Satellite Frequency Bands

最新推荐文章于 2024-12-28 10:51:54 发布
转载 最新推荐文章于 2024-12-28 10:51:54 发布 · 639 阅读 · 1 ·
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原文链接：http://www.marinesatellitesystems.com/index.php?page_id=101

本文详细介绍了卫星通信中使用的L-Band、C-Band、Ku-Band和Ka-Band等频段的特点与应用。从频率范围、带宽、设备要求、应用场景等方面对比分析，揭示了各频段的优势与限制。
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There is not much L-Band bandwidth available. The higher you go in frequency, the more bandwidth is available, but the equipment needs to be more sophisticated.
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If one could equate the cost and availability of L-Band space segment to say, city real estate, C-Band might be the suburbs, Ku band the countryside, and Ka-Band the prairies of the wild west. Maybe a little more difficult to get to, but a lot of it available at a reasonable price.
L-Band (1-2 GHz) | C-Band (4-8 GHz) | Ku-Band (12-18 GHz) | Ka-Band (26.5-40 GHz)

L-Band (1-2 GHz)

Being a relatively low frequency, L-band is easier to process, requiring less sophisticated and less expensive RF equipment, and due to a wider beam width, the pointing accuracy of the antenna does not have to be as accurate as the higher bands.
Only a small portion (1.3-1.7GHz) of L-Band is allocated to satellite communications on Inmarsat （国际海事卫星组织）. Inmarsat uses L-band for their Fleet Broadband, Inmarsat-B and C.
The older Inmarsat A and B antennas were typically 1 meter in diameter, but, with the launch of more powerful satellites and the use of steerable spot beams, the new Fleet broadband antennas are down to less than 30cm (12 inches).
L-Band is also used for low earth orbit satellites, military satellites, and terrestrial wireless connections like GSM mobile phones. It is also used as an intermediate frequency for satellite TV where the Ku or Ka band signals are down-converted to L-Band at the antenna LNB, to make it easier to transport from the antenna to the below deck, or indoor equipment.
Since there is not much bandwidth available in L-band, it is a costly commodity.

C-Band (4-8 GHz)

Satellite C-band usually transmits around 6 GHz and receives around 4 GHz. It uses large (2.4- 3.7 meter) antennas. These are the large white domes that you see on top of the cruise ships and commercial vessels.
C-band is typically used by large ships that traverse the oceans on a regular basis and require uninterrupted, dedicated, always on connectivity as they move from region to region. The shipping lines usually lease segment of satellite bandwidth that is provided to the ships on a full time basis, providing connections to the Internet, the public telephone networks, and data back-hauls to their head office.
C-band is also used for terrestrial microwave links, which can present a problem when vessels come into port and interfere with critical terrestrial links. This has resulted in serious restrictions within 300Km of the coast, requiring terminals to be turned off when coming close to land.

Ku-Band (12-18 GHz)

Ku-Band (pronounced Kay-You) refers to the lower portion of the K-Band. The “u” comes from a German term referring to “under” whereas the “a” in Ka- Band refers to “above” or the top part of K-Band. The middle portion of K-Band is a bit of a mystery. Other than a mention of K-Band radar there are few references on the Internet to it’s use.
Ku-Band is most commonly used for satellite TV and is used for most VSAT systems on yachts and ships today. There is much more bandwidth available in Ku -Band and it is therefore less expensive that C or L-band.
The main disadvantage of Ku-Band is rain fade. The wavelength of rain drops coincides with the wavelength of Ku-Band causing the signal to be attenuated during rain showers. This can be overcome by transmitting extra power but this of course comes with a cost as well.
The pointing accuracy of the antennas need to be much tighter than L-Band Inmarsat terminals, due to narrower beam widths, and consequently the terminals need to be more precise and more expensive.
Ku band coverage is generally by regional spot beams, covering major land areas with TV reception. VSAT Vessels moving from region to region need to change satellite beams, sometimes with no coverage in between beams. Lately this process has been improved with a transatlantic beam on Telstar 11n, and the satellite terminals and modems being programmed to automatically switch beams.
VSAT Antenna sizes typically range from the standard 1 meter, like the SeaTel 4009, to 1.5 meters for operation in fringe areas and, more recently, as low as 60cm for spread spectrum operation.

Ka-Band (26.5-40 GHz)

Ka-Band (pronounced Kay-A) is an extremely high frequency requiring great pointing accuracy and sophisticated RF equipment. Like Ku-band it is susceptible to rain fade. It is commonly used for high definition satellite TV. It is also used today for terrestrial VSAT services from companies like Hughes Networks.
Ka-Band bandwidth is plentiful and once implemented should be quite inexpensive compared to Ku-Band .
In 2010 there is news that Inmarsat will be providing a global Ka-Band VSAT service beginning in 2014. As more Ka-Band bandwidth becomes available, there will be several other satellite providers offering Ka-Band VSAT on a more regional basis.
The advantage of the Inmarsat solution is that it will be global, seamless, much smaller antennas, and should be much cheaper that Ku-Band services today. If priced correctly, this could revolutionize the marine VSAT industry. It will be difficult for smaller companies to compete with the expected $1.4M investment that Inmarsat is making in it’s I5 satellites.

http://www.marinesatellitesystems.com/index.php?page_id=101

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#define _CRT_SECURE_NO_WARNINGS #include <stdio.h> #include <stdlib.h> #include <string.h> #include <ctype.h> #include <math.h> #define MAXRINEX 1024 #define MAX_SATELLITES 200 // 卫星结构体 typedef struct { char prn[10]; // 卫星PRN号 (G01, C01, E01等) char system; // 系统标识 (G, C, E) double freq1_north, freq1_east, freq1_up; // 频率1的PCO double freq2_north, freq2_east, freq2_up; // 频率2的PCO int freq1_found; // 频率1是否找到 int freq2_found; // 频率2是否找到 } SatellitePCO; // 时间结构体 typedef struct { int year, month, day, hour, min; double sec; } DateTime; // 全局变量 SatellitePCO satellites[MAX_SATELLITES]; int sat_count = 0; DateTime start_time = { 2024, 6, 7, 2, 0, 0.0 }; // 开始时间: 2024-06-07 02:00:00 DateTime end_time = { 2024, 6, 7, 6, 0, 0.0 }; // 结束时间: 2024-06-07 06:00:00 // 安全的字符串拷贝函数 void safe_strcpy(char* dest, const char* src, size_t dest_size) { if (dest_size > 0) { strncpy(dest, src, dest_size - 1); dest[dest_size - 1] = '\0'; } } // 去除字符串首尾空格 char* trim(char* str) { if (!str) return str; char* end; // 跳过前导空格 while (isspace((unsigned char)*str)) str++; if (*str == 0) return str; // 去除尾部空格 end = str + strlen(str) - 1; while (end > str && isspace((unsigned char)*end)) end--; end[1] = '\0'; return str; } // 解析时间字符串 int parse_time(const char* line, DateTime* time) { if (!line || !time) return 0; return sscanf(line, "%d %d %d %d %d %lf", &time->year, &time->month, &time->day, &time->hour, &time->min, &time->sec); } // 比较时间 int compare_time(const DateTime* t1, const DateTime* t2) { if (!t1 || !t2) return 0; if (t1->year != t2->year) return t1->year - t2->year; if (t1->month != t2->month) return t1->month - t2->month; if (t1->day != t2->day) return t1->day - t2->day; if (t1->hour != t2->hour) return t1->hour - t2->hour; if (t1->min != t2->min) return t1->min - t2->min; if (t1->sec < t2->sec) return -1; if (t1->sec > t2->sec) return 1; return 0; } // 判断时间是否在有效期内 int is_time_valid(const DateTime* valid_from, const DateTime* valid_until, int has_valid_until) { // 检查开始时间是否在有效期内 if (compare_time(valid_from, &start_time) > 0) { return 0; // 有效开始时间晚于我们的开始时间 } // 如果有结束时间，检查结束时间是否在有效期内 if (has_valid_until) { if (compare_time(valid_until, &end_time) < 0) { return 0; // 有效结束时间早于我们的结束时间 } } // 如果没有结束时间，只要开始时间早于我们的开始时间就认为有效 // 因为这意味着该记录从valid_from开始一直有效到现在 return 1; // 时间有效 } // 查找卫星索引 int find_satellite(const char* prn) { if (!prn) return -1; for (int i = 0; i < sat_count; i++) { if (strcmp(satellites[i].prn, prn) == 0) { return i; } } return -1; } // 添加新卫星 int add_satellite(const char* prn, char system) { if (sat_count >= MAX_SATELLITES) return -1; if (!prn) return -1; safe_strcpy(satellites[sat_count].prn, prn, sizeof(satellites[sat_count].prn)); satellites[sat_count].system = system; satellites[sat_count].freq1_found = 0; satellites[sat_count].freq2_found = 0; satellites[sat_count].freq1_north = 0.0; satellites[sat_count].freq1_east = 0.0; satellites[sat_count].freq1_up = 0.0; satellites[sat_count].freq2_north = 0.0; satellites[sat_count].freq2_east = 0.0; satellites[sat_count].freq2_up = 0.0; return sat_count++; } // 解析PCO值 int parse_pco(const char* line, double* north, double* east, double* up) { if (!line || !north || !east || !up) return 0; return sscanf(line, "%lf %lf %lf", north, east, up); } // 获取频率标识 void get_frequency_bands(char system, char* freq1, char* freq2, size_t buf_size) { if (!freq1 || !freq2 || buf_size == 0) return; if (system == 'G') { // GPS safe_strcpy(freq1, "G01", buf_size); safe_strcpy(freq2, "G02", buf_size); } else if (system == 'C') { // BDS safe_strcpy(freq1, "C01", buf_size); // B1I (L1) safe_strcpy(freq2, "C06", buf_size); // B3I (L6) } else if (system == 'E') { // Galileo safe_strcpy(freq1, "E01", buf_size); // E1 (L1) safe_strcpy(freq2, "E05", buf_size); // E5a (L5) } else { freq1[0] = '\0'; freq2[0] = '\0'; } } // 计算无电离层组合系数 void calculate_ionofree_coeff(char system, double* alpha, double* beta) { if (!alpha || !beta) return; double f1, f2; if (system == 'G') { // GPS f1 = 1575.42; // L1 (MHz) f2 = 1227.60; // L2 (MHz) } else if (system == 'C') { // BDS f1 = 1575.42; // B1I (MHz) f2 = 1268.52; // B3I (MHz) } else if (system == 'E') { // Galileo f1 = 1575.42; // E1 (MHz) f2 = 1176.45; // E5a (MHz) } else { *alpha = *beta = 0.0; return; } double f1_sq = f1 * f1; double f2_sq = f2 * f2; double denom = f1_sq - f2_sq; if (fabs(denom) < 1e-9) { *alpha = *beta = 0.0; return; } *alpha = f1_sq / denom; *beta = -f2_sq / denom; } // 处理ATX文件 void process_atx_file(const char* input_file, const char* output_file) { if (!input_file || !output_file) { printf("无效的文件路径!\n"); return; } FILE* fp_in = fopen(input_file, "r"); FILE* fp_out = fopen(output_file, "w"); if (!fp_in) { printf("无法打开输入文件: %s\n", input_file); return; } if (!fp_out) { printf("无法创建输出文件: %s\n", output_file); fclose(fp_in); return; } char line[MAXRINEX]; int in_antenna_block = 0; int valid_satellite = 0; char current_prn[20] = ""; char current_system = '\0'; DateTime valid_from, valid_until; int has_valid_until = 0; char current_freq[10] = ""; // 写入输出文件头 fprintf(fp_out, "PRN 系统 北方向PCO1 东方向PCO1 天顶方向PCO1 北方向PCO2 东方向PCO2 天顶方向PCO2 北方向IFC 东方向IFC 天顶方向IFC\n"); fprintf(fp_out, " (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm) (mm)\n"); fprintf(fp_out, "时间段: 2024-06-07 02:00:00 至 2024-06-07 06:00:00\n\n"); // 跳过文件头 while (fgets(line, sizeof(line), fp_in)) { if (strstr(line + 60, "END OF HEADER")) break; } // 处理天线数据块 while (fgets(line, sizeof(line), fp_in)) { if (strstr(line + 60, "START OF ANTENNA")) { in_antenna_block = 1; valid_satellite = 0; current_prn[0] = '\0'; current_system = '\0'; has_valid_until = 0; continue; } if (strstr(line + 60, "END OF ANTENNA")) { in_antenna_block = 0; continue; } if (!in_antenna_block) continue; // 解析TYPE / SERIAL NO行 if (strstr(line + 60, "TYPE / SERIAL NO")) { char type[50], serial[50], cospar[50]; if (sscanf(line, "%49s %49s %49s", type, serial, cospar) == 3) { safe_strcpy(current_prn, serial, sizeof(current_prn)); current_system = serial[0]; // 只处理G、C、E系统 if (current_system == 'G' || current_system == 'C' || current_system == 'E') { valid_satellite = 1; } else { valid_satellite = 0; } } continue; } // 解析VALID FROM行 if (strstr(line + 60, "VALID FROM")) { if (parse_time(line, &valid_from) == 6) { // 检查时间有效性 if (!is_time_valid(&valid_from, &valid_until, has_valid_until)) { valid_satellite = 0; } } else { valid_satellite = 0; } continue; } // 解析VALID UNTIL行 if (strstr(line + 60, "VALID UNTIL")) { if (parse_time(line, &valid_until) == 6) { has_valid_until = 1; 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例如，全球定位系统 (GPS) 运营商以及卫星移动电话，如 Iridium和 Inmarsat提供海上、陆地和空中通信。R18 38.101-5 NTN FR1 band 分别为n256/255/254，可以看到对应的是卫星L频段和S频段，传输带宽和信道带宽规定如上。X波段(8–12 GHz)：主要用于军事通信、气象卫星和地球观测卫星。C波段(4–8 GHz)：常用于固定卫星通信服务，如卫星电视广播和数据传输。V波段(40-75 GHz)：用于高速数据传输、宽带多媒体服务和地球观测卫星。
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