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CN113765545A - Bluetooth receiver demodulation system and method - Google Patents

Bluetooth receiver demodulation system and method Download PDF

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CN113765545A
CN113765545A CN202111027429.6A CN202111027429A CN113765545A CN 113765545 A CN113765545 A CN 113765545A CN 202111027429 A CN202111027429 A CN 202111027429A CN 113765545 A CN113765545 A CN 113765545A
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CN113765545B (en
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傅永生
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Shanghai Institute of Microwave Technology CETC 50 Research Institute
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    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B5/00—Near-field transmission systems, e.g. inductive or capacitive transmission systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B5/00—Near-field transmission systems, e.g. inductive or capacitive transmission systems
    • H04B5/40—Near-field transmission systems, e.g. inductive or capacitive transmission systems characterised by components specially adapted for near-field transmission
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Abstract

The invention provides a demodulation system and a demodulation method of a Bluetooth receiver, which comprise the following modules: module M1: the Bluetooth receiver comprises a Bluetooth receiver, wherein a radio frequency signal is subjected to down-conversion to obtain an analog signal, the analog signal is subjected to ADC (analog to digital converter) sampling to obtain a digital sampling rate signal, the digital sampling rate signal is subjected to rate conversion to be converted into an integral multiple of the carrier central frequency of the analog signal to obtain a digital signal, the digital signal subjected to rate conversion is subjected to related multiplication with the delay of the digital signal, and then low-pass filtering is performed; module M2: and demodulating the Bluetooth receiver by dynamically setting time delay. The invention improves the existing demodulation algorithm of the Bluetooth receiver, fundamentally improves the performance of the receiver, greatly improves the performance by 4-5dB under the condition of not increasing the complexity, and can configure the demodulation delay; the calculation amount is small, and the cost is low.

Description

Bluetooth receiver demodulation system and method
Technical Field
The invention relates to the technical field of Bluetooth receivers, in particular to a system and a method for demodulating a Bluetooth receiver.
Background
In short-range wireless communication, bluetooth is becoming an increasingly important communication means. Many devices using bluetooth technology, such as bluetooth headsets, bluetooth speakers, etc., are widely used in people's daily life. However, as such applications become more widespread, the quality of such wireless connection technology is increasingly required. It is desirable to have transmission distances extending from 1 meter to 10 meters or more, connection times shorter, more reliable, and rates from hundreds of K to 1M or more. Thus, improvements to conventional bluetooth receivers are urgently needed.
The existing Bluetooth standard adopts GFSK modulation, and the Bluetooth receiver mainly comprises a digital front end, a demodulation module, a synchronization module, a signal detection module and the like. The demodulation methods can be generally classified into three types: a method called FM-to-AM (frequency modulation to amplitude modulation) conversion, phase shift discrimination and zero crossing rate detection. The first method, namely the FM-to-AM method, has low implementation cost and good performance, and becomes the mainstream demodulation method of most of the existing Bluetooth products. In order to reduce the radio frequency cost, the bluetooth adopts a low intermediate frequency technology, for a baseband signal with a bandwidth of 1M, after down-conversion, the carrier central frequency is 5MHz, the ADC adopts a 32MHz sampling rate, in order to change the baseband signal into an integral multiple of 5MHz, 32MHz needs to be subjected to rate conversion into 20MHz, the signal after the rate conversion is subjected to related multiplication with the delay thereof, then low-pass filtering is performed, and the output phase is judged, so that the transmitted signal can be recovered. Then, synchronization and decision are performed.
In a related bluetooth receiver patent document, for example, chinese patent publication No. CN109361493A, a bluetooth receiving method, a bluetooth receiver, and a bluetooth device are disclosed, which include: receiving a baseband signal, analyzing load data and cyclic redundancy CRC (cyclic redundancy check) information corresponding to the load data, obtaining a CRC result according to the CRC information, estimating the signal quality of the load data, processing the load data with the CRC error according to the signal quality when the CRC error is detected and the retransmission times are not less than a preset retransmission threshold, and finishing retransmission. By setting a retransmission threshold, when receiving a data packet each time, determining a CRC (cyclic redundancy check) result and signal quality, when the retransmission times are not less than the preset retransmission times, processing error data and finishing retransmission, thereby reducing retransmission, reducing transmission delay and improving the real-time property of communication. This patent document only changes some retransmission strategies through the CRC detection result and the threshold value, and does not improve the performance of the receiver in terms of the demodulation algorithm.
The existing bluetooth receiver patent document, such as chinese invention patent document with publication number CN111988108A, discloses an anti-interference high-precision signal synchronization method based on access codes in a bluetooth receiver, which takes the access codes agreed by both parties as local training sequences; sampling a received signal, continuously carrying out delay difference operation on two sampling values separated by one code element period, obtaining a sequence to be correlated according to the result of the delay difference operation, carrying out sliding correlation operation on the sequence to be correlated and a local training sequence, searching a peak value of a correlation value, and taking a sampling moment corresponding to the peak value as an initial position of an access code to realize frame timing synchronization.
The existing bluetooth receiver patent document, such as chinese patent publication No. CN104270177A, discloses an adaptive bluetooth receiver, which sets various parameters of the receiver, including the channel bandwidth of a filter, by detecting the existence of adjacent channel interference, and generates the gain settings of the high-frequency preamplifier and the gain-controllable amplifier by automatic gain control operation, and the receiver has the advantages of being adaptive, efficient, and low in power consumption. That is, the related patents improve the performance of the receiver in terms of CRC detection, synchronization, interference detection, and the like.
Chinese patent publication No. CN112398770A discloses a bluetooth low-power consumption multiphase frequency shift keying modulation/demodulation method and apparatus thereof, the method includes grouping input binary data streams, each group includes a plurality of bits; mapping the binary data stream into a phase sequence, wherein a binary data group is mapped into a phase in a predetermined phase set by gray coding; and modulating the phase sequence into a phase signal by utilizing a phase waveform obtained by integrating a preset frequency waveform. The baseband signal obtained based on the phase signal is used for Bluetooth low-power-consumption signal transmission, and can keep higher power amplification efficiency, lower demodulation complexity and higher multipath interference resistance performance while improving the BLE wireless transmission rate.
In view of the above related technologies, the inventor thinks that the device method basically does not improve the algorithm of the demodulator itself, has poor performance, is difficult to configure the delay size of demodulation, and has a large calculation amount and a high cost.
Disclosure of Invention
In view of the defects in the prior art, the present invention provides a demodulation system and method for a bluetooth receiver.
The invention provides a demodulation system of a Bluetooth receiver, which comprises the following modules:
module M1: the Bluetooth receiver comprises an ADC, wherein radio frequency signals are subjected to down-conversion to obtain analog signals, the analog signals are subjected to ADC sampling to obtain digital sampling rate signals, the digital sampling rate signals are subjected to rate conversion to be converted into integral multiples of carrier central frequency of the analog signals to obtain digital signals, the digital signals subjected to rate conversion are subjected to related multiplication with delay of the digital signals, and then low-pass filtering is carried out;
module M2: and demodulating the Bluetooth receiver by dynamically setting time delay.
Preferably, the module M1 further includes: the delay multiplication is expressed as:
Figure BDA0003243831410000031
wherein v isoutRepresenting the result of the delay multiplication; f represents the center frequency of the low intermediate frequency carrier; t represents time; theta represents the initial phase of the carrier; τ represents time delay;
Figure BDA0003243831410000032
represents the phase;
after low pass filtering, the multiple frequency is filtered out, yielding:
Figure BDA0003243831410000033
AMoutrepresenting an amplitude value of the signal after filtering;
namely, it is
Figure BDA0003243831410000034
Preferably, the module M2 includes: demodulation is performed by dynamically setting the time delay:
if it is set up
Figure BDA0003243831410000035
Substituting equation (6) yields:
Figure BDA0003243831410000036
therein
Figure BDA0003243831410000037
Wherein, InRepresenting a transmitting side binary bit; the subscript n denotes the time of the digitally sampled signal;
if it is set up
Figure BDA0003243831410000038
Substituting equation (6) yields:
Figure BDA0003243831410000039
therein
Figure BDA00032438314100000310
Due to amplitude values AM of the output signaloutDependent on phase
Figure BDA00032438314100000311
While phase position
Figure BDA00032438314100000312
Again depending on the time delay τ, and hence the phase
Figure BDA00032438314100000313
And time delay tau.
Preferably, the system also comprises a bluetooth transmitting end processing module, the bluetooth transmitting end processing module comprises a MAC layer, a physical layer, a CRC, a DAC and a modulation module, and assuming that the size of a user data packet output from the MAC layer is an assumed bit, the digital processing entering the physical layer firstly needs to be added with a CRC check of a pre-check bit and becomes a preset bit; for a non-coding system, framing operation is carried out to form a prediction bit frame; and the predicted bit frame is sent to a modulation module for GFSK modulation to generate a GFSK signal, and the GFSK signal enters an analog channel through a DAC to be processed and sent to an air interface.
Preferably, the system further comprises a bluetooth receiver processing module: the Bluetooth receiver comprises a demodulation module, the Bluetooth receiver adopts a low intermediate frequency technology, the delay is dynamically set, data output by the demodulation module is firstly synchronized by using a bit preamble and a bit access code at a sampling rate to obtain an initial position of the data, then downsampling is carried out to preset data, and demodulated data is obtained after hard judgment.
The invention provides a demodulation method of a Bluetooth receiver, which comprises the following steps:
step 1: obtaining an analog signal after the radio frequency signal is subjected to down conversion, obtaining a digital sampling rate signal after the analog signal is subjected to ADC (analog to digital converter) sampling, obtaining a digital signal after the digital sampling rate signal is subjected to rate conversion and is changed into integral multiple of carrier central frequency of the analog signal, and performing low-pass filtering after the digital signal subjected to rate conversion is subjected to related multiplication with the time delay of the digital signal;
step 2: and demodulating the Bluetooth receiver by dynamically setting time delay.
Preferably, the step 1 further comprises: the delay multiplication is expressed as:
Figure BDA0003243831410000041
wherein v isoutRepresenting the result of the delay multiplication; f represents the center frequency of the low intermediate frequency carrier; t tableShowing time; theta represents the initial phase of the carrier; τ represents time delay;
Figure BDA0003243831410000042
represents the phase;
after low pass filtering, the multiple frequency is filtered out, yielding:
Figure BDA0003243831410000043
AMoutrepresenting amplitude values representing the signal after filtering;
Figure BDA0003243831410000044
preferably, the step 2 comprises: demodulation is performed by dynamically setting the time delay:
if it is set up
Figure BDA0003243831410000045
Substituting equation (6) yields:
Figure BDA0003243831410000046
therein
Figure BDA0003243831410000047
Wherein, InRepresenting a transmitting side binary bit; the subscript n denotes the time of the digitally sampled signal;
if it is set up
Figure BDA0003243831410000051
Substituting equation (6) yields:
Figure BDA0003243831410000052
therein
Figure BDA0003243831410000053
Due to amplitude values AM of the output signaloutDependent on phase
Figure BDA0003243831410000054
While phase position
Figure BDA0003243831410000055
Again depending on the time delay τ, and hence the phase
Figure BDA0003243831410000056
And time delay tau.
Preferably, the method further comprises the bluetooth transmitting end processing step of: assuming that the size of a user data packet output from the MAC layer is an assumed bit, firstly adding a pre-detection bit CRC check to enter the digital processing of the physical layer, and changing the pre-detection bit CRC check into a preset bit; for a non-coding system, framing operation is carried out to form a prediction bit frame; and the predicted bit frame is sent to a modulation module for GFSK modulation to generate a GFSK signal, and the GFSK signal enters an analog channel through a DAC to be processed and sent to an air interface.
Preferably, the method further comprises the bluetooth receiver processing step of: the Bluetooth receiver adopts a low-intermediate frequency technology, dynamically sets time delay, and demodulates data output by a module, firstly, obtains an initial position of the data by using bit preamble and bit access code synchronization under a sampling rate, then performs down-sampling to preset data, and obtains demodulated data after hard judgment.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention improves the existing demodulation algorithm of the Bluetooth receiver, fundamentally improves the performance of the receiver, and can greatly improve the performance by 4-5dB under the condition of not increasing the complexity;
2. the demodulation delay size of the invention can be configured;
3. the invention has small calculation amount and low cost.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a diagram of a conventional FM-to-AM demodulation;
FIG. 2 is a diagram of a typical Bluetooth system receiver process;
FIG. 3 is a graph comparing the performance of different delay receivers at the Bluetooth 1M rate;
fig. 4 is a diagram of a process at the transmitting end of a typical bluetooth system.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.
FM-to-AM legacy receiver scheme: as shown in fig. 1, a conventional FM-to-AM demodulation scheme is shown. FM-to-AM represents frequency modulation to amplitude modulation. FM is called Frequency Modulation in English, and Chinese translation is Frequency Modulation. AM is called Amplitude Modulation throughout english, and chinese translation is Amplitude Modulation.
r (k) represents the output signal of the ADC, k representing the sampling time of the ADC; j represents a complex symbol; denotes multiplication; t represents time; i represents the orthogonal component; q represents an in-phase component; e represents a natural constant; and pi represents the circumferential ratio. Down sampling is carried out on the Chinese translation of the Down sampling; the branch Chinese translation is a branch; the Bandpass filter Chinese translation is a band-pass filter; delay Chinese translation is delay; the Lowpassfilter Chinese translation is a low pass filter, AMoutRepresenting the amplitude values of the signal after filtering.
The Bluetooth adopts a low intermediate frequency technology, after down-conversion is carried out on a baseband signal with the bandwidth of 1M, the carrier central frequency is 5MHz, the ADC adopts a 32MHz sampling rate, in order to change the bandwidth into an integral multiple of 5MHz, the 32MHz needs to be subjected to rate conversion into 20MHz to obtain a low intermediate frequency digital signal, the low intermediate frequency digital signal subjected to rate conversion is subjected to related multiplication with the delay thereof, and then low-pass filtering is carried out. ADC is called analog to digital converter in English, and Chinese translation is an analog-digital converter. The above process is formulated as:
the delay multiplication can be expressed as:
Figure BDA0003243831410000061
voutrepresenting the result of the delay multiplication; f represents the center frequency of the low intermediate frequency carrier wave and is 5 Mhz; t represents time; theta represents the initial phase of the carrier; τ represents time delay;
Figure BDA0003243831410000062
indicating the phase.
After low pass filtering, the 2 multiples are filtered out, yielding:
Figure BDA0003243831410000063
AMoutrepresenting the amplitude values of the signal after filtering.
The time delay tau is chosen such that
Figure BDA0003243831410000064
It is possible to obtain:
Figure BDA0003243831410000065
thus AMoutIs given a value of
Figure BDA0003243831410000066
And (6) determining. Conventional bluetooth receiver
Figure BDA0003243831410000067
Substitution into
Figure BDA0003243831410000068
Wherein:
Figure BDA0003243831410000071
t denotes the duration of the baseband waveform, here 1Mhz, InRepresenting the transmit side binary bits.
Can obtain the final product
Figure BDA0003243831410000072
FM-to-AM modifications: as can be seen from equation (5), AMoutIs determined by
Figure BDA0003243831410000073
Due to the sin function in
Figure BDA0003243831410000074
Is a monotonic function, therefore AMoutThe value depends on
Figure BDA0003243831410000075
That is to say that
Figure BDA0003243831410000076
Is very small at close to 0, and is close to
Figure BDA0003243831410000077
And
Figure BDA0003243831410000078
it is very large. And it is obvious that
Figure BDA0003243831410000079
The larger and the closer
Figure BDA00032438314100000710
Capability to receive hard decisionsThe better, while of a conventional receiver
Figure BDA00032438314100000711
Is far less than
Figure BDA00032438314100000712
And thus its performance is not good.
The embodiment of the invention discloses a Bluetooth receiver demodulation system, which comprises the following modules as shown in figures 1 and 2: module M1: the Bluetooth receiver comprises an ADC, wherein radio frequency signals are subjected to down-conversion to obtain analog signals (), the analog signals are subjected to ADC sampling to obtain digital sampling rate, the digital sampling rate is subjected to rate conversion to be converted into integral multiples of carrier central frequency of the analog signals to obtain digital signals, the digital signals subjected to rate conversion are subjected to related multiplication with delay of the digital signals, and then low-pass filtering is performed.
The radio frequency signal is subjected to down-conversion to obtain an analog low-intermediate frequency signal, the analog low-intermediate frequency signal is subjected to ADC sampling to obtain a high-multiple digital sampling signal, the high-multiple digital sampling signal is subjected to rate conversion to be an integral multiple of the carrier central frequency of the analog low-intermediate frequency signal to obtain a low-intermediate frequency digital signal, the low-intermediate frequency digital signal subjected to rate conversion is subjected to related multiplication with the delay of the low-intermediate frequency digital signal, and then low-pass filtering is performed. The low intermediate frequency is about 4-6 MHz. The radio frequency signal is obtained from a radio frequency front end. The radio frequency signal is down-converted by the low intermediate frequency receiver to obtain a carrier central frequency of 5Mhz, an ADC in the Bluetooth receiver adopts a sampling rate of 32Mhz, the sampling rate is subjected to rate conversion to become 20Mhz which is an integral multiple of the carrier central frequency to obtain a low intermediate frequency digital signal, the low intermediate frequency digital signal after the rate conversion is subjected to related multiplication with the delay of the low intermediate frequency digital signal, and then low-pass filtering is carried out. The delayed multiplication is expressed as
Figure BDA00032438314100000713
voutRepresenting the result of the delay multiplication; f represents the center frequency of the low intermediate frequency carrier wave and is 5 Mhz;t represents time; theta represents the initial phase of the carrier; τ represents time delay;
Figure BDA00032438314100000714
indicating the phase.
After low pass filtering, the multiple frequency is filtered out, yielding:
Figure BDA00032438314100000715
AMoutrepresenting the amplitude values of the signal after filtering.
The scheme of the invention comprises a novel Bluetooth receiver demodulation scheme: to this end a new receiver scheme is derived as follows: after low pass filtering, the 2 multiples are filtered out, yielding:
namely, it is
Figure BDA0003243831410000081
Module M2: and demodulating the Bluetooth receiver by dynamically setting time delay. Demodulation is performed by dynamically setting two time delays: if it is set up
Figure BDA0003243831410000082
Substituting equation (6) can result in:
Figure BDA0003243831410000083
therein
Figure BDA0003243831410000084
Wherein, InRepresenting a transmitting side binary bit; the index n indicates the time of the digitally sampled signal.
If it is set up
Figure BDA0003243831410000085
Can be substituted into formula (6)Obtaining:
Figure BDA0003243831410000086
therein
Figure BDA0003243831410000087
Due to amplitude values AM of the output signaloutDependent on phase
Figure BDA0003243831410000088
While phase position
Figure BDA0003243831410000089
Again depending on the time delay τ, and hence the phase
Figure BDA00032438314100000810
And time delay tau, the following table summarizes the phase
Figure BDA00032438314100000811
And time delay tau.
Figure BDA00032438314100000812
From this table it can be seen that the maximum phase can be reached
Figure BDA00032438314100000813
We simulate the no-coding Bluetooth transmission performance of 1M code rate under Gaussian white noise channel.
As shown in fig. 3, delay-1 in fig. 3 indicates the performance of the bit error rate of the conventional bluetooth receiver, and the others are the performance of the bit error rate of other delays after the popularization of the present invention, and in general, the actual standard is to see the signal-to-noise ratio corresponding to the bit error rate of 0.001. We see that to achieve a bit error rate of 0.001, the conventional receiver needs 17.5dB, while the new receiver modified by the present invention with delay-19 needs only 13.2dB to achieve a bit error rate of 0.001. There is a gain of about 4.3 dB.
As shown in fig. 3, the Bluetooth chinese translation is Bluetooth; rate Chinese translation is rate; the performance Chinese translation is performance; BER English is called Bit Error Ratio, and Chinese translation is Bit Error probability; snr is called SIGNAL-NOISE RATIO in English; the Chinese translation is the signal-to-noise ratio; dB is called decibel and Chinese translation is decibel. delay is a translation in delay.
The system further includes a bluetooth transmitting end processing module, as shown in fig. 4, the bluetooth transmitting end processing module includes a MAC layer, a physical layer, a CRC, a DAC, and a modulation module, and the MAC layer is a media access control layer. MAC is called media access control entirely in English, and Chinese translation is media access control. CRC is called Cyclic redundancy check in English, and Chinese translation is Cyclic redundancy check. DAC is called digital-to-analog conversion, and Chinese translation is digital-to-analog converter. Assuming that the size of a user data packet output from the MAC layer is an assumed bit, firstly adding a pre-detection bit CRC check to enter the digital processing of the physical layer, and changing the pre-detection bit CRC check into a preset bit; for a non-coding system, framing operation is carried out to form a prediction bit frame; and the predicted bit frame is sent to a modulation module for GFSK modulation to generate a GFSK signal, and the GFSK signal enters an analog channel through a DAC to be processed and sent to an air interface. GFSK is called Gauss frequency Shift Keying in English, and Chinese translation is Gaussian frequency Shift Keying. Fig. 4 is a typical bluetooth transmit side process. Assuming that the size of the user data packet output from the MAC layer is 100 bytes, i.e., 800 bits, the 24-bit CRC check is first added to the digital processing entering the physical layer, and becomes 824 bits. Assuming a 1M uncoded system, the framing operation is immediately performed, i.e., 8-bit preamble is added, and 32-bit access code is added, and the data bits constitute 864-bit frames. And sending the signal to a modulation module for GFSK modulation to generate a GFSK signal, and then entering an analog channel through a DAC for processing and sending the GFSK signal to an air interface. The MAC layer represents a media access layer; in fig. 4, a lower case MAC represents a Packet of the MAC layer, and a translation in a Packet is a Packet.
The system also includes a bluetooth receiver processing module, as shown in fig. 2, the bluetooth receiver includes a demodulation module, the bluetooth receiver adopts low-intermediate frequency technology, dynamically sets delay, and the data from the decoding module is firstly synchronized by using bit preamble and bit access code at 20MHz sampling rate to obtain the initial position of the data, then down-sampling to predetermined data, and obtaining demodulated data after hard judgment. Fig. 2 is a typical bluetooth receiver process. The bluetooth adopts the low-intermediate frequency technology, after down-conversion, the carrier central frequency is 5MHz for the baseband signal with the bandwidth of 1M, and the baseband signal is sent to the demodulation module, the demodulation module refers to the flow of fig. 1 for processing, the ADC adopts the 32MHz sampling rate, in order to change into the integral multiple of 5MHz, the 32MHz needs to be subjected to rate conversion into 20MHz, the signal after rate conversion is subjected to relevant multiplication with the delay thereof, and then low-pass filtering is performed. The delay here has a size of 19. The data from the decoding module is first synchronized by 8-bit preamble and 32-bit access code at 20MHz to obtain the starting position of the data. And then down-sampling to 1M, and obtaining demodulated data after hard judgment.
As shown in FIG. 2, the Analog Chinese translation is a simulation; the digit Chinese translation is a digital technology; the RF is called Radio Frequency entirely in English, and the Chinese translation is Radio Frequency; data Chinese translation is Data; RS is called radiation Susceptibility in English, and Chinese translation is radiation immunity.
The invention provides a variable-delay FM-to-AM demodulation method through the analysis and simulation of the traditional demodulation algorithm, thereby fundamentally improving the performance of a receiver, and greatly improving the performance by 4-5dB under the condition of not increasing the complexity.
The embodiment of the invention discloses a method for demodulating a Bluetooth receiver, which comprises the following steps as shown in figures 1 and 2: step 1: the radio frequency signal is subjected to down-conversion to obtain an analog low-intermediate frequency signal, the analog low-intermediate frequency signal is subjected to ADC sampling to obtain a high-multiple digital sampling signal, the high-multiple digital sampling signal is subjected to rate conversion to be an integral multiple of the carrier central frequency of the analog low-intermediate frequency signal to obtain a low-intermediate frequency digital signal, the low-intermediate frequency digital signal subjected to rate conversion is subjected to related multiplication with the delay of the low-intermediate frequency digital signal, and then low-pass filtering is performed.
The delay multiplication is expressed as:
Figure BDA0003243831410000101
wherein v isoutRepresenting the result of the delay multiplication; f represents the center frequency of the low intermediate frequency carrier; t represents time; theta represents the initial phase of the carrier; τ represents time delay;
Figure BDA0003243831410000102
indicating the phase.
After low pass filtering, the multiple frequency is filtered out, yielding:
Figure BDA0003243831410000103
AMoutrepresenting amplitude values representing the signal after filtering.
Namely, it is
Figure BDA0003243831410000104
Step 2: and demodulating the Bluetooth receiver by dynamically setting time delay. Demodulation is performed by dynamically setting the time delay: if it is set up
Figure BDA0003243831410000105
Substituting equation (6) yields:
Figure BDA0003243831410000106
therein
Figure BDA0003243831410000107
Wherein, InRepresenting a transmitting side binary bit; the index n indicates the time of the digitally sampled signal.
If it is set up
Figure BDA0003243831410000108
Substituting equation (6) yields:
Figure BDA0003243831410000109
therein
Figure BDA0003243831410000111
Due to amplitude values AM of the output signaloutDependent on phase
Figure BDA0003243831410000112
While phase position
Figure BDA0003243831410000113
Again depending on the time delay τ, and hence the phase
Figure BDA0003243831410000114
And time delay tau.
The method also comprises the processing steps of the Bluetooth transmitting end: assuming that the size of a user data packet output from the MAC layer is an assumed bit, firstly adding a pre-detection bit CRC check to enter the digital processing of the physical layer, and changing the pre-detection bit CRC check into a preset bit; for a non-coding system, framing operation is carried out to form a prediction bit frame; and the predicted bit frame is sent to a modulation module for GFSK modulation to generate a GFSK signal, and the GFSK signal enters an analog channel through a DAC to be processed and sent to an air interface.
The method further comprises the bluetooth receiver processing step of: the Bluetooth receiver adopts a low-intermediate frequency technology, dynamically sets time delay, and demodulates data output by a module, firstly, obtains an initial position of the data by using bit preamble and bit access code synchronization under a sampling rate, then performs down-sampling to preset data, and obtains demodulated data after hard judgment.
Those skilled in the art will appreciate that, in addition to implementing the system and its various devices, modules, units provided by the present invention as pure computer readable program code, the system and its various devices, modules, units provided by the present invention can be fully implemented by logically programming method steps in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers, embedded microcontrollers and the like. Therefore, the system and various devices, modules and units thereof provided by the invention can be regarded as a hardware component, and the devices, modules and units included in the system for realizing various functions can also be regarded as structures in the hardware component; means, modules, units for performing the various functions may also be regarded as structures within both software modules and hardware components for performing the method.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.

Claims (10)

1. A Bluetooth receiver demodulation system, comprising the following modules:
module M1: the Bluetooth receiver comprises an ADC, wherein radio frequency signals are subjected to down-conversion to obtain analog signals, the analog signals are subjected to ADC sampling to obtain digital sampling rate signals, the digital sampling rate signals are subjected to rate conversion to be converted into integral multiples of carrier central frequency of the analog signals to obtain digital signals, the digital signals subjected to rate conversion are subjected to related multiplication with delay of the digital signals, and then low-pass filtering is carried out;
module M2: and demodulating the Bluetooth receiver by dynamically setting time delay.
2. The bluetooth receiver demodulation system as claimed in claim 1, wherein said module M1 further comprises: the delay multiplication is expressed as:
Figure FDA0003243831400000011
wherein v isoutRepresenting the result of the delay multiplication; f represents the center frequency of the low intermediate frequency carrier; t represents time; theta represents the initial phase of the carrier; τ represents time delay;
Figure FDA0003243831400000012
represents the phase;
after low pass filtering, the multiple frequency is filtered out, yielding:
Figure FDA0003243831400000013
AMoutrepresenting an amplitude value of the signal after filtering;
namely, it is
Figure FDA0003243831400000014
3. The bluetooth receiver demodulation system according to claim 2, wherein said module M2 comprises: demodulation is performed by dynamically setting the time delay:
if it is set up
Figure FDA0003243831400000015
Substituting equation (6) yields:
Figure FDA0003243831400000016
therein
Figure FDA0003243831400000017
Wherein, InHair with indicationA transmit binary bit; the subscript n denotes the time of the digitally sampled signal;
if it is set up
Figure FDA0003243831400000018
Substituting equation (6) yields:
Figure FDA0003243831400000021
therein
Figure FDA0003243831400000022
Due to amplitude values AM of the output signaloutDependent on phase
Figure FDA0003243831400000023
While phase position
Figure FDA0003243831400000024
Again depending on the time delay τ, and hence the phase
Figure FDA0003243831400000025
And time delay tau.
4. The demodulation system of claim 1 further comprising a bluetooth transmitting end processing module, wherein the bluetooth transmitting end processing module comprises a MAC layer, a physical layer, a CRC, a DAC and a modulation module, and assuming that the size of the user data packet outputted from the MAC layer is an assumed bit, the digital processing entering the physical layer is firstly added with a CRC check of the pre-check bit and becomes a predetermined bit; for a non-coding system, framing operation is carried out to form a prediction bit frame; and the predicted bit frame is sent to a modulation module for GFSK modulation to generate a GFSK signal, and the GFSK signal enters an analog channel through a DAC to be processed and sent to an air interface.
5. The bluetooth receiver demodulation system of claim 1 further comprising a bluetooth receiver processing module: the Bluetooth receiver comprises a demodulation module, the Bluetooth receiver adopts a low intermediate frequency technology, the delay is dynamically set, data output by the demodulation module is firstly synchronized by using a bit preamble and a bit access code at a sampling rate to obtain an initial position of the data, then downsampling is carried out to preset data, and demodulated data is obtained after hard judgment.
6. A method for demodulating a bluetooth receiver, to which the bluetooth receiver demodulating system according to any one of claims 1 to 5 is applied, comprising the steps of:
step 1: obtaining an analog signal after the radio frequency signal is subjected to down conversion, obtaining a digital sampling rate signal after the analog signal is subjected to ADC (analog to digital converter) sampling, obtaining a digital signal after the digital sampling rate signal is subjected to rate conversion and is changed into integral multiple of carrier central frequency of the analog signal, and performing low-pass filtering after the digital signal subjected to rate conversion is subjected to related multiplication with the time delay of the digital signal;
step 2: and demodulating the Bluetooth receiver by dynamically setting time delay.
7. The method of claim 6, wherein step 1 further comprises: the delay multiplication is expressed as:
Figure FDA0003243831400000026
wherein v isoutRepresenting the result of the delay multiplication; f represents the center frequency of the low intermediate frequency carrier; t represents time; theta represents the initial phase of the carrier; τ represents time delay;
Figure FDA0003243831400000027
represents the phase;
after low pass filtering, the multiple frequency is filtered out, yielding:
Figure FDA0003243831400000031
AMoutrepresenting amplitude values representing the signal after filtering;
namely, it is
Figure FDA0003243831400000032
8. The method of claim 7, wherein the step 2 comprises: demodulation is performed by dynamically setting the time delay:
if it is set up
Figure FDA0003243831400000033
Substituting equation (6) yields:
Figure FDA0003243831400000034
therein
Figure FDA0003243831400000035
Wherein, InRepresenting a transmitting side binary bit; the subscript n denotes the time of the digitally sampled signal;
if it is set up
Figure FDA0003243831400000036
Substituting equation (6) yields:
Figure FDA0003243831400000037
therein
Figure FDA0003243831400000038
Due to amplitude values AM of the output signaloutDependent on phase
Figure FDA0003243831400000039
While phase position
Figure FDA00032438314000000310
Again depending on the time delay τ, and hence the phase
Figure FDA00032438314000000311
And time delay tau.
9. The method of claim 6, further comprising the step of processing at the bluetooth transmitter: assuming that the size of a user data packet output from the MAC layer is an assumed bit, firstly adding a pre-detection bit CRC check to enter the digital processing of the physical layer, and changing the pre-detection bit CRC check into a preset bit; for a non-coding system, framing operation is carried out to form a prediction bit frame; and the predicted bit frame is sent to a modulation module for GFSK modulation to generate a GFSK signal, and the GFSK signal enters an analog channel through a DAC to be processed and sent to an air interface.
10. The method of claim 6, further comprising the step of processing by the Bluetooth receiver: the Bluetooth receiver adopts a low-intermediate frequency technology, dynamically sets time delay, and demodulates data output by a module, firstly, obtains an initial position of the data by using bit preamble and bit access code synchronization under a sampling rate, then performs down-sampling to preset data, and obtains demodulated data after hard judgment.
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