IQ Calibration


IQ Calibration

Section: A 0.13um CMOS 6-9GHz 9-Bands Double-Carrier OFDM Transceiver for Ultra Wideband Applications Lesson: IQ calibration Novel Applications of the UWB Technologies. This course is brought to you by Gilad James Mystery School. Learn more at Gilad James.com. Introduction Since 2002, ultra wideband (UWB) technology has ignited the interests of academia and industry for its potential of achieving high-speed wireless communication in short distance with low power. It is actively investigated today due to the wide available bandwidth for very high data rate up to 480Mb/s and low power service over short distances in 10m range. According to FCC (Federal Communications Commission), the frequency spectrum allocated for UWB is 3.1-10.6 GHz, and the spectrum shape of modulated output power and maximum power level are limited to -41.3dBm/MHz, which ensures that UWB can coexist with existing spectrum users like GSM(Global System of Mobile communication), WLAN(Wireless Local Area Network) and Bluetooth. Based on MB-OFDM(Multi-Band Orthogonal Frequency Division Multiplexing), WiMedia released the initial version of Physical Layer (PHY) Specification in September 2005. In this proposal, the UWB frequency spectrum from 3.1 GHz to 10.6 GHz is divided into 14 channels with 528MHz for each channel. These sub-bands are grouped into five band groups. It is seen that by increasing the signal bandwidth significantly, ultra-wideband achieves a high channel capacity and becomes an attractive solution to the ever-increasing data rate demands in wireless personal area networks (WPAN). In December 2005, European Computer Manufacturer’s Association (ECMA) proposed the standard ECMA 368/369 on high-speed UWB physics layer and media access control layer based on MB-OFDM scheme. This has pushed the industrialization of UWB technology to a new stage again. In China, UWB technology has also become a hot topic according to the issue of the UWB standard by Chinese Government in 2008. A new UWB scheme named dual carrier-orthogonal frequency division multiplexing (DC-OFDM ) has been proposed and applied in China. In China standard, only the band from 6.2GHz to 9.4GHz and the band from 4.2GHz to 4.8GHz are available for UWB applications. These bands are partitioned into 14 sub-bands of 264MHz bandwidth which means the bandwidth is halved in China’s DC-OFDM standard compared with the ECMA 368/369 standard. Thus the sampling frequency of the DACs(Digital-to-Analog Converter) and ADCs(Analog-to-Digital Converter) are halved too. The power consumption of the system can be reduced greatly. Moreover, in DC-OFDM UWB, two bands locating around two different carriers are utilized at the same time to form a bandwidth of 528 MHz for maintaining high-speed communication. In this way, the spectrum usage is more flexible and the spectrum efficiency is enhanced. However, the requirements of less than 9-ns hopping time of the carrier frequency as well as simultaneous dual-carrier outputs challenge the design of dual-carrier frequency synthesizer. Fig.1 shows the frequency spectrum for WiMedia and China UWB standard. A fully integrated transceiver for DC-OFDM UWB system in the 6-9GHz band is present in this lecture. This lecture will describe the realization of a DC-OFDM UWB transceiver covering 6-9GHz bands in a low cost 0.13um CMOS process. Firstly, the RF receiver design will be described in section 2. Section 3 and 4 introduce respectively the designs of the RF transmitter and the 9-bands frequency synthesizer. The detailed measurement results are demonstrated in section 5, which is followed by the conclusions in section 6.
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