無線中繼器(RF Repeater)由天線、射頻雙工器、低雜訊放大器、混頻器、電調衰減器、濾波器、功率放大器等元器件或模組組成，包括上、下行兩種放大鏈路。其工作的基本原理是：用前向天線（施主天線）將基站的下行信號接收進直放機，通過低噪放大器將有用信號放大，抑制信號中的雜訊信號，提高信噪比（S/N）；再經下變頻至中頻信號，經濾波器濾波，中頻放大，再移頻上變頻至射頻，經功率放大器放大，由後向天線（重發天線）發射到移動台；同時利用後向天線接收移動台上行信號，沿相反的路徑由上行放大鏈路處理：即經過低噪放大器、下變頻器、濾波器、中放、上變頻器、功率放大器再發射到基站。從而達到基站與移動台的雙向通信。

數位直放站，主要區別與類比直放站的是在中間處理環節和中繼環節採用了數位的處理方式，數位中頻、數位濾波等技術。

5G 採用更高的頻譜以獲取更多頻寬資源，然而無線信號的傳播特性是頻率越高在空間傳播的空間損耗越大，這將影響其覆蓋能力。根據傳播模型測算，相同距離下：3.5GHz 比 1.8GHz 路徑損耗高 5.8dB 左右；3.5GHz 比 2.1GHz 路徑損耗高 4.4dB 左右。

5G TDD-NR 基站一般都採用大規模天線陣列，天線數目的增多為傳播通道提供了更多的複用增益和分集增益，使得系統在下行方向的資料速率、鏈路可靠性和覆蓋上擁有更好的性能。

但是在上行方向，即從終端向基站發送資料的通路上，終端的發射功率限制使了 5G 上行的覆蓋。此外，終端體積限制了天線數量，無法利用Massive MIMO，再加上 TDD 上下行時隙配比的差異等，進一步擴大了上下行覆蓋的差距。TDD-NR 的上行覆蓋受限，使得使用者在超出上行覆蓋區域之後就無法使用 5G 下行的高速資料業務，限制了 5G 下行大頻寬的優勢。 

加大基站密度固然可以解決5G覆蓋問題，但5G基站價格高昂，且耗電量大，運營商難以承受高昂的建設及運營成本。

5G微功率直放站介紹

• 採用先進的解幀同步技術，得到精確的同步控制信號 ；
• 上行最高功率23dBm，外接施主天線EIRP遠遠高於5G終端，大大改善5G網路上行覆蓋效果；
• 自帶隔離度檢測、AGC和自動休眠等智慧能功能；
• 支援2T2R MIMO，下載速率可達620Mbps；
• 高清智慧能顯示幕，輕鬆瞭解設備運行狀態 
• 可選藍牙連接APP監控功能，支援本地電腦連線。

The repeater consists of antennas, radio frequency duplexers, low-noise amplifiers, mixers, ESC attenuators, filters, power amplifiers and other components or modules, including uplink and downlink amplification links. The basic principle of its work is: use the forward antenna (donor antenna) to receive the downlink signal of the base station into the repeater, amplify the useful signal through the low-noise amplifier, suppress the noise signal in the signal, and improve the signal-to-noise ratio (S/ N); then down-converted to intermediate frequency signal, filtered by filter, amplified at intermediate frequency, shifted and up-converted to radio frequency, amplified by power amplifier, transmitted from the backward antenna (retransmission antenna) to the mobile station; The backward antenna receives the mobile station's uplink signal, and is processed by the uplink amplification link along the opposite path: that is, it passes through the low-noise amplifier, down-converter, filter, intermediate amplifier, up-converter, and power amplifier and then transmits to the base station. So as to achieve two-way communication between the base station and the mobile station. 

The main difference between digital repeaters and analog repeaters is that they adopt digital processing methods, digital intermediate frequency, digital filtering and other technologies in the intermediate processing link and relay link.

5G uses higher frequency spectrum to obtain more bandwidth resources. However, the propagation characteristics of wireless signals are that the higher the frequency, the greater the spatial loss of space propagation, which will affect its coverage capability. According to the calculation of the propagation model, at the same distance: the path loss of 3.5GHz is about 5.8dB higher than that of 1.8GHz; the path loss of 3.5GHz is about 4.4dB higher than that of 2.1GHz.

5G TDD-NR base stations generally use large-scale antenna arrays. The increase in the number of antennas provides more multiplexing gain and diversity gain for the propagation channel, enabling the system to have better data rates, link reliability, and coverage in the downlink direction. good performance.

However, in the uplink direction, that is, on the path from the terminal to the base station, the transmission power limit of the terminal makes the 5G uplink coverage. In addition, the size of the terminal limits the number of antennas, and Massive MIMO cannot be used. Coupled with the difference in the TDD uplink and downlink time slot ratios, the gap between uplink and downlink coverage is further expanded. The limited uplink coverage of TDD-NR makes it impossible for users to use 5G downlink high-speed data services after exceeding the uplink coverage area, limiting the advantages of 5G downlink large bandwidth.

Increasing the density of base stations can certainly solve the problem of 5G coverage, but 5G base stations are expensive and consume a lot of power, making it difficult for operators to bear the high construction and operation costs.