什么是匹配滤波器？对于与矩形包络调制信号相匹配的滤波器的实现方法有哪些？它们各有什么
题型：问答题 简答题
问题：
什么是匹配滤波器？对于与矩形包络调制信号相匹配的滤波器的实现方法有哪些？它们各有什么特点？
题型：问答题 简答题
Some people say, “Extreme(极限的) sports are so dangerous. Why would anyone want to do them?” But the danger is what makes them so excited. Keep reading to find out the most popular ones.
Bungee jumping: People on some South Pacific islands have been bungee jumping for hundreds of years. In 1979, some people bungee jumped off a bridge in England and made the sport popular around the world. Bungee jumping came to China in 1996.
Skateboarding: At first, this sport was called “sidewalk surfing”. Skateboarders often jump high into the air, go down steps or slide(滑行) down rails on their boards. They wear baggy trousers(宽松裤) so they can move more freely.
Skydiving: This is probably the scariest(最惊险的) extreme sport. Skydivers jump out of airplanes about four kilometers up in the sky. They usually free-fall for a while and then open a parachute to slow down for a safe landing.
Snowboarding: This became a winter Olympic sport in 1998. People tie their feet to the board with special shoes. They don’t use any ski sticks. Then, they ride down hills, jump high and do tricks.
小题1:What made bungee jumping popular all over the world?
A．A history of hundreds of years.
B．Jumping over a river in England.
C．Coming to China in 1996.
D．Jumping off a bridge in Britain.小题2:In which sport do people jump from a plane?
A．Bungee jumping.
B．Skydiving.
C．Skateboarding.
D．Snowboarding.小题3:Why do people wear “baggy trousers”?
A．They have many bags on them.
B．They can hold many things.
C．They make people move freely.
D．People wearing them can move fast.小题4:What’s the meaning of the underlined word “parachute”?
A．直升飞机
B．降落伞
C．滑板
D．飞艇小题5:Why do some people like to do the extreme sports?
A．It’s dangerous but exciting.
B．It’s exciting and safe.
C．It’s scary but safe.
D．It’s easy to learn.