filter

Abstract

The utility model discloses a filter, filter is linked with white noise source module to realize the filtration to white noise signal, its characterized in that, the filter includes: input unit, including high pass filter, high pass filter is linked with the first end of white noise source module to carry out the inhibition to low frequency part among white noise signal, forming unit, including low pass filter, low pass filter is connected between high pass filter output and the second end of white noise source module to carry out the inhibition to high frequency part among white noise signal, output unit, output unit is parallelly connected with low pass filter to adjust the white noise signal after filtering according to the input impedance demand of target test equipment. The present application provides a kind of passive filter circuit with simple structure, it is easy to realize, response stable, need not power supply, is suitable for the analog signal test environment of broadcast audio link, wireless microphone, audio system such as sound console.

Description

Technical Field

[0001] This utility model relates to the field of audio filtering technology, and in particular to filters. Background Technology

[0002] The ITU-R B.559-2 recommendation specifies a standardized weighted spectral curve for converting white noise into weighted colored noise that simulates human hearing, for use in performance testing of audio systems. This standard is widely used to evaluate the performance of audio equipment such as broadcast audio links, wireless microphones, and mixing consoles.

[0003] Existing technologies mostly employ passive filter networks with fixed parameters to implement this weighting process. However, to simulate an accurate weighted spectrum, these passive filters typically require multiple precision components, especially high-precision inductors and capacitors. This not only leads to high hardware costs but also occupies a large physical space. Furthermore, once the spectrum shape is set, it cannot be dynamically adjusted, lacking flexibility. Simultaneously, component deviations caused by device aging or changes in ambient temperature can cause the filter's frequency response to deviate from the standard curve, affecting test accuracy. Utility Model Content

[0004] The purpose of this invention is to provide a passive filter circuit that is simple in structure, easy to implement, stable in response, and requires no power supply. It can convert white noise signals into colored noise signals with spectral characteristics that conform to the ITU-RBS.559-2 recommended standard, thereby solving the problems of complex filter hardware, difficult adjustment, and large influence from component deviation in the prior art. It is suitable for analog signal testing environments of audio systems such as broadcast audio links, wireless microphones, and mixing consoles.

[0005] This utility model discloses a filter, which is connected to a white noise source module to filter white noise signals. The filter includes: The input unit includes a high-pass filter, which is connected to the first end of the white noise source module to suppress the low-frequency components of the white noise signal; The molding unit includes a low-pass filter connected between the output of the high-pass filter and the second terminal of the white noise source module to suppress the high-frequency components in the white noise signal. An output unit is connected in parallel with a low-pass filter to adjust the filtered white noise signal according to the input impedance requirements of the target test equipment.

[0006] In one or more embodiments of this utility model, a first resistor is further connected between the input unit and the first terminal of the white noise source module, the resistance value of the first resistor being less than 100Ω to serve as the source impedance of the white noise signal.

[0007] In one or more embodiments of this utility model, the high-pass filter includes a second resistor and a first capacitor, a first end of the second resistor is connected to the first resistor, a second end of the second resistor is connected to the first capacitor, and a second end of the first capacitor is connected to the second end of the white noise source module.

[0008] In one or more embodiments of this utility model, a first inductor is further connected between the second end of the first capacitor and the second end of the white noise source module to adjust the passband portion of the mid-frequency band of the white noise signal.

[0009] In one or more embodiments of this utility model, the low-pass filter includes a third resistor and a second capacitor, wherein the third resistor and the second capacitor are respectively connected in parallel across the two ends of the first inductor.

[0010] In one or more embodiments of the present invention, a shaping circuit is further included, which is connected between the low-pass filter and the output unit to limit or shape the mid-frequency band of the white noise signal.

[0011] In one or more embodiments of this utility model, the shaping circuit includes a second inductor and a fourth resistor. The first end of the second inductor is connected to the first end of the second capacitor, the second end of the second inductor is connected to the first end of the fourth resistor, and the second end of the fourth resistor is connected to the output unit.

[0012] In one or more embodiments of the present invention, the molding unit further includes a fifth resistor connected between the second end of the fourth resistor and the second end of the second capacitor for further control of the spectral shape.

[0013] In one or more embodiments of the present invention, the output unit includes a sixth resistor, which is connected in parallel across the fifth resistor.

[0014] In one or more embodiments of this utility model, the resistance value of the sixth resistor is not less than 5kΩ.

[0015] The beneficial effects of this invention are as follows: This invention, through an optimized combination of passive RLC components, can accurately convert white noise signals into weighted noise signals conforming to the ITU-RBS.559-2 standard, without requiring an external power supply. It has the advantages of simple structure, convenient implementation, stable frequency response, and low cost. This filter can effectively suppress the low-frequency and high-frequency components of white noise signals and generate colored noise that simulates human hearing through mid-frequency shaping and attenuation, making it suitable for various scenarios such as audio equipment testing and broadcast system verification. Attached Figure Description

[0016] Figure 1 This is a circuit diagram of a filter in one embodiment of the present invention; Figure 2 This is a waveform comparison diagram between the filters of this utility model and those in the prior art.

[0017] In the figure: Input unit 100, high-pass filter circuit 101, shaping unit 200, low-pass filter 201, shaping circuit 202, output unit 300, white noise source module 400. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solutions of this utility model, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of this utility model.

[0019] In the description of this utility model, it should be understood that the terms "vertical", "horizontal", "top", "bottom", "upper", "lower", "front", "rear", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0020] It should be noted that, unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0021] For the above issues, please refer to the appendix. Figure 1As shown, this utility model provides a filter, specifically an ITU-RBS.559-2 weighted filter, which is connected to a white noise source module 400 to filter white noise signals and convert them into weighted colored noise signals conforming to the ITU-RBS.559-2 standard. The filter includes an input unit 100, a shaping unit 200, and an output unit 300. In this embodiment, within the white noise frequency range of 20 Hz to 20 kHz, the frequency can generally be divided into the following approximate ranges based on human auditory characteristics and audio processing habits: the low-frequency part, ranging from 20 Hz to approximately 200 Hz (or 250 Hz), which includes sub-bass and bass frequencies, mainly affecting the thickness and impact of the sound. One of the characteristics of the ITU-RBS.559-2 weighted filter is the suppression of low frequencies below 100 Hz to simulate auditory perception. The mid-frequency range, from approximately 200Hz (or 250Hz) to approximately 5kHz, is the most sensitive frequency band for the human ear, containing most of the energy of speech and musical instruments. Limiting or response shaping the mid-frequency band is the core function of a weighted filter to simulate the mid-frequency characteristics of the program audio. The high-frequency range, from approximately 5kHz to 20kHz, includes treble and ultra-treble frequencies, affecting the brightness, clarity, detail, and spatiality of the sound. Weighted filters suppress these high frequencies to conform to the weighted spectrum curve.

[0022] In a further embodiment, the input unit 100 is designed to process the raw white noise signal from the white noise source module 400.

[0023] Specifically, a first resistor R1 is connected to the first terminal of the white noise source module 400, i.e., the signal input terminal. The resistance value of the first resistor R1 is preferably less than 100Ω. Its function is to serve as the source impedance of the white noise signal, ensuring impedance matching between the signal source and the filter, and reducing signal reflection and energy loss.

[0024] The input unit 100 also includes a high-pass filter 101, which suppresses the low-frequency components of the white noise signal to prevent DC components and unnecessary extremely low-frequency noise from entering the subsequent processing stage. The high-pass filter 101 can be composed of a second resistor R2 and a first capacitor C1. The first terminal of the second resistor R2 is connected to the first resistor R1, and the second terminal of the second resistor R2 is connected to the first capacitor C1. The second terminal of the first capacitor C1 is typically connected to the second terminal of the white noise source module 400, which is ground. In one embodiment, the resistance of the second resistor R2 can be 600Ω, and the capacitance of the first capacitor C1 can be 0.68μF, together forming a high-pass filter with a cutoff frequency below 100Hz.

[0025] To adjust the passband portion of the white noise signal in the mid-frequency band, a first inductor L1 is connected between the second terminal of the first capacitor C1 and the second terminal of the white noise source module 400. The first inductor L1 can be connected in parallel in the circuit for resonant absorption or compensation for low-frequency attenuation. In one embodiment, the inductance value of the first inductor L1 can be 0.8H.

[0026] In a further embodiment, the shaping unit 200 is the core component for implementing the ITU-RBS.559-2 weighted curve, and includes a low-pass filter 201 and a shaping circuit 202.

[0027] The low-pass filter 201 is connected between the output of the high-pass filter 101 and the second terminal of the white noise source module 400. Its main function is to suppress the high-frequency components of the white noise signal. The low-pass filter 201 can be constructed by connecting a third resistor R3 and a second capacitor C2 in parallel, and then connecting them in parallel across the first inductor L1. In one embodiment, the resistance of the third resistor R3 can be 700Ω, and the capacitance of the second capacitor C2 can be 1μF.

[0028] In a further embodiment, the shaping unit 200 further includes a shaping circuit 202 connected between the low-pass filter 201 and the output unit 300. The shaping circuit 202 is used to limit or shape the mid-frequency band of the white noise signal to simulate the mid-frequency characteristics of the program audio. The shaping circuit 202 may consist of a second inductor L2 and a fourth resistor R4. The first terminal of the second inductor L2 is connected to the first terminal of the second capacitor C2, and the second terminal of the second inductor L2 is connected to the first terminal of the fourth resistor R4. In one embodiment, the inductance value of the second inductor L2 may be 0.27H.

[0029] In addition, the molding unit 200 also includes a fifth resistor R5, which is connected between the second terminal of the fourth resistor R4 and the second terminal of the second capacitor C2. The fifth resistor R5, acting as a parallel resistor, is used to set the power attenuation characteristics of the frequency band, further controlling the spectrum shape. In one embodiment, the resistance value of the fourth resistor R4 can be 3.5kΩ, and the resistance value of the fifth resistor R5 can be 2.4kΩ.

[0030] In a further embodiment, the output unit 300 is responsible for the final adjustment of the filtered and shaped white noise signal to adapt to the input impedance requirements of the target test equipment and to avoid the loading effect affecting the filtering characteristics. The output unit 300 is connected in parallel with the low-pass filter 201.

[0031] The output unit 300 may include a sixth resistor R6, which is connected in parallel across the fifth resistor R5. The resistance of the sixth resistor R6 is preferably not less than 5kΩ. In one embodiment, the resistance of the sixth resistor R6 may be 5kΩ or higher to ensure that it acts as an isolation resistor or matching resistor, reducing the impact on the preceding filter circuit.

[0032] In summary, this utility model, through a carefully designed RLC passive network, suppresses low frequencies of the white noise signal output by the white noise source module 400 through the input unit 100, suppresses high frequencies and shapes the intermediate frequencies through the shaping unit 200, and finally performs impedance matching and output through the output unit 300 to generate a weighted noise signal conforming to the ITU-RBS.559-2 standard, which is suitable for performance testing of various audio systems.

[0033] like Figure 2 The image shows a comparison of waveforms between filters in the prior art and the weighted filter in this invention. The yellow waveform curve represents the waveform of a general filter, while the blue waveform curve represents the waveform of the weighted filter in this invention. The comparison shows that the weighted filter has a better suppression effect on waveforms near the main frequency.

[0034] The above embodiments are only for illustrating the technical concept and features of this utility model. Their purpose is to enable those skilled in the art to understand the content of this utility model and implement it. They cannot be used to limit the protection scope of this utility model. All equivalent changes or modifications made in accordance with the spirit and essence of this utility model should be covered within the protection scope of this utility model.

Claims

1. A filter connected to a white noise source module (400) to filter white noise signals, characterized in that, The filter includes: The input unit (100) includes a high-pass filter (101) connected to the first end of the white noise source module (400) to suppress the low-frequency part of the white noise signal; The molding unit (200) includes a low-pass filter (201) connected between the output of the high-pass filter (101) and the second end of the white noise source module (400) to suppress the high-frequency part of the white noise signal; An output unit (300) is connected in parallel with a low-pass filter (201) to adjust the filtered white noise signal according to the input impedance requirements of the target test equipment.

2. A filter according to claim 1, characterized in that, A first resistor is also connected between the input unit (100) and the first terminal of the white noise source module (400), and the resistance value of the first resistor is less than 100Ω to serve as the source impedance of the white noise signal.

3. A filter according to claim 2, characterized in that, The high-pass filter (101) includes a second resistor and a first capacitor. The first end of the second resistor is connected to the first resistor, the second end of the second resistor is connected to the first capacitor, and the second end of the first capacitor is connected to the second end of the white noise source module (400).

4. A filter according to claim 3, characterized in that, A first inductor is also connected between the second end of the first capacitor and the second end of the white noise source module (400) to adjust the passband portion of the mid-frequency band of the white noise signal.

5. A filter according to claim 4, characterized in that, The low-pass filter (201) includes a third resistor and a second capacitor, which are connected in parallel across the two ends of the first inductor.

6. A filter according to claim 1, characterized in that, It also includes a shaping circuit (202) connected between the low-pass filter (201) and the output unit (300) to limit or respond to the mid-frequency band of the white noise signal.

7. A filter according to claim 6, characterized in that, The shaping circuit (202) includes a second inductor and a fourth resistor. The first end of the second inductor is connected to the first end of the second capacitor, the second end of the second inductor is connected to the first end of the fourth resistor, and the second end of the fourth resistor is connected to the output unit (300).

8. A filter according to claim 7, characterized in that, The molding unit (200) also includes a fifth resistor connected between the second end of the fourth resistor and the second end of the second capacitor for further control of the spectral shape.

9. A filter according to claim 8, characterized in that, The output unit (300) includes a sixth resistor, which is connected in parallel across the fifth resistor.

10. A filter according to claim 9, characterized in that, The resistance of the sixth resistor is not less than 5kΩ.

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