Medium-short wave signal monitor

Abstract

The utility model discloses a medium-short wave signal monitor which comprises a front-end channel unit, an ADC sampling and preprocessing unit and a main control unit. The front-end channel unit comprises a first-stage filter, a second-stage filter, a pre-amplifier and an adjustable attenuator which are connected in sequence; the medium-short wave antenna is connected to the first-stage filter; the first-stage filter is a medium-short wave low-pass filter, and the second-stage filter comprises a parallel branch formed by the medium-short wave low-pass filter and a short wave high-pass filter; the input end of the parallel branch is connected with the output end of the primary filter through the change-over switch, and the output end of the parallel branch is connected with the input end of the pre-amplifier through the change-over switch; the ADC sampling and preprocessing unit comprises an ADC circuit and an FPGA circuit which are connected in sequence; the adjustable attenuator is connected with the ADC circuit, and the FPGA circuit is connected with the main control unit. According to the utility model, medium-wave and short-wave frequency switching monitoring and medium-wave and short-wave signal full-band direct acquisition with a high signal-to-noise ratio and a high dynamic range are realized.

Description

Technical Field

[0001] This utility model relates to the field of radio signal monitoring technology, and in particular to a medium and shortwave signal monitoring instrument. Background Art

[0002] Medium and shortwave broadcasting refers to radio broadcasting services conducted within a specific frequency range, including:

[0003] Medium wave (MW) broadcasting typically refers to broadcasting on frequencies between 300 kHz and 3 MHz. MW broadcasting uses ground waves for propagation, resulting in limited coverage during the day, but reaching greater distances at night due to ionospheric reflection. MW broadcasting is primarily used for national or regional programming, such as news, educational, and entertainment content, and is one of the earliest forms of broadcasting.

[0004] Shortwave (SW) broadcasting covers frequencies between 2.3 MHz and 26.1 MHz. This band is characterized by its ability to utilize ionospheric reflection to achieve long-distance and even global signal transmission. Therefore, shortwave broadcasting is ideal for international broadcasting, enabling the transmission of information directly to audiences abroad across national borders. Shortwave broadcasting is also frequently used for emergency communications, communication among amateur radio enthusiasts, and broadcasting services in special circumstances.

[0005] With the development of technology, the requirements for monitoring medium and shortwave signals are becoming increasingly stringent. Not only is real-time and accurate acquisition of multiple signals necessary, but high sensitivity, high dynamic range, and anti-interference capabilities are also required. Traditional medium and shortwave signal monitoring equipment typically uses discrete hardware modules to process signals in different frequency bands. However, this design has some limitations:

[0006] Signal interference problem: Due to the significant differences in the transmission mechanisms and power of medium wave and short wave signals, in traditional designs, the large signal of medium wave may cause serious interference to the small signal of short wave, resulting in inaccurate measurement of short wave signal.

[0007] Limited dynamic range: Traditional ADCs (analog-to-digital converters) are usually unable to process large and small signals simultaneously, especially in wide bandwidths, where they are prone to overload or signal loss, thus limiting the dynamic range of the system.

[0008] Therefore, how to provide a medium- and shortwave signal monitoring instrument that optimizes signal reception and improves monitoring performance is a technical problem that urgently needs to be solved by those skilled in the art. Utility Model Content

[0009] In response to the aforementioned research status, this invention provides a medium- and short-wave signal monitoring instrument that enables frequency switching monitoring between medium and short waves, as well as direct acquisition of medium- and short-wave signals across the entire band with high signal-to-noise ratio and high dynamic range.

[0010] This utility model provides a medium- and short-wave signal monitoring instrument, comprising: a front-end channel unit, an ADC sampling and preprocessing unit, and a main control unit; wherein...

[0011] The front-end channel unit includes a first-stage filter, a second-stage filter, a preamplifier, and an adjustable attenuator connected in sequence; a mid-wave and short-wave antenna is connected to the first-stage filter; the first-stage filter is a mid-wave and short-wave low-pass filter, and the second-stage filter includes a parallel branch composed of a mid-wave low-pass filter and a short-wave high-pass filter; the input terminal of the parallel branch is connected to the output terminal of the first-stage filter through a switching switch, and the output terminal of the parallel branch is connected to the input terminal of the preamplifier through a switching switch;

[0012] The ADC sampling and preprocessing unit includes an ADC circuit and an FPGA circuit connected in sequence; the adjustable attenuator is connected to the ADC circuit, and the FPGA circuit is connected to the main control unit.

[0013] Preferably, the first-stage filter is a 30MHz low-pass filter, the mid-wave low-pass filter is a 2MHz low-pass filter, and the short-wave high-pass filter is a 2MHz high-pass filter.

[0014] The primary filter uses a 30MHz low-pass filter to effectively remove high-frequency interference signals above 30MHz, preventing these interferences from entering subsequent circuits and avoiding ADC overload or nonlinear distortion. By removing high-frequency components, the subsequent preamplifier, adjustable attenuator, and ADC circuitry are protected, ensuring they operate within a safe operating range.

[0015] The secondary filter, through a parallel design of a 2MHz low-pass filter and a 2MHz high-pass filter, effectively separates medium-wave (535kHz to 1605kHz) and short-wave (above 1700kHz) signals, avoiding mutual interference. This design allows medium-wave and short-wave signals to be processed independently within their respective frequency bands, improving measurement accuracy and reliability. By selecting different filter paths via a switch, the monitoring frequency band can be flexibly switched according to actual needs, adapting to different application scenarios.

[0016] A preamplifier can amplify weak radio frequency signals, ensuring that the signal is not lost due to attenuation during transmission, especially when dealing with long-distance or low-power signals, thus improving the system's sensitivity.

[0017] The adjustable attenuator automatically adjusts the attenuation value according to the actual signal strength, ensuring that the signal input to the ADC is neither overloaded nor too weak, thereby achieving a dynamic range of over 120dB to adapt to signals of varying strengths. By adjusting the attenuation value, it prevents large signals from overloading the ADC, ensuring the stability and reliability of the system.

[0018] Preferably, the ADC circuit uses an ADC chip with a 10-bit width and a 105MHz sampling frequency, which helps to achieve the technical effects of high signal-to-noise ratio and high dynamic range.

[0019] Preferably, the receiving frequency band of the medium-shortwave antenna is 500KHz-30MHz.

[0020] Preferably, the system also includes a power control unit electrically connected to the ADC sampling and preprocessing unit and the main control unit. The power control unit has external main and backup dual AC power input interfaces, both for connecting to a 220V AC input power module. The dual AC power input interfaces provide redundant power supply functionality, ensuring that the backup power supply can immediately take over in the event of a main power failure, guaranteeing continuous system operation and enhancing system reliability and stability. Even during power switching, the system can maintain uninterrupted operation, avoiding monitoring interruptions due to power failures.

[0021] Preferably, the system also includes a BeiDou positioning unit, which is connected to the FPGA circuit. Through the BeiDou positioning unit, the monitor can obtain current location information, facilitating the recording of the geographical location of the signal source in mobile monitoring scenarios and aiding in the analysis of signal propagation paths and coverage areas.

[0022] Preferably, it also includes a REF clock management unit, which is electrically connected to the ADC circuit.

[0023] Preferably, the FPGA circuit is connected to the main control unit via a USB interface. The USB interface is a standard peripheral interface, which facilitates connection with various main control systems and simplifies system integration and maintenance.

[0024] Compared with the prior art, this utility model has the following advantages:

[0025] Optimized signal reception and improved measurement performance: By employing a mid-wave / short-wave switching filter, a low-noise preamplifier, and a digitally controlled adjustable attenuator in the front-end channel unit, this invention effectively separates mid-wave and short-wave signals, reduces external interference, and improves signal quality and stability. This design significantly enhances measurement accuracy and reliability, especially when processing signals in complex electromagnetic environments.

[0026] Achieving full-band direct sampling of mid-to-shortwave signals with high signal-to-noise ratio and high dynamic range: By selecting a 16-bit wide, 105MHz sampling rate ADC chip, not only is full-band direct sampling of the 500kHz–30MHz frequency band achieved, but also high signal-to-noise ratio and spurious-free dynamic range are provided. The front-end channel unit combined with the ADC configuration enables the device to maintain stable performance when processing both large and small signals, significantly improving the system's dynamic range and anti-interference capability. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the medium and shortwave signal monitoring instrument provided in this embodiment of the utility model;

[0029] Figure 2 This is a schematic block diagram of the front-end channel unit provided in this embodiment of the utility model;

[0030] Figure 3 This is a switch-based filter logic circuit diagram provided in this embodiment of the present invention;

[0031] Figure 4 This is a logic circuit diagram of the medium and shortwave signal monitoring instrument provided in this embodiment of the utility model;

[0032] Figure 5 This is a logic circuit diagram of the medium and shortwave signal monitoring instrument provided in this embodiment of the utility model;

[0033] Figure 6 This is a logic circuit diagram of the power control unit provided in an embodiment of the present invention;

[0034] Figure 7 This is a logic circuit diagram of the REF clock management unit provided in this embodiment of the present invention. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] like Figure 1 As shown, this utility model discloses a medium-shortwave signal monitoring instrument, comprising: a front-end channel unit, an ADC sampling and preprocessing unit, and a main control unit; the front-end channel unit includes a first-stage filter, a second-stage filter, a preamplifier, and an adjustable attenuator connected in sequence; a medium-shortwave antenna is connected to the first-stage filter; the first-stage filter is a medium-shortwave low-pass filter, and the second-stage filter includes a parallel branch composed of a medium-wave low-pass filter and a short-wave high-pass filter; the input end of the parallel branch is connected to the output end of the first-stage filter through a switching switch, and the output end of the parallel branch is connected to the input end of the preamplifier through a switching switch; the ADC sampling and preprocessing unit includes an ADC circuit and an FPGA circuit connected in sequence; the adjustable attenuator is connected to the ADC circuit, and the FPGA circuit is connected to the main control unit.

[0037] like Figure 2-3 As shown, the switching of the single-pole double-throw switch is achieved by controlling pins A and B, which can meet the switching of different filters. The switching operation between the preamplifier branch and the through branch is the same as that of the filter circuit, as shown in Table 1.

[0038] Table 1. Control Switching Signals for Single-Pole Double-Throw Switches

[0039] Control pin A Control pin B Input switch signal path Output switch signal path low level high level Signal Input - Signal Output 1 Signal Input 1 - Signal Output high level low level Signal Input - Signal Output 2 Signal Input 2 - Signal Output

[0040] The segmented filter employs frequency switching between medium wave and short wave, thus avoiding the influence of large medium wave signals on short wave signal testing. The preamplifier improves the receiving sensitivity of the equipment, achieving a noise floor of ≤-135dBm / Hz; the 50dB adjustable attenuator, adjustable in 1dB, enables a dynamic range of 120dB. Large signals can be tested up to +20dBm.

[0041] In one embodiment, the primary filter is a 30MHz low-pass filter, the mid-wave low-pass filter is a 2MHz low-pass filter, and the short-wave high-pass filter is a 2MHz high-pass filter.

[0042] In this embodiment, a 30MHz low-pass filter is used to filter out interference signals outside the 30MHz range of the shortwave band; a 2MHz low-pass filter is used to filter out interference signals outside the 1750kHz range of the medium wave band, suppressing shortwave signals and optimizing medium wave signal measurement; and a 2MHz high-pass filter is used to filter out interference signals at the lower end of the shortwave band, suppressing medium wave signals and optimizing shortwave signal measurement.

[0043] In one embodiment, the preamplifier is a 20dB low-noise amplifier to improve sensitivity and enhance small-signal measurements. A digitally controlled adjustable attenuator of 50dB in 1dB steps is used to improve large-signal measurements.

[0044] In one embodiment, the ADC circuit uses an ADC chip with a 10-bit width and a 105MHz sampling frequency.

[0045] In this embodiment, the ADC selected is model SC1269, with an SNR of 76.8dB and an SFDR of 88dB. When the monitoring host is working, the AD sampling clock operates at 100MHz, the signal-to-noise ratio is >70dB, and 16-bits are oversampled at 30MHz to ensure no data loss. The full-band shortwave signal from 500KHz to 30MHz enters the FPGA for subsequent preprocessing.

[0046] The FPGA used is an FMK230T8 chip, containing 600 DSP cores and 325 Block RAM. After logic optimization, it can meet the requirements of 20-channel AM reception and 2-channel spectrum acquisition. It can simultaneously demodulate and perform narrowband spectrum analysis on ≥8 channels of AM signals, and package the audio and spectrum data for transmission to the main control unit via USB 3.0 interface.

[0047] The 16-bit full-band sampled data output by the ADC chip is copied 16 times after entering the FPGA, such as... Figure 4 As shown, the signal enters the 16-channel DDC down-conversion mixing logic unit for spectrum shifting. The data shifted to zero frequency then undergoes a two-stage CIC interpolation filter to reduce the sampling rate from 100MHz to 40kHz. The 40kHz low-speed signal then passes through a CIC compensation filter and a half-band low-pass filter before being transmitted to the host computer main control system unit via a USB 3.0 interface.

[0048] DDS is a direct frequency synthesizer, implemented directly using an IP core provided by an FPGA. The IP core drives a 100MHz clock, has a phase control word width of 48 bits, and can achieve a frequency resolution of 3.55e-07Hz.

[0049] CIC is a comb decimation filter with an order of 7 and a decimation rate of 1250. It downsamples a signal with a sampling rate of 100MHz to 80KSps.

[0050] The HBF is a half-band filter that further reduces the sampling rate to 40KSps for processing by the subsequent host computer demodulation module. The half-band filter has 100 orders, with a passband ripple of 0.01dB and a stopband rejection of 90dB.

[0051] In this embodiment, as Figure 2 As shown, the front-end channel unit also includes an ADC driver, a wideband ADC driver, which converts single-ended to differential to drive the subsequent ADC chip.

[0052] In one embodiment, such as Figure 5 As shown, the receiving frequency band of the medium and shortwave antenna is 500KHz-30MHz.

[0053] In one embodiment, such as Figure 5 As shown, it also includes a power control unit electrically connected to the ADC sampling and preprocessing unit and the main control unit. The power control unit has external main and backup dual AC power input interfaces, both used to connect to a 220V AC input power module. In this embodiment, the power control unit converts the 12V power output from the 220V power module into 5V / 3.3V / 1.8V voltages according to the power requirements of the monitoring host, and distributes them to the various circuit units inside the monitoring host.

[0054] The logic circuit diagram of the power control unit is as follows: Figure 6 As shown, the implementation method is easily understood by those skilled in the art.

[0055] In one embodiment, such as Figure 5 As shown, it also includes a BeiDou positioning unit, which is connected to the FPGA circuit. This embodiment can provide system time synchronization, outputting latitude and longitude coordinates and a 1PPS clock signal. The satellite signal receiving sensitivity is approximately -155dBm.

[0056] In one embodiment, such as Figure 5 As shown, it also includes a REF clock management unit, which is electrically connected to the ADC circuit. This embodiment uses a clock generation chip to synchronize the internal VCO chip with the internal TCXO and the externally input clock to generate a 100MHz sampling clock signal for the ADC chip to sample.

[0057] like Figure 7 As shown, after the 20MHz TCXO outputs to the PLL clock chip, it outputs a 65MHz sampling clock, which is provided to the ADC chip. Finally, the ADC chip outputs a 65MHz clock and parallel data, which are provided to the FPGA for data sampling.

[0058] In one embodiment, the FPGA circuit is connected to the main control unit via a USB interface.

[0059] In one embodiment, the main control system unit includes two identical ARM main processors: an RK3588 chip, an 8-core (4 A76 cores + 4 A55 cores) ARM architecture, a clock speed of 2.4 GHz, and a computing power of up to 6 TOPS. Main processor 1 primarily implements signal processing-related functions such as RF front-end control, audio processing, indicator calculation, spectrum and waterfall plot curve operation, while main processor 2 is mainly used to run various services, including database management, web front-end services, graph management, statistical analysis, and data storage.

[0060] The main processor 2 is equipped with a 256GB M.2 solid-state drive and 8GB of DDR4 memory, which meets current computing performance and file storage needs.

[0061] In one embodiment, the circuit structure is encapsulated inside the chassis. The rear panel of the chassis features dual network ports, ensuring that data transmission and local parameter configuration are independent. It also includes USB and HDMI display interfaces for device debugging. If a problem occurs, an external keyboard, mouse, USB flash drive, and display terminal can be connected for troubleshooting without opening the chassis. In addition, an N-type 50-ohm standard signal interface is provided, along with a reserved signal input port and an SMA interface. The SMA interface can be connected to a Beidou positioning antenna to display the device's location and is also used for frequency calibration.

[0062] The present invention provides a detailed description of a medium- and short-wave signal monitoring instrument. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

[0063] In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, without necessarily requiring or implying any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

Claims

1. A medium- and shortwave signal monitoring instrument, characterized in that, include: The system comprises a front-end channel unit, an ADC sampling and preprocessing unit, and a main control unit; among which, The front-end channel unit includes a first-stage filter, a second-stage filter, a preamplifier, and an adjustable attenuator connected in sequence; a mid-wave and short-wave antenna is connected to the first-stage filter; the first-stage filter is a mid-wave and short-wave low-pass filter, and the second-stage filter includes a parallel branch composed of a mid-wave low-pass filter and a short-wave high-pass filter; the input terminal of the parallel branch is connected to the output terminal of the first-stage filter through a switching switch, and the output terminal of the parallel branch is connected to the input terminal of the preamplifier through a switching switch; The ADC sampling and preprocessing unit includes an ADC circuit and an FPGA circuit connected in sequence. The adjustable attenuator is connected to the ADC circuit, and the FPGA circuit is connected to the main control unit.

2. The medium- and shortwave signal monitoring instrument according to claim 1, characterized in that, The first-stage filter is a 30MHz low-pass filter, the mid-wave low-pass filter is a 2MHz low-pass filter, and the short-wave high-pass filter is a 2MHz high-pass filter.

3. The medium- and shortwave signal monitoring instrument according to claim 1, characterized in that, The ADC circuit uses an ADC chip with a 10-bit width and a 65MHz sampling frequency.

4. A medium- and shortwave signal monitoring instrument according to claim 1, characterized in that, The receiving frequency band of the medium- and short-wave antenna is 500KHz-30MHz.

5. A medium- and shortwave signal monitoring instrument according to claim 1, characterized in that, It also includes a power control unit electrically connected to the ADC sampling and preprocessing unit and the main control unit. The power control unit has external main and backup dual AC power input interfaces, both of which are used to connect to a 220V AC input power module.

6. A medium- and shortwave signal monitoring instrument according to claim 1, characterized in that, It also includes a BeiDou positioning unit, which is connected to the FPGA circuit.

7. A medium- and shortwave signal monitoring instrument according to claim 1, characterized in that, It also includes a REF clock management unit, which is electrically connected to the ADC circuit.

8. A medium- and shortwave signal monitoring instrument according to claim 1, characterized in that, The FPGA circuit is connected to the main control unit via a USB interface.

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