INTRODUCTION Data conversion is a broad area of activity that involves both theory and implementation. Our goal in this article is to provide a focused treatment of key fundamentals and an in-depth study of the latest approaches available for data converter design in communication systems. The coverage provided here should allow the reader to plan the design of a data converter integrated circuit or begin an independent investigation of the field. Since the early 1990s, the transceiver core shown in Fig.

Hence the bandwidth and slewing requirements for the folder is n times the maximum allowable input frequency. Therefore, folding with a high folding factor is not effective at high operating frequencies. Another drawback of the folding is substantial nonlinearity in the folder waveform. Comparing the ideal dotted waveform and the actual waveform in Fig. 18, it can be seen that the output of the folder is grossly inaccurate toward the peaks Vmax and Vmin. The effect is similar to residue errors in a two-step converter or a pipelined converter which cause integral nonlinearity or differential nonlinearity.

For simplicity we assume throughout this article that the signal band begins at DC, where signals are restricted to the frequency range [0, fb]. Sampling rates for bandlimited analog signals must exceed the Nyquist rate, denoted by 2fb, as shown in Fig. 5. Rf _ OUT + Figure 2. A binary-weighted N-bit Nyquist-rate D/A. Switching elements control current flow through the buffer based on bit values. The analog output voltage is expressed as Ài vout ¼ Vref SN i ¼ 1 2 bi , where Vref ¼ 2IRf. b1 b2 bN I I /2 I /2 −VEE −VEE −VEE N elements (current sources) N −1 A/D AND D/A CONVERSION ARCHITECTURES AND TECHNIQUES sample-and-hold or resampler analog/digital input amplitude quantization sampling operation vout ¼ Vref 2Ài bi ð2Þ i¼1 where bi are the bits of the input word, {b1, b2,y,bN}, which may be in either signed or unsigned digital form; b1 denotes the most significant bit (MSB); and bN, the least significant bit (LSB).