Home         Authors   Papers   Year of conference   Themes   Organizations        To MES conference

Digital recursive generator of the samples of chirp
Authors
	Lesnikov V.A.
	Chastikov A.V.
	Garsh D.G.
	Naumovich T.V.
Date of publication
	2016
Abstract
	It is proposed the recursive generator of complex samples of the linear chirp. The generator is characterized by minimum possible memory size and the minimum time of tuning. Linear chirp signals are widely used in radar, sonar, communication applications, oblique ionospheric sounding, digital imaging, test equipment, harmonic coding of speech, etc. The coherent forming of signal is needed in many of these applications. Forming of such signals it is expedient to carry out based on calculation of values of samples of these signals. Computation of samples of the chirp signal may be required when implementing the Bluestein Chirp-z transform, the Chirplet Transform. The numerically controlled oscillator (NCO) carries out calculation of the signal samples. One of the first realization of the numerically controlled linear chirp oscillator (NCLCO) has been based on preliminary calculation of the signal samples and store them in high-speed memory [3]. In [4] the approach to coherent sweep generation based on the calculation of the binary words, corresponding to the analytical expression for the quadratic phase of a sampled linear sweep is offered. In [6], [7] the approach based on recursive computation of a quadratic phase of the chirp is offered [5]. All considered methods assume use of a table memory. It significantly reduces flexibility of the former. Change of parameters requires considerable time. Proposed in this paper a recursive technique of forming of the complex samples of the chirp eliminates these disadvantages. Applied recursive technique is based on the ideas described in [8]-[10]. The NCLCO consists of two units. The first unit generates a harmonic complex signal. The parameters of the signal are determined by a complex constant and initial conditions. The second unit generates samples of a complex chirp. The first unit may be represented as the first order complex IIR digital filter with zero initial conditions. The pole of the transfer function of this filer is on the unit circumference in the z-plane. Thus, the first block is the unstable filter with constant coefficients. The second unit is also the first order unstable complex IIR digital filter. But coefficients of this filter change in each step. If to define concept of an instantaneous pole, then it moves on a unit circumference in each step. This paper proposes the recursive digital coherent generator of complex samples of linear chirp. The generator is characterized by the minimum amount of memory and the possibility of quick adjustment of any parameters. The authors obtained a decision on granting a patent of the Russian Federation [11].
Keywords
	sampling; linear chirp; numerically controlled oscillator; direct digital synthesis; recursive algorithm.
Library reference
	Lesnikov V.A., Chastikov A.V., Garsh D.G., Naumovich T.V. Digital recursive generator of the samples of chirp // Problems of Perspective Micro- and Nanoelectronic Systems Development - 2016. Proceedings / edited by A. Stempkovsky, Moscow, IPPM RAS, 2016. Part 1. P. 224-229.
URL of paper
	http://www.mes-conference.ru/data/year2016/pdf/D060.pdf