2020年经济学人 无人送货机的防护(2)

Adding threat-detection measures, such as heavy, power-hungry radar¹ antennae², or spinning lidar units,

增加威胁探测措施，如重型耗电的雷达天线或旋转激光雷达装置

radar's optical equivalent, would either reduce range or prevent lift-off in the first place.

（雷达的光学等效装置）可以在一开始就减少投掷射程或防止投掷。

Dr Roy and Mr Garg think, however, that they have hit on a low-power, lightweight self-defence system suitable for small drones.

但Roy博士和Garg博士认为他们发现了一种适用于小型无人机的低功率、轻型自卫系统。

Instead of employing light or radio waves to detect incoming threats, it harnesses sound waves and the Doppler effect.

无需光波和无线电波，它可以利用声波和多普勒效应来探测威胁来袭。

The Doppler effect is the frequency shift heard as a source of sound approaches or recedes³.

多普勒效应是当声源靠近或后退时听到的频率偏移。

It is, for example, the reason the pitch of a police siren changes as a patrol car passes in the street.

例如，这就是警车在街上经过时警笛声改变的原因。

To take advantage of it Dr Roy and Mr Garg plan to fit drones with diminutive⁴ loudspeakers, like those found in smartphones.

Roy博士和Garg博士计划利用这一点给无人机装上小型扬声器，就像智能手机上的那样。

These would broadcast an ultrasonic⁵ tone outward from the drone.

它们会从无人机向外发射超声波。

Similarly tiny microphones would then listen for reflections from incoming objects.

类似的，小型麦克风会听取来自临近物体的反射。

The Doppler shift of these reflections, run through a bit of on-board processing

这些反射的多普勒频移，经过一些机载处理

(but far less than that needed for radar or lidar) would give the bearing of the threat, and thus permit the drone to take evasive action.

（但远远少于雷达或激光雷达所需的处理），就能确定威胁的方位，从而使无人机采取规避行动。

To test the principle of what they call their DopplerDodge drone defence system,

为了测试他们的DopplerDodge无人机防御系统，

Dr Roy and Mr Garg have constructed a static version in their laboratory,

Roy博士和Garg博士在他们的实验室里构建了一个静态版本，

and have been throwing objects of various sizes and shapes at it, as if it were a hovering⁶ drone.

并向它投掷各种大小和形状的物体，就好像它是一个在空中盘旋的无人机。

At the moment, it can detect these objects from distances of up to four metres away.

目前，它可以探测到4米以外的物体。

That is pretty close, but would still give a drone a tenth of a second's notice of an incoming missile.

这个距离很近，但是仍然可以给无人机十分之一秒的时间来注意临近的投掷。

This would be sufficient for it to move itself out of the way.

这足以让无人机避开。

Tests on actual drones will take place shortly, and then, if all goes as planned,

不久将进行无人机的实际测试，如果一切按计划进行，

the two researchers will attempt to extend the system's range to 30 metres—a reasonable approximation of a stone's throw.

两位研究人员将尝试将系统的射程扩大到30米——一个接近扔石头的合理距离。

1 radar   

n.雷达，无线电探测器

参考例句：

• They are following the flight of an aircraft by radar.他们正在用雷达追踪一架飞机的飞行。
• Enemy ships were detected on the radar.敌舰的影像已显现在雷达上。

2 antennae   

n.天线；触角

参考例句：

• Sometimes a creature uses a pair of antennae to swim.有时某些动物使用其一对触须来游泳。
• Cuba's government said that Cubans found watching American television on clandestine antennae would face three years in jail.古巴政府说那些用秘密天线收看美国电视的古巴人将面临三年监禁。

3 recedes   

v.逐渐远离( recede的第三人称单数 )；向后倾斜；自原处后退或避开别人的注视；尤指问题

参考例句：

• For this reason the near point gradually recedes as one grows older. 由于这个原因，随着人渐渐变老，近点便逐渐后退。 来自辞典例句
• Silent, mournful, abandoned, broken, Czechoslovakia recedes into the darkness. 缄默的、悲哀的、被抛弃的、支离破碎的捷克斯洛伐克，已在黑暗之中。 来自辞典例句

4 diminutive   

adj.小巧可爱的，小的

参考例句：

• Despite its diminutive size,the car is quite comfortable.尽管这辆车很小，但相当舒服。
• She has diminutive hands for an adult.作为一个成年人，她的手显得非常小。

5 ultrasonic   

adj.超声的；n.超声波

参考例句：

• It was very necessary for people to take type-B ultrasonic inspection regularly.定期进行B超检查是十分必要的。
• Sounds are classified into two kinds: sonic and ultrasonic.声波分为两类，即普通声波与超声波。

6 hovering   

鸟( hover的现在分词 )； 靠近（某事物）； （人）徘徊； 犹豫

参考例句：

• The helicopter was hovering about 100 metres above the pad. 直升机在离发射台一百米的上空盘旋。
• I'm hovering between the concert and the play tonight. 我犹豫不决今晚是听音乐会还是看戏。