Global Positioning System (GPS)

 

Il Global Positioning System (GPS) funziona sul principio che se si conosce la distanza da diverse località, quindi è possibile calcolare la posizione. I luoghi noti sono i 24 satelliti situati in sei piani orbitali a quota 20,2 mila chilometri. Questi satelliti intorno alla terra ogni 12 ore e trasmettono un flusso di dati alla frequenza L1 primario 1.575GHZ che porta la grossa acquisizione (C / A) segnale codificato al suolo. Il ricevitore GPS misura il tempo di arrivo del codice C / A ad una frazione di un millisecondo, e quindi determina la distanza al satellite.

The Core Subsystems include: 

  1. Front End - the GPS L1 signals (Maximum = 24 signals) at 1.575GHz are received at the antenna and amplified by the Low-Noise-Amplifier (LNA). The RF front-end further filters, mixes, and amplifies (AGC) the signal down to the IF frequency where it is digitally sampled by a ADC. ' 

  2. Baseband Processor/CPU - the ADC samples of GPS C/A code signals are correlated by the DSP and then formulated to make range measurements to the GPS satellites. The DSP is interfaced with a general-purpose CPU, which handles tracking channels and controls user interfaces. TI OMAP integrates both DSP and ARM processor on the same chip.' 

  3. Memory - the processor runs applications stored in memory. The OS is stored in non-volatile memory such as EE/FLASH/ROM. Applications may be loaded in FLASH or DRAM. ' 

  4. User Interface - allows user to input/output data from the receiver using input commands via microphone, touch screen, and output MP3 to the earplug.'

  5. Connectivity - allows the receiver to connect to the USB port.' 

  6. Power Conversion - converts input power (battery or wall plug) to run various functional blocks.