应用背景 FIR(fini te impulse response)滤波器是数字信号处理系统中最基本的元件,它可以在保证任意幅频特性的同时具有严格的线性相频特性,同时其单位冲激响应是有限的,没有输入到输出的反馈,系统稳定。因此,FIR滤波器在通信、图像处理、模式识别等领域都有着广泛的应用。关键技术在进入FIR滤波器前,首先要将信号通过A/D器件进行模数转换,使之成为8bit的数字信号,一般可用速度较高的逐次逼进式A/D转换器,不论采用乘累加方法还是分布式算法设计FIR滤波器,滤波器输出的数据都是一串序列,要使它能直观地反应出来,还需经过数模转换,因此由FPGA构成的FIR滤波器的输出须外接D/A模块。
SHOW FULL COLUMNS FROM `jrk_downrecords` [ RunTime:0.003816s ]
SELECT `a`.`aid`,`a`.`title`,`a`.`create_time`,`m`.`username` FROM `jrk_downrecords` `a` INNER JOIN `jrk_member` `m` ON `a`.`uid`=`m`.`id` WHERE `a`.`status` = 1 GROUP BY `a`.`aid` ORDER BY `a`.`create_time` DESC LIMIT 10 [ RunTime:0.106564s ]
SHOW FULL COLUMNS FROM `jrk_tagrecords` [ RunTime:0.001470s ]
SELECT * FROM `jrk_tagrecords` WHERE `status` = 1 ORDER BY `num` DESC LIMIT 20 [ RunTime:0.002249s ]
SHOW FULL COLUMNS FROM `jrk_member` [ RunTime:0.001539s ]
SELECT `id`,`username`,`userhead`,`usertime` FROM `jrk_member` WHERE `status` = 1 ORDER BY `usertime` DESC LIMIT 10 [ RunTime:0.005816s ]
SHOW FULL COLUMNS FROM `jrk_searchrecords` [ RunTime:0.001325s ]
SELECT * FROM `jrk_searchrecords` WHERE `status` = 1 ORDER BY `num` DESC LIMIT 5 [ RunTime:0.007578s ]
SELECT aid,title,count(aid) as c FROM `jrk_downrecords` GROUP BY `aid` ORDER BY `c` DESC LIMIT 10 [ RunTime:0.023696s ]
SHOW FULL COLUMNS FROM `jrk_articles` [ RunTime:0.001306s ]
UPDATE `jrk_articles` SET `hits` = 2 WHERE `id` = 215990 [ RunTime:0.013375s ]