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Mobile Communication / LTE

LTE: Technology and Filter Requirements

LTE (Long-Term Evolution) remains the established fourth-generation global standard, serving as the backbone of connectivity with a spectrum ranging from 700 MHz to 3.8 GHz. While low-band frequencies like Band 20 (800 MHz) and Band 28 (700 MHz) primarily ensure wide-area coverage, mid-bands such as Band 3 (1.8 GHz) and Band 7 (2.6 GHz) provide the necessary capacity for urban centers. The primary challenge for RF infrastructure today lies in coexistence: filters must be extremely steep to prevent interference between LTE bands, digital broadcasting, and adjacent 5G services in DSS scenarios.

Wainwright Instruments provides solutions tailored exactly to 3GPP specifications for eNodeBs and infrastructure components. Our filters minimize intermodulation in multi-band environments and enable maximum spectrum utilization through high selectivity. This is essential for maintaining Quality of Service (QoS) for VoLTE and broadband applications even under high network loads.

Typical Deployment Scenarios:

LTE filters from Wainwright are critical components in systems requiring high signal purity and protection against out-of-band emissions throughout their lifecycle.

  • Macro and Micro Cells: In LTE base stations (eNodeBs), our filters ensure precise channel separation in the B7 capacity band (2.6 GHz) and reliably isolate uplink and downlink signals in crowded frequency spaces.
  • Industrial Campus Solutions: For private LTE networks, often operating in the Band 40 (2.3 GHz) or Band 42/43 (3.5 GHz) ranges, we offer tuned filters that guarantee exclusive frequency use without interference from public networks.
  • Rural Broadband Coverage: Within stationary FWA (Fixed Wireless Access) routers, our filters ensure stable signal integrity in the long-range Band 20 (800 MHz), providing fast internet in underserved areas.
  • Public Safety & PPDR: Our specialized filters offer highest reliability for integrating LTE into safety networks, such as in the specialized narrowband B31 (450 MHz) or B72 (450 MHz) bands.
  • Narrowband IoT (NB-IoT & LTE-M): To protect the extremely high receiver sensitivity required for applications deep indoor or underground, optimized filters are used to effectively mask interfering signals.
  • Maximizing Throughput: Multiple bands like B3 + B7 + B20 can be bundled using Carrier Aggregation (CA); our combination filters enable this efficient use of non-contiguous spectrum blocks.
  • Laboratory & Compliance Testing: High-precision filters in test and measurement systems are used to validate LTE components, ensuring strict adherence to 3GPP limits for out-of-band emissions.
  • Connected Vehicles: Reliable connections for eCall systems and telemetry in Band 3 (1.8 GHz) are achieved through filter solutions that operate stably even under extreme automotive thermal conditions.

Suitable Filter Categories for Mobile Communications / LTE

The global LTE ecosystem utilizes a wide range of FDD and TDD bands. Wainwright Instruments offers optimized filter solutions with high quality factors and thermal stability, fine-tuned to the power requirements of specific infrastructure or testing applications.

Band Pass Filters

Precise channel selection for bands such as B1 (2100 MHz), B3 (1800 MHz), and B20 (800 MHz) is enabled by our LTE Band Pass filters. They are specifically optimized for high-power amplifiers and base station hardware, combining steep rejection with minimal insertion loss. This combination maximizes the thermal efficiency of power amplifiers and ensures that strict spectral masks are maintained even under high loads. For space-sensitive micro-cells, we offer compact variants that guarantee reliable suppression of adjacent services.

Manually Tunable Band Pass Filters

Covering wide frequency ranges from 240 MHz to 9 GHz, our manually tunable Band Pass filters are designed specifically for LTE development applications. Via stable tuning elements, the center frequency can be adjusted with high accuracy for specific laboratory measurement setups or field troubleshooting. They are the ideal choice for characterizing prototypes across various bands, as they eliminate the need for physical hardware swaps. Technicians value the robust design particularly for portable use at radio masts to quickly and safely identify local interference sources.

Digitally Tunable Band Pass Filters

Modern SDR (Software Defined Radio) systems and automated LTE test benches benefit from our electronically controllable filters. Filter curves can be adjusted in real-time via digital interfaces like SPI to changing parameters, which is essential for carrier aggregation testing and research in the NB-IoT sector. This algorithm-driven adjustment allows for an extremely rapid response to frequency shifts in automated test environments. Our digital filters are optimized for use in reconfigurable test environments and measurement systems, combining digital control precision with high RF quality.

Band Reject Filters / Notch Filters

Targeted elimination of narrowband interfering signals, such as those caused by adjacent broadcast transmitters in the 800 MHz (Band 20) range, is handled by our high-efficiency LTE notch filters. They offer extremely deep stopband attenuation while the actual LTE desired signal remains nearly unaffected. This protection prevents sensitive LNAs from saturation by strong external signals and ensures maximum receiver sensitivity for the station. Especially in urban areas, these filters effectively prevent receiver overloading, contributing significantly to general spectrum hygiene.

Manually Tunable Band Reject Filters / Notch Filters

Frequency-tunable notch filters provide a flexible solution for interference suppression from Band 28 (700 MHz) to Band 7 (2.6 GHz). System integrators use manual adjustment of the stopband frequency to respond immediately to new interference sources on-site without having to swap hardware components. These filters are an indispensable tool for test laboratories validating complex coexistence scenarios between LTE and other radio services. The mechanical construction is designed to be robust enough that settings remain precisely reproducible even with frequent transport and use.

Digitally Tunable Band Reject Filters / Notch Filters

Automated responses to interference scenarios in intelligent LTE networks are enabled by digitally tunable notch filters. Controlled by monitoring algorithms, these filters dynamically mask interfering signals to maintain Quality of Service (QoS). Their seamless integration into automation concepts for radio optimization is particularly beneficial in smart factories where production can generate varying interference sources. Thanks to remote controllability, operators can adjust filter parameters centrally, making expensive on-site technician visits unnecessary.

Monoplexer / Diplexer / Duplexer / Triplexer

Combining multiple frequency blocks such as B3 + B7 + B20 for LTE-Advanced requires high-performance multiplexers. Our solutions guarantee high isolation between ports with extremely low insertion loss to achieve maximum data rates through carrier aggregation. In FDD scenarios, our duplexers allow for reliable separation of uplink and downlink signals under high power handling. Wainwright Instruments develops these components specifically for modern multi-band RRUs to increase radio cell capacity and eliminate disruptive signal crosstalk.

Absorptive Filters

To increase system linearity in high-power LTE transmit stages, absorptive filters are a crucial component. They convert unwanted harmonics directly into heat rather than reflecting them back to the power amplifier. This protection against reflection damage is essential for complying with strict spectral emission masks (SEM) in complex multi-band configurations. Our absorptive filters are designed for high continuous power and are used in both macro cells and test equipment to improve signal purity and significantly reduce error rates.