RF Introduction

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  • Basic RF terminology

    Transmitter (only TX)Receiver (only RX)

    Transceiver (both TX & RX)SoC (Transceiver + MCU)dBm – is a measure of RF Power referred to 1 mW (0 dBm)
    ……………10mW(10dBm), 500 mW (27dBm)

    PER – Packet Error Rate [%] – percentage of the packets not successfully received over a period of time
    ……………Used to measure the RF transceiver performance

    BER – Bit Error Rate [%] – percentage of the Bits not successfully received over a period of time
    ……………Used to measure the RF transceiver performance

    Sensitivity (RX) – it is the lowest input power of the receiver acceptable to receive packets with 1% PER

    Blocking (RX) – The receiver ability to work in the presence of a interfering RF signal in a frequency band relatively close to the signal of interest

    Dynamic range – the maximum received power variation at the receiver input pins which result in a correct demodulated signal

    Adjacent Channels – channel(s) closest to the active signal channel

    Alternate Channel – second next channel(s) to the active signal channel

    Payload – application data

    Modulation – superimposing algorithm of a low frequency signal (payload) onto a high frequency signal (Carrier) – ASK, OOK, FSK, GFSK, GMSK

    Crystal – Clocks the Radio IC crystal oscillator which generates the reference frequency for the RF synthesizer

    Balun converts balanced (differential) signal to unbalanced (single-ended) signal and the vice versa.

    Matching network – whenever a source of power with a fixed output impedance such as a radio transmitter operates into a load, the maximum possible power is delivered to the load when the impedance of the load is equal to the complex conjugate of the impedance of the source

    Filter attenuates out of band signals

    Antenna switching – Either can be used to switch from antenna to antenna with a better RSSI value, or is switching the antenna either to the RX to TX chain between the antenna and the radio IC

    Range Extender – can be used to increase the radiated output power

    Antenna – converts electric power into radio waves

    Signal encoder/decoder – converts information from one format or code to another, for the purposes of standardization, speed, security or saving space by shrinking size (e.g. Manchester), decoder does the opposite

    Modulator – process of varying one or more properties (amplitude, frequency, ..) of a high-frequency periodic waveform, called the carrier wave, with a modulating signal which typically contains information to be transmitted (Application Data)

    Communication channel – is the physical transmission medium as a wire or, as in our case, a radio channel

    Demodulator/Detector – Recovers the information content from the modulated carrier wave

Digital Amplitude modulation methods

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