1 Abstract—A quantized analog delay is designed as a requirement for the autocorrelation function in the Quadrature Downconversion Autocorrelation Receiver (QDAR) [1]. The quantized analog delay is comprised of a quantizer, multiple binary delay lines and an adder circuit. Being the foremost element, the quantizer consists of a series of comparators, each one comparing the input signal to a unique reference voltage. The comparator outputs connect to binary delay lines, which are a cascade of synchronized D-latches. The outputs available at each line are linked together to reconstruct the incoming signal using an adder circuit. For a delay time of 550 ps, simulation results in IBM’s CMOS 0.12 μm technology show that the quantized analog delay requires a total current of 36.7 mA at a 1.6 V power supply. Furthermore, delays in the range of several nanoseconds are feasible at the expense of power. After a Monte Carlo simulation it becomes evident that the response of the quantized analog delay does not suffer drastically from neither process nor component mismatch variations. Index Terms—analog delay, analog integrated circuits, quadrature downconversion autocorrelation receiver, impulse radio, quantizer, ultra-wideband I. INTRODUCTION Although impulse radio ultra-wideband technology promises enhanced data throughput with low-power consumption, it inseparably introduces several challenging design issues [2] [3] [4]. Ultra-wideband systems transmit at very low spectral densities and occupy a large amount of bandwidth, thus it is unequivocal that interference introduced from neighboring narrowband systems is a serious predicament, which could severely hamper or even degrade the overall performance of the system. In the transmit reference scheme proposed by Hoctor and Tomlinson [5] (see Fig. 1), consecutive pulses are transmitted with a predefined delay τ d between them. The first pulse acts as a reference, whereas the second pulse is modulated. The autocorrelation receiver correlates the incoming signal with a delayed version of the previous signal. The absolute value of the output after integration is in fact the S. Bagga, Lujun Zhang, Wouter A. Serdijn and John R. Long are with the Electronics Research Laboratory, Faculty of Electrical Engineering, Mathematics and Computer Science, Delft University of Technology, Mekelweg 4, 2628CD, Delft, The Netherlands (e-mail: {s.bagga, w.a.serdijn, j.r.long}@ewi.tudelft.nl). Erik B. Busking is with TNO, Defence, Security and Safety, P.O. Box 96864, 2509JG, The Hague, The Netherlands (e-mail: erik.busking@tno.nl). energy of the pulse while the polarity of the output contains the data. d τ autocorrelation function LNA ∫ ADC x τ d Fig. 1. Transmit reference scheme by Hoctor and Tomlinson A Quadrature Downconversion Autocorrelation Receiver (QDAR) (see Fig. 2) [1] is designed to operate in the presence of strong narrowband interference, while still being able to detect the incoming UWB signal. LNA x 0. 35 - 2. 4 GHz interference rejection filter - BPF x x x ∑ ∫ ADC phase shift 90 o osc I Q autocorrelation function fosc=5.05GHz τ d τ d Fig. 2. Quadrature downconversion autocorrelation receiver 10 frequency [GHz] 0 5 |S(f)| |S(f)| frequency [GHz] 0 5 LO 2.4 GHz 5 GHz Fig. 3. Frequency spectrum before (top) downconversion and after (bottom) downconversion The QDAR works on the principle of frequency wrapping or in other words, it folds the ultra-wideband frequency spectrum around the origin. At the same time, the narrowband interferers are positioned outside the band of interest and are simply removed by the means of a band-pass filter (see Fig. 3). Besides resolving the issues A Quantized Analog Delay for an ir-UWB Quadrature Downconversion Autocorrelation Receiver Sumit Bagga, Lujun Zhang, Wouter A. Serdijn, John R. Long and Erik B. Busking 328 0-7803-9398-8/05/$20.00 ©2005 IEEE