●●● ●●●● ●●●● 4.Noise figure ●●●● ●●●● ●●●● 1 Noise is generated by diode or transistor elements, ● thermal sources due to resistive losses. 噪声来自于二极管或晶体三极管元件，以及阻性损耗的热噪声。 2 Diode mixers generally achieve lower noise figures than transistor mixers. 二极管混频器通常可以达到比晶体三极管混频器更低的噪声系数。 3 The power of an SSB signal is one-half that of a DSB signal.单边带信号功率是双边带信号的一半。 S;INo For resistive mixers: SoINo FSSB =2FDSB FDSB(dB)=(FSSB-3)(dB) FssB≈Le 84. Noise figure ① Noise is generated by diode or transistor elements, thermal sources due to resistive losses. 噪声来自于二极管或晶体三极管元件，以及阻性损耗的热噪声。 ② Diode mixers generally achieve lower noise figures than transistor mixers. 二极管混频器通常可以达到比晶体三极管混频器更低的噪声系数。 ③ The power of an SSB signal is one-half that of a DSB signal. 单边带信号功率是双边带信号的一半。 0 0 0 / / S N S N F i  2 FSSB DSB  F ( ) ( 3)( ) FDSB SSB dB F dB   For resistive mixers: FSSB c  L 8