Multicarrier Constant Envelope Composite Signal - A Solution to the Next Generation Satellite Navigation Signals

Unlike a direct broadcasting satellite navigation system, the transmitting satellite navigation system developed in China uses transponders onboard communication satellites to retransmit navigation signals generated at a ground master station. The transmitting navigation satellite constellation consists of a number of inclined geosynchronous orbit (IGSO) satellites. Considering China's mainland coverage in the northern hemisphere occupies some 62 degrees in longitude, the inclination of the IGSO satellites cannot be too high, or its signals would not be received by the users in the middle and high latitude areas when the IGSO satellite travels over the southern hemisphere. Meanwhile, the latitude of the most southerly station in China mainland that can uplink navigation signals is about 18°N when the IGSO satellite travels to the southern hemisphere. Therefore, there is a need to consider the IGSO inclination to achieve balance between uplinking high-quality navigation signals and covering the high-latitude area. In this work, the navigation performance and availability of the IGSO satellite are examined when navigation signals are uplinked from the stations Lintong and Sanya.

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A Quasi-constant Envelope Multiplexing Technique for GNSS Signals

Journal of Navigation ◽

10.1017/s0373463315000119 ◽

2015 ◽

Vol 68 (4) ◽

pp. 791-808 ◽

Cited By ~ 3

Author(s):

Tao Yan ◽

Zuping Tang ◽

Jiaolong Wei ◽

Bo Qu ◽

Zhihui Zhou

Keyword(s):

Satellite System ◽

Significant Feature ◽

Constant Envelope ◽

Modulation Techniques ◽

Combining Efficiency ◽

The First Variation ◽

Global Navigation Satellite ◽

The Second Variation ◽

Numerical Optimisation ◽

Composite Signal

A significant feature of the modernised Global Navigation Satellite System (GNSS) signals is that there are multiple signal components needing to be transmitted on a carrier frequency. How to combine these signal components into a constant envelope composite signal is a challenge. Existing constant envelope modulation techniques have some limitations, and are not effective enough. To solve this problem, we propose a quasi-constant-envelope multiplexing technique in this paper. The proposed method is based on numerical optimisation, and can work in two ways. The corresponding objective functions are provided. To verify the performance of the proposed method, we present three application examples. Results show that the first variation of our method can reach the same combining performance as Phase-Optimised Constant-Envelope Transmission (POCET). In the second variation, the combining efficiency can be pre-set. We can reach higher combining efficiency than POCET, and the envelope of the composite signal becomes quasi-constant. Furthermore, the inter-modulation signals in the final composite signal are adjustable. With the help of the proposed method, we can learn more details of the combining scheme than with POCET.

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