A method and system for sampling a digital front-end signal

Abstract

The embodiment of the application provides a kind of sampling digital front-end signal processing method and system, comprising: obtaining the expected received digital radio frequency signal of each channel;According to the frequency of the channel of expected received digital radio frequency signal, generate digital local oscillator signal;Using digital local oscillator signal to the expected received digital radio frequency signal is quadrature mixed to be expected received digital radio frequency signal Channel down conversion to zero frequency, obtain the first in-phase / quadrature two-way baseband signal;After filtering and downsampling processing to the first in-phase / quadrature two-way baseband signal, obtain the second in-phase / quadrature two-way baseband signal;The second in-phase / quadrature two-way baseband signal is processed and whether the second in-phase / quadrature two-way baseband signal after processing is ILS-LOC signal or GLS-VDB signal is judged.Processed.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of sampling digital front-end signal processing method and system. BACKGROUND

[0002] At present, improving the localization rate of avionics equipment, realizing the independent controllable of communication navigation surveillance (CNS) key technology is an important strategic goal of developing domestic large aircraft industry in our country. However, the market of civil aviation CNS equipment is almost monopolized by foreign companies such as Honeywell, Collins of the United States and Thales of France, and the core technology is also controlled by them. Although domestic colleges and institutes have carried out some research on civil aviation radio navigation technology, there is still a big technical gap with foreign countries, and there is no formed MMR shelf product that meets the needs of civil aviation.

[0003] The working environment of airborne equipment is harsh, and there is a higher demand for environmental adaptability, and at the same time, miniaturization, light weight and low power consumption are pursued. The approach and landing phase of MMR is the flight phase with the highest safety and reliability requirements in the entire flight. In order to meet the above strict requirements, using advanced digital signal processing means instead of traditional analog circuit structure is the technical development trend of airborne MMR equipment.

[0004] Large civil aircraft usually use the multi-mode receiver (MMR) suggested by ARINC 755 "Digital Multi-Mode Receiver" standard to provide flight guidance in the approach and landing phase, which is mainly composed of instrument landing system (ILS) module, satellite landing system (GLS) module and microwave landing system (MLS) module, etc. The localizer (LOC) signal of ILS and the VHF data broadcast (VDB) signal of GLS are located in the VHF frequency band of 108-112 MHz, and the interval of each channel is 50 kHz.

[0005] In addition to the VHF band LOC and VDB channels, MMR also contains channels for processing UHF band (329.15-335.00 MHz) ILS glide path beacon (GS) signals and L-band global satellite navigation system (GNSS) signals, and the electromagnetic environment is complex. In order to avoid signal interference between them, the most effective means at present is to minimize the use of analog devices, especially analog local oscillators and mixers, and to replace them with radio frequency direct sampling and digital down conversion structure.

[0006] Most of the existing airborne VHF navigation equipment uses superheterodyne intermediate frequency sampling structure, using analog local oscillator and analog mixer. Affected by the nonlinear characteristics of analog components, especially when the equipment is aging, it is easy to cause serious local oscillator leakage, frequency deviation, and more harmonics and spurs. SUMMARY

[0007] To address the technical problems of severe local oscillator leakage, frequency deviation, and numerous harmonics and spurious emissions caused by the nonlinear characteristics of analog components in existing airborne VHF equipment during aging, this invention provides a sampling digital front-end signal processing method and system.

[0008] The embodiments of the present invention are achieved through the following technical solutions:

[0009] In a first aspect, embodiments of the present invention provide a sampling digital front-end signal processing method, comprising:

[0010] The radio frequency signals within a certain frequency range, including at least one channel, are sampled in real time and digitally processed at the sampling rate to obtain the expected received digital radio frequency signals for each channel.

[0011] A digital local oscillator signal is generated based on the frequency of the channel of the digital radio frequency signal to be received.

[0012] The expected digital radio frequency signal is quadrature-mixed with the digital local oscillator signal to downconvert the channel of the expected digital radio frequency signal to zero frequency, thereby obtaining the first in-phase / quadrature baseband signal.

[0013] After filtering and downsampling the first in-phase / quadrature baseband signals, the second in-phase / quadrature baseband signals are obtained.

[0014] The second in-phase / quadrature baseband signal is processed, and it is determined whether the processed second in-phase / quadrature baseband signal is an ILS-LOC signal or a GLS-VDB signal. If the second in-phase / quadrature baseband signal is an ILS-LOC signal, the amplitude modulation and demodulation are performed, and the spectral components are analyzed to calculate and output the modulation depth difference. If the second in-phase / quadrature baseband signal is a GLS-VDB signal, it is demodulated after matched filtering to decode and output the VDB broadcast message.

[0015] Furthermore, the radio frequency signal of the at least one channel refers to the signals on all channels within the 108-112MHz frequency band received by the multimode receiver.

[0016] Furthermore, a digital local oscillator signal is generated based on the frequency of the channel of the expected received digital radio frequency signal; including:

[0017] The digitally controlled oscillator is adjusted according to the frequency of the channel of the digital radio frequency signal to be received in order to generate a digital local oscillator signal.

[0018] Furthermore, the sampling rate f s Set as A frequency that is several times the center frequency.

[0019] In a second aspect, embodiments of the present invention provide a sampling digital front-end signal processing system, comprising:

[0020] A sampling unit is used to directly sample radio frequency signals of at least one channel in real time.

[0021] The first processing unit is used to digitize the radio frequency signal of each channel at a sampling rate to obtain the expected received digital radio frequency signal for each channel.

[0022] The generation unit is used to generate a digital local oscillator signal according to the frequency of the channel of the digital radio frequency signal to be received;

[0023] The second processing unit is used to perform quadrature mixing on the expected received digital radio frequency signal using the digital local oscillator signal to downconvert the channel of the expected received digital radio frequency signal to zero frequency, thereby obtaining the first in-phase / quadrature baseband signal.

[0024] A baseband signal generation unit is used to filter and downsample the first in-phase / quadrature baseband signals to obtain the second in-phase / quadrature baseband signals; and

[0025] The processing and judgment unit is used to process the second in-phase / quadrature baseband signals and determine whether the processed second in-phase / quadrature baseband signals are ILS-LOC signals or GLS-VDB signals. If the second in-phase / quadrature baseband signals are ILS-LOC signals, they are amplitude modulated and demodulated, and the spectral components are analyzed to calculate and output the modulation depth difference. If the second in-phase / quadrature baseband signals are GLS-VDB signals, they are demodulated after matched filtering to decode and output the VDB broadcast message.

[0026] Thirdly, embodiments of the present invention provide a sampling digital front-end signal processing system, comprising:

[0027] A bandpass filter is used to filter the radio frequency signal of each channel.

[0028] Low-noise amplifiers are used to amplify filtered signals with low noise.

[0029] An analog-to-digital converter is used to convert the low-noise amplified signal into digital signals and then digitize it at the sampling rate to obtain the expected digital radio frequency signal for each channel.

[0030] An FPGA chip is used to receive the expected digital radio frequency signal for each channel and adjust the digitally controlled oscillator according to the frequency of the channel of the expected digital radio frequency signal to generate a digital local oscillator signal.

[0031] A numerically controlled oscillator connected to an FPGA chip; used to perform quadrature mixing of the expected received digital radio frequency signal with a digital local oscillator signal to downconvert the channel of the expected received digital radio frequency signal to zero frequency, thereby obtaining the first in-phase / quadrature baseband signal.

[0032] The filtering unit is connected to the signal terminals of the in-phase baseband signal output and the quadrature baseband signal output of the numerically controlled oscillator; it is used to filter and downsample the first in-phase / quadrature baseband signals to obtain the second in-phase / quadrature baseband signal; and

[0033] The DSP chip, connected to the filtering unit, processes the second in-phase / quadrature baseband signals and determines whether the processed signals are ILS-LOC or GLS-VDB signals. If the signals are ILS-LOC, amplitude modulation and demodulation are performed to analyze the spectral components and calculate and output the modulation depth difference. If the signals are GLS-VDB, matched filtering is applied followed by demodulation to decode and output the VDB broadcast message.

[0034] Furthermore, the filtering unit includes:

[0035] The first filtering unit is connected to the signal terminal of the in-phase baseband signal output from the numerically controlled oscillator; and

[0036] The second filtering unit is connected to the signal terminal of the quadrature baseband signal output from the numerically controlled oscillator.

[0037] The DSP chip is connected to the first filter unit and the second filter unit respectively.

[0038] Both the first and second filtering units include:

[0039] A cascaded integrator comb filter is connected to the signal terminal of the in-phase / quadrature baseband signal output from a numerically controlled oscillator.

[0040] A half-band filter is connected to a cascaded integrator comb filter and a frequency-selective finite impulse response filter, respectively.

[0041] A frequency-selective finite impulse response filter is connected to a DSP chip.

[0042] Furthermore, the passband start frequency of the bandpass filter is not lower than 108MHz, the cutoff frequency is not lower than 112MHz, and the lower stopband cutoff frequency of the bandpass filter is not lower than f. s / 2, the upper stopband cutoff frequency is not higher than f s Stopband suppression of at least 60dB, f s The sampling rate.

[0043] Furthermore, the digital angular frequency of the numerically controlled oscillator is set to w. c ;

[0044]

[0045] Among them, f c f is the center frequency of the expected receiving channel. s The sampling rate.

[0046] Furthermore, the signal at the output in-phase baseband signal terminal is s. I [n], the signal at the signal terminal that outputs the quadrature baseband signal is s. Q [n];

[0047] Among them, s I [n] = cos(w) c n), s Q [n}=sin(w c n), where n represents the frequency of the digital radio frequency signal.

[0048] Compared with the prior art, the embodiments of the present invention have the following advantages and beneficial effects:

[0049] This invention discloses a sampling digital front-end signal processing method and system, which involves real-time direct sampling of at least one channel's radio frequency (RF) signal; digitizing the RF signal of each channel at a sampling rate to obtain the expected received digital RF signal for each channel; generating a digital local oscillator (LoU) signal based on the frequency of the channel of the expected received digital RF signal; using the LoU signal to perform quadrature mixing on the expected received digital RF signal to downconvert the channel of the expected received digital RF signal to zero frequency, obtaining a first in-phase / quadrature two-channel baseband signal; filtering and downsampling the first in-phase / quadrature two-channel baseband signal to obtain a second in-phase / quadrature two-channel baseband signal; and further processing the sampling digital front-end signal. The second in-phase / quadrature baseband signal is processed, and it is determined whether the processed second in-phase / quadrature baseband signal is an ILS-LOC signal or a GLS-VDB signal. If the second in-phase / quadrature baseband signal is an ILS-LOC signal, amplitude modulation and demodulation are performed, and the spectral components are analyzed to calculate and output the modulation depth difference. If the second in-phase / quadrature baseband signal is a GLS-VDB signal, it is demodulated after matched filtering to decode and output the VDB broadcast message. This solves the technical problem that existing airborne VHF equipment is prone to serious local oscillator leakage, frequency deviation, and a large number of harmonics and spurious emissions when the equipment ages due to the nonlinear characteristics of analog components. Attached Figure Description

[0050] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0051] Figure 1 This is a schematic diagram of the digital front-end signal processing method for sampling.

[0052] Figure 2 This is a schematic diagram of a sampling digital front-end signal processing system.

[0053] Figure 3 This is a schematic diagram of another sampling digital front-end signal processing system.

[0054] Figure 4 This is a schematic diagram of the signal spectrum before and after direct radio frequency sampling. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0056] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known structures, circuits, materials, or methods have not been specifically described in order to avoid obscuring the invention.

[0057] Throughout this specification, references to "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the invention. Therefore, the phrases "an embodiment," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. Moreover, those skilled in the art will understand that the illustrations provided herein are for illustrative purposes and are not necessarily drawn to scale. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0058] In the description of this invention, the terms "front", "rear", "left", "right", "up", "down", "vertical", "horizontal", "high", "low", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this invention.

[0059] Example

[0060] To address the technical problems of severe local oscillator leakage, frequency deviation, and excessive harmonics and spurious emissions caused by the nonlinear characteristics of analog components in existing airborne VHF equipment during aging, the present invention provides, in a first aspect, a sampling digital front-end signal processing method, referring to... Figure 1 As shown, it includes:

[0061] S1. Real-time direct sampling of radio frequency signals within a certain frequency range, including at least one channel, and digital processing at the sampling rate to obtain the expected received digital radio frequency signal for each channel;

[0062] Direct sampling refers to a sampling method that differs from the VHF portion of existing airborne ILS or GLS navigation equipment, which uses a superheterodyne intermediate frequency sampling structure. Instead, it uses direct radio frequency sampling.

[0063] The radio frequency signal of each channel is processed by bandpass filtering, low noise amplification, and digital-to-analog conversion, and then digitized at the sampling rate to obtain the expected received digital radio frequency signal for each channel.

[0064] S2. Generate a digital local oscillator signal based on the frequency of the channel of the digital radio frequency signal to be received;

[0065] S3. The expected digital radio frequency signal is quadrature-mixed with the digital local oscillator signal to downconvert the channel of the expected digital radio frequency signal to zero frequency, thereby obtaining the first in-phase / quadrature baseband signal.

[0066] S4. After filtering and downsampling the first in-phase / quadrature baseband signals, the second in-phase / quadrature baseband signals are obtained.

[0067] After performing low-pass filtering, downsampling, and suppression and downsampling of adjacent channels on the first in-phase / quadrature baseband signals, the second in-phase / quadrature baseband signals are obtained.

[0068] S5. Process the second in-phase / quadrature baseband signals and determine whether the processed second in-phase / quadrature baseband signals are ILS-LOC signals or GLS-VDB signals; if the second in-phase / quadrature baseband signals are ILS-LOC signals, perform amplitude modulation and demodulation and analyze the spectral components to calculate and output the modulation depth difference; if the second in-phase / quadrature baseband signals are GLS-VDB signals, perform matched filtering and demodulation to decode and output the VDB broadcast message.

[0069] The method of this invention can be implemented on an FPGA chip by programming using software radio technology.

[0070] Therefore, this embodiment of the invention directly samples the radio frequency (RF) signal of at least one channel in real time; digitizes the RF signal of each channel at a sampling rate to obtain the expected received digital RF signal for each channel; generates a digital local oscillator (LoU) signal based on the frequency of the channel of the expected received digital RF signal; uses the LoU signal to perform quadrature mixing on the expected received digital RF signal to downconvert the channel of the expected received digital RF signal to zero frequency, obtaining a first in-phase / quadrature two-channel baseband signal; filters and downsamples the first in-phase / quadrature two-channel baseband signal to obtain a second in-phase / quadrature two-channel baseband signal; and then filters and downsamples the second in-phase / quadrature two-channel baseband signal... The baseband signal is processed, and it is determined whether the processed second in-phase / quadrature baseband signal is an ILS-LOC signal or a GLS-VDB signal. If the second in-phase / quadrature baseband signal is an ILS-LOC signal, amplitude modulation and demodulation are performed, and the spectral components are analyzed to calculate and output the modulation depth difference. If the second in-phase / quadrature baseband signal is a GLS-VDB signal, it is demodulated after matched filtering to decode and output the VDB broadcast message. This solves the technical problem that existing airborne VHF equipment is prone to serious local oscillator leakage, frequency deviation, and a large number of harmonics and spurious emissions when the equipment ages due to the nonlinear characteristics of analog components.

[0071] Furthermore, the radio frequency signal of the at least one channel refers to the signals on all channels within the 108-112MHz frequency band received by the multimode receiver.

[0072] Furthermore, a digital local oscillator signal is generated based on the frequency of the channel of the expected received digital radio frequency signal; including:

[0073] The digitally controlled oscillator is adjusted according to the frequency of the channel of the digital radio frequency signal to be received in order to generate a digital local oscillator signal.

[0074] Furthermore, the sampling rate f s Set as A frequency that is several times the center frequency.

[0075] Secondly, embodiments of the present invention provide a sampling digital front-end signal processing system, with reference to... Figure 2 As shown, it includes:

[0076] A sampling unit is used to directly sample radio frequency signals of at least one channel in real time.

[0077] The first processing unit is used to digitize the radio frequency signal of each channel at a sampling rate to obtain the expected received digital radio frequency signal for each channel.

[0078] The generation unit is used to generate a digital local oscillator signal according to the frequency of the channel of the digital radio frequency signal to be received;

[0079] The second processing unit is used to perform quadrature mixing on the expected received digital radio frequency signal using the digital local oscillator signal to downconvert the channel of the expected received digital radio frequency signal to zero frequency, thereby obtaining the first in-phase / quadrature baseband signal.

[0080] A baseband signal generation unit is used to filter and downsample the first in-phase / quadrature baseband signals to obtain the second in-phase / quadrature baseband signals; and

[0081] The processing and judgment unit is used to process the second in-phase / quadrature baseband signals and determine whether the processed second in-phase / quadrature baseband signals are ILS-LOC signals or GLS-VDB signals. If the second in-phase / quadrature baseband signals are ILS-LOC signals, they are amplitude modulated and demodulated, and the spectral components are analyzed to calculate and output the modulation depth difference. If the second in-phase / quadrature baseband signals are GLS-VDB signals, they are demodulated after matched filtering to decode and output the VDB broadcast message.

[0082] Thirdly, embodiments of the present invention provide a sampling digital front-end signal processing system, with reference to... Figure 3 As shown, it includes:

[0083] A bandpass filter is used to filter the radio frequency signal of each channel.

[0084] Low-noise amplifiers are used to amplify filtered signals with low noise.

[0085] An analog-to-digital converter is used to convert the low-noise amplified signal into digital signals and then digitize it at the sampling rate to obtain the expected digital radio frequency signal for each channel.

[0086] An FPGA chip is used to receive the expected digital radio frequency signal for each channel and adjust the digitally controlled oscillator according to the frequency of the channel of the expected digital radio frequency signal to generate a digital local oscillator signal.

[0087] A numerically controlled oscillator connected to an FPGA chip; used to perform quadrature mixing of the expected received digital radio frequency signal with a digital local oscillator signal to downconvert the channel of the expected received digital radio frequency signal to zero frequency, thereby obtaining the first in-phase / quadrature baseband signal.

[0088] The filtering unit is connected to the signal terminals of the in-phase baseband signal output and the quadrature baseband signal output of the numerically controlled oscillator; it is used to filter and downsample the first in-phase / quadrature baseband signals to obtain the second in-phase / quadrature baseband signal; and

[0089] The DSP chip, connected to the filtering unit, processes the second in-phase / quadrature baseband signals and determines whether the processed signals are ILS-LOC or GLS-VDB signals. If the signals are ILS-LOC, amplitude modulation and demodulation are performed to analyze the spectral components and calculate and output the modulation depth difference. If the signals are GLS-VDB, matched filtering is applied followed by demodulation to decode and output the VDB broadcast message.

[0090] Furthermore, the filtering unit includes:

[0091] The first filtering unit is connected to the signal terminal of the in-phase baseband signal output from the numerically controlled oscillator; and

[0092] The second filtering unit is connected to the signal terminal of the quadrature baseband signal output from the numerically controlled oscillator.

[0093] The DSP chip is connected to the first filter unit and the second filter unit respectively.

[0094] Both the first and second filtering units include:

[0095] A cascaded integrator comb filter is connected to the signal terminal of the in-phase / quadrature baseband signal output from a numerically controlled oscillator.

[0096] A half-band filter is connected to a cascaded integrator comb filter and a frequency-selective finite impulse response filter, respectively.

[0097] A frequency-selective finite impulse response filter is connected to a DSP chip.

[0098] Optionally, the half-band filter includes two series-connected half-band filters, with the two ends of the two series-connected half-band filters connected to a cascaded integrator comb filter and a frequency-selective finite impulse response filter, respectively.

[0099] Furthermore, the passband start frequency of the bandpass filter is not lower than 108MHz, the cutoff frequency is not lower than 112MHz, and the lower stopband cutoff frequency of the bandpass filter is not lower than f. s / 2, the upper stopband cutoff frequency is not higher than f s Stopband suppression of at least 60dB, f s The sampling rate.

[0100] Furthermore, the digital angular frequency of the numerically controlled oscillator is set to w. c ;

[0101]

[0102] Among them, f c f is the center frequency of the expected receiving channel. s The sampling rate.

[0103] Furthermore, the signal at the output in-phase baseband signal terminal is s. I [n], the signal at the signal terminal that outputs the quadrature baseband signal is s. Q [n];

[0104] Among them, s I [n] = cos(w) c n), s Q [n] = sin(w) c n), where n represents the frequency of the digital radio frequency signal.

[0105] For example, refer to Figure 3 As shown, the system in this embodiment of the invention performs direct radio frequency sampling and processing on signals from all channels within the 108–112 MHz frequency band received by the MMR. The input radio frequency (RF) signal passes through a pre-amplifier analog bandpass filter (BPF) and a low-noise amplifier (LNA), and then through an analog-to-digital converter (ADC) at a sampling rate f. s The signals are digitized and input into the FPGA chip. Within the FPGA chip, the numerically controlled oscillator (NCO) is first adjusted according to the frequency of the expected receiving channel to generate a digital local oscillator signal. This signal is then used to perform quadrature mixing on the sampled digital radio frequency signal to downconvert the expected receiving channel to zero frequency. Next, a combination of a cascaded integrator comb filter (CIC) and a two-stage half-band filter (HB) is used to perform low-pass filtering and downsampling on the in-phase / quadrature (I / Q) baseband signals. Finally, after suppressing adjacent channels and downsampling using a frequency-selective finite impulse response filter (FIR), the lower-rate I / Q baseband signals are output to the DSP chip. The DSP chip processes the baseband signals. If it is an ILS-LOC signal, it performs amplitude modulation (AM) demodulation and analyzes the spectral components to calculate and output the modulation depth difference (DDM). If it is a GLS-VDB signal, it performs matched filtering and D8PSK demodulation to decode and output the VDB broadcast message.

[0106] Specifically, based on bandpass sampling theory, the sampling rate f s Set as The frequency, which is several times the center frequency, is used to position the receiving band near the center of the first Nyquist zone. This is done to allow for a larger transition band margin in the pre-amplifier analog bandpass filter and to reduce spectral aliasing caused by undersampling.

[0107] refer to Figure 4 As shown, after sampling, the digital angular frequency corresponding to the positive frequency band is located at... and Between -112MHz and -108MHz, the negative frequency band was shifted to the digital angular frequency. and Therefore, the passband start frequency of the preamplifier analog bandpass filter should be no less than 108MHz and the cutoff frequency no less than 112MHz; to prevent spectral aliasing caused by sampling, the lower stopband cutoff frequency of the preamplifier analog bandpass filter should be no less than f. s / 2, the upper stopband cutoff frequency is not higher than f s Stopband suppression is at least 60dB.

[0108] When the center frequency f of the expected receive channel is received from other avionics systems (such as the tuning control panel TCP or flight management system FMS) c Then, the digital angular frequency of the NCO should be set to... At this time, NCO outputs s to the in-phase branch. I [n] = cos(w) c n), output s to the orthogonal branch. Q [n] = sin(w) c n).

[0109] To facilitate the processing and demodulation of GLS-VDB signals, the design of the ADC sampling rate and the downsampling rates of each downsampling stage should ensure that the data rate input from the FPGA to the DSP is an integer multiple of 10.5 kHz. For example, the ADC sampling rate f can be set... s The baseband signal data rate is 147MHz, the cascaded integrator comb filter (CIC) has a downsampling rate of 140 times, the frequency-selective FIR has a downsampling rate of 5 times, and the final baseband signal data rate output from the FPGA to the DSP is 52.5kHz.

[0110] Therefore, the embodiments of the present invention can be applied to the reception of both ILS LOC and GLS VDB signals, which can improve the hardware and software reuse rate of MMR equipment and help reduce costs and achieve lightweight design. The sampling method of the embodiments of the present invention can reduce the design requirements of the pre-amplifier analog bandpass filter and can more effectively reduce spectral aliasing under the same BPF quality factor.

[0111] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method of sampling a digital front-end signal processing, characterized by, The method comprises the following steps: The real-time sampling multi-mode receiver receives radio frequency signals of at least one channel in the 108-112 MHz frequency band and digitizes the signals at a frequency a frequency near a multiple of the center frequency to obtain a digital radio frequency signal of the expected reception of each channel. A digitally controlled oscillator is adjusted in frequency according to the frequency of the channel of the digital radio frequency signal intended to be received to generate a digital local oscillator signal; wherein the digital angular frequency of the digitally controlled oscillator is set to ; wherein is the center frequency of the channel intended to be received, is the sampling rate; adopting a digital local oscillator signal to quadrature mix a digital radio frequency signal to be received to downconvert a frequency channel of the digital radio frequency signal to be received to zero frequency to obtain a first in-phase / quadrature two-path baseband signal; adopting a cascaded integral comb filter and a two-stage half-band filter in combination to low-pass filter and downsample the first in-phase / quadrature two-path baseband signal; and then, after suppressing adjacent channels and downsampling through a frequency-selective finite impulse response filter, obtaining a second in-phase / quadrature two-path baseband signal; processing the second in-phase / quadrature two-path baseband signal and judging whether the processed second in-phase / quadrature two-path baseband signal is an ILS-LOC signal or a GLS-VDB signal; if the second in-phase / quadrature two-path baseband signal is the ILS-LOC signal, performing amplitude modulation demodulation to analyze spectral components to calculate and output a modulation depth difference; and if the second in-phase / quadrature two-path baseband signal is the GLS-VDB signal, performing demodulation after matched filtering to decode and output a VDB broadcast text.

2. The method of claim 1, wherein the sampling digital front-end signal processing method is characterized by, The radio frequency signal of the at least one frequency channel refers to a signal on all frequency channels in a 108-112 MHz frequency band received by the multi-mode receiver.

3. A sampled digital front-end signal processing system, characterized by The method comprises the following steps: a sampling unit is configured to sample a radio frequency signal of at least one frequency channel in a 108-112 MHz frequency band received by a multi-mode receiver; The first processing unit is used for digitizing the radio frequency signal of each channel at a frequency near the center frequency to obtain a digital radio frequency signal of expected reception of each channel. The first processing unit is used for digitizing the radio frequency signal of each channel at a frequency near the center frequency to obtain a digital radio frequency signal of expected reception of each channel. The generating unit is configured to adjust a digitally controlled oscillator according to a frequency of a frequency channel of the expected received digital radio frequency signal to generate a digital local oscillator signal; wherein a digital angular frequency of the digitally controlled oscillator is set as ; wherein, is a center frequency of the expected received frequency channel, is a sampling rate; a second processing unit is configured to adopt a digital local oscillator signal to quadrature mix a digital radio frequency signal to be received to downconvert a frequency channel of the digital radio frequency signal to be received to zero frequency to obtain a first in-phase / quadrature two-path baseband signal; a baseband signal generation unit is configured to adopt a cascaded integral comb filter and a two-stage half-band filter in combination to low-pass filter and downsample the first in-phase / quadrature two-path baseband signal; and then, after suppressing adjacent channels and downsampling through a frequency-selective finite impulse response filter, obtain a second in-phase / quadrature two-path baseband signal; and a processing and judging unit is configured to process the second in-phase / quadrature two-path baseband signal and judge whether the processed second in-phase / quadrature two-path baseband signal is an ILS-LOC signal or a GLS-VDB signal; if the second in-phase / quadrature two-path baseband signal is the ILS-LOC signal, perform amplitude modulation demodulation to analyze spectral components to calculate and output a modulation depth difference; and if the second in-phase / quadrature two-path baseband signal is the GLS-VDB signal, perform demodulation after matched filtering to decode and output a VDB broadcast text.

4. A sampled digital front-end signal processing system, characterized by The method comprises the following steps: a band-pass filter is configured to filter process a radio frequency signal of at least one frequency channel in a 108-112 MHz frequency band received by a multi-mode receiver; a low-noise amplifier is configured to low-noise amplify process the filtered signal; an analog-to-digital converter for analog-to-digital conversion of the signal after low noise amplification processing to obtain a digital signal digitizing the signal around a frequency that is a multiple of the center frequency to obtain a digital radio frequency signal for each channel that is expected to be received; The FPGA chip is used for receiving the expected received digital radio frequency signal of each frequency channel, adjusting the digital controlled oscillator according to the frequency of the frequency channel of the expected received digital radio frequency signal to generate a digital local oscillation signal; wherein the digital angular frequency of the digital controlled oscillator is set as ; , wherein, is the center frequency of the expected received frequency channel, is the sampling rate; a digital controlled oscillator is connected with an FPGA chip; and is configured to adopt a digital local oscillator signal to quadrature mix a digital radio frequency signal to be received to downconvert a frequency channel of the digital radio frequency signal to be received to zero frequency to obtain a first in-phase / quadrature two-path baseband signal; The filter unit is connected with the signal end of the output in-phase baseband signal of the numerically controlled oscillator and the signal end of the output quadrature baseband signal; is used for adopting the mode of combining a cascade integral comb filter and a two-stage half-band filter to perform low-pass filtering and down-sampling on the first in-phase / quadrature two-way baseband signal; and after the adjacent channel is suppressed and down-sampled by a frequency-selective finite impulse response filter, the second in-phase / quadrature two-way baseband signal is obtained; and The DSP chip is connected with the filter unit, is used for processing the second in-phase / quadrature two-way baseband signal and judging whether the processed second in-phase / quadrature two-way baseband signal is an ILS-LOC signal or a GLS-VDB signal; if the second in-phase / quadrature two-way baseband signal is an ILS-LOC signal, after amplitude modulation demodulation, the spectrum component is analyzed to calculate and output the modulation depth difference; if the second in-phase / quadrature two-way baseband signal is a GLS-VDB signal, after matched filtering, demodulation is performed to decode and output the VDB broadcast text.

5. The sampling digital front-end signal processing system of claim 4, wherein, The filter unit comprises: The first filter unit is connected with the signal end of the output in-phase baseband signal of the numerically controlled oscillator; and The second filter unit is connected with the signal end of the output quadrature baseband signal of the numerically controlled oscillator; The DSP chip is connected with the first filter unit and the second filter unit respectively; The first filter unit and the second filter unit both comprise: The cascade integral comb filter is connected with the signal end of the output in-phase / quadrature baseband signal of the numerically controlled oscillator; The half-band filter is connected with the cascade integral comb filter and the frequency-selective finite impulse response filter respectively; The frequency-selective finite impulse response filter is connected with the DSP chip.

6. The sampling digital front-end signal processing system of claim 4, wherein, The passband start frequency of the bandpass filter is not less than 108 MHz, the cutoff frequency is not less than 112 MHz, the lower stopband cutoff frequency of the bandpass filter is not less than , the upper stopband cutoff frequency is not higher than , the stopband rejection is at least 60 dB, , and the sampling rate is 2.5 MHz.

7. The sampling digital front-end signal processing system of claim 4, wherein, The signal of the signal terminal outputting the in-phase baseband signal is , and the signal of the signal terminal outputting the quadrature baseband signal is ; wherein , , denotes the frequency of the digital radio frequency signal.

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