CM/L2CL) L5 I L5 Q E1 E5a (E
CM/L2CL) L5 I L5 Q E1 E5a (E5a-I/E5a-Q) E5b (E5b-I/E5b-Q) L1OF L1OC (L1OCd/L1OCp) L2OF L2OC (L2OCp) L3OC (L3OCd/L3OCp) B1I B1C B2I B2A (B2ad/B2ap) B3I Code Structure LFSR Charybdotoxin TFA Legendre sequence LFSR LFSR LFSR Memory code LFSR LFSR LFSR LFSR LFSR LFSR LFSR LFSR Legendre sequence LFSR LFSR LFSRBDS [7]L1:1575.42 MHz, L2: 1227.60 MHz, L3: 1381.05 MHz L5: 1176.45 MHz; B1:1561.098 MHz, B2: 1207.140 MHz, B3:1268.520 MHz; E1: 1575.420 MHz, E5: 1191.795 MHz.aAs the fields in the application of the GNSS have expanded along with the current development from the industries, research to provide higher precision and added functions of GNSS receivers happen to be extensively carried out [87]. Also to the basic part of getting signals and performing navigation calculations, advanced signal technologies, which include anti-jamming [8] and anti-spoofing [9], are applied, and research on multiconstellation and multi-frequency receivers [102] are getting conducted for high-precision high-reliability place calculations. In Compound 48/80 custom synthesis particular, research on single code generators that assistance numerous codes are actively performed for the implementation of multi-constellation and multi-frequency receivers to ensure that single receivers can assistance several codes [137]. As shown in Table 1, because LFSR-based code generation is the most widely applied, research on LFSR-based codes have been steadily conducted [103]. Based on 1 study [13], several LFSR-based PRN codes may be generated working with a single LFSR structure. However, there are actually not countless studies on the Legendre-based code generator structure so far. As representative Legendre-based generator structures, authors of [14,15] proposed basic code generators that use memory to store and read Legendre-based codes. The authors of [16] proposed a code generator structure exactly where Legendre sequences are generated around the fly to generate PRN codes and towards the authors of [17] proposed a Weil-generation code generator structure where Legendre sequences are stored inside the ROM and Weil sequences are generated on the fly. While preceding studies [147] succeeded in generating several Legendre-based codes using single hardware, they still use many unnecessary hardware resources to universally produce Legendre-based codes. Consequently, this paper proposes an area-efficient code generator structure exactly where a lot of Legendre sequence-based codes can be generated making use of a single universal code generator by removing redundant made use of hardware sources inside a variety where the general technique efficiency will not be degraded. The rest of this paper is organized as follows. Section 2 explains the background of Legendre sequence-based PRN codes, and Section 3 describes the preceding universal code generators. The proposed universal code generator is proposed in Section four, the experimental outcomes are discussed in Section five, plus the concluding remarks are made in Section six. two. Background To analyze the structure of code generators, it can be essential to completely fully grasp signal configuration and code construction. In this section, signal configuration and code con-Electronics 2021, 10,4 ofstruction are mathematically described to clarify the structure of code generators in the following sections. 2.1. Signal Configuration Generally, each and every satellite signal that involves Legendre-based codes contains a data channel as well as a pilot channel, as shown in Equation (1). The data channel delivers navigation messages, plus the pilot channel plays the function of facilitating signal acquisitio.
