原创 SMA connector

1. SMA连接器的主要技术指标如下：
温度范围：Temp.range -65～+165°C (PE Cable -40～+85°C)
振 动：Vibration MIL-STD-202,Method 213
特性阻抗：Impedance 50Ω
频率范围：Frequency Range DC～12.4GHz(半刚电缆 0～18GHz)
工作电压：Working Voltage 335V max (有效值)
耐 压：Withstand Voltage 1000V rms (海平面最小值)
接触电阻：Contact resistance
内导体之间：Center Contact ≤ 3 mΩ
外导体之间：Outer Contact ≤ 2 mΩ
绝缘电阻：Insulation resistance ≥ 5000 MΩ
插入损耗：Insertion loss ≤0.15 dB/6GHz
电压驻波比： VSWR 　直式:Straight 软电缆 ≤1.10+0.002f 半刚电缆 ≤1.05+0.001f
　　　　　　　　　　　弯式 Right angle 软电缆 ≤1.20+0.003f 半刚电缆 ≤1.10+0.001f
耐用性：Durability(mating) ≥500次（cycles）


2. 材料与涂覆 MATERIAL & PLATING
壳体 shell 黄铜 brass 镀硬金 gold plated
插针 contact pin 黄铜 brass 镀硬金 gold plated
插孔 socket 铍青铜 beryllium 镀硬金 gold plated
弹性接触件elastic contact 铍青铜 beryllium 镀硬金 gold plated
绝缘体 insulator 聚四氟乙烯 PTFE
压接套 crimp ferrule 铜合金 copper alloy 镀镍或镀金 nickel or gold plated
o型密封件o-ring sealing 硅橡胶6146 silastic


3.SMA连接器适用技术标准 APPLICABLE STANDARD
MIL-C-39012;
CECC 22110;
IEC 60169-15.
（待续：SMA连接器layout guide）

4. SMA connector layout guide

At the SMA-connector end, the via comes back up to the surface layer. The general rule is to keep the   balanced transmission line intact as long as possible to maintain matching. Another major rule, which designers often overlook, is the impedance matching of the SMA connector to the PCB. Although the SMA connector itself is matched to 50ohm, the landing pad on the PCB for the SMA connector is not. Unless you make special provisions, the performance of the board deteriorates at frequencies greater than 1 GHz. With the SMA connectors that the ADC10D1000 reference design uses, the SMA landing pad is about four times wider than a 50? trace. For a 50? match, the associated ground plane is Layer 7. You must remove the metal on layers 2 through 6.

  Figure 6 The general rule is to keep the balanced transmission line intact as long as possible to maintain matching. You must remove the green ground layer underneath the SMA landing pad, Layer 2, because it would form a large capacitor with the landing pad. This board has no conducting material under the SMA landing pad until Layer 7. Layer 7 must be an ac ground for proper impedance matching.

 总结：虽然SMA connector本身的阻抗是50Ohm,但是要确保SMA与PCB相连的PAD的阻抗也是50ohm，就需要将SMA参考到更底层的ground plane. 也就是说，要将下面的底层挖空，且走线加粗。具体的参数需要仿真来确定。