CN110601704B

CN110601704B - Method, apparatus, computer device and readable storage medium for reducing reception noise

Info

Publication number: CN110601704B
Application number: CN201910875170.7A
Authority: CN
Inventors: 周易; 蒋群; 羊金山; 邓扬; 樊欢; 朱露敏
Original assignee: Sunwave Communications Co Ltd
Current assignee: Sunwave Communications Co Ltd
Priority date: 2019-09-17
Filing date: 2019-09-17
Publication date: 2021-12-14
Anticipated expiration: 2039-09-17
Also published as: CN110601704A; WO2021052354A1

Abstract

The application relates to a method, a device, computer equipment and a readable storage medium for reducing receiving background noise, which comprises the steps of receiving a radio frequency signal, and acquiring the bandwidth and the central frequency point of the radio frequency signal; acquiring a corrected local oscillation frequency point according to the bandwidth and the central frequency point of the radio frequency signal; and sampling the radio frequency signal according to the corrected vibration frequency point to form a baseband signal so as to enable the central direct current signal to deviate from the bandwidth range of the baseband signal. According to the technical scheme, the local oscillation frequency point is corrected by calculating the central frequency point and the signal bandwidth of the radio frequency signal used in the actual existing network, and the radio frequency signal is sampled to form a baseband signal according to the corrected local oscillation frequency point, so that the uplink background of the base station cannot count the central direct current signal, and the problem that the central direct current signal affects the bottom noise in the bandwidth of the baseband signal is solved.

Description

Method, apparatus, computer device and readable storage medium for reducing reception noise

Technical Field

The present invention relates to the field of communications technologies, and in particular, to a method and an apparatus for reducing receive noise floor, a computer device, and a readable storage medium.

Background

At present, in wireless communication, communication base stations such as a macro station, a BBU (base band unit), a micro macro station and a pico base station have high requirements on received background noise, and generally require that an uplink background noise average value or the absolute power of a single RB block is less than-110 dBm. Therefore, higher requirements are put on the background noise of Distributed equipment such as a Distributed Antenna System (DAS) and a repeater. The 4G frequency bands of the mobile communication are 1.9G, 2.3G, 2.6G, 1.8G and 2.1G, and the 5G frequency bands of the mobile communication are 2.6G, 4.9G and 3.5G. Radio frequency bands used by 4G and 5G systems are generally higher, and background noise of wireless communication equipment working in a high frequency band has great influence on EVM and noise coefficient of signals, and directly influences communication performance of 4G and 5G equipment. This makes the next-stage distributed equipment connected with the base station by the feeder line put higher requirements on the uplink receiving background noise of the DAS and the repeater station. The use of wireless image transmission and wireless data transmission is also very extensive, like fields such as unmanned aerial vehicle, thing networking, intelligent industrial control. The performance and the transmission range of wireless image transmission and wireless data transmission can be greatly improved by reducing the bottom noise of the wireless receiver.

Transceiver chips (such as AD936x and AD937x series of ADI company) are widely applied to various wireless communication devices at present, and integrate a high-speed ADC and a high-speed DAC, a radio frequency conversion circuit, a clock phase-locked loop circuit and a gain control circuit, and are provided with a digital control IP core. The Transceiver chip is highly integrated, so that the volume and the power consumption of the equipment are greatly reduced. However, the Transceiver chips all have the problem of direct current of a central frequency point, so that the receiving bottom noise of the communication base station can be raised.

Disclosure of Invention

The application provides a method, a device, computer equipment and a readable storage medium for reducing the receiving background noise, which can reduce the receiving background noise of a base station under the condition of ensuring the performance of the base station to the maximum extent.

A method of reducing receive noise floor, the method comprising:

receiving a radio frequency signal, and acquiring the bandwidth and the central frequency point of the radio frequency signal;

acquiring a corrected local oscillation frequency point according to the bandwidth and the central frequency point of the radio frequency signal;

and sampling the radio frequency signal according to the corrected local frequency vibration point to form a baseband signal so as to enable a central direct current signal to deviate from the bandwidth range of the baseband signal.

In an embodiment, the method further comprises:

and synchronously carrying out frequency offset processing on the central direct current signal and the baseband signal so as to enable the central frequency point of the baseband signal to fall on zero frequency.

In an embodiment, the synchronizing the central dc signal and the baseband signal with frequency offset processing includes:

calculating frequency deviation according to the corrected local oscillation frequency point and the central frequency point of the radio frequency signal;

and synchronously carrying out frequency offset processing on the central direct current signal and the baseband signal according to the frequency offset.

In an embodiment, the obtaining a modified local oscillation frequency point according to the bandwidth and the central frequency point of the radio frequency signal includes:

configuring the bandwidth of the FIR filter; and comparing the relationship between the bandwidth of the radio frequency signal and a preset bandwidth.

In an embodiment, the comparing the relationship between the bandwidth of the radio frequency signal and the preset bandwidth includes:

if the bandwidth of the radio frequency signal is smaller than the preset bandwidth, calculating a frequency deviation value A (B/2) is larger than or equal to A and smaller than or equal to (C-B)/2 according to the bandwidth of the radio frequency signal and the center frequency point, wherein B is the bandwidth of the radio frequency signal, and C is the bandwidth of an FIR filter; calculating the corrected local oscillation frequency point according to the frequency offset value A and the central frequency point of the radio frequency signal;

if the bandwidth of the radio frequency signal is larger than the preset bandwidth, calculating a corrected local oscillation frequency point according to the bandwidth and the central frequency point of each carrier signal forming the radio frequency signal, wherein the corrected local oscillation frequency point is positioned in a transition band among a plurality of carrier signals.

In an embodiment, when the bandwidth of the radio frequency signal is greater than a preset bandwidth, the calculating and correcting the local oscillation frequency point according to the bandwidth and the central frequency point of each carrier signal constituting the radio frequency signal includes:

calculating a first transition band of each carrier signal according to the bandwidth of each carrier signal;

and calculating the corrected local oscillation frequency point according to the bandwidth, the central frequency point and the first transition band of each carrier signal.

In one embodiment, the bandwidth of the FIR filter is equal to the bandwidth of the radio frequency signal.

An apparatus for reducing receive noise floor, the apparatus comprising:

the first acquisition module is used for receiving a radio frequency signal and acquiring the bandwidth and the central frequency point of the radio frequency signal;

the second acquisition module is used for acquiring a corrected local oscillation frequency point according to the bandwidth and the central frequency point of the radio frequency signal;

and the sampling module is used for sampling the radio-frequency signal according to the corrected local frequency-oscillating point to form a baseband signal so as to enable the central direct-current signal to deviate from the bandwidth of the baseband signal.

A computer device comprising a memory storing a computer program and a processor implementing the steps of the above method when executing the computer program.

A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the steps of the above-mentioned method.

The method, the device, the computer equipment and the readable storage medium for reducing the receiving background noise provided by the embodiment of the application comprise the steps of receiving a radio frequency signal, and acquiring the bandwidth and the central frequency point of the radio frequency signal; acquiring a corrected local oscillation frequency point according to the bandwidth and the central frequency point of the radio frequency signal; and sampling the radio frequency signal according to the corrected local frequency vibration point to form a baseband signal so as to enable a central direct current signal to deviate from the bandwidth range of the baseband signal. According to the technical scheme, the local oscillation frequency point is corrected by calculating the central frequency point and the signal bandwidth of the radio frequency signal used in the actual existing network, and the radio frequency signal is sampled to form a baseband signal according to the corrected local oscillation frequency point, so that the uplink background of the base station cannot count the central direct current signal, and the problem that the central direct current signal affects the bottom noise in the bandwidth of the baseband signal is solved.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a flow chart of a method for reducing receive noise floor according to an embodiment;

FIG. 2 is a schematic sampling diagram of a conventional Transceiver chip according to an embodiment;

fig. 3 is a flowchart of calculating a modified local oscillation frequency point according to an embodiment;

FIG. 4 is a schematic sampling diagram of a Transceiver chip according to the present application;

FIG. 5 is a schematic sampling diagram of a Transceiver chip according to the present application according to another embodiment;

FIG. 6 is a diagram illustrating an embodiment of frequency offset processing for synchronization between a baseband signal and a central DC signal;

FIG. 7 is a diagram illustrating a frequency offset process for synchronizing a baseband signal with a central DC signal according to another embodiment;

FIG. 8 is a block diagram of an apparatus for reducing receive noise floor according to an embodiment;

FIG. 9 is an internal block diagram of a computer device provided in one embodiment.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present application more comprehensible, embodiments accompanying the present application are described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth to provide a thorough understanding of the present application, and in the accompanying drawings, preferred embodiments of the present application are set forth. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. This application is capable of embodiments in many different forms than those described herein and those skilled in the art will be able to make similar modifications without departing from the spirit of the application and it is therefore not intended to be limited to the specific embodiments disclosed below.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present application, "plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise. In the description of the present application, "a number" means at least one, such as one, two, etc., unless specifically limited otherwise.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Fig. 1 is a flowchart of a method for reducing a received noise floor according to an embodiment, and as shown in fig. 1, the method for reducing the received noise floor includes steps 110 to 130, where:

step 110, receiving the radio frequency signal, and acquiring the bandwidth and the center frequency point of the radio frequency signal.

Because the requirement of the next-stage distribution equipment connected with the base station, such as DAS or repeater, on receiving background noise is higher, the method for reducing the receiving background noise provided by the invention is suitable for DAS, repeater and other equipment. The method of the present invention will be described below by taking DAS as an example only. Typically, the DAS is composed of a main near-end Unit (AU), a Remote Unit (RU), and a Radio Remote Unit (RRU). The channels of the remote units RU receive the uplink signals of the external terminal, transmit the uplink signals to the near-end unit AU through transmission media such as optical fibers and network cables, and transmit the processed uplink signals to the RRU.

After AU equipment in the DAS receives downlink radio frequency signals, FPGA chips of the AU equipment transmit information of the radio frequency signals to the FPGA on the RU equipment through optical fibers, and ARM chips of the RU equipment read the information of the FPGA on the RU. Specifically, in the 3GPP standard and the spectrum planning in the chinese area, the central channel number determines the central frequency point of the uplink and downlink signals, so that the bandwidths of the uplink and downlink signals of all mobile, internet and telecommunication public network wireless communication frequency bands are the same, and the central frequency points of the uplink and downlink signals correspond to each other. After AU equipment in the DAS receives the downlink radio frequency signals, the FPGA chip of the AU equipment judges the central channel number and the actual effective bandwidth of the input signals, so that the central frequency point and the bandwidth of the uplink radio frequency signals corresponding to the RU end can be known, and information is transmitted to the FPGA chip of the RU end through optical fibers. After acquiring the central frequency point and the bandwidth of the downlink radio frequency signal, the AU device broadcasts the central frequency point and the bandwidth of the downlink radio frequency signal to all the RU devices cascaded with the AU device, and informs each RU device of the central frequency point and the bandwidth of the radio frequency signal of the channel.

And step 120, acquiring a corrected local oscillation frequency point according to the bandwidth and the central frequency point of the radio frequency signal.

Step 130, sampling the radio frequency signal according to the corrected local frequency point to form a baseband signal, so that the central direct current signal deviates from the bandwidth range of the baseband signal.

The radio frequency signal forms a baseband signal after being sampled by the local oscillator signal, and the central frequency point of the baseband signal is obtained by subtracting the local oscillator frequency point of the local oscillator signal from the central frequency point of the radio frequency signal in the sampling process. The resulting baseband signal is centered at the center frequency point, and its effective bandwidth is related to the configurable bandwidth of the digital FIR filter of the AD936x chip RX at the RU end. Namely, the baseband signal formed after sampling is the signal with the bandwidth configured by the FIR filter, centered at the central frequency point obtained after sampling the radio frequency signal according to the local oscillation signal of the modified local oscillation frequency point.

As shown in fig. 2, in a conventional sampling process, a radio frequency signal (refer to a left graph) with a bandwidth of 20M is shifted to zero frequency (refer to a right graph) after being sampled by a local oscillator signal, and then digital FIR filtering is performed. And the local oscillation frequency point of the local oscillation signal is equal to the central frequency point of the radio frequency signal. In the right diagram of fig. 2, the dashed trapezoid frame is a digital FIR filter, the solid line is a baseband signal, the dashed line is a digital FIR filter bandwidth of RX, and the straight line with a point is a dc signal, where the central dc signal is in the baseband signal band. It should be noted that, in the conventional technology, the digital FIR filter may be implemented by a DDC module of an FPGA, or by an FIR filter inside a Transceiver chip, and may be selected and used according to actual conditions.

As shown in fig. 2, the problem of direct current at the center frequency point of the zero intermediate frequency Transceiver chip is that the zero intermediate frequency technology is to directly move the radio frequency signal to zero frequency for IQ ADC sampling, the local oscillation frequency point of the Transceiver chip is set as the center frequency point of the baseband signal, the trapezoid frame with dotted line is the FIR filter of the Transceiver chip, and the bandwidth of the FIR filter of the chip is equal to the bandwidth of the radio frequency signal. At this time, the central frequency point is within the bandwidth range of the baseband signal, and the central direct current signal affects the EVM for receiving the modulation signal or the individual RB block in the modulation signal, so that the reception noise of the RB block is raised.

In this embodiment, first, the AU device analyzes according to the bandwidth of an actually input useful signal, configures the bandwidth of an FIR filter in a Transceiver chip, and configures the bandwidth of an FIR filter in a DDC module of the FPGA, where the FIR filter in the FPGA forms the FIR filter for the final signal. And then correcting the local oscillation frequency point of the local oscillation signal according to the central frequency point and the bandwidth of the radio frequency signal to obtain a corrected local oscillation frequency point, and sampling the radio frequency signal by using the corrected local oscillation frequency point to form a baseband signal. The local oscillation frequency point is corrected, namely, the local oscillation frequency point of the local oscillation signal is subjected to frequency offset processing, so that after the local oscillation frequency point is corrected to sample the radio frequency signal, the central direct current signal deviates out of the bandwidth range of the formed baseband signal. The base station uplink background can not count the central direct current signal, thereby solving the problem that the central direct current signal affects the bottom noise in the baseband signal bandwidth.

In an embodiment, the obtaining a modified local oscillation frequency point according to the bandwidth and the central frequency point of the radio frequency signal includes steps 310 to 330, where:

step 310, configuring the bandwidth of the FIR filter; and comparing the relationship between the bandwidth of the radio frequency signal and a preset bandwidth.

The configurable bandwidth of the digital FIR filter of the AD936x chip RX at the RU end is 56M at most, the radio frequency input of a Transceiver chip is broadband input, and the highest input frequency is 6 GHz. Although the Transceiver chip allows a large bandwidth to be input, the bandwidth of the digital FIR filter determines the maximum bandwidth of the digital signal output by the Transceiver chip, namely the bandwidth of the maximum radio frequency signal allowed to be input by the Transceiver chip is a radio frequency signal with a local oscillation frequency point as the center and the bandwidth of 56M.

Step 320, if the bandwidth of the radio frequency signal is less than or equal to the preset bandwidth, calculating a corrected frequency offset value A (B/2) and (C-B)/2, wherein B is the bandwidth of the radio frequency signal, and C is the bandwidth of the FIR filter; and calculating and correcting the local oscillation frequency point according to the frequency offset value A and the central frequency point of the radio frequency signal.

The preset bandwidth may be set to 20M, 25M. The specific value of the preset bandwidth may be set according to actual situations, and this embodiment is not limited. The present application takes the preset bandwidth as 20M as an example for explanation.

It should be noted that the preset bandwidth is set to distinguish whether the radio frequency signal is a single noise signal or consists of a plurality of carrier signals according to the bandwidth of the radio frequency signal. If the bandwidth of the radio frequency signal is greater than the preset bandwidth, the radio frequency signal is composed of a plurality of carrier signals; if the bandwidth of the radio frequency signal is less than or equal to the preset bandwidth, the radio frequency signal is composed of a single carrier signal. The radio frequency signal composed of a single carrier signal and the radio frequency signal composed of a plurality of carrier signals have different calculation modes of frequency offset. This embodiment is to explain how to perform frequency offset processing on a radio frequency signal composed of a single carrier signal.

As shown in fig. 4, assuming that the center frequency point of the uplink rf signal is f0, the signal bandwidth is B, B is smaller than the preset bandwidth, the maximum FIR filter bandwidth of the Transceiver chip is C, and the frequency offset value is a, in order to offset the center dc signal out of the bandwidth range of the baseband signal obtained after sampling, the range of a is set to (B/2) or less and (C-B)/2. For a CDMA signal bandwidth of 11M, which is at least 5M in frequency, for a 20M FDD-LTE signal, which is at least 10M in frequency, and for a 25M FDD-LTE signal, which is at least 12.5M in frequency, the center dc signal can be shifted out of the bandwidth range of the baseband signal. Specifically, for a bandwidth A >5.5M for 11M signals, A ≦ 22.5M; for a bandwidth A >10M for a 20M signal, A ≦ 18M; for a bandwidth A >12.5M for a 25M signal, A ≦ 15.5M. Then the local oscillation frequency point of the corrected Transceiver chip RX becomes f 0+ -A. And the ARM chip of the RU equipment sets a correction local oscillation frequency point f0 +/-A of the Transceiver chip. As can be seen from fig. 3, the local oscillation frequency points of the local oscillation signals are corrected and then the radio frequency signals are sampled to form baseband signals, the central direct current signal deviates from the bandwidth range of the baseband signals, when the macro station background counts the uplink bottom noise, only the in-band bottom noise of the baseband signals is counted, and the central direct current signal does not affect the uplink reception bottom noise.

And 330, if the bandwidth of the radio frequency signal is greater than the preset bandwidth, calculating a corrected local oscillation frequency point according to the bandwidth and the central frequency point of each carrier signal forming the radio frequency signal, wherein the corrected local oscillation frequency point is positioned in a transition band among a plurality of carrier signals.

The bandwidth of the radio frequency signal is greater than the preset bandwidth, which indicates that the radio frequency signal is composed of a plurality of carrier signals.

In one embodiment, calculating the modified local oscillation frequency point according to the bandwidth and the center frequency point of each carrier signal constituting the radio frequency signal includes:

and calculating a correction local oscillation frequency point according to the bandwidth, the central frequency point and the first transition band of each carrier signal.

Specifically, if the bandwidth of the radio frequency signal is greater than 20M, for example, the mobile TD-LTE E frequency band signal is 40M bandwidth or 50M bandwidth, the mobile TD-LTE F frequency band signal is 30M bandwidth, or the connected FDD-LTE signal is 30M bandwidth, and the connected telecommunication contention FDD-LTE signal is 45M bandwidth. The 40M bandwidth TD-LTE signal consists of 2 20M TD-LTE carrier signals; the 30M bandwidth TD-LTE or FDD-LTE signal is composed of 1 20M LTE carrier signal and 1 10M LTE carrier signal; the 45M bandwidth FDD-LTE signal consists of 2 20M LTE carrier signals and 15M LTE carrier signal; the 50M bandwidth FDD-LTE signal is composed of 2 20M LTE carrier signals and 1 10M LTE carrier signal. The maximum allowable output bandwidth of an FIR filter of the Transceiver chip is 56M, and for RF signals with the bandwidth of more than or equal to 30M, the central direct current signal cannot be directly deviated from the bandwidth range of a baseband signal. Because the BBU background only counts the background noise in the useful RB block band in the baseband signal bandwidth, the background noise of the transition band is not counted. And no RB block exists in the signal transition zone, and no information is transmitted. Therefore, only the central direct current signal needs to be ensured to be in the transition zone.

The FPGA chip of the AU equipment transmits information of radio frequency signals to the FPGA on the RU equipment through optical fibers, an ARM chip of the RU equipment reads the information of the FPGA on the RU, the ARM chip calculates transition zones of the radio frequency signals, and local oscillation frequency points of a Transceiver chip are set to be in the transition zones of two 20M TD-LTE carrier signals or the central frequency points are in the transition zones of 1 20M LTE carrier signal and 1 10M LTE carrier signal. The specific calculation process is as follows: the FPGA of the AU device analyzes the radio frequency signal input by the AU device, and determines central frequency points of 2 20M carrier signals within a 40M useful signal bandwidth, or central frequency points of 1 10M carrier signal and 1 20M carrier signal within a 30M useful signal bandwidth, where the central frequency points are set as f1 and f2, the useful RB block bandwidth of the 20M LTE carrier signal is (100+1) × 18 ═ 18.18MHz, the total bandwidth of the transition band (first transition band) is 20-18.18 ═ 1.82M, that is, the transition band of a single 20M carrier signal is ± 0.91M. The 2 TD-LTE carrier signals are combined into a 40M bandwidth signal, the bandwidth of a transition band between the two 20M carrier bandwidth signals is 2 x (20-18.18)/2 x 1.82M, namely the ARM correction local oscillation frequency point is ((f1+10-0.91) + (f2-10+ 0.91))/2.

As shown in fig. 5, a radio frequency signal with a bandwidth of 30M is composed of 1 carrier with a bandwidth of 20M and one carrier with a bandwidth of 10M. The total transition band of a single 10M carrier bandwidth signal is (20-18.18)/2 ═ 0.91, that is, the transition band of a single 10M carrier signal is ± 0.455M, the transition band bandwidths of 1 20M and 1 10M carrier signals are (20-18.18)/2+ (20-18.18)/2/2 ═ 1.365M, and the ARM modified local oscillation frequency point is ((f1+10-0.91) + (f2-5+0.455))/2 or ((f1-10+0.91) + (f2+ 5-0.455))/2. After the local oscillation frequency point is corrected, the radio frequency signal with the bandwidth of 30M is sampled and then moved to a baseband to form a baseband signal effective bandwidth range, and a central direct current signal does not exist, so that the influence of the central direct current signal on the bottom noise is avoided.

In order to more clearly describe the calculation method of correcting the local oscillation frequency point, a radio frequency signal with a bandwidth of 45M and a radio frequency signal with a bandwidth of 45M are taken as examples for description.

The 45M bandwidth signal is composed of 15M carrier signal and 2 20M carrier signals, and the sequence from the low frequency point to the high frequency point on the frequency spectrum may be 5M +20M, 20M +5M +20M, 20M +5M, and 3 combinations thereof. When how to calculate the modified local oscillation frequency point of the 45M bandwidth signal is analyzed, 15M carrier signal and 1 20M carrier signal need to be regarded as a whole, that is, the 45M signal can be regarded as 1 25M carrier signal and 1 20M carrier signal to be combined. Let the central frequency points of 2 20M carrier signals be f1 and f2, respectively, and the central frequency point of a 5M carrier signal be f 3. The total transition band of the 5M LTE carrier signal is (20-18.18)/2/2 ═ 0.455, i.e., the transition band of a single 5M carrier signal is ± 0.2275M. The center frequency points of the 25M carrier signals, which are the combination of the 1 20M carrier bandwidth signal and the 15M carrier bandwidth signal, are (f1-10+ f3+2.5)/2 and (f3-2.5+ f1+10)/2, or (f2-10+ f3+2.5)/2 and (f3-2.5+ f2+ 10)/2. The corrected local oscillation frequency point of the 45M bandwidth signal is as follows:

TABLE 1

Similarly, the bandwidth of the 50M rf signal is composed of 2 20M carrier signals and 1 10M carrier signal, and the sequence from the low frequency point to the high frequency point on the frequency spectrum may be 3 combinations of 10M +20M, 20M +10M +20M, and 20M + 10M. Then 1 10M carrier signal and 1 20M carrier signal are combined into one 30M signal, so that the corrected local oscillation frequency point is calculated by using 1 30M carrier signal and 1 20M carrier signal. Let the central frequency points of 2 20M carrier signals be f1 and f2, respectively, and the central frequency point of a 10M carrier signal be f 3. The center frequency points of the 30M carrier signals formed by combining 1 20M carrier signal and 1 10M carrier signal are (f1-10+ f3+5)/2 and (f3-5+ f1+10)/2, or (f2-10+ f3+5)/2 and (f3-5+ f2+ 10)/2. The modified local oscillation frequency points of the 50M bandwidth signals are as follows in table 2:

TABLE 2

In this embodiment, a TD-LTE F band is taken as an example for explanation, a center channel number of a radio frequency signal is 38450, that is, a center frequency point of a signal with a 30M bandwidth is 1900 MHz. The radio frequency signal bandwidth is 30M, and the TD-LTE signal of 30M bandwidth is composed of 1 20M carrier signal and 1 10M carrier signal of 1885-1905 MHz and 1905-1915 MHz. The traditional method is to set the local oscillation frequency point of a Transceiver chip equal to 1900MHz of a central channel number, configure a digital FIR filter of a chip RX to be 30M, and then the local oscillation direct current signal 1900MHz is in a useful signal 20M carrier wave.

According to the method provided by the embodiment of the application, the ARM chip at the RU end is provided with the digital FIR filter of the chip RX as 56M, and the local oscillation frequency point is corrected according to the signal center channel number and the signal bandwidth provided by the FPGA. The TD-LTE signal with 20M bandwidth is composed of 100 NB, the bandwidth of one NB is 18kHz, and the bandwidth of a transition band between two signals with 20M bandwidth is 1.82 MHz. The transition band of 1 20M carrier signal and 1 10M carrier signal of 30M TD-LTE broadband signal is 1904.09 MHz-1905.455 MHz, and the ARM modified local oscillator frequency point is (1904.09MHz + 1905.455)/2-1904.7725 MHz. As shown in fig. 5, the central dc signal is in the transition band of the 10M and 20M carrier signals, the uplink baseband detection of the macro station does not detect the noise floor in the transition band, and the dc signal does not affect the noise floor of the useful RB block in the transition band.

In one embodiment, the method for reducing the reception noise floor further comprises: and synchronously carrying out frequency offset processing on the central direct current signal and the baseband signal so as to enable the central frequency point of the baseband signal to fall at zero frequency.

After the radio frequency signal is sampled to the baseband, the center frequency point of the formed baseband signal is not at zero frequency, and a large frequency offset is generated, thereby causing the problems in two aspects. On one hand, the FPGA of the RU device has to process the baseband signal with the bandwidth of 56M, which increases the processing resource and the optical fiber bandwidth of the FPGA; on the other hand, the baseband signal is transmitted to the AU device to be subjected to digital-to-analog conversion and converted into the radio frequency signal, but since the central frequency point of the baseband signal is not at zero frequency, the central frequency point of the radio frequency signal can have an offset with a frequency offset value a after the frequency conversion is performed on the radio frequency signal at the AU end.

In this embodiment, the center direct current signal and the baseband signal are synchronously subjected to frequency offset processing, so that the center frequency point of the baseband signal falls at zero frequency. In one embodiment, synchronizing the center dc signal with the baseband signal for frequency offset processing includes:

Specifically, an NCO is integrated in a DDC module in the FPGA, the frequency offset of the NCO is set as-A according to the frequency offset value A obtained by the method, the NCO shifts the central direct current signal and the baseband signal again, namely, the central frequency point of the baseband signal is shifted to zero frequency, and the baseband signal with useful bandwidth is filtered. The designed bandwidth of an FIR filter in a DDC module of the FPGA can be equal to the bandwidth of a radio-frequency signal, so that the bandwidth of a signal actually processed by the FPGA is the same as the bandwidth of the radio-frequency signal, and the radio-frequency signal output by an AU end does not have frequency deviation.

If the bandwidth of the radio frequency signal is smaller than the preset bandwidth, for example, the bandwidth is 20M, an ARM chip in the RU device configures a Transceiver chip into a 56M bandwidth, and the ARM chip corrects the local oscillation frequency point according to the central frequency point and the bandwidth of the radio frequency signal, and deviates the central direct current signal out of the bandwidth range of the baseband signal. As shown in fig. 6, the NCO in the DDC module of the FPGA carries out synchronous frequency shifting on the baseband signal and the central dc signal, and when the modified local oscillation frequency point is f0 ± a, the NCO is set to be the frequency offset of-a. The trapezoid frame of the virtual dot line is an FIR filter in a DDC module of the FPGA, the bandwidth is configured to be 20M bandwidth, the straight line of the dot line is a central direct current signal, the central direct current signal deviates from the bandwidth range of the baseband signal at the moment, and the central frequency point of the baseband signal is positioned at zero frequency.

And if the bandwidth of the radio frequency signal is greater than or equal to the preset bandwidth, the corrected local oscillation frequency point is LOx, and the central frequency point of the radio frequency signal is f 0. If the radio frequency signal is directly output at the AU end in a frequency conversion mode, the center frequency point of the output signal is LOx MHz, and the center frequency point of the radio frequency signal which needs to be output actually is f 0. Therefore, the frequency offset value of the input signal of the RU equipment and the output signal of the AU equipment of the uplink radio frequency channel of the DAS system is | f0-LOx |. The DDC module in the FPGA of the RU end needs to move the central frequency point of the baseband signal to zero frequency again, so that the frequency conversion is carried out at the AU end to output the radio frequency signal, and the central frequency point deviation of a useful radio frequency band signal can not occur. At this time, the transport frequency NCO is set to- (f0-Lox) inside the FPGA. Meanwhile, the bandwidth of the FIR filter in the DDC module of the FPGA is equal to the bandwidth of the radio frequency signal, so that the FPGA does not process 56M bandwidth signals.

According to the above description of fig. 5, although the center dc signal is in the transition band of 10M and 20M carrier signals after the shift, since the 1904.7725MHz local oscillation frequency point is not the center frequency point of the TD-LTE F band signal with 30M bandwidth, if the signal is directly output at the AU end, the center frequency point of the output signal is 1904.7725MHz, and the center frequency point of the RF signal to be output is 1900 MHz. Therefore, the frequency offset between the RU input signal and the AU output signal of the uplink radio frequency channel of the DAS system is 1904.7725-1900-4.7725M. As shown in fig. 7, the DDC module inside the FPGA at the RU end needs to move the center frequency point of the 30M baseband signal to zero frequency again, so that the frequency conversion is performed at the AU end to output an RF signal, and frequency point offset of a useful RF broadband signal does not occur. At this time, the FPGA is set to-4.7725M as the carry frequency NCO, the dotted line trapezoid frame in fig. 7 is the FIR filter in the DDC module of the FPGA, and the bandwidth is 30M.

It should be noted that, the DAS, the repeater, and the AU end are both connected to the RRU through a radio frequency feeder and a coupler. Once the DAS and the RRU are connected and installed, the signal format of the radio frequency channel is fixed. In practical use, the signal bandwidth configuration of the existing network is flexible. Such as TD-LTE E-band signals, which move to provide a maximum used RF bandwidth of 50M. The RRU equipment only starts one 20M carrier bandwidth, and the central channel number configured by the RRU is a central frequency point of a 20M optional signal in a 50M band. However, with the cell coverage expansion, the RRU device starts 2 20M carriers to form a 40M bandwidth signal, and the center channel number is a 50M in-band optional 40M signal center frequency point. The method can flexibly judge the actual RU end uplink central frequency point and the RF signal bandwidth according to the AU end downlink input RF signal, and reconfigure the local oscillation frequency point, so that the local oscillation direct current signal can not influence the uplink RB block bottom noise. Meanwhile, no matter the capacity expansion of the signal bandwidth or the replacement of the RRU radio frequency system channel is carried out, the modification is one-time, and once the installation and debugging are completed, the channel number and the signal bandwidth can be fixed according to the communication system. Thus, the situation that the DAS system repeatedly configures the RU Transceiver chip can not occur.

It should be understood that although the steps in the flowcharts of fig. 1 and 3 are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not performed in the exact order shown and described, and may be performed in other orders, unless explicitly stated otherwise. Moreover, at least some of the steps in fig. 1 and 3 may include multiple sub-steps or multiple stages that are not necessarily performed at the same time, but may be performed at different times, and the order of performing the sub-steps or stages is not necessarily sequential, but may be performed alternately or alternately with other steps or at least some of the sub-steps or stages of other steps.

In one embodiment, as shown in fig. 8, there is provided an apparatus for reducing a reception noise floor, including: a first acquisition module 810, a second acquisition module 820, and a sampling module 830, wherein:

a first obtaining module 810, configured to receive a radio frequency signal, and obtain a bandwidth and a center frequency point of the radio frequency signal;

a second obtaining module 820, configured to obtain a modified local oscillation frequency point according to the bandwidth and the central frequency point of the radio frequency signal;

the sampling module 830 is configured to sample the radio frequency signal according to the corrected local frequency point to form a baseband signal, so that the central dc signal deviates from the bandwidth of the baseband signal.

In an embodiment, the apparatus for reducing the receive noise floor further includes an offset module, configured to perform frequency offset processing on the central direct current signal and the baseband signal synchronously, so that a central frequency point of the baseband signal falls at a zero frequency.

In an embodiment, the offset module is configured to calculate a frequency offset according to the corrected local oscillation frequency point and a center frequency point of the radio frequency signal;

In an embodiment, the obtaining, by the second obtaining module 820, the modified local oscillation frequency point according to the bandwidth and the central frequency point of the radio frequency signal includes:

In one embodiment, comparing the relationship between the bandwidth of the radio frequency signal and the preset bandwidth includes:

if the bandwidth of the radio frequency signal is less than the preset bandwidth, calculating a frequency offset value A (B/2) is more than or equal to A and less than or equal to (C-B)/2 according to the bandwidth of the radio frequency signal and the center frequency point, wherein B is the bandwidth of the radio frequency signal, and C is the bandwidth of an FIR filter; calculating and correcting a local oscillation frequency point according to the frequency offset value A and the central frequency point of the radio frequency signal;

if the bandwidth of the radio frequency signal is larger than the preset bandwidth, calculating a corrected local oscillation frequency point according to the bandwidth and the central frequency point of each carrier signal forming the radio frequency signal, wherein the corrected local oscillation frequency point is positioned in a transition zone among the plurality of carrier signals.

In an embodiment, the calculating, by the second obtaining module 820, the modified local oscillation frequency point according to the bandwidth and the central frequency point of each carrier signal constituting the radio frequency signal includes:

For specific definition of the means for reducing the received noise floor, reference may be made to the above definition of the method for reducing the received noise floor, and details thereof are not repeated here. The modules in the device for reducing the receiving bottom noise can be wholly or partially realized by software, hardware and a combination thereof. The modules can be embedded in a hardware form or independent from a processor in the computer device, and can also be stored in a memory in the computer device in a software form, so that the processor can call and execute operations corresponding to the modules.

In one embodiment, a computer device is provided, which may be a terminal, and its internal structure diagram may be as shown in fig. 9. The computer device includes a processor, a memory, a network interface, a display screen, and an input device connected by a system bus. Wherein the processor of the computer device is configured to provide computing and control capabilities. The memory of the computer device comprises a nonvolatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of an operating system and computer programs in the non-volatile storage medium. The network interface of the computer device is used for communicating with an external terminal through a network connection. The computer program is executed by a processor to implement a method of reducing receive noise floor. The display screen of the computer equipment can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer equipment can be a touch layer covered on the display screen, a key, a track ball or a touch pad arranged on the shell of the computer equipment, an external keyboard, a touch pad or a mouse and the like.

Those skilled in the art will appreciate that the architecture shown in fig. 9 is merely a block diagram of some of the structures associated with the disclosed aspects and is not intended to limit the computing devices to which the disclosed aspects apply, as particular computing devices may include more or less components than those shown, or may combine certain components, or have a different arrangement of components.

In one embodiment, a computer device is provided, comprising a memory and a processor, the memory having a computer program stored therein, the processor implementing the following steps when executing the computer program:

and sampling the radio frequency signal according to the corrected vibration frequency point to form a baseband signal so as to enable the central direct current signal to deviate from the bandwidth range of the baseband signal.

In one embodiment, a computer-readable storage medium is provided, having a computer program stored thereon, which when executed by a processor, performs the steps of:

It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by hardware instructions of a computer program, which can be stored in a non-volatile computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. Any reference to memory, storage, database, or other medium used in the embodiments provided herein may include non-volatile and/or volatile memory, among others. Non-volatile memory can include read-only memory (ROM), Programmable ROM (PROM), Electrically Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), or flash memory. Volatile memory can include Random Access Memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms such as Static RAM (SRAM), Dynamic RAM (DRAM), Synchronous DRAM (SDRAM), Double Data Rate SDRAM (DDRSDRAM), Enhanced SDRAM (ESDRAM), Synchronous Link DRAM (SLDRAM), Rambus Direct RAM (RDRAM), direct bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. A method for reducing receive noise floor, the method comprising:

acquiring a corrected local oscillation frequency point according to the bandwidth and the central frequency point of the radio frequency signal; the obtaining of the modified local oscillation frequency point according to the bandwidth and the central frequency point of the radio frequency signal comprises: configuring the bandwidth of the FIR filter; and comparing a relationship between the bandwidth of the radio frequency signal and a preset bandwidth, wherein the comparing the relationship between the bandwidth of the radio frequency signal and the preset bandwidth comprises: if the bandwidth of the radio frequency signal is smaller than the preset bandwidth, calculating a frequency deviation value A (B/2) is larger than or equal to A and smaller than or equal to (C-B)/2 according to the bandwidth of the radio frequency signal and the center frequency point, wherein B is the bandwidth of the radio frequency signal, and C is the bandwidth of an FIR filter; calculating the corrected local oscillation frequency point according to the frequency offset value A and the central frequency point of the radio frequency signal; if the bandwidth of the radio frequency signal is larger than the preset bandwidth, calculating a corrected local oscillation frequency point according to the bandwidth and the central frequency point of each carrier signal forming the radio frequency signal, wherein the corrected local oscillation frequency point is positioned in a transition band among a plurality of carrier signals;

2. The method of claim 1, further comprising:

3. The method of claim 2, wherein the synchronizing the center dc signal with the baseband signal comprises:

4. The method of claim 1, wherein when the bandwidth of the radio frequency signal is greater than a preset bandwidth, the calculating a modified local oscillation frequency point according to the bandwidth and the center frequency point of each carrier signal constituting the radio frequency signal comprises:

5. The method of claim 4, wherein the bandwidth of the FIR filter is equal to the bandwidth of the radio frequency signal.

6. An apparatus for reducing receive noise floor, the apparatus comprising:

the second acquisition module is used for acquiring a corrected local oscillation frequency point according to the bandwidth and the central frequency point of the radio frequency signal; the obtaining of the modified local oscillation frequency point according to the bandwidth and the central frequency point of the radio frequency signal comprises: configuring the bandwidth of the FIR filter; and comparing a relationship between the bandwidth of the radio frequency signal and a preset bandwidth, wherein the comparing the relationship between the bandwidth of the radio frequency signal and the preset bandwidth comprises: if the bandwidth of the radio frequency signal is smaller than the preset bandwidth, calculating a frequency deviation value A (B/2) is larger than or equal to A and smaller than or equal to (C-B)/2 according to the bandwidth of the radio frequency signal and the center frequency point, wherein B is the bandwidth of the radio frequency signal, and C is the bandwidth of an FIR filter; calculating the corrected local oscillation frequency point according to the frequency offset value A and the central frequency point of the radio frequency signal; if the bandwidth of the radio frequency signal is larger than the preset bandwidth, calculating a corrected local oscillation frequency point according to the bandwidth and the central frequency point of each carrier signal forming the radio frequency signal, wherein the corrected local oscillation frequency point is positioned in a transition band among a plurality of carrier signals;

7. A computer device comprising a memory and a processor, the memory storing a computer program, wherein the processor implements the steps of the method of any one of claims 1 to 5 when executing the computer program.

8. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the steps of the method of any one of claims 1 to 5.