Amplitude modulation broadcast co-frequency suppression method and device

Abstract

The invention belongs to the technical field of co-frequency suppression, and provides an amplitude modulation broadcast co-frequency suppression method and an implementation device, which are used for carrying out periodic segmentation suppression on illegal co-frequency broadcast signals. The method comprises the following steps: a sampling device receives and analyzes a remote signal and a local signal, and determines the frequency and phase of the remote signal through a signal processing algorithm; the amplitude modulation transmitter uses a phase-adjustable PLL external excitation signal, and the phase is independent and adjustable; a local carrier phase is dynamically moved in a set suppression period by using an adjustable phase excitation signal, and the phase shifting range and the stepping are adjustable; along with phase cyclic offset of local carrier signals, local medium wave coverage signals and far-end signals have a superposition counteracting area of partial periodic signals at any region receiving point, and the area can effectively reduce interference of signals in different places. According to actual measurement, in the application of the method, if the period is set to be 6 seconds, suppression of different-place same-frequency signals can be achieved within 2-4 seconds, the content of the different-place signals cannot be continuously and completely received, and finally the purpose of suppressing illegal same-frequency broadcast signals is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of co-frequency suppression, and in particular relates to a method and a device for realizing co-frequency suppression of amplitude modulation broadcasting. Background Art

[0002] In the field of medium and short wave broadcasting, avoiding the coverage of distant signals has always been a technical challenge. The propagation signals of medium and short wave broadcasting are extremely far, and local audiences are easily affected by harmful broadcast content from other places; Traditional co-channel suppression methods usually rely on increasing the co-channel transmission power, that is, suppressing harmful broadcast signals from other places by increasing the field strength of local signals. Although this method is effective to a certain extent, it is costly. In order to overcome the above problems, some technologies try to suppress the spread of harmful broadcast programs by transmitting the same frequency and inverted phase signals locally. The harmful broadcast signals from other places are collected at the remote end, and the phase inverted signals are transmitted locally to achieve efficient suppression of the broadcast signals from other places. However, this technology is affected by the coherent area of ​​the signal, and the suppression range is limited, so it is not effective in practical applications. Therefore, there is an urgent need for a new technical solution that can effectively suppress the interference of remote signals in different locations and improve the coverage quality of medium wave broadcasting without significantly increasing the technical cost. Summary of the invention

[0003] In order to solve the above technical problems, the present invention proposes a method for suppressing same-frequency but different-location amplitude modulation signals.

[0004] The present invention also provides a device for suppressing interference of same-frequency but different-location amplitude modulation signals. The technical solution adopted by the present invention is as follows: The present invention proposes a method for suppressing co-frequency and different-region signals, which can realize efficient suppression of illegal co-frequency broadcast signals in part of a cycle period, so that the content cannot be continuously received, thereby achieving the suppression purpose.

[0005] The method for suppressing the interference of co-frequency and non-local signals includes the following steps: firstly, sampling the signal, and detecting the frequency (Fr) and phase (Pr) of the non-local co-frequency signal after sampling; then, setting the cyclic suppression period T, the phase shift range Pm (pm<360) and the step value Pn according to the actual test results; determining the starting value Pb and the ending value Pe of the phase, the formula is: Pb = Pr + 180 - Pm / 2 and Pe = Pb + Pm; generating a local transmission excitation signal according to the detected non-local frequency Fr, and locking the phase to Pl; performing the following operations at each time interval t (t=T*Pn / Pm): in the positive cycle, if the local phase Pl is less than or equal to the phase ending value Pe, the transmitting phase Pl increases the step; in the reverse cycle, if the local phase Pl is greater than the starting phase Pb, the transmitting phase Pl decreases the step.

[0006] The present invention also proposes an AM broadcast co-frequency suppression device, comprising: a radio frequency sampling device, a host computer and a radio frequency signal generator; the device is used to apply the above-mentioned method for suppressing co-frequency and remote signal interference in AM broadcasting, and can achieve a stable, reliable and accurate output phase and can automatically adjust the phase according to requirements. The RF sampling device is located in the antenna tuning network part of the transmitting antenna, and the collected air RF signal is converted into frequency domain data and submitted to the controller; the host computer sets the cyclic suppression period, phase shift range and step value, phase start value and end value according to the actual test results based on the frequency and phase values ​​of the received signal, and performs phase shift at fixed time intervals.

[0007] The RF signal generator generates an AM broadcast transmitter excitation signal. The RF signal output by the RF signal generator is provided to the local AM transmitter as an excitation source. The transmitted local RF signal and the remote RF signal cancel each other out for part of the time in each phase shift cycle, thereby achieving the purpose of efficiently suppressing the remote signal for part of the time and failing to fully receive the remote broadcast content.

[0008] The technical effects achieved by the present invention are: The present invention realizes continuous cyclic stable movement of the carrier phase of the broadcast amplitude modulation transmission signal within a set range, and can achieve efficient suppression of illegal co-frequency broadcast signals during part of a cycle period, so that the content cannot be continuously and completely received, thereby achieving the purpose of suppression, avoiding the cost problem caused by increasing the transmission power in the traditional method, and providing an innovative harmful broadcast suppression method for the medium wave broadcasting field. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a flow chart of a method for suppressing interference of co-frequency signals in different locations according to embodiment 1 of the present invention; Figure 2It is a schematic diagram of signal reception and conversion in the present invention; Figure 3 : is a structural block diagram of a same-frequency suppression device provided according to an embodiment of the present invention Figure 4 It is the user setting interface of the host computer DETAILED DESCRIPTION

[0010] In order to make the purpose and advantages of the present invention more clearly understood, the present invention is specifically described below in conjunction with embodiments. It should be understood that the following text is only used to describe one or several specific embodiments of the present invention, and does not strictly limit the scope of protection of the specific claims of the present invention.

[0011] The present invention is proposed by the inventor based on the recognition and understanding of the following problems: In normal speech broadcasting, the human ear's ability to recognize speech is related to the number of syllables eliminated, based on the characteristics of the human ear receiving speech signals. In Mandarin Chinese, the average duration of a syllable is about 200-500 milliseconds. We tested the relationship between the number of syllables eliminated and the human ear's ability to understand speech information in normal speech broadcasting. In the first case, we periodically eliminated the last phoneme of each syllable in a normal speech broadcast, such as eliminating the last 50 milliseconds of each syllable, which may cause the final part of the syllable to be lost. However, in this case, the human ear may still be able to recognize most of the speech content, because the tone and final information in Mandarin Chinese is usually sufficient to express in the first half of the syllable. In the second case, we periodically eliminated two complete syllables in every four syllables, for example, in a speech, we eliminated two syllables (about 400-1000 milliseconds) in every four syllables (about 800-2000 milliseconds). This elimination pattern may significantly affect the intelligibility of speech, because the human ear relies on a continuous speech stream to predict and parse language, and the periodic elimination of some complete syllables may interrupt this continuity, making it difficult for the listener to track the speech stream and understand the semantics. Especially in pure language streams, this periodic elimination may cause a large amount of information loss, which seriously affects the listener's understanding of the content of the speech.

[0012] In summary, the human ear's ability to recognize speech content is affected by many factors under the influence of periodic elimination of syllables, including the number and duration of eliminated syllables. Eliminating a larger number of syllables may lead to a significant decrease in speech comprehension. In certain cases, if a certain length of syllables is periodically eliminated, the comprehensibility of the speech will be significantly reduced, making it difficult for the human ear to accurately recognize the speech information. Based on the characteristics of the human ear receiving speech signals, the present invention uses a 6-second cycle and eliminates syllables within a duration of 2-4 seconds per cycle, thereby achieving the purpose of efficiently suppressing illegal co-frequency broadcast signals within a specific period of the cycle to ensure that their content cannot be continuously received, thereby effectively suppressing co-frequency signal interference.

[0013] See attached Figure 1 and attached Figure 2 A method for suppressing the same frequency of an AM broadcast is provided, wherein the method is used to apply an AM broadcast same frequency suppression device to suppress the same frequency of a remote broadcast, and the method comprises the following steps: Perform signal sampling, and detect the frequency (Fr) and phase (Pr) of the same-frequency signal in different locations after sampling; Set the cyclic suppression period T, phase shift range Pm (pm<360) and step value Pn according to the actual test results. The cyclic suppression period T refers to the time required for the system to perform a complete suppression operation in the process of suppressing the same-frequency signal in different places. The appropriate T value can ensure that the signal in different places cannot be completely received by the receiver during the periodic suppression. The phase shift range Pm refers to the phase change range that the system can handle during the cycle. Step Pn refers to the step size or increment of the phase adjustment by the system in each cycle. A smaller step Pn can provide higher frequency resolution, which helps to more accurately identify and suppress interference signals; at the same time, too small a step Pn may also increase the processing time and affect the real-time performance of the system. The above parameters need to be set and adjusted according to the actual test results.

[0014] Determine the starting value Pb and ending value Pe of the phase. These two data determine the range of the local signal phase change. Pb is the starting point of the phase adjustment of the local transmission excitation signal. It is calculated based on the phase of the remote signal (Pr) and the manually set phase shift range (Pm), and the formula is: Pb = Pr + 180 - Pm / 2. The value of Pb determines the position where the local signal starts to shift the phase from the remote signal. If the Pb setting is inaccurate, the phase difference between the local signal and the remote signal may not be suitable, thereby reducing the suppression effect. Pe is the ending point of the phase adjustment of the local transmission excitation signal. It is obtained by adding the phase shift range Pm to Pb. The formula is Pe = Pb + Pm. The setting of Pe needs to ensure that the local signal can cover the entire phase shift range within the suppression cycle to ensure comprehensive suppression of the remote signal. If Pe is set too large or too small, the suppression cycle may be incomplete, affecting the suppression effect.

[0015] After determining the frequency Fr and phase information of the remote signal, a local transmission excitation signal is generated, whose frequency is locked to Fr and phase is Pl. The local signal phase Pl performs the following operations every time interval t: if the local phase Pl is less than or equal to the phase end value Pe in the positive cycle, the transmission phase Pl increases by Pn (= Pl + Pn); if the local phase Pl is greater than the starting phase Pb in the reverse cycle, the transmission phase Pl decreases by Pn (Pl = Pl - Pn). The time interval t is calculated based on the cyclic suppression period T, step Pn and phase shift range Pm, and the calculation formula is: t=T*Pn / Pm. In the positive cycle, if the phase Pl of the local signal is less than the end point phase Pe, Pl is increased by step Pn. In the reverse cycle, if Pl is greater than the starting point phase Pb, Pl is reduced by step Pn.

[0016] For news broadcasting program signals, the speed of news broadcasting is usually fast, generally up to 250 to 300 syllables per minute, that is, 4 to 6 syllables per second. According to the test results, when the cycle is set to 6 seconds, according to the normal voice broadcasting speed, 12 to 18 syllables can be suppressed within the phase cancellation (signal weakening) cycle. This suppression effect is enough to destroy the continuity of remote voice programs, making it impossible for the receiving end to continuously receive the complete program content; By cyclically adjusting the phase of the local carrier signal, within a certain range, at any geographical receiving point, there is a half-cycle signal superposition and cancellation zone between the local medium-wave coverage signal and the remote signal, effectively reducing interference from remote signals.

[0017] Attached Figure 3 This is a structural block diagram of a same-frequency signal suppression device provided according to an embodiment of the present invention. This embodiment is applicable to the case of performing cyclic phase shift on the phase of a radio frequency signal.

[0018] like Figure 3 As shown, a same-frequency signal suppression device provided in this embodiment includes: RF sampling equipment, host computer and RF signal generator; wherein the RF sampling equipment collects the RF signal transmitted by the input RF transmitter and transmits the output back to the host computer; the input end of the host computer is connected to the output end of the RF sampling equipment, and the output end of the host computer is connected to the input end of the RF signal generator; the output end of the RF signal generator is connected to the input end of the RF transmitter.

[0019] The RF sampling device collects the RF signal emitted by the input RF transmitter; when the local RF transmitter is not turned on, the RF sampling device uses its advantages of high sampling rate and wide bandwidth to directly sample the remote RF signal, thereby accurately measuring the frequency (Fr) and phase (Pr) of the remote signal, and outputs the collected RF signal back to the host computer.

[0020] Figure 4 The user interface provided for the host computer. The host computer provides an excitation signal for the transmitter, can adjust the output phase according to the settings, and can automatically adjust the phase offset in a cycle. The host computer receives the RF signal collected by the RF sampling device; the user sets the parameters of the start value Pb and the end value Pe and monitors the system through the software interface; according to the actual test results, the cyclic suppression period T, the phase shift range Pm (pm<360) and the step value Pn are set for the local RF signal; for example, the period is set to 6 seconds), and in each period, the local carrier phase is moved by the set step value (for example, 512, i.e. 11.25 degrees). Within a certain range, this cyclic movement of the phase can produce the effect of signal superposition and cancellation at the receiving point (mainly for language program signals); the host computer performs phase detection and analysis on the signal, and uses advanced signal processing algorithms to accurately detect the phase difference of the RF signal, and transmits the RF signal phase difference obtained by the detection and analysis to the RF signal generator.

[0021] The RF signal generator can generate a local RF signal to transmit to the RF transmitter, and can provide a locked frequency, phase shift range Pm (pm<360), cycle suppression period T and step value Pn for the RF signal channel. The RF signal generator includes: a constant temperature crystal oscillator circuit, whose output end is connected to the digital processing circuit, and is used to provide a clock signal for the digital processing circuit; a digital processing circuit, which is used to phase-modulate the generated carrier signal, generate a digital excitation signal and send the digital excitation signal to the output end for output; a filter output circuit, whose input end is connected to the output end of the digital processing circuit, and is used to convert the digital excitation signal into an analog excitation signal, and output it from the output end after filtering and amplification; a RF amplifier circuit, whose input end is connected to the output end of the filter output circuit in a one-to-one correspondence, and is used to amplify the power of the analog excitation signal to a preset power level.

[0022] The technical solution of the embodiment of the present invention is an index test system including a test signal demodulation module, an audio signal selection module and a radio frequency signal demodulation module, wherein the test signal demodulation module is connected to the input end of the audio signal selection module, the test signal demodulation module transmits the index test signal to the audio signal selection module, the output end of the audio signal selection module is connected to the input end of the radio frequency signal transmitter, switches between the broadcast audio signal and the index test signal, and transmits the signal to the radio frequency signal transmitter, the radio frequency signal demodulation module is connected to the output end of the radio frequency signal transmitter, and the radio frequency signal demodulation module receives the radio frequency signal transmitted by the radio frequency signal transmitter. The problem of unsatisfactory radio frequency signal effect coverage in the prior art is solved, and a system is provided that can achieve stable, reliable and accurate output phase and can cyclically move the phase as required, which reduces the radio frequency signal phase adjustment time and improves the radio frequency signal coverage effect.

[0023] This application can achieve efficient suppression of illegal co-frequency broadcast signals during part of a cycle period by realizing the continuous cyclic stable movement of the carrier phase of the broadcast AM transmission signal, so that its content cannot be continuously received, thereby achieving the purpose of suppression. Through the above technology, even if a local medium wave signal with a lower power is used for transmission, the voice content propagation of the remote co-frequency medium wave signal can be effectively interrupted, thereby achieving the purpose of suppressing the remote co-frequency broadcast signal. This method not only improves the coverage effect of the signal, but also reduces the dependence on high-power transmission equipment, reducing technical costs and energy consumption.

[0024] The above is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention. The structures, devices and operating methods not specifically described and explained in the present invention shall be implemented according to the conventional means in the art unless otherwise specified and limited.

Claims

1. A method for suppressing same-frequency signals in different places, characterized in that: The following steps are involved: First, the signal is sampled, and the frequency (Fr) and phase (Pr) of the remote co-frequency signal are detected after sampling; then, the cyclic suppression period T, phase shift range Pm (pm<360) and step value Pn are set according to the actual test results; the starting value Pb and ending value Pe of the phase are determined, and the formula is: Pb = Pr +180 - Pm / 2 and Pe = Pb + Pm; according to the detected remote frequency Fr, a local transmission excitation signal is generated, and the phase is locked to Pl; the following operations are performed at each time interval t (t=T*Pn / Pm): in the positive cycle, if the local phase Pl is less than or equal to the phase end value Pe, the transmission phase Pl increases the step; in the reverse cycle, if the local phase Pl is greater than the starting phase Pb, the transmission phase Pl decreases the step.

2. An AM broadcast same-frequency suppression device using the method for suppressing same-frequency signals in different places as claimed in claim 1, comprising: The radio frequency sampling device, the host computer and the radio frequency signal generator are characterized in that: the radio frequency sampling device is located in the antenna tuning network part of the transmitting antenna, and the collected radio frequency signals in the air are converted into frequency domain data and submitted to the controller; the host computer sets the cyclic suppression period, phase shift range and step value, phase start value and end value according to the actual test results through the frequency and phase values ​​of the received signal, and performs phase shift at fixed time intervals; the radio frequency signal output by the radio frequency signal generator is provided to the local amplitude modulation transmitter as an excitation source, and the transmitted local radio frequency signal and the remote radio frequency signal cancel each other out for part of the time in each phase shift period.

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