An emergency broadcast signal processing method, device and equipment

Abstract

This invention provides a method, apparatus, and device for processing emergency broadcast signals, relating to the field of communication processing technology. The method includes: acquiring an emergency broadcast signal in a first frequency band to be propagated, wherein the emergency broadcast signal in the first frequency band includes at least one piece of information to be propagated; filtering the emergency broadcast signal in the first frequency band to obtain a target purified signal; performing at least two frequency conversions on the target purified signal to obtain a second frequency band signal supported by a passive indoor distribution system; merging the second frequency band signal with a public network signal within the passive indoor distribution system to obtain a merged target transmission signal; and evenly distributing the target transmission signal to multiple preset transmission branch links, and transmitting it through the multiple preset transmission branch links to a receiving end in a corresponding preset target area for parsing to obtain the corresponding information to be propagated. The solution of this invention achieves stable transmission of FM emergency broadcast signals in a passive indoor distribution system.

Description

Technical Field

[0001] This invention relates to the field of communication processing technology, and in particular to a method, apparatus, and equipment for processing emergency broadcast signals. Background Technology

[0002] Existing passive indoor distribution systems support a minimum frequency band of 800MHz, while FM (frequency modulation) emergency broadcast signals operate in the 87-108MHz band, a difference of over 700MHz. This means FM signals cannot be directly fed into passive indoor distribution systems for transmission. The passive components of passive indoor distribution systems, such as power dividers, couplers, and feeders, suffer from excessive insertion loss (typically exceeding 15dB) in the 87-108MHz band, resulting in severe signal attenuation and failing to meet the signal strength requirements for emergency broadcast coverage. Furthermore, directly connecting FM emergency broadcast signals to passive indoor distribution systems would be problematic. However, its frequency band poses a potential interference risk with the public network's 2G / 3G / 4G / 5G signal frequency bands. First, spurious products of FM signals may intrude into the public network communication frequency bands, causing the public network signal's EVM index to deteriorate (exceeding the industry standard of ≤3%). Second, the strong power of the public network signal will suppress the weak FM signal, causing distortion in emergency broadcast reception, and the two cannot achieve stable transmission on the same network. Traditional FM emergency broadcasts are mostly transmitted above ground and cannot be transmitted in enclosed spaces such as underground passages and tunnels, thus making them unsuitable for scenarios in enclosed spaces such as passages and tunnels. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method, apparatus and equipment for processing emergency broadcast signals, which solves the problem that existing FM emergency broadcast signals cannot be directly fed into passive indoor distribution systems and transmitted stably.

[0004] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0005] This invention provides a method for processing emergency broadcast signals, applied to a terminal, the method comprising:

[0006] Acquire an emergency broadcast signal of a first frequency band to be transmitted, wherein the emergency broadcast signal of the first frequency band to be transmitted includes at least one piece of information to be transmitted;

[0007] The emergency broadcast signal of the first frequency band to be transmitted is filtered to obtain the target purified signal;

[0008] The target purification signal is subjected to at least two frequency conversion processes to obtain a second frequency band signal supported by the passive indoor distribution system; the minimum value of the frequency range of the second frequency band signal is greater than the maximum value of the frequency range of the first frequency band.

[0009] The second frequency band signal is combined with the public network signal in the passive indoor distribution system to obtain the combined target transmission signal;

[0010] The target transmission signal is evenly distributed to multiple preset transmission branch links, and then transmitted to the receiving end of the corresponding preset target area through the multiple preset transmission branch links to obtain the corresponding information to be transmitted.

[0011] The present invention also provides an emergency broadcast signal processing device, comprising:

[0012] The processing module is used to acquire an emergency broadcast signal in a first frequency band to be propagated, wherein the emergency broadcast signal in the first frequency band to be propagated includes at least one piece of information to be propagated; to filter the emergency broadcast signal in the first frequency band to obtain a target purified signal; to perform at least two frequency conversion processes on the target purified signal to obtain a second frequency band signal supported by the passive indoor distribution system; the minimum value of the frequency range of the second frequency band signal is greater than the maximum value of the frequency range of the first frequency band; to merge the second frequency band signal with the public network signal in the passive indoor distribution system to obtain a merged target transmission signal; and to evenly distribute the target transmission signal to multiple preset transmission branch links and transmit it to the receiving end of the corresponding preset target area through the multiple preset transmission branch links.

[0013] The transceiver module is used to evenly distribute the target transmission signal to multiple preset transmission branch links, and send it to the receiving end of the corresponding preset target area through the multiple preset transmission branch links for parsing to obtain the corresponding information to be transmitted.

[0014] Embodiments of the present invention also provide a computing device, including: a processor and a memory storing a computer program, wherein the computer program is executed by the processor to perform the above-described method.

[0015] The above-described solution of the present invention has at least the following beneficial effects:

[0016] The emergency broadcast signal processing method of the present invention includes: acquiring an emergency broadcast signal of a first frequency band to be transmitted, wherein the emergency broadcast signal of the first frequency band to be transmitted includes at least one piece of information to be transmitted; filtering the emergency broadcast signal of the first frequency band to be transmitted to obtain a target purified signal; performing at least two frequency conversion processes on the target purified signal to obtain a second frequency band signal supported by a passive indoor distribution system; wherein the minimum value of the frequency range of the second frequency band signal is greater than the maximum value of the frequency range of the first frequency band; merging the second frequency band signal with the public network signal within the passive indoor distribution system to obtain a merged target transmission signal; uniformly distributing the target transmission signal to multiple preset transmission branch links, and transmitting it through the multiple preset transmission branch links to the receiving end of the corresponding preset target area for parsing to obtain the corresponding information to be transmitted. This method achieves stable transmission of FM emergency broadcast signals in a passive indoor distribution system, while also improving the coverage of FM emergency broadcast signals and ensuring the stability of signals after long-distance transmission and multi-module processing. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the emergency broadcast signal processing method of the present invention;

[0018] Figure 2 This is a schematic diagram of the block structure of the emergency broadcast signal processing device of the present invention. Detailed Implementation

[0019] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0020] like Figure 1 As shown, an embodiment of the present invention proposes a method for processing emergency broadcast signals, applied to a terminal, the method comprising:

[0021] Step 11: Obtain the emergency broadcast signal of the first frequency band to be transmitted, wherein the emergency broadcast signal of the first frequency band to be transmitted includes at least one piece of information to be transmitted;

[0022] Step 12: Filter the emergency broadcast signal of the first frequency band to be transmitted to obtain the target purified signal;

[0023] Step 13: Perform at least two frequency conversion processes on the target purification signal to obtain a second frequency band signal supported by the passive indoor distribution system; the minimum value of the frequency range of the second frequency band signal is greater than the maximum value of the frequency range of the first frequency band.

[0024] Step 14: Combine the second frequency band signal with the public network signal in the passive indoor distribution system to obtain the combined target transmission signal;

[0025] Step 15: Distribute the target transmission signal evenly to multiple preset transmission branch links, and transmit it to the receiving end of the corresponding preset target area through the multiple preset transmission branch links to obtain the corresponding information to be transmitted.

[0026] In this embodiment, the emergency broadcast signal processing method is applied to a passive indoor distribution system to achieve lossless reception and transmission of the emergency broadcast signal. The passive indoor distribution system includes multiple indoor transmitting antennas. In operation, the outdoor FM emergency broadcast signal (emergency broadcast signal in the first frequency band, with a frequency range of 87-108MHz) is captured by the directional antenna of the passive indoor distribution system. It is first filtered by a dedicated FM bandpass filter to remove far-field clutter, and then amplified by a low-noise amplifier (LNA) with a 20dB gain (to suppress noise introduction). It is then transmitted to the indoor area through a low-loss coaxial cable. The data processing module of the indoor passive indoor distribution system adopts a two-stage frequency conversion strategy. First, the pre-processed FM signal is down-converted to a 450MHz intermediate frequency (avoiding the public network frequency band). After being purified by an intermediate frequency filter, it is up-converted to the 800-900MHz passive indoor distribution support frequency band. It is then amplified to 10-15dBm by a power amplifier (AGC module calibrates power fluctuations) to obtain the target frequency band signal supported by the passive indoor distribution system.

[0027] The frequency-converted FM signal (second frequency band signal) is connected to the transmitter of the passive indoor distribution system through the POI independent port of the full-band combining platform (inter-port isolation ≥80dB). The power is distributed through a broadband power divider and coupler, and then evenly covered to the target area (buildings, tunnels, etc.) through leaky cable or antenna feeder.

[0028] The receiver uses a built-in downconverter to restore the 800-900MHz signal to the original 87-108MHz FM signal, which is then further purified by a SAW filter and analyzed to obtain the corresponding information to be transmitted. Smartphones that support the 3GPPR16 standard can achieve system-level forced wake-up.

[0029] In one optional embodiment, the core module is encapsulated with a metal shield and reliably grounded, and a notch filter is added to the public network signal branch to avoid mutual interference between the FM signal and the public network signal, ensuring stable transmission over the shared network.

[0030] The emergency broadcast signal processing method described in this invention achieves precise adaptation between the 87-108MHz FM signal and the 800-900MHz passive indoor distribution frequency band through frequency conversion design. This completely solves the problem of signal access failure caused by frequency band differences and the inability of existing FM emergency broadcast signals to cover enclosed spaces. Furthermore, signals are prone to frequency drift and power fluctuations after long-distance transmission and multi-module processing. This method achieves stable transmission of FM emergency broadcast signals in passive indoor distribution systems, improves the coverage of FM emergency broadcast signals, and can be applied to sealed indoor scenarios such as underground tunnels. At the same time, through multi-layer filtering and multi-channel isolation design, the isolation between the FM signal and the public network signal is ≥80dB, and the EVM index of the public network signal is kept stable within the industry standard of ≤3%, achieving stable transmission of both signals on the same network without interference, and ensuring the stability of the signal after long-distance transmission and multi-module processing.

[0031] In an optional embodiment of the present invention, step 11 may specifically include:

[0032] The emergency broadcast signal of the first frequency band to be transmitted is acquired through the receiving module of the transmitting end; the receiving module adopts a dedicated FM receiving module with integrated low noise amplifier (LNA), which can improve the weak signal acquisition capability while suppressing noise, and the noise figure is controlled at ≤1.5dB to ensure effective reception of long-distance FM signals; the transmission medium is low loss coaxial cable, and the length is optimized according to the actual scenario based on the signal attenuation control requirements (typical configuration 80 meters). Both ends are equipped with standardized connectors, and the outdoor end adopts a triple waterproof protection structure to avoid signal attenuation and interface damage caused by rainwater erosion.

[0033] In an optional embodiment of the present invention, step 12, filtering the emergency broadcast signal of the first frequency band to be propagated to obtain the target purified signal, may include:

[0034] Step 121: Perform bandpass filtering on the emergency broadcast signal of the first frequency band to be transmitted to obtain an intermediate signal;

[0035] Step 122: Perform low-noise gain amplification processing on the intermediate signal to obtain the target purified signal.

[0036] In this embodiment, after the emergency signal enters the room, it first undergoes bandpass filtering for frequency band selection. Utilizing the frequency selectivity of the filter, only FM signals in the 87-108MHz range are allowed to pass through, filtering out noise outside the frequency band and ensuring that the output signal-to-noise ratio is ≥18dB. Then, it undergoes 20dB gain amplification, i.e., low-noise gain amplification, through a low-noise amplifier (LNA). Finally, the signal path is switched through an RF (radio frequency switch), accurately connecting the purified signal (target purified signal) to the frequency conversion unit of the subsequent passive indoor distribution system, thus completing the signal purification and transmission connection in the preprocessing stage.

[0037] In this embodiment, step 121, which involves bandpass filtering the emergency broadcast signal of the first frequency band to be transmitted to obtain an intermediate signal, may include:

[0038] Step 1211: Determine the first center frequency and first bandwidth of the emergency broadcast signal in the first frequency band;

[0039] Step 1212: Determine the second-order bandpass parameters of the second-order bandpass filter based on the first center frequency and the first bandwidth. The second-order bandpass parameters include the first inductance parameter and the first capacitance parameter of the resonant circuit in the second-order bandpass filter.

[0040] Step 1213: Determine the lower cutoff frequency and the upper cutoff frequency based on the first center frequency;

[0041] Step 1214: Based on the second-order bandpass parameters, the signal that the emergency broadcast signal of the first frequency band passes between the lower cutoff frequency and the upper cutoff frequency is determined as the intermediate signal.

[0042] In this embodiment, in step 1211, for the emergency broadcast signal of the first frequency band with a frequency range of 87-108MHz, the first center frequency is 97.5 MHz and the first bandwidth is 21 MHz.

[0043] In this embodiment, step 1212, determining the second-order bandpass parameters of the second-order bandpass filter based on the first center frequency and the first bandwidth, includes:

[0044] Step 12121, based on the first bandwidth and formula Determine the first inductance parameter in the second-order bandpass parameters. Where R is the system impedance, BW represents the first bandwidth of the emergency broadcast signal in the first frequency band.

[0045] Step 12122, based on the first center frequency, the first inductor parameters, and the formula Determine the first capacitance parameter C in the second-order bandpass parameters; where, , This is the first center frequency.

[0046] In this embodiment, step 1213, determining the lower cutoff frequency and the upper cutoff frequency based on the first center frequency, may include:

[0047] Through formula Determine the cutoff frequency ;

[0048] Through formula Determine the upper cutoff frequency ;

[0049] in, This is the first center frequency of the emergency broadcast signal in the first frequency band. This is the first bandwidth of the emergency broadcast signal in the first frequency band.

[0050] In this embodiment, step 1214, based on the second-order bandpass parameter, determines the signal passing between the lower cutoff frequency and the upper cutoff frequency of the emergency broadcast signal in the first frequency band as the intermediate signal, which may specifically include:

[0051] Determine the corresponding second-order bandpass filter based on the second-order bandpass parameters, the lower cutoff frequency, and the upper cutoff frequency;

[0052] The emergency broadcast signal (87–108 MHz) of the first frequency band to be transmitted is connected to the input of the corresponding second-order bandpass filter. The signal passes through the filter... and The resonant network formed when the signal frequency is close to When the frequency is at its lowest, the impedance of the series branch is at its lowest, and the voltage amplitude at the output terminal (such as across the capacitor) is at its highest. When the frequency deviates from the first center frequency, the impedance increases and the output amplitude decreases, so that the filter output terminal obtains the filtered signal, i.e., the intermediate signal. This signal retains the frequency components in the range of 87 to 108 MHz and filters out far-field noise interference outside the frequency band, becoming a clean intermediate signal.

[0053] In an optional embodiment of the present invention, step 121, which involves bandpass filtering the emergency broadcast signal of the first frequency band to be transmitted to obtain an intermediate signal, further includes:

[0054] Step 1215: Perform mirror suppression filtering on the intermediate signal and output the intermediate signal after mirror suppression filtering as the final intermediate signal.

[0055] In this embodiment, step 1215 may include:

[0056] Step 12151: Determine the second center frequency and second bandwidth corresponding to the first image frequency band;

[0057] Step 12152: Determine the image filtering parameters of the band-stop filter based on the second center frequency and the second bandwidth. The image filtering parameters include: the first resonant cavity parameters, the second resonant cavity parameters, and the coupling parameters of the first and second resonant cavities of the band-stop filter.

[0058] Step 12153: Based on the mirror filtering parameters, perform mirror suppression filtering on the intermediate signal, and output the intermediate signal after mirror suppression filtering as the final intermediate signal.

[0059] In this embodiment, by performing image suppression filtering on the intermediate signal, the image frequency interference problem of the superheterodyne architecture can be solved (the pure 87-108MHz FM signal after bandpass filtering may still be interfered by the adjacent 987-1008MHz image signal). This blocks the 987-1008MHz image signal in the adjacent FM band from entering the subsequent link, preventing it from interfering with the intermediate frequency signal after frequency conversion, thereby further ensuring the purity of the filtered signal and providing a stable frequency conversion signal for subsequent downconversion. Specifically, a dual-tuned cavity structure can be adopted, and by setting the cavity spacing and coupling coefficient, a deep stopband can be designed for the first image band of 987-1008MHz to achieve selective attenuation of the image signal. After the intermediate signal enters the bandstop filter, the 987-1008MHz image signal is deeply attenuated (suppression ratio ≥45dB), while the useful 87-108MHz FM signal passes normally (in-band insertion loss ≤0.8dB), thereby completing the suppression of image interference and eliminating the image interference signal.

[0060] In this embodiment, the second bandwidth corresponding to the first mirror band is The second center frequency corresponding to the first image band of MHz .

[0061] In an optional embodiment of the present invention, step 12152, determining the image filtering parameters of the band-stop filter based on the second center frequency and the second bandwidth, may include:

[0062] Based on the second center frequency and the second bandwidth, using the formula Determine the loaded Q value corresponding to the first resonant cavity. ;in, The second center frequency; For the second bandwidth;

[0063] Based on the second center frequency, the second bandwidth, and the loaded Q value And preset the second inductor parameters, through the formula Determine the resonant resistance corresponding to the first resonant cavity. ;in, ; To preset the second inductor parameter, a value of 5nH can be used;

[0064] Based on the preset second inductance parameters, using the formula Determine the second capacitance parameters corresponding to the first resonant cavity. ;

[0065] Based on the second center frequency and the second bandwidth, using the formula Determine the coupling coefficient k between the first and second resonant cavities; where, , ;

[0066] Based on the coupling coefficient k, using the formula and Determine the inductive coupling parameter M and the capacitive coupling parameter M of the first resonant cavity and the second resonant cavity. .

[0067] In this embodiment, the band-stop filter is connected in series after the band-pass filter to form a two-stage filter cascade; the parameters of the first resonant cavity and the second resonant cavity are the same; once the image filter parameters are determined, the corresponding band-stop filter can be constructed according to the determined image filter parameters, and then the intermediate signal is input to the band-stop filter for image suppression filtering processing, thereby obtaining the intermediate signal after image suppression filtering processing, and the signal is output as the final intermediate signal.

[0068] In an optional embodiment of the present invention, step 13, performing frequency conversion processing on the target purification signal to obtain a second frequency band signal supported by the passive indoor distribution system, may include:

[0069] Step 131: Perform down-conversion processing on the target purification signal to obtain a mid-frequency signal in a different frequency band from the public network signal;

[0070] Step 132: Perform up-conversion processing on the intermediate frequency signal to obtain the second frequency band signal supported by the passive indoor distribution system.

[0071] In this embodiment, a dual-stage frequency conversion strategy, namely an intermediate frequency transition design, is adopted to achieve precise adaptation between the low-frequency FM signal and the high-frequency band supported by the passive indoor distribution system, while avoiding spurious interference problems caused by direct frequency conversion. The radio frequency signal is converted into an intermediate frequency signal (IF signal) of a preset frequency band by the digital downconverter (DDC) inside the Transceiver chip. The IF signal must avoid the public network 2G / 3G / 4G frequency bands and have spurious attenuation ≥70dBc to reduce the risk of interference from the source. Optionally, the IF signal is a 450MHz IF signal.

[0072] In an optional embodiment of the present invention, step 131, which involves down-converting the target purification signal to obtain a mid-frequency signal in a different frequency band from the public network signal, may include:

[0073] Step 1311: Determine the first local oscillator signal based on the target purification signal;

[0074] Step 1312: Lock the first local oscillator signal to obtain the locked first local oscillator signal;

[0075] Step 1313: Mix the locked first local oscillator signal and the target purification signal to obtain the first mixed output signal;

[0076] Step 1314: Perform intermediate frequency filtering on the first mixing output signal to obtain an intermediate frequency signal in a different frequency band from the public network signal.

[0077] In this embodiment, step 1311 can specifically be achieved by using the formula... Determine the first local oscillator signal; where, The target purification signal corresponds to a frequency of 87-108 MHz. The target intermediate frequency is 450 MHz; therefore, the local oscillator frequency range of the first local oscillator signal is: Based on the local oscillator signal within this frequency range and the target purification signal, the signal is processed by a mixer to output the first local oscillator signal.

[0078] In this embodiment, step 1312, which involves locking the first local oscillator signal to obtain the locked first local oscillator signal, may include:

[0079] Step 13121: Input the local oscillator frequency range and preset frequency accuracy parameters of the first local oscillator signal into the preset phase-locked loop controller to obtain the second local oscillator signal;

[0080] Step 13122: Divide the second local oscillator signal to the frequency corresponding to the preset reference crystal oscillator to obtain the first local oscillator signal after frequency division;

[0081] Step 13123: Compare the phase of the first local oscillator signal after frequency division with the preset reference crystal oscillator signal, and output the phase error voltage;

[0082] Step 13124: Adjust the output frequency of the preset phase-locked loop controller in real time according to the feedback error voltage until the phase difference between the second local oscillator signal and the reference crystal oscillator signal approaches zero, and obtain the locked first local oscillator signal.

[0083] In this embodiment, the loop bandwidth of the preset phase-locked loop controller is 5~10 kHz; the frequency corresponding to the preset reference crystal oscillator is 10MHz; by locking the first local oscillator signal, the frequency stability can be ≤±2ppm, thereby ensuring that the frequency band can be matched with the passive indoor distribution device; after locking, the first local oscillator signal can be output through an isolator (reverse isolation ≥25dB) to prevent noise from the mixer output terminal from being fed back to the local oscillator module, and at the same time, the signal driving capability is improved to +7 dBm through a buffer amplifier.

[0084] In an optional embodiment of the present invention, step 1313, mixing the locked first local oscillator signal and the target purification signal to obtain a first mixed output signal, may include:

[0085] The locked first local oscillator signal and the target purification signal are subjected to difference frequency and sum frequency mixing operations to obtain a first mixing output signal; the first mixing output signal includes the locked first local oscillator signal leakage signal, the target purification signal leakage signal, the intermediate frequency signal, and the useless component signal.

[0086] In this embodiment, the difference frequency mixing operation is the locked first local oscillator signal ( to The absolute value of the difference between the target purification signal and the target purification signal is the target purification signal (450). The sum-frequency mixing operation is the locked first local oscillator signal (); to Adding the target purification signal to the signal yields the useless component signal.

[0087] In an optional embodiment of the present invention, step 1314, performing intermediate frequency filtering on the first mixer output signal to obtain an intermediate frequency signal in a different frequency band from the public network signal, may include:

[0088] Determine the third center frequency and third bandwidth of the intermediate frequency signal; the third center frequency is 450MHz; the third bandwidth is 21MHz.

[0089] Based on the third center frequency and the third bandwidth, the intermediate frequency filtering parameters of the intermediate frequency filter are determined. The intermediate frequency filtering parameters include the third inductance parameter and the third capacitance parameter of the resonant circuit in the intermediate frequency filter.

[0090] Based on the third center frequency, determine the intermediate frequency lower cutoff frequency and the intermediate frequency upper cutoff frequency;

[0091] Based on the intermediate frequency filtering parameters, the signal that the first mixer output signal passes between the intermediate frequency lower cutoff frequency and the intermediate frequency upper cutoff frequency is determined as the intermediate frequency signal.

[0092] In this embodiment, the process of intermediate frequency filtering of the first mixing output signal is the same as the process of filtering the intermediate signal. Both can be filtered by a bandpass filter to obtain the corresponding intermediate frequency signal.

[0093] In an optional embodiment of the present invention, step 131, which involves down-converting the target purification signal to obtain a mid-frequency signal in a different frequency band from the public network signal, may further include:

[0094] Step 1315: Detect and process the clutter components in the intermediate frequency signal to obtain the detection result;

[0095] Step 1316: Based on the detection results, the intermediate frequency signal is subjected to image residue suppression processing to obtain the image-suppressed intermediate frequency signal, and the image-suppressed intermediate frequency signal is used as the input signal for upconversion processing.

[0096] In this embodiment, step 1315 can be: real-time acquisition of intermediate frequency spectrum (intermediate frequency signal) through background monitoring unit; if clutter components above -70dBm are detected, output is determined to be residual image interference; step 1316 can be: when it is determined to be residual image interference, the intermediate frequency signal is subjected to residual image interference suppression processing to obtain the intermediate frequency signal after image suppression, and the intermediate frequency signal after image suppression is used as the input signal for upconversion processing.

[0097] In this embodiment, the image residual suppression design can solve the image frequency interference problem in the signal frequency conversion process. It can prevent the interference of the adjacent image frequency to the frequency-converted signal during the frequency conversion process. By predicting the image frequency, signal strength and local oscillator drift in the next 20ms, the local oscillator is calibrated in advance and the filter parameters are dynamically adjusted to achieve active interference suppression.

[0098] In an optional embodiment of the present invention, step 1316, which involves performing image retention suppression processing on the intermediate frequency signal based on the detection result to obtain an image-suppressed intermediate frequency signal, may include:

[0099] Step 13161: When the detection result indicates that the detected clutter component exceeds the preset threshold, calculate the notch frequency and configure the notch processing parameters.

[0100] Step 13162: Perform image lingering suppression processing on the mid-frequency signal according to the notch processing parameters to obtain the image-suppressed mid-frequency signal.

[0101] In this embodiment, step 13131 can be that the intermediate frequency signal is first purified by the original intermediate frequency filter (with in-band ripple ≤0.3dB) and then enters the programmable notch filter. The monitoring unit collects the intermediate frequency spectrum in real time. If clutter components above -70dBm are detected (determined to be residual image interference), the notch frequency is automatically calculated and a configuration command is issued.

[0102] Step 13132 can specifically involve applying the notch filter to the first stable frequency signal according to the notch processing parameters, whereby the filter attenuates the interference components by a depth of ≥35dB to ensure the purity of the intermediate frequency signal, thereby obtaining the first frequency signal.

[0103] Based on the above embodiments, the following example illustrates the specific implementation process of the image frequency anti-interference described above:

[0104] After the outdoor FM signal is captured by the antenna, it first passes through a dedicated FM bandpass filter to remove far-field clutter (out-of-band attenuation ≥65dB), and then enters the image rejection filter. This filter is based on coupled resonant cavity technology. By setting the cavity spacing and coupling coefficient, it forms a deep attenuation of the 987-1008MHz image signal in the adjacent FM frequency band, and physically blocks it from entering the subsequent link.

[0105] The filtered pure FM signal is amplified by 20dB low noise (noise figure ≤1.5dB) by LNA, transmitted to the room through low loss coaxial cable (transmission loss ≤3dB), and finally connected to the frequency converter unit through RF switch to complete the signal purification and initial suppression of image interference in the preprocessing stage.

[0106] The specific implementation process of frequency conversion:

[0107] First-stage down-conversion: The SDR module receives the pre-processed FM signal, and the local oscillator module accurately outputs a 537-558MHz first local oscillator signal, which is then isolated by an isolator and sent to the mixer. The isolator, through its unidirectional transmission characteristic, prevents noise feedback from the mixer output to the local oscillator module, thus preventing local oscillator frequency drift. The mixer, based on the superheterodyne principle, down-converts the FM signal to a 450MHz intermediate frequency. A high-linearity model can be selected to effectively reduce the nonlinear generation of image frequency components. Simultaneously, the background monitoring unit collects the actual local oscillator frequency every 10ms and compares it with the theoretical value. If the deviation exceeds ±50... Upon reaching Hz, a PLL calibration command is immediately triggered. The local oscillator output is corrected by adjusting the loop filter parameters to ensure that the image frequency is stable at 987-1008MHz and does not overlap with the useful signal frequency band. The intermediate frequency signal is first purified by the original intermediate frequency filter (with internal ripple ≤0.3dB) and then enters the programmable notch filter. The monitoring unit collects the intermediate frequency spectrum in real time. If clutter components above -70dBm are detected (determined to be residual image interference), the notch frequency is automatically calculated and a configuration command is issued. The filter attenuates the interference components by ≥35dB to ensure the purity of the intermediate frequency signal.

[0108] In an optional embodiment of the present invention, step 132, up-converting the intermediate frequency signal to obtain a second frequency band signal supported by the passive indoor distribution system, may include:

[0109] Step 1321: Upconvert the intermediate frequency signal to obtain the upconverted frequency band signal supported by the passive indoor distribution system. The upconverted frequency band signal includes multiple upconverted signals of different frequencies.

[0110] Step 1322: Filter the up-converted signal to obtain an up-converted filtered signal;

[0111] Step 1323: Perform multi-channel isolation processing on the signals of different frequency bands in the up-conversion filtered signal to obtain the second frequency band signal.

[0112] In this embodiment, step 132 can specifically be to directly convert the signal into an 800-900MHz passive indoor distribution system supported idle frequency band signal (upconverted signal) through the digital upconverter (DUC) of the Transceiver chip. The resulting upconverted signal includes multiple different frequencies, such as 801MHz, 802MHz...900MHz. By upconverting the intermediate frequency signal, the intermediate frequency signal can be effectively converted into a frequency band signal that the passive indoor distribution system can access, thereby enabling the emergency broadcast signal to be accessed into the passive indoor distribution system without loss.

[0113] In an optional embodiment of the present invention, step 1321, which involves up-converting the intermediate frequency signal to obtain an up-converted frequency band signal supported by the passive indoor distribution system, may include:

[0114] Step 13211: Determine the third local oscillator signal based on the intermediate frequency signal;

[0115] Step 13212: Lock the third local oscillator signal to obtain the locked third local oscillator signal;

[0116] Step 13213: Mix the locked third local oscillator signal and the intermediate frequency signal to obtain the second mixed output signal;

[0117] Step 13214: Filter the second mixing output signal to obtain the up-conversion band signal supported by the passive indoor distribution system.

[0118] In this embodiment, the up-conversion process is the reverse of the down-conversion process, and its purpose is to convert 450... The mid-frequency signal is up-converted to the 800-900MHz passive indoor distributed antenna system support band; among which, the third local oscillator signal ,in It is a medium frequency signal. For the up-conversion band signal, the third local oscillator signal, i.e., the up-conversion local oscillator frequency range, can be obtained through calculation. ;

[0119] In this embodiment, step 13212 may include: generating a locked third local oscillator signal through a phase-locked loop frequency synthesizer;

[0120] Step 13213 involves inputting the third local oscillator signal and the intermediate frequency signal into a mixer for processing, and outputting a signal containing sum-frequency components. and difference frequency components The mixing signal is the second mixing output signal, where the sum frequency component is the required up-converted frequency band signal; since the intermediate frequency signal carries FM information with a bandwidth of 21MHz, after up-conversion, this information is shifted to the corresponding position in the 800-900MHz frequency band, forming multiple up-converted frequency signals of different frequencies (corresponding to different input FM frequencies).

[0121] Step 13214 specifically involves connecting the up-converted mixer output signal to a bandpass filter, the center frequency of which is set to... (Taking the geometric center of 800-900MHz), passband bandwidth (Covering the entire 800-900MHz frequency band), the passband insertion loss is ≤1 dB, and the stopband suppression is ≥60 dB in both the difference frequency component band (0-100MHz) and the local oscillator leakage band (350-450MHz). After filtering, the up-conversion signal in the 800-900MHz range passes through with low loss, while the difference frequency component, local oscillator leakage and other spurious signals are significantly attenuated, resulting in a pure up-conversion filtered signal, which retains all the modulation information of the original FM emergency broadcast.

[0122] In this embodiment, step 1323 involves performing multi-channel isolation processing on signals of different frequency bands in the up-conversion filter signal to obtain a second frequency band signal. Specifically, to achieve multi-signal network transmission, independent transmission channels are allocated to signals of different frequency bands in the up-conversion filter signal based on the principle of multi-channel isolation. Different channels use different frequency signals, and the isolation design of the combiner / splitter achieves an isolation degree of ≥80dB between channels to avoid mutual interference with other signals. After isolation, the signal is amplified to 10-15dBm by a power amplifier to meet the input power requirements of the passive indoor distribution system. At the same time, the signal amplitude is monitored in real time by an automatic gain control (AGC) module, and the amplifier is dynamically adjusted accordingly. Gain is optimized to ensure output power fluctuation ≤ ±0.5dB, guaranteeing signal transmission stability. The power amplifier module employs a linear power amplifier with an output power designed for 10-15dBm and an adjustable gain range of 0-30dB. By optimizing the linear operating region of the amplifier circuit, a third-order intermodulation point ≥35dBm is ensured, preventing nonlinear distortion during signal amplification. The auxiliary filtering stage includes a 450MHz intermediate frequency (IF) filter and a second-order LC cavity filter. The IF filter has an in-band ripple ≤0.3dB, ensuring the purity of the IF signal. The LC cavity filter is designed for the 800-900MHz frequency band, with out-of-band attenuation ≥55dB, further suppressing spurious signals after frequency conversion.

[0123] In an optional embodiment of the present invention, step 14, which involves merging the second frequency band signal with the public network signal within the passive indoor distribution system to obtain the merged target transmission signal, may specifically include:

[0124] The second frequency band signal is connected to a preset isolator. The preset isolator physically isolates and combines the second frequency band signal with the existing public network signal in the passive indoor distribution system to obtain the target transmission signal.

[0125] In this embodiment, the FM emergency broadcast signal after up-conversion, i.e. the second frequency band signal (800-900MHz), is transmitted through a low-loss radio frequency cable and through the independent dedicated input port of the multi-system combining platform device.

[0126] Base station signals (e.g., 900MHz / 1800MHz / 2100MHz, etc.) from different operators (such as China Mobile, China Unicom, and China Telecom) are connected to other corresponding independent input ports of the POI through their respective radio frequency cables;

[0127] Inside the POI, each input signal first passes through a bandpass filter for that frequency band; for the FM emergency broadcast link, the filter allows 800-900MHz to pass through, further suppressing out-of-band spurious signals; for the public network link, the filter only allows its specific operating frequency band to pass through, preventing spurious signals (even very weak) from leaking back to the base station equipment.

[0128] After purification, each signal enters the star or cascaded combining unit of the POI. Specifically, the second-band signal is input to the first port Port1 of the POI. The bridge of the POI splits the second-band signal into two paths: one to the third port Port3 (output) and the other to Port4 (isolation). The public network signal enters the port Port2 of the POI, and is also split into two paths: one to the third port Port3 (output) and the other to the fourth port Port4 (isolation). The signals are combined at the output port Port3. The bridge design ensures that the signal phase from Port1 is 0° and the signal phase from Port2 is 0°. The power is directly added.

[0129] With the cancellation at the isolation port Port4, the bridge design ensures that: the signal phase from Port1 is 0°; the signal phase from Port2 is 180°; the phase cancellation results in zero power; there is no power output at Port4, and the actual load absorbs the residual power.

[0130] The final combined output is a 3dB bridge output: target transmitted signal; isolation terminal: 0W, connected to a dummy load. This achieves: same-band, same-point, dual-carrier power combining. This enables the combining and isolation of multi-band signals, ensuring that FM signals and public network 2G / 3G / 4G / 5G signals are transmitted independently within the same indoor distribution system without interference.

[0131] In an optional embodiment of the present invention, step 15, which involves uniformly distributing the target transmission signal to multiple preset transmission branch links and transmitting it through these links to the receiving end of the corresponding preset target area for parsing to obtain the corresponding information to be propagated, may include:

[0132] The merged target signal is input into a passive distributed network. The signal power is evenly distributed to multiple branch links by a power divider. The coupler extracts the corresponding signal power according to the coverage requirements and feeds it into the receiving end of the target area for parsing to obtain the corresponding information to be propagated.

[0133] In this embodiment, the signal is transmitted to the target area through a leaky cable or antenna feeder. The leaky cable radiates the signal evenly to enclosed spaces such as tunnels through its surface radiating holes, while the antenna feeder covers the signal to open indoor scenes such as buildings through its directional radiation characteristics. To further improve anti-interference capability, an independent metal shield is used for packaging, and shielded cables are used for the RF traces between modules, with the length controlled within 1 meter to reduce radiation interference caused by signal coupling. The power supply end adopts a combination of π-type filtering and common-mode choke. The π-type filter consists of capacitors and inductors of different capacitance values ​​to suppress differential-mode interference on the power line, while the common-mode choke suppresses common-mode interference, ensuring a power supply rejection ratio (PSRR) ≥ 65dB@1MHz to avoid power supply conducted interference affecting signal quality. After the merged target transmission signal is sent to the receiving end, the receiving end receives the 800-900MHz transmission signal and first... The built-in downconverter restores the signal to the original 87-108MHz FM signal. This process is achieved through reverse frequency conversion to ensure the accuracy of frequency conversion. The restored signal is further purified by a SAW filter, with out-of-band noise suppression ≥40dB, ensuring a receiving sensitivity ≥1.2μV. The restored and purified signal content is then analyzed. For audio media content, the appropriate audio encoding format is used for encapsulation. After receiving the signal, the terminal first performs digital signature verification to verify the legality and integrity of the information and prevent the spread of illegal broadcast content. After successful verification, the information is displayed through the built-in player or associated application. For smartphones that support the 3GPPR16 5G broadcast television standard, a system-level wake-up mechanism is adopted. Even if the terminal is in a black screen or locked state, it can be forcibly woken up by the emergency broadcast signal with a wake-up delay ≤1s, ensuring that emergency information reaches the user in a timely manner in emergency situations.

[0134] In an optional embodiment of the present invention, the method for processing the emergency broadcast signal may further include:

[0135] Step 161: Acquire the target purification signal parameters, target transmission signal parameters, and public network signal parameters in real time according to the preset sampling period;

[0136] Step 162: Based on the real-time monitoring values ​​of the target purification signal parameters, the target transmission signal parameters, and the public network signal parameters, optimize and adjust the frequency band of the target frequency band signal during the upconversion process.

[0137] In this embodiment, step 161 may specifically include:

[0138] FM signal parameters (power parameters of the target purified signal and power parameters of the target transmitted signal) and public network signal EVM index (power parameters of the public network signal) are collected according to the preset sampling period.

[0139] Step 162, based on the real-time monitoring values ​​of the target purification signal parameters, the target transmission signal parameters, and the public network signal parameters, optimizes and adjusts the frequency band of the target frequency band signal during the upconversion process, which may include:

[0140] Step 1621: Compare the real-time monitoring value with the preset threshold to obtain the comparison result;

[0141] Step 1622: When the real-time monitoring value in the comparison result is greater than the preset threshold, the frequency band of the target frequency band signal in the upconversion process is adjusted by the preset first priority strategy or the second priority strategy. The first priority strategy is that the background system automatically triggers the control mechanism to adjust the frequency band of the target frequency band signal in the upconversion process to the spare idle channel. The second priority strategy is to cut off the transmission of the target frequency band signal within a first preset time period.

[0142] In this embodiment, when interference ≥ -80dBm or public network EVM index > 3% is detected, the frequency band of the target frequency band signal during the upconversion process is adjusted using a preset first priority strategy or a second priority strategy. Specifically, the first priority strategy involves the background system automatically triggering a control mechanism to adjust the frequency band of the target frequency band signal during the upconversion process to a spare idle channel when interference ≥ -80dBm or public network EVM index > 3% is detected. This process is implemented by issuing a frequency adjustment command to the frequency conversion unit, with a response time ≤ 500ms. The second priority strategy is activated if the interference is not eliminated after frequency band adjustment, cutting off the FM signal within 100ms to avoid interference with the public network. Communication is affected; in this embodiment, the specific implementation process for optimization and adjustment can be achieved through the following hardware deployment: An MQTTBroker and a database are deployed on the backend server. The MQTTBroker supports access from 5000+ devices and is responsible for message forwarding between terminal devices and the server. Its lightweight communication protocol design is suitable for remote communication of IoT devices. The database is used to store device operating status data, historical monitoring data, and parameter modification records, supporting rapid data query and traceability. The monitoring module is integrated into the SDR module, which achieves comprehensive monitoring of FM signal quality by real-time acquisition of parameters such as signal-to-noise ratio, distortion, and frequency offset. The accuracy of the public network signal EVM monitor is ≤0.1% is used for real-time assessment of public network signal interference; the dispatch terminal can include a web client and a mobile APP. The web client is developed based on the Vue3+Vite+ElementPlus technology stack, providing a visual device management and monitoring interface; the mobile APP adopts a cross-platform development framework, supporting Android, iOS, and mini-program operation, meeting the diverse needs of on-site operation and maintenance and remote management; the monitoring unit collects FM signal parameters and public network signal EVM indicators at a sampling period of 100ms. The sampled data is uploaded to the backend server via MQTT protocol through the 4G network. The server performs real-time analysis and storage of the data; when interference ≥-80dBm or public network EVM indicator >3% is detected, the backend system automatically triggers the control mechanism. The first priority strategy is to adjust the upconverter frequency band to a spare idle channel. This process is achieved by issuing a frequency adjustment command to the frequency conversion unit, with a response time ≤500ms; if the frequency band is adjusted... If the interference persists, a second-priority strategy is activated to cut off the FM signal within 100ms to avoid impacting public communications. Administrators can remotely issue parameter configuration commands via a web interface or mobile app, such as adjusting transmission power or switching emergency broadcast content. Commands are pushed to the gateway device via MQTT Topics. After executing the commands, the gateway returns the execution results to the server via a feedback Topic. The server records the parameter modification history, including old and new values, the operator, and the operation time, supporting full traceability. To expand coverage, 5G broadcast technology can be integrated. In emergency scenarios, the backend system distributes converged media emergency data via RTMP streaming interfaces. Combined with the wide coverage advantage of broadcast television towers (with inter-tower spacing exceeding 60km), this provides wider coverage and stronger disaster resistance compared to traditional communication base stations, enabling emergency information delivery to remote areas and network blind spots, and improving emergency broadcast service capabilities in extreme situations.

[0143] In an optional embodiment of the present invention, the method for processing the emergency broadcast signal may further include:

[0144] Step 171: Obtain the spectrum data, ambient temperature data, equipment voltage data, and local oscillator correlation data of the processing equipment during the emergency broadcast signal processing process;

[0145] Step 172: Perform noise reduction and normalization preprocessing on the spectrum data, ambient temperature data, equipment voltage data, and local oscillator correlation data to generate feature vectors;

[0146] Step 173: Input the feature vector data into a preset prediction model for prediction processing to obtain the image frequency, signal strength and local oscillator drift within a preset time period in the future; wherein, the preset prediction model is obtained by training a preset neural network model with a preset historical feature data training set;

[0147] Step 174: Based on the image frequency, signal strength, and local oscillator drift within a preset time period in the future, dynamically adjust the local oscillator frequency, image filtering parameters, and notch filtering parameters.

[0148] In this embodiment, the design of the predictive model can reduce the response delay to less than 100ms during the original image interference suppression process, thereby coping with rapidly changing interference scenarios (such as sudden strong image signals). At the same time, it can realize dynamic adjustment of image frequency, signal strength and local oscillator drift, thereby improving the image suppression accuracy.

[0149] In this embodiment, to achieve the above process, the hardware configuration for the signal reception and preprocessing stages retains an FM-dedicated bandpass filter (87-108MHz, out-of-band attenuation ≥65dB), an image rejection filter (initial stopband 987-1008MHz, rejection ratio ≥45dB), a low-noise amplifier (LNA, gain 20dB, noise figure ≤1.5dB), low-loss coaxial cable, and IP65 protection components; a new multi-dimensional data acquisition module is added, integrating a spectrum analyzer chip, a temperature sensor, and a voltage monitoring chip, with a data interface supporting 1kHz high-speed transmission to ensure the real-time performance and integrity of the acquired data;

[0150] In terms of hardware configuration for frequency conversion processing, in addition to the existing PLL+TCXO local oscillator, high-performance mixer (IP3≥40dBm), programmable notch filter (450MHz intermediate frequency, notch depth≥35dB), SDR module, power amplifier (output 10-15dBm), and AGC module, a lightweight neural network processing module has been added (integrated into the high-performance host, equipped with a GPU accelerator card, supporting single inference time ≤0.5ms); three new types of control interfaces have been added: filter parameter control interface (adjusting the resonant frequency and attenuation depth of the image rejection filter via I2C protocol), local oscillator pre-calibration trigger interface (issuing calibration commands via SPI protocol), and notch parameter preset interface (supporting software configuration of notch frequency and depth). The dual-stage frequency conversion architecture (87-108MHz→450MHz→800-900MHz) and multi-channel isolation design (inter-channel isolation ≥80dB) are retained to ensure that the core functions of frequency band adaptation are not affected.

[0151] In this embodiment, the spectrum data mentioned in step 171 is obtained by a spectrum analyzer chip at 1ms intervals, which collects the signal strength (resolution 0.1dBm) of the 87-108MHz FM useful frequency band and the 987-1008MHz first image frequency band, the spectrum flatness (calculating the amplitude fluctuation within the 3dB first bandwidth), and the peak frequency (accurate to 1Hz). The time-domain signal is converted into frequency-domain data, and feature parameters are extracted. The environmental and equipment parameters are obtained by a temperature sensor (accuracy ±0.5℃) to monitor the operating environment temperature of the equipment in real time, and a voltage monitoring chip (accuracy ±0.01V) to collect the power input voltage. Data is uploaded every 1ms to capture the instantaneous fluctuations of temperature and voltage. The local oscillator correlation data is obtained by collecting the actual output frequency of the local oscillator (resolution 1Hz), the PLL loop lock status (locked / unlocked), and the loop filter output voltage every 1ms through the dedicated interface of the SDR module, providing data support for analyzing the local oscillator drift law.

[0152] In this embodiment, step 172 specifically involves uploading the collected data to the background preprocessing module via a 4G network. Random noise is first removed by moving average filtering (window size of 5 sampling points), and then Min-Max normalization is used to map the data of different dimensions (signal strength: -120~-40dBm, temperature: -20~60℃, voltage: 200~240V, frequency: corresponding frequency band range) to the [0,1] interval, generating a 128-dimensional input feature vector to ensure the consistency and effectiveness of the neural network input data.

[0153] In this embodiment, the preset prediction model in step 173 adopts a hybrid neural network model of "input layer - CNN feature extraction layer - LSTM time capture layer - fully connected output layer", with a total of about 1.2 million parameters, balancing inference speed and prediction accuracy; wherein, the input layer: receives a 128-dimensional preprocessed feature vector, including the historical 50ms spectrum sequence (30-dimensional), temperature sequence (10-dimensional), voltage sequence (10-dimensional), local oscillator drift sequence (20-dimensional), PLL state features (8-dimensional), spectrum flatness features (10-dimensional), peak frequency features (10-dimensional), and loop filter voltage sequence (10-dimensional); the CNN feature extraction layer: includes 2 convolutional layers and 2 pooling layers. The first convolutional layer uses 32 3×3 convolutional kernels with a stride of 1 and the ReLU activation function to extract local spatial features of the spectral data (such as peak distribution and spectral concave locations). The first pooling layer is a 2×2 max pooling layer with a stride of 2 to reduce parameter dimensionality. The second convolutional layer uses 64 3×3 convolutional kernels with a stride of 1 and the ReLU activation function to deepen feature extraction. The second pooling layer is a 2×2 average pooling layer with a stride of 2, outputting a 64-dimensional feature vector. The LSTM temporal capture layer contains two LSTM layers, each with 64 hidden units and the tanh activation function. The weights of the forget gate, input gate, and output gate are optimized through training to effectively capture... The system calculates long-term dependencies in time series data (such as the cumulative trend of local oscillator drift and the gradual change pattern of mirror signal strength), outputting a 64-dimensional time series feature vector. The fully connected output layer consists of three layers: the first layer is 64→32 dimensions with ReLU activation; the second layer is 32→16 dimensions with ReLU activation; and the third layer is 16→4 dimensions with no activation function. It outputs the predicted mirror frequency (f_pred, in Hz), predicted signal strength (P_pred, in dBm), predicted local oscillator drift (Δf_lo_pred, in Hz), and prediction confidence (range [0,1]) for the next 20ms.

[0154] In this embodiment, the preset prediction model is obtained by training the preset neural network model using a preset historical feature data training set as follows:

[0155] Historical feature data training set construction: A hybrid dataset of laboratory simulation and field testing was used, with a sample size of ≥200,000 records. The laboratory simulation covered different types of electromagnetic interference (continuous interference, sudden interference, gradual interference), temperature gradient (-20℃~60℃, step size 5℃), and voltage fluctuation (±10%, step size 2%). The field testing selected three typical scenarios: urban buildings, tunnels, and remote mountainous areas, collecting ≥50,000 data points for each scenario to ensure the diversity and representativeness of the dataset. Training process: PyTorch framework was used for training, with a batch size of 64, 50 training epochs, an initial learning rate of 0.001, and the AdamW optimizer (weight decay coefficient) was used. To suppress overfitting, an early stopping strategy is adopted (training stops if the validation set error does not decrease for 5 consecutive rounds). The training objective is to minimize the mean squared error (MSE), ultimately achieving a prediction accuracy of ≥95% with a prediction error of ≤±50Hz for mirror frequency, ≤±2dB for signal strength, and ≥0.85 confidence level. The online update mechanism is as follows: the backend server summarizes the measured data and prediction error of the day every 24 hours, and adopts an incremental learning method (freezing the weights of CNN and LSTM layers and only fine-tuning the weights of fully connected layers) to update the model with new data, ensuring that the model adapts to environmental changes (such as the addition or removal of surrounding radio frequency equipment or changes in the electromagnetic environment) during long-term operation and maintains prediction accuracy.

[0156] In this embodiment, step 174, which dynamically adjusts the local oscillator frequency based on the image frequency, signal strength, and local oscillator drift over a preset future time period, may include:

[0157] The multi-dimensional data acquisition module uploads the preprocessed feature vector at a 1ms cycle. The neural network processing module receives and caches the data in real time, integrates the historical 50ms data every 5ms, generates a complete feature vector, and starts inference. The single inference time is ≤0.5ms, and the prediction results (f_pred, P_pred, Δf_lo_pred, Confidence) are output.

[0158] If the prediction confidence is greater than or equal to 0.85, and the predicted local oscillator drift Δflopred is greater than or equal to ±50Hz (it is predicted that this drift will cause the image frequency to shift by more than ±80Hz, close to the useful signal frequency band), the neural network immediately sends an early calibration command through the SPI interface. After receiving the command, the PLL module adjusts the local oscillator frequency according to the formula flo1=(frf+fif)+Δflopred (frf is the current FM useful signal frequency, and fif is the 450MHz intermediate frequency). Through the temperature compensation characteristics of the TCXO and the loop locking mechanism of the PLL, the stability of the local oscillator frequency after calibration is ensured to be ≤±0.5ppm. The calibration process is completed within 5ms to avoid the image frequency from overlapping with the useful signal. Within 1ms after calibration, the data acquisition module acquires the new local oscillator frequency and feeds it back to the neural network. If the actual drift is ≤±20Hz, the calibration is deemed valid; otherwise, a second calibration is triggered to ensure the accuracy of the local oscillator frequency.

[0159] Dynamically adjusting the mirror filter parameters includes:

[0160] The neural network calculates the optimal resonant parameters (equivalent capacitance and inductance values, corresponding cavity spacing and coupling coefficients) based on the predicted image frequency fpred and the frequency-attenuation characteristic curve of the filter. Based on the predicted signal strength Ppred, the attenuation depth is determined: 55dB when Ppred ≥ -65dBm (strong interference), 50dB when -75dBm ≤ Ppred < -65dBm (medium-intensity interference), and 45dB when Ppred < -75dBm (weak interference), achieving on-demand suppression. The resonant parameters and attenuation depth commands are sent to the image suppression filter via the I2C interface. The variable capacitor and inductor components inside the filter respond and adjust in ≤3ms time, ensuring the first center frequency of the stopband is precisely aligned with fpred. The attenuation depth is configured according to the command, ensuring effective suppression of the predicted image signal.

[0161] Dynamically adjust notch filtering parameters, including:

[0162] The neural network calculates the intermediate frequency notch point (IF point) of the image signal after frequency conversion (i.e., the frequency of the image signal in the 450MHz intermediate frequency link after downconversion by the mixer) according to the formula fiftrap=fpred-flo1 based on the calibrated local oscillator frequency flo1 and the predicted image frequency fpred. Through the notch parameter preset interface, the notch frequency (fiftrap) and notch depth (≥40dB when Ppred≥-70dBm, otherwise ≥35dB) are sent to the programmable notch filter 5ms in advance. The filter completes the parameter configuration and is ready in advance. When the image signal enters the intermediate frequency link with the useful signal, the notch filter immediately performs deep suppression on the signal at the fiftrap frequency to avoid residual interference affecting the subsequent upconversion process and ensure that the signal-to-noise ratio of the intermediate frequency signal is ≥22dB.

[0163] In an optional embodiment of the present invention, the method for processing the emergency broadcast signal may further include:

[0164] Every 5ms, the measured image frequency (fmeas) and signal strength (Pmeas) are compared with the predicted values ​​(fpred, Ppred), and the errors Δferr = |fmeas - fpred| and ΔPerr = |Pmeas - Ppred| are calculated. If Δferr > 100Hz or ΔPerr > 3dB, local weight fine-tuning of the model is triggered (only the last 10% of the weights of the LSTM layer are adjusted) to correct the prediction bias and ensure improved prediction accuracy in the next round. If the error exceeds the standard for three consecutive times, the data acquisition density is automatically increased (the sampling interval is shortened from 1ms to 0.5ms) to improve the timeliness of the feature vector.

[0165] The signal, after being purified by intermediate frequency, is converted to an idle frequency band supported by passive indoor distribution system (IDS) in the range of 800-900MHz by digital upconverter (DUC), with a frequency stability of ≤±2ppm. The signal is amplified to 10-15dBm by power amplifier. The AGC module monitors the output power in real time and dynamically adjusts the amplifier gain to ensure that the power fluctuation is ≤±0.5dB, which meets the input requirements of passive indoor distribution system.

[0166] In this embodiment, for indoor distributed antenna system (DAS) access and transmission, the following components are retained: full-band POI (800-3700MHz, independent FM signal port access, port isolation ≥80dB), wideband power divider (800MHz band insertion loss ≤0.3dB), coupler (coupling degree 10-20dB optional), leaky cable / antenna feeder (full-band leaky cable for tunnel scenarios, high-gain antenna feeder for building scenarios), and anti-interference components (public network signal branch notch filter, 800-900MHz FM band suppression ratio ≥50dB; core module metal shield, grounding resistance ≤4Ω). After the FM converted signal is combined through the POI, the power is evenly distributed through the power divider and coupler (power fluctuation of each branch link ≤±2dB), and then covered to the target area through the leaky cable / antenna feeder. The power supply end adopts a π-type filter + common-mode choke combination (PSRR≥65dB@1MHz) to ensure no interference with the public network signal transmission.

[0167] In this embodiment, for the receiver restoration process, the terminal has a built-in downconverter and SAW filter (87-108MHz, out-of-band attenuation >25dB@±2MHz offset) to restore the 800-900MHz transmission signal to the original FM signal. The receiving sensitivity is ≥1.2μV and the distortion is ≤0.3%. The audio media content is decoded according to the corresponding format. The terminal first performs digital signature verification (verifies the legality of the information). After the signature verification is passed, it is displayed through the built-in player or associated application. The smartphone terminal that supports the 3GPPR16 5G broadcast television standard has a system-level forced wake-up capability. Even if it is in a black screen or locked screen state, it can be woken up by the emergency broadcast signal and display information within ≤1s.

[0168] In this embodiment, the backend server for optimizing and adjusting the frequency band of the target frequency band signal during the upconversion process deploys a neural network processing module, a prediction database (storing historical prediction data and measured data, supporting fast query and tracing), a control command issuance interface (supporting multiple protocols such as I2C, SPI, and MQTT), and a visual monitoring interface (developed based on the Web, supporting real-time display of the image frequency prediction curve, the actual curve, the suppression parameter adjustment record, and the interference suppression effect index). The adjustment logic can be set as follows: the neural network dynamically adjusts the local oscillator frequency, image suppression filter parameters, and intermediate frequency notch parameters at a 5ms cycle to maintain an image suppression ratio ≥90dB, an intermediate frequency signal-to-noise ratio ≥22dB, and a public network signal EVM index ≤3%. In the event of sudden strong interference: if the predicted signal strength P_pred ≥ -60dBm (predicted as strong interference), the neural network immediately triggers a multi-level linkage suppression strategy: the attenuation depth of the image suppression filter is maximized to 60dB, the intermediate frequency notch depth is increased to 45dB, and at the same time, a command is sent through the MQTT interface to temporarily reduce the gain threshold of the AGC module (from 15dBm to 12dBm) to avoid amplifier saturation distortion caused by strong interference signals. The entire linkage response time is ≤3ms. In the event of fault tolerance: if the neural network prediction confidence is <0.85 (e.g., abnormal data acquisition or sudden environmental changes cause the model to be unable to predict accurately), the system automatically switches to the traditional "real-time monitoring - passive adjustment" mode (monitoring the image signal at 10ms intervals, triggering adjustment if it exceeds the limit) to ensure that the image suppression function is not interrupted; at the same time, an alarm message is pushed to the management personnel, and the system automatically switches back to the prediction-driven mode after the data returns to normal or the environment stabilizes. Data traceability and analysis: the backend database stores prediction data, adjustment records, and interference suppression effect data on a daily basis, and supports query and analysis by time, scenario, interference type, and other dimensions, providing data support for model optimization and parameter iteration.

[0169] like Figure 2 As shown, embodiments of the present invention also provide an emergency broadcast signal processing device 20, comprising:

[0170] Processing module 201 is used to acquire an emergency broadcast signal of a first frequency band to be propagated, wherein the emergency broadcast signal of the first frequency band to be propagated includes at least one piece of information to be propagated; to filter the emergency broadcast signal of the first frequency band to be propagated to obtain a target purified signal; to perform frequency conversion processing on the target purified signal to obtain a second frequency band signal supported by the passive indoor distribution system; wherein the minimum value of the frequency range of the second frequency band signal is greater than the maximum value of the frequency range of the first frequency band; and to merge the second frequency band signal with the public network signal in the passive indoor distribution system to obtain a merged target transmission signal.

[0171] The transceiver module 202 is used to evenly distribute the target transmission signal to multiple preset transmission branch links, and send it to the receiving end of the corresponding preset target area through the multiple preset transmission branch links for parsing to obtain the corresponding information to be transmitted.

[0172] Optionally, the emergency broadcast signal of the first frequency band to be transmitted is filtered to obtain the target purified signal, including:

[0173] The emergency broadcast signal in the first frequency band to be transmitted is subjected to bandpass filtering to obtain an intermediate signal;

[0174] The intermediate signal is amplified by low noise gain to obtain the target purified signal.

[0175] Optionally, the emergency broadcast signal in the first frequency band to be transmitted is bandpass filtered to obtain an intermediate signal, including:

[0176] Determine the first center frequency and first bandwidth of the emergency broadcast signal in the first frequency band;

[0177] Based on the first center frequency and the first bandwidth, the second-order bandpass parameters of the second-order bandpass filter are determined. The second-order bandpass parameters include the first inductance parameter and the first capacitance parameter of the resonant circuit in the second-order bandpass filter.

[0178] Based on the first center frequency, determine the lower cutoff frequency and the upper cutoff frequency;

[0179] Based on the second-order bandpass parameter, the signal that the emergency broadcast signal of the first frequency band passes between the lower cutoff frequency and the upper cutoff frequency is determined as the intermediate signal.

[0180] Optionally, the emergency broadcast signal in the first frequency band to be transmitted is bandpass filtered to obtain an intermediate signal, further comprising:

[0181] Determine the second center frequency and second bandwidth corresponding to the first image band;

[0182] Based on the second center frequency and the second bandwidth, the mirror filtering parameters of the band-stop filter are determined. The mirror filtering parameters include: the first resonant cavity parameters, the second resonant cavity parameters, and the coupling parameters of the first and second resonant cavities of the band-stop filter.

[0183] Based on the mirror filtering parameters, the intermediate signal is subjected to mirror suppression filtering, and the intermediate signal after mirror suppression filtering is output as the final intermediate signal.

[0184] Optionally, the target purification signal is subjected to at least two frequency conversion processes to obtain a second frequency band signal supported by the passive indoor distribution system, including:

[0185] The target purification signal is down-converted to obtain a mid-frequency signal in a different frequency band than the public network signal.

[0186] The intermediate frequency signal is up-converted to obtain the second frequency band signal supported by the passive indoor distribution system.

[0187] Optionally, the target purification signal is down-converted to obtain a mid-frequency signal in a different frequency band than the public network signal, including:

[0188] The first local oscillator signal is determined based on the target purification signal;

[0189] The first local oscillator signal is locked to obtain the locked first local oscillator signal.

[0190] The locked first local oscillator signal and the target purification signal are mixed to obtain the first mixed output signal;

[0191] The first mixing output signal is subjected to intermediate frequency filtering to obtain an intermediate frequency signal in a different frequency band from the public network signal.

[0192] Optionally, the intermediate frequency signal is up-converted to obtain a second frequency band signal supported by the passive indoor distribution system, including:

[0193] The intermediate frequency signal is up-converted to obtain the up-converted frequency band signal supported by the passive indoor distribution system. The up-converted frequency band signal includes multiple up-converted frequency signals of different frequencies.

[0194] The up-converted signal is filtered to obtain the up-converted filtered signal;

[0195] The signals of different frequency bands in the up-conversion filtered signal are subjected to multi-channel isolation processing to obtain the second frequency band signal.

[0196] Optionally, the second frequency band signal is combined with the public network signal within the passive indoor distribution system to obtain the combined target transmission signal, including:

[0197] By using a pre-set isolator, the second frequency band signal is physically isolated and combined with the existing public network signal in the passive indoor distribution system to obtain the combined target transmission signal.

[0198] It should be noted that this device corresponds to the method described above, and all implementations in the method embodiments described above are applicable to the embodiments of this device and can achieve the same technical effect. Further details are omitted in this embodiment.

[0199] Embodiments of the present invention also provide a computing device, including: a processor and a memory storing a computer program, wherein the computer program is executed by the processor to perform the methods described in the above embodiments.

[0200] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for processing emergency broadcast signals, characterized in that, Applied to a terminal, the method includes: Acquire an emergency broadcast signal of a first frequency band to be transmitted, wherein the emergency broadcast signal of the first frequency band to be transmitted includes at least one piece of information to be transmitted; The emergency broadcast signal of the first frequency band to be transmitted is filtered to obtain the target purified signal; The target purification signal is subjected to at least two frequency conversion processes to obtain a second frequency band signal supported by the passive indoor distribution system; the minimum value of the frequency range of the second frequency band signal is greater than the maximum value of the frequency range of the first frequency band. The second frequency band signal is combined with the public network signal in the passive indoor distribution system to obtain the combined target transmission signal; The target transmission signal is evenly distributed to multiple preset transmission branch links, and then transmitted to the receiving end of the corresponding preset target area through the multiple preset transmission branch links to obtain the corresponding information to be transmitted.

2. The method for processing emergency broadcast signals according to claim 1, characterized in that, The emergency broadcast signal in the first frequency band to be transmitted is filtered to obtain the target purified signal, including: The emergency broadcast signal in the first frequency band to be transmitted is subjected to bandpass filtering to obtain an intermediate signal; The intermediate signal is amplified by low noise gain to obtain the target purified signal.

3. The method for processing emergency broadcast signals according to claim 2, characterized in that, The emergency broadcast signal in the first frequency band to be transmitted is bandpass filtered to obtain an intermediate signal, including: Determine the first center frequency and first bandwidth of the emergency broadcast signal in the first frequency band; Based on the first center frequency and the first bandwidth, the second-order bandpass parameters of the second-order bandpass filter are determined. The second-order bandpass parameters include the first inductance parameter and the first capacitance parameter of the resonant circuit in the second-order bandpass filter. Based on the first center frequency, determine the lower cutoff frequency and the upper cutoff frequency; Based on the second-order bandpass parameter, the signal that the emergency broadcast signal of the first frequency band passes between the lower cutoff frequency and the upper cutoff frequency is determined as the intermediate signal.

4. The method for processing emergency broadcast signals according to claim 3, characterized in that, The emergency broadcast signal in the first frequency band to be transmitted is bandpass filtered to obtain an intermediate signal, and the signal further includes: Determine the second center frequency and second bandwidth corresponding to the first image band; Based on the second center frequency and the second bandwidth, the mirror filtering parameters of the band-stop filter are determined. The mirror filtering parameters include: the first resonant cavity parameters, the second resonant cavity parameters, and the coupling parameters of the first and second resonant cavities of the band-stop filter. Based on the mirror filtering parameters, the intermediate signal is subjected to mirror suppression filtering, and the intermediate signal after mirror suppression filtering is output as the final intermediate signal.

5. The method for processing emergency broadcast signals according to claim 1, characterized in that, The target purification signal is subjected to at least two frequency conversion processes to obtain a second frequency band signal supported by the passive indoor distribution system, including: The target purification signal is down-converted to obtain a mid-frequency signal in a different frequency band than the public network signal. The intermediate frequency signal is up-converted to obtain the second frequency band signal supported by the passive indoor distribution system.

6. The method for processing emergency broadcast signals according to claim 5, characterized in that, The target purification signal is down-converted to obtain a mid-frequency signal in a different frequency band than the public network signal, including: The first local oscillator signal is determined based on the target purification signal; The first local oscillator signal is locked to obtain the locked first local oscillator signal. The locked first local oscillator signal and the target purification signal are mixed to obtain the first mixed output signal; The first mixing output signal is subjected to intermediate frequency filtering to obtain an intermediate frequency signal in a different frequency band from the public network signal.

7. The method for processing emergency broadcast signals according to claim 5, characterized in that, The intermediate frequency signal is up-converted to obtain the second frequency band signal supported by the passive indoor distribution system, including: The intermediate frequency signal is up-converted to obtain the up-converted frequency band signal supported by the passive indoor distribution system. The up-converted frequency band signal includes multiple up-converted frequency signals of different frequencies. The up-converted signal is filtered to obtain the up-converted filtered signal; The signals of different frequency bands in the up-conversion filtered signal are subjected to multi-channel isolation processing to obtain the second frequency band signal.

8. The method for processing emergency broadcast signals according to claim 1, characterized in that, The second frequency band signal is combined with the public network signal within the passive indoor distribution system to obtain the combined target transmission signal, including: By using a pre-set isolator, the second frequency band signal is physically isolated and combined with the existing public network signal in the passive indoor distribution system to obtain the combined target transmission signal.

9. An emergency broadcast signal processing device, characterized in that, include: The processing module is used to acquire an emergency broadcast signal in a first frequency band to be propagated, wherein the emergency broadcast signal in the first frequency band to be propagated includes at least one piece of information to be propagated; to filter the emergency broadcast signal in the first frequency band to be propagated to obtain a target purified signal; to perform frequency conversion processing on the target purified signal to obtain a second frequency band signal supported by the passive indoor distribution system; wherein the minimum value of the frequency range of the second frequency band signal is greater than the maximum value of the frequency range of the first frequency band; and to merge the second frequency band signal with the public network signal in the passive indoor distribution system to obtain a merged target transmission signal. The transceiver module is used to evenly distribute the target transmission signal to multiple preset transmission branch links, and send it to the receiving end of the corresponding preset target area through the multiple preset transmission branch links for parsing to obtain the corresponding information to be transmitted.

10. A computing device, characterized in that, include: A processor, a memory storing a computer program, wherein the computer program, when executed by the processor, performs the method as described in any one of claims 1 to 8.

Images