplifier is generally considered to have a band-pass limited by 3 dB points at the higher frequency and lower frequency ends of the band-pass amplifier&#39;s response curve. Band-pass amplifier s  105  response is illustrated by curve  303  in graph  301 , with 3 dB points shown at  323  and  325 . The curve  303  in graph  301  is reproduced in graphs  307 ,  315 , and  317 , in order to illustrate that the individual broadcast signals ( 305 ,  309 ,  311 ,  313 ,  313 A,  319 ,  321  and  321 A) are within the band-pass of the wide-band amplifier&#39;s response curve  303 .  
         [0032]    The graphs  307 ,  315 , and  317  represent three different signal environments. The three different signal environments are used to illustrate how the operation of a wide-band amplifier  105  may be altered to better accommodate the conditions present. The graphs represent several individual broadcast signals, within the bandwidth of the wide-band amplifier  105 . In each graph one desired target signal and one or more undesired, or interference signals, are depicted. The relative strength of the signals depicted in the graphs of FIG. 3 are reflected in each signal&#39;s amplitude on the y axis of the graphs.  
         [0033]    In graph  307 , the signal represented by waveform  305  is the desired target signal. In addition to the target signal there are three other undesired or interference signals  309 . The undesired signals may represent noise, i.e. jamming signals, or other individual transmission signals that are not selected to be received. The desired signal  305  is significantly stronger than the undesired signals  309 . In this case, the amplification of the wide-band amplifier  105  could be increased until the onset of distortion of waveform  305  was detected. Because the desired signal is the strongest in the band of signals being received by the wide-band amplifier, it would be the limiting signal. The limiting signal in this case is the signal with the greatest amplitude. It is also the signal that needs to be amplified as much as possible without distortion. If the signal environment were as portrayed in graph  307 , then the amplification of the wide-band amplifier  105  could be increased until the onset of distortion within the amplifier were detected. When the onset of distortion were detected, it could be correctly assumed that the maximum amplification for the given environment had been applied.  
         [0034]    In graph  315  the target signal  311  is significantly smaller than unwanted signal  313 A. Signal  313 A is the largest signal present within the bandwidth  303  of the wide-band amplifier  105 . In the signal environment illustrated in graph  315 , if the amplification of the wide-band amplifier  105  were increased until the onset of distortion was detected, the target signal  311  would not have the maximum amplification possible. This is because the onset of distortion would be detected in the undesired signal  313 A and the gain of the wide-band amplifier  105  would be limited at that point. Because the target signal  311  is significantly smaller than an undesired signal  313 A, limiting the wide-band amplifier  105  gain when signal distortion is detected will prevent the target signal  311  from being fully amplified. However, the gain of the wide-band amplifier  105  may be increased to the point where the unwanted signal  313 A is not only distorted, but is on the edge of saturation, similar to signal  205  in graph  201 . In that case, the desired signal  311  will receive greater amplification, as compared to a case where the gain had been restricted to the point where the onset of distortion was detected. In the signal environment portrayed in graph  315  the amplifier gain should not be limited to the point where the onset of distortion were detected, the amplification should be limited only at the point where the onset of saturation were detected.  
         [0035]    In graph  317 , a third signal environment is illustrated where the desired signal  319  and the undesired signal  321 A are of the approximately the same amplitude. In the signal environment in graph  317 , the target signal  319  is of the same order of magnitude as the as the unwanted signal  321 A. If the gain of the wide-band amplifier  105  is increased until distortion is detected the maximum gain may not be applied to the target signal. Conversely, if the gain of the wide-band amplifier  105  were to be increased to the point where the onset of saturation were detected, the targeted signal might be distorted and the performance of the receiver degraded. The control algorithms previously applied to the environments depicted in graphs  307  and  315  may result in degraded performance in the signal environment illustrated in graph  317 . If the gain of wide-band amplifier  105  is increased, it may only be increased up to the point where nonlinearity is detected in the target signal  319 , that would have to be monitored at the narrow-band amplifier  113 . In addition to monitoring for distortion of the target signal  319  at the output of the narrow-band amplifier  113 , the wide-band amplifier  105  would have to be monitored for the onset of saturation. The wide-band amplifier  105  must always be kept from saturating or all the signals being amplified by it will be affected, not merely the signal that is causing the saturation.  
         [0036]    Thus, there are three distinct circumstances presented. First, when the desired target signal is the largest signal, the gain of the wide-band amplifier may be increased until distortion is detected. Since the onset of distortion will be detected in the desired signal, the target signal will receive the maximum amplification without distortion.  
         [0037]    Second, when the desired signal is much smaller than the interfering signals, the wide-band amplifier  105  may be adjusted for increasing gain until the onset of saturation is detected in the wide-band amplifier  105 . In the case where the desired signal is significantly smaller than undesired signals, the amplification could be increased until the onset of saturation was detected. At the point where saturation was detected, there could be distortion introduced into a plurality of signals in the band. Since the desired target signal is significantly smaller than the undesired signals, the target signal would not be distorted and would receive maximum amplification.  
         [0038]    Third, when the desired target signal and the undesired signals are of the same order of magnitude, a two step process is required. This is because the target signal is not easily determinable whether the desired signal is the largest signal. If the desired signal is the largest signal, the amplification may be increased until the onset of saturation is detected in the wide-band amplifier  105  or until distortion is detected of the desired signal in the narrow-band amplifier  113  is detected, whichever occurs first. Since it cannot be predicted whether the onset of saturation will be detected or distortion will be detected in the target signal first, both must be monitored and the gain of the wide-band amplifier  105  limited to the point where the first one occurs. Since the desired target and undesired signals are of the same general magnitude the target signal must be monitored, in the narrow-band amplifier  113 , to insure that, when the onset of distortion is detected in the wide-band amplifier, it is not the target signal that is being distorted.  
         [0039]    In order to use the above described signal magnitude information to improve the performance of the receiver system, the onset of amplifier non-linearity and saturation must be detected. To detect amplifier saturation and distortion operating parameters such as current drawn by the amplifier, voltage excursions of amplifier waveforms, and amplifier power may be detected. There are a variety of ways to detect saturation or non-linearity of the target signal, such as by measuring the current used by an amplifier, voltage excursions of amplifier waveforms, and by measuring amplifier power. Various electronic apparatus for producing measurements of amplifier voltage, current, and power are illustrated in FIG. 5.  
         [0040]    To detect current being drawn by an amplifier, a scheme such as the one illustrated at  441  of FIG. 5, may be employed. A low value sensing resistor V R    405  may be inserted in series with the amplifier power supply V CC    409 . The power supply current I PS  consumed by the Amplifier  403  will be proportional to the voltage developed across the low value sensing resistor V R    405 . Because the voltage of the power supply may also be known, the power consumed in the amplifier may be determined. To detect the onset of non-linearity within an amplifier the amplification, or the magnitude of the Input  401  may be changed and the resulting current drawn observed. The ratio of amplification change to the change in current drawn may then be used by some type of Digital Control Unit (DCU), such as a microprocessor, or microcomputer, state machine or the like to calculate the onset of non-linearity and saturation using standard techniques known in the art.  
         [0041]    Another scheme to detect current being drawn by an amplifier is illustrated at  443  in FIG. 5. A current measuring device  417 , such as a hall effect device, may be placed so that all the current entering the amplifier  417  will be directed by the sensor. The power supply current I PS  consumed by the amplifier  403  may be detected by a current sensing device  417 . Because the voltage of the power supply is known, the power consumed in the amplifier may also be ascertained. To detect the onset of nonlinearity, the amplification of the amplifier or the magnitude of the input  411  may be changed and the resulting current drawn by the amplifier observed. The ratio of amplification change to the change in current drawn may then be used by a digital control unit (DCU), such as a microprocessor, or microcomputer, state machine or the like, to calculate the onset of nonlinearity and saturation using standard techniques known in the art.  
         [0042]    To detect output voltage excursions of an amplifier, a scheme as illustrated in at  445  in FIG. 5, may be used. The input  421 , or the gain of the amplifier  419 , may be varied. By observing the change in the amplitude of the output waveform with an amplitude detection circuit  423 , the onset of saturation or amplitude non linearity may be calculated.  
         [0043]    Another scheme to detect the output voltage excursions of the output of an amplifier is illustrated at  447  in FIG. 5. The input  425 , or the gain of the amplifier  427 , may be varied and the change in the amplitude of the output waveform may be observed. By detecting a positive peak, V +   PEAK , using diode  429 , and capacitor  433 , and a negative peak, V −   PEAK , using diode  435 , and capacitor  439 , signal amplitude and hence the onset of saturation or signal non linearity may be detected.  
         [0044]    Another method of detecting the onset of distortion and saturation in an amplifier in an amplifier employs a variable level power supply. A variable level power supply might be in the form of the DC-DC converter. FIG. 6 illustrates a DC-DC converter  501 , such as might be used in detection of saturation and distortion of an amplifier. The DC-DC converter  501  may be connected to a power supply V CC    503 . A Control Signal  507  may then control the DC output V DC    505 . The DC output V DC    505  would then be used as a power supply for the amplifier. The DC level could be controlled by a Digital Control Unit (“DCU‘) that would measure amplifier parameters such as out put voltage swing of the amplifier or the current drawn by the amplifier. The onset of distortion or saturation could then be detected by the DCU.  
         [0045]    As DC to DC converters increase in efficiency, they may be employed in changing the amplifier supply voltage not only to check circuit parameters and detect the onset of conditions such as distortion and saturation, but as a method of more efficiently operating the amplifier. By limiting the supply voltage to the minimum level that is necessary to achieve the proper amplifier performance, power may be saved. For example in FIG. 2, if the maximum amplification of a signal produces a signal  213  as illustrated in graph  201 , the amplified signal will be using only a relatively small portion of the amplifier&#39;s range. If the power supply voltage is reduced, for example using a DC-DC converter, then the situation in graph  209 , where the signal  213  uses most of the linear operating region of the amplifier, may be obtained. Since the signal  213  is being amplified in linear operating regions of the amplifier, the reduction of the power supply voltage does not adversely affect the quality of the signal  213 . However, in graph  209 , where the power supply voltage has been reduced, the power consumed by the amplifier is also reduced.  
         [0046]    [0046]FIG. 7 contains a graph  601 , illustrating the relationship between the ratio of narrow-band amplifier  113  output and the wide-band amplifier  105  output versus the amount of desired target signal present within a wide-band signal. The vertical axis of the graph represents the portion of the wide-band signal that is represented by the desired target signal. For example, at point  605 , the desired signal makes up 100% of the wide-band amplifier signal. At point  609 , the desired signal makes up 50% of the wide-band amplifier signal. At point  613 , the desired signal makes up 0% of the wide-band amplifier signal, i.e. it is not present. This ratio of desired signal to spurious signal may be used in order to control characteristics of a wide-band amplifier in a communications system to optimize performance.  
         [0047]    [0047]FIG. 8 is an illustration encompassing several preferred embodiments of the invention. Signals are received by the antenna  701 , and then passed to a wide-band amplifier  709 . The current sensor  707  measures the current that is being supplied to the wide-band amplifier  709  from a DC to DC converter  713 . The measurement  715  is then passed to the digital control unit (“DCU‘)  738 . The band of frequencies from the wide-band amplifier  709  is then provided to a mixer  717 , where it is combined with a frequency  718  from a local oscillator  718 , and then provided to a narrow-band filter  719 . The frequency provided to the mixer  717  is controlled by the DCU  738  and adjusted so that the narrow-band Filter  719  passes only the frequency containing the broadcast channel desired. The output of the narrow-band Filter  719  is passed to a narrow-band amplifier  729 . The output of the narrow-band filter  719  is also passed to a peak to peak measurement unit  723 . The peak to peak measurement unit  723  is passed to the DCU  738  via a signal  721 .  
         [0048]    The DCU  738 , may then accept the measurement from the peak to peak measurement unit  723  and compare it to the measurement  715  from the current sensor  707 , in order to establish a signal ratio of desired signal to total signal present in the wide-band amplifier  709 . If the signal ratio is greater than a certain level, illustrated as point  607  in FIG. 7, then the desired signal is predominant. Where the desired signal is predominant, the DCU  738  may increase the gain of the wide-band amplifier  709 , until the onset of distortion in the wide-band amplifier  709 , is detected. If the narrow-band amplifier  729  cannot handle any more signal input without distortion, then nothing is gained by increasing the gain of the wide-band amplifier  709 . Thus, the signals may be as illustrated by waveform  213 , in Graph  201  of FIG. 2. The signal amplitude may not typically be increased without overloading the narrow-band amplifier  729 . If the amplification of the incoming signal cannot be increased, the wide-band amplifier power supply may be decreased without affecting the amplification of the desired signal. The voltage of the DC-DC Converter  705  may be decreased without affecting the amplification of the desired signal. The DCU  738  may use control line  713 , from the DCU  738 , to command the DC-DC Converter  705  to lower the wide-band amplifier  709  power supply voltage until the measurement at the Current Sensor  707  detects the beginning of the onset of non-linearity. Where the onset of nonlinearity is detected, the wide-band amplifier  709  power supply voltage may not be lowered without sacrificing the quality of the desired signal.  
         [0049]    If the signal ratio is past a certain level as illustrated in point  611  in FIG. 7, then the undesired signals are predominant. Where the undesired signals are predominant, the signals may be as illustrated in graph  315  of FIG. 4. The DCU  738  may use control line  711  from the DCU  738  to increase the gain of the wide-band amplifier  709 . When the measurement at the Current Sensor  707  detects the beginning of the onset of non-linearity, it is an unwanted signal, e.g.  313 A, that is being distorted. Thus, the gain of the wide-band amplifier  709  may be increased until the onset of saturation is detected. At the point where the wide-band amplifier  709  begins to saturate, the gain of the wide-band amplifier  709  may not be increased without adversely affecting all signals being amplified. However, where an unwanted signal is being distorted, is of little consequence and the wide-band amplifiers  709  amplification of the desired signal improves the performance of the system.  
         [0050]    If the signal ratio exceeds a certain level as illustrated in point  611  in FIG. 7, but is less than a certain level illustrated as point  607 , then the undesired signals are of the same order of magnitude as the desired signal. Thus, the signals may be as illustrated in graph  317  of FIG. 4. Since the desired signal and the undesired signal are similar in value, both the onset of saturation in the wide-band amplifier  711  and the onset of distortion in the narrow-band amplifier  729  will need to be monitored. The gain of the wide-band amplifier  711  may be increased until detection of either the onset of saturation in the wide-band amplifier  711  or the onset of distortion in the narrow-band amplifier  729 . If the signal passed to the narrow-band amplifier  729  is at a maximum level, then power supply  705  of the wide-band amplifier  711  may be decreased until detection of either the onset of saturation in the wide-band amplifier  711  or the onset of distortion in the narrow-band amplifier  729 . Where the power supply of the wide-band amplifier  709  is reduced until the onset of distortion is detected in the wide-band amplifier  709 , the desired signal may be monitored for distortion by monitoring the signal into the narrow band amplifier via the peak to peak signal monitor  723 , or by monitoring the current signal  727  of the current sensor  725 . The current signal  727  represents the current being supplied to the narrow-band amplifier  729  and may be used to detect the onset of signal nonlinearity.  
         [0051]    While various embodiments of the application have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of this invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.