CN113132282B - Signal tracking demodulation device and method - Google Patents

Abstract

The application provides a signal tracking demodulation device and a method, wherein the device comprises: the system comprises a receiving antenna, a band-pass filter, a low-noise amplifier, a digital controlled oscillator, a mixer, a low-pass filter, a gain adjustable amplifier, an analog-to-digital converter and a digital processing module; after filtering out-of-band interference, amplifying, mixing and filtering high-frequency components of an FSK signal transmitted by a transmitting device in sequence, converting the FSK signal into a digital signal, and adjusting the gain of a gain-adjustable amplifier by a digital processing module according to the size of the digital signal; acquiring the current intermediate frequency according to the digital signals of a plurality of symbol periods, and determining data in a single symbol period according to the digital signals and the intermediate frequency of the single symbol period; and when the intermediate frequency exceeds the preset range, the local oscillation frequency of the numerical control oscillator is adjusted back, so that the intermediate frequency is in the preset range. The embodiment of the application is beneficial to meeting the requirements of high data rate and high reliability of implantable medical equipment communication.

Description

Signal tracking demodulation device and method

technical field

The present application relates to the technical field of digital signal processing, and in particular, to an apparatus and method for signal tracking and demodulation.

Background technique

With the development and progress of electronic technology, implantable medical equipment has become a hot field of global medical equipment research and development. Compared with traditional portable medical equipment, implantable medical equipment can detect various physiological indicators of the human body in real time, predict and treat diseases. It is more flexible and convenient to use. The implanted medical device transmits the detected signal to the external device through wireless communication. The modulation methods commonly used in the uplink are Frequency Shift Keying (FSK) and Amplitude Shift Keying (ASK). , ASK modulation has the advantage of low power consumption, but the anti-noise performance is poor, while the power consumption of FSK modulation is high, but the anti-noise performance is strong.

In order to reduce the problem of high power consumption of FSK modulation, the existing technology adopts the method of directly modulating the free-oscillating oscillator to generate the FSK modulation signal. However, this method is faced with the problem of frequency drift. In order to avoid frequency drift, some teams use injection Locking technology (Injection-Locked) realizes signal reception, however, injection locking technology requires the carrier frequency of the resonant frequency of the transmitting and receiving ends to remain relatively stable for a certain period of time, and the resonant frequencies of the transmitting and receiving ends need to be adjusted for a certain period of time. It is difficult to meet the high data rate and high reliability requirements of implantable medical equipment communication.

SUMMARY OF THE INVENTION

In view of the above technical problems, the present application provides a signal tracking and demodulation device and method, which is beneficial to meet the requirements of high data rate and high reliability for communication of implantable medical equipment.

In order to achieve the above purpose, a first aspect of the embodiments of the present application provides a signal tracking and demodulation device, including: a receiving antenna, a band-pass filter, a low-noise amplifier, a numerically controlled oscillator, a mixer, a low-pass filter, a gain Adjustable amplifiers, analog-to-digital converters and digital processing modules;

The receiving antenna is used to receive the FSK signal transmitted by the transmitting device, and transmit the FSK signal to the band-pass filter; the band-pass filter is used to filter the received FSK signal after out-of-band interference transmit to the low-noise amplifier; the low-noise amplifier is used to amplify the received FSK signal and then transmit it to the mixer; the mixer is used to amplify the received FSK signal with the The local oscillator signal output by the numerically controlled oscillator is mixed and transmitted to the low-pass filter; the low-pass filter is used to filter the received FSK signal to remove high-frequency components and transmit it to the analog-to-digital converter; The analog-to-digital converter is used to convert the received FSK signal into a digital signal, and transmit the digital signal to the digital processing module;

The digital processing module is used to adjust the gain of the adjustable gain amplifier according to the size of the received digital signal;

The digital processing module is further configured to obtain the current intermediate frequency frequency according to the digital signal of a preset number of symbol periods, and determine the data in the single symbol period according to the digital signal and the intermediate frequency of a single symbol period;

The digital processing module is further configured to call back the local oscillator frequency of the numerically controlled oscillator when the intermediate frequency frequency exceeds a preset range, so that the intermediate frequency frequency is within a second preset range.

In a feasible embodiment, in terms of adjusting the gain of the adjustable gain amplifier according to the size of the received digital signal, the digital processing module is specifically configured to:

At the end of each preset time period, obtain the maximum value and the minimum value of the digital signal within the preset time period, and obtain the peak-to-peak value according to the maximum value and the minimum value;

The peak-to-peak value is compared with a threshold value, and the gain of the adjustable gain amplifier is adjusted according to the comparison result.

In a feasible embodiment, in terms of obtaining the current intermediate frequency frequency according to the digital signal of a preset number of symbol periods, the digital processing module is specifically configured to:

Performing Fourier analysis on the digital signal of the preset number of symbol periods to obtain a first peak value and a second peak value;

The average value of the frequencies of the first peak and the second peak is obtained, and the average value is used to represent the intermediate frequency.

In a feasible embodiment, in terms of determining data in a single symbol period according to the digital signal and the intermediate frequency of a single symbol period, the digital processing module is specifically configured to:

performing Fourier analysis on the digital signal of the single symbol period to obtain a third peak value;

Compare the frequency of the third peak with the intermediate frequency, and if the frequency of the third peak is greater than the intermediate frequency, determine that the data in the single symbol period is 1; If the frequency is less than the intermediate frequency, it is determined that the data in the single symbol period is 0.

In a feasible embodiment, in terms of recalling the local oscillator frequency of the numerically controlled oscillator so that the intermediate frequency frequency is within the second preset range, the digital processing module is specifically used for:

According to the deviation of the local oscillator frequency of the numerically controlled oscillator relative to the frequency of the digital signal, changing the control word of the numerically controlled oscillator according to the first preset step size gradually recalls the local oscillator frequency of the numerically controlled oscillator, so that the intermediate frequency is within the second preset range.

In a feasible embodiment, the receiving antenna is further configured to receive a test signal transmitted by the transmitting device, and the test signal is used for the digital processing module to perform carrier acquisition and local oscillator frequency adjustment;

In terms of carrier acquisition and local oscillator adjustment, the digital processing module is specifically used for:

fixing the gain of the adjustable gain amplifier;

Starting with the first output frequency, the local oscillator frequency of the numerically controlled oscillator is adjusted with a second preset step size until the local oscillator frequency of the numerically controlled oscillator is adjusted to the second output frequency; the output frequency of the numerically controlled oscillator The range is within the first output frequency to the second output frequency;

During the adjustment process, the positions where the two amplitudes with the largest amplitudes appear are obtained, and the local oscillator frequency corresponding to the position where the largest amplitude appears for the first time among the two amplitudes is determined as the to-be-set local frequency of the numerically controlled oscillator. vibration frequency;

Obtain the carrier frequency of the transmitting device according to the to-be-set local oscillator frequency and the frequency saved with the maximum amplitude for the first time;

The local oscillator frequency of the numerically controlled oscillator is adjusted according to the carrier frequency of the transmitting device.

A second aspect of the embodiments of the present application provides a signal tracking and demodulation method, including:

Receive the digital signal sent by the analog-to-digital converter, the digital signal is obtained by converting the received FSK signal by the analog-to-digital converter, the FSK signal is sent by the transmitting device, received by the receiving antenna, and then undergoes band-pass filtering in turn Filter out out-of-band interference, low-noise amplifier amplification, mixer mixing, low-pass filter to filter out high-frequency components and then transmit to the analog-to-digital converter;

Adjust the gain of the adjustable gain amplifier according to the size of the digital signal;

Acquire the current intermediate frequency frequency according to the digital signal of a preset number of symbol periods, and determine the data in the single symbol period according to the digital signal of a single symbol period and the intermediate frequency frequency;

When the intermediate frequency frequency exceeds the preset range, the local oscillator frequency of the numerically controlled oscillator is recalled, so that the intermediate frequency frequency is within the second preset range.

In a feasible embodiment, the adjusting the gain of the adjustable gain amplifier according to the size of the received digital signal includes:

At the end of each preset time period, obtain the maximum value and the minimum value of the digital signal within the preset time period, and obtain the peak-to-peak value according to the maximum value and the minimum value;

The peak-to-peak value is compared with a threshold value, and the gain of the adjustable gain amplifier is adjusted according to the comparison result.

In a feasible embodiment, the obtaining the current intermediate frequency frequency according to the digital signal of a preset number of symbol periods includes:

Performing Fourier analysis on the digital signal of the preset number of symbol periods to obtain a first peak value and a second peak value;

The average value of the frequencies of the first peak and the second peak is obtained, and the average value is used to represent the intermediate frequency.

In a feasible embodiment, the determining the data in the single symbol period according to the digital signal and the intermediate frequency of the single symbol period includes:

performing Fourier analysis on the digital signal of the single symbol period to obtain a third peak value;

Compare the frequency of the third peak with the intermediate frequency, and if the frequency of the third peak is greater than the intermediate frequency, determine that the data in the single symbol period is 1; If the frequency is less than the intermediate frequency, it is determined that the data in the single symbol period is 0.

In a feasible embodiment, the callback of the local oscillator frequency of the numerically controlled oscillator, so that the intermediate frequency frequency is within a second preset range, includes:

According to the deviation of the local oscillator frequency of the numerically controlled oscillator relative to the frequency of the digital signal, changing the control word of the numerically controlled oscillator according to the first preset step size gradually recalls the local oscillator frequency of the numerically controlled oscillator, so that the intermediate frequency is within the second preset range.

In a feasible embodiment, before receiving the digital signal sent by the analog-to-digital converter, the method further includes:

receiving a test signal transmitted by the transmitting device, the test signal is used for carrier acquisition and local oscillator frequency adjustment;

fixing the gain of the adjustable gain amplifier;

Starting from the first output frequency, the local oscillator frequency of the numerically controlled oscillator is adjusted with a second preset step size until the local oscillator frequency of the numerically controlled oscillator reaches the second output frequency; a range within the first output frequency to the second output frequency;

During the adjustment process, the positions where the two amplitudes with the largest amplitudes appear are obtained, and the local oscillator frequency corresponding to the position where the largest amplitude appears for the first time among the two amplitudes is determined as the to-be-set local frequency of the numerically controlled oscillator. vibration frequency;

Obtain the carrier frequency of the transmitting device according to the to-be-set local oscillator frequency and the frequency saved with the maximum amplitude for the first time;

The local oscillator frequency of the numerically controlled oscillator is adjusted according to the carrier frequency of the transmitting device.

A third aspect of the embodiments of the present application further provides a computer storage medium, where the computer storage medium stores a computer program, the computer program includes program instructions, and the program instructions, when executed by a processor, cause the processor to execute As in all or part of the method of the second aspect.

The above-mentioned scheme of the present application includes at least the following beneficial effects:

It can be seen that in the embodiment of the present application, after filtering out out-of-band interference, amplifying, mixing, and filtering high-frequency components sequentially, the FSK signal transmitted by the transmitting device is converted into a digital signal, and the digital processing module is based on the digital signal. The size of the signal adjusts the gain of the gain-adjustable amplifier; obtains the current intermediate frequency frequency according to the digital signal of a preset number of symbol periods, and determines the frequency within the single symbol period according to the digital signal and the intermediate frequency of a single symbol period In the case that the intermediate frequency frequency exceeds the preset range, the local oscillator frequency of the numerically controlled oscillator is recalled, so that the intermediate frequency frequency is within the second preset range. In this way, the carrier frequency of the FSK signal transmitted by the transmitting device can be tracked in real time, and the demodulation of the FSK signal whose carrier frequency is relatively fast and greatly changed can be realized without interfering with the signal reception, which is beneficial to meet the high data communication requirements of implantable medical equipment. efficiency and high reliability requirements.

Description of drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only These are some embodiments of the present application. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

FIG. 1 is a schematic structural diagram of an apparatus for signal tracking and demodulation provided by an embodiment of the present application;

FIG. 2 is a schematic structural diagram of a transmitter according to an embodiment of the present application;

3 is a schematic diagram of the working characteristics of an analog-to-digital converter provided by an embodiment of the present application;

FIG. 4 is a schematic diagram of a workflow of a transmitting device provided by an embodiment of the present application;

FIG. 5 is a schematic flowchart of a signal tracking solution method provided by an embodiment of the present application.

Detailed ways

In order to make those skilled in the art better understand the solutions of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only The embodiments are part of the present application, but not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the scope of protection of the present application.

The appearances of the terms "comprising" and "having" and any variations thereof in the specification, claims and drawings of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units is not limited to the listed steps or units, but optionally also includes unlisted steps or units, or optionally also includes For other steps or units inherent to these processes, methods, products or devices. In addition, the terms "first", "second", "third", etc. are used to distinguish different objects and not to describe a specific order.

Please refer to FIG. 1. FIG. 1 is a schematic structural diagram of a signal tracking and demodulation apparatus provided by an embodiment of the present application. As shown in FIG. 1, the signal tracking and demodulation apparatus includes: a receiving antenna, a band-pass filter, and a low noise amplifier , numerically controlled oscillators, mixers, low-pass filters, gain-adjustable amplifiers, analog-to-digital converters and digital processing modules. The output frequency of the numerically controlled oscillator is in the range of 420MHz to 500MHz, the low-pass filter bandwidth is 10MHz, the gain adjustable amplifier is 3dB, the bandwidth is 10MHz, and the gain is up to 50dB. The sampling frequency of the converter is fixed at 40MHz. As shown in Figure 3, the analog-to-digital converter sampling at 40MHz has a maximum frequency of only 20MHz. The sampling process folds the FSK signal frequency. Therefore, the input frequency higher than 20MHz will be folded to Within 20MHz, for example: 45MHz signal, the output frequency is 5MHz after sampling by the analog-to-digital converter.

Wherein, in the specific embodiment of the present application, the above-mentioned receiving antenna is used to receive the FSK signal transmitted by the transmitting device. Please refer to FIG. 2. FIG. 2 is a schematic structural diagram of a transmitting device according to an embodiment of the application. The transmitting device includes: a baseband processing module, a numerically controlled oscillator, a power amplifier, a band-pass filter, and a transmitting antenna, and each part is connected in sequence. , the data collected by the implantable medical equipment is encoded, filtered, selected by the carrier frequency and FSK modulation coefficient through the baseband processing module, to realize the establishment of data frames and data correction, and to generate control signals, which are transmitted to the numerically controlled oscillator. Frequency modulation is performed to generate a frequency modulation signal, the frequency modulation signal is amplified by the power amplifier, and then the harmonic components are filtered out by the band-pass filter, and the final FSK signal is radiated by the transmitting antenna. The output frequency range of the transmitter is 430MHz to 490MHz, the transmit power is 0dBm, the data rate is 2Mbps, and the frequency offset is 2MHz. In some examples, the transmitting device can be understood as an implantable medical device, and in other examples, the transmitting device can also be understood as a transmitter of the implantable medical device.

The receiving antenna transmits the received FSK signal to the band-pass filter of the signal tracking demodulation device, the band-pass filter is used to filter out the out-of-band interference of the received FSK signal, and then transmits it to the low noise amplifier; The low noise amplifier is used to amplify the received FSK signal and then transmit it to the mixer; the mixer is used to combine the FSK signal sent by the low noise amplifier with the local oscillator output by the numerical control oscillator of the tracking demodulation device The signal is mixed, and then the mixed FSK signal is transmitted to a low-pass filter; the low-pass filter is used to filter out the high-frequency components of the FSK signal sent by the mixer, and then sent to the analog-to-digital converter ; analog-to-digital converter, used to convert the FSK signal sent by the low-pass filter into a digital signal, and transmit the digital signal to the digital processing module for amplitude and frequency detection and processing, as well as decoding processing, etc., and finally complete the transmission of the transmitting device. data reception.

Specifically, the digital processing module may be an FPGA (Field Programmable Gate Array, Field Programmable Gate Array) module or other integrated digital module, which is used to adjust the gain of the adjustable gain amplifier according to the size of the received digital signal.

In a feasible implementation manner, in terms of adjusting the gain of the adjustable gain amplifier according to the size of the received digital signal, the digital processing module is specifically configured to:

At the end of each preset time period, obtain the maximum value and the minimum value of the digital signal within the preset time period, and obtain the peak-to-peak value according to the maximum value and the minimum value;

The peak-to-peak value is compared with a threshold value, and the gain of the adjustable gain amplifier is adjusted according to the comparison result.

Among them, in the specific embodiment of the present application, the preset time period may be 5uS. Since the two registers will store the maximum value and the minimum value in the 5uS digital signal, the digital processing module will read the maximum value and the minimum value stored in the register every 5uS. The difference between the minimum value, the maximum value and the minimum value is the peak-to-peak value. The threshold value can be set according to the actual situation. If the peak-to-peak value is higher than the threshold, the gain of the gain adjustable amplifier will be reduced. Then increase the gain of the adjustable gain amplifier so that the peak-to-peak value is about half the reference voltage of the analog-to-digital converter. The gain of the adjustable gain amplifier is adjusted every 5uS, which is beneficial to keep the signal strength before the analog-to-digital converter stable, and is not affected by the strength of the FSK signal received by the receiving antenna. Optionally, after each gain adjustment is completed, it is necessary to "clear" the maximum and minimum registers, and assign the average value of the recorded maximum and minimum values to these two registers, so that the registers can record the next Maximum and minimum within 5uS.

Specifically, the digital processing module is further configured to acquire the current intermediate frequency according to the digital signal of a preset number of symbol periods, and determine the data in the single symbol period according to the digital signal and the intermediate frequency of a single symbol period.

In a feasible implementation manner, in terms of obtaining the current intermediate frequency frequency according to the digital signal of a preset number of symbol periods, the digital processing module is specifically configured to:

Performing Fourier analysis on the digital signal of the preset number of symbol periods to obtain a first peak value and a second peak value;

The average value of the frequencies of the first peak and the second peak is obtained, and the average value is used to represent the intermediate frequency.

Among them, in the specific embodiment of the present application, the preset number of symbol periods can be customized, for example: N symbol periods, two peaks are obtained by performing Fourier analysis on the digital signal in the N symbol periods, and the first The first peak is recorded as the first peak, the second peak is recorded as the second peak, the position (frequency) of the first peak is F ₀ , and the position of the second peak is F ₁ , corresponding to '0' respectively and the frequency of the '1' signal, to obtain the average Fc of the frequencies of the two peaks, and the average Fc is the estimated value of the current intermediate frequency. In this scheme, in the process of receiving the FSK signal sent by the transmitting device, the digital processing module still estimates the intermediate frequency every 5uS, and the accuracy can reach 0.2MHz.

In a feasible implementation manner, in terms of determining data in a single symbol period according to the digital signal and the intermediate frequency of a single symbol period, the digital processing module is specifically configured to:

performing Fourier analysis on the digital signal of the single symbol period to obtain a third peak value;

Compare the frequency of the third peak with the intermediate frequency, and if the frequency of the third peak is greater than the intermediate frequency, determine that the data in the single symbol period is 1; If the frequency is less than the intermediate frequency, it is determined that the data in the single symbol period is 0.

Among them, in the specific embodiment of the present application, the digital processing module performs a Fourier analysis on the digital signal of a single symbol period every 0.5uS, and obtains a peak value, which is denoted as the third peak value, and its position is Fd. The frequency Fd is compared with the intermediate frequency frequency Fc, where Fd>Fc means that the data in the single symbol period is 1, and Fd<Fc means that the data in the single symbol period is 0. The single symbol period may be one of the above N symbol periods, and the determined "1" or "0" is the data finally decoded by the signal tracking and demodulation apparatus.

Specifically, the digital processing module is further configured to call back the local oscillator frequency of the numerically controlled oscillator when the intermediate frequency frequency exceeds a preset range, so that the intermediate frequency frequency is within the second preset range.

In an optional implementation manner, in terms of recalling the local oscillator frequency of the numerically controlled oscillator so that the intermediate frequency frequency is within the second preset range, the digital processing module is specifically configured to:

According to the deviation of the local oscillator frequency of the numerically controlled oscillator relative to the frequency of the digital signal, changing the control word of the numerically controlled oscillator according to the first preset step size gradually recalls the local oscillator frequency of the numerically controlled oscillator, so that the intermediate frequency is within the second preset range.

Wherein, in the specific embodiment of the present application, the first preset range is 5MHz±1MHz, the first preset step size may be 0.2MHz, and the second preset range is 5MHz±0.3MHz. The intermediate frequency Fc exceeds the first preset range, indicating that the local oscillator frequency of the numerically controlled oscillator of the tracking demodulation device has a large deviation from the received signal carrier. If the intermediate frequency Fc is larger than the range of 5MHz±1MHz, every Reduce the control word of the numerical control oscillator by 0.2MHz for 10uS to adjust the local oscillator frequency of the numerical control oscillator until the intermediate frequency Fc enters 5MHz±0.3MHz. On the contrary, if the intermediate frequency Fc is smaller than the range of 5MHz±1MHz , the control word of the numerically controlled oscillator is increased by 0.2MHz every 10uS. After each calculation of the intermediate frequency Fc, it is detected whether the intermediate frequency Fc exceeds the first preset range, and when it exceeds, the intermediate frequency Fc is adjusted in time to enter the second preset range, which is conducive to the automatic tracking of the FSK signal.

In a feasible implementation manner, the receiving antenna is further configured to receive a test signal transmitted by the transmitting device, and the test signal is used for the digital processing module to perform carrier acquisition and local oscillator frequency adjustment;

In terms of carrier acquisition and local oscillator adjustment, the digital processing module is specifically used for:

fixing the gain of the adjustable gain amplifier;

Starting from the first output frequency, the local oscillator frequency of the numerically controlled oscillator is adjusted with a second preset step size until the local oscillator frequency of the numerically controlled oscillator reaches the second output frequency; a range within the first output frequency to the second output frequency;

During the adjustment process, the positions where the two amplitudes with the largest amplitudes appear are obtained, and the local oscillator frequency corresponding to the position where the largest amplitude appears for the first time among the two amplitudes is determined as the to-be-set local frequency of the numerically controlled oscillator. vibration frequency;

Obtain the carrier frequency of the transmitting device according to the to-be-set local oscillator frequency and the frequency saved with the maximum amplitude for the first time;

The local oscillator frequency of the numerically controlled oscillator is adjusted according to the carrier frequency of the transmitting device.

Among them, in the specific embodiment of the present application, the first output frequency is the lowest value of the output frequency range of the exponentially controlled oscillator, that is, 420MHz, the second output frequency is the highest value of the output frequency range of the exponentially controlled oscillator, that is, 500MHz, and the second The preset step size is 10MHz, and the LO frequency to be set is the LO frequency that needs to be set for the exponentially controlled oscillator. At the beginning of communication, the signal tracking and demodulation device does not determine the operating frequency of the transmitting device. Therefore, the transmitting device usually needs to transmit 15uS continuous '0' data before transmitting a normal frame. For 15uS continuous '0' data, the above test signal (which can be understood as a fixed preamble) refers to the 15uS continuous '0' data, and the transmission workflow of the transmitting device is shown in FIG. 4 .

The signal tracking demodulation device uses the time of 15uS to capture the carrier frequency of the transmitting device and adjust the local oscillator frequency of the local numerical control oscillator. Specifically, the digital processing module firstly fixes the gain of the adjustable gain amplifier to 25dB, and then increases the local oscillator frequency of the numerically controlled oscillator in steps of 10MHz from 420MHz, and waits for about 0.1uS after each increase. After stabilization, collect the 1uS signal for Fourier analysis, obtain the spectrum, save the maximum frequency and amplitude, until the local oscillator frequency of the numerical control oscillator is increased to 500MHz.

Please refer to Table 1. Table 1 is the frequency record after Fourier analysis is performed on the carrier frequency, the local oscillator frequency, the intermediate frequency frequency and the sampling frequency of the analog-to-digital converter in the process of adjusting the local oscillator frequency from 420MHz in this application:

Table 1

A total of 9 frequencies and 9 amplitudes are recorded in Table 1. It takes 9.8uS to calculate the two amplitudes with the largest amplitudes among the 9 amplitudes and their positions. The corresponding local oscillator frequencies and preset carrier frequencies of these two positions The difference (450MHz in Table 1) is not more than 10MHz. It can be seen that among the 9 amplitudes, the largest two appear in the serial number 4 and the serial number 5, and the corresponding local oscillator frequencies are 450MHz and 460MHz respectively, that is, the first occurrence The local oscillator frequency corresponding to the position of the maximum amplitude is 450MHz, and the 450MHz is the local oscillator frequency to be set for the numerically controlled oscillator. The frequency saved at the position where the maximum amplitude first appears is the difference between the preset carrier frequency and the local oscillator frequency. Assuming that the difference is 4MHz, the transmitter can be calculated based on the difference of 4MHz and the to-be-set local oscillator frequency of 450MHz. The carrier frequency is 454MHz, so the capture operation of the carrier frequency is completed, and the local oscillator frequency of the numerically controlled oscillator is roughly adjusted according to the captured carrier frequency, so that the intermediate frequency frequency in the process of receiving the test signal enters the first preset range, that is, In the range of 5MHz±1MHz, after the local oscillator frequency is roughly adjusted, the digital processing module starts to perform the gain adjustment operation according to the maximum and minimum values recorded in the register every 5uS. It can be seen from Table 1 that the test signal has not been attenuated through the low-pass filter at the positions corresponding to No. 3 to No. 5, and the recorded frequencies are all within the range of ±10MHz, and the position where the maximum amplitude occurs for the first time corresponds to The IF frequency of , is consistent with the frequency obtained after sampling by the analog-to-digital converter, so the carrier frequency can be calculated more accurately at this position. After transmitting the 15uS test signal, the transmitting device starts to transmit the normal frame, that is, the FSK signal, and the signal tracking and demodulation device performs the aforementioned tracking and demodulation operation.

It can be seen that the signal tracking and demodulation device provided by the embodiment of the present application converts the FSK signal transmitted by the transmitting device into a digital signal after sequentially filtering out out-of-band interference, amplifying, mixing, and filtering out high-frequency components, The digital processing module adjusts the gain of the adjustable gain amplifier according to the size of the digital signal; obtains the current intermediate frequency according to the digital signal of a preset number of symbol periods, and obtains the current intermediate frequency according to the digital signal of a single symbol period and the intermediate frequency Determining data in the single symbol period; when the intermediate frequency exceeds a preset range, recalling the local oscillator frequency of the numerically controlled oscillator so that the intermediate frequency is within a second preset range. In this way, the carrier frequency of the FSK signal transmitted by the transmitting device can be tracked in real time, and the demodulation of the FSK signal whose carrier frequency is relatively fast and greatly changed can be realized without interfering with the signal reception, which is beneficial to meet the high data communication requirements of implantable medical equipment. efficiency and high reliability requirements.

Based on the descriptions of the device embodiments shown in FIGS. 1-4, please refer to FIG. 5. FIG. 5 is a schematic flowchart of a signal tracking and demodulation method provided by an embodiment of the present application. As shown in FIG. 5, the following steps are included:

S51. Receive a digital signal sent by an analog-to-digital converter;

Wherein, in the specific embodiment of the present application, the digital signal is obtained by converting the received FSK signal by the analog-to-digital converter, and the FSK signal is sent by the transmitting device, received by the receiving antenna, and then undergoes band-pass filtering in turn. Filter out out-of-band interference, low-noise amplifier amplification, mixer mixing, low-pass filter to filter out high-frequency components and then transmit to the analog-to-digital converter;

S52, adjust the gain of the adjustable gain amplifier according to the size of the digital signal;

S53, obtaining the current intermediate frequency frequency according to the digital signal of a preset number of symbol periods, and determining the data in the single symbol period according to the digital signal and the intermediate frequency frequency of a single symbol period;

S54. When the intermediate frequency exceeds a preset range, recall the local oscillator frequency of the numerically controlled oscillator so that the intermediate frequency falls within the second preset range.

In a feasible implementation manner, the adjusting the gain of the adjustable gain amplifier according to the size of the received digital signal includes:

At the end of each preset time period, obtain the maximum value and the minimum value of the digital signal within the preset time period, and obtain the peak-to-peak value according to the maximum value and the minimum value;

The peak-to-peak value is compared with a threshold value, and the gain of the adjustable gain amplifier is adjusted according to the comparison result.

In a feasible implementation manner, the obtaining the current intermediate frequency frequency according to the digital signal of a preset number of symbol periods includes:

Performing Fourier analysis on the digital signal of the preset number of symbol periods to obtain a first peak value and a second peak value;

The average value of the frequencies of the first peak and the second peak is obtained, and the average value is used to represent the intermediate frequency.

In a feasible implementation manner, the determining the data in the single symbol period according to the digital signal and the intermediate frequency of the single symbol period includes:

performing Fourier analysis on the digital signal of the single symbol period to obtain a third peak value;

Compare the frequency of the third peak with the intermediate frequency, and if the frequency of the third peak is greater than the intermediate frequency, determine that the data in the single symbol period is 1; If the frequency is less than the intermediate frequency, it is determined that the data in the single symbol period is 0.

In a feasible implementation manner, the callback of the local oscillator frequency of the numerically controlled oscillator, so that the intermediate frequency frequency is within a second preset range, includes:

According to the deviation of the local oscillator frequency of the numerically controlled oscillator relative to the frequency of the digital signal, changing the control word of the numerically controlled oscillator according to the first preset step size gradually recalls the local oscillator frequency of the numerically controlled oscillator, so that the intermediate frequency is within the second preset range.

In a feasible implementation manner, before receiving the digital signal sent by the analog-to-digital converter, the method further includes:

receiving a test signal transmitted by the transmitting device, the test signal is used for carrier acquisition and local oscillator frequency adjustment;

fixing the gain of the adjustable gain amplifier;

Starting from the first output frequency, the local oscillator frequency of the numerically controlled oscillator is adjusted with a second preset step size until the local oscillator frequency of the numerically controlled oscillator reaches the second output frequency; a range within the first output frequency to the second output frequency;

During the adjustment process, the positions where the two amplitudes with the largest amplitudes appear are obtained, and the local oscillator frequency corresponding to the position where the largest amplitude appears for the first time among the two amplitudes is determined as the to-be-set local frequency of the numerically controlled oscillator. vibration frequency;

Obtain the carrier frequency of the transmitting device according to the to-be-set local oscillator frequency and the frequency saved with the maximum amplitude for the first time;

The local oscillator frequency of the numerically controlled oscillator is adjusted according to the carrier frequency of the transmitting device.

For the specific implementation of the above steps S51-S54, reference may be made to the relevant descriptions of the embodiments shown in Figs.

An embodiment of the present application further provides a computer storage medium, where the computer storage medium stores a computer program, the computer program includes program instructions, and the program instructions, when executed by a processor, cause the computer to execute the implementation as shown in FIG. 5 . all or part of the method.

Exemplarily, the computer program of the computer storage medium includes computer program code, which may be in source code form, object code form, executable file or some intermediate form, and the like. The computer storage medium may include: any entity or device capable of carrying the computer program code, a recording medium, a U disk, a removable hard disk, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM, Read-Only Memory), Random Access Memory (RAM, Random Access Memory), electric carrier signal, telecommunication signal and software distribution medium, etc.

The embodiments of the present application have been introduced in detail above, and the principles and implementations of the present application are described in this paper by using specific examples. The descriptions of the above embodiments are only used to help understand the methods and core ideas of the present application; at the same time, for Persons of ordinary skill in the art, based on the idea of the present application, will have changes in the specific implementation manner and application scope. In summary, the contents of this specification should not be construed as limitations on the present application.

Claims (6)

1. A signal tracking demodulation apparatus, characterized in that the apparatus comprises: the system comprises a receiving antenna, a band-pass filter, a low-noise amplifier, a digital controlled oscillator, a mixer, a low-pass filter, a gain adjustable amplifier, an analog-to-digital converter and a digital processing module;

the receiving antenna is used for receiving the FSK signal transmitted by the transmitting device and transmitting the FSK signal to the band-pass filter; the band-pass filter is used for filtering out-of-band interference of the received FSK signal and transmitting the FSK signal to the low noise amplifier; the low-noise amplifier is used for amplifying the received FSK signal and transmitting the amplified FSK signal to the mixer; the frequency mixer is used for mixing the received FSK signal with the local oscillator signal output by the numerical control oscillator and then transmitting the mixed signal to the low-pass filter; the low-pass filter is used for filtering high-frequency components of the received FSK signal and transmitting the FSK signal to the analog-to-digital converter; the analog-to-digital converter is used for converting the received FSK signal into a digital signal and transmitting the digital signal to the digital processing module;

the digital processing module is used for adjusting the gain of the gain-adjustable amplifier according to the size of the received digital signal;

the digital processing module is further configured to obtain a current intermediate frequency according to the digital signals of a preset number of symbol periods, and determine data in a single symbol period according to the digital signals of the single symbol period and the intermediate frequency;

the digital processing module is further configured to adjust back a local oscillator frequency of the digitally controlled oscillator when the intermediate frequency exceeds a preset range, so that the intermediate frequency is within a second preset range;

in terms of adjusting the gain of the gain-adjustable amplifier according to the received digital signal, the digital processing module is specifically configured to:

when each preset time period is finished, acquiring the maximum value and the minimum value of the digital signal in the preset time period, and obtaining a peak value according to the maximum value and the minimum value;

comparing the peak-to-peak value with a threshold value, and adjusting the gain of the gain-adjustable amplifier according to the comparison result so that the peak-to-peak value is half of the reference voltage of the analog-to-digital converter;

in determining data within a single symbol period from the digital signal and the intermediate frequency for the single symbol period, the digital processing module is specifically configured to:

performing Fourier analysis on the digital signal of the single symbol period to obtain a third peak value;

comparing the frequency of the third peak value with the intermediate frequency, and if the frequency of the third peak value is greater than the intermediate frequency, determining that the data in the single symbol period is 1; and if the frequency of the third peak value is smaller than the intermediate frequency, determining that the data in the single symbol period is 0.

2. The apparatus of claim 1, wherein in obtaining the current if frequency from the digital signal over a preset number of symbol periods, the digital processing module is specifically configured to:

performing Fourier analysis on the digital signals of the preset number of symbol periods to obtain a first peak value and a second peak value;

and acquiring the average value of the frequencies of the first peak value and the second peak value, and representing the intermediate frequency by using the average value.

3. The apparatus according to claim 1 or 2, wherein in adjusting back the local oscillator frequency of the digitally controlled oscillator so that the intermediate frequency is within a second preset range, the digital processing module is specifically configured to:

and according to the deviation condition of the local oscillation frequency of the numerical control oscillator relative to the frequency of the digital signal, changing the control word of the numerical control oscillator according to a first preset step length to gradually adjust back the local oscillation frequency of the numerical control oscillator so as to enable the intermediate frequency to be in a second preset range.

4. The apparatus of claim 3, wherein the receiving antenna is further configured to receive a test signal transmitted by the transmitting apparatus, and the test signal is used for carrier acquisition and local oscillation frequency adjustment by the digital processing module;

in terms of carrier capture and local oscillator adjustment, the digital processing module is specifically configured to:

fixing the gain of the gain adjustable amplifier;

starting from the first output frequency, adjusting the local oscillation frequency of the numerical control oscillator by a second preset step length until the local oscillation frequency of the numerical control oscillator reaches a second output frequency; the output frequency of the digitally controlled oscillator ranges from the first output frequency to the second output frequency;

in the adjusting process, acquiring positions of two amplitudes with the maximum amplitude, and determining the local oscillation frequency corresponding to the position of the maximum amplitude in the two amplitudes as the local oscillation frequency to be set of the numerical control oscillator;

obtaining the carrier frequency of the transmitting device according to the local oscillation frequency to be set and the frequency stored by the maximum amplitude value appearing for the first time;

and adjusting the local oscillation frequency of the numerical control oscillator according to the carrier frequency of the transmitting device.

5. A method for signal tracking demodulation, the method comprising:

receiving a digital signal sent by an analog-to-digital converter, wherein the digital signal is obtained by converting a received FSK signal by the analog-to-digital converter, the FSK signal is sent by a transmitting device, received by a receiving antenna, sequentially filtered by a band-pass filter to remove out-of-band interference, amplified by a low-noise amplifier, mixed by a mixer and filtered by a low-pass filter to remove high-frequency components, and then transmitted to the analog-to-digital converter;

adjusting the gain of the gain adjustable amplifier according to the size of the digital signal;

acquiring a current intermediate frequency according to the digital signals of a preset number of symbol periods, and determining data in a single symbol period according to the digital signals and the intermediate frequency of the single symbol period;

when the intermediate frequency exceeds a preset range, the local oscillation frequency of the numerical control oscillator is adjusted back so that the intermediate frequency is in a second preset range;

the adjusting the gain of the gain-adjustable amplifier according to the magnitude of the digital signal includes:

when each preset time period is finished, acquiring the maximum value and the minimum value of the digital signal in the preset time period, and obtaining a peak value according to the maximum value and the minimum value;

comparing the peak-to-peak value with a threshold value, and adjusting the gain of the gain-adjustable amplifier according to the comparison result so that the peak-to-peak value is half of the reference voltage of the analog-to-digital converter;

the determining data in a single symbol period according to the digital signal and the intermediate frequency of the single symbol period comprises:

performing Fourier analysis on the digital signal of the single symbol period to obtain a third peak value;

comparing the frequency of the third peak value with the intermediate frequency, and if the frequency of the third peak value is greater than the intermediate frequency, determining that the data in the single symbol period is 1; and if the frequency of the third peak value is smaller than the intermediate frequency, determining that the data in the single symbol period is 0.

6. The method of claim 5, wherein the obtaining a current intermediate frequency from the digital signal of a preset number of symbol periods comprises:

performing Fourier analysis on the digital signals of the preset number of symbol periods to obtain a first peak value and a second peak value;

and acquiring the average value of the frequencies of the first peak value and the second peak value, and representing the intermediate frequency by using the average value.

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