WO2019127859A1 - 一种支持全频段的分布式天线系统远端单元及实现方法 - Google Patents

一种支持全频段的分布式天线系统远端单元及实现方法 Download PDF

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WO2019127859A1
WO2019127859A1 PCT/CN2018/075964 CN2018075964W WO2019127859A1 WO 2019127859 A1 WO2019127859 A1 WO 2019127859A1 CN 2018075964 W CN2018075964 W CN 2018075964W WO 2019127859 A1 WO2019127859 A1 WO 2019127859A1
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programmable
link
power
radio frequency
monitoring channel
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PCT/CN2018/075964
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English (en)
French (fr)
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陈青松
李鑫
余官定
褚如龙
毛建洋
胡晓飞
罗宝填
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三维通信股份有限公司
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Publication of WO2019127859A1 publication Critical patent/WO2019127859A1/zh

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/022—Site diversity; Macro-diversity
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0426—Power distribution
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/52—TPC using AGC [Automatic Gain Control] circuits or amplifiers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/08—Access point devices
    • H04W88/10—Access point devices adapted for operation in multiple networks, e.g. multi-mode access points

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  • the present invention relates to the field of wireless communication technologies, and in particular, to a remote unit of a distributed antenna system supporting a full frequency band and an implementation method thereof.
  • distributed antenna system systems are mainly used to solve indoor signal coverage problems of large buildings, such as (shopping malls, stadiums, large office buildings, etc.). As indoor traffic increases, distributed antenna system systems need to be continuously upgraded and expanded to meet new demands. At the same time, 5G is about to be commercialized, and existing distributed antenna system systems need to be re-engineered to support 5G frequency bands. .
  • the existing remote antenna unit of the distributed antenna system is a system based on frequency customization. As shown in FIG. 1 , the existing distributed antenna system has a fixed frequency filter and a duplexer in the transceiver link, and can only support specific ones. Frequency Range. In the process of system upgrade or expansion, if you need to support different frequency bands or add new frequency bands, you can only do so by replacing the devices. For example, the indoor coverage of 5G mobile communication generally adopts the 3.5GHz frequency band, while the existing 2G/3G/4G is concentrated in the 700M to 2700MHz frequency band. To upgrade to support 5G, the hardware system must be replaced, which results in repeated investment of equipment and replacement of hardware. A lot of labor costs are required, and the overall cost of the system is high.
  • the distributed antenna system equipment is to support all RF bands, there should be no RF components such as RF filters and duplexers on the RF transceiver link and all devices on the link should support the full frequency range.
  • existing chip manufacturers have introduced RF devices supporting the full frequency range of 0 to 6 GHz. It is theoretically feasible to design a distributed antenna system system with a full frequency range. However, since there is no RF filter on the transceiver link, the interference problem of the transmission channel to the receiving channel cannot be ignored, and in severe cases, the system may be paralyzed.
  • the interference of the transmitting channel to the receiving channel comes from two aspects: on the one hand, the transmitting signal is received by the receiving antenna, causing the device of the receiving link to be saturated, causing severe nonlinearity; on the other hand, the signals generated by the transmitting link power amplifier are mutually The component is modulated, which may fall within the uplink frequency range and affect the quality of the uplink signal. Under normal circumstances, the spatial isolation of the transmitting and receiving antennas ensures that the downlink signal does not interfere with the uplink. However, due to changes in the electromagnetic environment near the device or the antenna, such as the addition of metal baffles in the space, the isolation of the transmitting and receiving antennas may change, which may result in System performance has deteriorated and may not even work.
  • a remote unit for a distributed antenna system supporting a full frequency band mainly includes: programmable Logic processing unit FPGA, programmable RF transmit link, programmable RF receive link, and transmit and receive antennas.
  • the function of the programmable logic processing unit FPGA is (1) for implementing communication with a distributed antenna system near-end machine, receiving a downlink signal and transmitting an uplink signal to the near-end machine; (2) for receiving the slave Digital signals from the near-end of the distributed antenna system, digital filtering and digital up-conversion and digital pre-distortion DPD, quadrature modulator correction QMC, etc., sent to the programmable RF transmit link; (3) Receiving digital signals from the programmable radio frequency receiving link, performing digital down conversion and digital filtering, and transmitting to a distributed antenna system near-end machine; (4) for implementing with a programmable radio frequency link The monitoring of the isolation of the transmitting and receiving antennas and the adaptive adjustment of the distributed antenna system.
  • the programmable RF transmission link mainly includes a digital to analog converter, a programmable local oscillator generator, a quadrature modulator, a variable gain amplifier, a high power amplifier, and a monitoring channel a.
  • the programmable radio frequency transmitting link is configured to receive a digital signal of the programmable logic processing unit FPGA, and perform analog-to-digital conversion to obtain an analog signal S1.
  • the signal S1 is modulated to be required to be transmitted.
  • the RF frequency is amplified by a variable gain amplifier and a high power gain amplifier.
  • the variable gain amplifier is used for output power regulation and automatic adjustment of the system when the isolation of the transceiver antenna changes.
  • the monitoring channel a of the programmable radio frequency transmitting link mainly includes a radio frequency coupler, a down mixer and an analog to digital converter, and is used by the programmable logic processing unit FPGA to acquire signal intermodulation of the programmable radio frequency transmitting link.
  • the programmable RF receiving link mainly includes an adjustable attenuator, a low noise amplifier, a programmable local oscillator generator, a quadrature demodulator, a programmable low pass filter, a variable gain amplifier, and an analog to digital converter. And monitor channel b.
  • the programmable radio frequency receiving link is configured to receive an uplink signal from the antenna, and after being amplified, demodulate the specific radio frequency to a baseband according to a software configuration of the local oscillator signal, and then perform low-pass filtering and analog-to-digital conversion. After sampling, it is sent to the programmable logic processing unit FPGA.
  • Adjustable attenuators and variable gain amplifiers in the programmable RF receive link are used to adjust link gain distribution as system isolation changes.
  • the monitoring channel b of the receiving link mainly includes a radio frequency coupler, a local oscillator generator, a down mixer, a programmable low pass filter, and a power detecting circuit, and is configured to measure the transmitted signal to reach the programmable radio frequency receiving chain.
  • the power of the road is calculated to determine the isolation between the transceiver antennas.
  • the invention also provides a method for implementing a remote unit of a distributed antenna system supporting a full frequency band, by which the monitoring and adaptive adjustment of the isolation of the transceiver antenna can be realized.
  • the method for calculating the isolation between the transceiver antennas includes:
  • the adaptive adjustment method of the distributed antenna system includes:
  • the power P in detected by the monitoring channel b is greater than the maximum input power threshold P thd that the programmable RF receiving link can withstand, by adjusting the value of the adjustable attenuator in the programmable RF receiving link, The power of the LNA entering the programmable radio frequency receive link does not exceed Pthd .
  • the gain of the programmable RF receive link is maintained constant by increasing the gain of the variable gain amplifier in the programmable RF receive link.
  • the isolation of the transceiver antenna becomes larger, and if the power P in detected by the monitoring channel b is smaller than the maximum input power threshold P thd that the programmable RF receiving link can withstand, the automatic adjustment is adjustable.
  • the values of the attenuator and the variable gain amplifier are used to improve the noise figure of the programmable RF receive link.
  • the method for adaptively adjusting the distributed antenna system further includes:
  • the isolation of the transceiver antenna increases, P inband ⁇ P' thd , by increasing the gain of the variable gain amplifier of the programmable RF transmission link to ensure the strength of the transmitted signal.
  • the invention has the beneficial effects that all the 2G/3G/4G frequency bands can be supported only by software configuration without the need to replace the hardware system, and the smooth upgrade to the 5G is supported, and the use is convenient, and the overall system cost is higher than the existing products. Greatly reduced.
  • FIG. 1 is a schematic diagram of a remote unit of a conventional distributed antenna system
  • FIG. 2 is a schematic diagram of a remote unit of a distributed antenna system of the present invention.
  • FIG. 3 is a flow chart of an adaptive adjustment method 1 of a distributed antenna system of the present invention.
  • FIG. 4 is a flow chart of an adaptive adjustment method 2 of the distributed antenna system of the present invention.
  • the remote unit of the conventional distributed antenna system generally includes a frequency-customized device such as a radio frequency filter and a duplexer, and cannot support a full-band application.
  • the programmable RF transmission link mainly includes a digital-to-analog converter, a local oscillator generator, a quadrature modulator, a variable gain amplifier, and a high power.
  • the gain amplifier and the monitoring channel a realize the transmission function of the downlink signal.
  • the radio frequency modulation adopts a zero-IF modulation scheme to avoid the out-of-band spurs caused by the mirror image and the local oscillator leakage.
  • the programmable logic processing unit FPGA can correct the quadrature modulator by correcting the QMC algorithm with a real-time quadrature modulator.
  • the quadrature modulator correction QMC algorithm is an industry-wide algorithm and will not be described here.
  • variable gain amplifier in the programmable RF transmit link can be used to dynamically adjust the output power and can be used to adaptively adjust the system gain as the transmit and receive antenna isolation changes, as described below.
  • the monitoring channel a is coupled with the RF signal from the high power gain amplifier. After down-conversion, it is sampled by the analog-to-digital converter, and the sampled digital signal is sent to the programmable logic processing unit.
  • the monitoring channel a has three functions: one is to observe the QMC observation channel as a digital predistortion DPD and a quadrature modulator, the other is to obtain the output power of the high power gain amplifier, and the third is to extract the intermodulation component of the transmitted signal for Measure whether the intermodulation will interfere with the upstream signal.
  • the programmable RF receiving link mainly includes an adjustable attenuator, a low noise amplifier, a local oscillator generator, a quadrature demodulator, a programmable low pass filter, a variable gain amplifier, and the like.
  • the analog-to-digital converter and the monitoring channel b realize the receiving function of the radio frequency signal.
  • the adjustable attenuator and the variable gain amplifier can dynamically adjust the gain distribution of the link for adaptive adjustment of the system gain when the transceiver antenna isolation changes, as described below.
  • the monitoring channel b is coupled from the low noise amplifier, and after downconversion, the programmable frequency filter filters out the unwanted frequency components and then enters the power detection circuit.
  • the detected power value is sent to the programmable logic processing unit FPGA for calculating the isolation of the system transceiver antenna.
  • the programmable logic processing unit FPGA is mainly used to realize communication and digital signal processing functions with the distributed antenna system near-end machine, including digital filtering, digital up-conversion, digital down-conversion, digital pre-distortion DPD, The quadrature modulator corrects the QMC and the like.
  • the programmable logic processing unit FPGA is used to monitor the isolation between the transmitting and receiving antennas, and adaptively adjust the gain of the system according to the change of the isolation, so that it can work stably.
  • the interference of the programmable RF transmit link to the programmable RF receive link mainly comes from two aspects. Among them, the transmitted signal is directly received by the receiving antenna, and if the isolation is too poor, it may cause saturation of the programmable RF receiving link.
  • the isolation between the transceiver antennas is calculated as follows:
  • the bandwidth of the local oscillator and programmable low-pass filter of monitoring channel b so that the spectrum of the transmitted signal is in the passband of the low-pass filter.
  • the output power P r of the detector is the received transmit power.
  • the gain of the receiving antenna port to the monitoring channel b detector is G r
  • the interference of the programmable RF transmit link to the programmable RF receive link mainly comes from two aspects. Among them, the transmitted signal is directly received by the receiving antenna, and if the isolation is too poor, it may cause saturation of the programmable RF receiving link.
  • the adaptive adjustment method for this situation is as follows:
  • the power P in detected by the monitoring channel b is greater than the maximum input power threshold P thd that the receiver can withstand, then adjust the value of the adjustable attenuator before the low noise amplifier so that the power entering the low noise amplifier does not exceed P thd .
  • the interference signal is filtered by the low-pass filter, so the gain of the variable gain amplifier after the filter can be increased to maintain the gain of the entire receiver.
  • P in ⁇ P thd the values of the adjustable attenuator and the variable gain amplifier are automatically adjusted to improve the noise figure of the receiver. The adjustment process is shown in Figure 3.
  • the signal intermodulation component due to the nonlinearity of the programmable RF transmit link device may cause interference to the uplink signal.
  • 3GPP Band3 has a downlink frequency range of 1805 MHz to 1880 MHz and an upstream frequency range of 1710 MHz to 1785 MHz. Since the uplink and downlink frequency intervals are small, the intermodulation component of the downlink signal is just in the uplink frequency band. If the transmission and reception isolation of the antenna is relatively small, the uplink signal may be blocked.
  • the adjustment method for this situation is as follows:
  • the isolation G of the transmitting and receiving antenna is calculated according to the method described above.
  • the maximum threshold allowed for the interference signal defined by the programmable RF receive link is P′ thd . If P inband >P′ thd , the transmitter needs to be reduced by adjusting the variable gain amplifier of the programmable RF transmit link. Output power to avoid interference with upstream signals.
  • P inband ⁇ P' thd the gain of the variable gain amplifier is automatically increased to ensure the strength of the transmitted signal. The adjustment process is shown in FIG.
  • the distributed antenna system when the isolation of the transmitting and receiving antennas is deteriorated, the distributed antenna system can be stably operated by automatic adjustment.
  • the gain distribution of the receiver or the output power of the transmitter is adjusted, the uplink noise figure is increased or the downlink output power is decreased, and the coverage of the distributed antenna system is correspondingly reduced. Therefore, while the system is automatically adjusted, a user alarm signal is generated to prompt the network maintenance personnel to check the electromagnetic environment around the device. After the network maintenance personnel eliminates the factors that cause the antenna transceiver isolation to deteriorate, the system automatically returns to the optimal working state.
  • the present invention provides a remote unit for a distributed antenna system supporting a full frequency band, which can support any 2G/3G/4G frequency band through software configuration, and supports smooth evolution to 5G without replacing any hardware equipment.

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Abstract

本发明提供一种支持全频段的分布式天线系统远端单元及实现方法，其包括：可编程的逻辑处理单元FPGA、可编程的射频发射链路、可编程的射频接收链路以及收发天线。通过在可编程射频发射链路设置监控通道a和可编程射频接收链路设置监控通道b，实现收发天线的隔离度的监控、自适应调整，从而，在不需要更换硬件系统的前提下，仅通过软件配置即可支持所有的2G/3G/4G频段，并支持向5G的平滑升级，使用方便，系统总体成本较现有产品大大降低。

Description

一种支持全频段的分布式天线系统远端单元及实现方法 技术领域
本发明涉及无线通信技术领域，尤其涉及一种支持全频段的分布式天线系统远端单元及实现方法。
背景技术
当前，分布式天线系统系统主要用于解决大型建筑物的室内信号覆盖问题，如(商场、体育馆、大型写字楼等)。随着室内业务量的提升，分布式天线系统系统需要不断升级和扩容，以满足新增的需求；同时，5G即将商用，现有的分布式天线系统系统需要重新改造来实现对5G频段的支持。
现有的分布式天线系统远端单元是基于频率定制的系统，如图1所示，现有的分布式天线系统收发链路中存在固定频率的滤波器和双工器，只能支持特定的频率范围。在系统升级或扩容的过程中，如果需要支持不同的频段，或者新增频段，只能通过更换设备的方式进行。例如，5G移动通信室内覆盖普遍采用3.5GHz频段，而现有的2G/3G/4G集中在700M～2700MHz频段，升级到支持5G必须更换硬件系统，这样就造成了设备的重复投资，同时更换硬件需要大量的人力成本，系统总体造价高昂。
如果分布式天线系统设备要支持所有的射频频段，那么射频收发链路上不能有射频滤波器、双工器等频率部件并且链路上的所有器件需支持全频率范围。当前，已有芯片厂商推出支持0到6GHz全频率范围的射频器件，设计全频率范围的分布式天线系统系统理论上已经可行。但是，由于收发链路上没有射频滤波器件，发射通道对接收通道的干扰问题不可忽视，严重时甚至会导致系统瘫痪。发射通道对接收通道的干扰来自于2个方面：一方面是发射信号被接收天线接收，导致接收链路的器件饱和，产生严重的非线性；另一方面，发射链路功率放大器产生的信号互调分量，有可能落在上行频率范围内，影响上行信号质量。正常情况下，由收发天线的空间隔离度来保证下行信号不干扰上行，但由于设备或天线附近的电磁环境改变，如空间新增金属档板等，导致收发天线的隔离度发生变化，可能导致系统性能恶化，甚至无法工作。
发明内容
针对上述技术存在的不足，本发明提出了一种支持全频段的分布式天线系统 远端单元及实现方法，其中，一种支持全频段的分布式天线系统远端单元，主要包括：可编程的逻辑处理单元FPGA、可编程的射频发射链路、可编程的射频接收链路以及收发天线。
其中，所述可编程逻辑处理单元FPGA的功能，(1)用于实现与分布式天线系统近端机的通信，接收下行信号并将上行信号发送到近端机；(2)用于接收从分布式天线系统近端机来的数字信号，进行数字滤波和数字上变频以及数字预失真DPD、正交调制器校正QMC等处理，发送到所述可编程的射频发射链路；(3)用于接收从所述可编程的射频接收链路来的数字信号，进行数字下变频和数字滤波，发送到分布式天线系统近端机；(4)用于与可编程的射频链路配合实现所述收发天线的隔离度的监控，以及对分布式天线系统进行自适应调整。
所述可编程射频发射链路，主要包括数模转换器、可编程的本振发生器、正交调制器、可变增益放大器、高功率放大器、监控通道a。
所述可编程射频发射链路，用于接收所述可编程逻辑处理单元FPGA的数字信号，进行数模转换后得到模拟信号S1，根据本振信号的软件配置，将信号S1调制到需要发射的射频频率，通过可变增益放大器以及高功率增益放大器进行放大。所述可变增益放大器用于输出功率调节以及收发天线的隔离度变化时系统的自动调节。
所述可编程射频发射链路的监控通道a，主要包括射频耦合器、下混频器和模数转换器，用于可编程逻辑处理单元FPGA获取所述可编程射频发射链路的信号互调分量，以及数字预失真DPD和正交调制器校正QMC的反馈链路。
所述可编程射频接收链路，主要包括可调衰减器、低噪声放大器、可编程的本振发生器、正交解调器、可编程低通滤波器、可变增益放大器、模数转换器，以及监控通道b。
所述可编程射频接收链路，用于接收从天线来的上行信号，经过放大后，根据本振信号的软件配置，将特定的射频频率解调到基带，然后经过低通滤波和模数转换器采样后，送到可编程逻辑处理单元FPGA。
所述可编程射频接收链路中的可调衰减器和可变增益放大器，用于系统隔离度变化时调整链路增益分配。
所述接收链路的监控通道b，主要包括射频耦合器、本振发生器、下混频器、 可编程低通滤波器以及功率检测电路，用于测量发射信号到达所述可编程射频接收链路的功率，计算收发天线之间的隔离度。
本发明还提供一种支持全频段的分布式天线系统远端单元的实现方法，通过所述方法可实现所述收发天线的隔离度的监控、自适应调整。
其中，所述收发天线之间的隔离度计算方法包括：
步骤(1)：通过所述监控通道a获取所述可编程的发射链路的输出功率P out。假设监控通道a的增益为G t，所述可编程逻辑处理单元FPGA检测到的监控通道a输出功率为P t，P out＝P t+G t。
步骤(2)，配置监控通道b的本振发生器和可编程低通滤波器的带宽，使发射信号的频谱处于可编程低通滤波器的通带内，功率检测电路的输出功率P r为接收到的发射功率。假设接收天线口到监控通道b功率检测电路的增益为G r，对应到接收天线口的功率P in，P in＝P r+G r。
所述收发天线之间的隔离度G，G＝P in-P out。
所述分布式天线系统的自适应调整方法，包括：
若监控通道b检测到的功率P in大于所述可编程的射频接收链路可承受的最大输入功率门限P thd，通过调整所述可编程的射频接收链路中的可调衰减器的值，使进入所述可编程的射频接收链路中的LNA的功率不超过P thd。通过增大所述可编程的射频接收链路中的可变增益放大器的增益，维持所述可编程的射频接收链路的增益不变。
当外部环境变化导致所述收发天线隔离度的变大，若监控通道b检测到的功率P in小于所述可编程的射频接收链路可承受的最大输入功率门限P thd，则自动调整可调衰减器和可变增益放大器的值，用于改善所述可编程的射频接收链路的噪声系数。
所述分布式天线系统的自适应调整方法，还包括：
可编程逻辑处理单元FPGA采用数字滤波器对监控通道a收到的信号进行滤波，获取发射信号的互调分量位于接收频段内的功率P IMD，互调分量到达接收天线的功率P inband＝P IMD+G。定义所述可编程的射频接收链路的干扰信号允许的最高门限为P′ thd，若P inband＞P′ thd，则通过减小所述可编程的射频发射链路的可变增益放大器来降低输出功率，以避免干扰上行信号。当外部环境变化导致所 述收发天线隔离度增大，P inband＜P′ thd，则通过增大所述可编程的射频发射链路的可变增益放大器的增益，以保证发射信号的强度。
本发明的有益效果：在不需要更换硬件系统的前提下，仅通过软件配置即可支持所有的2G/3G/4G频段，并支持向5G的平滑升级，使用方便，系统总体成本较现有产品大大降低。
附图说明
图1是传统的分布式天线系统远端单元示意图；
图2是本发明的分布式天线系统远端单元示意图；
图3是本发明分布式天线系统的自适应调整方法1的流程图；
图4是本发明分布式天线系统的自适应调整方法2的流程图。
具体实施方式
以下结合附图对本发明的实施例进行进一步详细说明。
若图1所示，传统的分布式天线系统远端单元，其射频收发链路通常包含射频滤波器、双工器等频率定制器件，无法支持全频段的应用。
图2是本发明本发明的分布式天线系统远端单元，可编程的射频发射链路主要包括顺序连接的数模转换器、本振发生器、正交调制器、可变增益放大器、高功率增益放大器、监控通道a，实现下行信号的发射功能。
其中，射频调制采用零中频调制方案，以避免调制器的镜像和本振泄漏产生带外杂散。因为发射链路监控通道a的存在，可编程逻辑处理单元FPGA可以通过实时的正交调制器校正QMC算法对正交调制器进行校正。正交调制器校正QMC算法是业界通用算法，在此不再赘述。
如图2所示，可编程的射频发射链路中的可变增益放大器可用于动态调节输出功率，可用于在收发天线隔离度变化时对系统增益进行自适应调整，见下文所述。
如图2所示，监控通道a从高功率增益放大器后耦合射频信号，经过下变频后，由模数转换器采样，将采样后的数字信号送到可编程逻辑处理单。该监控通道a有3个作用：一是作为数字预失真DPD和正交调制器校正QMC的观测通道，二是获取高功率增益放大器的输出功率，三是提取发射信号的互调分量，用于衡量该互调是否会对上行信号存在干扰。
如图2所示，可编程的射频接收链路主要包括顺序连接的可调衰减器、低噪声放大器、本振发生器、正交解调器、可编程低通滤波器、可变增益放大器、模数转换器、监控通道b，实现射频信号的接收功能。
其中，可调衰减器和可变增益放大器可以动态调整链路的增益分配，用于在收发天线隔离度变化时对系统增益进行自适应调整，见下文所述。
如图2所示，监控通道b从低噪声放大器后耦合信号，下变频后由可编程滤波器滤除不需要的频率分量，然后进入功率检测电路。检出的功率值送到可编程逻辑处理单元FPGA，用于计算系统收发天线的隔离度。
如图2所示，可编程逻辑处理单元FPGA，主要用于实现与分布式天线系统近端机的通信和数字信号处理功能，包括数字滤波、数字上变频、数字下变频、数字预失真DPD、正交调制器校正QMC等。同时，可编程逻辑处理单元FPGA用于监控收发天线之间的隔离度，并根据隔离度的变化自适应调整系统的增益，使其能稳定工作。
根据上文所述，可编程的射频发射链路对可编程的射频接收链路的干扰主要来自于2个方面。其中，发射信号直接被接收天线接收，如果隔离度太差，可能导致可编程的射频接收链路的饱和。
收发天线之间的隔离度计算方法如下：
首先，通过监控通道a获取发射链路的输出功率P out。假设监控通道a的增益为G t，可编程逻辑处理单元FPGA检测到的监控通道a输出功率为P t，那么P out＝P t+G t。
配置监控通道b的本振和可编程低通滤波器的带宽，使发射信号的频谱处于低通滤波器的通带内，此时检波器的输出功率P r为接收到的发射功率。假设接收天线口到监控通道b检波器的增益为G r，那么对应到接收天线口的功率为P in＝P r+G r。由此可以得出收发天线之间的隔离度G为：
G＝P in-P out
根据上文所述，可编程的射频发射链路对可编程的射频接收链路的干扰主要来自于2个方面。其中，发射信号直接被接收天线接收，如果隔离度太差，可能导致可编程的射频接收链路的的饱和。针对该情况的自适应调整方法如下：
如果监控通道b检测到的功率P in大于接收机可承受的最大输入功率门限P thd， 那么调整低噪声放大器前的可调衰减器的值，使进入低噪声放大器的功率不超过P thd。同时，该干扰信号会被低通滤波器滤除，所以可以增大滤波器后的可变增益放大器的增益，来维持整个接收机的增益不变。当外部环境变化导致收发天线隔离度变大，P in＜P thd，则自动调整可调衰减器和可变增益放大器的值，以改善接收机的噪声系数。所述调整流程如图3所示。
根据上文所述，由于可编程的射频发射链路器件的非线性产生的信号互调分量，可能会对上行信号造成干扰。例如，3GPP Band3，其下行频率范围是1805MHz到1880MHz，上行频率范围为1710MHz到1785MHz。由于上下行频率间隔很小，下行信号的互调分量正好处于上行频段内，如果天线的收发隔离度比较小，可能会对上行信号造成阻塞。针对该情况的调整方法如下：
首先，根据上文所述方法计算收发天线的隔离度G。然后，可编程逻辑处理单元FPGA采用数字滤波器对监控通道a收到的信号进行滤波，获取发射信号的互调分量位于接收频段内的功率P IMD。由此可以计算出该互调分量到达接收天线的功率P inband＝P IMD+G。定义接可编程的射频接收链路的干扰信号允许的最高门限为P′ thd，如果P inband＞P′ thd，则需要通过调整可编程的射频发射链路的可变增益放大器来减小发射机输出功率，以避免干扰上行信号。当外部环境变化导致收发天线隔离度增大，P inband＜P′ thd，则自动增大可变增益放大器的增益，以保证发射信号的强度。所述调整流程如图4所示。
根据上文所述，当收发天线隔离度变差后，分布式天线系统经过自动调整能稳定工作。但由于调整了接收机的增益分配或发射机的输出功率，会导致上行噪声系数增大或下行输出功率减小，会相应的减小分布式天线系统的覆盖范围。因此，系统在自动调整的同时，还产生用户告警信号，以提示网络维护人员检查设备周边电磁环境。待网络维护人员消除了导致天线收发隔离度变差的因素后，系统会自动恢复到最佳工作状态。
由上可知，本发明提供一种支持全频段的分布式天线系统远端单元，可通过软件配置支持任意2G/3G/4G频段，并支持向5G的平滑演进，无需更换任何硬件设备。
最后需要说明的是，以上实施例仅用于说明本发明的技术方案，而非对其限制。本领域的相关技术人员根据本方案对以上实施例的修改或者对部分功能单元 的等同替换，均不脱离本发明的保护范围。

Claims (7)

  1. 一种支持全频段的分布式天线系统远端单元，远端单元包括：可编程的逻辑处理单元FPGA、可编程的射频发射链路、可编程的射频接收链路以及收发天线，所述可编程射频发射链路包括数模转换器、可编程的本振发生器、正交调制器、可变增益放大器、高功率放大器，所述可编程射频接收链路包括可调衰减器、低噪声放大器、可编程的本振发生器、正交解调器、可编程的低通滤波器、可变增益放大器、模数转换器，其特征在于，所述可编程射频发射链路设置监控通道a，所述可编程射频接收链路设置监控通道b。
  2. 根据权利要求1所述的支持全频段的分布式天线系统远端单元，其特征在于，所述可编程射频发射链路的监控通道a，主要包括：射频耦合器、下混频器和模数转换器，用于获取所述可编程射频发射链路的输出功率和信号互调分量。
  3. 根据权利要求1所述的支持全频段的分布式天线系统远端单元，其特征在于，所述可编程射频接收链路的监控通道b，主要包括：射频耦合器、本振发生器、下混频器、可编程的低通滤波器以及功率检测电路，用于测量发射信号到达所述可编程射频接收链路的功率，计算所述收发天线之间的隔离度。
  4. 一种支持全频段的分布式天线系统远端单元的实现方法，其特征在于，所述方法可实现所述收发天线的隔离度的监控、自适应调整。
  5. 根据权利要求4所述的支持全频段的分布式天线系统远端单元的实现方法，其特征在于，所述收发天线之间的隔离度计算方法包括：
    步骤(1)：通过所述监控通道a获取所述可编程的发射链路的输出功率P out；假设监控通道a的增益为G t，所述可编程逻辑处理单元FPGA检测到的监控通道a输出功率为P t，P out＝P t+G t；
    步骤(2)，配置监控通道b的本振发生器和可编程低通滤波器的带宽，使发射信号的频谱处于可编程低通滤波器的通带内，功率检测电路的输出功率P r为接收到的发射功率；假设接收天线口到监控通道b功率检测电路的增益为G r，对应到接收天线口的功率P in，P in＝P r+G r；
    所述收发天线之间的隔离度G，G＝P in-P out。
  6. 根据权利要求4所述的支持全频段的分布式天线系统远端单元的实现方法，其特征在于，所述分布式天线系统的自适应调整方法，包括：
    若监控通道b检测到的功率P in大于所述可编程的射频接收链路可承受的最大输 入功率门限P thd，通过调整所述可编程的射频接收链路中的可调衰减器的值，使进入所述可编程的射频接收链路中的LNA的功率不超过P thd；通过增大所述可编程的射频接收链路中的可变增益放大器的增益，维持所述可编程的射频接收链路的增益不变；
    当外部环境变化导致所述收发天线隔离度的变大，若监控通道b检测到的功率P in小于所述可编程的射频接收链路可承受的最大输入功率门限P thd，则自动调整可调衰减器和可变增益放大器的值，用于改善所述可编程的射频接收链路的噪声系数。
  7. 根据权利要求4所述的支持全频段的分布式天线系统远端单元的实现方法，其特征在于，所述分布式天线系统的自适应调整方法，还包括：可编程逻辑处理单元FPGA采用数字滤波器对监控通道a收到的信号进行滤波，获取发射信号的互调分量位于接收频段内的功率P IMD，互调分量到达接收天线的功率P inband＝P IMD+G；定义所述可编程的射频接收链路的干扰信号允许的最高门限为P′ thd，若P inband＞P′ thd，则通过减小所述可编程的射频发射链路的可变增益放大器来降低输出功率，以避免干扰上行信号；当外部环境变化导致所述收发天线隔离度增大，P inband＜P′ thd，则通过增大所述可编程的射频发射链路的可变增益放大器的增益，以保证发射信号的强度。
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