Design Of CMOS RF Circuits For A Zero-IF Transmitter

In modern society, wireless communication becomes more and more important to our lives and work, and wireless communication facilities such as mobile phones and personal digital assistant becomes ordinary in daily lives. Wireless-local-area-network (WLAN) technology is a reliable and convenient way to provide instant, flexible and constant data rate network access, and it can almost offer connections for any place. From one point of view, any network that connects information equipments via wireless medium in an area coverage can be called WLAN. This definition covers various types of standard, which can be classified into two orientation: one mainly for high speed application IEEE802.11,IEEE802.11a/b/g and the other for low speed and short distance application such as Bluetooth,HomeRF and HiperLAN. Form another point of view, WLAN points to networks that follow IEEE802.11 standard. This standard has already become the standard of industry in fact.In addition, the development of CMOS technology makes integrating the whole RF front-end on a single chip possible.An RF transmitter performs modulation, up conversion and power amplification.The RF front-end circuits integrated on a single chip used for wireless communication are researched in this dissertation, as well as a direct-up-conversion(zero-medium-frequency) transmitter is designed. The transmitter adopts IEEE802.11b standard for WLAN, and is applied in a long-distance medical treatment, carrying out the voice transmission between the patient and the doctor. IEEE802.11b standard specified operation in the2.4GHz band (also known as the ISM band) and could achieve speeds up to 11Mbps. Choosing 802.11b is not only for the voice transmission, but also for multi-medium transmission in the future. And 802.11b can also realize long transmission distance as well.The transmitter consists of two low-pass-filter, two variable gain amplifier, two mixer, and a divider on the chip, and a filter as well as a power amplifier off chip. Simulations are carried on for each block to meet the requirement, and the low-pass-filter (which utilizes 4th order Butterworth active RC configuration) and the divider (which adopts flip-flop-based structure) are taped out with UMC18 CMOS RF/Mixed_mode technology. Of course, the system realized the transmitting function. The low-pass-filter and the divider are tested at last.