A method for constructing a frequency profile of an emitted signal used in a non-contact ranging system measuring fluid velocity and range within a flow channel, the method including at least two concurrent spectral analysis processes, each operating at a different sample rate and having a different window duration and frequency resolution, a decimation process being used to reduce the data rate between one analysis scale and the next, said method comprising: determining N stepped frequency chirps, wherein each frequency chirp of the N stepped frequency chirps has a linear FM modulation of a predetermined bandwidth and slope, and wherein a starting frequency for each of the plurality of stepped frequency chirps is chosen so that a non-linear step profile is created which extends over a predetermined total bandwidth, sorting the plurality of N stepped frequency chirps into P sub-sequences, where P is equal to the product of decimation factors to be used in the spectral analysis processes, ordering the P sub-sequences end to end in time, characterized in that each of the plurality of N stepped frequency chirps is represented only once in the P sub-sequences and each of the P sub sequences extends to at least 90% of the predetermined total bandwidth, in that the duration of emitting the P sub-sequences or a multiple of the P sub-sequences is equal to the duration of a longest duration frame in the spectral analysis processes, in that prior to sorting the plurality of N stepped frequency chirps into P sub sequences, groups of the N stepped frequency chirps are enumerated as Go through G (N-1) to define even-indexed groups of frequency chirps and odd-indexed groups of frequency chirps, one of the even-indexed groups of frequency chirps and the odd-indexed groups of frequency chirps being reordered in time to begin at an end of the other one of the even-indexed groups of frequency chirps and the odd-indexed groups of frequency chirps and in reverse order; and in that sorting the N stepped frequency chirps into P sub-sequences comprises: re-enumerating the reordered frequency chirps as Co through C (N-1); and sorting the reordered frequency chirps into P sub-sequences, wherein {sub-sequence} n = {Cn, C (n+P), C (n+2P), C (n+3P),...} n, where n = 0 to (P-1). determining N stepped frequency chirps, wherein each frequency chirp of the N stepped frequency chirps has a linear FM modulation of a predetermined bandwidth and slope, and wherein a starting frequency for each of the plurality of stepped frequency chirps is chosen so that a non-linear step profile is created which extends over a predetermined total bandwidth, sorting the plurality of N stepped frequency chirps into P sub-sequences, where P is equal to the product of decimation factors to be used in the spectral analysis processes, ordering the P sub-sequences end to end in time, characterized in that each of the plurality of N stepped frequency chirps is represented only once in the P sub-sequences and each of the P sub sequences extends to at least 90% of the predetermined total bandwidth, in that the duration of emitting the P sub-sequences or a multiple of the P sub-sequences is equal to the duration of a longest duration frame in the spectral analysis processes, in that prior to sorting the plurality of N stepped frequency chirps into P sub sequences, groups of the N stepped frequency chirps are enumerated as Go through G (N-1) to define even-indexed groups of frequency chirps and odd-indexed groups of frequency chirps, one of the even-indexed groups of frequency chirps and the odd-indexed groups of frequency chirps being reordered in time to begin at an end of the other one of the even-indexed groups of frequency chirps and the odd-indexed groups of frequency chirps and in reverse order; and in that sorting the N stepped frequency chirps into P sub-sequences comprises: re-enumerating the reordered frequency chirps as Co through C (N-1); and sorting the reordered frequency chirps into P sub-sequences, wherein {sub-sequence} n = {Cn, C (n+P), C (n+2P), C (n+3P),...} n, where n = 0 to (P-1). re-enumerating the reordered frequency chirps as Co through C (N-1); and sorting the reordered frequency chirps into P sub-sequences, wherein {sub-sequence} n = {Cn, C (n+P), C (n+2P), C (n+3P),...} n, where n = 0 to (P-1).