Do you wake up every day feeling too tired, or even upset? If so, then a new alarm clock could be just for you. The clock, called SleepSmart, measures your sleep cycle, and waits1you to be in your lightest phase of sleep2rousing you. Its makers say that should3you wake up feeling refreshed every morning. 　　As you sleep you pass4a sequence of sleep states—light sleep, deep sleep and REM(rapid eye movement) sleep—that5approximately every 90 minutes. The point in that cycle at which you wake can6how you feel later, and may7have a greater impact than how much or little you have slept. Being roused during a light phase8you are more likely to wake up energetic. 　　SleepSmart9the distinct pattern of brain waves10during each phase of sleep, via a headband equipped11electrodes(电极)and a microprocessor. This measures the electrical activity of the wearer’s brain, in much the12way as some machines used for medical and research 13, and communicates wirelessly with a clock unit near the bed. You14the clock with the latest time at15you want to be wakened, and it16duly(适时地)wakes you during the last light sleep phase before that. 　　The17was invented by a group of students at Brown University in Rhode Island18a friend complained of waking up tired and performing poorly on a test. “19sleep-deprived people ourselves, we started thinking of20to do about it,” says Eric Shashoua, a recent college graduate and now chief executive officer of Axon Sleep Research Laboratories, a company created by the students to develop their idea.