WO2019173962A1 - Anti-aliasing filter, related device, and anti-aliasing filter control method - Google Patents

Abstract

An anti-aliasing filter, a related device, and an anti-aliasing filter control method. The anti-aliasing filter comprises a power supply V, an adjustable resistor R₁, a capacitor C₁, an inductor L₁, an adjustable capacitor C₂, and a resistor R₂. The negative electrode of the power supply V is grounded, and the positive electrode of the power supply V is coupled to a first end of the adjustable resistor R₁; a second end of the adjustable resistor R₁is coupled to a first end of the capacitor C₁; a second end of the capacitor C₁is grounded; a first end of the inductor L₁is separately coupled to the first end of the capacitor C₁and the second end of the adjustable resistor R₁, and a second end of the inductor L₁is coupled to a first end of the adjustable capacitor C₂; a second end of the adjustable capacitor C₂ is grounded; a first end of the resistor R₂ is coupled to the first end of the adjustable capacitor C₂ and the second end of the inductor L₂, and a second end of the resistor R₂ is grounded. The present application decreases the number of components, thereby reducing costs and power consumption.

Description

Anti-aliasing filter, related device and anti-aliasing filter control method Technical field

The present application relates to the field of wireless communication technologies, and in particular, to an anti-aliasing filter, a related device, and a control method for an anti-aliasing filter.

Background technique

The receiver is an integral part of the wireless communication system. Figure 1A shows the structure of a direct sampling receiver in a wideband system. As shown in FIG. 1A, the direct sampling receiver includes a radio frequency front end (RF Frontend) circuit, an analog digital converter (ADC), and a digital baseband (DBB) circuit. The clock signals for the ADC and Digital Baseband (DBB) circuits are provided by a clock generator (CLK). The RF front-end circuit includes a Variable Gain Low Noise Amplifier (VGLNA), a Tilt Equalizer (TILT EQ) and its buffer BUF_TILT, and an anti-aliasing filter (AAF). ) and its buffer BUF_AAF.

Among them, VGLNA is used for low noise amplification of the input signal RF_IN.

The AAF can be a Low-Pass Filter (LPF) to reduce the aliasing frequency component to a negligible level in the output level to minimize aliasing. According to the Nyquist sampling theorem, the sampling frequency f _{S of the} ADC needs to be higher than twice the maximum frequency f _BW of the useful signal. Otherwise, the sampling frequency is not high enough, and the high frequency signal in the analog signal is folded to the low frequency band, which is false. The phenomenon of frequency components is called aliasing. Aliasing can cause spectral distortion and the useful signal cannot be restored correctly. In order to solve the frequency aliasing, in the RF front-end circuit before the ADC, it is necessary to use AAF to filter out frequency components higher than 1/2 sampling frequency.

TILT EQ is used to compensate the spectrum of the signal to make the output signal spectrum flatter. After the broadband signal passes through the channel, the amplitude of the low frequency component and the high frequency component may differ due to the non-ideal frequency characteristics of the channel. For example, when a wideband signal passes through a cable, the spectrum exhibits a decrease in low frequency attenuation and a high frequency attenuation. This requires the TILT EQ to generate a frequency response (or positive slope) from the low frequency to the high frequency. Compensation is made to make the output signal spectrum flatter to reduce the dynamic range of the ADC. Among them, the upward frequency response means that the response gain of the TILT EQ to the high frequency signal is greater than the response gain of the low frequency signal, and can be expressed by the formula: K(dB)=G _H -G _L >0 dB. Where K represents the difference or slope of the frequency response, G _H represents the response gain of the TILT EQ to the high frequency signal, G _L represents the response gain of the TILT EQ to the low frequency signal, and K > 0 represents the updip frequency response of the positive slope. A schematic diagram of the TILT EQ generating a positive slope up warping frequency response can be seen in Figure 1B, where f _L represents the frequency of the low frequency signal, f _H represents the frequency of the high frequency signal, and f _S represents the sampling frequency of the ADC. Correspondingly, when the input signal of the RF front end is attenuated at a low frequency and the high frequency decay is reduced, the TILT is required to generate a falling frequency response (or a negative slope, the formula is K(dB)=G _H -G _L <0dB). The spectrum is compensated to make the output signal spectrum flatter to reduce the dynamic range of the ADC. Among them, the frequency response is also the frequency response, the pointer to a system, the response of the signal of different frequencies through the output of the system.

The ADC is used to sample the analog signal and complete the discretization process to obtain the digital output signal DIG_OUT. The DBB is used for demodulating, decoding, computing, and outputting the digital output signal DIG_OUT, and finally obtains the data information Data included in the RF input signal.

Limited by the bandwidth of active devices in a low-cost complementary metal oxide semiconductor (CMOS) process, in ultra-wideband receivers, anti-aliasing filters can only use passive devices with larger area (capacitors) , inductance, etc.), large area, high cost. At the same time, in order not to affect the characteristics of the active amplifier circuit of the previous stage, a high bandwidth, low output impedance buffer BUF_AAF is usually required before the anti-aliasing filter. The power consumption of the buffer BUF_AAF is even higher than the power consumption of the amplifier itself. Similarly, TILT is also composed of larger passive components. Correspondingly, a high-power active buffer BUF_TILT is also required.

Figure 1C provides a schematic diagram of the circuit structure of a typical slope equalizer (TILT EQ). As shown in FIG. 1C, the slope equalizer includes at least one inductor L, a plurality of capacitors, and a plurality of resistors. With proper configuration, the inductor and capacitor can form a series resonator or a parallel resonator. When L and C _p2 form a parallel resonator, the low frequency is attenuated and the high frequency is upturned to form a positive slope frequency response. When L and C _p1 form a series resonator, the high frequency is attenuated and the low frequency is upturned to form a negative slope frequency response. Figure 1D provides a schematic diagram of the circuit structure of a typical anti-aliasing filter (AAF). As shown in FIG. 1D, the anti-aliasing filter requires at least one inductor L ₁ , a plurality of capacitors, and a plurality of resistors. Therefore, in the RF front-end circuit shown in FIG. 1A, both the TILT EQ and the AAF require at least one inductor, a plurality of capacitors, and a plurality of resistors. Therefore, the RF front-end circuit requires at least two inductors, a plurality of capacitors, and a plurality of resistors, resulting in a large area of the RF front-end circuit and a high cost. At the same time, since the RF front-end circuit requires two active buffers, the RF front-end circuit is caused. The power consumption is higher.

In summary, how to design an anti-aliasing filter that can simultaneously implement TILT EQ and AAF functions, thereby reducing the number of passive components (capacitors, inductors, etc.) and the number of active buffers in the RF front-end, thereby reducing the RF front-end The cost and power consumption of the circuit are technical problems that need to be solved.

Summary of the invention

The technical problem to be solved by the present application is to provide an anti-aliasing filter, a related device and an anti-aliasing filter control method, and realize the anti-aliasing filter with the functions of TILT EQ and AAF at the same time, so that less The components have more functions. Applying the anti-aliasing filter to the receiver can reduce the number of components in the receiver, reduce the need for active buffer circuits, and reduce the area and cost of the receiver. Power consumption.

In a first aspect, an embodiment of the present application provides an anti-aliasing filter, including a power supply V, an adjustable resistor R ₁ , a capacitor C ₁ , an inductor L ₁ , a tunable capacitor C _{2 ,} and a resistor R ₂ . a positive electrode coupled to negative ground, the power source V to a first end of the adjustable resistor R _1, a second end of the adjustable resistor R ₁ is coupled to a first terminal of the capacitor C _1, the capacitance C ₁ of the second terminal, the first terminal of the inductor L _1, a first end of the capacitor, respectively C ₁ and a second end coupled to the adjustable resistors R _1, the first inductor L _1, the second end coupled to the first end of the adjustable capacitor C _2, the second terminal of the adjustable capacitor C _2, a first end of the resistor R ₂ is coupled to the first adjustable capacitor C ₂ And a second end of the inductor L ₁ , the second end of the resistor R ₂ is grounded.

By implementing the embodiments of the present application, by setting a resistor with adjustable resistance and a capacitance with adjustable capacitance, the anti-aliasing filter can simultaneously have the functions of TILT EQ and AAF, and can generate a frequency response with different slopes for the signal. It is also possible to filter out frequency components above the 1/2 sampling frequency for the input signal. Therefore, the anti-aliasing filter provided by the embodiment of the present application can implement fewer functions to implement more functions than the scheme of setting two independent circuits TILT EQ and AAF in the prior art. Applying the anti-aliasing filter provided by the embodiment of the present application to the RF front-end circuit can reduce the number of passive components (capacitance, inductance, etc.) and the number of active buffers in the RF front-end, thereby reducing the cost of the RF front-end circuit. And power consumption. Applying the anti-aliasing filter provided by the embodiment of the present application to the receiver can reduce the number of components in the receiver, reduce the requirement of the active buffer circuit, and reduce the area, cost and power consumption of the receiver. . Applying the anti-aliasing filter provided by the embodiment of the present application to a communication device can reduce the cost and power consumption of the communication device.

In the embodiment of the present application, the frequency response of the anti-aliasing filter to the high-frequency signal in the useful signal when at least one of the resistance of the adjustable resistor R ₁ and the capacitance of the adjustable capacitor C ₂ changes The difference from the frequency response to the low frequency signal in the useful signal also changes. Here, the difference between the frequency response of the anti-aliasing filter to the high frequency signal in the useful signal and the frequency response of the low frequency signal in the useful signal can be understood as the slope. The slope can be expressed in K. The formula can be expressed as: K(dB)=G _H -G _L , where G _H represents the frequency response of the anti-aliasing filter to the high frequency signal, and G _L represents the frequency response of the anti-aliasing filter to the low frequency signal, K >0 indicates a positive slope and K<0 indicates a negative slope. For example, when the resistance of the adjustable resistor R ₁ is the first resistance and the capacitance of the adjustable capacitor C ₂ is the first capacitance, K=K1, when the resistance of the adjustable resistor R ₁ is the second resistance When the capacitance of the adjustable capacitor C ₂ is the second capacitance value, K=K2. Wherein, K1≠K2, the first resistance is the second resistance value and the first capacitance value is the second resistance value, or the first resistance value=the second resistance value and the first capacitance value is the second resistance value, or The first resistance value is the second resistance value and the first capacitance value is the second resistance value. Therefore, by adjusting the resistance of the adjustable resistor R ₁ and/or the capacitance of the adjustable capacitor C ₂ , it is possible to achieve a different slope of the frequency response of the anti-aliasing filter to the signal. In the embodiment of the present application, the signal to be sampled may be a wideband signal, and the anti-aliasing filter filters out the useful signal from the signal to be sampled. The high frequency signal described in the embodiment of the present application may be the highest frequency signal in the useful signal, or the second highest frequency signal in the useful signal, or the third highest frequency signal in the useful signal. This application does not limit this. The low frequency signal described in the embodiment of the present application may be the lowest frequency signal in the useful signal, the second lowest frequency signal in the useful signal, and the third lowest frequency signal in the useful signal. This is not limited.

In the embodiment of the present application, the difference between the frequency response of the high frequency signal and the frequency response of the low frequency signal may also be referred to as a slope. The difference between the frequency response of the high frequency signal and the frequency response to the low frequency signal may also be referred to as an adjustable slope or a variable slope. The frequency response characteristic can be reflected in the value of the response gain (or voltage gain) in a specific application. The frequency response of different slopes means that the difference (ie, slope) K of the response gain G _H of the high frequency signal and the response gain G _L of the low frequency signal is variable after the signal passes through the anti-aliasing filter. For example, K can be a positive slope, ie K(dB) = G _{H -} G _L > 0 dB, in which case the frequency response of the anti-aliasing filter is the up warping frequency response. K can also be a negative slope, ie K(dB) = G _{H -} G _L <0 dB, in which case the frequency response of the anti-aliasing filter is the falling frequency response. Among them, the upturn frequency response can also be called upturn frequency response, rising frequency response, rising frequency response, and the like. The falling frequency response can also be referred to as the falling frequency response.

It should be noted that the signal for which the slope can be adjusted in the embodiment of the present application may be an in-band signal. The in-band signal is the signal whose frequency is within the passband range of the anti-aliasing filter. An out-of-band signal is a signal whose frequency is higher than the passband range of the anti-aliasing filter.

In one possible design, the antialiasing filter further comprises a capacitor C _3, a first end of the capacitor C ₃ is coupled to a first end of the inductor L _1, capacitor C is coupled to the second terminal of the first inductor L _{1 3} Two ends.

In one possible design, the anti-aliasing filter described above is a low pass filter.

In one possible design, the anti-aliasing filter described above is a π-type low pass filter.

In a second aspect, the embodiment of the present application provides another anti-aliasing filter, including a power supply V, an adjustable resistor R ₁ , a capacitor C ₁ , an inductor L ₁ , an inductor L ₂ , a tunable capacitor C ₂ , and a resistor R _{2 .} and an adjustable resistor R _3, the positive power source V is coupled to a first terminal of an adjustable resistor R ₁ and a second adjustable resistor R ₁ is coupled to a first terminal of capacitor C _1, L _1, respectively, a first terminal of the inductor Coupling with the second end of the adjustable resistor R ₁ and the first end of the capacitor C ₁ , the second end of the inductor L ₁ is coupled to the first end of the adjustable capacitor C ₂ , and the first end of the resistor R ₂ is respectively coupled to the inductor The second end of L ₁ is coupled to the first end of the adjustable capacitor C ₂ , the negative terminal of the power supply V is coupled to the first end of the adjustable resistor R ₃ , and the second end of the capacitor C ₁ is coupled to the adjustable resistor R ₃ a second end, L, respectively, a first terminal of the inductor ₂ and the second end of the adjustable resistor R ₃ and capacitor C ₁ is coupled to a second end, the second end of the inductor L ₂ is coupled to a second adjustable capacitor C _2, The second end of the resistor R ₂ is coupled to the second end of the inductor L _{2 and} the second end of the adjustable capacitor C ₂ , respectively.

By implementing the embodiments of the present application, by setting a resistor with adjustable resistance and a capacitance with adjustable capacitance, the anti-aliasing filter can simultaneously have the functions of TILT EQ and AAF, and can generate a frequency response with different slopes for the signal. It is also possible to filter out frequency components above the 1/2 sampling frequency for the input signal. Therefore, the anti-aliasing filter provided by the embodiment of the present application can implement fewer functions to implement more functions than the scheme of setting two independent circuits TILT EQ and AAF in the prior art. Applying the anti-aliasing filter provided by the embodiment of the present application to the RF front-end circuit can reduce the number of passive components (capacitance, inductance, etc.) and the number of active buffers in the RF front-end, thereby reducing the cost of the RF front-end circuit. And power consumption. Applying the anti-aliasing filter provided by the embodiment of the present application to the receiver can reduce the number of components in the receiver, reduce the requirement of the active buffer circuit, and reduce the area, cost and power consumption of the receiver. . Applying the anti-aliasing filter provided by the embodiment of the present application to a communication device can reduce the cost and power consumption of the communication device.

In the embodiment of the present application, when at least one of the resistance of the adjustable resistor R ₁ , the resistance of the adjustable resistor R ₃ , and the capacitance of the adjustable capacitor C ₂ is changed, the anti-aliasing filter is useful. The difference between the frequency response of the high frequency signal in the signal and the frequency response of the low frequency signal in the useful signal also changes. For example, when the resistance of the adjustable resistor R ₁ is the first resistance value, the resistance of the adjustable resistor R ₃ is the second resistance value, and the capacitance of the adjustable capacitor C ₂ is the first capacitance value, K=K1, When the resistance of the adjustable resistor R ₁ is the third resistance value, the resistance of the adjustable resistor R ₃ is the fourth resistance value, and the capacitance of the adjustable capacitor C ₂ is the second capacitance value, K=K2. Wherein, K1≠K2, the first resistance value is the third resistance value, the second resistance value is the fourth resistance value, and the first capacitance value is the second resistance value, or the first resistance value=the third resistance value, the second The resistance value is the fourth resistance value and the first capacitance value is the second resistance value, or the first resistance value is the third resistance value, the second resistance value is the fourth resistance value, and the first capacitance value is the second resistance value, Or the first resistance value is the third resistance value, the second resistance value is the fourth resistance value, and the first capacitance value is the second resistance value, or the first resistance value=the third resistance value and the second resistance value=the first The fourth resistance value and the first capacitance value ≠ the second resistance value, or the first resistance value=the third resistance value, the second resistance value ≠the fourth resistance value, and the first capacitance value=the second resistance value, or the first The resistance value is the third resistance value, the second resistance value is the fourth resistance value, and the first capacitance value is the second resistance value. Therefore, by adjusting the resistance of the adjustable resistor R ₁ , the resistance of the adjustable resistor R ₃ , and/or the capacitance of the adjustable capacitor C ₂ , the anti-aliasing filter can be different in frequency response of the signal. The slope of.

In one possible design, the antialiasing filter further comprises a capacitor C _3, a first end of the capacitor C ₃ is coupled to a first end of the inductor L _1, capacitor C is coupled to the second terminal of the first inductor L _{1 3} Two ends.

In one possible design, the anti-aliasing filter ₄ further includes a capacitor C ₄ is coupled to a first terminal of a first terminal of the capacitor C inductor L _2, a capacitor C ₄ is coupled to the second terminal of the second inductor L ₂ Two ends.

In one possible design, the anti-aliasing filter described above is a low pass filter.

In one possible design, the anti-aliasing filter described above is a π-type low pass filter.

In a third aspect, the embodiment of the present application provides a radio frequency front end, which includes the anti-aliasing filter described in the first aspect, or the anti-aliasing filter described in the second aspect.

In a fourth aspect, an embodiment of the present application provides a receiver, where the receiver includes the radio frequency front end and an analog to digital converter described in the third aspect, and an output end of the radio frequency front end is coupled to an input of the analog to digital converter. End, the analog to digital converter is used to convert an analog signal into a digital signal. Wherein, the receiver can be, but is not limited to, a direct sampling receiver, which can be applied to, but not limited to, a broadband system.

In a fifth aspect, an embodiment of the present application provides a communication device, where the communication device includes a receiver and a processor, and the receiver is the receiver described in the foregoing fourth aspect.

Specifically, the communication device can be a set top box. The communication device can also be a terminal device, a network device, or the like.

In a sixth aspect, an embodiment of the present application provides a method for controlling an anti-aliasing filter, and the anti-aliasing filter is applied to a communication device. The method includes: the communication device determines a target slope, the communication device includes an anti-aliasing filter, and the anti-aliasing filter includes a power source V, an adjustable resistor R ₁ , a capacitor C ₁ , an inductor L ₁ , a tunable capacitor C _{2 ,} and a resistor R _2, the negative power supply V is grounded, a positive power source V is coupled to a first terminal of an adjustable resistor R ₁ is coupled to a first terminal of capacitor C _1, a second end of the adjustable resistor R _1, the second end of the capacitor C _1, ground, a first end of _an inductance L and capacitance C are coupled to a first end of _a second end of the variable resistors R ₁ and the second end of the inductor L ₁ is coupled to a first end of the adjustable capacitor C _2, The second end of the adjustable capacitor C ₂ is grounded, the first end of the resistor R ₂ is coupled to the first end of the adjustable capacitor C _{2 and} the second end of the inductor L ₁ , and the second end of the resistor R ₂ is grounded, and the slope is resistant The difference between the frequency response of the aliasing filter to the high frequency signal in the wanted signal and the frequency response of the low frequency signal in the useful signal. The communication device determines the first combined parameter corresponding to the target slope according to the preset relationship between the preset slope and the combined parameter, and the combined parameter includes the resistance of the adjustable resistor R ₁ and the capacitance of the adjustable capacitor C ₂ , and the first combined parameter may be The resistance of the resistor R ₁ is the target resistance, and the capacitance of the adjustable capacitor C ₂ in the first combined parameter is the target value. The communication device adjusts the resistance of the adjustable resistor R ₁ to the target resistance value, and adjusts the capacitance of the adjustable capacitor C ₂ to the target capacitance value.

By implementing the method described in the embodiments of the present application, an anti-aliasing filter with a slope-adjustable function can be designed and generated, and an anti-aliasing filter can be realized by setting a resistor with adjustable resistance and a capacitance with adjustable capacitance. The TILT EQ and AAF functions simultaneously provide a frequency response with different slopes for the signal, as well as filtering out frequency components above the 1/2 sampling frequency for the input signal. Therefore, the anti-aliasing filter provided by the embodiment of the present application can implement fewer functions to implement more functions than the scheme of setting two independent circuits TILT EQ and AAF in the prior art. Applying the anti-aliasing filter provided by the embodiment of the present application to the RF front-end circuit can reduce the number of passive components (capacitance, inductance, etc.) and the number of active buffers in the RF front-end, thereby reducing the cost of the RF front-end circuit. And power consumption. Applying the anti-aliasing filter provided by the embodiment of the present application to the receiver can reduce the number of components in the receiver, reduce the requirement of the active buffer circuit, and reduce the area, cost and power consumption of the receiver. . Applying the anti-aliasing filter provided by the embodiment of the present application to a communication device can reduce the cost and power consumption of the communication device.

In one possible design, the antialiasing filter further comprises a capacitor C _3, a first end of the capacitor C ₃ is coupled to a first end of the inductor L _1, capacitor C is coupled to the second terminal of the first inductor L _{1 3} Two ends.

In one possible design, the target slope is determined by the communication device based on the slope selected by the user; or the target slope is determined by the communication device based on the frequency spectrum of the received signal.

In a seventh aspect, the embodiment of the present application provides another control method for an anti-aliasing filter, which is applied to a communication device. The method includes: the communication device determines a target slope, and the set top box includes a power source V, an adjustable resistor R ₁ , a capacitor C ₁ , an inductor L ₁ , an inductor L ₂ , a tunable capacitor C ₂ , a resistor R _{2 ,} and an adjustable resistor R ₃ , and the power source V is coupled to the positive electrode of a first end of the variable resistor R _1, a second end of the adjustable resistor R ₁ is coupled to a first terminal of capacitor C _1, L _1, respectively, a first end of the inductance of the variable resistor R ₁ and a second end coupled to a first end of the capacitor C _1, the second end of the inductor L ₁ is coupled to a first end of the adjustable capacitor C _2, the first end of the resistor R _2, respectively, and the second end of the inductor L ₁ and The first end of the regulating capacitor C ₂ is coupled, the negative terminal of the power supply V is coupled to the first end of the adjustable resistor R ₃ , and the second end of the capacitor C ₁ is coupled to the second end of the adjustable resistor R ₃ , the inductor L ₂ a first end of the second, respectively the adjustable resistor R ₃ and a capacitor C coupled to _a second end, the second end of the inductor L ₂ is coupled to the second terminal of the adjustable capacitor C _2, a second resistor R ₂ is end of the inductor L, respectively the second end ₂ and a second end coupled to an adjustable capacitor C _2, the slope of anti-aliasing filter frequency response of the high frequency signal of the desired signal and the useful signal The difference in frequency response of the low-frequency signal. The communication device determines a first combined parameter corresponding to the target slope according to a preset relationship between the preset slope and the combined parameter, and the combined parameter includes a resistance of the adjustable resistor R _{1 ,} a resistance of the adjustable resistor R ₃ , and a adjustable capacitor C ₂ The capacitance value, the resistance of the adjustable resistor R ₁ in the first combined parameter is the first target resistance value, and the resistance of the adjustable resistor R ₃ in the first combined parameter is the second target resistance value, and the first combined parameter is adjustable The capacitance of capacitor C ₂ is the target capacitance. The communication device adjusts the resistance of the adjustable resistor R ₁ to the first target resistance value, adjusts the resistance value of the adjustable resistor R ₃ to the second target resistance value, and adjusts the capacitance value of the adjustable capacitor C ₂ to the target capacity. value.

By implementing the method of the embodiment of the present application, an anti-aliasing filter with a slope-adjustable function can be designed and generated, and an anti-aliasing filter can be realized by setting a resistor with adjustable resistance and a capacitance with adjustable capacitance. With TILT EQ and AAF functions, it can generate frequency response with different slopes for signals, and can filter out frequency components above 1/2 sampling frequency for input signals. Therefore, the anti-aliasing filter provided by the embodiment of the present application can implement fewer functions to implement more functions than the scheme of setting two independent circuits TILT EQ and AAF in the prior art. Applying the anti-aliasing filter provided by the embodiment of the present application to the RF front-end circuit can reduce the number of passive components (capacitance, inductance, etc.) and the number of active buffers in the RF front-end, thereby reducing the cost of the RF front-end circuit. And power consumption. Applying the anti-aliasing filter provided by the embodiment of the present application to the receiver can reduce the number of components in the receiver, reduce the requirement of the active buffer circuit, and reduce the area, cost and power consumption of the receiver. . Applying the anti-aliasing filter provided by the embodiment of the present application to a communication device can reduce the cost and power consumption of the communication device.

In one possible design, the antialiasing filter further comprises a capacitor C _3, a first end of the capacitor C ₃ is coupled to a first end of the inductor L _1, capacitor C is coupled to the second terminal of the first inductor L _{1 3} Two ends.

In one possible design, the anti-aliasing filter ₄ further includes a capacitor C ₄ is coupled to a first terminal of a first terminal of the capacitor C inductor L _2, a capacitor C ₄ is coupled to a second terminal of inductor L ₂ Two ends.

In one possible design, the target slope is determined by the communication device based on the slope selected by the user; or the target slope is determined by the communication device based on the frequency spectrum of the received signal.

In summary, by setting a resistor with adjustable resistance and a capacitor with adjustable capacitance, the anti-aliasing filter can be equipped with TILT EQ and AAF functions, which can generate different slope frequency responses to signals. Filter the frequency components above the 1/2 sampling frequency for the input signal. Therefore, the anti-aliasing filter provided by the embodiment of the present application can implement fewer functions to implement more functions than the scheme of setting two independent circuits TILT EQ and AAF in the prior art. Applying the anti-aliasing filter provided by the embodiment of the present application to the RF front-end circuit can reduce the number of passive components (capacitance, inductance, etc.) and the number of active buffers in the RF front-end, thereby reducing the cost of the RF front-end circuit. And power consumption. Applying the anti-aliasing filter provided by the embodiment of the present application to the receiver can reduce the number of components in the receiver, reduce the requirement of the active buffer circuit, and reduce the area, cost and power consumption of the receiver. . Applying the anti-aliasing filter provided by the embodiment of the present application to a communication device can reduce the cost and power consumption of the communication device.

DRAWINGS

FIG. 1A is a schematic structural diagram of a direct sampling receiver;

FIG. 1B shows a schematic diagram of a slope equalizer (TILT EQ) generating a positive slope up-orientation frequency response;

1C is a schematic diagram showing the circuit structure of a slope equalizer (TILT EQ);

FIG. 1D is a schematic diagram showing the circuit structure of an anti-aliasing filter (AAF);

2 is a schematic diagram showing frequency response characteristics of an anti-aliasing filter provided by an embodiment of the present application;

FIG. 3 shows a circuit structure of an anti-aliasing filter provided by an embodiment of the present application;

FIG. 4 shows a circuit structure of another anti-aliasing filter provided by an embodiment of the present application;

FIG. 5 shows a circuit structure of a differential form anti-aliasing filter provided by an embodiment of the present application;

FIG. 6 shows a circuit structure of another differential form anti-aliasing filter provided by an embodiment of the present application;

FIG. 7 is a schematic structural diagram of a radio frequency front end according to an embodiment of the present disclosure;

FIG. 8 is a schematic structural diagram of a receiver provided by an embodiment of the present application;

FIG. 9 is a schematic structural diagram of another receiver provided by an embodiment of the present application;

Figure 10 is a block diagram showing the structure of a π-type low-pass filter;

FIG. 11 is a diagram showing the frequency response characteristics of the anti-aliasing filter provided by the embodiment of the present application in different configurations.

detailed description

The technical solutions in the embodiments of the present application will be described below with reference to the accompanying drawings in the embodiments of the present application.

The embodiment of the present application proposes an anti-aliasing filter with adjustable inner slope, which can simultaneously implement the functions of TILT EQ and AAF, and can reduce the number of passive components (capacitance, inductance, etc.) in the RF front end and the active buffer. The number, in turn, reduces the cost and power consumption of the RF front-end circuitry. The anti-aliasing filter proposed in the embodiment of the present application can generate a frequency response with different slopes for the signal, and can also filter the frequency component of the input signal by more than 1/2 sampling frequency. Here, the frequency response of different slopes means that the difference K between the response gain G _H of the high frequency signal and the response gain G _L of the low frequency signal is variable after the signal passes through the anti-aliasing filter. For example, K may be a positive slope (K (dB) = G _{H -} G _L > 0 dB) or a negative slope (K (dB) = G _{H -} G _L < 0 dB). When K>0, it indicates the upward frequency response, or the upswing frequency response, the rising frequency response, the rising frequency response, and the like. When K<0, it indicates a falling frequency response, or a falling frequency response. Referring to FIG. 1B, a schematic diagram of the frequency response of the upturn is shown. In FIG. 1B, the abscissa is the frequency and the ordinate is the response gain, and K(dB)=G _H -G _L >0 dB in FIG. 1B.

In addition, the anti-aliasing filter provided by the embodiment of the present application further includes an out-of-band rejection, that is, a frequency equal to or higher than (f _S -f _BW ), an in-band gain (G _in ) and an out-of-band. The difference in gain (G _out ). 2 is a schematic diagram of frequency response characteristics of an anti-aliasing filter provided by an embodiment of the present application. Where f _S represents the sampling frequency of the ADC, f _BW represents the highest frequency of the wanted signal, f _in represents the frequency of the _in -band signal, and G _{in -} G _out represents the _out- of-band rejection. It should be noted that the slope adjustment described in the embodiment of the present application is mainly directed to the slope adjustment of the in-band signal.

Among them, the in-band signal refers to a signal whose frequency is within the passband range of the anti-aliasing filter. An out-of-band signal is a signal whose frequency is higher than the passband range of the anti-aliasing filter.

In the embodiment of the present application, the adjustable resistor may also be referred to as a variable resistor, and the adjustable capacitor may also be referred to as a variable capacitor.

Referring to FIG. 3, a circuit structure of an anti-aliasing filter provided by an embodiment of the present application is shown. The anti-aliasing filter 30 includes a power source V, an adjustable resistor R ₁ , a capacitor C ₁ , an inductor L ₁ , a tunable capacitor C _{2 ,} and a resistor R ₂ . The negative power supply V is grounded, a positive power source V is coupled to a first end of the adjustable resistance R is a _1, the adjustable end of the second resistor R B ₁ is coupled to a first terminal of capacitor C ₁ C, ₁ second capacitor C d grounded end, a first end of the inductance L e ₁ respectively, the first end of the capacitor C c ₁ and a second adjustable resistor R ₁ is coupled to terminal b, the second end of the inductor L ₁ is coupled to an adjustable capacitor C f ₂ g of a first end, a second end of adjustable capacitance to ground C h _2, a first end of resistor R i ₂ is coupled to a first end of the adjustable capacitor C ₂ and inductance L g f _1, respectively, the second end The second end j of the resistor R ₂ is grounded.

It should be noted that the coupling includes a direct connection or an indirect connection.

Wherein, the resistance of the adjustable resistor R ₁ is variable (or adjustable), and the capacitance of the adjustable capacitor C ₂ is variable (or adjustable). When the resistance of the adjustable resistor R ₁ changes, the difference between the frequency response of the anti-aliasing filter 30 to the high frequency signal in the useful signal and the frequency response of the low frequency signal in the useful signal also changes. Alternatively, as the capacitance of the tunable capacitor C ₂ changes, the difference between the frequency response of the anti-aliasing filter 30 to the high frequency signal in the useful signal and the frequency response of the low frequency signal in the useful signal also changes. Alternatively, when the resistance of the adjustable resistor R ₁ is different and the capacitance of the adjustable capacitor C ₂ changes, the frequency response of the anti-aliasing filter 30 to the high frequency signal in the useful signal and the low frequency signal in the useful signal The difference in frequency response also changes.

For example, the initial value of the adjustable resistor R ₁ is R0, and the initial value of the adjustable capacitor C ₂ is C0. The resistance values of the different adjustable resistors R ₁ and the capacitance of the adjustable capacitor C ₂ correspond to different slopes. When the resistance of the adjustable resistor R ₁ is adjusted to 0.2×R0, and the capacitance of the adjustable capacitor C ₂ is C0, the frequency response of the anti-aliasing filter 30 to the high frequency signal and the frequency response to the low frequency signal The value is +9dB. When the resistance of the adjustable resistor R ₁ is adjusted to 0.4×R0 and the capacitance of the adjustable capacitor C ₂ is C0, the difference between the frequency response of the anti-aliasing filter 30 to the high frequency signal and the frequency response to the low frequency signal The value is +5dB. When the resistance of the adjustable resistor R ₁ is R0 and the capacitance of the adjustable capacitor C ₂ is C0, the difference between the frequency response of the anti-aliasing filter 30 to the high frequency signal and the frequency response to the low frequency signal is 0 dB. . When the resistance of the adjustable resistor R ₁ is adjusted to 0.6×R0, and the capacitance of the adjustable capacitor C ₂ is adjusted to 3×C0, the frequency response of the anti-aliasing filter 30 to the high frequency signal and the frequency of the low frequency signal The difference in response is -5dB. When the resistance of the adjustable resistor R ₁ is adjusted to 0.4×R0, and the capacitance of the adjustable capacitor C ₂ is adjusted to 5×C0, the frequency response of the anti-aliasing filter 30 to the high frequency signal and the frequency of the low frequency signal The difference in response is -10dB, and so on. The correspondence between the resistance of the adjustable resistor R ₁ , the capacitance of the adjustable capacitor C ₂ and the difference between the frequency response of the anti-aliasing filter 30 to the high-frequency signal and the frequency response of the low-frequency signal can be seen in Table 1 below. Shown.

Table 1

Resistance of R 1 (initial value is R0)	C 2 capacitance (initial value is C0)	Frequency response (G H -G L )
0.2×R0	C0	+9dB
0.4×R0	C0	+5dB
R0	C0	0dB
0.6×R0	3×C0	-5dB
0.4×R0	5×C0	-10dB

Among them, +9dB and +5dB are positive slope frequency response, and -5dB and -10dB are negative slope frequency response.

It should be noted that Table 1 is an example of the resistance values of five groups of R ₁ and the capacitance value of C ₂ . In practical applications, the number of values of R ₁ and C ₂ may be selected in multiple combinations, and is not limited to the above. The five sets of parameters shown in Table 1 may be, for example, 6 groups, 10 groups, etc., which are not limited in this embodiment of the present application, and each combination will correspond to an in-band frequency response performance.

It should be noted that the anti-aliasing filter shown in FIG. 3 is a π-type low-pass filter, and the π-type low-pass filter may be a π-type low-pass filter synthesized according to a Butterworth or Bessel transfer function. Optionally, the anti-aliasing filter may be other structures. For example, the anti-aliasing filter provided by the embodiment of the present application may also be a π-type low-pass filter synthesized according to an Elliptic or Chebyshev II transfer function, and The difference in Figure 3 is that a capacitor C ₃ is added to the π-type low-pass filter synthesized by the Elliptic or Chebyshev II transfer function. Specifically, it can be seen in Figure 4.

FIG. 4 shows a circuit structure of another anti-aliasing filter provided by an embodiment of the present application. Anti-aliasing filter 40 to increase a capacitance C ₃ on the basis of FIG. 3, a first end of the capacitor C ₃ is coupled to the inductance L k e ₁ of a first end, a second end of the capacitor C ₃ is coupled to the inductor L _{L. 1} The second end f.

The anti-aliasing filter shown in FIG. 4 also realizes the slope-adjustable function of the anti-aliasing filter by adjusting the resistance value of the adjustable resistor R ₁ and the capacitance of the adjustable capacitor C ₂ , and the specific parameter correspondence relationship can be Refer to Table 1 above, and details are not described here.

It should be noted that the anti-aliasing filters shown in FIG. 3 and FIG. 4 are all based on a single-ended architecture. In practical applications, the structure of the single-ended anti-aliasing filter may include but is not limited to FIG. 3 . And the anti-aliasing filter structure shown in FIG.

The anti-aliasing filters shown in Figures 3 and 4 above are based on a single-ended architecture. In order to improve the anti-interference capability of the direct sampling receiver, a differential receiver structure can be used. The structure of the differential form anti-aliasing filter provided by the embodiment of the present application is as shown in FIG. 5. In FIG. 5, the anti-aliasing filter 50 includes a power supply V, an adjustable resistor R ₁ , a capacitor C ₁ , an inductor L ₁ , an inductor L ₂ , a tunable capacitor C ₂ , a resistor R _{2 ,} and an adjustable resistor R ₃ , and a power source V. the positive electrode is coupled to a first end of the adjustable resistance R is a _1, the adjustable end of the second resistor R B ₁ is coupled to a first terminal of capacitor C ₁ C, a first end of the inductance L e ₁ respectively and the adjustable resistor R the second end of the capacitor C b and c ₁ is a first terminal ₁ is coupled to a second end of the inductor L ₁ is coupled to an adjustable capacitor C f of the first end ₂ g, a first end of resistor R i _2, respectively, and the inductance The second end f of L ₁ is coupled to the first end g of the tunable capacitor C ₂ , the negative terminal of the power supply V is coupled to the first end m of the adjustable resistor R ₃ , and the second end d of the capacitor C ₁ is coupled to the adjustable the second end of resistor R ₃ n, a first end of the inductance L o ₂ respectively with the adjustable end of the second resistor R ₃ and capacitor C n d ₁ of the second terminal is coupled to a second terminal of inductor L ₂ is coupled to p to adjustable capacitor C h ₂ of the second end, the second end of the resistor R j ₂ is coupled to a second end of the inductance L p and a second end of the adjustable capacitor C ₂ h _2, respectively.

The resistance of the adjustable resistor R ₁ in FIG. 5 is half of the resistance of the adjustable resistor R ₁ in FIG. 3 , and the resistance of the adjustable resistor R ₃ in FIG. 5 is the adjustable resistor R in FIG. 3 . Half of the resistance of ₁ , that is, the resistance of the adjustable resistor R ₁ in FIG. 3 is equally distributed to the differential two paths. L the inductance value of the inductor ₁ in FIG. 5 is a half of the inductance L value in FIG. 3 the inductor _1, L the inductance value of the inductor ₂ and FIG. 5 is a half of the inductance L value in FIG. 3 the inductor _1, i.e., FIG. 3 The inductance value of the middle inductor L ₂ is equally distributed to the differential two paths.

The values of the parameters of the other components in FIG. 5 are the same as those of the single-ended structure shown in FIG. 3, and are not described herein again.

In the anti-aliasing filter shown in Fig. 5, the resistance values of the adjustable resistor R ₁ and the adjustable resistor R ₃ are adjustable, and the capacitance of the adjustable capacitor C ₂ is adjustable, when the resistance of the adjustable resistor R ₁ is The frequency response of the anti-aliasing filter 50 to the high frequency signal in the useful signal and the low frequency signal in the useful signal when at least one of the resistance of the trimming resistor R ₃ and the capacitance of the adjustable capacitor C ₂ is varied The difference in frequency response also changes.

For example, the initial value of the adjustable resistor R ₁

The initial value of the adjustable resistor R ₃ is R1, and the initial value of the second capacitor C ₂ is C0. The resistance of different adjustable resistors R ₁ , the resistance of the adjustable resistor R ₃ , and the capacitance of the adjustable capacitor C ₂ correspond to different frequency responses. When the resistance of the adjustable resistor R ₁ is adjusted to 0.2×R1, the resistance of the adjustable resistor R ₃ is adjusted to 0.2×R1, and the capacitance of the adjustable capacitor C ₂ is C0, the anti-aliasing filter 50 is high. The difference between the frequency response of the frequency signal and the frequency response to the low frequency signal is +9 dB. When the resistance of the adjustable resistor R ₁ is adjusted to 0.4×R1, the resistance of the adjustable resistor R ₃ is adjusted to 0.4×R1, and the capacitance of the adjustable capacitor C ₂ is C0, the anti-aliasing filter 50 is high. The difference between the frequency response of the frequency signal and the frequency response to the low frequency signal is +5 dB. When the resistance of the adjustable resistor R ₁ is R1, the resistance of the adjustable resistor R ₃ is R1, and the capacitance of the adjustable capacitor C ₂ is C0, the frequency response of the anti-aliasing filter 50 to the high-frequency signal is The difference in frequency response to the low frequency signal is 0 dB. When the resistance of the adjustable resistor R ₁ is adjusted to 0.6×R1, the resistance of the adjustable resistor R ₃ is adjusted to 0.6×R1, and the capacitance of the adjustable capacitor C ₂ is adjusted to 3×C0, the anti-aliasing filter The difference between the frequency response of 50 pairs of high frequency signals and the frequency response to low frequency signals is -5 dB. When the resistance of the adjustable resistor R ₁ is adjusted to 0.4×R1, the resistance of the adjustable resistor R ₃ is adjusted to 0.4×R1, and the capacitance of the adjustable capacitor C ₂ is adjusted to 5×C0, the anti-aliasing filter The difference between the frequency response of 50 pairs of high frequency signals and the frequency response to low frequency signals is -10 dB, and so on. The resistance of the adjustable resistor R ₁ , the resistance of the adjustable resistor R ₃ , the capacitance of the adjustable capacitor C ₂ and the frequency response of the anti-aliasing filter 50 to the high frequency signal and the frequency response to the low frequency signal The corresponding relationship can be seen as shown in Table 2 below.

Table 2

Among them, +9dB and +5dB are positive slope frequency response, and -5dB and -10dB are negative slope frequency response.

It should be noted that Table 2 is an example of the values of the resistance values of R ₁ , the resistance of R ₃ , and the capacitance of C ₂ . In practical applications, the numerical values of R ₁ , R ₃ and C ₂ A plurality of combinations may be selected, and are not limited to the five sets of parameters shown in Table 1 above, for example, 6 sets, 10 sets, etc., which are not limited in the embodiment of the present application, and each combination will correspond to one type of in-band. Frequency response performance.

It should be noted that the anti-aliasing filter shown in FIG. 5 is a differential π-type low-pass filter, and the differential π-type low-pass filter may be a π-type low-pass integrated according to a Butterworth or Bessel transfer function. filter. Optionally, the differential anti-aliasing filter may be other structures. For example, the differential anti-aliasing filter provided by the embodiment of the present application may also be a differential π type synthesized according to an Elliptic or Chebyshev II transfer function. The low-pass filter differs from FIG. 5 in that a capacitance C ₃ and a capacitance C ₄ are added to the differential π-type low-pass filter synthesized by the Elliptic or Chebyshev II transfer function. Specifically, it can be seen in FIG. 6.

FIG. 6 shows a circuit structure of another differential anti-aliasing filter provided by an embodiment of the present application. The differential anti-aliasing filter 60 adds a capacitor C ₃ and a capacitor C _{4 to} the first end k of the capacitor C ₃ to the first end e of the inductor L _{1 and} the second end of the capacitor C ₃ . l is coupled to a second end of the inductor L is f _1. A first end of the capacitor C q ₄ is coupled to a first end of the inductance L o _2, the capacitance C r ₄ a second terminal coupled to the second end of the inductor L is p _2.

The differential anti-aliasing filter shown in Figure 6 also achieves the slope of the anti-aliasing filter by adjusting the resistance of the adjustable resistor R ₁ , the resistance of the adjustable resistor R ₃ , and the capacitance of the tunable capacitor C ₂ . For the adjustable function, the specific parameter correspondence can refer to Table 2 above, and details are not described here.

It should be noted that the anti-aliasing filters shown in FIG. 5 and FIG. 6 are all based on a differential architecture. In practical applications, the structure of the differential anti-aliasing filter may include but is not limited to those shown in FIG. 5 and FIG. 6. Anti-aliasing filter structure.

It should be noted that the anti-aliasing filters shown in FIG. 3 to FIG. 6 are all described by taking a π-type low-pass filter as an example. In practical applications, the implementation of the anti-aliasing filter may also be Other structures or types of filters are not limited in this embodiment of the present application.

In the anti-aliasing filter shown in FIG. 3 to FIG. 6, the slope of the anti-aliasing filter is adjusted by adjusting the resistance of the resistor and the capacitance of the capacitor, so that the anti-aliasing filter is not only Only the filtering function is provided, and the frequency response (including the positive slope frequency response and the negative slope frequency response) of the different slopes can be generated for the signals, so that the anti-aliasing filter provided by the embodiment of the present application simultaneously implements the functions of the TILT EQ and the AAF.

FIG. 7 is a schematic structural diagram of a radio frequency front end provided by an embodiment of the present application. As shown in FIG. 7, the RF front end 70 includes a variable gain low noise amplifier (VGLNA) 701, a buffer 702, and an anti-aliasing filter (AAF) 703. The buffer 702 is used for circuit isolating the variable gain low noise amplifier 701 and the anti-aliasing filter 703 to avoid the circuit characteristics of the anti-aliasing filter 703 of the subsequent stage to the variable gain low noise amplifier 701 of the previous stage. Make an impact. The anti-aliasing filter 703 may be the single-ended anti-aliasing filter shown in FIG. 3 or FIG. 4, or may be the differential anti-aliasing filter shown in FIG. 5 or FIG. 6. In a specific application, the anti-aliasing filter provided in the embodiment of the present application can directly replace the TILT EQ and the AAF in the RF front end in the prior art, and simultaneously implement the in-band slope adjustment and anti-aliasing functions, thereby reducing the radio frequency. The number of passive components (capacitors, inductors, etc.) in the front end reduces the area and cost of passive components in the RF front-end circuitry. Moreover, since the TILT EQ circuit is removed, the RF front end provided by the embodiment of the present application reduces the number of active buffers compared to the prior art, thereby reducing the power consumption of the RF front end circuit.

FIG. 8 is a schematic structural diagram of a receiver provided by an embodiment of the present application. The receiver is a single-ended direct sampling receiver. As shown in FIG. 8, the RF front end circuit in the receiver 80 is a single-ended form of the RF front end shown in FIG. 7, and the RF front end includes a variable gain low noise amplifier. , buffers and anti-aliasing filters.

FIG. 9 is a schematic structural diagram of another receiver according to an embodiment of the present application. The receiver is a differential direct sampling receiver. As shown in FIG. 9, the RF front end circuit in the receiver 90 is a differential form of the RF front end shown in FIG. 7. The RF front end includes a variable gain low noise amplifier and a buffer. And anti-aliasing filters.

It should be noted that the receiver provided by the embodiment of the present application may be a direct sampling receiver, and the direct sampling receiver may be applied to, but not limited to, a broadband system.

The receiver provided by the embodiment of the present application integrates the functions of two passive modules (ie, TILT EQ and AAF), realizes slope adjustment and anti-aliasing functions, reduces the number of passive components, and utilizes less Passive devices achieve as much functionality and performance as possible.

After combining the functions of TILT EQ and AAF, the embodiment of the present application only needs one active buffer drive. Compared with the prior art scheme shown in FIG. 1A, the structure of the receiver is simplified, and at least two functional modules are reduced, so that the area and power consumption of the receiver are effectively reduced.

For the anti-aliasing filter shown in FIG. 3 or FIG. 4, the embodiment of the present application further provides a control method for the anti-aliasing filter, and the control method may include the following steps.

S101: The communication device determines a target slope, and the communication device includes the anti-aliasing filter shown in FIG. 3 or FIG.

The manner in which the communication device determines the target slope includes, but is not limited to, the following two.

method one,

The communication device receives the slope selected by the user and determines the slope selected by the user as the target slope.

Specifically, the communication device can be a set top box. When installing a set-top box digital TV in a home, after the cable is laid, the user (or staff) can first measure the cable output signal with a spectrum detector to determine the actual slope of the signal. The slope required for the anti-aliasing filter is then chosen based on the actual slope of the signal. For example, if the actual slope of the signal measured by the spectrum detector is -5 dB, then +5 dB is chosen as the slope required for the anti-aliasing filter. The communication device can set a knob that corresponds to a different slope when the rotary button is adjusted to a different scale. If the communication device does not provide a scale corresponding to the +5dB slope, the user can select the slope closest to +5dB as the target slope. After the communication device receives the slope selected by the user, the slope selected by the user is determined as the target slope.

Method 2,

The target slope is determined by the communication device based on the frequency spectrum of the received signal.

Specifically, after the set top box is powered on, the set top box automatically detects the spectrum of the input signal to obtain the actual slope of the signal. The slope required to provide the anti-aliasing filter is then selected based on the actual slope obtained. For example, if the actual slope of the signal is -5dB, then +5dB is chosen as the slope required for the anti-aliasing filter.

S102: determining a first communication device corresponding to the target slope parameter combinations according to the preset correspondence relationship between the slope of a combination of parameters, the parameters including a combination of an adjustable resistance value of the resistors R ₁ and an adjustable capacitance capacitor C _2, the first combination of parameters The resistance of the medium adjustable resistor R ₁ is the target resistance value, and the capacitance of the adjustable capacitor C ₂ in the first combined parameter is the target capacitance value.

Specifically, the preset correspondence may be the correspondence shown in Table 1 above. For example, if the target slope is +5 dB, the communication device can determine the target resistance value of 0.4×R0 by querying the above Table 1, and the first capacitance value is C0. The preset correspondence may be stored in a memory of the communication device.

S103: the communication _{device. 1} the variable resistance of the resistor is adjusted to the target R & lt resistance, and capacitance of adjustable capacitor C ₂ is adjusted to a target capacitance value.

The communication device controls the resistance of the adjustable resistor R ₁ and the capacitance of the tunable capacitor C ₂ such that the slope provided by the anti-aliasing filter is the target slope such that the frequency of the output signal is nearly flat.

For the anti-aliasing filter shown in FIG. 5 or FIG. 6, the embodiment of the present application further provides another anti-aliasing filter control method, and the control method may include the following steps.

S201: The communication device determines a target slope, and the communication device includes the anti-aliasing filter shown in FIG. 5 or FIG. 6.

For the step, reference may be made to step S101 above, and details are not described herein again.

S202: determining a first communication device corresponding to the target slope parameter combinations according to the preset correspondence relationship between the slope of a combination of parameters, the parameters including a combination of an adjustable resistance value of the resistors R _1, R the resistance of the adjustable resistance ₃ and an adjustable capacitor C The capacitance value of ₂ , the resistance of the adjustable resistor R ₁ in the first combined parameter is the first target resistance value, and the resistance value of the adjustable resistor R ₃ in the first combined parameter is the second target resistance value, in the first combined parameter The capacitance of the tunable capacitor C ₂ is the target capacitance.

Specifically, the preset correspondence may be the correspondence shown in Table 2 above. For example, if the target slope is +5 dB, the communication device can determine the first target resistance value of 0.4×R0 by querying the above table 2, the second target resistance value is 0.4×R0, and the first capacitance value is C0. The preset correspondence may be stored in a memory of the communication device.

S203: The communication device to adjust the resistance of the adjustable resistor R ₁ to the first target resistance value, the resistance of the adjustable resistor R ₃ adjusted as a second target resistance value, and the capacitance of variable capacitor C ₂ is adjusted Target value.

The communication device controls the resistance of the adjustable resistor R ₁ , the resistance of the adjustable resistor R ₃ , and the capacitance of the adjustable capacitor C ₂ such that the slope provided by the anti-aliasing filter is the target slope, so that the frequency of the output signal Nearly flat.

The function of the anti-aliasing filter described above is verified in conjunction with a specific simulation map. Assuming that the frequency band of the wanted signal is 1 GHz to 2 GHz, the sampling frequency f _S of the ADC is 5 GHz, and an anti-aliasing filter is required to simultaneously achieve in-band slope adjustment (5 of +9 dB, +5 dB, 0 dB, -5 dB, and -10 dB). The slope is an example) and the out-of-band anti-aliasing (not less than 8dB of rejection) function. The design parameters of the anti-aliasing filter can be as shown in Table 3 below.

table 3

R 1	C 1	L 1	C 3	C 2	R 2
R0=100ohm	401.2fF	4.802nH	387.4fF	C0=777fF	2000ohm

The frequency response characteristics of the anti-aliasing filter under different configurations are shown in Figure 11. The in-band slope and out-of-band rejection results are shown in Table 4. For specific applications, the register adjusts the parameter values corresponding to R1 and C2 according to the input signal condition to obtain the corresponding frequency response.

Table 4

The frequency of the high frequency signal is 2 GHz, and the frequency of the low frequency signal is 1 GHz. The difference between the frequency response G _{H of the} anti-aliasing filter for the high frequency signal and the frequency response G _L of the low frequency signal is the slope.

It can be seen from Table 4 that the anti-aliasing filter provided by the embodiment of the present application implements the in-band slope adjustment and the out-of-band suppression function.

In another embodiment of the present application, a chip is provided, the chip comprising the anti-aliasing filter provided in the previous embodiment, and/or a radio frequency front end, and/or a receiver. The chip can be connected to other hardware devices (such as a processor) via a bus or other means. The chip can be, for example, Wireless Local Area Networks (WLAN), Wireless Sensor Network (WSN), Global Positioning System (GPS), Radio Frequency Identification (RFID), Bluetooth. System, mobile communication system, mobile digital TV and other radio frequency receiving chips.

In another embodiment of the present application, a communication device is provided, the communication device comprising the anti-aliasing filter provided in the previous embodiments, and/or a radio frequency front end, and/or a receiver.

Specifically, the communication device can be a set top box.

In addition, the communication device may also be a terminal device, which may also be referred to as a user device, a mobile station, an access terminal, a subscriber unit, a subscriber station, a remote station, a remote terminal, a mobile device, a user terminal, a wireless communication device, and a user. Agent or user device, etc. The terminal device can be a station in a Wireless Local Area Networks (WLAN) (Staion, ST), which can be a cellular phone, a cordless phone, a Session Initiation Protocol (SIP) phone, and a personal digital processing (English: Personal) Digital Assistant, PDA), handheld devices with wireless communication capabilities, computing devices or other processing devices connected to wireless modems, in-vehicle devices, wearable devices, and mobile stations in future 5G networks or publicly evolved public land mobile networks (Public) Land Mobile Network, PLMN) Terminal equipment in the network, etc.

Alternatively, the communication device may also be a network device, and the network device may be an access point (AP) in the WLAN, and may be a base transceiver station (Base Transceiver Station) or a Node B (NodeB, NB). It may also be an evolved Node B (eNB) in LTE, or an in-vehicle device, a wearable device, and a next-generation Node B (gNB) in a future 5G network or a future evolution. Access network equipment in the PLMN network, etc.

The above is only the preferred embodiment of the embodiments of the present application, and the scope of the embodiments of the present application is not limited thereto. Those skilled in the art can understand all or part of the process of implementing the foregoing embodiments, and Equivalent changes made in the claims of the application examples are still within the scope of the invention.

Claims (14)

1. An anti-aliasing filter, comprising: a power source V, an adjustable resistor R ₁ , a capacitor C ₁ , an inductor L ₁ , a tunable capacitor C ₂ and a resistor R ₂ , wherein a negative pole of the power source V is grounded, coupled to the positive power source V is the adjustable resistance R ₁ of a first end, _a second end of the adjustable coupling capacitor C to the first end of the resistor R _1, the second terminal of the capacitor C _1, ground, a first end of the inductor L _1, a first end of the capacitor, respectively C ₁ and a second end coupled to the adjustable resistors R _1, the second end of the inductor L ₁ is coupled to the a first adjustable capacitance C ₂ of the terminal, the second terminal of the adjustable capacitor C _2, a first end of the resistor R ₂ is coupled to a first terminal of the adjustable capacitor C and the inductance L ₂ of _At the second end of the first terminal, the second end of the resistor R ₂ is grounded.
2. The said anti-aliasing filter of claim 1, wherein said anti-aliasing filter further includes a capacitor C _3, the first end of the capacitor C ₃ is coupled to the first terminal of the inductor L ₁ , C ₃ of the capacitor is coupled to the second end of the inductor L ₁ of the second end.
3. An anti-aliasing filter, comprising: a power supply V, an adjustable resistor R ₁ , a capacitor C ₁ , an inductor L ₁ , an inductor L ₂ , a tunable capacitor C ₂ , a resistor R _{2 ,} and an adjustable resistor R ₃ , coupling the positive power source V to a first end of the variable resistor R _1, the adjustable second end coupled to a first terminal of the capacitor C _1, resistors R _1, the inductance of L ₁ second One end is coupled to the second end of the adjustable resistor R _{1 and} the first end of the capacitor C ₁ , and the second end of the inductor L ₁ is coupled to the first end of the adjustable capacitor C ₂ a first end of the resistor R ₂ is coupled to a second end of the inductor L _{1 and} a first end of the adjustable capacitor C ₂ , and a cathode of the power source V is coupled to the adjustable resistor R _3, a first end, a second end of the capacitor C ₁ is coupled to the second end of the adjustable resistor of R _3, L ₂ a first end of said inductor, respectively, the second adjustable resistor R ₃ is end and a second end coupled to the capacitor C _1, a second end of the inductor L ₂ is coupled to the second terminal of the adjustable capacitor C _2, the second end of the resistor R _2, respectively, with the inductance L ₂ of the second end and said Coupling the second end of the capacitor C _2.
4. _3, the first terminal of the capacitor C ₃ is coupled to the first terminal of the inductor L ₁ according to claim 3, wherein said anti-aliasing filter, characterized in that said anti-aliasing filter further comprises a capacitor C the second end of the capacitor C ₃ is coupled to the second end of the inductor L _1.
5. The anti-aliasing filter according to claim 3 or 4, wherein the anti-aliasing filter further comprises a capacitor C ₄ , the first end of the capacitor C ₄ being coupled to the first of the inductor L ₂ end, a second end of the capacitor C ₄ is coupled to the second end of the inductor L _2.
6. An RF front end, comprising an anti-aliasing filter, a low noise amplifier, and a buffer, the anti-aliasing filter being according to any one of claims 1-2, or any one of claims 3-5 An anti-aliasing filter, an output of the low noise amplifier coupled to an input of the buffer, an output of the buffer coupled to an input of the anti-aliasing filter, the low noise amplifier The signal is subjected to low noise amplification, and the buffer is used for circuit isolation of the anti-aliasing filter and the low noise amplifier.
7. A receiver comprising a radio frequency front end and an analog to digital converter, the radio frequency front end being the radio frequency front end of claim 6, the output end of the radio frequency front end being coupled to an input of the analog to digital converter End, the analog to digital converter is used to convert an analog signal into a digital signal.
8. A method for controlling an anti-aliasing filter, comprising:

   The communication device determines a target slope, and the communication device includes an anti-aliasing filter including a power supply V, an adjustable resistor R ₁ , a capacitor C ₁ , an inductor L ₁ , a tunable capacitor C _{2 ,} and a resistor R _2, the negative power supply V is grounded, a positive electrode coupled to the power source V to a first end of the adjustable resistance R _1, the first adjustable resistor R ₁ is coupled to a second terminal of the capacitor C _1, At one end, the second end of the capacitor C ₁ is grounded, and the first end of the inductor L ₁ is coupled to the first end of the capacitor C _{1 and} the second end of the adjustable resistor R ₁ respectively. coupling a second end of said inductance of L ₁ to a first terminal of the adjustable capacitor C _2, the second terminal of the adjustable capacitor C _2, a first end of the resistor R ₂ is coupled to the adjustable a first end of the capacitor C _{2 and} a second end of the inductor L ₁ , the second end of the resistor R ₂ is grounded, the slope being a frequency of the high frequency signal in the useful signal of the anti-aliasing filter The difference between the response and the frequency response to the low frequency signal in the useful signal;

   Determining, by the communication device, a first combination parameter corresponding to the target slope according to a preset relationship between a preset slope and a combination parameter, where the combination parameter includes a resistance of the adjustable resistor R ₁ and the adjustable capacitor C ₂ The resistance value of the adjustable resistor R ₁ in the first combination parameter is a target resistance value, and the capacitance value of the adjustable capacitance C ₂ in the first combination parameter is a target capacitance value;

   The communication device adjusts the resistance of the adjustable resistor R ₁ to the target resistance, and adjusts the capacitance of the adjustable capacitor C ₂ to the target capacitance.
9. The method according to claim 8, wherein said anti-aliasing filter further includes a capacitor C _3, the first end of the capacitor C ₃ is coupled to the first terminal of the inductor L _1, a capacitor C ₃ is coupled to a second end of the second end of the inductor L _1.
10. The method according to claim 8 or 9, wherein the target slope is determined by the communication device according to a slope selected by a user; or the target slope is a spectrum of the communication device according to the received signal. definite.
11. A method for controlling an anti-aliasing filter, comprising:

    The communication device determines a target slope, and the set top box includes a power source V, an adjustable resistor R ₁ , a capacitor C ₁ , an inductor L ₁ , an inductor L ₂ , a tunable capacitor C ₂ , a resistor R _{2 ,} and an adjustable resistor R ₃ . V is coupled to the positive electrode of a first end of the variable resistor R _1, the adjustable second end coupled to a first terminal of the capacitor C _1, resistors R _1, L _1, a first end of said inductor, respectively, Coupling with a second end of the adjustable resistor R _{1 and} a first end of the capacitor C _{1 ,} a second end of the inductor L ₁ being coupled to a first end of the adjustable capacitor C ₂ a first end of the resistor R ₂ is coupled to a second end of the inductor L _{1 and} a first end of the adjustable capacitor C ₂ , and a cathode of the power source V is coupled to the third end of the adjustable resistor R ₃ In one end, the second end of the capacitor C ₁ is coupled to the second end of the adjustable resistor R ₃ , and the first end of the inductor L _{2 and} the second end of the adjustable resistor R ₃ are respectively a second end coupled to said capacitor C _1, a second end of the inductor L ₂ is coupled to the second terminal of the adjustable capacitor C _2, the second end of the resistor R _2, respectively, and the inductance L ₂ Second end and said Tune capacitor C ₂ is coupled to the second end, the slope of the anti-aliasing filter frequency response and the frequency difference between the low-frequency signal of the desired signal responsive to the high-frequency signal of the desired signal;

    Said communication device determining a first parameter of the composition according to the preset target slope corresponding to the slope of the correspondence between the combination of parameters, the combined resistance value of the adjustable parameter comprises the resistors R _1, R ₃ the adjustable resistor The resistance value of the adjustable capacitor C ₂ , the resistance of the adjustable resistor R ₁ in the first combination parameter is a first target resistance value, and the adjustable in the first combination parameter The resistance value of the resistor R ₃ is a second target resistance value, and the capacitance value of the adjustable capacitor C ₂ in the first combination parameter is a target capacitance value;

    The communication device adjusts the resistance of the adjustable resistor R ₁ to the first target resistance, adjusts the resistance of the adjustable resistor R ₃ to the second target resistance, and The capacitance of the adjustable capacitor C ₂ is adjusted to the target capacitance.
12. The method of claim 11, wherein said anti-aliasing filter further includes a capacitor C _3, the first end of the capacitor C ₃ is coupled to the first terminal of the inductor L _1, a capacitor C ₃ is coupled to a second end of the second end of the inductor L _1.
13. The method according to claim 11 or 12, wherein the anti-aliasing filter further comprises a capacitor C ₄ , the first end of the capacitor C ₄ being coupled to the first end of the inductor L ₂ , said second terminal of capacitor C ₄ is coupled to the second end of the inductor L _2.
14. The method according to any one of claims 11 to 13, wherein the target slope is determined by the communication device according to a slope selected by a user; or the target slope is based on the received communication device The spectrum of the signal is determined.

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