关于biquad

biquad是双二阶，这种结构的双二是什么意思?传输函数分子分母都是二阶的?
Biquad Switched Capacitor Filter呢?

找到这样的一个相关内容：MAX261是美国MAXIM公司推出的CMOS双二阶通用开关电容有源滤波器，其内部含有两个二阶滤波单元。

so biquad的意思就是两个二阶的意思么?美信的biquad filter有一个经典结构，难不成这个biquad就只是指这个（种）特定结构么?

想不明白了啊，求大神指教一下

google也上不去，坑爹，度娘啥都不知道

biquad is also called bi-linear, basically in the frequency response, the denominator is second order while and numerator can be as high as 2nd order.

thaks，

In signal processing, a digital biquad filter is a second-order recursive linear filter, containing two poles and two zeros. "Biquad" is an abbreviation of "biquadratic", which refers to the fact that in the Z domain, its transfer function is the ratio of two quadratic functions

thanks for your sharing