A single-chip CMOS IF-band converter design for DVB-T receivers
Introduction
The function of a DVB-T (terrestrial digital video broadcasting) receiver analog front end is to convert an input signal from the radio frequency (RF) tuner into a bit stream for following OFDM (orthogonal frequency division multiplexing) demodulation processing. The analog front end circuitry consists of an RF tuner, a down-conversion mixer, an automatic gain controller (AGC), an anti-aliasing filter (AAF), and an analog to digital converter (ADC), as shown in Fig. 1. The RF tuner selects a desired channel and converts the received signal into a 36 MHz intermediate frequency (IF) signal. The down-conversion mixer then converts the 36 MHz IF signal into a 4.5 MHz baseband signal. The AGC block is used to ensure that the amplitude of the received signal is kept in a constant level which is large enough for the following circuitry. The digital variable gain amplifier (DVGA) possesses a 70 dB dynamic tuning range with a 0.3 dB gain error and 95 MHz bandwidth. The AAF is used to remove the adjacent-channel coupled noise generated by the mixer to avoid inter-channel interferences and then passes the desired signal to the ADC [1]. The proposed IFC integrates all of the down-conversion mixer, the AGC, and the AAF into a single chip. Physical measurements on silicon justify the performance of our design with conversion , .
Section snippets
Down-conversion mixer
There are three basic active mixers using the concept of balancing: unbalanced mixer, single balanced mixer, and double balanced mixer. The unbalanced mixer has a problem that the frequency components at the RF input will appear at the output. It is called RF feedthrough. Similarly, the frequency components at the local oscillator frequency input will also propagate through in the single balanced mixer designs. It is called local oscillation feedthrough. Neither RF feedthrough nor local
Simulation
In order to verify the performance of the proposed IFC, TSMC (Taiwan Semiconductor Manufacturing Company) 2P4M CMOS process is adopted to carry out the proposed design. Table 1 summarizes the specifications of the proposed IFC.
Conclusion
We have proposed a CMOS single-chip IF-band converter for DVB-T receivers. The proposed IFC converts a 36 MHz IF input into a 4.5 MHz baseband signal. The down-conversion mixer adopts the current folded-mirror architecture to provide a superior performance in conversion gain and linearity. The AGC based on a DVGA composed of a plurality of gain blocks and a fully differential degeneration amplifier. The gain tuning required by DVB-T receivers can be carried out by digital signals selecting proper
Acknowledgments
This research was partially supported by National Science Council under Grant NSC94-2213-E-110-022 and NSC94-2213-E-110-024. Furthermore, the authors would like to express their deepest gratefulness to CIC (Chip Implementation Center) of NAPL (National Applied Research Laboratories), Taiwan, for their thoughtful chip fabrication service. The authors also like to thank “Aim for Top University Plan” project of NSYSU and MOE, Taiwan, for partially supporting this investigation.
References (13)
- M. Massel, Digital Television, DVB-T COFDM and ATSC 8-VSB, 〈digitalTVbooks.com〉 Hong Kong,...
VLSI for Wireless Communication
(2002)- et al.
CMOS Circuit Design, Layout, and Simulation
(1998) - W.-C. Cheng, C.-F. Chan, C.-S. Choy, K.-P. Pun, A 1.5V 900MHz CMOS current folded-mirror mixer, in: Proceedings of the...
- et al.
Digitally programmable decibel-linear CMOS VGA for low-power mixed-signal applications
IEEE Trans. Circuits Sys. II: Analog Digital Signal Process.
(2000) - M. Mostafa, H. Elwan, A. Bellaour, B. Kramer, S.H.K. Embabi, A 110MHz 70dB CMOS variable gain amplifier, in: 1999 IEEE...
Cited by (1)
Characterization of a Gm-C Filter Based on CNTFETs for Use in Digital Audio Broadcasting Systems
2019, Journal of Electronic Materials