4. Radio Subsystem Features
MT3333 All-in-One GNSS
4.1. Low Noise Amplifier (LNA) and mixer
The MT3333 includes an LNA that offers devices two antenna options:
• A multi-GNSS antenna connected directly to the internal LNA in high-gain mode, ideal for low-cost
solutions without an external LNA.
• An external antenna and high gain external LNA connected to the internal LNA in low-gain mode, which
offers high linearity. In this configuration, external LNA gain ranging from 15 to 20 dB is recommended.
The maximum total external RF front end gain including active antenna and external LNA can be 43dB.
The down-conversion mixer then converts the amplified signal to the Intermediate Frequency (IF) signal. The
down-conversion mixer is a single-ended passive mixer, with a current mode interface between the mixer and
multi-modes low pass filter.
4.2. Voltage Controlled Oscillator (VCO) and synthesizer
The frequency synthesizer includes a crystal oscillator, VCO, divider, phase frequency detector (PFD), charge pump
(CP) and loop filter, which are all integrated on the MT3333 chip. The VCO is auto-calibrated to its required sub-
band when the chip is powered on.
4.3. Low Pass Filter (LPF)
The current-mode LPF provides modes for the various combinations of GNSS constellations supported by MT3333.
4.4. Analog-to-Digital Converter (ADC)
The differential IF signal is quantized by a high performance ADC. The ADC sampling clock is provided by the
divided clock from the local oscillator (LO).
4.5. Active Interference Canceller (AIC)
The AIC can detect 12 different single-tone interference signals. It can then track the phase and frequency of these
12 interference signals to provide continuous cancellation.
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