问题 问答题 简答题

鉴相器的作用及其组成是什么?

答案

参考答案:

鉴相器是一个相位比较电路,输入信号(基准)和VOC输出信号在鉴相器内进行相位比较,而输出一个代表二者相位差的误差电压(直流),经过环路滤波器(直流放大积分低通滤波)得到的无干扰直流误差电压UAPC去控制压控振荡器VCO,使压控振荡VCO的输出频率朝着减小两信号频率和相位误差的方向变化,终始VCO输出=基准信号频率,无频率差,只有剩余相位差(静态)。VCO输出是经过提纯的高S/N的信号,鉴相器由于平衡变压器,二极管,电阻电容组成,均称鉴相二极管,电阻,电容,变压器等,同时有隔直的电容和积分电路等组成。

选择题
单项选择题

After the terrorist attacks in America last September, terrorist risk became the pariah of perils. The airline industry was most directly affected by the attacks, and it was the first to find that no one wanted to insure terrorist risk. Insurance companies immediately increased premiums and cut cover for airlines’ third-party terror and war liabilities to $ 50m per airline, per "event". Under pressure from airlines, the American government and the members of the European Union agreed to become insurers of last resort for airlines’ war and terrorist liabilities, for a limited period. These government guarantees are due to expire at the end of the month.

The American government has already agreed to extend its guarantee for another 60 days. The EU’s transport ministers are meeting next week in Brussels to decide what to do. Insurers and reinsurers are keen for the commercial market to resume the provision of all airline insurance as soon as possible. No wonder: The premiums for such cover have inevitably increased considerably.

However, in the case of terrorism, and especially of terrorism in the skies, a number of special factors arise. Some are purely practical: a disaster as sudden and unforeseen as the attacks on the World Trade Center has had destructive effects on the insurance industry. The maximum cover for third-party terrorist risk available in the primary aviation market is now $ 50m, and that is not nearly enough cover risks that are perceived to be much higher since September 11th. Even if the market could offer sufficient cover, another catastrophe on such a scale would be more than the market could cope with.

In addition, a rare and devastating risk of a political nature is arguably one that it is right for governments to cover, at least in part. In the wake of attacks by Irish terrorists the British government has recognized this point by agreeing to back a mutual fund to cover risks to property from terrorist attack.

In the case of the airlines, the appropriate answer is some form of mutual scheme with government backing. In fact, under the code-name "Equitime", representatives of airlines, insurers and the American government are setting up an insurance vehicle to be financed by airlines and reinsured by the government. Governments would guarantee the fund’s excess. risk, but their role would diminish as the fund grew.

Setting something up will take time. So, to bridge the gap, governments will have to remain insurer of last resort for airlines’ war and terrorist risk for some time to come.

The word "vehicle" (Para. 5) denotes()

A. vulnerability

B. capability

C. liability

D. availability