A filter order automatic adjustment device and method used in a receiver

Abstract

The present invention belongs to the field of satellite navigation technology, and specifically relates to an automatic filter order adjustment device and method used in a receiver. The present invention has the ability to actually monitor, judge and process application scenarios. When there is a large amount of out-of-band interference in the application scenario, the filter order can be automatically adjusted to a high order to achieve the ability to suppress interference or noise, thereby improving the sensitivity of the received signal; when the application scenario is ideal, the filter order can be automatically adjusted to a low order to save the overall power consumption of the filter and achieve the lowest overall power consumption of the receiver. The paths used in the normal use stage and the signal monitoring stage are independent, and the signal monitoring circuit will not affect the actual received signal of the receiver; the signal monitoring circuit does not need to work all the time and can be turned off when not needed to save the power consumption of the receiver system.

Description

Technical Field

[0001] The invention belongs to the technical field of satellite navigation, and in particular relates to a device and method for automatically adjusting the filter order applied to a receiver. Background Art

[0002] In the receiver system, filters play an important role. In the application scenario where signals within a specific frequency range need to be received, filters can filter out the required signals. At the same time, filters reduce the impact of interference and noise on the received signal by filtering out-of-band signals and noise, thereby ensuring signal quality. Based on the existing filter circuit design technology, the filter's ability to suppress out-of-band signals is mainly related to the order of the filter. A second-order filter ("biquad") includes second-order filtering performance, and the attenuation rate near its cutoff frequency is usually 40dB / Dec. In order to improve its out-of-band suppression capability, the method of increasing the overall order of the filter is usually adopted.

[0003] However, increasing the order of the filter will also bring some disadvantages. As the order increases, the circuit structure of the filter becomes more complex, which will cause the receiver system to generate additional power consumption, which is not conducive to applications in low-power scenarios. Therefore, in practical applications, it is often necessary to select the appropriate filter order based on external interference conditions.

[0004] The usual receiver structure, such as Figure 1 As shown. It mainly includes the low noise amplifier, mixer, filter, variable gain amplifier and analog-to-digital converter of the RF front end, which are used to filter, amplify and process the received RF signal after down-conversion, and hand it over to the digital baseband for processing after passing through the analog-to-digital converter. The order of the filter in the existing receiver system is mostly fixed to achieve a specific out-of-band suppression capability, but lacks the ability to actually judge and process the application scenario. When there is a large amount of out-of-band interference in the application scenario, it is hoped that the order of the filter is as high as possible to achieve the ability to suppress interference or noise, thereby improving the sensitivity of the received signal. When the application scenario is ideal, it is hoped to reduce the order of the filter to save the overall power consumption of the filter and achieve the lowest power consumption of the receiver as a whole. Summary of the invention

[0005] The purpose of the present invention is to provide a device and method for automatically adjusting the filter order used in a receiver, so as to realize the receiver system's ability to actually monitor, judge and process application scenarios, so as to solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above-mentioned purpose, the present invention provides, on the one hand, a device for automatically adjusting the filter order used in a receiver, comprising: an order adjustable filter, the filter being composed of a plurality of biquad filter circuits connected in series, each biquad filter circuit comprising at least one adjustable resistor; a monitoring bandpass filter, for receiving a signal in an interference signal frequency band in a receiver application scenario; and a digital algorithm unit, for reading the output of an analog-to-digital converter and adjusting the order of the order adjustable filter according to a preset threshold.

[0007] Preferably, the order adjustable filter is an active resistor capacitor structure, and under different configurations, the quality factor Q of each biquad filter circuit is respectively:

[0008] When configured as 2nd order, the Q of the first Biquad filter circuit is 0.707;

[0009] When configured as 4th order, the Q of the first Biquad filter circuit is 0.541, and the Q of the second Biquad filter circuit is 1.307;

[0010] When configured as 6th order, the Q of the first Biquad filter circuit is 0.518, the Q of the second Biquad filter circuit is 0.707, and the Q of the third Biquad filter circuit is 1.932;

[0011] When configured as 8th order, the Q of the first Biquad filter circuit is 0.510, the Q of the second Biquad filter circuit is 0.601, the Q of the third Biquad filter circuit is 0.9, and the Q of the fourth Biquad filter circuit is 2.563.

[0012] Preferably, the center frequency and bandwidth of the monitoring bandpass filter are configurable to monitor signals near the interference frequency band F2, wherein F2>Fo+F3dB>F1>Fo, Fo is the local oscillator signal frequency of the receiver, F3dB is the filter bandwidth, and F1 is the effective signal frequency.

[0013] Preferably, during the signal monitoring stage, the digital algorithm unit dynamically adjusts the order of the adjustable-order filter by averaging N sampling values ​​of the analog-to-digital converter output signal and comparing them with a preset energy setting threshold, where N is a preset integer greater than 1.

[0014] Preferably, the switching states between the biquad filter circuits of the adjustable-order filter can be controlled by a digital algorithm unit.

[0015] Another aspect of the present invention provides an adjustment method for a filter order automatic adjustment device applied to a receiver, comprising the following steps:

[0016] In the signal monitoring stage, a monitoring bandpass filter is used to receive the signal in the interference frequency band;

[0017] Amplify the received signal through a variable gain amplifier to a suitable input range for the analog-to-digital converter;

[0018] Convert analog signals into digital signals and analyze them by the digital algorithm unit;

[0019] According to the comparison result between the average energy value of the digital signal and the preset threshold value, the order of the adjustable order filter is automatically adjusted.

[0020] Preferably, when the digital algorithm unit starts working, it first assigns an initial value of 1 to the relevant register, then reads the analog-to-digital converter N times, where N is a preset integer greater than 1, takes the average of the N readings and compares it with a preset energy threshold.

[0021] Preferably, in the signal monitoring stage, the signal chain includes a low noise amplifier, a mixer, a monitoring bandpass filter, a variable gain amplifier, an analog-to-digital converter and a digital algorithm unit; in the normal use stage, the signal chain does not include a monitoring bandpass filter and a digital algorithm unit.

[0022] Preferably, the goal of automatic adjustment is to dynamically adjust the filter order when the interference intensity changes.

[0023] Preferably, a mechanism for switching between the normal reception phase and the signal monitoring phase is also included, allowing the receiver to perform interference monitoring periodically or on demand according to current environmental conditions.

[0024] Technical effects and advantages of the present invention: Compared with the prior art, the present invention provides a device and method for automatically adjusting the filter order applied to a receiver, which has the following advantages:

[0025] The present invention has the ability to actually monitor, judge and process application scenarios. When there is a large amount of out-of-band interference in the application scenario, the order of the filter can be automatically adjusted to a high order to achieve the ability to suppress interference or noise, thereby improving the sensitivity of the received signal; when the application scenario is ideal, the order of the filter can be automatically adjusted to a low order to save the overall power consumption of the filter and achieve the lowest power consumption of the receiver as a whole. The paths used in the normal use stage and the signal monitoring stage are independent, and the signal monitoring circuit will not affect the actual received signal of the receiver; the signal monitoring circuit does not need to work all the time and can be turned off when not needed to save the power consumption of the receiver system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of a receiver structure in the prior art;

[0027] Figure 2is a schematic diagram of the receiver structure of the present invention;

[0028] Figure 3 A circuit diagram of an adjustable-order filter according to the present invention;

[0029] Figure 4 It is the working flow chart of the digital algorithm unit of the present invention;

[0030] Figure 5 For the present invention Figure 3 The circuit diagram of the first biquad filter circuit;

[0031] Figure 6 For the present invention Figure 3 The circuit diagram of the second biquad filter circuit;

[0032] Figure 7 For the present invention Figure 3 The circuit diagram of the third biquad filter circuit;

[0033] Figure 8 For the present invention Figure 3 Circuit diagram of the fourth biquad filter circuit. DETAILED DESCRIPTION

[0034] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0035] The present invention provides a filter order automatic adjustment device applied to a receiver, such as Figure 2 As shown, it mainly includes the low-noise amplifier, mixer, filter, variable gain amplifier and analog-to-digital converter of the RF front end, which are used to filter, amplify and process the received RF signal after down-conversion, and then hand it over to the digital baseband for processing after passing through the analog-to-digital converter.

[0036] It also includes an automatic filter order adjustment system, which can automatically monitor the signal energy of the received frequency band, which is the main interference signal frequency band in the receiver application scenario.

[0037] When the signal energy of the monitored frequency band exceeds the set threshold range, it means that the interference in the actual application scenario is too strong. The filter order automatic adjustment system will automatically adjust and increase the filter order to achieve the ability to suppress interference or noise, thereby improving the sensitivity of the received signal.

[0038] When the signal energy of the monitored frequency band is less than the set threshold range, it means that the environment in the actual application scenario is relatively ideal. The filter order automatic adjustment system will automatically adjust and reduce the filter order to save the overall power consumption of the filter and achieve the lowest power consumption of the receiver as a whole.

[0039] The filter order automatic adjustment system of the embodiment of the present invention is based on a common receiver system, and mainly includes an order adjustable filter, and further includes a monitoring bandpass filter and a digital algorithm unit.

[0040] like Figure 2 As shown. The order adjustable filter is composed of a multi-stage biquad structure connected in series, and the actual biquad stage used can be adjusted according to the actual usage. The monitoring bandpass filter can configure the bandwidth to the interference signal frequency band to achieve the reception of the interference signal. The digital algorithm unit can read the output of the analog-to-digital converter and perform corresponding algorithm processing to actually configure the final order of the order adjustable filter.

[0041] The system is divided into normal use phase and signal monitoring phase:

[0042] During normal use, the signal link is as follows Figure 2 As shown by the solid arrow, the RF signal input passes through a low-noise amplifier and then is down-converted by a mixer. It then passes through a filter with an adjustable order and amplified by a variable gain amplifier at an appropriate multiple before being handed over to an analog-to-digital converter to convert the analog signal into a digital signal, and finally to a digital baseband for processing.

[0043] During normal use, the monitoring bandpass filter and the digital algorithm unit can be turned off to save the overall power consumption of the receiver.

[0044] During the signal monitoring phase, the signal link is as follows: Figure 2 As shown by the dotted arrow, the RF signal input passes through a low-noise amplifier and then is down-converted by a mixer. It then passes through a monitoring bandpass filter to receive the signal in the interference frequency band, and then passes through a variable gain amplifier to amplify the signal by an appropriate multiple and then is handed over to an analog-to-digital converter to convert the analog signal into a digital signal. The converted digital signal is then analyzed by a digital algorithm unit, and the actual order of the filter is determined by comparing it with a preset threshold.

[0045] In actual use, the normal use phase and the signal monitoring phase can adjust their respective time allocations as needed. You can choose to perform signal monitoring only once when the receiver system is powered on, and then maintain the normal use phase to achieve the optimal filter order; you can also choose to alternate between the normal use phase and the signal monitoring phase regularly to achieve the receiver system's ability to actually monitor, judge and process the application scenario.

[0046] like Figure 3 and Figure 5-Figure 8 As shown, the filter with adjustable order is composed of multiple biquad structures connected in series, and the actual number of biquad stages used can be adjusted according to actual usage. The biquad filter circuit is an electronic filter that is composed of two second-order parts connected in series to act on the signal together to realize a second-order filter with a specific frequency response.

[0047] The filter of the embodiment of the present invention is described as follows using an active resistor capacitor structure and an 8th order (4th level biquad) type. Figure 3 As shown, in the actual system, the filter can use other orders, and the structure type of the filter can also be selected according to the actual requirements of the system.

[0048] according to Figure 3 When the filter as a whole needs to be configured as the second order (1st order biquad) in the circuit shown, the corresponding switches S_BQ2, S_BQ3, and S_BQ4 of the second biquad filter circuit, the third biquad filter circuit, and the fourth biquad filter circuit are closed.

[0049] The input signal of the filter is directly output after being filtered only by the first Biquad circuit, and all circuits in the second Biquad filter circuit, the third Biquad filter circuit, and the fourth Biquad filter circuit can be turned off to reduce the overall power consumption of the filter circuit.

[0050] In order to meet the overall functional requirements of the filter, the resistor R_BQ1 of the first Biquad filter circuit needs to be adjusted to meet the quality factor Q=0.707 of the first Biquad filter circuit.

[0051] When the filter as a whole needs to be configured as 4th order (2-stage biquad), the corresponding switches S_BQ3 and S_BQ4 of the third biquad filter circuit and the fourth biquad filter circuit are closed, and the input signal of the filter is directly output after being filtered by the first biquad circuit and the second biquad circuit. All circuits in the third biquad filter circuit and the fourth biquad filter circuit can be turned off to reduce the overall power consumption of the filter circuit.

[0052] In order to meet the overall functional requirements of the filter, the resistor R_BQ1 of the first Biquad filter circuit needs to be adjusted to meet the quality factor Q=0.541 of the first Biquad filter circuit, and the resistor R_BQ2 of the second Biquad filter circuit needs to be adjusted to meet the quality factor Q=1.307 of the second Biquad filter circuit. When the filter as a whole needs to be configured as a 6th order (3-level biquad), the corresponding switch S_BQ4 of the fourth Biquad filter circuit is closed, and the input signal of the filter is directly output after being filtered by the first Biquad circuit, the second Biquad circuit and the third Biquad circuit, and all circuits in the fourth Biquad filter circuit can be turned off to reduce the overall power consumption of the filter circuit.

[0053] In order to meet the overall functional requirements of the filter, the resistor R_BQ1 of the first Biquad filter circuit needs to be adjusted to meet the quality factor Q=0.518 of the first Biquad filter circuit, the resistor R_BQ2 of the second Biquad filter circuit needs to be adjusted to meet the quality factor Q=0.707 of the second Biquad filter circuit, and the resistor R_BQ3 of the third Biquad filter circuit needs to be adjusted to meet the quality factor Q=1.932 of the third Biquad filter circuit. When the filter as a whole needs to be configured as 8th order (4-level biquad), the corresponding switches of all Biquad filter circuits are turned on, and the input signal of the filter is filtered by the first Biquad circuit, the second Biquad circuit, the third Biquad circuit and the fourth Biquad circuit before output, so as to achieve the optimal out-of-band suppression capability of the filter circuit.

[0054] In order to meet the overall functional requirements of the filter, the resistance R_BQ1 of the first Biquad filter circuit needs to be adjusted to meet the quality factor Q=0.510 of the first Biquad filter circuit, the resistance R_BQ2 of the second Biquad filter circuit needs to be adjusted to meet the quality factor Q=0.601 of the second Biquad filter circuit, the resistance R_BQ3 of the third Biquad filter circuit needs to be adjusted to meet the quality factor Q=0.9 of the third Biquad filter circuit, and the resistance R_BQ4 of the fourth Biquad filter circuit needs to be adjusted to meet the quality factor Q=2.563 of the fourth Biquad filter circuit.

[0055] The specific workflow of the digital algorithm unit is as follows: Figure 4As shown, when the digital algorithm unit system starts working, the initial value 1 is first assigned to the digital algorithm unit related register, and N is a preset integer greater than 1, which represents the number of times the analog-to-digital converter is read. When the number of readings meets the preset requirement of N, the output values ​​of the N analog-to-digital conversions are averaged. Then, the average value of the N measurements is compared with the preset energy setting threshold. If the average value of the N measurements is greater than the setting threshold, the order of the filter with adjustable order is increased; if the average value of the N measurements is less than the setting threshold, the order of the filter with adjustable order is reduced.

[0056] On the other hand, the present invention provides an adjustment method for a filter order automatic adjustment device applied to a receiver, comprising the following steps:

[0057] In the signal monitoring stage, a monitoring bandpass filter is used to receive the signal in the interference frequency band;

[0058] Amplify the received signal through a variable gain amplifier to a suitable input range for the analog-to-digital converter;

[0059] Convert analog signals into digital signals and analyze them by the digital algorithm unit;

[0060] According to the comparison result between the average energy value of the digital signal and the preset threshold value, the order of the adjustable order filter is automatically adjusted.

[0061] Furthermore, when the digital algorithm unit starts working, it first assigns an initial value of 1 to the relevant register, then reads the analog-to-digital converter N times, where N is a preset integer greater than 1, and takes an average of the N readings and compares it with a preset energy threshold.

[0062] Furthermore, in the signal monitoring stage, the signal chain includes a low noise amplifier, a mixer, a monitoring bandpass filter, a variable gain amplifier, an analog-to-digital converter and a digital algorithm unit; in the normal use stage, the signal chain does not include a monitoring bandpass filter and a digital algorithm unit.

[0063] Furthermore, the goal of automatic adjustment is to dynamically adjust the filter order when the interference intensity changes.

[0064] Preferably, the system also includes a mechanism for switching between a normal reception phase and a signal monitoring phase, allowing the receiver to perform interference monitoring periodically or on demand according to current environmental conditions.

[0065] In a specific embodiment, assuming that the effective signal frequency is F1, the filter bandwidth of the adjustable order is F3dB, the out-of-band interference signal frequency is F2, the local oscillator signal frequency of the receiver is Fo, and the frequency magnitude relationship is F2-Fo>F3dB>F1-Fo.

[0066] In the signal monitoring stage, the RF signal input passes through a low noise amplifier and is down-converted by a mixer. The effective signal frequency is down-converted to F1-Fo, and the out-of-band interference signal frequency is down-converted to F2-Fo. The center frequency of the monitoring bandpass filter can be configured as F2-Fo, and the bandwidth of the monitoring bandpass filter can be configured as (F2-Fo-F3dB) / 4. In this way, signals near the interference frequency band F2 will be received by the embodiment of the present invention, thereby realizing the monitoring of interference signals in actual application scenarios.

[0067] The signal near the interference frequency band F2 is then amplified by an appropriate multiple through a variable gain amplifier. The amplification multiple needs to be based on the input range and resolution requirements of the analog-to-digital converter to ensure that the input signal of the analog-to-digital converter is close to the full swing. In this way, the signal near the interference frequency band F2 will be received by the embodiment of the present invention and converted into a processable digital signal.

[0068] The processable digital signal will be handed over to the digital algorithm unit for processing. The specific working process of the digital algorithm unit is as follows: Figure 4 As shown, when the digital algorithm unit system starts working, the initial value 1 is first assigned to the relevant registers of the digital algorithm unit, and N is a preset integer greater than 1, which represents the number of times the analog-to-digital converter reads the value. When the number of readings meets the preset requirement of N, the output values ​​of these N analog-to-digital conversions are averaged.

[0069] Then, the average value of the N measurements is compared with the preset energy setting threshold. If the average value of the N measurements is greater than the set threshold, it means that the signal near the interference frequency band F2 is too strong, and the order of the filter with adjustable order is increased to enhance the ability to suppress interference signals. If the average value of the N measurements is less than the set threshold, the order of the filter with adjustable order is reduced to reduce the power consumption of the filter and ensure the minimum power consumption of the receiver system.

[0070] The goal of automatic adjustment is to achieve the receiver system's ability to actually monitor, judge and process application scenarios. That is, when external interference is strong, a higher filter order is required. The embodiment of the present invention can adjust and increase the filter order; when external interference is weak, a high filter order is not required. A high-order filter will increase additional circuit power consumption. The embodiment of the present invention can adjust and reduce the filter order to minimize the overall power consumption of the receiver.

[0071] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A filter order automatic adjustment device used in a receiver, characterized in that: include: An order adjustable filter, the filter is composed of a plurality of biquad filter circuits connected in series, each biquad filter circuit comprising at least one adjustable resistor; A monitoring bandpass filter is used to receive signals in the interference signal frequency band in the receiver application scenario; A digital algorithm unit, used for reading the output of the analog-to-digital converter and adjusting the order of the adjustable-order filter according to a preset threshold; Among them, in the signal monitoring stage, a monitoring bandpass filter is used to receive the signal in the interference frequency band, and the received signal is amplified to a suitable input range of the analog-to-digital converter through a variable gain amplifier. The analog signal is converted into a digital signal and analyzed by the digital algorithm unit. According to the comparison result of the average energy value of the digital signal with the preset threshold, the order of the adjustable order filter is automatically adjusted.

2. The filter order automatic adjustment device used in a receiver according to claim 1, characterized in that: The order adjustable filter is an active resistor capacitor structure, and under different configurations, the quality factor Q of each biquad filter circuit is: When configured as 2nd order, the Q of the first Biquad filter circuit is 0.707; When configured as 4th order, the Q of the first Biquad filter circuit is 0.541, and the Q of the second Biquad filter circuit is 1.307; When configured as 6th order, the Q of the first Biquad filter circuit is 0.518, the Q of the second Biquad filter circuit is 0.707, and the Q of the third Biquad filter circuit is 1.932; When configured as 8th order, the Q of the first Biquad filter circuit is 0.510, the Q of the second Biquad filter circuit is 0.601, the Q of the third Biquad filter circuit is 0.9, and the Q of the fourth Biquad filter circuit is 2.

563.

3. The filter order automatic adjustment device used in a receiver according to claim 2, characterized in that: The center frequency and bandwidth of the monitoring bandpass filter are configurable to monitor signals near the interference frequency band F2, wherein F2>Fo+F3dB>F1>Fo, Fo is the local oscillator signal frequency of the receiver, F3dB is the filter bandwidth, and F1 is the effective signal frequency.

4. The filter order automatic adjustment device used in a receiver according to claim 3, characterized in that: During the signal monitoring stage, the digital algorithm unit dynamically adjusts the order of the adjustable-order filter by averaging N sampling values ​​of the analog-to-digital converter output signal and comparing them with a preset energy setting threshold, where N is a preset integer greater than 1.

5. The filter order automatic adjustment device used in a receiver according to claim 4, characterized in that: The switching states between the biquad filter circuits of the adjustable-order filter can be controlled by a digital algorithm unit.

6. According to the filter order automatic adjustment device used in the receiver of claim 5, when the digital algorithm unit starts working, it first assigns an initial value of 1 to the relevant register, then reads the value of the analog-to-digital converter N times, N is a preset integer greater than 1, takes the average of the N readings and compares it with the preset energy threshold.

7. According to the filter order automatic adjustment device used in the receiver of claim 6, in the signal monitoring stage, the signal chain includes a low noise amplifier, a mixer, a monitoring bandpass filter, a variable gain amplifier, an analog-to-digital converter and a digital algorithm unit; in the normal use stage, the signal chain does not include the monitoring bandpass filter and the digital algorithm unit.

8. The filter order automatic adjustment device used in a receiver according to claim 7, characterized in that: The goal of automatic adjustment is to dynamically adjust the filter order when the interference intensity changes.

9. The filter order automatic adjustment device used in a receiver according to claim 8, characterized in that: It also includes a mechanism to switch between the normal reception phase and the signal monitoring phase, allowing the receiver to perform interference monitoring periodically or on demand depending on the current environmental conditions.

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