Baseband communication method based on automatic gain control

Abstract

The invention relates to a baseband communication method based on automatic gain control, which comprises the following steps that: at a transmitting end, a baseband processor constructs an automatic gain control (AGC) sequence and performs power normalization; at a receiving end, the baseband processor judges whether the MGC mode or the AGC mode is adopted according to the air interface power value obtained through calculation; if the MGC mode is adopted, the baseband processor receives a first target gain value sent by the upper computer to determine a total gain needing to be adjusted; if the AGC mode is adopted, the baseband processor determines a gain adjustment mode according to the air interface power value; when the gain adjustment mode is AGC adjustment, adjusting the received signal strength (RSSI) to a linear amplification region, and subtracting the received signal strength (RSSI) from a second target gain value to obtain a total gain needing to be adjusted; calculating a gain gear value of an amplifier in the radio frequency front-end circuit needing to be started according to the total gain needing to be adjusted, and issuing the gain gear value to the radio frequency front-end circuit; and calculating a gain code word needing to be adjusted by the radio frequency receiving circuit in the linear adjustment area and issuing the gain code word to the radio frequency receiving circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless baseband communication, and in particular to a baseband communication method based on automatic gain control. Background Art

[0002] Automatic gain control AGC in wireless communication is a technology used to keep the amplitude of the receiver output signal constant. The AGC function is indispensable in modern communication systems. AGC helps maintain consistent signal strength, improve the signal-to-noise ratio, and minimize distortion. In wireless communication systems, signal strength is affected by changes in the distance between the transmitter and the receiver and other factors such as obstacles and interference. AGC can ensure that the received signal always remains within the range of optimal reception. Orthogonal frequency division multiplexing OFDM signal is the current mainstream wireless communication physical layer waveform. It uses multi-carrier modulation. 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 improved data transmission rate. However, OFDM signals have a large dynamic range and the peak-to-average power of the signal is relatively high, which poses a huge challenge to AGC to quickly and accurately adjust the gain to adapt to the wide range of changes in the receiver signal.

[0003] At the same time, when the air interface signal-to-noise ratio is relatively low, it is not easy to achieve accurate and fast adjustment using only AGC control. Summary of the invention

[0004] In view of the above analysis, an embodiment of the present invention aims to provide a baseband communication method based on automatic gain control to solve the problem that it is not easy to achieve accurate and fast adjustment using only AGC control when the air interface signal-to-noise ratio is low in existing wireless communications.

[0005] The embodiment of the present invention provides a baseband communication method based on automatic gain control, comprising: at a transmitting end, a baseband processor constructs an AGC sequence and maps it to a first baseband bandwidth, performs IFFT transformation to obtain a time-domain wireless frame, performs power normalization on different data segments of the time-domain wireless frame to obtain a time-domain AGC sequence, and transmits it in sequence through a radio frequency transmitting circuit and a radio frequency front-end circuit; at a receiving end, a baseband processor calculates a received signal strength RSSI and an air interface power value of each cycle according to a digital signal input by an radio frequency receiving circuit, and determines whether to adopt an MGC mode or an AGC mode according to the air interface power value; if the MGC mode is adopted, a host computer determines a first target gain value according to the air interface power value, and the baseband processor receives the first target gain value sent by the host computer to determine the total gain that needs to be adjusted, Then the total gain that needs to be adjusted is divided into gain gear and gain codeword adjustment value, the gain gear adjustment value is sent to the RF front-end circuit, and the gain codeword adjustment value is sent to the RF receiving circuit; if the AGC mode is adopted, the baseband processor determines 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 second target gain value to obtain the total gain that needs to be adjusted; according to the total gain that needs to be adjusted, the gain gear value of the amplifier in the RF front-end circuit that needs to be turned on is calculated and sent to the RF front-end circuit; the gain codeword that needs to be adjusted for the RF receiving circuit is calculated in the linear adjustment area and sent to the RF receiving circuit.

[0006] Furthermore, the baseband processor constructs the AGC sequence formula as follows:

[0007]

[0008] Where r is the root index of the ZC sequence and r∈{1,2,3...,N ZC -1}, n = 0, 1, 2, ..., N ZC -1, N ZC is the AGC sequence length and is an odd number, and q is a natural number.

[0009] Furthermore, the baseband processor obtains the actual gain values ​​of the third low-noise amplifier, mixer, and low-pass filter in the stored RF receiving circuit under different gain codewords according to the linear gain control codeword table; the baseband processor obtains the actual gain values ​​of the amplifier in the stored RF front-end circuit under different gain gears according to the fast control word gain table; the baseband processor obtains the gain deviation caused by the frequency deviation between each frequency band of the stored signal and the center frequency according to the frequency compensation table; the air interface power value is calculated based on the actual gain value and gain deviation obtained above, and the gain gear and gain codeword that need to be sent are calculated based on the actual gain value, gain deviation, and total gain that need to be adjusted obtained above.

[0010] Furthermore, in MGC mode or AGC adjustment, the baseband processor prioritizes the quick adjustment of the total gain to be adjusted through the gain gear according to the total gain to be adjusted and the gain gear status of the amplifier in the current RF front-end circuit, reads the actual gain value from the fast control word gain table with the gain gear as the index value, and divides the total gain to be adjusted by the actual gain value adjusted by the gain gear as the linear gain to be adjusted; the AGC gain control module in the baseband processor sends the gain codeword to the RF receiving circuit in the order of preferentially allocating the linear gain to be adjusted to the third low noise amplifier, then to the mixer, and finally to the low-pass filter.

[0011] Furthermore, the baseband processor calculates the received signal strength RSSI of N signal points in each cycle based on the data sampled by the RF receiving circuit and calculates the air interface power value based on the actual gain stored in the linear gain control codeword table, the fast control word gain table, and the gain deviation stored in the frequency compensation table.

[0012] Furthermore, the baseband processor determines the gain adjustment mode according to the air interface power value and the cycle in the AGC mode; 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.

[0013] Further, judging whether to adopt the MGC mode or the AGC mode according to the air interface power value includes:

[0014] SS1: The baseband processor determines whether the air interface power of the current cycle is greater than or equal to the first threshold and whether the air interface power of multiple historical cycles is less than or equal to the second threshold. If so, it is determined that the current cycle collects the rising edge of the air interface power and enters the AGC mode from the current cycle;

[0015] Otherwise, the baseband processor determines whether the air interface power of the current cycle is greater than or equal to the fourth threshold and less than the first threshold, and whether the air interface power of multiple historical cycles is less than or equal to the second threshold. If so, the current cycle starts to enter the MGC mode;

[0016] SS2: If the current cycle collects the rising edge of the air interface power and enters the AGC mode, if the air interface power value of a certain cycle in the N-1 cycles starting from the next cycle of the current cycle is less than the second threshold again, re-enter SS1; otherwise, if the air interface power in a certain cycle after N cycles starting from the next cycle of the current cycle is less than or equal to the second threshold, or the reduction of the air interface power in a certain cycle compared with the air interface power of the previous cycle is greater than or equal to the third threshold, or the reduction of the air interface power in a certain cycle compared with the air interface power of the previous cycle plus the reduction of the air interface power in 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, re-enter SS1;

[0017] If the current period collects the rising edge of the air interface power and enters the MGC mode, the MGC mode will be adopted for multiple collection periods after the current period, until the air interface power of the signal in a period after the current period is less than or equal to the second threshold, or the air interface power in a period is greater than or equal to the first threshold, or the reduction amount of the air interface power in a period compared with the air interface power of the previous period is greater than or equal to the third threshold, or the reduction amount of the air interface power in a period compared with the previous period plus the reduction amount of the air interface power in the next period of the period compared with the air interface power of the period is greater than or equal to the third threshold, or the current frame of the signal ends and re-enters SS1;

[0018] Among them, the first threshold is greater than the fourth threshold, the fourth threshold is greater than the third threshold, and the third threshold is greater than the second threshold.

[0019] Furthermore, if the AGC mode is determined, the gain adjustment mode is determined in the following manner:

[0020] In the N cycles after the period from the acquisition to 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 rising edge of the air interface power, the air interface power value of each cycle is greater than or equal to the first threshold, the gain adjustment mode of each cycle after the N cycles is determined to be AGC state locked until the air interface power of a certain cycle after N cycles is less than or equal to the second threshold, or the reduction in 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 reduction in air interface power of a certain cycle compared with the air interface power of the previous cycle plus the reduction in 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 next cycle of the period from the acquisition to the rising edge of the air interface power, the air interface power value of a certain cycle is less than the second threshold again, re-judge whether to enter the AGC mode.

[0021] Furthermore, at the receiving end, the RF front-end circuit amplifies and filters the received signal and sends it to the RF receiving circuit. The RF receiving circuit amplifies, mixes, and converts the input signal into a digital signal and transmits it to the baseband processor.

[0022] Furthermore, the baseband processor determines the frequency band region to which the center frequency of the currently received signal belongs based on the center frequency of the currently received signal, and sends a control codeword to configure the frequency filter of the RF front-end circuit to implement gating of the frequency band region.

[0023] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0024] 1. A baseband communication method based on automatic gain control of the present invention determines whether to adopt an MGC mode or an AGC mode according to an air interface power value; if the MGC mode is adopted, a host computer determines a first target gain value according to the air interface power value, a baseband processor receives the first target gain value sent by the host computer to determine a total gain that needs to be adjusted, and then splits the total gain that needs to be adjusted into a gain gear and a gain codeword adjustment value, the gain gear adjustment value is sent to a radio frequency front-end circuit, and the gain codeword adjustment value is sent to a radio frequency receiving circuit; if the AGC mode is adopted, the baseband processor determines a gain adjustment mode according to the air interface power value, and the gain adjustment mode includes AGC adjustment, AGC retention, and AGC state locking; when the gain adjustment mode is AGC adjustment, the received signal strength RSSI is adjusted to a linear amplification region, and the total gain that needs to be adjusted is obtained by subtracting the second target gain value; 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 by the radio frequency receiving circuit is calculated in the linear adjustment region and sent to the radio frequency receiving circuit. According to the signal strength, the MGC mode or AGC mode is used; the gain is divided into multiple gain gears and linear gain adjustment values, which can quickly converge to the linear adjustment area and complete the gain adjustment to the target value within 2 to 3 cycles (256 sampling points per cycle).

[0025] 2. In the present invention, a baseband communication method based on automatic gain control is used. The transmitting end constructs an AGC sequence formula through a baseband processor. After the nq compensation amount is added, the AGC sequence has a wider bandwidth and a more complex structure in the spectrum. The enrichment of the spectrum characteristics helps to improve the anti-interference ability of the system and can better cope with various noises and interferences.

[0026] 3. The AGC mode of a baseband communication method based on automatic gain control of the present invention adds power conversion prediction and state locking functions, which can identify the arrival of effective air interface signals, and lock the gain value after the AGC segment of the effective signal of each wireless frame completes the gain adjustment, until the end of the wireless frame or the air interface power of a certain period after N periods is less than or equal to the second threshold, 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, or the reduction of the air interface power of a certain period compared with the air interface power of the previous period plus the reduction of the air interface power of the next period of the period compared with the air interface power of the period is greater than or equal to the third threshold. The AGC locking state is released. The power change prediction and AGC state locking functions of the present invention have stronger anti-disturbance capabilities for the burst synchronization of OFDM waveforms with a high peak-to-average ratio.

[0027] 4. A baseband communication method based on automatic gain control of the present invention obtains the actual gain values ​​of the third low noise amplifier, mixer, and low pass filter in the radio frequency receiving circuit stored under different gain code words according to the linear gain control code word table; the baseband processor obtains the actual gain values ​​of the amplifier in the radio frequency front end circuit stored under different gain gears according to the fast control word gain table; the baseband processor obtains the gain deviation caused by the frequency deviation of each frequency band of the stored signal and the center frequency according to the frequency compensation table; the air interface power value is calculated based on the actual gain value and gain deviation obtained above, and the gain gear and gain code words that need to be issued are calculated based on the actual gain value, gain deviation, and total gain that need to be adjusted obtained above. The linear gain control code word table, the fast control word gain table, and the frequency compensation table pre-store the actual gain values ​​of the third low noise amplifier, mixer, and low pass filter under different gain code words, the actual gain values ​​of the amplifier in the radio frequency front end circuit under different gain gear values, and the gain deviation in the table, and the results are obtained by fast table lookup in MGC adjustment and AGC adjustment, which reduces cumbersome formula calculations, avoids additional real-time calculation overhead, and improves the operation speed of fast AGC state locking.

[0028] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0030] Figure 1A flowchart of a baseband communication method based on automatic gain control according to the present invention;

[0031] Figure 2 A flow chart of a method for baseband communication method based on automatic gain control in the present invention, in which AGC is adjusted as a gain adjustment mode;

[0032] Figure 3 A structural block diagram of a device for implementing a baseband communication method based on automatic gain control according to the present invention;

[0033] Figure 4 A baseband communication method based on automatic gain control transmits an AGC segment time domain waveform in a frame according to the present invention;

[0034] Figure 5 The present invention discloses an AGC segment constellation diagram in a baseband communication method transmitting frame based on automatic gain control. DETAILED DESCRIPTION

[0035] The preferred embodiments of the present invention are 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, but are not used to limit the scope of the present invention.

[0036] A specific embodiment of the present invention discloses a baseband communication method based on automatic gain control, such as Figure 1 As shown, it specifically includes steps 1 to 3.

[0037] Step 1. At the transmitting end, the baseband processor constructs an AGC sequence and maps it to the first baseband bandwidth, performs IFFT transformation to obtain a time domain wireless frame, performs power normalization on different data segments of the time domain wireless frame to obtain a time domain AGC sequence, and transmits it in turn through the RF transmitting circuit and the RF front-end circuit; at the receiving end, the baseband processor calculates the received signal strength RSSI and the air interface power value of each cycle based on the digital signal input by the RF receiving circuit.

[0038] The baseband processor constructs the AGC sequence formula as follows:

[0039]

[0040] Where r is the root index of the ZC sequence and r∈{1,2,3...,N ZC -1}, n = 0, 1, 2, ..., N ZC -1, N ZC is the AGC sequence length and is an odd number, and q is a natural number.

[0041] The time domain waveform of the AGC segment in the transmission frame is as follows: Figure 4 shown.

[0042] The AGC segment constellation diagram in the transmit frame is as follows: Figure 5 shown.

[0043] Specifically, in the definition of the frame format: the physical layer of the wireless communication AGC device in this example adopts the OFDM broadband waveform, and the AGC sequence at the transmitting end is generated by the ZC sequence. The AGC sequence meets the CAZAC characteristics, has the characteristics of constant envelope and constant transmission power, and is suitable for OFDM systems. q After adding the nq term to the exponent, the spectrum has a wider bandwidth and a more complex structure. This enrichment of the spectrum characteristics helps to improve the system's anti-interference ability, enabling it to better cope with various noises and interferences. Adding this term can be adjusted according to the needs of the actual application scenario. This makes the AGC sequence more adaptable and flexible in different application scenarios. For example, the sequence can be frequency offset in some scenarios. Multipath effects and interference are common problems in wireless communication systems. By introducing phase adjustment and frequency offset, the sequence's anti-multipath and anti-interference capabilities can be improved, and robustness can be improved.

[0044] The AGC signal generation process includes steps S1-S8:

[0045] S1. First, specify the root index r, the AGC sequence length Nzc, and the q value. In a specific embodiment of the present invention, r is set to 23, Nzc is 39, and the q value is 11.

[0046] S2. Determine the number of points for time-frequency conversion. In a specific embodiment of the present invention, the number of points is 1024, the time domain is 1024 sampling points, and the corresponding frequency domain is 1024 subcarriers.

[0047] S3. Calculate the positions of the 39 subcarriers in the 1024 subcarriers in the frequency domain, specifically, arrange 39 subcarriers continuously from the center subcarrier position of the 1024 subcarriers.

[0048] S4. Calculate the AGC frequency domain sequence value according to formula (1).

[0049] S5. Create a frequency domain sequence capable of storing 1024 subcarriers.

[0050] S6. Store the AGC frequency domain sequence value into the frequency domain sequence according to the 39 subcarrier positions of S3.

[0051] S7. Perform IFFT transformation on the frequency domain sequence to convert from the frequency domain to the time domain.

[0052] S8. Normalize the time domain sequence, specifically by using the ratio of the number of subcarriers occupied by ZC sequences of different data segments of the time domain wireless frame (39+1=40 in this embodiment) to the number of points of the time-frequency transformation (1024 in this embodiment) as the normalization coefficient.

[0053] Specifically, the above AGC sequence is mapped to a 2MHz baseband bandwidth with an FFT point number of 1024 points (except that the zero subcarrier is a DC subcarrier and does not need to be mapped), and then IFFT and power normalization operations are performed (different data segments of a wireless frame use different numbers of subcarriers. The more subcarriers, the power will increase, and vice versa. Therefore, in order to make the power of each segment relatively constant, it is necessary to perform normalization operations on each segment to achieve the purpose of keeping the power of each segment basically stable), and a 64-point cyclic prefix is ​​added to obtain a time domain AGC sequence.

[0054] At the receiving end, the RF front-end circuit amplifies and filters the received signal and sends it to the RF receiving circuit. The RF receiving circuit amplifies, mixes, and converts the input signal into a digital signal and transmits it to the baseband processor.

[0055] The structural block diagram of the device for implementing the method of the present invention is as follows: Figure 3 shown.

[0056] Specifically, 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.

[0057] 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.

[0058] After passing through the RF front-end circuit, the signal enters the RF receiver. This design uses a zero intermediate frequency circuit, which has a low-pass filter, mixer, low-pass filter and ADC analog-to-digital converter inside. This part converts the RF signal into a digital baseband signal. The receiving gain codeword of this part is written into the gain register of the receiver through SPI communication.

[0059] The radio frequency receiving circuit further comprises: 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.

[0060] 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 realize the function of adjusting the linear gain value according to each dB through their own control code words; the first and second low noise amplifiers realize the turning on or bypassing of the low noise amplifiers through their own gain gear values; the frequency filter realizes the selection of different frequency band areas through the received control code words.

[0061] The RF front-end circuit also includes a RF switch, which is used to switch the input channel and the output channel of the device.

[0062] The baseband processor determines the frequency band region to which the center frequency of the current received signal belongs based on the center frequency of the received signal, and sends a control codeword to configure the frequency filter of the RF front-end circuit to achieve gating of the frequency band region.

[0063] In a specific embodiment of the present invention, the baseband processor is divided into five frequency band areas according to the frequency range of the designated frequency filter as follows: BAND64: 225-330 MHz, BAND65: 330-480 MHz, BAND66: 480-700 MHz, BAND67: 700-1100 MHz, and BAND68: 1100-1700 MHz.

[0064] The calculation formula of the frequency filter center frequency control codeword is:

[0065] Control code word = (f x -f low ) / (f high -f low )×250;f x is the tuning center frequency within the frequency band, f low is the lowest frequency in the segment, f high is the highest frequency in the segment, 250 is the total number of steps in the segment, if the calculated result is a decimal place, it should be rounded off to an integer. For example: the frequency code of the input 255MHz signal = (255-225) / (655-225)×250=30 / 430×250=17.4; rounded to 17; converted to hexadecimal result is 0x11.

[0066] The required sub-band tuning center frequency can be selected in each frequency band area. The sub-band tuning center frequency that can be selected by the control code word 0x11 is 255 MHz.

[0067] The baseband processor calculates the received signal strength RSSI of N signal points in each cycle based on the data sampled by the RF receiving circuit and calculates the air interface power value based on the actual gain stored in the linear gain control codeword table, the fast control word gain table, and the gain deviation stored in the frequency compensation table.

[0068] Specifically, the RF receiving circuit continuously sends the digital sampling signal to the baseband processor, the baseband processor stores the digital sampling signal in the data cache through DMA, and then configures the AGC timer to periodically trigger the AGC timing interrupt. A specific embodiment of the present invention uses N=256 digital sampling points as a cycle, enters the interrupt, and calculates the average value of the RSSI of the signal in each cycle as the received signal strength RSSI.

[0069] The method for calculating the air interface power value is to first calculate the received signal strength RSSI power value of each period, and then convert the RSSI power value into a logarithmic value db.

[0070] The calculation formula for received signal strength RSSI is:

[0071]

[0072] Where N = 256, I i is the I component of the ith digital sampling signal, Q i is the Q component of the i-th digital sampling signal.

[0073] The baseband processor obtains the actual gain values ​​of the third low-noise amplifier, mixer, and low-pass filter in the stored RF receiving circuit under different gain codewords according to the linear gain control codeword table; the baseband processor obtains the actual gain values ​​of the amplifier in the stored RF front-end circuit under different gain gears according to the fast control word gain table; the baseband processor obtains the gain deviation caused by the frequency deviation between each frequency band and the center frequency of the stored signal according to the frequency compensation table; the air interface power value is calculated based on the actual gain value and gain deviation obtained above, and the gain gear and gain codeword that need to be sent are calculated based on the actual gain value, gain deviation, and total gain that need to be adjusted obtained above.

[0074] Specifically, the air interface power value is calculated by reverse calculation of the received signal strength RSSI based on the actual gain stored in the linear gain control codeword table and the fast control word gain table corresponding to the gain gear value used in the current cycle, and the gain deviation stored in the frequency compensation table corresponding to the gain codeword used in the current cycle.

[0075] Step 2: Determine whether to use MGC mode or AGC mode according to the air interface power value.

[0076] The determining of whether to adopt the MGC mode or the AGC mode according to the air interface power value includes:

[0077] SS1: The baseband processor determines whether the air interface power of the current cycle is greater than or equal to the first threshold and whether the air interface power of multiple historical cycles is less than or equal to the second threshold. If so, it is determined that the current cycle collects the rising edge of the air interface power and enters the AGC mode from the current cycle;

[0078] Otherwise, the baseband processor determines whether the air interface power of the current cycle is greater than or equal to the fourth threshold and less than the first threshold, and whether the air interface power of multiple historical cycles is less than or equal to the second threshold. If so, the current cycle starts to enter the MGC mode;

[0079] SS2: If the current cycle collects the rising edge of the air interface power and enters the AGC mode, if the air interface power value of a certain cycle in the N-1 cycles starting from the next cycle of the current cycle is less than the second threshold again, re-enter SS1; otherwise, if the air interface power in a certain cycle after N cycles starting from the next cycle of the current cycle is less than or equal to the second threshold, or the reduction of the air interface power in a certain cycle compared with the air interface power of the previous cycle is greater than or equal to the third threshold, or the reduction of the air interface power in a certain cycle compared with the air interface power of the previous cycle plus the reduction of the air interface power in 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, re-enter SS1;

[0080] If the current period collects the rising edge of the air interface power and enters the MGC mode, the MGC mode will be adopted for multiple collection periods after the current period, until the air interface power of the signal in a period after the current period is less than or equal to the second threshold, or the air interface power in a period is greater than or equal to the first threshold, or the reduction amount of the air interface power in a period compared with the air interface power of the previous period is greater than or equal to the third threshold, or the reduction amount of the air interface power in a period compared with the previous period plus the reduction amount of the air interface power in the next period of the period compared with the air interface power of the period is greater than or equal to the third threshold, or the current frame of the signal ends and re-enters SS1;

[0081] Among them, the first threshold is greater than the fourth threshold, the fourth threshold is greater than the third threshold, and the third threshold is greater than the second threshold.

[0082] Specifically, in a specific embodiment of the present invention, the baseband processor can automatically switch between the two modes of automatic gain control AGC and manual gain control MGC in real time, enter the AGC mode under normal signal-to-noise ratio conditions, and enter the MGC mode under low signal-to-noise ratio conditions. If the air interface power of multiple historical periods is less than or equal to the second threshold, the multiple historical periods are regarded as noise segments, if the current period collects the rising edge of the air interface power, if the air interface power of the current period is greater than or equal to the first threshold, it is considered that the current period is in a normal signal-to-noise ratio situation, and if the air interface power of the current period is greater than or equal to the fourth threshold and less than the first threshold, it is considered that the current period is in a low signal-to-noise ratio situation.

[0083] Step 3: If the MGC mode is adopted, the host computer determines the first target gain value according to the air interface power value, the baseband processor receives the first target gain value sent by the host computer to determine the total gain that needs to be adjusted, and then splits the total gain that needs to be adjusted into a gain gear and a gain codeword adjustment value, the gain gear adjustment value is sent to the RF front-end circuit, and the gain codeword adjustment value is sent to the RF receiving circuit; if the AGC mode is adopted, the baseband processor determines 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 total gain that needs to be adjusted is obtained by subtracting the second target gain value; the gain gear value of the amplifier in the RF 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 RF front-end circuit; the gain codeword that needs to be adjusted for the RF receiving circuit is calculated in the linear adjustment area and sent to the RF receiving circuit.

[0084] Specifically, if the MGC mode is adopted, the host computer determines the first target gain value according to the air interface power value, the baseband processor receives the first target gain value sent by the host computer, and subtracts the first target gain value from the current baseband processor received signal strength to obtain the total gain that needs to be adjusted.

[0085] The flow chart of the method using AGC adjustment as the gain adjustment mode is as follows Figure 2 shown.

[0086] If the AGC mode is determined, the gain adjustment mode is determined as follows:

[0087] In the N cycles after the period from the acquisition to 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 rising edge of the air interface power, the air interface power value of each cycle is greater than or equal to the first threshold, the gain adjustment mode of each cycle after the N cycles is determined to be AGC state locked until the air interface power of a certain cycle after N cycles is less than or equal to the second threshold, or the reduction in 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 reduction in air interface power of a certain cycle compared with the air interface power of the previous cycle plus the reduction in 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 next cycle of the period from the acquisition to the rising edge of the air interface power, the air interface power value of a certain cycle is less than the second threshold again, re-judge whether to enter the AGC mode.

[0088] Specifically, the AGC gain adjustment flag value can be set to TRUE or FALSE. Initialized to FALSE, the AGC gain adjustment flag is set to FALSE in the AGC hold state, and the flag is set to TRUE after the AGC state is locked.

[0089] The power conversion trend prediction and AGC locking capabilities are added during the AGC gain adjustment process. First, the length of the AGC segment of the frame header of the wireless frame is obtained, the sudden change of air interface power and the current noise threshold statistics are monitored, and the current signal is calculated according to the air interface power of the current cycle and multiple historical cycles. Whether it is in the noise segment or the valid waveform segment, the start and end boundaries of the valid signal are predicted and judged. After the AGC segment gain adjustment of the signal frame is completed, the gain is locked until the end of the wireless signal frame. This design avoids the malfunction of the AGC due to energy changes or additional noise in the data frame after the AGC segment, reduces the probability of AGC false triggering caused by average power fluctuations due to the high peak-to-average ratio of the OFDM waveform, and superimposed air interface interference signals in the frame time period outside the AGC segment will not cause AGC false triggering, thereby improving the anti-interference capability.

[0090] Regardless of whether it is determined to be MGC mode or AGC mode, gain adjustment must be performed through the linear gain control codeword table, fast control word gain table, and frequency compensation table. The linear gain control codeword table, fast control word gain table, and frequency compensation table are multiple data structures, which are used to record the actual gain value obtained by measuring and calibrating each step gain gear value or gain codeword in advance. The frequency compensation table is used to compensate for the gain deviation caused by the frequency deviation between each frequency band of the actual received signal and the center frequency (because the sampling is based on the center frequency data, but what is actually needed is that the data is within a frequency band in the frequency domain, and the frequency gain outside the center frequency has a gain deviation from the center frequency). The frequency deviation is stepped by 5Mhz, and the deviation from the gain of the center frequency is calculated and stored in the frequency compensation table.

[0091] In MGC mode or AGC adjustment, the baseband processor prioritizes the gain gear 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 status of the amplifier in the RF front-end circuit, reads the actual gain value from the fast control word gain table using the gain gear as an index value, and divides the total gain that needs to be adjusted by the actual gain value adjusted by the gain gear as the linear gain that needs to be adjusted; the AGC gain control module in the baseband processor sends the gain codeword to the RF receiving circuit in the order of preferentially allocating the linear gain that needs to be adjusted to the third low-noise amplifier, then to the mixer, and finally to the low-pass filter.

[0092] In AGC mode, the baseband processor determines the gain adjustment mode according to the air interface power value and the cycle it is in; if the gain adjustment mode of the current cycle is AGC adjustment, the area where 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.

[0093] Specifically, the total gain that needs to be adjusted is calculated as follows:

[0094] 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 logarithmic value is 96.3296. The gain adjustment range of the target gain value is set to 2 11 , converted to a logarithmic value of 20log 10 211 , the logarithm of the target gain value is 66.2266.

[0095] After obtaining the maximum sampling value and the target gain value, the interval division begins:

[0096] The sampling signal range of the top saturation area is between 15 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. This range adjustment reduces the gain △1=25db.

[0097] The sampling signal range of the oversaturation zone is between 13 bits and 15 bits, and the logarithmic value range of the oversaturation zone is 20log 10 2 13 ~20log 10 2 15 , i.e. 78.2678~90.3090. The gain reduction in this range is △2=18db.

[0098] The area less than 13 bits is a linear amplification area, which includes a linear adjustment area and a gain holding area.

[0099] 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 is 20log 10 2 12 ~20log 10 2 13 , the interval range is 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 and 78.2678.

[0100] Adjust the target gain value to the 11-bit sampling signal range as the adjusted target value, and calculate the logarithmic value 20log 10 2 11 , the logarithm of the target gain value is 66.2266.

[0101] The logarithmic value of the top saturation area and the oversaturation area after the gain is reduced and the logarithmic value of the sampled signal in the linear adjustment area are adjusted to the gain holding area. The method is to use the logarithmic value of the signal strength after the top saturation area and the oversaturation area are adjusted to the linear amplification area and the logarithmic value of the signal strength of the received signal strength RSSI in the linear adjustment area minus 66.2266db to find the fast control word gain table and the linear gain control codeword table, and send the gain gear value and gain codeword to be adjusted to the RF front-end circuit and the RF receiving circuit to realize AGC adjustment. If the RSSI logarithmic value calculated by the baseband processor after the AGC adjustment enters the gain holding area of ​​66.2266db±3db, it is considered that the AGC adjustment is completed. The logarithmic value of the signal strength that jumps out of the gain holding area is: <60db or >72db.

[0102] Specifically, the gain adjustment mode judgment stage is entered, and the gain interval judgment is performed according to the received signal strength RSSI calculated by the current baseband processor. The gain interval is divided into the top saturation area, the oversaturation area, the linear adjustment area and the gain retention area. The gain adjustment value of this round is obtained according to the interval where the received signal strength RSSI is located. When the received signal strength RSSI is in the gain retention interval, the gain will remain unchanged. When the received signal strength RSSI is in the top saturation area, it indicates that the gain has entered the nonlinear area 1, so the gain is reduced by Δ1, and a specific embodiment of the present invention is Δ1=25db, leaving the top saturation area and entering the linear amplification area. When the received signal strength RSSI is in the oversaturation area, it indicates that the gain has entered the nonlinear area 2, and the gain is reduced by Δ2, and a specific embodiment of the present invention is Δ2=18db, leaving the oversaturation area. When the received signal strength RSSI is in the linear adjustment area, the gain is directly adjusted to reach the target value, so the total gain that needs to be adjusted is obtained by subtracting the received signal strength RSSI from the target gain value.

[0103] Compared with the prior art, the baseband communication method based on automatic gain control provided in this embodiment determines whether to adopt the MGC mode or the AGC mode according to the air interface power value; if the MGC mode is adopted, the host computer determines the first target gain value according to the air interface power value, the baseband processor receives the first target gain value sent by the host computer to determine the total gain that needs to be adjusted, and then splits the total gain that needs to be adjusted into a gain gear and a gain codeword adjustment value, the gain gear adjustment value is sent to the RF front-end circuit, and the gain codeword adjustment value is sent to the RF receiving circuit; if the AGC mode is adopted, the baseband processor determines the gain adjustment mode according to the air interface power value, and the gain adjustment mode includes AGC adjustment, AGC retention, and AGC state locking; when the gain adjustment mode is AGC adjustment, the received signal strength RSSI is adjusted to the linear amplification area, and the total gain that needs to be adjusted is obtained by subtracting the second target gain value; the gain gear value of the amplifier in the RF 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 RF front-end circuit; the gain codeword that needs to be adjusted by the RF receiving circuit is calculated in the linear adjustment area and sent to the RF receiving circuit. According to the signal strength, the MGC mode or AGC mode is used; the gain is divided into multiple gain gears and linear gain adjustment values, which can quickly converge to the linear adjustment area, and the gain adjustment to the target value can be completed within 2 to 3 cycles (256 sampling points per cycle). The baseband communication method provided in this embodiment constructs the AGC sequence formula through the baseband processor. After adding the nq compensation amount, the AGC sequence has a wider bandwidth and more complex structure in the spectrum. This enrichment of the spectrum characteristics helps to improve the anti-interference ability of the system and can better cope with various noises and interferences. In the method provided in this embodiment, the AGC mode adds power change prediction and state locking functions, which can identify the arrival of valid air interface signals, and lock the gain value after the gain adjustment is completed in the AGC segment of the valid signal of each wireless frame, until the end of the wireless frame or the air interface power of a certain period after N periods is less than or equal to the second threshold, 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, or the reduction of the air interface power of a certain period compared with the air interface power of the previous period plus the reduction of the air interface power of the next period of the period compared with the air interface power of the period is greater than or equal to the third threshold. The AGC locking state is released. The power change prediction and AGC state locking functions of the present invention have stronger anti-disturbance capabilities for the burst synchronization of OFDM waveforms with a higher peak-to-average ratio.In the method provided in this embodiment, the actual gain values ​​of the third low noise amplifier, mixer, and low pass filter in the stored radio frequency receiving circuit under different gain code words are obtained according to the linear gain control code word table; the baseband processor obtains the actual gain values ​​of the amplifier in the stored radio frequency front-end circuit under different gain gears according to the fast control word gain table; the baseband processor obtains the gain deviation caused by the frequency deviation of each frequency band of the stored signal from the center frequency according to the frequency compensation table; the air interface power value is calculated based on the actual gain value and gain deviation obtained above, and the gain gear and gain code words that need to be issued are calculated based on the actual gain value, gain deviation, and total gain that need to be adjusted obtained above. The linear gain control code word table, the fast control word gain table, and the frequency compensation table pre-store the actual gain values ​​of the third low noise amplifier, mixer, and low pass filter under different gain code words, the actual gain values ​​of the amplifier in the radio frequency front-end circuit under different gain gear values, and the gain deviation in the table, and the results are obtained by fast table lookup in MGC adjustment and AGC adjustment, which reduces cumbersome formula calculations, avoids additional real-time calculation overhead, and improves the operation speed of fast AGC state locking.

[0104] Those skilled in the art will appreciate that all or part of the processes of the above-mentioned embodiments can be implemented by instructing related hardware through a computer program, and the program can be stored in a computer-readable storage medium, wherein the computer-readable storage medium is a disk, an optical disk, a read-only storage memory, or a random access memory, etc.

[0105] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A baseband communication method based on automatic gain control, characterized in that: include: At the transmitting end, the baseband processor constructs an AGC sequence and maps it to the first baseband bandwidth, performs IFFT transformation to obtain a time domain wireless frame, performs power normalization on different data segments of the time domain wireless frame to obtain a time domain AGC sequence, and transmits it in sequence through the RF transmitting circuit and the RF front-end circuit; at the receiving end, the baseband processor calculates the received signal strength RSSI and the air interface power value of each cycle according to the digital signal input by the RF receiving circuit, and determines whether to use the MGC mode or the AGC mode according to the air interface power value; if the MGC mode is used, the host computer determines the first target gain value according to the air interface power value, and the baseband processor receives the first target gain value sent by the host computer to determine the total gain that needs to be adjusted Gain, and then the total gain to be adjusted is divided into a gain gear and a gain codeword adjustment value, the gain gear adjustment value is sent to the RF front-end circuit, and the gain codeword adjustment value is sent to the RF receiving circuit; if the AGC mode is adopted, the baseband processor determines 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 second target gain value to obtain the total gain to be adjusted; the gain gear value of the amplifier in the RF front-end circuit to be turned on is calculated according to the total gain to be adjusted and sent to the RF front-end circuit; In the linear adjustment region, the gain codeword required to be adjusted by the radio frequency receiving circuit is calculated and sent to the radio frequency receiving circuit.

2. The baseband communication method according to claim 1, characterized in that: The baseband processor constructs the AGC sequence formula as follows: Where r is the root index of the ZC sequence and r∈{1,2,3...,N ZC -1}, n = 0, 1, 2, ..., N ZC -1, N ZC is the AGC sequence length and is an odd number, and q is a natural number.

3. The baseband communication method according to claim 1, characterized in that: The baseband processor obtains the actual gain values ​​of the third low noise amplifier, the mixer, and the low pass filter in the radio frequency receiving circuit under different gain code words according to the linear gain control code word table; The baseband processor obtains the actual gain value of the amplifier in the stored RF front-end circuit at different gain levels according to the fast control word gain table; the baseband processor obtains the gain deviation caused by the frequency deviation of each frequency band of the stored signal from the center frequency according to the frequency compensation table; the air interface power value is calculated based on the actual gain value and gain deviation obtained above, and the gain level and gain codeword that need to be sent are calculated based on the actual gain value, gain deviation and total gain that need to be adjusted obtained above.

4. The baseband communication method according to claim 3, characterized in that: In MGC mode or AGC adjustment, the baseband processor prioritizes the gain gear 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 status of the amplifier in the RF front-end circuit, reads the actual gain value from the fast control word gain table using the gain gear as an index value, and divides the total gain that needs to be adjusted by the actual gain value adjusted by the gain gear as the linear gain that needs to be adjusted; the AGC gain control module in the baseband processor sends the gain codeword to the RF receiving circuit in the order of preferentially allocating the linear gain that needs to be adjusted to the third low-noise amplifier, then to the mixer, and finally to the low-pass filter.

5. The baseband communication method according to claim 4, characterized in that: The baseband processor calculates the received signal strength RSSI of N signal points in each cycle based on the data sampled by the RF receiving circuit, and calculates the air interface power value based on the actual gain stored in the linear gain control codeword table, the fast control word gain table, and the gain deviation stored in the frequency compensation table.

6. The baseband communication method according to claim 5, characterized in that: In AGC mode, the baseband processor determines the gain adjustment mode according to the air interface power value and the cycle it is in; if the gain adjustment mode of the current cycle is AGC adjustment, the area where 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.

7. The baseband communication method according to claim 1, characterized in that: The determining of whether to adopt the MGC mode or the AGC mode according to the air interface power value includes: SS1: The baseband processor determines whether the air interface power of the current cycle is greater than or equal to the first threshold and whether the air interface power of multiple historical cycles is less than or equal to the second threshold. If so, it is determined that the current cycle collects the rising edge of the air interface power and enters the AGC mode from the current cycle; Otherwise, the baseband processor determines whether the air interface power of the current cycle is greater than or equal to the fourth threshold and less than the first threshold, and whether the air interface power of multiple historical cycles is less than or equal to the second threshold. If so, the current cycle starts to enter the MGC mode; SS2: If the current cycle collects the rising edge of the air interface power and enters the AGC mode, if the air interface power value of a certain cycle in the N-1 cycles starting from the next cycle of the current cycle is less than the second threshold again, re-enter SS1; otherwise, if the air interface power in a certain cycle after N cycles starting from the next cycle of the current cycle is less than or equal to the second threshold, or the reduction of the air interface power in a certain cycle compared with the air interface power of the previous cycle is greater than or equal to the third threshold, or the reduction of the air interface power in a certain cycle compared with the air interface power of the previous cycle plus the reduction of the air interface power in 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, re-enter SS1; If the current period collects the rising edge of the air interface power and enters the MGC mode, the MGC mode will be adopted for multiple collection periods after the current period, until the air interface power of the signal in a period after the current period is less than or equal to the second threshold, or the air interface power in a period is greater than or equal to the first threshold, or the reduction amount of the air interface power in a period compared with the air interface power of the previous period is greater than or equal to the third threshold, or the reduction amount of the air interface power in a period compared with the previous period plus the reduction amount of the air interface power in the next period of the period compared with the air interface power of the period is greater than or equal to the third threshold, or the current frame of the signal ends and re-enters SS1; Among them, the first threshold is greater than the fourth threshold, the fourth threshold is greater than the third threshold, and the third threshold is greater than the second threshold.

8. The baseband communication method according to claim 7, characterized in that: If the AGC mode is determined, the gain adjustment mode is determined as follows: In the N cycles after the period from the acquisition to 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 rising edge of the air interface power, the air interface power value of each cycle is greater than or equal to the first threshold, the gain adjustment mode of each cycle after the N cycles is determined to be AGC state locked until the air interface power of a certain cycle after N cycles is less than or equal to the second threshold, or the reduction in 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 reduction in air interface power of a certain cycle compared with the air interface power of the previous cycle plus the reduction in 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 next cycle of the period from the acquisition to the rising edge of the air interface power, the air interface power value of a certain cycle is less than the second threshold again, re-judge whether to enter the AGC mode.

9. The baseband communication method according to claim 1, characterized in that: At the receiving end, the RF front-end circuit amplifies and filters the received signal and sends it to the RF receiving circuit. The RF receiving circuit amplifies, mixes, and converts the input signal into a digital signal and transmits it to the baseband processor.

10. The baseband communication method according to claim 9, characterized in that: The baseband processor determines the frequency band region to which the center frequency of the current received signal belongs based on the center frequency of the received signal, and sends a control codeword to configure the frequency filter of the RF front-end circuit to achieve gating of the frequency band region.

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