GNSS Full-Band Signal Splitter Selection: Analysis of Measured Data for 1-to-4 Port Gain Optimization

Driven by the completion of the BeiDou-3 global network and the modernization of GPS, the scale of China's high-precision positioning market exceeded 28 billion yuan in 2025. However, in multi-system and multi-frequency signal distribution scenarios, engineers often face tricky problems such as gain imbalance, poor phase consistency, and insufficient port-to-port isolation. How should a 1-to-4 port GNSS full-band signal splitter be selected to achieve optimal gain? Based on measured data, this article breaks down key performance indicators and selection decision paths.

GNSS Full-Band Signal Splitter Technical Background and Core Parameters

As the "signal hub" of satellite navigation systems, the performance of the GNSS full-band signal splitter directly determines the upper limit of accuracy for multi-receiver synchronous deployment. Current mainstream devices must simultaneously cover full-band signals such as BeiDou B1I/B1C/B2a/B3I, GPS L1/L2/L5, GLONASS G1/G2, and Galileo E1/E5a/E5b, with a frequency span ranging from 1164MHz to 1610MHz.

Full-Band Coverage and System Compatibility Requirements

Full-band coverage is not a simple superposition of frequencies, but a comprehensive test of in-band flatness and group delay consistency. Actual measurements show that when the in-band fluctuation exceeds ±1.5dB, the joint multi-frequency calculation accuracy will drop by more than 30%. Models like 32-0165B-01 must support compatible reception of the BeiDou-3 global signal structure and GPS modernized signals, ensuring that the center frequency deviation of B1C/L1C/E1 frequency points is controlled within ±5MHz.

Typical Application Scenarios for 1-to-4 Port Architecture

The 1-to-4 port architecture offers cost advantages in scenarios such as surveying and mapping reference stations, intelligent driving test fields, and UAV swarm control. Compared with 1-to-8 or 1-to-16 solutions, this architecture strikes a balance between port count and insertion loss—the theoretical distribution loss is 6dB, while actual high-quality products can control it within 7dB. A typical configuration includes: reference station master antenna → splitter → 4 receivers for synchronous observation, achieving millimeter-level baseline resolution.

Analysis of Measured Data for Key Gain Optimization Indicators

Gain optimization is the core goal of GNSS full-band signal splitter selection. Measured data shows that different brands of products differ significantly in gain flatness indicators, which directly affects the initialization time and fix rate of RTK fixed solutions.

Port Gain Flatness and Frequency Response Curves

The frequency response curve is an intuitive basis for evaluating gain flatness. The full-band gain fluctuation of high-quality products should be controlled within ±0.5dB, and the attenuation at edge frequency points (1164MHz, 1610MHz) should not exceed 1.2 times that of the center frequency point. Actual measurement comparison shows that the 32-0165B-01 model using the Wilkinson power division structure has 12% better gain stability at the B2a/L5 frequency point (1176.45MHz) than the branch-line coupling solution.

Impact of Phase Consistency on RTK Positioning Accuracy

Phase consistency is a key indicator for multi-receiver synchronous observation. When the phase difference between the 4 ports exceeds 5°, systematic errors will be introduced into the double-difference observations, degrading the baseline resolution accuracy from millimeter-level to centimeter-level. Actual measurements verify that in short baseline (<10km) RTK applications, a splitter with phase consistency better than ±3° can shorten the fixed solution initialization time by 40% and increase the fix rate to over 98%.

1分4端口隔离度与噪声系数实测对比

Port-to-port isolation and noise figure are often overlooked but crucial hidden indicators that directly determine the anti-interference capability and receiving sensitivity when multiple receivers work in parallel.

Port-to-Port Isolation and Multipath Suppression Capability

Insufficient port isolation will lead to signal crosstalk, forming equivalent multipath effects. Standards require adjacent port isolation to be ≥20dB and opposite port isolation to be ≥25dB. Measured data shows that the splitter using a microstrip-coaxial hybrid structure can achieve more than 28dB opposite isolation in the 1.2GHz–1.6GHz band, which is an improvement of 6–8dB compared to traditional pure microstrip structures, significantly improving multipath suppression performance in urban canyon environments.

Correlation Analysis Between Noise Figure and Receiver Sensitivity

The noise figure characterizes the additional noise introduced by the splitter, and the typical value should be <3dB. It is worth noting that noise figure and gain are not independent—a high-gain front-end can compensate for distribution loss, but it will compress the receiver's dynamic range. Practical recommendation: when used with a low-noise amplifier (LNA), control the splitter's noise figure within 2.5dB, and the total system noise figure can be optimized to below 3.5dB, meeting the -160dBm weak signal acquisition requirement.

Selection Decision Framework and Engineering Implementation Key Points

Establishing a quantitative selection framework is an effective way to avoid "empiricism" traps. It is recommended that engineers build an evaluation system from three dimensions: link budget, environmental adaptability, and supply chain security.

Gain Budget Calculation and Link Loss Matching

A complete link budget needs to coordinate antenna gain, cable loss, splitter insertion loss, and receiver noise figure. Typical reference station configuration example: antenna gain +5dBic → 50m cable -4dB → splitter -7.2dB → receiver, net gain -6.2dB, which is within the receiver's optimal input window (-10dBm to -30dBm) within. If the link loss exceeds the limit, an LNA module must be integrated at the front end of the splitter.

Domestic Substitution and Supply Chain Security Considerations

At present, domestic GNSS full-band signal splitters have achieved benchmark substitution for imported products in core indicators. When selecting, attention should be paid to: the completeness of the S-parameter test report, the temperature drift coefficient (gain variation <±1dB in the range of -40℃ to +85℃), and MTBF reliability data. It is recommended to prioritize suppliers with BeiDou navigation product certification qualifications to ensure long-term supply stability and technical support response speed.

Measured Cases and Performance Verification in Typical Application Scenarios

Theoretical indicators must be verified by actual scenarios. The following two cases show the typical deployment modes of 1-to-4 port GNSS full-band signal splitters in high-precision positioning systems.

Synchronous Deployment of Multiple Receivers at Surveying and Mapping Reference Stations

A provincial CORS station adopted the 32-0165B-01 model to implement a 1-master 4-backup receiver architecture. Continuous observation data for 30 days showed that: the gain difference among the 4 ports was <0.4dB, the phase consistency was ±2.5°, the BDS/GPS dual-system RTK fixed solution horizontal accuracy reached ±8mm+1ppm, and the vertical accuracy was ±15mm+1ppm, meeting the millimeter-level accuracy requirements of crustal deformation monitoring. Key improvement: the integrated antenna-splitter design with stable phase center eliminates the interface loss uncertainty of traditional split schemes.

Multi-Sensor Fusion Test Platform for Intelligent Driving

In an L4 autonomous driving closed test field, a single antenna drives GNSS/INS integrated navigation, V2X roadside units, ground truth collection systems, and monitoring terminals through a 1-to-4 port splitter. The actual challenge lies in the fact that differences in the load impedance of the 4 channels lead to the deterioration of the port reflection coefficient. Solution: choose a splitter model with built-in isolation resistors to optimize the VSWR from 1.8 to below 1.3, ensuring that the local oscillator leakage of each receiver does not interfere with each other, and the multi-sensor time synchronization accuracy is better than 20ns.

Key Summary

• Gain Flatness Priority: A full-band fluctuation of ±0.5dB is the fundamental threshold for ensuring joint multi-frequency calculation accuracy, and edge frequency point attenuation requires focused attention.
• Phase Consistency Quantified: A port phase difference within ±3° can increase the RTK fix rate to over 98% and shorten the initialization time by 40%.
• Balance Between Isolation and Noise: 28dB opposite isolation combined with <2.5dB noise figure achieves dual optimization of multipath suppression and weak signal acquisition.
• Systematic Link Budget: Establish a complete gain model from the antenna to the receiver to avoid selecting a single device out of the system context.
• Scenario-Based Verification Required: Surveying and mapping reference stations and intelligent driving scenarios have differentiated requirements for phase center stability and time synchronization accuracy.

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