Zero-IF receiver has some advantages, such as small factor, low cost and easily integrated on a chip. They make it competitive of RF receivers. However, DC Offset and flicker noise, etc., have profound effects in zero-IF receiver, which need not be considered in super-heterodyne receiver. Following a major study of flicker noise, possible solutions are given, especially those based on the passive mixer. Introduction Wireless communication becomes more and more important with the tendency of personal communication. Because wireless communication becomes digital, networking, small and intelligent, radio system will be changed from analog, digital to software. Accordingly, large translation will happen to the receiver architecture. (1) The receiver may usually be realized by super-heterodyne architecture. For super-heterodyne receiver, RF modulated signal can be shifted to easily processed IF and IF modulated signal can be handled: amplification, filtration and demodulation. Particular gain control, noise figure and narrow-band selection may be realized in super-heterodyne architecture, but there are some inherent disadvantages, such as complicated architecture, difficult coordination, bulk, and large power consumption. As a result, new receiver architecture appears. There are digital IF receiver, zero-IF receiver (also called direct-conversion receiver), etc., meeting the demands of high performance, low power consumption, agility and convenience. Because zero-IF receiver is similar to software-radio receiver in many ways, this paper presents flicker noise based on zero-IF receiver. 1. Zero-IF Receiver