Frequency divider and frequency division system

Abstract

The application discloses a frequency divider and a frequency division system, and relates to the field of signal processing.The frequency divider comprises an input port, an all-pass filter, a first adder and a second adder.The input port is connected with the input end of the all-pass filter, the input end of the first adder and the input end of the second adder.The output end of the all-pass filter is connected with the input end of the first adder and the input end of the second adder.The all-pass filter filters an original signal input by the input port based on preset filter coefficients to obtain a filtered first signal.The output end of the first adder is connected with a high-pass output port of the frequency divider, and the output end of the second adder is connected with a low-pass output port of the frequency divider.The first adder is used for adding a negative value of the first signal to the original signal to obtain a high-pass signal of the frequency divider.The second adder is used for adding the first signal to the original signal to obtain a low-pass signal of the frequency divider.The application provides a frequency divider based on an all-pass filter, which effectively reduces the occupied computing resources of the frequency divider.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of signal processing, and more particularly, to a frequency divider and a frequency division system. BACKGROUND

[0002] A conventional frequency division system needs to separate signals of different frequency bands by a frequency divider to avoid sound interference between different units. The frequency divider is divided into passive device frequency division and active filter frequency division. The passive device is an LC device to form a physical frequency divider, which has a large size and is easily affected by the impedance matching of the loudspeaker. The active filter can avoid the influence of the impedance matching of the loudspeaker, including an analog filter frequency divider design through an operational amplifier and a digital frequency divider design in an audio processing chip. The analog frequency divider needs to occupy the circuit board area and lacks application advantages in small devices, while the digital frequency divider is widely used.

[0003] The commonly used digital frequency dividers on the market are Butterworth form and L-R form. Taking a second-order Butterworth filter as an example, it includes four shifters and five multipliers, and even after normalization, four multipliers are needed. The L-R frequency divider needs two Butterworth filters to be cascaded, that is, a 2-order L-R frequency divider needs at least 8 multipliers. With the increase of the order of the frequency divider, the number of multipliers will continue to increase, resulting in the continuous increase of the consumption of chip computing resources and the demand for power. SUMMARY

[0004] An object of the present application is to provide a frequency division scheme for reducing the consumption of computing resources and the demand for power.

[0005] According to a first aspect of the present application, a frequency divider is provided, comprising: an input port, which is communicatively connected with an input end of an all-pass filter, an input end of a first adder and an input end of a second adder, respectively;

[0006] an all-pass filter, wherein an output end of the all-pass filter is communicatively connected with the input end of the first adder and the input end of the second adder, respectively, and the all-pass filter filters an original signal input by the input port based on a preset filter coefficient to obtain a first filtered signal;

[0007] an output end of the first adder is communicatively connected with a high-pass output port of the frequency divider, and an output end of the second adder is communicatively connected with a low-pass output port of the frequency divider;

[0008] wherein the first adder is configured to add a negative value of the first signal to the original signal to obtain a high-pass signal of the frequency divider; and the second adder is configured to add the first signal to the original signal to obtain a low-pass signal of the frequency divider.

[0009] According to a second aspect of the present application, a frequency division system is provided, comprising: a frequency divider, an amplifier module and a speaker unit, the amplifier module comprising a first amplifier module and a second amplifier module, the speaker unit comprising a tweeter unit and a woofer unit; the frequency divider comprises:

[0010] an input port, which is communicatively connected with an input end of the all-pass filter, an input end of the first adder and an input end of the second adder respectively;

[0011] an all-pass filter, an output end of the all-pass filter being communicatively connected with an input end of the first adder and an input end of the second adder respectively, the all-pass filter filtering an original signal input by the input port based on a preset filter coefficient to obtain a filtered first signal;

[0012] an output end of the first adder being communicatively connected with a high-pass output port of the frequency divider, an output end of the second adder being communicatively connected with a low-pass output port of the frequency divider;

[0013] wherein, the first adder is configured to add a negative value of the first signal to the original signal to obtain a high-pass signal of the frequency divider; the second adder is configured to add the first signal to the original signal to obtain a low-pass signal of the frequency divider;

[0014] the high-pass output port of the frequency divider, the first amplifier module and the tweeter unit are sequentially communicatively connected, the low-pass output port of the frequency divider, the second amplifier module and the woofer unit are sequentially communicatively connected.

[0015] Optionally, the system further comprises:

[0016] a phase compensation filter, an output port of the phase compensation filter being communicatively connected with an input port of the frequency divider.

[0017] Optionally, the phase compensation filter is an N-order all-pass filter.

[0018] Optionally, a group delay of the N-order all-pass filter is determined by the following formula:

[0019]

[0020] wherein, is an objective function, the objective function is:

[0021]

[0022] wherein, is a group delay of the N-order all-pass filter, is a target phase of the Nth all-pass filter, is a frequency.

[0023] Optionally, a group delay of the Nth all-pass filter is represented by the following formula:

[0024]

[0025] wherein, is an imaginary part of a transfer function of the Nth all-pass filter, is a real part of the transfer function of the Nth all-pass filter, is a phase of the Nth all-pass filter transfer function, the Nth all-pass filter transfer function being:

[0026]

[0027] wherein, is a preset filter coefficient of the Nth all-pass filter.

[0028] Optionally, the target phase of the Nth all-pass filter is determined by the following formula:

[0029]

[0030] wherein, is a group delay of the frequency divider.

[0031] Optionally, the system comprises a upsampling rate module, a first low-pass filter, a downsampling rate module and a second low-pass filter.

[0032] The upsampling rate module, the first low-pass filter, the phase compensation filter, the downsampling rate module, the second low-pass filter and the frequency divider are sequentially and communicatively connected.

[0033] Optionally, the first low-pass filter and the second low-pass filter respectively comprise:

[0034] a second input port, which is communicatively connected with an input end of a second all-pass filter and an input end of a third adder;

[0035] a second all-pass filter, an output end of the second all-pass filter being communicatively connected with an input end of the third adder, the second all-pass filter filtering a second original signal input by the second input port based on a preset filter coefficient to obtain a filtered second signal;

[0036] an output end of the third adder being a second output port, the third adder being configured to add the second signal and the second original signal to obtain an output signal of the low-pass filter.

[0037] Optionally, the system further comprises a first dynamic range control unit and a second dynamic range control unit, the first dynamic range control unit is arranged between the frequency divider and the first amplifier, and the second dynamic range control unit is arranged between the frequency divider and the second amplifier; the first dynamic range control unit and the second dynamic range control unit are used to compress the signal output by the frequency divider, so as to improve the audio loudness of the system output.

[0038] The application provides a frequency divider, which comprises an input port, a full-band filter, a first adder, a second adder and a high-pass output port and a low-pass output port.

[0039] Other characteristics and advantages of the present application will become apparent from the following detailed description of exemplary embodiments thereof, which description refers to the attached drawings. BRIEF DESCRIPTION OF DRAWINGS

[0040] The accompanying drawings incorporated in and forming a part of the specification, illustrate embodiments of the present application and, together with the description, serve to explain the principles of the present application.

[0041] Figure 1 is a structural schematic diagram of a frequency divider provided by an embodiment of the present application;

[0042] Figure 2 is a structural schematic diagram of a first-order full-band filter provided by an embodiment of the present application;

[0043] Figure 3 is a structural schematic diagram of a second-order full-band filter provided by an embodiment of the present application;

[0044] FIG. 4(a) is a schematic diagram of a frequency-amplitude response curve of a frequency divider provided by an embodiment of the present application;

[0045] FIG. 4(b) is a schematic diagram of a frequency-phase response curve of a frequency divider provided by an embodiment of the present application;

[0046] FIG. 5(a) is a frequency, amplitude response curve of a phase compensation filter according to an embodiment of the present application;

[0047] FIG. 5(b) is a frequency, phase response curve of a phase compensation filter according to an embodiment of the present application;

[0048] Figure 6 FIG. 6 is a group delay curve of a 12th order phase compensation filter according to an embodiment of the present application;

[0049] Figure 7 FIG. 7 is a group delay curve of an 18th order phase compensation filter according to an embodiment of the present application;

[0050] Figure 8 FIG. 8 is a structure diagram of a fractional-N system according to an embodiment of the present application;

[0051] Figure 9 FIG. 9 is a structure diagram of a fractional-N system including up- and down- sampling rate modules and a phase compensation filter according to an embodiment of the present application;

[0052] Figure 10 FIG. 10 is a structure diagram of a fractional-N system including a dynamic range control unit according to an embodiment of the present application. DETAILED DESCRIPTION

[0053] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement of the components and steps set forth in the embodiments, numerical expressions, and numerical values, unless specifically stated otherwise, do not limit the scope of the present application.

[0054] The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the scope of the application, its application, or uses.

[0055] Techniques, methods, and devices known to those of ordinary skill in the relevant art can not be discussed in detail herein. However, where appropriate, such techniques, methods, and devices can be viewed as part of the specification and can be claimed as such.

[0056] In all of the examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not as a limitation on the scope of the exemplary embodiments. Thus, other examples of the exemplary embodiments can have different values.

[0057] It should be noted that like reference numerals and letters refer to like items throughout the attached drawings, and thus, once an item is defined in one drawing, it is not necessary to discuss it further in subsequent drawings.

[0058] It should be noted that like reference numerals and letters refer to like items throughout the attached drawings, and thus, once an item is defined in one drawing, it is not necessary to discuss it further in subsequent drawings.Figure 1 This is a schematic diagram of a frequency divider 100 according to an embodiment of this application, including: an input port, which is communicatively connected to the input of an all-pass filter 101, the input of a first adder 102, and the input of a second adder 103; an all-pass filter 101, the output of which is communicatively connected to the input of the first adder 102 and the input of the second adder 103, wherein the all-pass filter 101 filters the original signal input to the input port based on a preset filtering coefficient to obtain a filtered first signal; the output of the first adder 102 is communicatively connected to the high-pass output port of the frequency divider, and the output of the second adder 103 is communicatively connected to the low-pass output port of the frequency divider; wherein the first adder 102 is used to add the negative value of the first signal to the original signal to obtain the high-pass signal of the frequency divider; and the second adder 103 is used to add the first signal to the original signal to obtain the low-pass signal of the frequency divider.

[0059] In one embodiment of this application, the order of the all-pass filter can be set according to actual usage requirements, so as to... Figure 2 and Figure 3 Taking the first-order and second-order all-pass filters shown as examples, where X(Z) is the input signal and Y(Z) is the output signal, The shifter is represented by a first-order all-pass filter, which includes only one multiplier, and a second-order all-pass filter, which includes only two multipliers. Compared to Butterworth and LR filters of the same order, the first-order all-pass filter reduces the number of multipliers by 1 and 3 respectively, while the second-order all-pass filter reduces the number by 2 and 6 respectively. Furthermore, the reduction in multipliers increases with the filter order; for example, a fourth-order all-pass filter includes 4 multipliers, while the Butterworth and LR filters include 8 and 16 multipliers respectively. Therefore, the technical solution of this application can effectively reduce the computational load of the chip. In this example, the preset filter coefficients in the multipliers of the input all-pass filter can be pre-tested and set according to the actual situation of the frequency divider.

[0060] In this embodiment, the first-order all-pass filter introduces a 180-degree phase lag after the frequency point, making the original signal and its processed signal orthogonal. When the adder synthesizes the two signals, the low-frequency components are superimposed in the same direction due to the phase difference approaching 0°, resulting in signal amplitude enhancement, while the high-frequency components are canceled out of phase due to the phase difference approaching 180°; thus achieving low-pass characteristics. The subtractor exhibits complementary characteristics: the low-frequency band is canceled out by in-phase subtraction, and the high-frequency band is reinforced by out-of-phase subtraction, achieving high-pass filtering characteristics.

[0061] In this embodiment, a high-pass signal refers to a signal with a frequency higher than the division point, and a low-pass signal refers to a signal with a frequency lower than the division point.

[0062] In this example, a frequency divider is provided, based on the phase rotation function of all-pass filter, through addition and subtraction operation, construct the constructive / destructive interference condition in frequency domain, so as to realize the frequency separation without amplitude distortion, compared with the traditional frequency divider using Butterworth or L-R filter, can effectively reduce the calculation resource consumption of frequency divider, improve the processing speed of chip, at the same time, the frequency division effect is the same as the traditional frequency divider, figure 4(a) and figure 4(b) are the frequency, amplitude or phase response curve of frequency divider based on 2 order L-R filter and frequency divider based on 2 order all-pass filter under the same condition, it can be seen that the high frequency signal LR2H and AP2H output by the two are exactly the same, and the low frequency signal LR2L and AP2L are also exactly the same.

[0063] Figure 8 It is a structure schematic diagram of a frequency division system 1000 provided by the embodiment of the application, comprising: a frequency divider 100, an amplifier module and a speaker unit, the amplifier module comprises a first amplifier module 200 and a second amplifier module 300, and the speaker unit comprises a high sound unit 210 and a low sound unit 220; the frequency divider 100 comprises: an input port, which is in communication connection with the input end of the all-pass filter, the input end of the first adder and the input end of the second adder respectively; an all-pass filter, the output end of the all-pass filter is in communication connection with the input end of the first adder and the input end of the second adder respectively, and the all-pass filter filters the original signal input by the input port based on a preset filter coefficient to obtain a filtered first signal; the output end of the first adder is in communication connection with the high-pass output port of the frequency divider, and the output end of the second adder is in communication connection with the low-pass output port of the frequency divider; wherein the first adder is used for adding the negative value of the first signal and the original signal to obtain the high frequency signal of the frequency divider; and the second adder is used for adding the first signal and the original signal to obtain the low frequency signal of the frequency divider. The high-pass output port of the frequency divider 100, the first amplifier module 200 and the high sound unit 210 are sequentially in communication connection, and the low-pass output port of the frequency divider 100, the second amplifier module 300 and the low sound unit 220 are sequentially in communication connection.

[0064] In this example, the frequency division system can divide the original sound signal based on the frequency divider of the foregoing embodiment, and input the amplified signals to the corresponding speaker units through the amplifiers to output the sound signals of the corresponding frequencies. In this way, the overall calculation amount and the sound response speed of the system are effectively reduced.

[0065] In one example of the embodiment, the amplifier module further comprises an analog-to-digital conversion module, which converts the digital signal after frequency division of the frequency divider into an analog signal, and then amplifies the voltage and current of the analog signal through the amplifier to drive the speaker unit to output correspondingly.

[0066] In one example of the embodiment, the system further comprises a phase compensation filter, and an output port of the phase compensation filter is communicatively connected to the input port of the frequency divider.

[0067] In the embodiment, the system can further be provided with a phase compensation filter, and the phase alignment is achieved by using the group delay characteristic of the phase compensation filter, the phase distortion problem caused by the frequency divider is solved, and the output quality of the system is improved.

[0068] In one example of the embodiment, the phase compensation filter is an N-order all-pass filter.

[0069] In the embodiment, the N-order all-pass filter can be used as the phase compensation filter. In the prior art, the phase compensation filter usually adopts a finite impulse response type filter, but the order of the finite impulse response type filter is usually high, and if the L-R filter is used, a very large time delay and a large amount of calculation will be consumed. Therefore, the N-order all-pass filter can be used for phase compensation to further reduce the amount of calculation. In addition, since the aforementioned frequency divider satisfies the same phase of two-way output, the two phase compensation filters respectively arranged in the traditional scheme can be combined into one, and the pre-processing is performed before the frequency divider.

[0070] In one example of the embodiment, the group delay of the N-order all-pass filter is determined by the following formula:

[0071]

[0072]

[0073] wherein, is the group delay of the N-order all-pass filter, is the target phase of the N-order all-pass filter, and w is the frequency.

[0074] In the embodiment, the Newton-type algorithm or the GA algorithm can be used to obtain the optimal solution of the group delay of the compensation filter by different iteration methods, that is, the difference between the group delay of the filter and the target is solved to minimize the variance, so as to realize the compensation of the frequency divider.

[0075] In the example, the target phase of the N-order all-pass filter is determined by the following formula:

[0076]

[0077] wherein, is the group delay of the frequency divider.

[0078] In this case, the group delay of the frequency divider can be tested in advance, and the group delay of the frequency divider is negated by the maximum value of the group delay of the frequency divider, so as to obtain the target phase of the phase compensation filter.

[0079] In one example of the embodiment, the group delay of the Nth-order all-pass filter It is represented by the following formula:

[0080]

[0081] wherein, is the imaginary part of the transfer function of the Nth-order all-pass filter, is the real part of the transfer function of the Nth-order all-pass filter, is the phase of the transfer function of the Nth-order all-pass filter, and the transfer function of the Nth-order all-pass filter is:

[0082]

[0083] wherein, is a preset filter coefficient of the Nth-order all-pass filter.

[0084] In the embodiment, the Nth-order all-pass filter has N parameters, and the transfer function can be represented as:

[0085]

[0086] The transfer function is further expanded into a real part and an imaginary part:

[0087]

[0088] The phase can be represented as:

[0089]

[0090] The group delay can be obtained by taking the derivative of the phase and negating, that is:

[0091]

[0092] Based on this, the construction of the target function is completed.

[0093] In the embodiment, FIG. 5(a) and FIG. 5(b) are frequency and amplitude, phase curves based on the output of the 2nd-order all-pass frequency divider and the frequency and amplitude, phase response curves AP-N12 of the 12th-order all-pass phase compensation filter. In the above manner, the group delay characteristics of the Nth-order all-pass phase compensation filter can be used to realize phase alignment, solve the phase distortion problem caused by the frequency divider, and improve the output quality of the system. At the same time, in order to obtain better results, the order of the phase compensation filter can be increased, such as Figure 6 as shown.Figure 6 For the group delay curve when N is 12, it can be seen that the compensated high-frequency part has slight fluctuation. By further increasing the order, when N is 18, the group delay curve is as shown in Figure 7 It can be seen that the compensated curve has almost the same delay in the full frequency band without fluctuation.

[0094] In the embodiment, the system includes an upsampling rate module 400, a first low-pass filter 500, a downsampling rate module 700, and a second low-pass filter 800; the upsampling rate module 400, the first low-pass filter 500, the phase compensation filter 600, the downsampling rate module 700, the second low-pass filter 800, and the frequency divider 100 are sequentially connected in communication.

[0095] In the embodiment, the frequency division system is as shown in Figure 9 In order to obtain better audio output effect, the phase compensation filter usually adopts a relatively high-order filter setting, and the processing time of the corresponding phase compensation will increase. Based on this, an upsampling rate module can be arranged before phase compensation to increase the sampling rate, reduce the time for collecting each data sample, increase the number of sampling points of the group delay, and reduce the processing time of the compensation filter. After processing, the frequency division processing is performed after the original sampling rate of the audio signal is restored through downsampling. In the embodiment, in order to eliminate the problem of high-frequency spectrum aliasing introduced by upsampling and downsampling, a low-pass filter can be connected after upsampling and downsampling to perform anti-aliasing and eliminate the influence of upsampling to preserve the original signal.

[0096] In the embodiment of the present application, the cutoff frequency of the high-pass filter or the low-pass filter can be set based on actual conditions.

[0097] In an example of the embodiment, the first low-pass filter and the second low-pass filter each include: a second input port, which is connected in communication with the input end of the second all-pass filter and the input end of the third adder; a second all-pass filter, the output end of the second all-pass filter being connected in communication with the input end of the third adder, and the second all-pass filter filtering the second original signal input by the second input port based on a preset filter coefficient to obtain a filtered second signal; and a third adder, the output end of the third adder being a second output port, and the third adder being configured to add the second signal and the second original signal to obtain an output signal of the low-pass filter.

[0098] In the example, the first low-pass filter and the second low-pass filter can be set based on the frequency divider as shown in Figure 1 Only the low-pass part in the frequency divider is retained to realize the function of low-pass filtering. Compared with other types of filters, the low-pass filter based on the all-pass filter has smaller calculation resource consumption, effectively saving the overall power consumption of the system.

[0099] In one example of the embodiment, the system further comprises a first dynamic range control unit 900 and a second dynamic range control unit 910, the first dynamic range control unit 900 is arranged between the frequency divider 100 and the first amplifier 200, and the second dynamic range control unit 910 is arranged between the frequency divider 100 and the second amplifier 300; the first dynamic range control unit and the second dynamic range control unit are used to compress the signal output by the frequency divider, so as to improve the audio loudness of the system output.

[0100] In the embodiments of the present application, as shown in Figure 10 The system can further be provided with a DRC (dynamic range control) unit arranged after the high-pass output and the low-pass output of the frequency divider. The DRC unit can compress the dynamic range of the signal, improve the average loudness of the audio, prevent peak overload distortion, and protect the hardware safety of the system.

[0101] The above has described the embodiments of the present application, the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those skilled in the art without departing from the scope and spirit of the described embodiments. The selection of the terms used herein is intended to best explain the principles of the embodiments, practical application, or technical improvement to the technology in the market, or to enable other ordinary skilled persons in the art to understand the embodiments disclosed herein. The scope of the present application is defined by the appended claims.

Claims

1. A frequency division system, characterized in that, The system includes a crossover, an amplifier module, and a speaker unit. The amplifier module includes a first amplifier module and a second amplifier module. The speaker unit includes a tweeter and a woofer. The crossover includes: The input ports are communicatively connected to the input terminals of the all-pass filter, the first adder, and the second adder, respectively. An all-pass filter is provided, wherein the output of the all-pass filter is communicatively connected to the input of a first adder and the input of a second adder, and the all-pass filter filters the original signal input to the input port based on a preset filtering coefficient to obtain a filtered first signal. The output of the first adder is communicatively connected to the high-pass output port of the frequency divider, and the output of the second adder is communicatively connected to the low-pass output port of the frequency divider. The first adder is used to add the negative value of the first signal to the original signal to obtain the high-pass signal of the frequency divider; the second adder is used to add the first signal to the original signal to obtain the low-pass signal of the frequency divider. The high-pass output port of the crossover, the first amplifier module and the tweeter are sequentially connected in communication, and the low-pass output port of the crossover, the second amplifier module and the woofer are sequentially connected in communication. A phase compensation filter, wherein the output port of the phase compensation filter is communicatively connected to the input port of the frequency divider, wherein the phase compensation filter is an Nth-order all-pass filter, where N is a positive integer; The group delay of the Nth-order all-pass filter It is determined by the following formula: in, Let be the objective function, the objective function for: in, The group delay of an Nth-order all-pass filter. It is the target phase of the Nth-order all-pass filter. For frequency; The group delay of the Nth-order all-pass filter This can be expressed by the following formula: in, Let be the imaginary part of the transfer function of the Nth-order all-pass filter. Let be the real part of the transfer function of the Nth-order all-pass filter. Let be the phase of the transfer function of the Nth-order all-pass filter, and let the transfer function of the Nth-order all-pass filter be: in, These are the preset filter coefficients of the Nth-order all-pass filter; The target phase of the Nth-order all-pass filter is determined by the following formula: in, The group delay of the frequency divider.

2. The system according to claim 1, characterized in that, The system includes an upsampling rate module, a first low-pass filter, an downsampling rate module, and a second low-pass filter; The upsampling rate module, the first low-pass filter, the phase compensation filter, the downsampling rate module, the second low-pass filter, and the frequency divider are sequentially connected in communication.

3. The system according to claim 2, characterized in that, The first low-pass filter and the second low-pass filter each include a second input port, a second full-pass filter, and a third adder: The second input port is communicatively connected to the input of the second all-pass filter and the input of the third adder, respectively. The second all-pass filter has its output terminal communicatively connected to the input terminal of the third adder. The second all-pass filter filters the second original signal input to the second input port based on preset filtering coefficients to obtain the filtered second signal. The output of the third adder is the second output port. The third adder is used to add the second signal to the second original signal to obtain the output signal of the low-pass filter.

4. The system according to claim 1, characterized in that, The system further includes a first dynamic range control unit and a second dynamic range control unit. The first dynamic range control unit is disposed between the crossover and the first amplifier, and the second dynamic range control unit is disposed between the crossover and the second amplifier. The first dynamic range control unit and the second dynamic range control unit are used to compress the signal output by the crossover to improve the audio loudness of the system output.

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