Patent Application
20090175468
1. Field of the Invention
The invention relates to audio processing, and in particular to methods for preventing click-and-pop caused by gain changes and an electronic device using the same.
2. Description of the Related Art
Many electrical devices, such as telephone devices, mobile phones or signal transceivers, including digital cordless telephone base stations and digital telephone answering machines, receive an input signal wherein the input signal gain or strength can vary widely and rapidly. In such cases, in the presence of relatively large fluctuations in input signal levels, it is often desirable to maintain the gain of the input signal within an acceptable range. This is particularly desirable if the input signal is provided to another device requiring the input signal level to be within a certain range. Automatic gain controllers (AGCs) are commonly included in such electrical devices to maintain the gain of the input signal at a relatively constant value or within a desired dynamic range by adjusting the amplification of the input signal in inverse proportion to the input signal strength.
Embodiments of an electronic device are provided. An amplifier thereof amplifies an input signal and generates an amplified signal. An analog-to-digital converter (ADC) thereof converts the amplified signal to a digital signal. An automatic gain controller (AGC) thereof updates a gain of the amplifier according to a strength of the amplified signal or amplified digital signal. A smoothing unit thereof updates a gain of the digital signal from the ADC before and/or after the AGC updates the gain of the amplifier, such that click-and-pop caused when the AGC updates the gain of the amplifier is eliminated.
The invention provides an embodiment of a method for preventing click-and-pop caused by gain changes, in which an input signal is amplified by an amplifier, and the amplified input signal is converted to a digital signal. A gain of the amplifier is updated according to a strength of the amplified signal or amplified digital signal, and a gain of the digital signal is updated before and/or after updating the gain of the amplifier.
The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:
The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.
The electronic device 100A comprises a programmable gain amplifier (PGA) 10, an analog-to-digital converter (ADC) 12, an automatic gain controller (AGC) 14 and a smoothing unit 16. The PGA 10 has an adjustable gain which is controlled by a signal S3, and the amplifier 10 amplifies or attenuates input signals Sin and generates corresponding amplified signals S1. Namely, the PGA 10 receives the input signals Sin, amplifies the received input signals Sin according to the control of the AGC 14, and then outputs the amplified signals S1 to the ADC 12. The ADC 12 converts the amplified signals S1 from the PGA 10 to digital signals S2.
The AGC 14 maintains the gain of the input signal Sin at a relatively constant value or within a desired dynamic range by adjusting the amplification of the input signal Sin in inverse proportion to the input signal strength. For example, the AGC 14 examines and analyzes strength of the amplified signal S1 (analog signals) and outputs a signal S3 to adjust the gain of the PGA 10, thereby avoiding from a loss of information caused by distortion (including clipping) or low signal to noise ratio (SNR). The AGC 14 selectively increases the gain, decreases the gain or does not change the gain of the PGA 10 according to the analysis of the signal S1. The AGC 14 is preferably a digital signal processor (DSP) programmed to perform the device functions. The AGC 14 may also be comprised of a programmed general purpose CPU or dedicated digital or analog circuit.
However, click-and-pop may occur when the AGC 14 is turned on to adjust the PGA 10. Because the gain step is discontinuous, click-and-pop may occur across the gain change boundary. For example, as shown in
In order to overcome such a problem, the smoothing unit 16 smoothes the gain step when the gain of the PGA 10 changes according to control of the AGC 14 and then outputs the smoothed signal serving as an output signal Sout. In this case, the smoothing unit 16 is coupled between the ADC 12 and the AGC 14, and generates a smooth gain to adjust the (digital) signal S2 from the ADC 12 according to a signal S4 from the AGC 14, thereby smoothing the gain step of the PGA 10 such that click-and-pop can be eliminated. For example, the smoothing unit 16 can be a pre-smoothing unit to smooth the gain step of the PGA 10 before the AGC 14 updates gain of the PGA 10, a post-smoothing unit to smooth the gain step of the PGA 10 when the AGC 14 updates gain of the PGA 10 or a combination thereof. An application circuit (not shown), such as a digital telephone answering machine, preferably receives and processes the output signal Sout to perform a desired function. Detailed description of the smoothing unit 16 is provided later, and only briefly described herein.
When the AGC 14 generates the signals S3 to update the gain of the PGA 10 by +N dB according to signal strength of the signals S1, the AGC 14 also generates the signals S4 to enable the post-smoothing unit 16_1 to update (decrease) the gain of the signals S2 from ADC 12 during a time period after the gain of the PGA 10 changes, such that gain change of the output signals Sout can be smoothed.
At time t6, the post-smoothing unit 16_1 then generates the smooth gain SMG with −0.6 dB to adjust the gain S2G (i.e., +2 dB), such that the gain SOG is increased to +1.4 dB from +1.2 dB. At time t7, the post-smoothing unit 16_1 generates the smooth gain SMG with −0.4 dB to adjust the gain S2G (i.e., +2 dB), such that the gain SOG is increased to +1.6 dB from +1.4 dB. At time t8, the post-smoothing unit 16_1 then generates the smooth gain SMG with −0.2 dB to adjust the gain S2G (i.e., +2 dB), such that the gain SOG is increased to +1.8 dB from +1.6 dB. Finally, after time t9, the post-smoothing unit 16_1 generates the smooth gain SMG with 0 dB to adjust the gain S2G, i.e., the post-smoothing unit 16_1 stops adjusting the gain S2G of the signals S2, such that the gain SOG of the output signals Sout is increased to +2.0 dB from +1.8 dB.
In this case, the smooth gain generated by the post-smoothing unit 16_1 is adjusted to 0 dB from −0.8 dB gradually, but is not limited thereto. The smooth gain generated by the post-smoothing unit 16_1 can also be adjusted to 0 dB from −N dB gradually when the gain S2G of the signals S2 is updated with +N dB resulting from that the AGC 14 updates gain of the PGA 10 with +N dB.
When the AGC 14 generates the signals S3 to update the gain of the PGA 10 with −N dB according to signal strength of the signals S1, the AGC 14 also generates the signals S4 to enable the post-smoothing unit 16_1 to update the gain of the signals S2 from ADC 12 during a time period after the moments (or transients) of the gain of the PGA 10 changes, such that gain change of the output signals Sout can be smoothed.
At time t6, the post-smoothing unit 16_1 then generates the smooth gain SMG with +0.6 dB to adjust the gain S2G (i.e., +1.0 dB), such that the gain SOG is decreased to +1.6 dB from +1.8 dB. At time t7, the post-smoothing unit 16_1 generates the smooth gain SMG with +0.4 dB to adjust the gain S2G (i.e., +1.0 dB), such that the gain SOG is decreased to +1.4 dB from +1.6 dB. At time t8, the post-smoothing unit 16_1 then generates the smooth gain SMG with +0.2 dB to adjust the gain S2G (i.e., +1.0 dB), such that the gain SOG is decreased to +1.2 dB from +1.4 dB. Finally, after time t9, the post-smoothing unit 16_1 generates the smooth gain SMG with 0 dB to adjust the gain S2G, i.e., the post-smoothing unit 16_1 stops adjusting the gain S2G of the signal S2, such that the gain SOG of the output signal Sout is decreased to +1.0 dB from +1.2 dB.
In this case, the smooth gain generated by the post-smoothing unit 16_1 is adjusted to 0 dB from +0.8 dB gradually, but is not limited thereto. The smooth gain generated by the post-smoothing unit 16_1 can also be adjusted to 0 dB from +N dB gradually when the gain S2G of the signals S2 is updated with −N dB resulting from the AGC 14 updates gain of the PGA 10 with −N dB.
In some embodiments, as shown in
For example, when the AGC 14 updates the gain T_gain(n) of the signals S4 with +1 dB, the smooth gain S_gain (n) generated by the post-smoothing unit 16_1 can be adjusted to 0 dB from −1 dB gradually, such that the gain X(n) of the signals S2 from the ADC 12 can be smoothed. Alternatively, when the AGC 14 updates the gain T_gain(n) of the signals S4 with −1 dB, the smooth gain S_gain (n) generated by the post-smoothing unit 16_1 can be adjusted to 0 dB from +1 dB gradually, such that the gain X(n) of the signals S2 from the ADC 12 can be smoothed.
As shown, the post-smoothing unit 16_1 comprises multipliers M1˜M3, a delay unit D1 and an adder A1. The multiplier M1 multiplies the gain X(n) of the signal S2 from the ADC 12 by the smooth gain S_gain(n) from the adder A1. The delay unit D1 receives the smooth gain S_gain(n) from the adder A1 and outputs a delayed smooth gain S_gain(n−1) to the multiplier M2. The multiplier M2 receives the gain T_gain(n) of the signals S4 from the AGC 14, and multiplies the gain T_gain(n) of the signals S4 by the delayed smooth gain S_gain(n−1) and outputs the multiplied gain to the multiplier M3. The multiplier M3 multiplies the multiplied gain from the multiplier M2 by the adjusting factor α and outputs a decayed gain to the adder A1. The adder A1 adds the decayed gain to (1−α) to generate the smooth gain S_gain (n).
For example, the smooth gain S_gain(n−1) is initially at 0 dB, the adjusting factor is 0.9. When the gain T_gain(n) of the signals S4 is updated with −1 dB (i.e., 0.76) by the AGC 14 at time ta, the smooth gain S_gain(n) is −0.9 dB+0.1 at time tn and then the smooth gain S_gain(n) is adjusted to 0 dB from −0.9 dB+0.1 gradually after time tn, It should be noted that the gain T_gain(n+1) of the signals S4 is updated with 0 dB at time ta+1, and when the smooth gain S_gain(n) is 0 dB, it means that the post-smoothing unit 16_1 stops updating the gain of the signals S2 from the ADC 12.
Because the gain Y(n) of the output signal Sout is obtained according to the equation Y(n)=X(n)×S_gain(n), when the gain X(n) of the signals S2 is updated with +1 dB, the multiplier M1 multiplies gain X(n) by the smooth gain S_gain(n−1), such that the gain Y(n) of the output signal Sout is gradually adjusted to +1 dB.
Conversely, when the gain T_gain(n) of the signals S4 is updated with +1 dB (i.e., 1.14) by the AGC 14 at time tn, the smooth gain S_gain(n) is 0.9 dB+0.1 at time tn and then smooth gain S_gain(n) is adjusted to 0 dB from 0.9 dB+0.1 gradually after time tn, It should be noted that the gain T_gain(n+1) of the signals S4 is updated with 0 dB at time tn+1, and when the smooth gain S_gain(n) is 0 dB, it means that the post-smoothing unit 16_1 stops updating the gain of the signals S2 from the ADC 12. Because the gain Y(n) of the output signals Sout is obtained according to the equation Y(n)=X(n)×S_gain(n), when the gain X(n) of the signals S2 is updated with −1 dB, the multiplier M1 multiplies gain X(n) with the smooth gain S_gain(n−1), such that the gain Y(n) of the output signals Sout is gradually adjusted to −1 dB.
Before the AGC 14 generates the signals S3 to update the gain of the PGA 10 with +N dB according to signal strength of the signals S1, the AGC 14 also generates the signals S4 to enable the pre-smoothing unit 16_2 to update the gain of the signals S2 from ADC 12 during a time period before the gain of the PGA 10 changes, such that gain change of the output signal Sout can be smoothed.
For example, the pre-smoothing unit 16_2 generates the smooth gain SMG with +0.2 dB to update the gain S2G (i.e., +1.0 dB), such that the gain SOG of the output signal Sout is increased to +1.2 dB from +1.0 dB, at time t1. At time t2, the pre-smoothing unit 16_2 then generates the smooth gain SMG with +0.4 dB to adjust the gain S2G (i.e., +1.0 dB), such that the gain SOG is increased to +1.4 dB from +1.2 dB.
At time t3, the pre-smoothing unit 16_2 generates the smooth gain SMG with +0.6 dB to adjust the gain S2G (i.e., +1.0 dB), such that the gain SOG is increased to +1.6 dB from +1.4 dB. At time t4, the pre-smoothing unit 16_2 then generates the smooth gain SMG with +0.8 dB to adjust the gain S2G (i.e., +1.0 dB), such that the gain SOG is increased to +1.8 dB from +1.6 dB. Finally, after time t5, the pre-smoothing unit 16_2 generates the smooth gain SMG with 0 dB to adjust the gain S2G, i.e., the post-smoothing unit 16_1 stops adjusting the gain S2G of the signals S2. Then, the gain SOG of the output signals Sout is increased to +2.0 dB from +1.8 dB when the gain S2G of the signals S2 is increased to +2 dB from +1 dB and the AGC 14 updates gain of the PGA 10 with +1 dB at time t5.
In this case, the smooth gain generated by the pre-smoothing unit 16_2 is adjusted to 0.8 dB from 0 dB gradually during a time period, and is updated with 0 dB after the time period, but is not limited thereto. The smooth gain generated by the pre-smoothing unit 16_2 can also be adjusted to 0 dB from −N dB gradually during a time period, and is updated with 0 dB after the time period when the gain S2G of the signals S2 is updated with +N dB resulting from that the AGC 14 updates gain of the PGA 10 with +N dB.
When the AGC 14 generates the signals S3 to update the gain of the PGA 10 with −N dB according to signal strength of the signals S1, the AGC 14 also generates the signals S4 to enable the pre-smoothing unit 16_2 to decrease the gain of the signals S2 from ADC 12 during a time period before the gain of the PGA 10 changes, such that gain change of the output signals Sout can be smoothed.
At time t1, the pre-smoothing unit 16_2 generates the smooth gain SMG with −0.2 dB to adjust the gain S2G of +2.0 dB, such that the gain SOG of the output signals Sout is only decreased to +1.8 dB rather than +2.0 dB. At time t2, the pre-smoothing unit 16_2 then generates the smooth gain SMG with −0.4 dB to adjust the gain S2G of +2.0 dB, such that the gain SOG is decreased to +1.6 dB rather than +2.0 dB or +1.8 dB.
At time t3, the pre-smoothing unit 16_2 generates the smooth gain SMG with −0.6 dB to adjust the gain S2G of +2.0 dB, such that the gain SOG is decreased to +1.4 dB rather than +2.0 dB or +1.6 dB. At time t4, the pre-smoothing unit 16_2 then generates the smooth gain SMG with −0.8 dB to adjust the gain S2G of +2.0 dB, such that the gain SOG is decreased to +1.2 dB from +1.4 dB. Finally, after time t5, the pre-smoothing unit 16_2 generates the smooth gain SMG with 0 dB to adjust the gain S2G, i.e., the pre-smoothing unit 16_1 stops adjusting the gain S2G of the signals S2. Then, the gain SOG of the output signals Sout is decreased to +1.0 dB from +1.2 dB because the gain S2G of the signals S2 is adjusted to +1.0 dB from +2.0 dB at time t5 resulting from the AGC 14 updates gain of the PGA 10 with −1 dB at time t5.
In this case, the smooth gain generated by the pre-smoothing unit 16_2 is adjusted to −0.8 dB from 0 dB gradually during a time period and is updated with 0 dB after the time period, but is not limited thereto. The smooth gain generated by the pre-smoothing unit 16_2 can also be adjusted to 0 dB from −N dB gradually during a time period, and is updated with 0 dB after the time period when the gain S2G of the signal S2 is updated with −N dB resulting from that the AGC 14 updates gain of the PGA 10 with −N dB.
In some embodiments, as shown in
When the smooth gain S_gain(n) is not equal to the gain T_gain(n) of the signals S4 provided by the AGC 14, the pre-smoothing unit 16_2 generates the smooth gain S_gain(n) according to an equation S_gain(n)=β×S_gain(n−1), in which β represents an adjusting factor. For example, the adjusting factor β can be 0.1×N dB if the AGC 14 updates the PGA 12 with +N dB, or can be 0.1×(−N)dB if the AGC 14 updates the PGA 12 with −N dB. Y(n) represents the gain of the output signals Sout as shown in
When the AGC 14 updates the gain T_gain(n) of the signals S4 with +1.0 dB, the gain Z_gain(n) is +1.0 dB calculated by the equation Z_gain(n)=T_gain(n)×Z_gain(n−1). As described above, the gain Z_gain(n) is still maintained at +1.0 dB when the gain T_gain(n+1) is updated with 0 dB by the AGC 14. When the smooth gain S_gain(n) does not reach +1.0 dB (i.e. the gain T_gain(n)) provided by the AGC 14, the smooth gain S_gain(n) generated by the pre-smoothing unit 16_2 can be adjusted to +1.0 dB from 0 dB gradually, such that the gain X(n) of the signals S2 from the ADC 12 can be smoothed.
When the AGC 14 updates the gain T_gain(n) of the signals S4 with −1.0 dB, the gain Z_gain(n) is set to −1.0 dB calculated by the equation Z_gain(n)=T_gain(n)×Z_gain(n−1). As described above, the gain Z_gain(n) is still maintained at −1.0 dB when the gain T_gain(n+1) is updated with 0 dB by the AGC 14. When the smooth gain S_gain(n) does not reach −1.0 dB (i.e. the gain T_gain(n)) provided by the AGC 14, the smooth gain S_gain (n) generated by the pre-smoothing unit 16_2 can be adjusted to −1.0 dB from 0 dB gradually, such that the gain X(n) of the signals S2 from the ADC 12 can be smoothed.
When the smooth gain S_gain(n) is equal to the gain Z_gain(n), the smooth gain S_gain(n) and the gain Z_gain(n) are both updated to 0 dB, i.e., the pre-smoothing unit 16_2 generates the smooth gain S_gain(n) with 0 dB to update the gain X(n) of the signals S2 from the ADC 12. Namely, the pre-smoothing unit 16_2 stops updating the gain X(n) of the signals S2 from the ADC 12.
As shown, the pre-smoothing unit 16_2 comprises multipliers M4˜M6, a subtractor SU1, a determining unit DU1, a switching unit SW1, a delay unit D2 and a multiplexer MP1. The multiplier M4 multiplies the gain X(n) of the signals S2 from the ADC 12 by the smooth gain S_gain(n) from the multiplexer MP1. The multiplier M5 stores the gain T_gain(n) of the signals S4 updated by the AGC 14 to serve as the gain Z_gain(n) until the smooth gain S_gain(n) is equal to the gain Z_gain(n). The subtractor SU1 subtracts the gain Z_gain(n) from the smooth gain S_gain(n) and outputs the subtracted result to the determining unit DU1. The determining unit DU1 determines whether the smooth gain S_gain(n) is equal to the gain Z_gain(n) according to the subtracted result and outputs two signals SY and SN according to the determined results.
As the subtracted result is not zero, i.e., the smooth gain S_gain(n) is not equal to the gain Z_gain(n), the determining unit DU1 outputs the signal SN with a high logic level and the signal SY with a low logic level. Because the signal SY is at the low logic level, the switching unit SW1 does not output a gain with 0 dB (i.e., 1.0 ) to reset the gain Z_gain(n). Because the signal SN is at the high logic level, the multiplexer MP1 outputs the result of the multiplier M6 to serve as the smooth gain S_gain(n). At this time, i.e., the smooth gain S_gain(n) is not equal to the gain Z_gain(n), the multiplier M6 multiplies the adjusting factor α by a previous smooth gain S_gain(n−1) and outputs the multiplied result to the multiplexer MP1. The multiplexer MP1 outputs the multiplied result, i.e., the previous smooth gain S_gain(n−1) multiplied by the adjusting factor A, to serve as the smooth gain S_gain(n).
When the subtracted result is zero, it means that the smooth gain S_gain(n) is equal to the gain Z_gain(n), and then the determining unit DU1 outputs the signal SN with a low logic level and the signal SY with a high logic level. Because the signal SY is at the high logic level, the switching unit SW1 is turned on to output a gain with 0 dB (i.e., 1.0 ) to update the gain Z_gain(n). In addition, because the signal SN is at the low logic level, the multiplexer MP1 outputs a gain with 0 dB (i.e., 1.0) to serve as the smooth gain S_gain(n). Then, the multiplier M4 multiplies the gain X(n) of the signals S2 from the ADC 12 by the smooth gain S_gain(n) of 0 dB from the multiplexer MP1. Namely, the pre-smoothing unit 16_2 stops updating the gain X(n) of the signal S2 from the ADC 12.
For example, the smooth gain S_gain(n) is initially at 0 dB, the adjusting factor β is 0.1 dB if the AGC 14 updates the PGA 12 with +1.0 dB. When the gain T_gain(n) of the signals S4 is updated with +1.0 dB (i.e., 1.14) by the AGC 14 at time tn, the multiplier M5 stores the gain T_gain(n) (i.e. +1.0 dB) to serve as the gain Z_gain(n). The subtractor SU1 subtracts the gain Z_gain(n) (i.e. +1.0 dB) from the smooth gain S_gain(n) and outputs the subtracted result to the determining unit DU1. The determining unit DU1 determines that the smooth gain S_gain(n) is not equal to the gain Z_gain(n) according to the subtracted result and outputs the signal SN with a high logic level and the signal SY with a low logic level. Hence, the switching unit SW1 does not output a gain with 0 dB to update the gain Z_gain(n) and the multiplexer MP1 outputs the result of the multiplier M6 to serve as the smooth gain S_gain(n). The multiplier M6 multiplies the adjusting factor β (i.e., +0.1 dB) by a previous smooth gain S_gain(n−1) (i.e., 0 dB) and outputs the multiplied result with +0.1 dB to the multiplexer MP1. The multiplexer MP1 outputs the multiplied result with +0.1 dB serving as the smooth gain S_gain(n).
Because the current smooth gain S_gain(n) with +0.1 dB is not equal to the gain T_gain(n) with +1.0 dB, the determining unit DU1 outputs the signal SN with the high logic level and the signal SY with the low logic level again. The multiplier M6 multiplies the adjusting factor β (i.e., +0.1 dB) by the previous smooth gain S_gain(n−1) with +0.1 dB and outputs the multiplied result with +0.2 dB to the multiplexer MP1. The multiplexer MP1 outputs the multiplied result with +0.2 dB serving as the smooth gain S_gain(n). Similarly, because the current smooth gain S_gain(n) with +0.2 dB is not equal to the gain T_gain(n) with +1.0 dB, the determining unit DU1 outputs the signal SN with the high logic level and the signal SY with the low logic level again. The multiplier M6 multiplies the adjusting factor β (i.e., +0.1 dB) by the previous smooth gain S_gain(n−1) with +0.2 dB and outputs the multiplied result with +0.3 dB to the multiplexer MP1. The multiplexer MP1 outputs the multiplied result with +0.3 dB serving as the smooth gain S_gain(n). And so on, the delay unit D2, the multiplier M6 and the multiplexer MP1 updates the smooth gain S_gain(n) by the adjusting factor β (i.e., +0.1 dB) over and over, until the smooth gain S_gain(n) is equal to the gain Z_gain(n).
When the smooth gain S_gain(n) reaches (or equals) the gain Z_gain(n), the determining unit DU1 outputs the signal SN with a low logic level and the signal SY with a high logic level. Because the signal SY is at the high logic level, the switching unit SW1 is turned on to output a gain with 0 dB (i.e., 1.0) to update the gain Z_gain(n). In addition, because the signal SN is at the low logic level, the multiplexer MP1 outputs a gain with 0 dB (i.e., 1.0) to serve as the smooth gain S_gain(n). Then, the multiplier M4 multiplies the gain X(n) of the signal S2 from the ADC 12 by the smooth gain S_gain(n) of 0 dB from the multiplexer MP1. Namely, the pre-smoothing unit 16_2 stops updating the gain X(n) of the signals S2 from the ADC 12.
Alternatively, the adjusting factor β is −0.1 dB if the AGC 14 updates the PGA 12 with −1.0 dB. When the gain T_gain(n) of the signal S4 is updated with −1 dB (i.e., 0.76) by the AGC 14, the multiplier M5 stores the gain T_gain(n) (i.e. −1.0 dB) to serve as the gain Z_gain(n). The subtractor SU1 subtracts the gain Z_gain(n) (i.e. −1.0 dB) from the smooth gain S_gain(n) and outputs the subtracted result to the determining unit DU1. The determining unit DU1 determines that the smooth gain S_gain(n) is not equal to the gain Z_gain(n) according to the subtracted result and outputs the signal SN with a high logic level and the signal SY with a low logic level. Hence, the switching unit SW1 does not output a gain with 0 dB to reset the gain Z_gain(n) and the multiplexer MP1 outputs the result of the multiplier M6 to serve as the smooth gain S_gain(n). The multiplier M6 multiplies the adjusting factor β (i.e., −0.1 dB) by a previous smooth gain S_gain(n−1) (i.e., 0 dB) and outputs the multiplied result with −0.1 dB to the multiplexer MP1. The multiplexer MP1 outputs the multiplied result with −0.1 dB serving as the smooth gain S_gain(n).
Because the current smooth gain S_gain(n) with −0.1 dB is not equal to the gain T_gain(n) with −1.0 dB, the determining unit DU1 outputs the signal SN with the high logic level and the signal SY with the low logic level again. The multiplier M6 multiplies the adjusting factor β (i.e., −0.1 dB) by the previous smooth gain S_gain(n−1) with −0.1 dB and outputs the multiplied result with −0.2 dB to the multiplexer MP1. The multiplexer MP1 outputs the multiplied result with −0.2 dB serving as the smooth gain S_gain(n). Similarly, because the current smooth gain S_gain(n) with −0.2 dB is not equal to the gain T_gain(n) with −1.0 dB, the determining unit DU1 outputs the signal SN with the high logic level and the signal SY with the low logic level again. The multiplier M6 multiplies the adjusting factor β (i.e., −0.1 dB) by the previous smooth gain S_gain(n−1) with −0.2 dB and outputs the multiplied result with −0.3 dB to the multiplexer MP1. The multiplexer MP1 outputs the multiplied result with −0.3 dB serving as the smooth gain S_gain(n). And so on, the delay unit D2, the multiplier M6 and the multiplexer MP1 update the smooth gain S_gain(n) with −0.1 dB over and over, until the smooth gain S_gain(n) is equal to the gain T_gain(n).
When the smooth gain S_gain(n) reaches (or equals) the gain T_gain(n), the determining unit DU1 outputs the signal SN with a low logic level and the signal SY with a high logic level. Because the signal SY is at the high logic level, the switching unit SW1 is turned on to output a gain with 0 dB (i.e., 1.0) to update the gain Z_gain(n). In addition, because the signal SN is at the low logic level, the multiplexer MP1 outputs a gain with 0 dB (i.e., 1.0) to serve as the smooth gain S_gain(n). Then, the multiplier M4 multiplies the gain X(n) of the signals S2 from the ADC 12 by the smooth gain S_gain(n) of 0 dB from the multiplexer MP1. Namely, the pre-smoothing unit 16_2 stops updating the gain X(n) of the signals S2 from the ADC 12.
Before the AGC 14 generates the signals S3 to update the gain of the PGA 10 with +N dB according to signal strength of the signals S1, the AGC 14 generates the signals S4 to enable the mix-smoothing unit 16_3 to update the gain of the signals S2 from ADC 12 during a first time period. After the AGC 14 generates the signal S3 to update the gain of the PGA 10 by +N dB, the AGC generates the signal S4 to enable the mix-smoothing unit 16_3 to update the gain of the signal S2 from ADC 12 during a second time period.
At time t3, the mix-smoothing unit 16_3 generates the smooth gain SMG with +0.2 dB to adjust the gain S2G (i.e., +1.0 dB), such that the gain SOG of the output signals Sout is increased to +1.2 dB from +1.0 dB. At time t4, the mix-smoothing unit 16_3 then generates the smooth gain SMG with +0.4 dB to adjust the gain S2G (i.e., +1.0 dB), such that the gain SOG is increased to +1.4 dB from +1.2 dB. At time t5, the mix-smoothing unit 16_3 generates the smooth gain SMG with −0.4 dB to adjust the gain S2G (i.e., +2 dB), such that the gain SOG of the output signals Sout is increased to +1.6 dB from +1.4 dB. At time t6, the mix-smoothing unit 16_3 then generates the smooth gain SMG with −0.2 dB to adjust the gain S2G (i.e., +2 dB), such that the gain SOG is increased to +1.8 dB from +1.6 dB.
Finally, after time t7, the mix-smoothing unit 16_3 generates the smooth gain SMG with 0 dB to adjust the gain S2G, i.e., the mix-smoothing unit 16_3 stops updating the gain S2G of the signals S2. Then, the gain SOG of the output signals Sout is increased to +2.0 dB from +1.8 dB because the gain S2G of the signals S2 is adjusted to +2.0 dB from +1.0 dB at time t5.
As shown, the gain S2G of the signals S2 is adjusted to +1.0 dB from +2.0 dB at time t5 as the AGC 14 updates gain of the PGA 10 with −1 dB at time t5. The mix-smoothing unit 16_3 generates the smooth gain SMG to update (decrease) the gain of the signals S2 from ADC 12 during times t3 and t4 and to update (increase) the gain of the signals S2 during times t5 and t6, such that gain change of the output signal Sout can be smoothed.
At time t3, the mix-smoothing unit 16_3 generates the smooth gain SMG with −0.2 dB to adjust the gain S2G (i.e., +1.0 dB), such that the gain SOG of the output signals Sout is decreased to +1.8 dB from +2.0 dB. At time t4, the mix-smoothing unit 16_3 then generates the smooth gain SMG with −0.4 dB to adjust the gain S2G (i.e., +1.0 dB), such that the gain SOG is decreased to +1.6 dB from +1.8 dB. At time t5, the mix-smoothing unit 16_3 generates the smooth gain SMG with +0.4 dB to adjust the gain S2G (i.e., +2 dB), such that the gain SOG of the output signals Sout is decreased to +1.4 dB from +1.6 dB. At time t6, the mix-smoothing unit 16_3 then generates the smooth gain SMG with +0.2 dB to adjust the gain S2G (i.e., +2 dB), such that the gain SOG is increased to +1.2 dB from +1.4 dB.
Finally, after time t7, the mix-smoothing unit 16_3 generates the smooth gain SMG with 0 dB to adjust the gain S2G, i.e., the mix-smoothing unit 16_3 stops updating the gain S2G of the signals S2. Then, the gain SOG of the output signals Sout is decreased to +1.0 dB from +1.2 dB because the gain S2G of the signals S2 is updated to +1.0 dB from +2.0 dB at time t5.
In some embodiments, as shown in
In the case where the gain of the PGA 10 is updated by +1 dB, the AGC 14 generates the signals S4 to enable the pre-smoothing unit 16_3 of the mix-smoothing unit 16_5 to gradually update the gain of the signals S2 with +0.5 dB in a first time period before the AGC 14 generates the signals S3 to update the gain of the PGA 10 with +1 dB according to signal strength of the signals S1. During the first time period, the post-smoothing 16_4 does not update the gain X(n) of the signals S2, i.e., the S2_gain(n) is 0 dB, and the gain Y(n) of the output signals Sout is equal to the gain X″(n) generated by the multiplier M4. Namely, the gain Y(n) of the output signals Sout can be obtained according to an equation Y(n)=X″(n)=X(n)×S1_gain(n).
Then, after the AGC 14 generates the signals S3 to update the gain of the PGA 10 by +1 dB, the AGC 14 generates the signals S4 to enable the post-smoothing unit 16_4 of the mix-smoothing unit 16_5 to update the gain of the signals S2 by −0.5 dB gradually. During the second time period, the pre-smoothing 16_3 does not update the gain X(n) of the signals S2, i.e., the S1_gain(n) is 0 dB, and the gain X(n) of the signals S2 is equal to the gain X″(n) generated by the multiplier M4. Namely, the gain Y(n) of the output signals Sout can be obtained according to an equation Y(n)=X″(n)×S2_gain(n)=X(n)×S2_gain(n).
For example, when the AGC 14 is going to update the PAG 10 by +1 dB, the AGC 14 may update the gain T1_gain(n) of the signals S4 by +0.5 dB in advance. Hence, the delay unit D2, the multiplier M6 and the multiplexer MP1 updates the smooth gain S1_gain(n) by the adjusting factor β (i.e., +0.1 dB), over and over during the first time period, until the smooth gain S1_gain(n) is equal to the gain T1_gain(n), i.e., +0.5 dB. Because of the equation Y(n)=X″(n)=X(n)×S1_gain(n), the gain Y(n) of the output signals Sout can be updated by the adjusting factor β (i.e., +0.1 dB) over and over until the smooth gain S1_gain(n) reaches +0.5 dB. When the smooth gain S1_gain(n) reaches (or equals) +0.5 dB (i.e., the gain T_gain(n)), the gain Z_gain(n) and the smooth gain S1_gain(n) are both updated with 0 dB. Namely, the pre-smoothing unit 16_3 stops updating the gain X(n) of the signals S2 from the ADC 12.
When the AGC 14 updates the PGA 10 by +1.0 dB, the AGC 14 also updates the gain T2_gain(n) of the signals S4 by −0.5 dB, such that the smooth gain S2_gain(n) is updated with 0 dB from −0.5 dB gradually. Because the gain Y(n) of the output signals Sout is obtained according to the equation Y(n)=X″(n)×S2_gain(n)=X(n)×S2_gain(n), as the smooth gain S2_gain(n) is updated to 0 dB from −0.5 dB gradually, the gain Y(n) of the output signals Sout is gradually adjusted to +1 dB from +0.5 dB. When the smooth gain S2_gain(n) is 0 dB, it means that the post-smoothing unit 16_4 stops updating the gain X(n) of the signals S2 from the ADC 12.
In a case where the gain of the PGA 10 is updated with −1 dB, the AGC 14 generates the signals S4 to enable the pre-smoothing unit 16_2 of the mix-smoothing unit 16_3 to update the gain of the signals S2 by −0.5 dB in a first time period before the AGC 14 generates the signals S3 to update the gain of the PGA 10 by −1 dB according to signal strength of the signals S1. During the first time period, the post-smoothing 16_4 does not update the gain X(n) of the signals S2, i.e., the S2_gain(n) is 0 dB, and the gain Y(n) of the output signals Sout is equal to the gain X″(n) generated by the multiplier M4. Namely, the gain Y(n) of the output signals Sout can be obtained according to an equation Y(n)=X″(n)=X(n)×S1_gain(n).
Then, after the AGC 14 generates the signals S3 to update the gain of the PGA 10 by −1 dB, the AGC 14 generates the signals S4 to enable the post-smoothing unit 16_4 of the mix-smoothing unit 16_3 to update the gain X(n) of the signals S2 with −0.5 dB. During the second time period, the pre-smoothing 16_3 does not update the gain X(n) of the signals S2, i.e., the S1_gain(n) is 0 dB, and the gain X(n) of the signals S2 is equal to the gain X″(n) generated by the multiplier M4. Namely, the gain Y(n) of the output signals Sout can be obtained according to an equation Y(n)=X″(n)×S2_gain(n)=X(n)×S2_gain(n).
For example, when the AGC 14 is going to update the PAG 10 by −1 dB, the AGC 14 may update the gain T1_gain(n) of the signals S4 to −0.5 dB in advance. Hence, the delay unit D2, the multiplier M6 and the multiplexer MP1 update the smooth gain Si_gain(n) with the adjusting factor β (i.e., −0.1 dB) over and over during the first time period, until the smooth gain S1_gain(n) is equal to the gain T1_gain(n), i.e., −0.5 dB. Because of the equation Y(n)=X″(n)=X(n)×S1_gain(n), the gain Y(n) of the output signals Sout can be updated with the adjusting factor β (i.e., −0.1 dB) over and over until the smooth gain S1_gain(n) reaches −0.5 dB. When the smooth gain S1_gain(n) reaches (or equals) −0.5 dB (i.e., the gain T_gain(n)), the gain Z_gain(n) and the smooth gain S1_gain(n) are both updated with 0 dB. Namely, the pre-smoothing unit 16_3 stops updating the gain X(n) of the signals S2 from the ADC 12.
When the AGC 14 updates the PGA 10 with −1.0 dB, the AGC 14 also updates the gain T2_gain(n) of the signals S4 with +0.5 dB, such that the smooth gain S2_gain(n) is adjusted to 0 dB from +0.5 dB gradually. Because the gain Y(n) of the output signals Sout is obtained according to the equation Y(n)=X″(n)×S2_gain(n)=X(n)×S2_gain(n), as the smooth gain S2_gain(n) is adjusted to 0 dB from +0.5 dB gradually, the gain Y(n) of the output signals Sout is gradually adjusted to −1 dB from −0.5 dB. Namely, when the smooth gain S2_gain(n) is 0 dB, the post-smoothing unit 16_4 stops updating the gain X(n) of the signals S2 from the ADC 12.
While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.
