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Satellite Navigation / GLONASS

GLONASS: Technology and Filter Requirements

GLONASS (Globalnaja Nawigazionnaja Sputnikowaja Sistema) is the Russian counterpart to the American GPS and an indispensable component in modern multi-GNSS receivers. The technological hallmark of GLONASS has traditionally been its use of FDMA (Frequency Division Multiple Access), where satellites transmit on different frequencies within the L1 (1598.06 MHz to 1605.38 MHz) and L2 (1242.94 MHz to 1248.63 MHz) bands. Modern satellite generations also utilize the L3 band (1202.025 MHz) with advanced CDMA modulations. Since GLONASS signals occupy a wider spectrum than GPS due to the FDMA approach, they impose extreme requirements on filter hardware to process the necessary bandwidth without phase distortion. Wainwright Instruments manufactures specialized high-performance filters for these high-sensitivity applications, designed to precisely isolate GLONASS bands from terrestrial interference. A particular challenge is the proximity to the Iridium network (1616 MHz to 1626.5 MHz) and mobile satellite services in the L-band, which can saturate receiver front-ends. Our solutions ensure exceptional group delay stability, which is vital for precise timing and positioning - especially in high northern latitudes where GLONASS coverage is optimized.

Typical Deployment Scenarios

In professional navigation environments, our filters function as protective barriers to ensure the integrity of GLONASS data streams under the most difficult RF conditions.

  • Arctic Maritime & Navigation: Because GLONASS provides superior coverage in polar regions due to its orbital inclination, our filters protect receivers on icebreakers and research vessels against powerful on-board S-band radar systems.
  • Multi-Constellation Reference Stations: In global base stations receiving GPS, Galileo, and GLONASS simultaneously, our filters ensure clean separation of L1/L2/L3 signals with minimal internal noise.
  • Avionics & Flight Guidance: In aircraft navigation systems, our RF components protect navigation modules from interference caused by on-board high-power transmitters for satellite communication (Satcom) in the 1.6 GHz range.
  • Precision Agriculture (Smart Farming): Autonomous tractors use GLONASS to augment GPS; our filters eliminate interference from local LTE-M or NB-IoT networks to enable lane-accurate guidance.
  • Critical Time Referencing (Timing): In utility infrastructures or cellular networks, our filters protect GLONASS timing antennas from overloading by neighboring 5G base stations (gNodeBs) at the same mast.
  • Military Reconnaissance & Logistics: In protected receivers, our filter solutions prevent the blocking of radio paths by intentional jamming or unintentional broadband atmospheric interference.
  • Geodesy & Land Surveying: For high-precision surveying equipment, we supply filters with minimal insertion loss to optimize the Signal-to-Noise Ratio (SNR) of weak satellite signals for millimeter-accurate measurements.
  • Autonomous Transport Robots: In expansive industrial areas, our components secure the GLONASS connection against electromagnetic pulses from heavy machinery and industrial Wi-Fi networks.

Suitable Filter Categories for Satellite Navigation / GLONASS

The specific FDMA structure and high demands for signal purity require filter solutions that combine extraordinary selectivity and thermal stability.

Band Pass Filters

Our GLONASS Band Pass filters enable precise selection of L1, L2, and L3 bands. They are specifically optimized for use in professional navigation systems and infrastructure applications, combining steep rejection skirts with minimal insertion loss. This maximizes receiver sensitivity and protects high-sensitivity Low Noise Amplifiers (LNAs) from saturation by strong neighboring signals in the LTE Band 7 (2.6 GHz) or 5G n78 (3.5 GHz) range. By using high-quality resonators, we ensure that phase linearity is maintained across the entire FDMA spectrum, directly improving positioning accuracy. Manufacturers of infrastructure components benefit from the high power handling and precision of our filters.

Manually Tunable Band Pass Filters

For the development of GLONASS hardware in laboratory environments, we offer manually tunable Band Pass filters covering the range from 1100 MHz to 1700 MHz. Via high-precision mechanical tuning elements, the passband can be adjusted exactly to specific GLONASS channels or experimental frequency ranges. This flexibility allows engineers to investigate the robustness of their receiver designs against targeted broadband interference or neighboring satellite services like BeiDou or Galileo in the lab. The robust construction of our manually tunable filters guarantees permanent reproducibility of measurement results.

Digitally Tunable Band Pass Filters

Electronically controllable filters support modern SDR-based navigation architectures and automated test environments that must react agilely to various global GNSS constellations. Via digital interfaces, filter parameters can be adjusted in real-time, which is particularly advantageous for automated test sequences checking channel selectivity. Our digitally tunable filters combine digital control precision with the necessary RF quality and are optimized for use in test environments and development systems. They enable rapid reconfiguration of test scenarios without manual hardware swaps and support efficient quality assurance processes.

Band Reject Filters / Notch Filters

Our GLONASS notch filters serve to eliminate specific strong interfering signals located immediately adjacent to or within the utilized navigation spectrum, such as strong cellular carriers or terrestrial microwave links. They feature extremely deep stopband attenuation while the rest of the GLONASS passband remains nearly unaffected. This protection is fundamental to prevent saturation of high-sensitivity receiver front-ends in urban environments. By using our notch filters, the robustness of the infrastructure against narrowband interferers is massively increased, increasing positioning availability.

Manually Tunable Band Reject Filters / Notch Filters

Frequency-tunable notch filters provide a flexible solution for interference suppression directly in the field during the commissioning of reference stations. By manually adjusting the stopband frequency, interfering signals caused, for example, by poorly performing radio systems in the vicinity can be masked immediately. This ensures the availability of navigation services without waiting for new filter hardware. The mechanical precision of our filters guarantees that once a stopband frequency is found, it remains stable, which is particularly decisive for permanently installed antenna sites on bridges or masts.

Digitally Tunable Band Reject Filters / Notch Filters

In intelligent navigation networks, digitally tunable notch filters enable an automated response to dynamic interference scenarios. Controlled by monitoring algorithms, these filters can dynamically mask interfering signals in real-time to maintain precision for critical applications such as automatic port maneuvers. Their integration into automation concepts for radio optimization allows for autonomous radio optimization of entire sites. Thanks to remote controllability, operators can adjust filter characteristics centrally, reducing operating costs and massively increasing resilience against new interference sources.

Monoplexer / Diplexer / Duplexer / Triplexer

Combining multiple GLONASS bands or separating GNSS signals from other services on a shared antenna requires high-performance multiplexers with extremely high isolation. Our triplexers for GNSS applications enable the simultaneous use of different frequency bands with minimal mutual interference. Wainwright Instruments manufactures these components with a focus on minimal group delay distortion so as not to impair positioning accuracy. Precise tuning prevents signal crosstalk and protects sensitive receiver paths in compact multi-frequency systems from overloading by external radiation. Our multiplexers are optimized for use in professional navigation systems and industrial infrastructure applications.

Absorptive Filters

Absorptive filters play a crucial role in the transmission infrastructure of GLONASS simulators and test transmitters to preserve signal purity. Rather than conducting unwanted harmonics or reflections back to the generator, these filters safely convert them into heat, preventing signal distortion. This is particularly important for complying with strict regulatory masks for test transmitters in the 1.2 GHz to 1.6 GHz range. Our absorptive filters are designed for continuous operation and increase simulation precision by consistently minimizing thermal stress and signal reflections.