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QP值和PK值的区别
(2006-09-07 10:58:50)网上很多关于讨论PK和QP的区别，大部分还是说得很模糊。
峰值（PK），所表现的就是测量波形的瞬时最大值。对应的峰值检波器就要求电路的充电足够快，而放电足够慢。峰值的大小只取决于信号的幅度。
准峰值（QP），所表现的是测量信号能量的大小。由于准峰值检波器的充电时间要比放电时间快得多，因此信号的重复频率越高，得出的准峰值也就越高。（在GB9254-1998中提到过在测量接收机上所示的读数在限值附近波动时，则读数的观察时间应不少于15s，记录最高读数，而孤立的瞬间高值忽略不记。）准峰值检波器还能以线性方式对不同幅度的信号起响应。这样，准峰值既可以反映信号的幅度，也能反映出信号的时间分布。}
1）幅度大、重复频率低的信号与幅度小、重复频率高的信号可能会有相同的准峰值输出。
2）对于连续波信号，准峰值测量的结果与峰值测量的结果是一样的。
3）准峰值测量要比峰值测量慢2-3个数量级。
英文解释：
Quasi-peak
Measurements Quasi-peak detection is a form of detection where a
signal level is weighted based on the repetition frequency of the
spectral components making up the signal. That is to say; the
result of a quasi-peak measurement depends on the repetition rate
of the signal. Signals can be classified into two general
categories based upon their repetition rate: narrowband or
broadband. A narrowband signal is a signal that can be resolved by
the spectrum analyzer. An example of a narrowband signal is a
continuous wave (CW) signal. A CW signal is one signal at a fixed
frequency. A broadband signal is a signal that cannot be resolved
by the spectrum analyzer. An example of a broadband signal is a
pulse signal. Peak, quasi-peak, and average detection will yield
the same amplitude level for a narrowband signal. A broadband
signal will yield a quasi-peak level lower than the peak level. The
weighting (accounted for through specific charge and discharge time
constants in the quasi-peak detector circuit), is a function of the
repetition frequency of the signal being measured. The lower the
repetition frequency, the lower the quasi-peak level. Many agencies
governing the electromagnetic interference (EMI) from commercial
products require quasi-peak detection to be used .Even if the
emission from a device is over a test limit when measured with peak
detection, the device will be considered to pass if the quasi-peak
level is below the test limit. Because of the charge and discharge
time constants used in the quasi-peak detector , the spectrum
analyzer must sweep considerably slower when the quasi-peak
detector is on. Since the quasi-peak level of a signal is always
equal to or less than the peak level of that signal, quasi-peak
detection need be employed only when a signal is close to or over
the test limit when measured with peak detection. For initial
measurements, peak detection is used since peak detection does not
require the slower sweep
times.
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