HK1173012B - Signal quality estimation and control system - Google Patents

Abstract

A signal quality estimation and control system for controlling a signal having noise. The system may include a signal strength determination system having an input configured to receive the signal and an output configured to output information indicative of the strength of the signal, a noise strength determination system having an input configured to receive the signal and an output configured to output information indicative of the strength of the noise in the signal, and a signal quality evaluation system. The signal quality evaluation system may have an input configured to receive the output of the signal strength determination system, an input configured to receive the output from the noise strength determination system, and an output configured to output information indicative of the quality of the signal based on the output from the signal strength determination system and the output from the noise strength determination system. A signal control system may be include that has an input configured to receive the output from the signal quality evaluation system and to control a switching function relating to the signal based on the output from the signal quality evaluation system.

Description

Signal quality estimation and control system

The present application is a divisional application of chinese patent application having an application number of 200680017253.3, entitled "signal quality estimation and control system" by attritor corporation.

Cross Reference to Related Applications

This application is based on and claims priority from U.S. provisional application No.60/667,969 entitled "FMSignal Quality assessment for BTSC Audio Decoders," filed 4/2005, attorney docket No. 56233-234, which is incorporated herein by reference in its entirety.

Technical Field

The present application relates to signal processing and control systems, and more particularly to the estimation of signal strength and/or noise in a modulated signal, and to the control of such a signal.

Background

Both noise in the modulated signal and the reduction in the strength of the signal can cause problems. However, it may be difficult to accurately evaluate the level of this noise. And it is also difficult to effectively address any detected problems.

Noise and attenuation in the Secondary Audio Program (SAP) channel of a BTSC television signal is an example. As is well known, the SAP channel is frequency modulated on a 4.5MHz audio carrier, i.e., itself frequency modulated as part of the overall television signal. The same audio carrier is also often used to carry information for other channels, including the sum of the left and right stereo signals (L + R), the difference between the left and right stereo signals (L-R), and professional information (PROF).

The SAP channel is typically more susceptible to noise than the L + R and L-R (which are typically decoded in a television set to form left and right stereo signals). This is due to the SAP channel being farther from the center of the 4.5MHz carrier than the L-R channel or the L + R channel (which are also used for monaural signals). It is well known that signals that are far from the center of a frequency modulated carrier are generally more susceptible to noise interference than signals that are closer to the center of the carrier.

In some cases, the SAP signal may not be present or it may have insufficient signal strength to meet acceptable listening quality. In other cases, the noise imposed on the SAP signal may have an amplitude that degrades the SAP signal to an unacceptable level.

Similar and/or other problems with amplitude and/or noise may arise in other types of modulated signals, such as professional channel FM carrier signals (PROF), european dual FM audio carrier signals (a2 and Zweiton), japanese 4.5MHz audio carrier signals (EIAJ), japanese FM differential carrier signals (EIAJ), analog mono FM carrier signals (NICAM), FM stereo signals, satellite FM audio signals, and AM signals.

Disclosure of Invention

An SAP signal quality estimation and control system for controlling an SAP signal having noise may include a signal quality estimation system having an input configured to receive the SAP signal and an output configured to output information indicative of a quality of the received signal. The SAP signal quality estimation and control system may also include a signal control system having an input configured to receive the signal quality estimation system output and for providing a switching function related to the SAP signal.

The signal control system may be configured to control switching between SAP and stereo channels, between SAP and monaural channels, between allowing and disallowing user selection of SAP channels, and/or between playing SAP and muting SAP channels.

The SAP signal quality estimation system may be implemented with a digital signal processing system.

The signal quality estimation and control system may include: a signal strength determination system having an input configured to receive a signal and an output configured to output information indicative of the strength of the signal; a noise strength determination system having an input configured to receive a signal and an output configured to output information indicative of the strength of noise in the signal; and a signal quality evaluation system. The signal quality evaluation system may have an input configured to receive an output of the signal strength determination system, an input configured to receive an output of the noise strength determination system, and an output configured to output information indicative of signal quality based on the output of the signal strength determination system and the output of the noise strength determination system.

The output of the signal quality evaluation system may be configured to output information indicating whether the signal quality is acceptable or not. This may be based on a comparison between the output information of the signal strength determination system and a predetermined signal strength threshold. This may also be based on a comparison between the output information of the noise strength determination system and a predetermined noise strength maximum. This may also be based on a comparison between the output information of the signal strength determination system and the output information of the noise strength determination system. The comparison may be between a ratio of the output information of the signal strength determination system to the output information of the noise strength determination system and a predetermined signal-to-noise ratio threshold.

The signal strength determination system may include an envelope extraction system having an input configured to receive the FM signal and an output configured to output information indicative of an amplitude of an envelope of the FM signal. The signal strength determination system may also have an averaging system having an input configured to receive the output of the envelope extraction system and an output configured to output information indicative of an average of the output of the envelope extraction system.

The signal strength determination system may include a signal strength indicator having an input configured to receive information based on an output of the averaging system and an indicator configured to indicate signal strength to a user.

The noise strength determination system may include an envelope extraction system having an input configured to receive the FM signal and an output configured to output information indicative of an amplitude of an envelope of the FM signal. The noise strength determination system may also have a first averaging system having an input configured to receive the output of the envelope extraction system and an output configured to output information indicative of an average of the output of the envelope extraction system. The noise strength determination system may also have a subtraction system having an input configured to receive the output of the envelope extraction system, an input configured to receive the output of the averaging system, and an output configured to output information indicative of a difference between the output of the envelope extraction system and the output of the first averaging system. The noise strength determination system may also have a second averaging system having an input configured to receive information based on the output of the subtraction system and an output configured to output information representing an average of the information based on the output of the subtraction system.

The first and/or second averaging systems may each comprise an integrator.

The noise strength determination system may include a squaring system having an input configured to receive the output of the subtracting system and an output configured to transmit information representing an approximation of the square of the output of the subtracting system to the input of the second averaging system.

The noise strength determination system may include a noise strength indicator having an input configured to receive information based on an output of the second averaging system and an indicator configured to indicate a strength of the noise to a user.

A noise strength determination system for determining noise strength in an AM signal having an envelope may include an extraction system having an input configured to receive the AM signal and an output configured to output information indicative of an amplitude of FM modulation on the AM signal.

The above and other features, steps, features, objects, benefits and advantages will become more apparent from a reading of the following detailed description of exemplary embodiments, the accompanying drawings and the claims.

Drawings

FIG. 1 is a block diagram of a signal quality estimation and control system;

FIG. 2 is a block diagram of the signal and noise strength determination system shown in FIG. 1 configured for use with FM signals;

FIG. 3 is a block diagram of various signal quality estimation and control systems processing an SAP FM carrier signal;

FIG. 4 is a block diagram of various signal quality estimation and control systems processing signals other than SAP FM carrier signals; and

fig. 5 is a block diagram of a signal and noise strength indicator system.

Detailed Description

Fig. 1 is a block diagram of a signal quality estimation and control system.

As shown in fig. 1, the signal quality estimation and control system may include a signal quality estimation system 101 and a signal control system 103.

The signal quality estimation system 101 may be configured to receive the modulated signal 105 and output information indicative of the quality of the modulated signal 105. The modulated signal 105 may be any type of modulated signal including derivatives of modulated signals such as modulated signals that have been shifted in frequency by heterodyne or other techniques. The modulated signal 105 may include one or more undesired noise components. Specific examples of the modulated signal 105 are discussed below in conjunction with fig. 2-4.

The signal quality estimation system 101 may have a signal strength determination system 109, to which signal strength determination system 109 the modulated signal 105 may be transmitted. The signal strength determination system 109 may output information indicative of the strength of the modulated signal 105.

The signal quality estimation system 101 may have a noise strength determination system 111, to which noise strength determination system 111 the modulated signal 105 may be transmitted. Noise strength determination system 111 may output information indicative of the strength of noise that is part of modulated signal 105.

The signal quality estimation system 101 may have a signal quality evaluation system 119. The signal quality evaluation system 119 may be configured to receive the output of the signal strength determination system 109 and the output of the noise strength determination system 111. The signal quality evaluation system 119 may output information to the signal control system 103 indicative of the quality of the modulated signal 105 based on the output of the signal strength determination system 109 and/or the output of the noise strength determination system 111.

The signal quality evaluation system 119 may perform any type of algorithm, calculation, or processing to provide the output. In one embodiment, the signal quality evaluation system 119 may compare the output of the signal strength determination system 109 to a predetermined signal strength threshold. If the output of the signal strength determination system 109 is greater than the predetermined signal strength threshold, the signal quality evaluation system 119 may indicate to the signal control system 103 that the modulated signal 105 is acceptable. Otherwise, the signal quality evaluation system 119 may indicate that the modulated signal 105 is unacceptable.

The signal quality evaluation system 119 may also compare the output of the noise strength determination system 111 with a predetermined noise strength maximum. If the output of the noise strength determination system 111 is not greater than the predetermined noise strength maximum, the signal quality evaluation system 119 may indicate to the signal control system 103 that the modulated signal 105 is acceptable. Otherwise, the signal quality evaluation system 119 may indicate that the modulated signal 105 is unacceptable.

The signal quality evaluation system 119 may also compare the output of the signal strength determination system 109 with the output of the noise strength determination system 111 and inform whether the modulated signal 105 is acceptable based on the comparison.

Any type of comparison may be made. In one embodiment, the comparison may be between the ratio of the output of the signal strength determination system 109 to the output of the noise strength determination system 111 and a predetermined signal-to-noise ratio threshold. If the measured ratio is greater than a predetermined threshold, the signal quality evaluation system 119 may indicate to the signal control system 103 that the modulated signal 105 is acceptable. Otherwise, the signal quality evaluation system 119 may indicate that the modulated signal 105 is unacceptable.

The signal quality evaluation system 119 may make the acceptable/unacceptable determination based on other criteria and combinations of criteria. For example, the signal quality evaluation system 119 may signal that the modulated signal 105 is acceptable only if the output of the signal strength determination system 109 is greater than a predetermined signal strength threshold and the output of the noise strength determination system 111 is not greater than a predetermined noise strength maximum. In another embodiment, the signal quality evaluation system 119 may signal that the modulated signal 105 is unacceptable only if the output of the signal strength determination system 109 is greater than a predetermined signal strength threshold and the ratio of the output of the signal strength determination system 109 to the output of the noise strength determination system 111 is greater than a predetermined signal-to-noise ratio threshold.

The signal control system 103 may be configured to receive an output from the signal quality estimation system 101 and provide a switching function related to the modulated signal 105. Any type of switching function may be provided in relation to the modulated signal 105. Further examples are discussed below in conjunction with the discussion of fig. 3.

Fig. 2 is a block diagram of the signal and noise strength determination system shown in fig. 1 configured for FM signals. Although FIG. 2 will now be discussed in conjunction with FIG. 1, the system shown in FIG. 2 may be used with other systems than the system shown in FIG. 1. Similarly, the system shown in FIG. 1 may work with other systems than the system shown in FIG. 2.

The signal strength determination system 109 shown in fig. 1 may include an envelope extraction system 201 and a mean computation system 203.

The noise strength determination system 111 shown in fig. 1 may include an envelope extraction system 201, a mean computation system 203, a subtraction system 205, a squaring system 207, and a mean computation system 209.

The envelope extraction system 201 may be configured to produce an output representing the magnitude of a synthesized (parsed) representation of the FM signal 211, such as the envelope of the FM signal 211. Signals that extract envelope information from FM signals are known. Any such system may be used.

The averaging system 203 may be configured to produce an output representative of the amplitude of the envelope received from the envelope extraction system 201 over a period of time. Systems for time averaging signal values are also known, and any such system may be used. Such systems may include, for example, a low pass filter and/or an integrator. The output of the averaging system 203 may represent the average signal strength of the FM signal 211 as reflected by the average signal strength output 213.

The subtraction system 205 can be configured to subtract the instantaneous value of the envelope from the envelope extraction system 201 from the output of the mean computation system 203. The output of the subtraction system 205 may thus represent the instantaneous deviation of the envelope of the FM signal 211 from the mean of the envelope of the FM signal 211.

In an idealized system, the envelope of the FM signal 211 will not change over time. However, in a real system, noise may be introduced, which will cause amplitude modulation of the FM signal 211. Thus, the output of the subtraction system 205 may represent noise on the FM signal 211.

The squaring system 207 may be configured to receive the output from the subtraction system 205 and output information representing an approximation of the square of the output of the subtraction system 205. Squaring the output from the subtraction system 205 can eliminate errors that would otherwise be introduced if both positive and negative changes in the output of the subtraction system 205 were to be evaluated. Squaring the output also provides a more linear representation of the variation in noise level in the FM signal 211. The squaring system 207 may be replaced by a system that calculates the absolute value of the output of the subtraction system 205.

The averaging system 209 may be configured to average the output of the squaring system 207 over a period of time. The system may be any type of averaging system, such as one of the types of averaging systems discussed above in connection with averaging system 203.

Thus, the output of the averaging system 209 may represent the average noise strength, as reflected by the average noise strength output 215.

Fig. 3 is a block diagram of various signal quality estimation and control systems processing an SAP FM carrier signal. This figure shows some of the many types of switching functions that can be provided by the signal control system 103 of fig. 1.

As can be seen by a close examination of fig. 3, the signal quality estimation and control system 301 may receive an SAP FM carrier signal 303, which SAP FM carrier signal 303 may be part of a BTSC formatted signal. Although the SAP FM carrier signal is shown in fig. 3 as a processed signal, any other type of modulated signal may be processed. Examples of such other types of modulated signals are discussed below in conjunction with fig. 4.

Returning to fig. 3, the SAP FM carrier signal 303 may be processed by a signal quality estimation system 301, which signal quality estimation system 301 may be the same as the signal quality estimation system 101 in fig. 1 and 2.

Blocks 303a-303e illustrate a number of different types of signal control systems that may be used. Each of which may function as the signal control system 103 shown in fig. 1. An actual system may have only one of these types of control systems, or in some cases, another type of control system, or in other cases, a plurality of these types of control systems.

The SAP/stereo control system 303a may be configured to switch the receiver in which the system shown in fig. 3 is installed from outputting SAP channels to outputting stereo channels. The SAP/stereo control system 303a may be configured to cause this switching to occur when the output of the signal quality estimation system 301 indicates that the SAP FM carrier signal 303 has unacceptable quality.

By using this configuration, the receiver can automatically switch from the SAP channel to the normal stereo channel when the noise level and/or signal strength in the SAP FM carrier signal 303 reaches an unacceptable level. Since stereo channels are typically less sensitive to noise than SAP channels, this may automatically provide a comparable high quality channel to the listener. The SAP/stereo control system 303a may be configured such that the receiver is caused to revert to the originally selected SAP channel when the output of the signal quality estimation system 301 indicates that the SAP FM carrier signal 303 returns to an acceptable quality.

The SAP/mono control system 303b may operate in a similar manner except that the SAP/mono control system 303b may cause the receiver to switch between the SAP channel and the monaural channel. The monaural channel is less susceptible to noise than the stereo channel.

The SAP/stereo/mono control system 303c may operate in a similar manner except that the SAP/stereo/mono control system 303c may be configured to switch between three modes, namely, an SAP channel, a stereo channel, and a monaural channel. In this embodiment, the signal quality estimation system 301 may be configured to output three acceptable levels, the highest level deemed by the SAP/stereo/mono control system 303c to allow the SAP channel to continue playing, the middle level deemed by the SAP/stereo/mono control system 303c to require the receiver to switch from the SAP channel to the stereo channel, and the lowest level deemed by the SAP/stereo/mono control system 303c to require the receiver to switch from the stereo channel to the monaural channel. When the signal improves, the SAP/stereo/mono control system 303c may be configured to cause the switch to revert to the original setting.

Many receivers include a user operated control that allows the user to switch between a normal stereo channel (or monaural channel) and an SAP channel. The SAP selection disable system 303d may be configured to disable the user operated control when the output of the signal quality estimation system 301 indicates that the quality of the SAP FM carrier signal 303 is unacceptable. This may be accomplished by removing the option from the user's line of sight or preventing the user from activating the option. The disable control may be removed once the output of the signal quality estimation system 301 indicates that the quality of the SAP FM carrier signal 303 is again acceptable.

The SAP muting control system 303e may be configured to mute the sound output by the receiver when the output of the signal quality estimation system 301 indicates that the quality of the SAP FM carrier signal 303 is not acceptable, and may remove the mute when an acceptable indication is again received.

Fig. 4 is a block diagram of various signal quality estimation and control systems processing other signals in addition to the SAP FM carrier signal. As shown in fig. 4, the signal quality estimation and control system may include a signal quality estimation system 401, and the signal quality estimation system 401 may be of any type, such as the signal quality estimation system 101 shown in fig. 1 and 2.

The signal quality estimation system 401 may be configured to receive any type of modulated signal, such as one of the modulated signals 403 a-i.

The signal control system 403 may receive an output from the signal quality estimation system 401 and control a switching function related to the modulated signal. The signal control system 403 may be of any of the types 303a-303e discussed above in connection with fig. 3, with any of the types 303a-303e discussed in connection with fig. 3 being modified to control the switching function appropriate for the particular modulated signal being processed.

One example of a modulated signal that may be processed is a 4.5MHz FM audio carrier signal 403 a. As is well known, this is an audio carrier channel that is FM modulated on a standard NTSC signal in accordance with the BTSC format. It includes the SAP channel described above as well as other channels. In this embodiment, the signal control system 403 may be configured to switch between stereo and monaural or to switch between monaural and mute.

Another example of a modulated signal that may be processed is a professional channel FM carrier signal 403 b. As is well known, the professional channel FM carrier is another channel that includes the 4.5MHz FM audio carrier in the NTSC signal. In this embodiment, the signal control system 403 may be configured to switch between professional channel and mute.

Another example of a modulated signal that may be processed is the european dual FM audio carrier signal 403 c. As is well known, this is the audio channel used in european television transmissions as part of the a2 or Zweiton format. In this embodiment, the signal control system 403 may be configured to switch between stereo and monaural, or between bilingual channel B and bilingual channel a, or between either of the channels and silence.

Another example of a modulated signal that may be processed is the japanese 4.5MHz FM audio carrier signal 403 d. It is well known that this is an audio carrier widely used in japan as part of the EIAJ format. In this embodiment, the signal control system 403 may be configured to switch between stereo and monaural or between monaural and mute.

Another example of a modulated signal that may be processed is the japanese FM differential carrier signal 403 e. As is well known, this differential carrier forms one of the channels of the japanese 4.5MHz FM carrier signal in the EIAJ format.

Another example of a modulated signal that may be processed is an analog mono FM carrier signal 403 f. As is well known, this is an analog mono channel under the NICAM format. In this embodiment, the signal control system 403 may be configured to switch between monaural channels and mute.

Another example of a modulated signal that may be processed is an FM stereo broadcast signal 403 g. As is well known, this is a signal widely used in FM broadcasting. In this embodiment, the signal control system 403 may be configured to switch between stereo and monaural channels.

Another example of a modulated signal that may be processed is a satellite FM audio transmission signal 403 h. As is well known, this is a widely used signal in the transmission of FM audio by satellite. In this embodiment, the signal control system 403 may be configured to switch between monaural channels and mute.

Another example of a modulated signal that may be processed is an AM modulated signal 403 i. This signal may be used, for example, with AM broadcasting or as an analog mono carrier in NICAM-L systems. However, in this embodiment, the signal quality estimation system 401 may use a different extraction system than the envelope extraction system 201 shown in fig. 2. In particular, the signal quality estimation system 401 may use an extraction system configured to receive the AM signal 403i and output information representative of the amplitude of the FM modulation on the AM signal. Ideally, the AM signal will not exhibit any deviation in its frequency. However, when noise is added to the signal, the noise can be detected by checking the deviation of the frequency of the AM signal, that is, by checking the amplitude of FM on the AM signal. All other components shown in fig. 1 and 2 may be the same as described above except for this change. In this embodiment, the signal control system 403 may be configured to switch between monaural channels and mute.

Fig. 5 is a block diagram of a signal and noise strength indicator system. The signal and noise strength indicator system may include a signal strength determination system 501, the signal strength determination system 501 being coupled to a signal strength indicator 503. Similarly, the signal and noise strength indicator system may include a noise strength determination system 505, the noise strength determination system 505 coupled to a noise strength indicator 507.

The signal strength determination system 501 may be the same as the signal strength determination system 109 or may be of any other type. Similarly, noise strength determination system 505 may be the same as noise strength determination system 111, or may be of any other type.

The signal strength indicator 503 and the noise strength indicator 507 may be any type of indicator configured to communicate information regarding signal strength or noise strength, respectively, to a user. The signal strength indicator 503 and the noise strength indicator 507 may each include a digital display, one or more LED lights, an analog meter, other types of indicating devices, and/or any combination of these devices. While the illustrated system in fig. 5 is illustrated with both a signal strength indicator 503 and a noise strength indicator 507, alternative embodiments may include only one of these indicators, such as only the signal strength indicator 503 (where the noise strength determination system 505 and the noise strength indicator 507 may not be needed) or only the noise strength indicator 507 (where the signal strength determination system 501 and the signal strength indicator 503 may not be needed).

The composition and operation of various subsystems not described in detail above are well known in the art. One or more of these subsystems may be implemented with analog circuitry and/or digital circuitry. For example, one or more of the components of the signal strength determination system 109, the noise strength determination system 111, and the signal quality evaluation system 119 may be implemented using mathematical equations that are processed in the digital domain by a digital signal processing system, all in accordance with well-known techniques. In fact, in this and other embodiments, each of the modulated input signals described may constitute periodic samples of a reference modulated signal. These samples may be taken at any rate, such as 384KHz or 288 KHz.

The averaging system may be configured in accordance with known techniques so that it is more focused on new measurements than on old measurements.

Although the particular signals described so far are FM or AM signals, these signals may include both modulation types. The signal quality estimation and control systems that have been described can efficiently process these mixed modulation type signals, especially when only one type of modulation is dominant in the signal. For example, when processing a mixed modulation type signal and one type of modulation predominates, the signal quality evaluation system 119 may be configured to find no unacceptable signal until the measurements of the noise strength determination system 111 yield values greater than those resulting from the non-predominate modulation type.

The components, steps, features, objects, benefits and advantages that have been discussed are merely illustrative. Neither they nor the discussion about them are intended to limit the scope of protection. Numerous other embodiments are also contemplated, including embodiments having fewer, more, and/or different components, steps, features, objects, benefits, and advantages. The components and steps may also be arranged and customized in different ways.

In short, the scope of protection is only limited by the appended claims. The scope is intended to be accorded the breadth consistent with the language used in the claims and to include all structural and functional equivalents. The above discussion or exemplary descriptions is not intended to dedicate any features, steps, features, objects, benefits, advantages, or equivalents to the public regardless of whether they are recited in the claims.

The term "means for. Similarly, the word "step for. The absence of such phrases means that the claims do not define any corresponding structure, material, or acts.

Claims (9)

1. A signal quality estimation and control system for controlling a signal having noise, comprising:

a signal strength determination system having an input configured to receive the signal and an output configured to output a signal strength signal indicative of the strength of the signal; wherein the signal strength determination system comprises: (i) an envelope extraction system having an input configured to receive an FM signal, and an output configured to output an FM magnitude signal representative of an envelope magnitude of the FM signal; and (ii) a mean computation system having an input configured to receive the FM magnitude signal output by the envelope extraction system, and an output configured to output a mean FM signal representing a mean of the FM magnitude signal output by the envelope extraction system;

a noise strength determination system having an input configured to receive the signal and an output configured to output a noise strength signal indicative of the strength of noise in the signal; wherein the noise strength determination system comprises: a subtraction system having a first input configured to receive the FM magnitude signal, a second input configured to receive the mean FM signal, and an output configured to output a difference signal representing a difference between the FM magnitude signal and the mean FM signal; wherein the noise strength determination system is configured to receive the difference signal from an output of the subtraction system;

a signal quality evaluation system having a first input configured to receive a signal strength signal from an output of the signal strength determination system, a second input configured to receive a noise strength signal from the noise strength determination system, and an output configured to output a quality signal indicative of a quality of the signal based on at least one of the signal strength signal and the noise strength signal; and

a signal control system having an input configured to receive the quality signal and to control a switching function related to the signal based on the quality signal;

wherein an input of the signal strength determination system and an input of the noise strength determination system are configured to receive an SAP signal; and

wherein the signal control system is configured to control a switching function related to the SAP signal.

2. A signal quality estimation and control system according to claim 1, wherein the output of the signal quality evaluation system is configured to output information indicating whether the signal quality is acceptable.

3. A signal quality estimation and control system according to claim 2 wherein the output of the signal quality evaluation system is based on a comparison between the signal strength signal and a predetermined signal strength threshold.

4. A signal quality estimation and control system according to claim 2 wherein the output of the signal quality evaluation system is based on a comparison between the noise strength signal and a predetermined noise strength maximum.

5. The signal quality estimation and control system of claim 2 wherein the output of the signal quality evaluation system is based on a comparison between the signal strength signal and the output noise strength signal.

6. The signal quality estimation and control system of claim 5 wherein the comparison is between a ratio of the signal strength signal to the noise strength signal and a predetermined signal-to-noise ratio threshold.

7. The signal quality estimation and control system of claim 6 wherein the quality signal is further based on a comparison between the signal strength signal and a predetermined signal strength.

8. The signal quality estimation and control system of claim 1 wherein the averaging system comprises an integrator.

9. The signal quality estimation and control system of claim 1 wherein the signal strength determination system and the noise strength determination system are each implemented by a digital signal processing system.