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The microwave passive components of an RF front-end of a modern base station include filters, couplers, dividers, matching networks and so on, used to shape, direct and condition signals. With the development of base stations to accommodate 5G massive MIMO and dense frequency allocations, the demands of these components have never been so great. Base station front-end issues are solvable at Linkworld, where we design and produce passive components that are optimized to base station environments, and we have more than 20 years of RF experience. Four key considerations are discussed in this guide.
Filter Performance: Selectivity and Insertion Loss
The initial blockade to interference is filters. They have to strike inconsistent objectives: low insertion loss at passband frequencies to maintain signal level, and high rejection in the out-of-band to reject interference. In case of 5G sub-6 GHz applications, bandpass filters are generally expected to have an insertion loss of less than 1 dB with rejection of over 50 dB at neighboring bands. New designs of filtennas incorporate filtering along with antenna element and minimize transition losses in massive MIMO arrays with compact sizes. The portfolio of filters offered by Linkworld covers these technologies and allows the best solution to be found to meet a particular frequency band and performance objective.
Power Dividers and Couplers: Balance and Isolation
Power dividers and couplers are used to distribute signals to more than one antenna element and synthesize signals of diversity receivers. Phased array and MIMO uses amplitude and phase balance. High-performance dividers are amplitude balanced with amplitude variation of ±0.1 dB and phase balanced with ±1 degree at operating bands. Output ports isolation eliminates unexpected array behavior and oscillation trajectories. In the case of power monitoring loops, directional couplers are used to measure VSWR and amplifier protection. In this context the directionality applies to the accuracy of the measurements of VSWR and to the value of amplifier protection. The power dividers and couplers of Linkworld are designed with accuracy in internal designs that provide the balance and isolation of the modern architecture of the base stations.
Integration Technologies: LTCC and IPD Solutions
The diminishing size of base stations and the functionality they are able to provide are driving an increasing replacement of discrete components with integrated solutions. The Low-Temperature Co-fired Ceramic (LTCC) technology is used to make filters, baluns, couplers, and matching networks integrated in multilayer ceramic modules up to 20-layers thick. LTCC offers outstanding design flexibility in terms of thermal stability and low loss in dielectric. To achieve increased miniaturization, Integrated Passive Devices (IPD) on high-resistivity silicon material or GaAs substrates are chips that many functions loaded on them. These attain a quality factor of more than 30 at 1 GHz with sufficient power capability. The engineering department at Linkworld assists customers to formulate these choices and choose the integration methodology that will be effective in terms of performance, size, and cost.
PIM Performance and System Linearity
Passive intermodulation (PIM) has proven to be a performance distinguishing element. Having many high-power carriers pass through non-linear junctions in passive components, they cause interference that desensitizes collocated receivers. The sources of PIM are ferromagnetic materials, ineffective contact between unlike metals, loose mechanical connectivity and contamination. PIM specifications of -150 dBc or higher are becoming standard as tower-mounted components. The design of low-PIM necessitates the removal of ferromagnetic materials, uniform plating systems, and mechanical construction with high integrity allowing contact integrity despite thermal cycling and vibration. The passive components of Linkworld are designed specifically to provide a low-PIM performance and the material choices as well as manufacturing processes are confirmed by thorough testing.
The capacity, coverage, and reliability of wireless networks essentially depend on the microwave passive components. Sharply selective, low loss filters, precisely balanced dividers, integrated technologies that allow densely packed MIMO arrays, PIM free designs, all components must be tailored to the requirements of the front end of the base station. Linkworld has more than twenty years of RF manufacturing experience and extensive telecommunications knowledge base, which has given the company the passive components that network operators and OEMs rely on when deploying the most critical base stations. Get in touch with us regarding your front-end design needs.