Calian GNSS-TW-3990XF-ANT - Multi Constellation Full Band Antenna (37dB)
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GNSS-TW-3990XF-ANT is a high-performance, full-band (multi-band, specifically referred to as triple-band) It is designed to cover a wide range of GNSS frequencies from multiple constellations, which is a key feature of the Accutenna technology.
Rask innføring i GNSS-antenner
GNSS står for Global Navigation Satellite System, som er en samlebetegnelse for satelittnavigasjonssystemer. Det mest kjente er GPS (Global Positioning System), men det finnes også andre, som Russlands GLONASS, Europas Galileo og Kinas BeiDou. Hvert system består av satellitter som sender ut radiosignaler, som deretter mottas av en GNSS-mottaker på bakken.
En GNSS-antenne er en spesialisert enhet som fanger opp disse svake radiosignalene. Antennens kvalitet er avgjørende for nøyaktigheten til den endelige posisjonsberegningen.
Problemet med flerveisforplantning (Multipath Interference)
Signaler fra GNSS-satellitter reiser i en rett linje til antennen. I den virkelige verden kan disse signalene imidlertid sprette tilbake fra objekter som bygninger, trær eller bakken før de når antennen. Dette skaper flerveisforplantning (multipath interference), hvor mottakeren får både det direkte signalet og ett eller flere forsinkede, reflekterte signaler. Dette er en betydelig feilkilde fordi mottakeren bruker signalets reisetid til å beregne avstand, og et reflektert signal har en lengre vei, som fører til en feil avstandsmåling og en unøyaktig posisjon.
Løsningen: Sirkulær polarisering og to-punktsmating (Dual-Feed Technology)
GNSS-satellitter sender ut signalene sine ved hjelp av en bestemt type radiobølge kalt høyresirkulær polarisering (RHCP). Tenk på det som om signalet "skrur seg" i en bestemt retning mens det reiser. Når et RHCP-signal spretter av en overflate, blir polariseringen snudd, og det blir et venstresirkulært polarisert (LHCP) signal.
Tallysmans Accutenna-teknologi utnytter dette fenomenet ved å bruke et tosidig matet antennedesign (dual-feed antenna).
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Antenne med ett matepunkt (Single-Feed Antenna): En tradisjonell antenne har kun ett punkt for å motta signalet. Selv om den er designet for å motta det ønskede RHCP-signalet, er den ikke spesielt god til å avvise de uønskede LHCP-signalene. Dette er spesielt sant når antennen opererer på frekvenser som ligger utenfor dens ideelle innstilling, noe som er vanlig i moderne GNSS-systemer som sporer flere konstellasjoner på litt forskjellige frekvenser. Denne dårlige avvisningen av reflekterte signaler fører til store posisjonsfeil.
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Antenne med to matepunkt (Dual-Feed Antenna): En Accutenna-antenne bruker en keramisk patch med to matepunkter. Ved å kombinere signalene fra disse to punktene med en spesifikk faseforskyvning (en liten forsinkelse), kan antennen oppnå en virkelig sirkulær respons over hele sitt driftsbånd. Dette betyr at den er svært følsom for de tiltenkte RHCP-signalene og svært effektiv til å avvise de uønskede LHCP-signalene. Denne overlegne avvisningen av reflekterte signaler er kjernen i teknologiens evne til å gi høy presisjon. Dokumentet understreker dette med en sammenligning av aksiale forhold, et mål på hvor "sirkulær" en antenne er. Et lavt aksialt forhold (som 1 dB for Accutenna) indikerer utmerket avvisning av kryss-polariserte signaler, mens et høyt (som 7-8 dB for en enkel matet antenne) indikerer dårlig avvisning.
Dekning for flere konstellasjoner og frekvenser
Ettersom GNSS-teknologien har utviklet seg, sporer mottakere nå signaler fra flere konstellasjoner (som GPS, GLONASS, Galileo og BeiDou) og på flere frekvenser. Tallysmans Accutenna-teknologi er designet for å håndtere denne kompleksiteten:
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Accutenna med enkel patch: Denne versjonen dekker det øvre GNSS-båndet og kan spore flere konstellasjoner (GPS L1, GLONASS G1, Galileo E1, BeiDou B1).
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Accutenna med dobbel patch: Denne mer avanserte versjonen bruker to patcher for å gi enda bredere dekning, og støtter både det øvre og nedre GNSS-båndet. Dette gjør at den kan spore signaler på flere frekvenser (f.eks. GPS L1/L2/L5, GLONASS G1/G2/G3), noe som er avgjørende for høypresisjonsapplikasjoner som Real-Time Kinematic (RTK) og Precise Point Positioning (PPP). Disse applikasjonene krever flere frekvenser for å løse posisjonsuklarheter og oppnå nøyaktighet ned til centimeter.
Evnen til å operere over et bredt frekvensområde med en konsekvent sirkulær respons er det som skiller Accutenna-teknologien, og gjør den egnet for moderne, høypresisjons GNSS-applikasjoner.
Product Description: GNSS-TW-3990XF-ANT
The GNSS-TW-3990XF-ANT is a multi-constellation, full-band antenna that leverages Calian's (formerly Tallysman) Accutenna® technology. Its name "XF" stands for "eXtended Filter," indicating it has a robust, advanced filter design to reject a broader range of out-of-band signals.
Functional Aspects
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Full-Band Coverage: It's designed to track signals from all available GNSS constellations on their primary and secondary frequencies. This includes GPS (L1/L2/L5/L6), GLONASS (G1/G2/G3), Galileo (E1/E5a/E5b/E6), and BeiDou (B1/B2/B2a/B3). It also receives L-band correction services and SBAS signals (WAAS, EGNOS, etc.)
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Superior Interference Mitigation: The "XF" filter technology is specifically designed to combat interference from a wide variety of sources, including new and emerging LTE bands (e.g., Ligado signals), Wi-Fi, and other satellite communications. This ensures clean, reliable GNSS signals even in congested RF environments.
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Precision and Accuracy: By leveraging signals from all available GNSS frequencies, the antenna provides the most robust and accurate positioning solution possible. This is crucial for applications like precision agriculture, autonomous vehicles, and RTK (Real-Time Kinematic) surveying
Technical Information
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LNA Gain: It features a high-gain Low-Noise Amplifier (LNA) with a typical gain of 37 dB
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Low Noise Figure: A very low noise figure (typically 2.5 dB) ensures a high signal-to-noise ratio, which is critical for weak satellite signals.
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Enclosure: It comes in a rugged, permanent through-hole mount enclosure with a high ingress protection rating, often IP67 or IP69K, making it durable in harsh weather conditions.
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Axial Ratio: The antenna provides an excellent axial ratio and a tightly grouped phase center variation, which is a hallmark of Accutenna® technology and leads to better signal integrity and multipath rejection.
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Design: The antenna features a precision-tuned, twin circular dual-feed, stacked patch element, with a sophisticated architecture that separates and re-combines the signals for optimal performance.
Comparison to Other Models
The GNSS-TW-3990XF-ANT is an evolution of the previous models, offering a broader and more advanced feature set.
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GNSS-TW-3872-ANT: The TW-3872 is a dual-band antenna (L1/L2) for precision positioning.The TW-3990XF is a full-band antenna, adding coverage of the L5/E5/E6/B3 bands, which are essential for true next-generation, high-precision applications and provide greater signal redundancy.The TW-3990XF also has a slightly higher gain (37 dB vs 35 dB) and more advanced filtering
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GNSS-TW-3742-ANT: The TW-3742 is a single-band (L1) antenna optimized for precision timing and is known for its very high gain (40 dB). The TW-3990XF, while having slightly less gain (37 dB), is a much more versatile and capable antenna due to its full-band coverage and advanced interference mitigation, making it suitable for a wider range of high-precision applications beyond just timing.
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GNSS-TW-3372-ANT: The TW-3372 is a single-band (L1/G1) antenna designed for cost-sensitive applications. While it offers a wider patch bandwidth for both GPS and GLONASS L1 signals, it lacks the multi-frequency capability of the TW-3990XF. The TW-3990XF is a premium, top-tier antenna in comparison, offering far more constellations and frequencies.
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GNSS-TW-3872-ESM-T: This is a product kit, not a unique antenna model. It bundles the TW-3872-ANT with a mounting bracket. The TW-3990XF would be considered the next-level, more advanced antenna model for users who are seeking the highest possible performance and multi-band capability.
Features
- Very low noise preamp (2.5 dB typ.)
- Low axial ratio (< 2.0 dB typ.)
- Tight phase centre variation
- High-gain LNA (37 dB typ.)
- Low current (32 mA typ.)
- ESD circuit protection (15 kV)
- Invariant performance from 2.5 to 16 VDC
- IP69K, CE RED, REACH, RoHS, and S-9401.V1.0 compliant
- EN45545-2, EN50121, EN50155, and EN61373 compliant
- AAR Certified
Benefits
- Ideal for full-band RTK surveying systems
- Excellent interference mitigation
- Excellent multipath rejection
- Increased system accuracy
- Excellent signal-to-noise ratio
The key difference in accuracy between single-band, dual-band, and full-band GNSS receivers lies in their ability to mitigate common sources of error, particularly ionospheric delay and multipath interference.1 Simply put, the more frequency bands a receiver can use, the more accurate and reliable its positioning becomes, especially in challenging environments.2
Single-Band GNSS
A single-band receiver uses only one frequency band, typically the L1 band (around 1575 MHz), to calculate its position.3 While single-band receivers are the most affordable and consume the least power, they have significant limitations in accuracy.
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Accuracy: Under ideal, open-sky conditions, a single-band receiver can achieve accuracy in the range of 2 to 5 meters.4
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Main Weakness: They are highly susceptible to errors caused by the atmosphere and signal reflections. The single L1 signal is easily distorted by the ionosphere and can be significantly affected by multipath interference (signals bouncing off buildings or trees).5 This makes them unreliable in urban areas, under heavy tree cover, or in other obstructed environments.6
Dual-Band GNSS
A dual-band receiver uses two frequency bands, typically the L1 and a second band like L2 or L5.7 Using two different frequencies from the same satellite allows the receiver to effectively calculate and cancel out the ionospheric delay, a major source of error.8
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Accuracy: Dual-band receivers can achieve much better accuracy, often down to 1 meter or less in open-sky conditions.9 In some high-end applications with correction services, they can even reach centimeter-level accuracy.10
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Advantages:
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Ionospheric Correction: By comparing the time difference between the L1 and L5 signals from the same satellite, the receiver can precisely measure and remove the ionospheric delay.11
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Improved Multipath Rejection: Newer signals like L5 are designed to be more robust and less susceptible to multipath, as they have higher power and wider bandwidth, making it easier to distinguish the direct signal from a reflected one.12 This significantly improves performance in urban and semi-obstructed environments.
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Full-Band GNSS (also known as Multi-Band)
A full-band or multi-band receiver is a more advanced version of a dual-band receiver. It can track and utilize three or more frequency bands (e.g., L1, L2, L5, and L6) from multiple GNSS constellations (GPS, GLONASS, Galileo, BeiDou, etc.).
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Accuracy: These receivers can achieve the highest possible level of accuracy, often at the centimeter-level when used with correction services like RTK (Real-Time Kinematic) or PPP (Precise Point Positioning).13
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Advantages:
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Maximum Signal Availability: By tracking all available frequencies from every satellite in view, a full-band receiver has a greater number of usable signals, which improves reliability and reduces the time it takes to get an accurate "fix" on its position.14
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Enhanced Redundancy: Having multiple signals from different constellations provides significant redundancy. If a signal on one frequency or from a specific satellite is blocked or interfered with, the receiver can still maintain a highly accurate position using other available signals.15
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Future-Proofing: Full-band receivers can access new and emerging GNSS signals and services, such as Galileo's High Accuracy Service (HAS), ensuring long-term compatibility and performance.
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