Take DFT of the sampled data of each subpulse
, and obtain its frequency domain data firstly.
where [w.sub.n] is the complex weight of the nth subcarrier, satisfying [mathematical expression not reproducible] is the mth element of the sequence which modulates the nth subcarrier, u(t) is the gate function, [t.sub.b] is subpulse
width, [f.sub.n] = n x [DELTA]f is the nth subcarrier, [DELTA]f = 1/[t.sub.b] is frequency space, [N.sub.c] is the number of subcarriers, and M is the number of OFDM symbols.
SFCS is composed of a burst of narrow-band subpulse
chirp signals with their carrier frequencies increased/decreased linearly or nonlinearly [1-4].
The laboratory device enables the current pulse to be split into 2 ms subpulses
. Each subpulse
may be applied to a different electrode or electrode set pair with desired polarity.
At the outset of its development program, the manufacturer established a stability goal of 65 dB in a radar subpulse
bandwidth of 333 kHz.
where [[theta].sub.l] is the downlooking angle of the center line of lth subswath, [f.sub.c] is the carrier frequency, [lambda] = c/[f.sub.c] is the wavelength, [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] is the delay time of the lth subpulse
, t = [t.sub.k]+m[T.sub.r] is the whole time, [t.sub.k] is the fast time, m is a integer, [T.sub.r] is pulse repetition interval, and [gamma] is the chirp rate.
where [[tau].sup.R.sub.nq] and [[tau].sup.F.sub.nq] are the rise instant and the fall instant normalized with respect to the modulation period [T.sub.p] of the qth subpulse
related to nth waveform, respectively (q = 1, ...
Modulation parameters set special values M = 3 and K = N/2; MPPSK pulse waveforms corresponding to nonzero symbols, that is, "1" to "2", are subdivided into a number of subpulses
each of duration [KT.sub.1], where [NT.sub.1] is the pulse width and 2 is the number of subpulses
Under certain conditions, the central region of the pulse passes through the PBS losslessly, and the rejected pulse consists of the leading and trailing edges of the intracavity pulse, which can be regarded as two subpulses
. In , we gave a detailed report on this phenomenon.
A burst is composed of many brief subpulses
, perhaps from individual shock waves inside a turbulent jet.
In the first mode, two subpulses
are transmitted in turn with different azimuth antenna beams by switching the phase coefficients in the transmit modules, and echoes of the two subpulses
are simultaneously received by the main lobe and the first grating lobe of the whole antenna and recorded in a single channel.
The nadir energy could be seriously reduced by analog beamforming (ABF) on transmit in elevation with null steering as shown in Figure 4(a), and broad nulls could be used to reduce the temporal overlap at receivers due to echoes from different subswaths corresponding to different subpulses
as shown in Figure 4(b).