A circuit and method for enhancing the discrimination of a pulse signal from ambient noise

Abstract

The application discloses a circuit and method for enhancing the distinguishability of a pulse signal and environmental noise, and relates to the field of ultrasonic signal detection. The circuit comprises: an input signal inputting an input end of a filter circuit; an output end of the filter circuit being connected with an input end of a multiplier circuit; the multiplier circuit comprising a first output end and a second output end; the first output end being connected with a first input end of a comparator; the second output end being connected with a first input end of a subtractor; a second input end of the subtractor inputting an input signal; an output end of the subtractor being connected with an input end of a negative value elimination circuit; a second input end of the comparator inputting an input signal; an output end of the comparator being connected with a first input end of a selector; an output end of the negative value elimination circuit being connected with a second input end of the selector; a third input end of the selector inputting an input signal; and an output end of the selector outputting a pulse signal. The application can improve the accuracy of a pulse signal received by a receiver.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic signal detection, and in particular to a circuit and method for enhancing the distinction between pulse signals and environmental noise. Background Technology

[0002] In ultrasonic ranging applications, after the transmitter sends a pulse signal, a portion of the pulse signal is reflected by an obstacle and received by the receiver. The distance is calculated based on the transmission and reception times. If the transmitted signal encounters small obstacles, such as raindrops or snowflakes, a small portion of the pulse signal will also be returned. Additionally, noise from the receiver's own circuitry will also be introduced into the received signal. The ultrasonic receiver first passes the signal through a bandpass filter and a low-pass filter to obtain the envelope of the received signal. Subsequent circuitry then detects any raised pulses within this envelope signal; these are the signals reflected back by the obstacles. If the distance to be detected is long, i.e., the target obstacle is far away, the energy of the returned signal will be very close to noise, negatively impacting the receiver's judgment. Summary of the Invention

[0003] The purpose of this invention is to provide a circuit and method for enhancing the distinction between pulse signals and ambient noise, thereby improving the accuracy of the pulse signals received by the receiver.

[0004] To achieve the above objectives, the present invention provides the following solution:

[0005] A circuit for enhancing the distinction between pulse signals and ambient noise, the circuit comprising: a filter circuit, a multiplier circuit, a subtractor circuit, a negative value elimination circuit, a comparator circuit, and a selector circuit;

[0006] The input signals include pulse signals and ambient noise signals;

[0007] The input signal is input to the input terminal of the filter circuit; the output terminal of the filter circuit is connected to the input terminal of the multiplier circuit; the multiplier circuit includes a first output terminal and a second output terminal; the first output terminal is connected to the first input terminal of the comparator; the second output terminal is connected to the first input terminal of the subtractor; the input signal is input to the second input terminal of the subtractor; the output terminal of the subtractor is connected to the input terminal of the negative value elimination circuit; the input signal is input to the second input terminal of the comparator; the output terminal of the comparator is connected to the first input terminal of the selector; the output terminal of the negative value elimination circuit is connected to the second input terminal of the selector; the input signal is input to the third input terminal of the selector; the output terminal of the selector outputs the pulse signal.

[0008] Optionally, the filter circuit is an IIR low-pass filter circuit.

[0009] Optionally, the IIR low-pass filter circuit is a first-order IIR low-pass filter circuit.

[0010] Optionally, the multiplier circuit includes a first multiplier circuit and a second multiplier circuit;

[0011] The output terminal of the filter circuit is connected to the first input terminal of the first multiplier circuit and the first input terminal of the second multiplier circuit, respectively; the second input terminal of the first multiplier circuit is used to input the first coefficient; the second input terminals of the second multiplier circuit are all used to input the second coefficient; the output terminal of the first multiplier circuit is the first output terminal of the multiplier circuit; the output terminal of the second multiplier circuit is the second output terminal of the multiplier circuit.

[0012] Optionally, the value of the first coefficient is greater than 1 and the value of the first coefficient is less than 2.

[0013] Optionally, the value of the second coefficient is greater than 0 and the value of the second coefficient is less than 1.

[0014] A method for enhancing the distinguishability between pulse signals and ambient noise, applied to the aforementioned circuit for enhancing the distinguishability between pulse signals and ambient noise, the method comprising:

[0015] Acquire the input signal; the input signal includes a pulse signal and an ambient noise signal;

[0016] The input signal is filtered to obtain a first ambient noise value;

[0017] Multiply the first environmental noise value by the first coefficient and the second coefficient respectively to obtain the corresponding second environmental noise value and third environmental noise value;

[0018] A first comparison output signal is obtained based on the comparison result between the input signal and the third ambient noise value; wherein, when the input signal is greater than the third ambient noise value, the first comparison output signal is the input signal; when the input signal is less than or equal to the third ambient noise value, the first comparison output signal is the difference between the input signal and the second ambient noise value;

[0019] A positive signal is obtained based on the comparison result between the comparison output signal and zero; wherein, when the comparison output signal is greater than zero, the positive signal is the comparison output signal; when the comparison output signal is less than or equal to zero, the positive signal is zero.

[0020] A second comparison output signal is obtained based on the comparison result between the second ambient noise value and the input signal; wherein, when the second ambient noise value is greater than the input signal, the second comparison output signal is the second ambient noise value; when the second ambient noise value is less than or equal to the input signal, the second comparison output signal is the input signal.

[0021] The pulse signal is obtained based on the comparison result of the second comparison output signal, the positive signal, and the input signal.

[0022] Optionally, a first-order IIR low-pass filter is applied to filter the input signal; the formula for the first-order IIR low-pass filter is:

[0023] y(n)=M / N*x(n)+(NM) / N*y(n-1);

[0024] Where y(n) represents the output of the nth cycle, y(n-1) represents the output of the (n-1)th cycle, x(n) represents the input of the nth cycle, and M and N are the configuration parameters.

[0025] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0026] This invention provides a circuit for enhancing the distinction between pulse signals and ambient noise, primarily applied in ultrasonic signal detection. This invention enhances the signal while suppressing ambient noise, thereby improving the ability to distinguish the signal from ambient noise. The invention uses an IIR filter to filter the envelope signal of the mixed noise and pulse signal to obtain a first ambient noise value. This first ambient noise value is then multiplied by a first coefficient to obtain a second ambient noise value. The envelope signal is compared with the second ambient noise value. If the envelope signal is greater than the second ambient noise value, the envelope signal is output; otherwise, the difference between the envelope signal and a third ambient noise value is output. The third ambient noise value is obtained by multiplying the first ambient noise value by a second coefficient. This invention increases the difference between the pulse signal and the ambient noise signal in the envelope signal, thus enabling better detection of the pulse signal from the envelope signal. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1This is a block diagram of the circuit structure for enhancing the distinction between pulse signals and ambient noise according to the present invention.

[0029] Figure 2 This is a flowchart of the method for enhancing the distinction between pulse signals and environmental noise according to the present invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] The purpose of this invention is to provide a circuit and method for enhancing the distinction between pulse signals and ambient noise, thereby improving the accuracy of the pulse signals received by the receiver.

[0032] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] Example 1

[0034] like Figure 1 As shown, the present invention provides a circuit for enhancing the distinction between pulse signals and environmental noise. The circuit includes: a filter circuit, a multiplier circuit, a subtractor circuit, a negative value elimination circuit, a comparator circuit, and a selector circuit.

[0035] The input signals include pulse signals and ambient noise signals.

[0036] The input signal is input to the input terminal of the filter circuit; the output terminal of the filter circuit is connected to the input terminal of the multiplier circuit; the multiplier circuit includes a first output terminal and a second output terminal; the first output terminal is connected to the first input terminal of the comparator; the second output terminal is connected to the first input terminal of the subtractor; the input signal is input to the second input terminal of the subtractor; the output terminal of the subtractor is connected to the input terminal of the negative value elimination circuit; the input signal is input to the second input terminal of the comparator; the output terminal of the comparator is connected to the first input terminal of the selector; the output terminal of the negative value elimination circuit is connected to the second input terminal of the selector; the input signal is input to the third input terminal of the selector; the output terminal of the selector outputs the pulse signal.

[0037] The filter circuit is an IIR low-pass filter circuit.

[0038] Furthermore, the IIR low-pass filter circuit is a first-order IIR low-pass filter circuit.

[0039] In one specific implementation, the multiplier circuit includes a first multiplier circuit and a second multiplier circuit.

[0040] The output terminal of the filter circuit is connected to the first input terminal of the first multiplier circuit and the first input terminal of the second multiplier circuit, respectively; the second input terminal of the first multiplier circuit is used to input the first coefficient; the second input terminals of the second multiplier circuit are all used to input the second coefficient; the output terminal of the first multiplier circuit is the first output terminal of the multiplier circuit; the output terminal of the second multiplier circuit is the second output terminal of the multiplier circuit.

[0041] Specifically, the value of the first coefficient is greater than 1 and the value of the first coefficient is less than 2.

[0042] Furthermore, the value of the second coefficient is greater than 0 and the value of the second coefficient is less than 1.

[0043] In practical applications, a circuit that enhances the distinction between pulse signals and ambient noise includes an IIR low-pass filter, two multipliers, a subtractor, a negative value elimination circuit, a comparator, and a selector.

[0044] The input signal is an envelope signal containing pulse signals and environmental noise; the envelope signal is the input signal in this invention. After passing through an IIR low-pass filter, the envelope signal yields a relatively stable environmental noise floor signal that can track environmental changes in real time, referred to as the first environmental noise value. Multiplying the first environmental noise value by a first coefficient yields the second environmental noise value. Multiplying the first environmental noise value by a second coefficient yields the third environmental noise value. The envelope signal and the third environmental noise value are compared. If the envelope signal is greater than the third environmental noise value, the envelope signal is output; otherwise, the difference between the envelope signal and the third environmental noise value is output. Since the difference calculation may result in a negative value, and since the envelope signal is always positive, a negative value cancellation circuit is used to convert negative values ​​to 0 to avoid encountering negative values ​​in subsequent processing. Therefore, in this invention, if the input is negative, the output after passing through the negative value cancellation circuit is 0; that is, the negative value cancellation circuit is a circuit that converts negative values ​​to 0.

[0045] The first and second coefficients mentioned above need to be adjusted according to the design requirements. The value of the first coefficient is generally between 1 and 2, and the value of the second coefficient is generally a number greater than 0 and less than or equal to 1.

[0046] If the envelope signal is greater than or equal to the second ambient noise value, then the current signal is a pulse signal; conversely, if the envelope signal is less than the second ambient noise value, then the current signal is ambient noise. The difference between the envelope signal and the second ambient noise value reflects the suppression effect on ambient noise, i.e., the amplitude is reduced. The selector selects the output based on the comparison result. Specifically, when the envelope signal is greater than or equal to the second ambient noise value, the selector module outputs the envelope signal; when the envelope signal is less than the second ambient noise value, the output of the negative value clipping circuit is selected as the output of the selector module. This achieves the effect of not reducing the amplitude of pulse signals while simultaneously reducing the amplitude of ambient noise.

[0047] This invention can further widen the amplitude gap between pulses and noise, thereby making pulse detection in subsequent circuits easier.

[0048] Example 2

[0049] The following provides a method to enhance the distinction between pulse signals and ambient noise, applying digital logic to achieve the corresponding functions and technical effects of Embodiment 1, such as... Figure 2 As shown, the method includes:

[0050] Step S1: Acquire the input signal; the input signal includes a pulse signal and an ambient noise signal.

[0051] Step S2: Filter the input signal to obtain the first ambient noise value.

[0052] Step S3: Multiply the first environmental noise value by the first coefficient and the second coefficient respectively to obtain the corresponding second environmental noise value and third environmental noise value.

[0053] Step S4: Based on the comparison result between the input signal and the third ambient noise value, a first comparison output signal is obtained; wherein, when the input signal is greater than the third ambient noise value, the first comparison output signal is the input signal; when the input signal is less than or equal to the third ambient noise value, the first comparison output signal is the difference between the input signal and the second ambient noise value.

[0054] Step S5: Obtain a positive signal based on the comparison result between the comparison output signal and zero; wherein, when the comparison output signal is greater than zero, the positive signal is the comparison output signal; when the comparison output signal is less than or equal to zero, the positive signal is zero.

[0055] Step S6: Based on the comparison result between the second ambient noise value and the input signal, a second comparison output signal is obtained; wherein, when the second ambient noise value is greater than the input signal, the second comparison output signal is the second ambient noise value; when the second ambient noise value is less than or equal to the input signal, the second comparison output signal is the input signal.

[0056] Step S7: Obtain the pulse signal based on the comparison result of the second comparison output signal, the positive signal, and the input signal.

[0057] Specifically, a first-order IIR low-pass filter is applied to filter the input signal; the formula for the first-order IIR low-pass filter is:

[0058] y(n)=M / N*x(n)+(NM) / N*y(n-1).

[0059] Where y(n) represents the output of the nth beat, y(n-1) represents the output of the (n-1)th beat, x(n) represents the input of the nth beat, and M and N are configuration parameters. In ultrasound applications, the typical value of M is a number greater than 0 and less than N, and N is a positive integer.

[0060] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0061] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A circuit for enhancing the distinction between pulse signals and ambient noise, characterized in that, The circuit includes: a filter circuit, a multiplier circuit, a subtractor circuit, a negative value elimination circuit, a comparator circuit, and a selector circuit; The input signals include pulse signals and ambient noise signals; The input signal is input to the input terminal of the filter circuit; the output terminal of the filter circuit is connected to the input terminal of the multiplier circuit; the multiplier circuit includes a first output terminal and a second output terminal; the first output terminal is connected to the first input terminal of the comparator circuit; the second output terminal is connected to the first input terminal of the subtractor circuit; the input signal is input to the second input terminal of the subtractor circuit; the output terminal of the subtractor circuit is connected to the input terminal of the negative value elimination circuit; the input signal is input to the second input terminal of the comparator circuit; the output terminal of the comparator circuit is connected to the first input terminal of the selector circuit; the output terminal of the negative value elimination circuit is connected to the second input terminal of the selector circuit; the input signal is input to the third input terminal of the selector circuit; the output terminal of the selector circuit outputs the pulse signal. The multiplier circuit includes a first multiplier circuit and a second multiplier circuit; The output terminal of the filter circuit is connected to the first input terminal of the first multiplier circuit and the first input terminal of the second multiplier circuit, respectively; the second input terminal of the first multiplier circuit is used to input the first coefficient; the second input terminals of the second multiplier circuit are all used to input the second coefficient; the output terminal of the first multiplier circuit is the first output terminal of the multiplier circuit; the output terminal of the second multiplier circuit is the second output terminal of the multiplier circuit.

2. The circuit for enhancing the distinction between pulse signals and ambient noise according to claim 1, characterized in that, The filter circuit is an IIR low-pass filter circuit.

3. The circuit for enhancing the distinction between pulse signals and ambient noise according to claim 2, characterized in that, The IIR low-pass filter circuit is a first-order IIR low-pass filter circuit.

4. The circuit for enhancing the distinction between pulse signals and ambient noise according to claim 1, characterized in that, The value of the first coefficient is greater than 1 and the value of the first coefficient is less than 2.

5. The circuit for enhancing the distinction between pulse signals and ambient noise according to claim 1, characterized in that, The value of the second coefficient is greater than 0 and the value of the second coefficient is less than 1.

6. A method for enhancing the distinguishability between pulse signals and ambient noise, characterized in that, The method includes: Acquire the input signal; the input signal includes a pulse signal and an ambient noise signal; The input signal is filtered to obtain a first ambient noise value; The first ambient noise value is multiplied by a first coefficient and a second coefficient to obtain the corresponding second and third ambient noise values. Specifically, the multiplier circuit includes a first multiplier circuit and a second multiplier circuit. The output terminal of the filter circuit is connected to the first input terminal of the first multiplier circuit and the first input terminal of the second multiplier circuit, respectively. The second input terminal of the first multiplier circuit is used to input the first coefficient. The second input terminals of the second multiplier circuit are all used to input the second coefficient. The output terminal of the first multiplier circuit is the first output terminal of the multiplier circuit. The output terminal of the second multiplier circuit is the second output terminal of the multiplier circuit. A first comparison output signal is obtained based on the comparison result between the input signal and the third ambient noise value; wherein, when the input signal is greater than the third ambient noise value, the first comparison output signal is the input signal; when the input signal is less than or equal to the third ambient noise value, the first comparison output signal is the difference between the input signal and the third ambient noise value. A positive signal is obtained based on the comparison result between the comparison output signal and zero; wherein, when the comparison output signal is greater than zero, the positive signal is the comparison output signal; when the comparison output signal is less than or equal to zero, the positive signal is zero. A second comparison output signal is obtained based on the comparison result between the second ambient noise value and the input signal; wherein, when the second ambient noise value is greater than the input signal, the second comparison output signal is the second ambient noise value; when the second ambient noise value is less than or equal to the input signal, the second comparison output signal is the input signal. The pulse signal is obtained based on the comparison result of the second comparison output signal, the positive signal, and the input signal.

7. The method for enhancing the distinction between pulse signals and ambient noise according to claim 6, characterized in that, The input signal is filtered using a first-order IIR low-pass filter; the formula for the first-order IIR low-pass filter is: y(n)=M / N x(n)+(N-M) / N y(n-1); Where y(n) represents the output of the nth cycle, y(n-1) represents the output of the (n-1)th cycle, x(n) represents the input of the nth cycle, and M and N are the configuration parameters.

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