# 利用选择性改善接收机的截止点

### 三阶交调产生的干扰

 IIM3 = 3 × PI - 2 × IIP3 (dBm) (式1)

### 改进的三阶输入截止点(IIP3)级联方程

 √iim3 = √iim31 + √(iim32/(g1/il)) (伏特) (式2)

 IIP3 = PI + ½(PI - IIM3) (dBm) (式3)

 pI/iip3 = √(iim3/pI) (式4)

 IIP31 = P1 + ½(P1 - IIM31) (dBm) (式5)
 IIP32 = P2 + ½(P2 - IIM32) (dBm) (式6)

 IIP31 = PI + ½(PI - IIM31) (dBm) (式7)
 IIP32 = (PI + G1 - IL - S) + ½(PI + G1 - IL - S - IIM32) (dBm) (式8)

 pI/iip31 = √(iim31/pI) (式9)
 pI(g1/il)/(iip32 × s3/2) = √iim32/((g1/il)pI) (式10)

 √(iim3/pI) = √(iim31/pI) + √(iim32/(g1/il)pI (式11)

 1/iip3 = 1/iip31 + (g1/il)/(iip32 × s3/2) (式12)

 IIP3e2 = IIP32 + (3/2) × S (dBm) (式13)

 1/iip3 = 1/iip31 + (g1/(iip32 × s13/2) + (g1 × g2)/(iip33 × (s1 × s2)3/2) + ... + (g1 × g2 ... gM-1)/(iip3M × (s1 × s2 ... sM-1)3/2) (式14)

### 二阶交调产生的干扰

 IIM2 = 2 × PI - IIP2 (dBm) (式15)

### 改进的二阶输入截止点(IIP2)级联方程

 √iim2 = √iim21 + √(iim22/(g1/il)) (伏特) (式16)

 IIP2 = PI + (PI - IIM2) (dBm) (式17)

 pI/iip2 = iim2/pI (式18)

 IIP21 = P1 + (P1 - IIM21) (dBm) (式19)
 IIP22 = P2 + (P2 - IIM22) (dBm) (式20)

 IIP21 = PI + (PI - IIM21) (dBm) (式21)
 IIP22 = (PI + G1 - IL - S) + (PI + G1 - IL - S - IIM22) (dBm) (式22)

 pI/iip2I = iim2I/pI (式23)
 (pI × (g1/il))/(iip22 × S²) = iim22/(g1/il) × pI) (式24)

 √(iim2/pI) = √(iim2I/pI) + √(iim22/(g1/il) × pI) (式25)

 √(1/iip2) = √(1/iip2I) + √((g1/il)/(iip22 × s²) (式26)

 IIP2e2 = IIP22 + 2 × S (dBm) (式27)

 √(1/iip2) = √(1/iip21) + √(g1/(iip22 × s1²)) + √((g1 × g2)/(iip23 × (s1 × s2)²) + ... + √((g1 × g2 ... gM-1)/(iip2M × (s1 × s2 ... sM-1)²) (式28)

1. S. Maas, Microwave Mixers, Norwood, MA, Artech House, 1993.
2. P. Vizmuller, RF Design Guide, Norwood, MA, Artech House, 1995.