An anti-jamming AGC baseband communication device based on a burst OFDM waveform

Abstract

The application relates to an anti-interference AGC baseband communication device based on a burst OFDM waveform, which comprises a radio frequency front-end circuit, a radio frequency receiving circuit and a baseband processor; the radio frequency front-end circuit is used for receiving and amplifying and filtering a signal and then transmitting the signal to the radio frequency receiving circuit; the radio frequency receiving circuit amplifies, mixes and digitizes an input signal and then transmits the signal to the baseband processor; the baseband processor is used for calculating the RSSI and the air interface power value of each period, determining the gain adjustment mode according to the air interface power value; when the gain adjustment mode is AGC adjustment, the RSSI is adjusted to a linear amplification area, and the total gain needing to be adjusted is obtained by subtracting a target gain value; the gain gear value of the amplifier in the radio frequency front-end circuit needing to be turned on is calculated according to the total gain needing to be adjusted and is then sent to the radio frequency front-end circuit; and the gain code word of the radio frequency receiving circuit needing to be adjusted is calculated in the linear adjustment area and is then sent to the radio frequency receiving circuit.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wireless receiver technology, and particularly relates to an anti-interference AGC baseband communication device based on burst OFDM waveform. BACKGROUND

[0002] Automatic gain control (AGC) in wireless communication is a technique used to maintain the amplitude of the receiver output signal constant. AGC function is essential in modern communication systems. AGC helps to maintain consistent signal strength, improve signal-to-noise ratio, and minimize distortion. In a wireless communication system, signal strength is affected by the distance between the transmitter and the receiver, as well as other factors such as obstacles and interference, AGC can ensure that the received signal is always within the optimal range for reception. Orthogonal frequency division multiplexing (OFDM) signal is the mainstream physical layer waveform in wireless communication, which adopts multi-carrier modulation, and its main idea is to divide the channel into several orthogonal sub-channels, and modulate the data stream to each sub-channel for transmission. OFDM waveform has the advantages of high spectrum utilization, anti-multipath fading ability, and improving data transmission rate, but OFDM signal has a large dynamic range, and the peak-to-average power ratio of the signal is high, which brings great challenges to the AGC to quickly and accurately adjust the gain to adapt to the large range of changes in the receiver signal. SUMMARY

[0003] In view of the above analysis, the embodiments of the present application aim to provide an anti-interference AGC baseband communication device based on burst OFDM waveform, to solve the problem that the existing wireless receiving device based on burst OFDM waveform is difficult for AGC to quickly and accurately adjust the gain due to the large dynamic range of OFDM signal and the high peak-to-average power ratio of the signal.

[0004] The embodiment of the application provides a burst OFDM waveform-based anti-interference AGC baseband communication device, which comprises a radio frequency front-end circuit, a radio frequency receiving circuit and a baseband processor; the radio frequency front-end circuit is used for receiving and amplifying and filtering a signal and then transmitting the signal to the radio frequency receiving circuit; the radio frequency receiving circuit amplifies, mixes and digitizes the input signal to obtain a digital signal and then transmits the digital signal to the baseband processor; the baseband processor is used for calculating a received signal strength RSSI and an air interface power value of each period according to the digital signal input by the radio frequency receiving circuit, determining a gain adjustment mode according to the air interface power value, wherein the gain adjustment mode comprises AGC adjustment, AGC keeping and AGC state locking; when the gain adjustment mode is AGC adjustment, the received signal strength RSSI is adjusted to a linear amplification zone, and a difference between the received signal strength RSSI and a target gain value is obtained to obtain a total gain that needs to be adjusted; the gain gear value of the amplifier in the radio frequency front-end circuit that needs to be turned on is calculated according to the total gain that needs to be adjusted and then is transmitted to the radio frequency front-end circuit; and the gain code word of the radio frequency receiving circuit that needs to be adjusted is calculated in the linear adjustment zone and then is transmitted to the radio frequency receiving circuit.

[0005] Further, the device further comprises an external memory of the baseband processor, wherein the external memory comprises a DDR memory; the DDR memory is used for storing a linear gain value code table, a fast control word gain table and a frequency compensation table; the linear gain value code table is used for storing actual gain amounts of the radio frequency receiving circuit under different gain code words; the fast control word gain table is used for storing actual gain values of the amplifier in the radio frequency front-end circuit under different gain gear values; and the frequency compensation table is used for storing gain deviations caused by frequency deviations of each frequency band of the signal and a center frequency point.

[0006] Further, the baseband processor comprises a power calculation module; the power calculation module is used for calculating the received signal strength RSSI of N signal points in each period according to data sampled by the radio frequency receiving circuit and calculating the air interface power value according to actual gain amounts stored in the linear gain value code table and the fast control word gain table and gain deviations stored in the frequency compensation table.

[0007] Further, the baseband processor further comprises an AGC automatic gain calculation module; the AGC automatic gain calculation module is used for determining the gain adjustment mode according to the air interface power value and a period in which the baseband processor is located; if the gain adjustment mode of the current period is AGC adjustment, the area in which the received signal strength RSSI is located is determined according to the received signal strength RSSI; if the received signal strength RSSI is located in a top saturation zone, the received signal strength RSSI is reduced by Δ1 to enter the linear amplification zone; if the received signal strength RSSI is located in an oversaturation zone, the received signal strength RSSI is reduced by Δ2 to enter the linear amplification zone, a difference between the signal strength entering the linear amplification zone and the target gain value is obtained to obtain the total gain that needs to be adjusted; and if the received signal strength RSSI is in the linear adjustment zone, a difference between the received signal strength RSSI and the target gain value is obtained to obtain the total gain that needs to be adjusted.

[0008] Further, the baseband processor further comprises an AGC gear calculation module and an AGC gain control module; the AGC gear calculation module is used for adjusting the total gain to be adjusted by the gain gear value in priority, reading out the actual gain value from the fast control word gain table with the gain gear value as the index value, and taking the actual gain value of the gain gear value adjustment from the total gain to be adjusted as the linear gain to be adjusted according to the gain gear value; the AGC gain control module takes the linear gain value code table with the linear gain to be adjusted plus the gain of the maximum gain gear value as the index, and calculates the gain code word according to the actual gain value in the linear gain value code table and sends it to the radio frequency receiving circuit.

[0009] Further, the AGC automatic gain calculation module determines the gain adjustment mode in the following manner:

[0010] Step 1, the AGC automatic gain calculation module judges whether the air interface power of the current period is greater than or equal to a first threshold value and whether the air interface power of the multiple historical periods before the current period is less than or equal to a second threshold value, if yes, it is determined that the rising edge of the air interface power is collected in the current period, and the gain adjustment mode of the current period is determined as AGC adjustment; wherein the first threshold value is greater than the second threshold value;

[0011] Step 2, from the period when the rising edge of the air interface power is collected, the gain adjustment mode of the first two or three periods among the N periods thereafter is AGC adjustment, and the gain adjustment mode of the remaining N-2 or N-3 periods thereafter is AGC maintenance; if the air interface power value of each period from the period when the rising edge of the air interface power is collected is greater than or equal to the first threshold value, the gain adjustment mode of each period after the N periods is determined as AGC state locking until the signal air interface power of a certain period after the N periods is less than or equal to the second threshold value, or the reduction of the air interface power of a certain period compared with the air interface power of the last period is greater than or equal to the third threshold value, or the sum of the reduction of the air interface power of a certain period compared with the air interface power of the last period and the reduction of the air interface power of the next period of the certain period compared with the air interface power of the certain period is greater than or equal to the third threshold value, or the current frame of the signal ends; if the air interface power value of a certain period from the next period of the period when the rising edge of the air interface power is collected is less than the first threshold value, it returns to step 1.

[0012] Further, the radio frequency front-end circuit comprises a radio frequency antenna, a first low noise amplifier, a frequency filter, and a second low noise amplifier; the radio frequency antenna receiving end is connected to the input end of the first low noise amplifier, the output end of the first low noise amplifier is connected to the input end of the frequency filter, the output end of the frequency filter is connected to the input end of the second low noise amplifier, and the output end of the second low noise amplifier is connected to the input end of the radio frequency receiving circuit.

[0013] Further, the radio frequency receiving circuit comprises a mixer, a low pass filter, and an ADC analog-to-digital converter; the output end of the mixer is connected to the input end of the low pass filter; the output end of the low pass filter is connected to the analog input end of the ADC analog-to-digital converter; and the digital sampling output end of the ADC analog-to-digital converter is connected to the baseband processor.

[0014] Further, the radio frequency receiving circuit further comprises a third low noise amplifier; the input end of the third low noise amplifier is connected to the output end of the second low noise amplifier, and the output end of the third low noise amplifier is connected to the input end of the mixer.

[0015] Further, the first to third low noise amplifiers, the frequency filter, the mixer, and the low pass filter are all provided with respective digital programmable circuits; the third low noise amplifier, the mixer, and the low pass filter realize the function of adjusting the linear gain value by every dB through respective control code words; the first and second low noise amplifiers realize the function of turning on or bypassing the low noise amplifier through respective gain gear values; and the frequency filter realizes the function of selecting different frequency band regions through the received control code word.

[0016] Compared with the prior art, the present application can realize at least one of the following beneficial effects:

[0017] 1. The baseband processor of the device is used for calculating the received signal strength RSSI and the air interface power value of each period according to the digital signal input by the radio frequency receiving circuit, determining the gain adjustment mode according to the air interface power value, wherein the gain adjustment mode comprises AGC adjustment, AGC keeping, and AGC state locking; when the gain adjustment mode is AGC adjustment, the received signal strength RSSI is adjusted to the linear amplification region, and the total gain to be adjusted is calculated by subtracting the target gain value; the gain gear value of the amplifier to be turned on in the radio frequency front-end circuit is calculated according to the total gain to be adjusted and is sent to the radio frequency front-end circuit; and the gain code word to be adjusted in the radio frequency receiving circuit is calculated in the linear adjustment region and is sent to the radio frequency receiving circuit. The gain is divided into multiple gain gears and linear gain adjustment values, so that the gain can be quickly converged to the linear adjustment region, and the gain adjustment to the target value can be completed within 2-3 periods (256 sampling points per period).

[0018] 2, The AGC automatic gain calculation module of the device adds power change prediction and AGC state locking function, can identify the arrival of the effective signal of the air interface, and lock the gain value after the gain adjustment of the AGC section of the effective signal of each wireless frame, until the end of the current wireless frame or the air interface power of a certain period after N periods is less than or equal to the second threshold value, or the reduction of the air interface power of a certain period compared with the air interface power of the last period is greater than or equal to the third threshold value, or the sum of the reduction of the air interface power of a certain period compared with the air interface power of the last period and the reduction of the air interface power of the next period of the certain period compared with the air interface power of the certain period is greater than or equal to the third threshold value, and the AGC locking state is released. The power change prediction and AGC state locking function of the device has stronger anti-disturbance ability for the burst synchronization of the waveform with higher peak-to-average ratio of OFDM waveform.

[0019] 3, The linear gain value code table, the fast control word gain table and the frequency compensation table are stored in the DDR memory of the device; the linear gain value code table is used for storing the actual gain amount of the radio frequency receiving circuit under different preset gains; the fast control word gain table is used for storing the actual gain value of the amplifier in the radio frequency front-end circuit under different gain position values; and the frequency compensation table is used for storing the gain deviation caused by the frequency deviation of each frequency band of the signal and the center frequency point. The linear gain value code table, the fast control word gain table and the frequency compensation table prestore the actual gain amount corresponding to different gain code words of the radio frequency receiving circuit, the actual gain value of the amplifier in the radio frequency front-end circuit under different gain position values and the gain deviation in the table, so that the result is obtained by fast table lookup in the AGC adjustment, the cumbersome formula calculation is reduced, the additional real-time calculation overhead is avoided, and the operation speed of the fast AGC state locking is improved.

[0020] In the application, the above technical solutions can be combined with each other to realize more preferred combination solutions. Other features and advantages of the application will be described in the subsequent description, and some advantages will become apparent from the description or be understood by implementing the application. The purposes and other advantages of the application can be realized and obtained from the contents specifically indicated in the description and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0021] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application.

[0022] Figure 1 A structure block diagram of an anti-interference AGC baseband communication device based on a burst OFDM waveform is provided in the application;

[0023] Figure 2 A working flowchart of an anti-interference AGC baseband communication device based on a burst OFDM waveform is provided in the application;

[0024] Figure 3 The present invention is a flowchart of a method for adjusting AGC as a gain adjustment mode in an anti-interference AGC baseband communication device based on a burst OFDM waveform. DETAILED DESCRIPTION

[0025] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, and are not used to limit the scope of the present invention.

[0026] A specific embodiment of the present invention discloses an anti-interference AGC baseband communication device based on a burst OFDM waveform, such as Figure 1 As shown. The device includes: a radio frequency front-end circuit, a radio frequency receiving circuit and a baseband processor; the radio frequency front-end circuit is used to receive a signal and amplify and filter the signal before sending it to the radio frequency receiving circuit, and the radio frequency receiving circuit amplifies, mixes, and performs analog-to-digital conversion on the input signal to obtain a digital signal and transmit it to the baseband processor; the baseband processor is used to calculate the received signal strength RSSI and the air interface power value of each cycle based on the digital signal input by the radio frequency receiving circuit, and determine the gain adjustment mode based on the air interface power value, and the gain adjustment mode includes AGC adjustment, AGC hold, and AGC state lock; when the gain adjustment mode is AGC adjustment, the received signal strength RSSI is adjusted to the linear amplification region, and the total gain to be adjusted is obtained by subtracting it from the target gain value; the gain gear value of the amplifier in the radio frequency front-end circuit to be turned on is calculated based on the total gain to be adjusted and sent to the radio frequency front-end circuit; the gain codeword to be adjusted by the radio frequency receiving circuit is calculated in the linear adjustment region and sent to the radio frequency receiving circuit.

[0027] Specifically, the method for calculating the air interface power value is to first calculate the received signal strength RSSI power value for each cycle, and then convert the RSSI power value into a logarithmic value (db). The air interface power value is calculated by reverse deduction from the received signal strength RSSI based on the actual gain stored in the linear gain value code table corresponding to the gain level used in the current cycle, the fast control word gain table, and the gain deviation stored in the frequency compensation table corresponding to the gain codeword used in the current cycle.

[0028] The total gain that needs to be adjusted is calculated as follows:

[0029] The sampling range of the ADC analog-to-digital converter is 16 bits, so the maximum sampling value is 2 16 . Converted to logarithmic value 20log 10 2 16 , so the maximum value of the logarithm is 96.3296. The target gain value is set to 2 11 , converted to logarithmic value 20log 10 211 The logarithmic value of the target gain value is 66.2266.

[0030] After obtaining the sampling maximum value and the target gain value, the interval division is started:

[0031] The sampling signal range of the top saturation area is between 15 bits and 16 bits, and the logarithmic value range of the top saturation area is 20log 10 2 15 ~ 20log 10 2 16 , i.e. 90.3090~96.3296. The interval adjustment reduces the gain Δ1=25db.

[0032] The sampling signal range of the over-saturation area is between 13 bits and 15 bits, and the logarithmic value range of the over-saturation area is 20log 10 2 13 ~ 20log 10 2 15 , i.e. 78.2678~90.3090. The interval adjustment reduces the gain Δ2=18db.

[0033] Less than 13 bits is a linear amplification area, which includes a linear adjustment area and a gain maintaining area.

[0034] The sampling signal range of the linear adjustment area is between 12 bits and 13 bits or less than 10 bits, and the logarithmic value range of the linear adjustment area is 20log 10 2 12 ~ 20log 10 2 13 , obtaining the interval range 72.2472~78.2678. Or <20log 10 2 10 , i.e. <60db. The logarithmic value range of the linear adjustment area is <60db or between 72.2472~78.2678.

[0035] Adjust the target gain value to 2 11 , and calculate the logarithmic value 20log 10 2 11 , obtaining the logarithmic value of the target gain value as 66.2266.

[0036] The logarithmic values of the sampling signals in the top saturation area, the over-saturation area and the linear adjustment area are adjusted to the gain holding area, the method is that the difference between the logarithmic values of the signal intensity after the adjustment of the top saturation area and the over-saturation area to the linear amplification area and the logarithmic values of the signal intensity in the linear adjustment area of the received signal intensity RSSI is subtracted by 66.2266db, the difference is used to look up the fast control word gain table and the linear gain value code table, and the gain gear value and the gain code word required for adjustment are sent to the radio frequency front-end circuit and the radio frequency receiving circuit to realize the AGC adjustment, and if the RSSI logarithmic value calculated by the baseband processor after the AGC adjustment enters the gain holding area 66.2266db±3db, it is considered that the AGC adjustment is completed. The logarithmic value of the signal intensity out of the gain holding area is: <60db or >72db.

[0037] The radio frequency front-end circuit comprises a radio frequency antenna, a first low-noise amplifier, a frequency filter and a second low-noise amplifier; the radio frequency antenna receiving end is connected to the input end of the first low-noise amplifier, the output end of the first low-noise amplifier is connected to the input end of the frequency filter, the output end of the frequency filter is connected to the input end of the second low-noise amplifier, and the output end of the second low-noise amplifier is connected to the input end of the radio frequency receiving circuit.

[0038] The radio frequency receiving circuit comprises a mixer, a low-pass filter and an ADC analog-to-digital converter; the output end of the mixer is connected to the input end of the low-pass filter; the output end of the low-pass filter is connected to the analog input end of the ADC analog-to-digital converter; and the digital sampling output end of the ADC analog-to-digital converter is connected to the baseband processor.

[0039] Specifically, after passing through the radio frequency front-end circuit, the signal enters the radio frequency receiver, and a zero intermediate frequency circuit is adopted in the design, which internally has a low-pass filter, a mixer, a low-pass filter and an ADC analog-to-digital converter, and this part converts the radio frequency signal into a digital baseband signal. The receiving gain code word of this part is written into the gain register of the receiver through SPI communication.

[0040] The radio frequency receiving circuit further comprises a third low-noise amplifier; the input end of the third low-noise amplifier is connected to the output end of the second low-noise amplifier, and the output end of the third low-noise amplifier is connected to the input end of the mixer.

[0041] The first to third low-noise amplifiers, the frequency filter, the mixer and the low-pass filter all have respective digital programmable circuits, the third low-noise amplifier, the mixer and the low-pass filter realize the function of adjusting the linear gain value by every dB through respective control code words; the first and second low-noise amplifiers realize the opening or bypassing of the low-noise amplifier through respective gain gear values; and the frequency filter realizes the gating of different frequency band areas through the received control code word.

[0042] Specifically, the radio frequency front-end circuit further comprises a radio frequency switch, which is used for switching of the input channel and the output channel of the device.

[0043] The device further comprises a baseband processor external memory, which comprises a DDR memory, and the DDR memory is used for storing a linear gain value code table, a fast control word gain table, and a frequency compensation table; the linear gain value code table is used for storing actual gain amounts of the radio frequency receiving circuit under different gain code words; the fast control word gain table is used for storing actual gain values of the amplifier in the radio frequency front-end circuit under different gain position values; and the frequency compensation table is used for storing gain deviations caused by frequency deviations of each frequency band of a signal and a center frequency point.

[0044] Specifically, the linear gain value code table, the fast control word gain table, and the frequency compensation table are a plurality of data structures, which are used for pre-calibration by measurement to record actual gain values obtained by each step gain position value or gain code word. The frequency compensation table is used for compensating gain deviations caused by frequency deviations of each frequency band of an actual received signal and a center frequency point (because the data is sampled according to the center frequency point, but the actual required data is data within a frequency band on the frequency domain, and there is a gain deviation between the gain of a frequency point outside the center frequency point and the gain of the center frequency point), and the gain deviation amount from the center frequency point is calculated according to a step of 5 Mhz of the frequency deviation and is stored in the frequency compensation table.

[0045] The baseband processor comprises a power calculation module; the power calculation module is used for calculating received signal strength RSSI of N signal points in each period according to data sampled by the radio frequency receiving circuit and calculating air interface power values according to actual gain amounts stored in the linear gain value code table and the fast control word gain table and gain deviations stored in the frequency compensation table.

[0046] Specifically, the radio frequency receiving circuit continuously sends digital sampling signals to the baseband processor, the baseband processor stores the digital sampling signals in a data buffer through a DMA mode, and then an AGC timer is configured to periodically trigger an AGC timing interrupt, and a specific embodiment of the present application takes N=256 digital sampling points as one period, enters the interrupt, and calculates an average value of RSSI of signals in each period as the received signal strength RSSI.

[0047] The received signal strength RSSI calculation formula is as follows:

[0048]

[0049] N=256, I i is an I component of the i th digital sampling signal, and Q i is a Q component of the i th digital sampling signal.

[0050] The baseband processor further comprises an AGC automatic gain calculation module; the AGC automatic gain calculation module is used for determining a gain adjustment mode according to an air interface power value and a period in which the baseband processor is located; if the gain adjustment mode of the current period is AGC adjustment, the baseband processor determines a region in which the baseband processor is located according to a received signal strength RSSI; if the received signal strength RSSI is located in a top saturation region, the received signal strength RSSI is reduced by Δ1 to enter a linear amplification region; if the received signal strength RSSI is located in an oversaturation region, the received signal strength RSSI is reduced by Δ2 to enter the linear amplification region; a difference between a signal strength entering the linear amplification region and a target gain value is obtained to obtain a total gain that needs to be adjusted; if the received signal strength RSSI is in a linear adjustment region, a difference between the received signal strength RSSI and the target gain value is obtained to obtain the total gain that needs to be adjusted.

[0051] Specifically, in the gain adjustment mode judgment stage, a gain interval is judged according to a received signal strength RSSI calculated by the baseband processor; the gain interval is divided into a top saturation region, an oversaturation region, a linear adjustment region and a gain keeping region; a gain adjustment value of the current round is obtained according to the region in which the received signal strength RSSI is located; when the received signal strength RSSI is in the gain keeping region, the gain is kept unchanged; when the received signal strength RSSI is in the top saturation region, it is indicated that the gain has entered a nonlinear region 1, therefore the gain is reduced by Δ1, Δ1=25db in an embodiment of the present application, the top saturation region is left and the linear amplification region is entered; when the received signal strength RSSI is in the oversaturation region, it is indicated that the gain has entered a nonlinear region 2, therefore the gain is reduced by Δ2, Δ2=18db in an embodiment of the present application, the oversaturation region is left; when the received signal strength RSSI is in the linear adjustment region, the gain is directly adjusted to a target value, therefore a difference between the received signal strength RSSI and the target gain value is obtained to obtain the total gain that needs to be adjusted.

[0052] The baseband processor further comprises an AGC gear calculation module and an AGC gain control module; the AGC gear calculation module is used for preferentially adjusting the total gain that needs to be adjusted by a gain gear value according to the total gain that needs to be adjusted and a gain gear value state of an amplifier in a radio frequency front-end circuit, reading an actual gain value from a fast control word gain table by taking the gain gear value as an index value, and taking the actual gain value adjusted by the gain gear value as linear gain that needs to be adjusted; the AGC gain control module takes the linear gain that needs to be adjusted and a gain when the gain gear value is maximum as indexes to search a linear gain value code table, calculates an actual gain value in the linear gain value code table, and sends a gain code word to a radio frequency receiving circuit.

[0053] Specifically, the linear gain value code table is used to take the total gain of the linear gain corresponding to the gain code word received by the radio frequency receiving circuit and the maximum amplifier gain position value in the radio frequency front-end circuit as the address, and store the difference between the signal power obtained after the signal source output signal passes through the radio frequency front-end circuit and the radio frequency receiving circuit and the signal source output signal power as the actual gain amount in the corresponding address of the code table; the fast control word gain table is used to store the actual gain value of the signal source output power after passing through the first low noise amplifier and the second low noise amplifier under the control of the different position value control codes of the first low noise amplifier and the second low noise amplifier and the fixed gain of the radio frequency receiving circuit; the frequency compensation table is used to store the gain deviation caused by the frequency deviation of the center frequency point of the signal source output signal and the center frequency point of the frequency band set by the frequency filter.

[0054] The AGC automatic gain calculation module determines the gain adjustment mode in the following manner:

[0055] Step 1, the AGC automatic gain calculation module determines whether the current period air interface power is greater than or equal to the first threshold value and whether the air interface power of the multiple historical periods before the current period is less than or equal to the second threshold value, if yes, it is determined that the rising edge of the air interface power is collected in the current period, and the gain adjustment mode of the current period is determined as AGC adjustment; wherein the first threshold value is greater than the second threshold value;

[0056] Step 2, in the N periods after the period in which the rising edge of the air interface power is collected, the gain adjustment mode of the first two or three periods is AGC adjustment, and the gain adjustment mode of the remaining N-2 or N-3 periods is AGC keeping; if the air interface power value of each period in the N periods after the period in which the rising edge of the air interface power is collected is greater than or equal to the first threshold value, the gain adjustment mode of each period after the N periods is determined as AGC state locking until the air interface power of a certain period after the N periods is less than or equal to the second threshold value, or the reduction of the air interface power of a certain period compared with the air interface power of the previous period is greater than or equal to the third threshold value, or the sum of the reduction of the air interface power of a certain period compared with the air interface power of the previous period and the reduction of the air interface power of the next period of the certain period compared with the air interface power of the certain period is greater than or equal to the third threshold value, or the current frame of the signal ends; if the air interface power value of a certain period in the N-1 periods starting from the next period of the period in which the rising edge of the air interface power is collected is less than the first threshold value again, it returns to step 1.

[0057] Specifically, the AGC adjustment gain adds power conversion trend prediction and AGC locking capability, first acquires the length of the frame header AGC section of a radio frame, monitors the mutation of the air interface power and the current noise threshold statistical value, calculates whether the current signal is in the noise section or the effective waveform section according to the air interface power of the current period and multiple historical periods, judges the starting and ending boundaries of the effective signal in this way, locks the gain after the gain adjustment of the AGC section of the signal frame, and the design avoids the misoperation of AGC caused by the energy change or additional noise of the data frame after the AGC section, reduces the probability of AGC mis-triggering caused by the average power fluctuation of the high peak-to-average ratio of the OFDM waveform, and the superimposed air interface interference signal in the frame period outside the AGC section will not cause AGC mis-triggering, and the anti-interference capability is improved.

[0058] The baseband processor further comprises a frequency configuration module; the frequency configuration module is configured to determine a center frequency point of a current received signal, and according to the frequency filter band region to which the currently determined center frequency point of the received signal belongs, to issue a control code word to configure a frequency filter band region.

[0059] Specifically, the frequency configuration module sends 2 bytes of data to the frequency filter through an SPI interface, 15-10 bits are invalid data; 9-8 bits are band region selection codes: 00 for 225-655 MHz, 01 for 655-1200 MHz, and 10 for 1200-1700 MHz; 7-0 bits are frequency filter center frequency control codes.

[0060] The frequency filter center frequency control code word calculation formula is:

[0061] Control code word = (f x -f low ) / (f high -f low )×250; f x is the center frequency of the received signal, f low is the lowest frequency in the band region, f high is the highest frequency in the band region, and 250 is the total number of steps in the segment. If the calculation result is a decimal, it should be rounded to an integer. For example: the control code word of the input 255MHz signal = (255-225) / (655-225)×250 = 30 / 430×250 = 17.4; rounding to 17; converted to hexadecimal result is 0x11.

[0062] In each frequency band region of the frequency filter, the center frequency of the required sub-frequency segment can be selected, and the frequency filter sub-frequency segment center frequency selected by the above control code word 0x11 is 255MHz.

[0063] Compared with the prior art, the baseband processor provided in the embodiment is used to calculate the received signal strength RSSI and the air interface power value of each period according to the digital signal input by the radio frequency receiving circuit, determine the gain adjustment mode according to the air interface power value, the gain adjustment mode including AGC adjustment, AGC keeping and AGC state locking; when the gain adjustment mode is AGC adjustment, the received signal strength RSSI is adjusted to the linear amplification zone, and the total gain to be adjusted is calculated by subtracting the target gain value; the gain gear value of the amplifier in the radio frequency front-end circuit to be turned on is calculated according to the total gain to be adjusted and is sent to the radio frequency front-end circuit; the gain code word to be adjusted of the radio frequency receiving circuit is calculated in the linear adjustment zone and is sent to the radio frequency receiving circuit. The gain is divided into multiple gain gears and linear gain adjustment values, which can quickly converge to the linear adjustment zone and complete the gain adjustment to the target value within 2-3 periods (256 sampling points per period). The AGC automatic gain calculation module provided in the embodiment adds the power change prediction and AGC state locking functions, can identify the arrival of the air interface effective signal, and lock the gain value after the gain adjustment in the AGC segment of each wireless frame effective signal until the end of the current wireless frame or the signal air interface power in a certain period after N periods is less than or equal to the second threshold value, or the reduction of the air interface power in a certain period compared with the air interface power in the last period is greater than or equal to the third threshold value, or the sum of the reduction of the air interface power in a certain period compared with the air interface power in the last period and the reduction of the air interface power in the next period of the certain period compared with the air interface power in the certain period is greater than or equal to the third threshold value. The power change prediction and AGC state locking functions of the device have stronger anti-disturbance ability for the burst synchronization of the waveform with a higher peak-to-average ratio of the OFDM waveform. The DDR memory provided in the embodiment stores the linear gain value code table, the fast control word gain table and the frequency compensation table; the linear gain value code table is used to store the actual gain amount of the radio frequency receiving circuit under different preset gains; the fast control word gain table is used to store the actual gain value of the amplifier in the radio frequency front-end circuit under different gain gear values; and the frequency compensation table is used to store the gain deviation corresponding to the frequency difference between the center frequency point of different signals and the center frequency point of the frequency band set by the frequency filter. The linear gain value code table, the fast control word gain table and the frequency compensation table prestore the actual gain amount corresponding to different gain code words of the radio frequency receiving circuit, the actual gain value of the amplifier in the radio frequency front-end circuit under different gain gear values and the gain deviation in the table, obtain the result by fast table lookup in the AGC adjustment, reduce the cumbersome formula calculation, avoid the additional real-time calculation overhead, and improve the operation speed of the fast AGC state locking.

[0064] Those skilled in the art can understand that all or part of the processes of the above-mentioned embodiment methods can be completed by instructing the relevant hardware by a computer program, and the program can be stored in a computer readable storage medium. The computer readable storage medium is a disk, an optical disk, a read-only memory, a random access memory, etc.

[0065] The above description is merely preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. An anti-interference AGC baseband communication device based on burst OFDM waveform, characterized in that: The device includes: a radio frequency front-end circuit, a radio frequency receiving circuit and a baseband processor; the radio frequency front-end circuit is used to receive a signal and amplify and filter the signal before sending it to the radio frequency receiving circuit, and the radio frequency receiving circuit amplifies, mixes, and performs analog-to-digital conversion on the input signal to obtain a digital signal and transmit it to the baseband processor; the baseband processor is used to calculate the received signal strength RSSI and the air interface power value of each cycle according to the digital signal input by the radio frequency receiving circuit, and determine the gain adjustment mode according to the air interface power value, and the gain adjustment mode includes AGC adjustment, AGC hold, and AGC state lock; when the gain adjustment mode is AGC adjustment, the received signal strength RSSI is adjusted to the linear amplification area, and the difference is made with the target gain value to obtain the total gain that needs to be adjusted; the gain gear value of the amplifier in the radio frequency front-end circuit that needs to be turned on is calculated according to the total gain that needs to be adjusted and sent to the radio frequency front-end circuit; the gain codeword that needs to be adjusted for the radio frequency receiving circuit is calculated in the linear adjustment area and sent to the radio frequency receiving circuit; The baseband processor includes an AGC automatic gain calculation module; the AGC automatic gain calculation module determines the gain adjustment mode in the following manner: Step 1: The AGC automatic gain calculation module determines whether the air interface power in the current cycle is greater than or equal to a first threshold and whether the air interface power in multiple historical cycles before the current cycle is less than or equal to a second threshold. If so, it is determined that a rising edge of air interface power is collected in the current cycle, and the gain adjustment mode of the current cycle is determined to be AGC adjustment; wherein the first threshold is greater than the second threshold; Step 2. In the N cycles after the period from the acquisition to the period of the rising edge of the air interface power, the gain adjustment mode of the first two or three cycles is AGC adjustment, and the gain adjustment mode of the remaining N-2 or N-3 cycles is AGC maintenance; if in the N cycles after the period from the acquisition to the period of the rising edge of the air interface power, the air interface power value of each cycle is greater than or equal to the first threshold, then the gain adjustment mode of each cycle after the N cycles is determined to be AGC state lock, until the air interface power of a certain cycle signal after N cycles is less than or equal to the second threshold, or the reduction in the air interface power of a certain cycle compared with the air interface power of the previous cycle is greater than or equal to the third threshold, or the sum of the reduction in the air interface power of a certain cycle compared with the air interface power of the previous cycle plus the reduction in the air interface power of the next cycle of the cycle compared with the air interface power of the cycle is greater than or equal to the third threshold, or the current frame of the signal ends; if in the N-1 cycles starting from the period next to the period of the acquisition to the period of the rising edge of the air interface power, the air interface power value of a certain cycle is less than the first threshold again, return to step 1.

2. The AGC baseband communication device according to claim 1, wherein: The device also includes a baseband processor external memory, the external memory includes a DDR memory, the DDR memory is used to store a linear gain value code table, a fast control word gain table, and a frequency compensation table; the linear gain value code table is used to store the actual gain of the radio frequency receiving circuit under different gain code words; the fast control word gain table is used to store the actual gain value of the amplifier in the radio frequency front-end circuit under different gain gear values; The frequency compensation table is used to store the gain deviation caused by the frequency deviation of each frequency band of the signal from the center frequency point.

3. The AGC baseband communication device according to claim 2, wherein: The baseband processor also includes a power calculation module; the power calculation module is used to calculate the received signal strength RSSI of N signal points in each cycle based on the data sampled by the RF receiving circuit and calculate the air interface power value based on the actual gain amount stored in the linear gain value code table, the fast control word gain table, and the gain deviation stored in the frequency compensation table.

4. The AGC baseband communication device according to claim 3, wherein: The AGC automatic gain calculation module is used to determine the gain adjustment mode according to the air interface power value and the cycle in which it is located; if the gain adjustment mode of the current cycle is AGC adjustment, the area in which it is located is determined according to the received signal strength RSSI. If the received signal strength RSSI is in the top saturation area, the received signal strength RSSI is reduced by Δ1 to enter the linear amplification area; if the received signal strength RSSI is in the oversaturation area, the received signal strength RSSI is reduced by Δ2 to enter the linear amplification area, and the signal strength entering the linear amplification area is subtracted from the target gain value to obtain the total gain that needs to be adjusted; if the received signal strength RSSI is in the linear adjustment area, the received signal strength RSSI is subtracted from the target gain value to obtain the total gain that needs to be adjusted.

5. The AGC baseband communication device according to claim 4, wherein: The baseband processor also includes an AGC gear calculation module and an AGC gain control module; the AGC gear calculation module is used to quickly adjust the total gain that needs to be adjusted based on the total gain that needs to be adjusted and the current gain gear value status of the amplifier in the RF front-end circuit, and preferentially adjust the total gain that needs to be adjusted through the gain gear value, read the actual gain value from the fast control word gain table using the gain gear value as an index value, and divide the total gain that needs to be adjusted by the actual gain value adjusted by the gain gear value as the linear gain that needs to be adjusted; the AGC gain control module uses the linear gain that needs to be adjusted plus the gain when the gain gear value is maximum as an index to search the linear gain value code table, calculate the gain codeword based on the actual gain value in the linear gain value code table, and send it to the RF receiving circuit.

6. The AGC baseband communication device according to claim 1, wherein: The RF front-end circuit includes an RF antenna, a first low-noise amplifier, a frequency filter, and a second low-noise amplifier; the RF antenna receiving end is connected to the first low-noise amplifier input end, the first low-noise amplifier output end is connected to the frequency filter input end, the frequency filter output end is connected to the second low-noise amplifier input end, and the second low-noise amplifier output end is connected to the RF receiving circuit input end.

7. The AGC baseband communication device according to claim 1, wherein: The RF receiving circuit includes: a mixer, a low-pass filter and an ADC analog-to-digital converter; the mixer output is connected to the low-pass filter input; the low-pass filter output is connected to the ADC analog-to-digital converter analog input; the ADC analog-to-digital converter digital sampling output is connected to the baseband processor.

8. The AGC baseband communication device according to claim 7, wherein: The radio frequency receiving circuit further includes: a third low noise amplifier; an input end of the third low noise amplifier is connected to an output end of the second low noise amplifier, and an output end of the third low noise amplifier is connected to an input end of the mixer.

9. The AGC baseband communication device according to claim 8, wherein: The first to third low-noise amplifiers, frequency filters, mixers and low-pass filters all have their own digital programmable circuits. The third low-noise amplifier, mixer and low-pass filter use their own control code words to adjust the linear gain value according to each dB; the first and second low-noise amplifiers use their own gain gear values ​​to turn on or bypass the low-noise amplifiers; and the frequency filter uses the received control code words to select different frequency band areas.

Images