Generating precision nonlinear FM chirp waveforms

Nonlinear swept frequency technique for CO2 measurements using a CW laser system

“…The use of nonlinear sweeps for use in sidelobe suppression is a well-known technique from radar [20][21][22][23]. Although the use of data windows can also reduce sidelobes, it usually results in a loss of signal to noise.…”

Some Aspects of Sidelobe Reduction in Pulse Compression Radars Using NLFM Signal Processing

“…According to [11], the frequency modulation law of a temporal predistortioned FM signal can be generally written as follows ( Figure 1):…”

“…For these values and signal base (denoted next by BT ) of 40 and 80, a decreasing of the sidelobes assigned to the compression-weighting (Hamming) filter responses from −29.3 dB to −34.7 dB and from −35.5 dB to −38.4 dB, respectively, were achieved. According to [11], more appropriate values for predistortioning function parameters are ∆t = 1/∆F and ∆f = 0.55 • ∆F (in this case, as optimization criterion, the local behavior of the sidelobe level was effective used etc. )…”

“…The primary idea of Cook and Bernfeld is extended in [11] to the nonlinear predistortioning case. In other words, some examples of nonlinear predistortioning functions are given in [11].…”

“…Generally, all these processing techniques can be divided into two major research directions, namely: a) designing of pseudo-NLFM (or piecewise) waveforms which are in fact, LM signals predistortioned on short intervals (e.g., at the pulse ends) into temporal domain or corrected into spectral domain [1,[8][9][10]; b) designing of proper (e.g., as desired shape of the energy/power spectral density (E/PSD) etc.) pure (continuous) NLFM waveforms using usually, iterative methods [11][12][13], stationary phase principle [14][15][16], Zak transform [17,18], suitable weighting/convolutional functions [19][20][21][22], explicit functions cluster algorithm [23,24] or marginal Fisher's information-based techniques [25] etc. Also, many of the above described NLFM methods are implemented by standard computational algorithms, but some interesting approaches connected with the artificial intelligence (AI) paradigms are also discussed in literature [26][27][28].…”