RF Introduction

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  • Basic RF terminology
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    • Transmitter (only TX)• Receiver (only RX)
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    • 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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