射頻系統(tǒng)介紹ppt課件(完整版)
【正文】 harmonic distortion (dBc) 20dBc 2nd HMD 3rd HMD 4w1 中華大學(xué) 通訊系 40 High power RF transmitter ? Determine the OP1dB: – QPSK: OP1dB= Output power spec. + 3dB – OFDM: OP1dB= Output power spec. + 6dB ? Fix PA loading impedance – Fixed transistor output load line – sustain the OP1dB – Reduce the distortion and EVM ? Reduce input nonlinear admittance 中華大學(xué) 通訊系 41 AM to AM and AM to PM Conversion I Q BER will increase due to magnitude and phase migrations of the IQ constellation when amplifier’s gain is pressed. AM/PM AM/PM AM/AM AM/AM 中華大學(xué) 通訊系 42 Spectrum regrowth frequency Lower Adjacent Channel Upper Adjacent Channel Carrier Channel Caused by IM3 AM/AM AM/PM 。1 Introduction of Radio Frequency Systems 中華大學(xué) 通訊系 田慶誠 中華大學(xué) 通訊系 2 Outline ? Analog radio munication system ? Digital wireless munication system ? Radio Frequency transceiver ? RF receiver specifications ? RF transmitter specifications ? High power RF transmitter 中華大學(xué) 通訊系 3 Analog radio munication system ? Amplitude modulation – Homodyne receiver – Heterodyne receiver 外差式接收機(jī) ? Frequency modulation – Super heterodyne receiver 超外差式接收機(jī) 中華大學(xué) 通訊系 4 Amplitude modulation receiver ? Homodyne receiver 1906 Forest 真空管 1906 Fessenden 調(diào)幅 AM廣播 1912 Armstrong 再生檢波收音機(jī) Wider RF filter bandwidth Bad noise immunity Demodulation 解調(diào) AM 576 KHz AF 100~2KHz 中華大學(xué) 通訊系 5 Amplitude modulation receiver ? Heterodyne receiver Narrow IF filter bandwidth Good noise immunity Demodulation 解調(diào) AM 1413 kHz AF 100~2KHz LO 958 kHz IF 455 kHz Better Sensitivity 中華大學(xué) 通訊系 6 Frequency modulation receiver ? Super heterodyne receiver 1918 Armstrong 超外差收音機(jī)
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