GPS测试 QXDM测到的卫星的CN0与看到的CN0不一致

测试GPS功能时，发现通过QXDM工具看到的modem侧的每个卫星的CN0都比手机软件上看到的要低3-3.5db，抓取实时log发现HAL层log打印出来的CN0值就与modem侧不一致。

高通给的解释是： This is by design, which has been introduced from the end of 2018. That is to day, the signal strength value (CNo) keeps the same the one in Antenna part, not baseband part. By contrast, qxdm report CNo from baseband part. The difference is the total loss from Antenna to baseband, i.e. approx. 3db ~ 3.5 db. Also, reporting antenna part signal strength could keep consistent with other vendor and Google definition

就是说天线和modem侧的CN0会有损耗，大概3.5db左右，HAL层的CN0值是从天线获取的，所以和QXDM看到的有差异。 当然也有一些手机平台比较旧，没有合入这个算法，所以看到的CN0是一致的。

android log：关键字搜索 LocSvc_LocApiBase

06-10 02:24:33.441   770  1726 V LocSvc_LocApiBase:    000:           GPS  04    0.000000    0.000000    0.000000    1575420032.000000    0x1A 0x 1
06-10 02:24:33.441   770  1726 V LocSvc_LocApiBase:    001:           GPS  07    0.000000    73.000000    272.000000    1575420032.000000    0x1B 0x 1
06-10 02:24:33.441   770  1726 V LocSvc_LocApiBase:    002:           GPS  08    0.000000    49.000000    36.000000    1575420032.000000    0x1A 0x 1
06-10 02:24:33.441   770  1726 V LocSvc_LocApiBase:    003:           GPS  09    0.000000    14.000000    215.000000    1575420032.000000    0x1A 0x 1
06-10 02:24:33.441   770  1726 V LocSvc_LocApiBase:    004:           GPS  11    0.000000    73.000000    98.000000    1575420032.000000    0x1A 0x 1
06-10 02:24:33.444   770  1726 V LocSvc_LocApiBase:    005:           GPS  13    0.000000    2.000000    323.000000    1575420032.000000    0x1A 0x 1
06-10 02:24:33.444   770  1726 V LocSvc_LocApiBase:    006:           GPS  16    0.000000    7.000000    91.000000    1575420032.000000    0x1A 0x 1
06-10 02:24:33.444   770  1726 V LocSvc_LocApiBase:    007:           GPS  17    0.000000    6.000000    234.000000    1575420032.000000    0x1A 0x 1
06-10 02:24:33.444   770  1726 V LocSvc_LocApiBase:    008:           GPS  22    0.000000    0.000000    0.000000    1575420032.000000    0x1A 0x 1
06-10 02:24:33.444   770  1726 V LocSvc_LocApiBase:    009:           GPS  27    0.000000    17.000000    47.000000    1575420032.000000    0x1A 0x 1
06-10 02:24:33.444   770  1726 V LocSvc_LocApiBase:    010:           GPS  28    0.000000    18.000000    292.000000    1575420032.000000    0x1A 0x 1
06-10 02:24:33.445   770  1726 V LocSvc_LocApiBase:    011:           GPS  30    0.000000    43.000000    309.000000    1575420032.000000    0x1B 0x 1
06-10 02:24:33.445   770  1726 V LocSvc_LocApiBase:    012:       GLONASS  74    0.000000    33.000000    116.000000    1598062464.000000    0x1A 0x10
06-10 02:24:33.445   770  1726 V LocSvc_LocApiBase:    013:       GLONASS  76    0.000000    26.000000    326.000000    1601437440.000000    0x1A 0x10
06-10 02:24:33.445   770  1726 V LocSvc_LocApiBase:    014:       GLONASS  75    0.000000    68.000000    21.000000    1602000000.000000    0x1A 0x10
06-10 02:24:33.445   770  1726 V LocSvc_LocApiBase:    015:       GLONASS  84    0.000000    14.000000    28.000000    1603124992.000000    0x1A 0x10
06-10 02:24:33.445   770  1726 V LocSvc_LocApiBase:    016:       GLONASS  85    0.000000    73.000000    33.000000    1604249984.000000    0x1A 0x10
06-10 02:24:33.445   770  1726 V LocSvc_LocApiBase:    017:        BEIDOU  201    0.000000    35.000000    126.000000    1561097984.000000    0x18 0x10000
06-10 02:24:33.445   770  1726 V LocSvc_LocApiBase:    018:        BEIDOU  202    0.000000    40.000000    217.000000    1561097984.000000    0x18 0x10000
06-10 02:24:33.445   770  1726 V LocSvc_LocApiBase:    019:        BEIDOU  203    0.000000    49.000000    175.000000    1561097984.000000    0x18 0x10000

06-10 02:24:33.445 770 1726 V LocSvc_LocApiBase: 020: BEIDOU 204 0.000000 23.000000 112.000000 1561097984.000000 0x18 0x10000 06-10 02:24:33.445 770 1726 V LocSvc_LocApiBase: 021: BEIDOU 205 0.000000 22.000000 243.000000 1561097984.000000 0x18 0x10000