第8ç« +æ•°å­—ä¿¡å&mid

第8ç« +æ•°å­—ä¿¡å&mid

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信息传输与处理实验室 蒋铃鸽 2. 2FSK 信号的功谱与带宽 c.2FSK 带宽 10 2( ) 22 1 T b BRff RF R T = +− + Δ = ± 定义频偏 1 () 2 F ff Δ− ± 选择载频 1 2 c f =+ 采用带限 Nyquist 设计 1 ) T BF R α = Δ+ + 带宽
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信息传输与处理实验室 蒋铃鸽 (b). 相位连续 FSK 2 f fK ω π Δ 为频偏系数 b(t) 双极基带数字序列作为调制信号 , 载波为 cos ω c t. 0 () cos ( ) t FSK c stA t b d ωτ τ =+ Δ 瞬时相位 0 t c tt b t d t θωω Δ {} ( ) 1 , 1 ib i i bt agt iT a = −∈ + 瞬时角频率 0 ( ) t c cc i b i dt d b d θ ωω ⎡⎤ == + Δ ⎢⎥ ⎣⎦ Δ = + Δ
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信息传输与处理实验室 蒋铃鸽 8.2.2 2FSK 信号的解调 (1) 相干解调 判决 0 cos t ω t=T LPF LPF MF 0 1 () rt 1 cos t 0 T V = + 222 10 00 1 2 TT Es t d ts t d t A T === ∫∫ 0 T V = 2 0 sin( ) sin( ) 1 cos cos ()() T At t d t E ωω ρω + == = + −+ / nT ωπ −= / mT + = 两信号正交 , 一般取①成立 , 0 ρ = 2 11 22 24 e E AT P erfc erfc NN ⎡⎤ ⎢⎥ ⎣⎦ 1 + ± : cos s tA t s t = = 0 tT 相位已知 , 最佳 接收为相关接收
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信息传输与处理实验室 蒋铃鸽 (2) 非相干解调 00 0 :( ) ( )( ) c o s ( ) Hr t s t n t A t n t ω θ = += + + 判决 t=T 包络 检波器 MF 0 1 () rt 0 T V = 1 R 0 R + 22 2 0 11 exp exp 24 e A AT P N σ ⎛⎞ =− ⎜⎟ ⎝⎠ ⎝⎠ 0 1 exp E N ⎝⎠ 相位未知 , 佳为正交接收 1 0 cos ( ) ( ) st A t t =+ 0 tT 1 ) ( ) c o s ( ) t s t n tA t n t = + + 10 R R 1 H > 0 H < 0
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信息传输与处理实验室 蒋铃鸽 8-2 () 18 61 8 0 5 55 22 1 0 0 2 2V 105dB 21 0 / 1 11 02 2 1 0 / 105dB 1.78 10 2 /1.78 10 1.124 10 ( ) (1.124) 10 4 FSK WH z s FSK FSK Ts N W H z AV AT N μ −− × == × × × = × ×× = 设有一 系统,发送信号峰值电压为 ,信道损耗
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第8ç« +æ•°å­—ä¿¡å&mid

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