Bandwidth equalization system and method based on ADC analog bandwidth insufficiency

Abstract

The invention provides a bandwidth equalization system and method based on ADC analog bandwidth insufficiency, relates to the technical field of signal processing, and solves the problem that an existing scheme is difficult to deal with limitation of ADC analog bandwidth insufficiency. The system comprises a radio frequency antenna, a radio frequency switch, a frequency conversion channel, an ADC, a time-frequency conversion module and a bandwidth equalization module which are connected in sequence, and further comprises a control module which is connected with the radio frequency switch, the frequency conversion channel, the time-frequency conversion module and the bandwidth equalization module. And the control module is used for receiving the time-frequency data input from the time-frequency conversion module, determining an equalization factor corresponding to each discrete frequency point according to the time-frequency data, and issuing the equalization factor to the bandwidth equalization module, so that the bandwidth equalization process is carried out based on the equalization factor, and the compensation correction of the full-frequency-point amplitude response in the bandwidth range is completed. According to the invention, the channel bandwidth is expanded by adopting a digital frequency domain equalization method, the analog input bandwidth is effectively improved, and the influence of insufficient analog input bandwidth is reduced.

Description

Technical Field

[0001] The present invention relates to the field of signal processing technology, and in particular to a bandwidth equalization system and method based on insufficient ADC analog bandwidth. Background Art

[0002] With the rapid development of modern electronic information technology, the demand for observation bandwidth in high-speed signal processing systems continues to increase. In specialized applications such as radar, communications, and electronic countermeasures, to achieve real-time perception and analysis of complex electromagnetic environments, the systems require front-end signal acquisition modules to possess ultra-wideband, or even multiples of the Nyquist frequency range, instantaneous processing capabilities. However, due to limitations in semiconductor processing technology, the analog input bandwidth of current commercial analog-to-digital converters (ADCs) is insufficient to meet the requirements for direct sampling of high-frequency signals, resulting in significant amplitude-frequency response degradation in high-frequency bands.

[0003] like Figure 1 As shown in the figure, it shows the relationship between amplitude Amp and frequency, that is, the amplitude-frequency response curve. As the frequency increases, the amplitude gradually decreases; the key points in the figure are explained as follows: Required bandwidth frequency lower limit: This is the lowest frequency point required by the system; Analog bandwidth cutoff frequency: This is the maximum frequency point that the ADC can actually process; Required bandwidth frequency upper limit: This is the highest frequency point required by the system.

[0004] from Figure 1 As can be seen from the figure, the amplitude remains essentially stable between the lower limit of the required bandwidth and the analog bandwidth cutoff frequency. However, when the frequency exceeds the analog bandwidth cutoff frequency, the amplitude drops rapidly and exhibits significant attenuation compared to the ideal amplitude. This attenuation manifests itself as distortion of the signal spectral energy distribution, nonlinear amplitude distortion, and deterioration of phase noise. Such defects not only reduce the effective sensitivity of the system but also lead to critical performance issues such as excessive dual-tone test indicators and modulation signal demodulation distortion.

[0005] To address the above issues, traditional technical solutions usually adopt a compensation strategy of configuring a sample-and-hold circuit at the front end of the ADC, such as Figure 2As shown in the figure, the ability to capture high-frequency components is improved by expanding the effective sampling window of the analog signal. Although this method can partially transfer the system bandwidth requirements to the sampling and protection circuit design, it still has many limitations in engineering practice. Especially in high-reliability application scenarios such as aerospace equipment, the existing domestic sampling and protection circuits cannot meet the use standards of space-grade devices in terms of operating temperature range, radiation resistance and long-term stability, while imported devices have problems such as limited supply channels and poor batch consistency. In addition, the additional sampling and protection circuit will introduce clock feedthrough noise and harmonic distortion. Measured data shows that its spurious-free dynamic range is deteriorated to a certain extent compared to the direct sampling solution. At the same time, the increase in circuit complexity also brings about derivative contradictions such as increased power consumption and tight layout space.

[0006] Existing solutions are still limited to discrete hardware compensation. In ultra-wideband applications, technical challenges such as impedance matching between the sampling and holding circuit and the ADC, signal transmission delay compensation, and coordinated control of temperature drift are becoming increasingly prominent. Especially at high sampling rates, group delay fluctuations caused by printed circuit board parasitics further degrade signal integrity, making it impossible to meet the engineering requirements of precise phase measurement and broadband signal demodulation. Therefore, there is an urgent need to break through the technical path dependence of traditional hardware compensation and explore new signal acquisition architectures to address the system performance degradation caused by insufficient ADC analog bandwidth. Summary of the Invention

[0007] In response to the high bandwidth requirements of the system, in certain special application scenarios, the availability of domestically produced ADCs with large analog input bandwidth is extremely limited, making them unable to meet the system's usage requirements. Therefore, this paper proposes a bandwidth equalization system and method based on insufficient ADC analog bandwidth. This paper uses digital frequency-domain equalization to achieve channel bandwidth expansion. When analog bandwidth is insufficient, digital processing methods can be used to increase the analog input bandwidth and mitigate the impact of insufficient analog input bandwidth.

[0008] The present invention adopts the following technical solutions to achieve the purpose: A bandwidth equalization system based on insufficient ADC analog bandwidth includes a radio frequency antenna, a radio frequency switch, a frequency conversion channel, an ADC, a time-frequency conversion module, and a bandwidth equalization module connected in sequence, and also includes a control module, the control module being connected to the radio frequency switch, the frequency conversion channel, the time-frequency conversion module, and the bandwidth equalization module respectively; The control module is used to control the state of the RF switch and the gain of the frequency conversion channel, and is also used to receive time-frequency data input from the time-frequency conversion module, determine the equalization factor corresponding to each discrete frequency point based on the time-frequency data, and send the equalization factor to the bandwidth equalization module, so that the bandwidth equalization process is performed based on the discrete equalization factor, and complete the compensation correction of the amplitude response of all frequency points in the bandwidth range.

[0009] Preferably, a front-end module is further provided between the RF antenna and the RF switch; the RF antenna is used to receive RF signals and transmit them to the front-end module, and the front-end module is used to ensure that the system's operating noise coefficient is maintained within a preset threshold through low-noise amplification.

[0010] Preferably, the control module is used to determine and control the gain of the frequency conversion channel based on preset system dynamic indicators and sensitivity indicators; by maintaining the gain of the frequency conversion channel, the system full-bandwidth thermal noise amplitude response is greater than the preset decibel value of the quantization noise of the ADC, so that when the analog bandwidth is insufficient, the attenuated signal amplitude is also stronger than the quantization noise amplitude.

[0011] Specifically, the ADC is used to perform analog-to-digital conversion on the radio frequency signal and thermal noise passing through the ADC, and the real-time data after analog-to-digital conversion is input into the time-frequency conversion module; The time-frequency conversion module is used to implement the time-frequency conversion of the real-time data by using the FFT method, obtain the time-frequency data of the discrete spectrum after the conversion, and input the time-frequency data into the control module.

[0012] Furthermore, the control module is used to determine the equalization factor corresponding to each discrete frequency point according to the amplitude-frequency response characteristics of the ADC during the acquisition of the equalization factor.

[0013] Specifically, the control module is used to control the radio frequency switch to be in an off state during the acquisition of the equalization factor, and at this time, the acquisition input of the ADC is the full-bandwidth thermal noise of the system passing through the frequency conversion channel; The time-frequency conversion module is used to perform time-frequency conversion on the process from input to output of the system full-bandwidth thermal noise after analog-to-digital conversion by the ADC, and input the obtained time-frequency data into the control module; The control module is further configured to perform multi-frame denoising on the time-frequency data and use the result as the amplitude-frequency response characteristic of the ADC.

[0014] Preferably, the control module is further configured to perform a data normalization operation on the amplitude-frequency response characteristics of the ADC to obtain an equalization factor corresponding to each discrete frequency point.

[0015] Specifically, the control module is further configured to, after obtaining the balancing factor, send the balancing factor to the bandwidth balancing module; The output end of the bandwidth equalization module is also connected to the input end of the signal processing module. The bandwidth equalization module is used to receive the data to be equalized after the time-frequency transformation of the RF signal by the time-frequency transformation module, and based on the received equalization factor, perform amplitude compensation correction on the data to be equalized according to each discrete frequency point and input it into the signal processing module for subsequent signal processing, thereby completing the bandwidth equalization process.

[0016] The present invention also provides a bandwidth equalization method based on insufficient ADC analog bandwidth. The hardware basis of the method is the aforementioned bandwidth equalization system. The method includes an equalization factor acquisition process and an equalization working process. During the equalization factor acquisition process, the external RF signal input is stopped by turning off the RF switch. The ADC then acquires the system's full-bandwidth thermal noise after applying the frequency conversion channel gain. This is then subjected to a time-frequency transform to obtain the time-frequency data of the discrete spectrum. Multi-frame denoising is performed on this time-frequency data to generate the ADC's amplitude-frequency response characteristics at each discrete frequency point. This amplitude-frequency response characteristic is then normalized to obtain the equalization factor corresponding to each discrete frequency point. During the equalization process, the RF switch is turned on, the external RF signal is obtained and amplified through the frequency conversion channel, the amplified signal is converted by ADC, and the converted signal is converted into the data to be equalized through time-frequency transformation; the data to be equalized is amplitude compensated and corrected according to the equalization factor corresponding to each discrete frequency point. The corrected data completes the bandwidth equalization and is then used for subsequent signal processing.

[0017] Specifically, in the process of obtaining the equalization factor, the amplitude-frequency response characteristics are normalized to obtain the equalization factor corresponding to each discrete frequency point, as shown in the following formula:

[0018] During the equalization process, the data to be equalized is corrected for amplitude compensation according to the equalization factor corresponding to each discrete frequency point, as shown in the following formula:

[0019] Among various Represents discrete frequency points The corresponding equilibrium factor, Representative frequency The input time-frequency data amplitude of the system full bandwidth thermal noise, Representative frequency The amplitude of the data to be equalized, Represents the bandwidth equalization data amplitude after amplitude compensation correction.

[0020] In summary, due to the adoption of this technical solution, the beneficial effects of the present invention are as follows: This invention achieves effective bandwidth expansion through an automatic bandwidth equalization strategy. Without adding additional sample-and-hold circuits, it improves system sensitivity and expands the two-tone dynamic range. It also suppresses amplitude-frequency fluctuations within the passband, significantly improving signal distortion defects caused by limited analog bandwidth. The invention addresses the in-band unevenness of the frequency conversion channel by correcting frequency response fluctuations to an accuracy better than ±0.5dB. This eliminates the insertion loss associated with traditional discrete component compensation and ensures long-term system stability, meeting the stringent reliability and radiation resistance requirements of aerospace-grade equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention further illustrates its implementation and technical solutions in detail through the following drawings, which specifically include 6 drawings as follows: Figure 1 This is a schematic diagram of the amplitude-frequency response under the current ADC input analog bandwidth limitation; Figure 2 A schematic diagram of the structure of the sample-and-hold circuit configured for the traditional technical solution; Figure 3 Schematic diagram of the bandwidth equalization system of the present invention; Figure 4 Schematic diagram of the overall process of the bandwidth equalization method of the present invention; Figure 5 Schematic diagram of the ADC amplitude-frequency response characteristics obtained in the present invention; Figure 6 Schematic diagram of determining the equalization factor based on the ADC amplitude-frequency response characteristics in the present invention. DETAILED DESCRIPTION

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0024] Example 1 like Figure 3As shown, a bandwidth equalization system for insufficient ADC analog bandwidth is described. This embodiment incorporates time-frequency conversion and bandwidth equalization into conventional processing. The system includes an RF antenna, an RF switch, a frequency conversion channel, an ADC, a time-frequency conversion module, and a bandwidth equalization module, which are connected in sequence. The system also includes a control module, which is connected to the RF switch, the frequency conversion channel, the time-frequency conversion module, and the bandwidth equalization module.

[0025] As the main points of this embodiment, Figure 3 As shown, the control module serves as the brain of the entire system process. It is used to control the state of the RF switch and the gain of the frequency conversion channel. It is also used to receive the time-frequency data input from the time-frequency conversion module, determine the equalization factor corresponding to each discrete frequency point according to the time-frequency data, and send the equalization factor to the bandwidth equalization module. The bandwidth equalization process is performed based on the discrete equalization factor to complete the compensation correction of the amplitude response of all frequency points in the bandwidth range.

[0026] like Figure 3 As shown, this embodiment further includes a front-end module between the RF antenna and the RF switch. The RF antenna is configured to receive RF signals and transmit them to the front-end module, which uses low-noise amplification to ensure that the system's operating noise figure remains within a preset threshold. This approach improves system sensitivity, thereby protecting the system's operating noise figure.

[0027] In this embodiment, the control module is used to determine and control the gain of the frequency conversion channel based on preset system dynamic indicators and sensitivity indicators. Each indicator can be selectively configured based on the specific needs of the actual RF signal being received. This is a mature technology in the field and will not be described in detail here. In this embodiment, the gain of the frequency conversion channel is redesigned in this way. By maintaining the gain of the frequency conversion channel, the system's full-bandwidth thermal noise amplitude response is made to be at least 10dB greater than the quantization noise of the ADC. Therefore, even if the analog bandwidth is insufficient, the attenuated signal amplitude is still 10dB stronger than the quantization noise. This ensures that the system does not suffer from SNR degradation due to factors such as ADC quantization error.

[0028] In this embodiment, the ADC is used to perform analog-to-digital conversion on the radio frequency signal and thermal noise passing through the ADC, and the real-time data after analog-to-digital conversion is input into the time-frequency conversion module; The time-frequency conversion module is used to implement the time-frequency conversion of the real-time data by using the FFT method, obtain the time-frequency data of the discrete spectrum after the conversion, and input the time-frequency data into the control module.

[0029] As a preferred and key part of this embodiment, the control module is used to determine the equalization factor corresponding to each discrete frequency point according to the amplitude-frequency response characteristics of the ADC during the acquisition of the equalization factor. It first controls the RF switch to be in the off state. At this time, the acquisition input of the ADC is the full-bandwidth thermal noise of the system passing through the frequency conversion channel. Subsequently, the time-frequency conversion module performs time-frequency conversion on the process from input to output of the full-bandwidth thermal noise of the system after analog-to-digital conversion by the ADC, and inputs the obtained time-frequency data into the control module; the control module is also used to perform multi-frame denoising on the time-frequency data and use it as the amplitude-frequency response characteristics of the ADC.

[0030] After obtaining the amplitude-frequency response characteristics of the ADC, the control module can perform data normalization operations on it to obtain the equalization factors corresponding to each discrete frequency point; after obtaining the equalization factors, the equalization factors are sent to the bandwidth equalization module.

[0031] In this embodiment, Figure 3 As shown, the output end of the bandwidth equalization module is also connected to the input end of the signal processing module. The bandwidth equalization module is used to receive the data to be equalized after the time-frequency transformation of the RF signal from the time-frequency transformation module, and based on the received equalization factor, perform amplitude compensation correction on the data to be equalized according to each discrete frequency point and input it into the signal processing module for subsequent signal processing, thereby completing the bandwidth equalization process.

[0032] Example 2 Based on Example 1, this example introduces a bandwidth equalization method based on insufficient ADC analog bandwidth. The hardware basis of this method is the bandwidth equalization system in Example 1. Figure 4 As shown in FIG. , the method includes a balancing factor acquisition process and a balancing working process.

[0033] During the equalization factor acquisition process, the external RF signal input is stopped by turning off the RF switch. The ADC then acquires the system's full-bandwidth thermal noise after applying the frequency conversion channel gain. This is then subjected to a time-frequency transform to obtain the time-frequency data of the discrete spectrum. Multi-frame denoising is performed on this time-frequency data to generate the ADC's amplitude-frequency response characteristics at each discrete frequency point. This amplitude-frequency response characteristic is then normalized to obtain the equalization factor corresponding to each discrete frequency point. During the equalization process, the RF switch is turned on, the external RF signal is obtained and amplified through the frequency conversion channel, the amplified signal is converted by ADC, and the converted signal is converted into the data to be equalized through time-frequency transformation; the data to be equalized is amplitude compensated and corrected according to the equalization factor corresponding to each discrete frequency point. The corrected data completes the bandwidth equalization and is then used for subsequent signal processing.

[0034] In this embodiment, after the input of the external RF signal is stopped, the full-bandwidth thermal noise of the system collected by the ADC after the frequency conversion channel gain is Gaussian white noise. The amplitude-frequency response characteristics of the ADC can be obtained by the time-frequency response from the white noise input to the output within the full working bandwidth.

[0035] As a preferred embodiment of the present invention, after the control module receives the time-frequency data, the multi-frame denoising operation it performs needs to take into account resource overhead. In this embodiment, the statistical duration is designed to be 1024 frames. At this time, the bit width of the time-frequency data is expanded to 10 bits, and the denoising process of 1K frames of data is performed to form a stable amplitude-frequency response characteristic of the ADC at each discrete frequency point. Figure 5 The amplitude-frequency response characteristic curve shown is shown in FIG. , where the vertical axis Amp is the amplitude.

[0036] In the process of obtaining the equalization factor of this embodiment, the amplitude-frequency response characteristics are normalized to obtain the equalization factor corresponding to each discrete frequency point. Figure 6 The schematic is as follows:

[0037] Then, during the equalization process, the data to be equalized is subjected to amplitude compensation correction according to the equalization factor corresponding to each discrete frequency point, as shown in the following formula:

[0038] Among various Represents discrete frequency points The corresponding equilibrium factor, Representative frequency The input time-frequency data amplitude of the system full bandwidth thermal noise, Representative frequency The amplitude of the data to be equalized, Represents the bandwidth equalization data amplitude after amplitude compensation correction.

[0039] The effects of the system and method of the present invention in application examples are as follows: The maximum input bandwidth of a certain ADC cannot meet the working bandwidth requirements of the system. The maximum gain loss in the unsuitable working band is about 10dB. If no additional bandwidth compensation is performed, the performance outside the device simulation bandwidth range will lose a maximum of about 10dB of sensitivity and two-tone dynamics, and the system performance will be significantly reduced. When the bandwidth equalization method of the present invention is adopted, the fluctuation within the entire working bandwidth range is less than 0.5dB, which successfully improves the system performance and provides a basic guarantee for the subsequent signal processing process.

Claims

1. A bandwidth equalization system based on insufficient ADC analog bandwidth, characterized by: It includes a radio frequency antenna, a radio frequency switch, a frequency conversion channel, an ADC, a time-frequency conversion module, and a bandwidth equalization module connected in sequence, and also includes a control module, the control module is connected to the radio frequency switch, the frequency conversion channel, the time-frequency conversion module, and the bandwidth equalization module respectively; The control module is used to control the state of the RF switch and the gain of the frequency conversion channel, and is also used to receive time-frequency data input from the time-frequency conversion module, determine the equalization factor corresponding to each discrete frequency point based on the time-frequency data, and send the equalization factor to the bandwidth equalization module, so that the bandwidth equalization process is performed based on the discrete equalization factor, and complete the compensation correction of the amplitude response of all frequency points in the bandwidth range.

2. The bandwidth equalization system according to claim 1, wherein: A front-end module is also provided between the RF antenna and the RF switch; the RF antenna is used to receive RF signals and transmit them to the front-end module, and the front-end module is used to ensure that the system's operating noise coefficient is maintained within a preset threshold through low-noise amplification.

3. The bandwidth equalization system according to claim 1, wherein: The control module is used to determine and control the gain of the frequency conversion channel based on preset system dynamic indicators and sensitivity indicators; by maintaining the gain of the frequency conversion channel, the system full-bandwidth thermal noise amplitude response is greater than the preset decibel value of the quantization noise of the ADC, so that when the analog bandwidth is insufficient, the attenuated signal amplitude is also stronger than the quantization noise amplitude.

4. The bandwidth equalization system according to claim 1, wherein: The ADC is used to perform analog-to-digital conversion on the radio frequency signal and thermal noise passing through the ADC, and the real-time data after analog-to-digital conversion is input into the time-frequency conversion module; The time-frequency conversion module is used to implement the time-frequency conversion of the real-time data by using the FFT method, obtain the time-frequency data of the discrete spectrum after the conversion, and input the time-frequency data into the control module.

5. The bandwidth equalization system according to claim 1, wherein: The control module is used to determine the equalization factor corresponding to each discrete frequency point according to the amplitude-frequency response characteristics of the ADC during the acquisition of the equalization factor.

6. The bandwidth equalization system according to claim 5, characterized in that: The control module is used to control the radio frequency switch to be in an off state during the acquisition of the equalization factor, and at this time the acquisition input of the ADC is the full-bandwidth thermal noise of the system passing through the frequency conversion channel; The time-frequency conversion module is used to perform time-frequency conversion on the process from input to output of the system full-bandwidth thermal noise after analog-to-digital conversion by the ADC, and input the obtained time-frequency data into the control module; The control module is further configured to perform multi-frame denoising on the time-frequency data and use the result as the amplitude-frequency response characteristic of the ADC.

7. The bandwidth equalization system according to claim 6, wherein: The control module is further configured to perform a data normalization operation on the amplitude-frequency response characteristics of the ADC to obtain an equalization factor corresponding to each discrete frequency point.

8. The bandwidth equalization system according to claim 7, wherein: The control module is further configured to send the balancing factor to the bandwidth balancing module after obtaining the balancing factor; The output end of the bandwidth equalization module is also connected to the input end of the signal processing module. The bandwidth equalization module is used to receive the data to be equalized after the time-frequency transformation of the RF signal by the time-frequency transformation module, and based on the received equalization factor, perform amplitude compensation correction on the data to be equalized according to each discrete frequency point and input it into the signal processing module for subsequent signal processing, thereby completing the bandwidth equalization process.

9. A bandwidth equalization method based on insufficient ADC analog bandwidth, characterized by: The hardware basis of the method is the bandwidth equalization system according to any one of claims 1 to 8, and the method includes an equalization factor acquisition process and an equalization working process; During the equalization factor acquisition process, the external RF signal input is stopped by turning off the RF switch. At this time, the ADC collects the system's full-bandwidth thermal noise after frequency conversion channel gain, and performs time-frequency transformation on the system's full-bandwidth thermal noise to obtain the time-frequency data of the discrete spectrum. After multi-frame denoising of the time-frequency data, the amplitude-frequency response characteristics of the ADC at each discrete frequency point are formed; after data normalization operation is performed on the amplitude-frequency response characteristics, the equalization factors corresponding to each discrete frequency point are obtained; During the equalization process, the RF switch is turned on to obtain the external RF signal and amplify it through the frequency conversion channel. The amplified signal is converted by ADC and the converted signal is converted by time-frequency conversion to obtain the data to be equalized. The data to be equalized is amplitude compensated and corrected according to the equalization factor corresponding to each discrete frequency point. The corrected data completes bandwidth equalization and is then ready for subsequent signal processing.

10. The bandwidth equalization method according to claim 9, wherein: In the process of obtaining the equalization factor, the amplitude-frequency response characteristics are normalized to obtain the equalization factor corresponding to each discrete frequency point, as shown in the following formula: During the equalization process, the data to be equalized is corrected for amplitude compensation according to the equalization factor corresponding to each discrete frequency point, as shown in the following formula: Among various Represents discrete frequency points The corresponding equilibrium factor, Representative frequency The input time-frequency data amplitude of the system full bandwidth thermal noise, Representative frequency The amplitude of the data to be equalized, Represents the bandwidth equalization data amplitude after amplitude compensation correction.

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