The present invention relates to a method for analyzing the properties of an incident signal. The present invention also relates to an associated analysis device and platform. In the field of very wideband passive listening of radio signals, typically between 2 GigaHertz (GHz) and 20 GHz, the aim is to obtain the simultaneous measurement of the frequency and the direction of arrival of a signal with a receiver. with direct temporal sampling not respecting the Shannon criterion, while minimizing the computational load. It is also desirable that the measurement be robust in the event of errors between the specified sample rates and the actual sample rates implemented. It is, in particular, known from the document L.-J. Ge et al., “Simultaneous Frequency and Direction Estimation from Parallel Array Data”, IEE Proc. Radar, Sonar Navig., 142 (1), pp.6-10, 1995 a method for simultaneously estimating the frequency and direction of arrival of multiple narrowband sources. Based on rotational invariance techniques, the joint estimates are calculated directly by appropriate data processing. However, the computational load remains relatively high especially with a large number of radiating elements, and performance is limited at fairly low frequencies, making the approach ill-suited to the context of wideband listening. There is therefore a need for an analysis method making it possible to simultaneously obtain the frequency and the direction of arrival of a broadband signal with a direct time-sampling receiver that does not comply with the Shannon criterion involving fewer calculations and exhibiting good robustness. For this, the present description relates to a method for analyzing the properties of an incident signal by an analysis device comprising an antenna array comprising N linearly spaced antennas, each antenna being identified by an index n, the index n being an integer between 0 and N-1, the method comprising a step of receiving the incident signal by the N antennas, a step of shifting each signal received by a value of n times the same increment, to obtain shifted samples, a step of calculating the summation of the shifted samples, to obtain a summation signal for the considered increment, the summation signal being the product of the value of the envelope at the value of the increment and of a modulation. The method also includes a step of extracting the value of the envelope from the value of the increment, the steps of shifting, calculating and extracting being repeated for several increments. The method also includes a step of estimating a property of the incident signal using the different values ​​of the extracted envelope. According to particular embodiments, the method comprises one or more of the following characteristics, taken in isolation or according to all the technically possible combinations: - the increment is identical for each iteration. - the extraction step involves rectification followed by low-pass filtering to obtain the absolute value of the envelope for the increment. - the envelope has a succession of local maxima and, during the estimation step, the position of the first local maximum of the envelope is determined, the position of the first local maximum being used to estimate the direction of arrival of the incident signal. - the envelope has a period, the period being the interval between two successive absolute maxima and in which, during the estimation step, the period of the envelope is determined, the period being used to estimate the frequency of the incident signal. The present description also describes a device for analyzing the properties of an incident signal, the analysis device comprising an antenna array comprising N linearly spaced antennas, the analysis device being suitable for receiving an incident signal by the N antennas, each antenna being identified by an index n, the index n being an integer between 0 and N-1. The analysis device is also suitable for, for several increments, shifting each signal received by a value of n times the same increment, to obtain shifted samples, calculate the summation of the shifted samples, to obtain a summation signal for l 'considered increment, the summation signal being the product of the value of the envelope at the value of the increment and of a modulation, and extracting the value of the envelope at the value of the increment. The analysis device is also able to estimate a property of the incident signal using the different values ​​of the extracted envelope. According to particular embodiments, the analysis device comprises one or more of the following characteristics, taken in isolation or in any technically possible combination ibles: - the device is a digital device. - the device is an analog device. The present description also describes a platform comprising a device for analyzing a signal as described above. Other characteristics and advantages of the invention will become apparent on reading the following description of embodiments of the invention, given by way of example only and with reference to the drawings which are: - [Fig 1] Figure 1, a schematic representation of a platform comprising a signal analysis device; - [Fig 2] Figure 2, a schematic view of an example of the analysis device of Figure 1; - [Fig 3] Figure 3, a schematic representation of a signal envelope obtained by the analysis device, and - [Fig 4] Figure 4, a schematic view of an example of the analysis device of Figure 1. A platform 10 is shown schematically in Figure 1. The platform 10 is, for example, a vehicle. In the example given, the platform is an aircraft. The platform 10 comprises systems 14 operating in real time ensuring the operation of the platform 10. Three real time systems 14 are shown in Figure 1. For the rest, it is assumed that one of the real-time systems is a signal analyzer 16. The analysis device 16 is suitable for analyzing the properties of an incident signal. More precisely, the analysis device 16 is suitable for simultaneously measuring the frequency of an incident signal in a predetermined frequency range and the direction of arrival of the same incident signal. The analysis device 16 is suitable for a signal having a spectral band greater than or equal to 10 GigaHertz (GHz). A signal having a spectral band greater than or equal to 10 GHz is considered to be a wideband signal. The analysis device 16 comprises an antenna array 18, processing channels 20, a calculation circuit 22 and a computer 24. The antenna array 18 is a linear array. The antenna network 18 comprises N antennas 26. N is an integer, in particular an integer greater than or equal to 10. Each antenna 26 is identified by an index n. The index n is an integer between 0 and N-1. The antennas 26 are regularly spaced at a spacing denoted a. In Figure 2, schematically, na denotes the position of the (n + 1) -th antenna 26 with by convention an origin of the distances located on the antenna 16 furthest to the left of the antenna array 18. Each antenna 26 is connected to a specific processing channel 20. Each processing channel 20 is identified by the same index n as the antenna 26 to which the processing channel 20 is connected. Each processing channel 20 comprises M successive sets of delay lines 28, each set of delay lines 28 being connected by a sampling point 30 so that each processing channel 20 comprises M sampling channels 30. The first set of delay lines 28 located behind the processing channels 20 exhibits an increase affine with the index of the processing channel 20 of the delay introduced in increments of an amount dt. M is an integer strictly greater than 1. The calculation circuit 22 comprises M summers 34 each followed by a rectifier 36 and a low-pass filter 38. The i-th adder 34 is able to carry out the sum of the signals taken from each i-th sampling point 30 of a processing channel 20. The computer 24 is able to obtain the signals at the output of each low-pass filter 38 in order to estimate the direction of arrival and the frequency of the incident signal. The operation of the device 16 is now described with reference to an example of the implementation of a method for analyzing the properties of an incident signal. The method includes a receiving step, a shifting step, a calculating step and an estimating step. It is assumed that a source emits a signal at a supposedly fixed frequency for an analysis time. During the reception step, each antenna 26 receives a signal. The actual signal received on the / 7th antenna, is written, with an amplitude S: s „(t) = S cos [a) t + kna sin q +