Satellite Navigation / QZSS

QZSS: Technology and Filter Requirements

QZSS (Quasi-Zenith Satellite System), also known as "Michibiki", is a Japanese satellite-based augmentation system specifically designed to enhance the availability and accuracy of GPS signals in the deep urban canyons of Japanese metropolitan areas. Technologically, the system operates in the frequency bands L1 (1,575.42 MHz), L2 (1,227.60 MHz), L5 (1,176.45 MHz), and the specific L6 band (1,278.75 MHz), which is utilized for the Centimeter Level Augmentation Service (CLAS). The unique feature is its quasi-zenith orbit, which ensures that at least one satellite is always directly overhead Japan to minimize shading effects caused by high-rise buildings. RF hardware in QZSS environments faces the challenge of receiving extremely weak signals in an environment with massive spectral density. Proximity to high-power 5G base stations (n78) and terrestrial Small Cells operating in the 3.5 GHz to 4.5 GHz range can saturate high-sensitivity navigation front-end components. Wainwright Instruments manufactures specialized high-performance filters designed to ensure excellent selectivity in the L-band while providing extremely high out-of-band rejection. This is essential to preserve the integrity of the correction data in the L6 band, which is indispensable for autonomous driving and precision industrial robotics.

Typical Deployment Scenarios

In professional navigation environments, QZSS filters function as critical barriers against interference to fully exploit the benefits of high-precision Japanese satellite architecture.

Autonomous Driving in Urban Centers: In the urban canyons of Tokyo or Osaka, our filters secure receivers in Massive MIMO-controlled autonomous vehicles by eliminating interference from local ITS infrastructure.
Disaster Warning Systems: QZSS transmits critical messages during earthquakes or tsunamis; here, our filter solutions guarantee absolutely fail-safe signal detection, even when terrestrial infrastructure is burdened by high emergency radio traffic.
Precision Agriculture & Drones: For centimeter-accurate control of agricultural machinery in rural Japan, our components protect the L5 and L6 signals from overloading caused by neighboring LTE-M or NB-IoT transmitters.
Critical Time Referencing (Timing): In base stations for 5G networks, our filters protect GNSS timing antennas from the extreme transmit power of their own Remote Radio Units (RRUs) at the same mast.
Maritime Safety & Surveying: In Japanese coastal waters, our robust filters protect receiver front-ends from saturation by powerful on-board S-band and X-band radar systems.
Industrial Automation (Smart Factory): In automated warehouses, our filters support AGV navigation by stabilizing signal purity against electromagnetic pulses from heavy-duty machinery.
Geodesy & Infrastructure Monitoring: For reference stations monitoring bridges or dams, we supply filters with minimal thermal drift to ensure the millimeter accuracy of long-term measurements.
Test and Certification Laboratories: For validating new navigation components, we supply high-precision reference filters to characterize hardware behavior under extreme coexistence conditions in the lab.

Suitable Filter Categories for Satellite Navigation / QZSS

High signal bandwidth requirements of QZSS, particularly for the CLAS service, demand filter solutions with superior selectivity and group delay stability.

Band Pass Filters

Our QZSS Band Pass filters enable precise selection of L1, L2, L5, and L6 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 for weak satellite signals 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 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 QZSS hardware in laboratory environments, we offer manually tunable Band Pass filters covering the range from 1,100 MHz to 1,700 MHz. Via high-precision mechanical tuning elements, the passband can be adjusted exactly to specific channels or experimental frequency ranges. This flexibility allows engineers to investigate the robustness of their receiver designs against targeted broadband interference or coexistence with neighboring GNSS services in the lab. The robust construction of our manually tunable filters guarantees permanent reproducibility of measurement results during demanding stress tests.

Digitally Tunable Band Pass Filters

Electronically controllable filters support modern SDR-based navigation architectures 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, supporting efficient quality assurance processes in manufacturing.

Band Reject Filters / Notch Filters

Our QZSS notch filters serve to eliminate specific strong interfering signals located immediately adjacent to or within the utilized spectrum, such as terrestrial radio systems in the 1.2 GHz range. They feature extremely deep stopband attenuation while the rest of the passband remains nearly unaffected. This protection is fundamental to prevent saturation of high-sensitivity receiver front-ends in urban environments with a high density of Small Cells. By using our notch filters, the robustness of the infrastructure against narrowband interferers is massively increased, increasing the availability of precision positioning.

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 or ITS nodes. 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 even under strong vibrations and temperature fluctuations.

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 landings or autonomous transport fleets. Their integration into automation concepts for radio optimization allows for autonomous radio optimization of entire test areas. 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 QZSS bands or separating GNSS signals from other services on a shared antenna requires high-performance multiplexers with extremely high isolation. Our duplexers and triplexers 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 across the entire spectrum from L1 to L6 so as not to impair positioning accuracy. Precise tuning prevents signal crosstalk and protects sensitive receiver paths 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 QZSS simulators and ground stations 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. Our absorptive filters are designed for continuous operation and increase simulation precision by consistently minimizing thermal stress and signal reflections while optimizing the signal-to-noise ratio.