RF spectrum-monitoring and signal detection device

Abstract

The invention relates to an RF spectrum-monitoring and signal detection device (100), comprising: - an l / Q baseband downconversion circuit (102) receiving an RF signal, having a first output that delivers an in-phase baseband downconverted component and a second output that delivers a quadrature baseband downconverted component; - a first amplitude sign detection circuit (114) that delivers, at output, a first amplitude sign signal representative of the sign of the amplitude of the in-phase component; - a second amplitude sign detection circuit (118) that delivers, at output, a second amplitude sign signal representative of the sign of the amplitude of the quadrature component; - a frequency sign detection circuit (120) that is coupled to outputs of the amplitude sign detection circuits and that delivers, at output, a frequency sign signal representative of the sign of the phase difference between the first and second amplitude sign signals, and thus of the frequency sign of the baseband downconverted RF signal.

Description

[0001] DESCRIPTION

[0002] TITLE: RF SPECTRUM MONITORING AND SIGNAL DETECTION DEVICE

[0003] TECHNICAL FIELD

[0004] This invention relates to the field of radio frequency (RF) spectrum monitoring and signal detection, with an emphasis on low power consumption and without any prior information on the spectrum condition.

[0005] Prior art

[0006] Spectrum is a resource that is highly regulated by governing bodies. There are free spectrum bands, such as the 2.4 GHz ISM (Industrial, Scientific, and Medical) band with a bandwidth of 100 MHz, which are generating a lot of interest. There are several wireless communication standards and many industrial applications using this ISM band in which channels of completely different communication standards overlap. This makes the spectrum of this band (and other bands as well) very complex and the coexistence of signals in this band very difficult.

[0007] This congestion increases the need for spectrum monitoring and signal detection to coexist with interference activity. Signals available over the air can be located anywhere within this band. These can be wideband modulated communication signals or any type of energy-emitting industrial or commercial products located within the band. It is a very complicated task to monitor such a complex spectrum without any prior knowledge.

[0008] Another interest of spectrum monitoring is to identify a signal of interest by radio link to operate a wireless radio opportunistically to save energy, as in a radio alarm clock for example.

[0009] Generally, down-conversion and filtering are pre-processing steps required to extract information with minimal power consumption from a given frequency band located at high frequencies. Therefore, the required processing bandwidth can be reduced without any loss of information.

[0010] Low-IF (intermediate frequency) or high-IF downconversion can be implemented in a heterodyne architecture. These options require RF bandpass filtering (BPF) before downconversion, which is not centered around the local oscillator (LO) frequency. The filters used for this RF BPF can be off-chip, such as SAW filters, but with the disadvantage of increasing the cost of the circuit using these filters, and requiring high power consumption and a large chip area.

[0011] As an alternative to low-IF or high-IF downconversions, baseband downconversion, or zero-IF downconversion, can be achieved, i.e., downconversion around the DC component or 0. This baseband downconversion requires filtering centered around a LO frequency. This filter transfer function can be implemented entirely on-chip with a baseband for RF impedance transformation via a passive mixer. This drastically reduces cost and power consumption compared to SAW filters used for low-IF or high-IF downconversions. However, the band image is folded on itself and this architecture requires a homodyne architecture and thus complex signal processing to preserve the baseband information.

[0012] Energy detection is the lowest complexity and energy consumption operation that can be used to detect signals after baseband downconversion. Energy detection can be performed on the baseband signal to detect the existence of a signal in a frequency band. However, the extracted information is very limited and the usage is limited to very simple detection tasks.

[0013] Summary of the invention

[0014] An objective of the present invention is to provide a spectrum monitoring device

[0015] Low-power RF and signal detection that can detect signals in a spectrum under various conditions and without any prior information about the spectrum condition.

[0016] To this end, the invention provides an RF spectrum monitoring and signal detection device, comprising:

[0017] - an I / Q baseband down-converting circuit, comprising an input configured to receive an RF signal, a first output configured to deliver an in-phase baseband down-converted component of the RF signal, and a second output configured to deliver a quadrature baseband down-converted component of the RF signal;

[0018] - a first amplitude sign detection circuit comprising an input coupled to the first output of the l / Q baseband down-converting circuit, and configured to output a first amplitude sign signal whose amplitude value depends on the sign of the amplitude of the in-phase baseband down-converted component;

[0019] - a second amplitude sign detection circuit comprising an input coupled to the second output of the l / Q baseband down-converting circuit, and configured to output a second amplitude sign signal whose amplitude value depends on the sign of the amplitude of the quadrature baseband down-converted component;

[0020] - a frequency sign detection circuit, comprising inputs coupled to outputs of the first and second amplitude sign detection circuits, and configured to output a frequency sign signal whose amplitude value, or a presence or absence of oscillations in the frequency sign signal, depends on the sign of the phase difference between the first and second amplitude sign signals, and is representative of the frequency sign of a baseband downconverted RF signal comprising the in-phase baseband downconverted component of the RF signal and the quadrature baseband downconverted component of the RF signal.

[0021] The proposed RF spectrum monitoring and signal detection device first performs l / Q baseband down-conversion of the RF signal while dividing the signal into an in-phase component and a quadrature component. The first and second amplitude sign signals (which can be regarded as digital signals) are then generated in such a manner that the amplitude value of each of these signals depends on the sign of the amplitude of the down-conversion baseband components respectively. Finally, a frequency sign signal, which is representative of the sign of the phase difference, or delay, between the first and second amplitude sign signals, is generated.

[0022] Unlike real signals, complex signals have a non-symmetrical spectrum. Detecting the frequency sign of a complex signal as proposed in the invention determines on which half of the spectrum the signal lies. Thus, very useful information about the content of the spectrum and the location of available signals in the spectrum is extracted from this information. Therefore, a much larger amount of information can be extracted about the content of the spectrum. The extraction of these characteristic elements is carried out with phase difference information between the I and Q signals and a zero crossing rate of these I or Q signals.

[0023] The baseband frequency downscaling implemented by the device helps to reduce the required processing bandwidth to a minimum.

[0024] Detecting the frequency sign of a complex signal as proposed in the invention is more reliable than simple energy detection. Indeed, if a complex bandpass filter is applied to signals and simple energy detection is performed on the filtered signals, the extracted energy may be higher than a threshold depending on the attenuation of the filter and the intensity of the out-of-band signal, and poor detection may occur. An out-of-band signal may be at the image frequency. If energy detection is performed on I or Q signals directly without combining them to obtain the signal S = I + jQ, the image content will be merged with the desired content. In this case, it is impossible to understand whether the signal comes from a positive or negative frequency with simple energy detection.If energy detection is performed after reconstruction of the S = I + jQ signal, the image may not be completely suppressed and may remain in the desired band due to processing imperfections. It is not possible to evaluate this effect with simple energy detection. An out-of-band signal may be at a different frequency than the image frequency but it can still cause misdetection if it has sufficient power.

[0025] The proposed frequency sign detection function can mitigate these misdetections. If the signal is on the opposite side of the spectrum from the side where the filter is located, the frequency sign will eliminate misdetections even if the energy detection identifies the existence of a signal.

[0026] The RF spectrum monitoring and signal detection device according to the invention can be used for any arbitrary frequency band and / or for any arbitrary signal, regardless of the values ​​of the frequencies of the spectrum band and the complexity of the signals to be detected. The RF spectrum monitoring and signal detection device can be used to detect analog signals of any shape such as sinusoids, triangular waves, square waves, etc., which covers any industrial or medical signal, or modulated signals, which covers communication signals. The proposed architecture of the RF spectrum monitoring and signal detection device can be implemented with low power, low cost and high accuracy. Furthermore, there is no ambiguity in the result obtained between the positive and negative frequency phase difference.

[0027] The RF spectrum monitoring and signal detection device can be used for different types of applications: empty band detection, occupied band detection, coarse FFT (Fast Fourier Transform), demodulation (e.g. FSK), and synchronization. The proposed device can also be used in Bluetooth to perform RSSI (Received Signal Strength Indication) detection and channel occupancy detection for adaptive frequency hopping sequence generation. The proposed device can also be used in Bluetooth Low Energy (BLE) to detect notification packets, which may arrive with a period of 20 ms to 10 s.

[0028] The RF spectrum monitoring and signal detection device can be used as a radio alarm clock to detect a signal of interest to activate the main radio receiver. Therefore, it could drastically reduce the overall power consumption of the system. Any low-power devices using wireless communication such as an Internet of Things, low-power wireless sensor nodes, low-power wearable and implantable devices, etc. can benefit from the proposed device.

[0029] The proposed device can be used in smart car keys, which requires detecting the nearby car with very low power consumption to unlock the car or activate some other functions.

[0030] In a first embodiment, the frequency sign detection circuit may include a D flip-flop, a data input of the D flip-flop being coupled to one of the outputs of the first and second amplitude sign detection circuits, and a clock input of the D flip-flop being coupled to the other of the outputs of the first and second amplitude sign detection circuits. In this first embodiment, the frequency sign detection circuit outputs a digital signal having a value of 0 or 1 depending on the sign of the frequency of the complex signal output by the l / Q baseband down-converting circuit, and thus does not require additional display circuitry. In this configuration, the amplitude value of the frequency sign signal is representative of the frequency sign of the down-converted baseband RF signal.

[0031] In a variant of the first embodiment, the frequency sign detection circuit may comprise:

[0032] - a T flip-flop, a data input of the T flip-flop being coupled to one of the outputs of the first and second amplitude sign detection circuits, a clock input of the T flip-flop being coupled to the other of the outputs of the first and second amplitude sign detection circuits, and

[0033] - an oscillation detector comprising an input coupled to the output of the T flip-flop and configured to output a signal whose value depends on whether or not the signal output by the T flip-flop oscillates.

[0034] In this embodiment, the presence or absence of oscillations in the frequency sign signal is representative of the frequency sign of the down-converted baseband RF signal. Each of the first and second amplitude sign detection circuits may include one of the following: an amplitude limiting amplifier, a comparator, a Schmitt trigger comparator, a clock time-controlled comparator, a transconductor circuit coupled to a current comparator.

[0035] The RF spectrum monitoring and signal detection device may further comprise a first filtering unit comprising a first low-pass filter and / or a first baseband complex bandpass filter and comprising at least one input coupled to the first output of the l / Q baseband down-converting circuit and an output coupled to the input of the first amplitude sign detection circuit, and a second filtering unit comprising a second low-pass filter and / or a second baseband complex bandpass filter and comprising at least one input coupled to the second output of the l / Q baseband down-converting circuit and an output coupled to the input of the second amplitude sign detection circuit.For example, complex baseband bandpass filters can be used to filter out signals outside the ISM band and to filter out some parts inside the ISM band. Therefore, it is possible to divide the ISM band into smaller bands. For example, in very crowded and complicated spectrum conditions, this improves the processing power and accuracy of the device while reducing the power consumption of the device since the circuits after the complex baseband bandpass filters can work with a less complex spectrum and would therefore require lower power consumption.

[0036] In a second embodiment, the RF spectrum monitoring and signal detection device may further comprise at least one counter having an input coupled to one of the outputs of the first and second amplitude sign detection circuits, and configured to output an average frequency of the down-converted baseband RF signal. This second embodiment may, using the obtained value of the average frequency of the down-converted baseband RF signal, avoid misdetection if a strong out-of-band signal is on the same side as the band of interest, or in the case where there are multiple signals in the spectrum and most of the power is on the same side of the spectrum.

[0037] In a third embodiment, the RF spectrum monitoring and signal detection device may further comprise:

[0038] - an average value calculator comprising an input coupled to the output of the frequency sign detection circuit, and configured to output a signal whose value corresponds to the average of the frequency sign signal, and

[0039] - a comparator circuit configured to compare the signal output by the average value comparator to a high threshold value and / or a low threshold value. Comparing the average value of the frequency sign signal to the threshold value(s) enables single / multiple signal detection because the average of the frequency sign signals will depend on the signal content on the positive and negative side spectrum content.

[0040] In an exemplary embodiment, the average value calculator may include a low-pass filter, e.g., an integrator.

[0041] In an exemplary embodiment, the comparator circuit may comprise:

[0042] - a first voltage comparator comprising a first input coupled to the output of the average value calculator and a second input configured to receive the high threshold value, and

[0043] - a second voltage comparator comprising a first input coupled to the output of the average value calculator and a second input configured to receive the low threshold value, and

[0044] - an exclusive OR gate having two inputs coupled to the outputs of the first and second voltage comparators.

[0045] The different variants described above for the first embodiment can be applied to the second and / or third embodiments.

[0046] The RF spectrum monitoring and signal detection device may further include a receiving element including a low noise amplifier and / or an RF bandpass filter, wherein an input of the receiving element is configured to receive the RF signal, and an output of the receiving element is coupled to the input of the l / Q baseband downconverter circuit. The RF bandpass filter improves immunity to interference and unwanted signals outside the band of interest. The low noise amplifier improves the noise performance of the device, and thus improves the sensitivity of the device. The device may also include an antenna for receiving the RF signal, wherein an input of the receiving element (or the input of the l / Q baseband downconverter circuit if the device does not include the receiving element) is coupled to the antenna.The RF spectrum monitoring and signal detection device may be configured to detect at least one signal belonging to a 2.4 GHz ISM band.

[0047] The RF spectrum monitoring and signal detection device may further comprise:

[0048] - a first energy detection circuit comprising an input coupled to the first output of the l / Q baseband down-converting circuit;

[0049] - a first threshold crossing detection circuit comprising an input coupled to an output of the first energy detection circuit;

[0050] - a second energy detection circuit comprising an input coupled to the second output of the l / Q baseband down-converting circuit;

[0051] - a second threshold crossing detection circuit comprising an input coupled to an output of the second energy detection circuit.

[0052] In this case, the RF spectrum monitoring and signal detection device may further comprise:

[0053] - a plurality of first baseband complex bandpass filters each having inputs coupled to the first and second outputs of the l / Q baseband downconverter circuit and an output coupled to an input of one of a plurality of first amplitude sign detection circuits;

[0054] - a plurality of second baseband complex bandpass filters each having inputs coupled to the first and second outputs of the l / Q baseband downconverter circuit and an output coupled to an input of one of a plurality of second amplitude sign detection circuits;

[0055] - several first energy detection circuits each comprising an input coupled to the output of one of the first baseband bandpass filters;

[0056] - several first threshold crossing detection circuits each comprising an input coupled to an output of one of the first energy detection circuits;

[0057] - several second energy detection circuits each comprising an input coupled to the output of one of the second baseband bandpass filters;

[0058] - several second threshold crossing detection circuits each comprising an input coupled to an output of one of the second energy detection circuits.

[0059] The invention also provides a method for RF spectrum monitoring and signal detection, comprising:

[0060] - reception of an RF signal;

[0061] - the baseband frequency down-conversion l / Q of the RF signal into an in-phase baseband frequency down-conversion component and a quadrature baseband frequency down-conversion component;

[0062] - generating a first amplitude sign signal whose amplitude value depends on the sign of the amplitude of the in-phase baseband down-converted component, and a second amplitude sign signal whose amplitude value depends on the sign of the amplitude of the quadrature baseband down-converted component;

[0063] - generating a frequency sign signal whose amplitude value, or the presence or absence of oscillations in the frequency sign signal, depends on the sign of the phase difference between the first and second amplitude sign signals, and is thus representative of the frequency sign of a baseband down-converted RF signal comprising the in-phase baseband down-converted component of the RF signal and the quadrature baseband down-converted component of the RF signal.

[0064] Throughout the text of this application, the term "coupled" can designate either a direct connection between two elements, without an intermediate element between them, or an indirect connection between these two elements, namely a connection formed through at least one intermediate element. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] The present invention will be better understood after reading the description of exemplary embodiments given merely for informational purposes and in no way limiting with reference to the attached drawings in which: [Fig. 1] schematically shows an RF spectrum monitoring and signal detection device according to a first embodiment of the invention; [Fig. 2] shows examples of time domain signals obtained in the RF spectrum monitoring and signal detection device according to the first embodiment of the invention; [Fig. 3], [Fig. 4], [Fig. 5], [Fig. 6] and [Fig. 7] show different implementations of the first and second amplitude sign detection circuits of the RF spectrum monitoring and signal detection device according to the invention; [Fig.8] schematically shows the RF spectrum monitoring and signal detection device according to a variant of the first embodiment of the invention; [Fig. 9] shows examples of time domain signals obtained in the RF spectrum monitoring and signal detection device according to the variant of the first embodiment of the invention as shown in Fig. 8; [Fig. 10] schematically shows an RF spectrum monitoring and signal detection device according to a second embodiment of the invention; [Fig. 11] schematically shows an RF spectrum monitoring and signal detection device according to a third embodiment of the invention; [Fig. 12] schematically shows an example implementation of a part of the RF spectrum monitoring and signal detection device according to the third embodiment of the invention; [Fig.13] schematically shows an RF spectrum monitoring and signal detection device according to the second embodiment of the invention and comprising several optional elements; [Fig. 14] schematically shows an RF spectrum monitoring and signal detection device according to a fourth embodiment of the invention.

[0066] Identical, similar or equivalent parts of the various figures described below bear the same numerical references so as to facilitate the transition from one figure to another.

[0067] The various parts shown in the figures are not necessarily shown to a uniform scale, to make the figures more readable.

[0068] The different possibilities (variants and embodiments) must be understood as not mutually exclusive and can be combined with each other.

[0069] Detailed description of particular embodiments

[0070] An RF spectrum monitoring and signal detection device 100 according to a first embodiment is described below in connection with Fig. 1.

[0071] The device 100 includes an I / Q baseband downconverter circuit 102. The circuit 102 includes an input 104 to which an RF signal is applied. For example, the device 100 may be part of an RF signal receiver, and the input 104 may be coupled to an antenna from which the RF signal is received, an LNA (low noise amplifier) ​​amplifying the RF signal received by the antenna, and a BPF (band pass filter) filtering the received RF signal at the band of interest. These components are not shown in Fig. 1. For example, the RF signal may belong to a 2.4 GHz ISM band, and may correspond to a WLAN signal. The RF signal is analog signals of any shape such as a sine wave, a triangle wave, a square wave, etc. as used in any industrial or medical application. The RF signal can also be a modulated signal, as used in communications applications.To simplify the description of the invention, it is considered that a sinusoidal RF signal is applied to the input 104.

[0072] The input 104 is split in two such that the RF signal is applied to a first input of a first multiplier 106, or first mixer, and to a first input of a second multiplier 108, or second mixer. The baseband frequency down-conversion of the RF signal is achieved by mixing the RF signal with a LO signal, for example generated from a local oscillator (not shown in Fig. 1), having a frequency fi_o whose value is equal to or very close to the carrier frequency of the RF signal. According to an exemplary embodiment, the LO signal may correspond to a sinusoidal signal (however other types of signal may be used). For example, if the RF signal belongs to the ISM band between 2400 MHz and 2500 MHz, the frequency fi_o may be equal to 2450 MHz to obtain a baseband signal having a frequency between -50 MHz and 50 MHz. The LO signal is applied to a second input of the first multiplier 106.The l / Q baseband down-converter circuit 102 also includes a quadrature phase shifter 110 receiving the LO signal at one input and outputting the LO signal 90° out of phase with respect to the original LO signal. The 90° out of phase LO signal is applied to a second input of the second multiplier 108.

[0073] The first and second multipliers 106, 108 and the quadrature phase shifter 110 may be fabricated as described in C. Andrews and A.C. Molnar, "A Passive Mixer-First Receiver With Digitally Controlled and Widely Tunable RF Interface," in IEEE Journal of Solid-State Circuits, Vol. 45, No. 12, pp. 2696-2708, Dec. 2010, or in P. Song and H. Hashemi, "mm-Wave Mixer-First Receiver With Selective Passive Wideband Low-Pass Filtering," in IEEE Journal of Solid-State Circuits, Vol. 56, No. 5, pp. 1454-1463, May 2021.

[0074] The l / Q baseband downconverter circuit 102 includes a first output, corresponding to an output of the first multiplier 106, onto which an in-phase baseband downconverted component of the RF signal is output, and a second output, corresponding to an output of the second multiplier 108, onto which a quadrature baseband downconverted component of the RF signal is output.

[0075] The device 100 further comprises a first filtering unit comprising, in this example, a first low-pass filter 112 comprising an input coupled to the first output of the l / Q baseband down-converting circuit 102 and an output coupled to the input of a first amplitude sign detection circuit 114. The device 100 also comprises a second filtering unit comprising, in this example, a second low-pass filter 116 comprising an input coupled to the second output of the l / Q baseband down-converting circuit 102 and an output coupled to the input of the second amplitude sign detection circuit 118. The signal output by the first low-pass filter 112 (i.e., the signal output by the first filtering unit) is referred to as signal / in FIG.1, and the signal output by the second low-pass filter 116 (i.e., the signal output by the second filter unit) is referred to as the Q signal in Fig. 1. The first and second low-pass filters 112, 116 may have cutoff frequencies equal to 50 MHz when the baseband frequency is between -50 MHz and 50 MHz.

[0076] The in-phase and quadrature baseband down-converted components of the RF signal output by the first and second multipliers 106, 108, and thus also the / and Q signals, have the same frequency since they are a real and imaginary part of the same signal.

[0077] The first amplitude sign detection circuit 114 is configured to output a first digital amplitude sign signal whose value depends on the sign of the amplitude of the signal / . In Fig. 1, the signal output by the first amplitude sign detection circuit 114 is called l Sign . The second amplitude sign detection circuit 118 is configured to output a second digital amplitude sign signal whose value depends on the sign of the amplitude of the signal Q. In Fig. 1, the signal output by the first amplitude sign detection circuit 118 is called Q Sign .

[0078] The device 100 further comprises a frequency sign detection circuit 120, comprising inputs coupled to outputs of the first and second amplitude sign detection circuits 114, 118, and configured to output a frequency sign signal (referred to as Freq. Sign in Fig. 1) whose value depends on the sign of the phase difference between the first and second digital amplitude sign signals l Sign and Q sign. For example, in the first embodiment described herein, the frequency sign detection circuit 120 corresponds to a D flip-flop having a data input coupled to one of the outputs of the first and second amplitude sign detection circuits 114, 118 (coupled to the output of the first amplitude sign detection circuit 114 in the example shown in Fig. 1), and a clock input coupled to the other of the outputs of the first and second amplitude sign detection circuits 114, 118 (coupled to the output of the second amplitude sign detection circuit 118 in the example shown in Fig. 1).

[0079] Fig. 2 shows examples of time domain signals obtained in the RF spectrum monitoring and signal detection device 100 shown in Fig. 1. The signals shown in the left part of Fig. 2 are obtained when the frequency of the baseband down-converted RF signal is positive, and the signals shown in the right part of Fig. 2 are obtained when the frequency of the baseband down-converted RF signal is negative. In order to simplify the description, the signals / and Q are considered to correspond to sinusoids. Thus, when the frequency of the baseband down-converted RF signal is positive, the zero-crossing time in a rising edge direction of the signal / has occurred before the zero-crossing time in a rising edge direction of the signal Q.Conversely, when the frequency of the down-converted baseband RF signal is negative, the time of the zero crossing in a rising edge direction of the signal / occurred after the time of the zero crossing in a rising edge direction of the signal Q.

[0080] Amplitude sign detection circuits 114, 118 convert modulated sinusoids into square waves that change values ​​at times corresponding to zero-crossing times of the sinusoids. Frequency sign detection circuit 120, which corresponds to a D flip-flop in the exemplary embodiment shown in Fig. 1, samples the amplitude of the Signat the rising edge time Qsign to detect the frequency sign of the RF signal. Thus, the frequency sign detection circuit 120 outputs a signal "1" when the frequency of the baseband down-converted RF signal is positive, and outputs a signal "0" when the frequency of the baseband down-converted RF signal is negative.

[0081] In the device 100 shown in Fig. 1, if the frequency to be detected is positive, the signal / leads the signal Q by 90 degrees. If the frequency is negative, the signal Q leads the signal / by 90 degrees. If the amplitude of the signal / is positive at a zero-crossing time of the signal Q in the rising edge direction, this means that the detected frequency is positive. If the amplitude of the signal / is negative at a zero-crossing time of the signal Q in the rising edge direction, this means that the detected frequency is negative.

[0082] This principle can be extended to the zero crossing time in a falling edge direction. If the amplitude of the signal / is positive at a zero crossing time of the signal Q in the falling edge direction, this means that the detected frequency is negative. If the amplitude of the signal / is negative at a zero crossing time of the signal Q in the falling edge direction, this means that the frequency is positive. Alternatively, the device 100 can be manufactured in such a way that it utilizes these properties, for example, by using a negative edge triggered D flip-flop as the frequency sign detection circuit 120.

[0083] Alternatively, this principle can be extended and based on signal zero crossing instants / . For example, if the amplitude of signal Q is positive at the signal zero crossing instant / in the rising edge direction, this means that the detected frequency is negative. If the amplitude of signal Q is negative at the signal zero crossing instant / in the rising edge direction, this means that the detected frequency is positive. If the amplitude of signal Q is positive at the signal zero crossing instant / in the falling edge direction, this means that the detected frequency is positive. If the amplitude of signal Q is negative at the signal zero crossing instant / in the falling edge direction, this means that the detected frequency is negative. In these configurations, signal Q Signis applied to the data input and the / sign signal is applied to the clock input of the D flip-flop (which can be edge triggered or edge triggered).

[0084] Various implementations of the first and second amplitude sign detection circuits 114, 118 are described below.

[0085] As shown in Fig. 3, each of the first and second amplitude sign detection circuits 114, 118 may correspond to an amplitude-limiting amplifier formed by a differential amplifier receiving at its inverting input the signal / or Q through a resistor R. The non-inverting input of each of the amplitude-limiting amplifiers is coupled to a reference voltage, for example ground. The output of each of the amplitude-limiting amplifiers is coupled to its inverting input through two Zener diodes connected to each other in series but inverted with respect to each other.

[0086] Alternatively, as shown in Fig. 4, each of the first and second amplitude sign detection circuits 114, 118 may correspond to a comparator receiving on its non-inverting input the signal / or Q. The non-inverting input of each of the comparators is coupled to a reference voltage, for example ground. An advantage of this configuration is that the comparators are easier to design in CMOS technology since it does not require a diode or feedback circuit. It can also allow higher speeds to be achieved.

[0087] Alternatively, as shown in Fig. 5, each of the first and second amplitude sign detection circuits 114, 118 may correspond to a Schmitt trigger comparator receiving at its non-inverting input the signal / or Q. The non-inverting input of each of the Schmitt trigger comparators is coupled to a reference voltage, for example ground. An advantage of this configuration is that the Schmitt trigger comparator improves noise immunity of the circuit.

[0088] Alternatively, as shown in Fig. 6, each of the first and second amplitude sign detection circuits 114, 118 may correspond to a clock-time-set comparator receiving at its non-inverting input the signal / or Q. The non-inverting input of each of the clock-time-set comparators is coupled to a reference voltage, for example ground. The same clock signal is applied to the clock input of both clock-time-set comparators. An advantage of this configuration is that clock-time-set comparators are faster and have better sensitivity than continuous-time comparators. This architecture can be used with a sufficiently high oversampling ratio which would be determined by the highest frequency content.

[0089] Alternatively, as shown in Fig. 7, each of the first and second amplitude sign detection circuits 114, 118 may correspond to a transconductor circuit coupled to a current comparator. The signals / and Q are applied to the non-inverting inputs of the transconductor circuits. The inverting input of each of the transconductor circuits is coupled to a reference voltage, for example, ground. The outputs of the transconductor circuits are coupled to the inputs of the current comparators, and the signals / s , gnand Qsign are delivered on the outputs of the current comparators. This configuration is advantageously used for high frequency applications and can improve the performance for high frequency signals. The different implementations previously disclosed in connection with Figs. 3 to 7 can be combined in such a way that one of the first and second amplitude sign detection circuits 114, 118 is manufactured in accordance with one of these implementations and the other of the first and second amplitude sign detection circuits 114, 118 is manufactured in accordance with another of these implementations. A variant of the RF spectrum monitoring and signal detection device 100 according to the first embodiment is described below in connection with Fig. 8. Compared to the device 100 previously described in connection with Fig. 1, the frequency sign detection circuit 120 of the device 100 shown in Fig.8 includes a T flip-flop. A data input of the T flip-flop is coupled to one of the outputs of the first and second amplitude sign detection circuits 114, 118 (coupled to the output of the first amplitude sign detection circuit 114 in the example shown in Fig. 8), and a clock input of the T flip-flop is coupled to the other of the outputs of the first and second amplitude sign detection circuits 114, 118 (coupled to the output of the second amplitude sign detection circuit 118 in the example shown in Fig. 8). The frequency sign detection circuit 120 of the device 100 shown in Fig. 8 further includes an oscillation detector having an input coupled to the output of the T flip-flop and configured to output a signal whose value depends on whether the signal output by the T flip-flop is oscillating.9 shows examples of time domain signals obtained in the RF spectrum monitoring and signal detection device 100 shown in Fig. 8. The signals shown in the left part of Fig. 9 are obtained when the frequency of the baseband down-converted RF signal is positive, and the signals shown in the right part of Fig. 9 are obtained when the frequency of the baseband down-converted RF signal is negative. The signals / , Q, / . s / gnand Qsign are similar to those previously described in connection with Fig. 2. The value of the signal output by the T flip-flop is inverted when the value applied to the data input is 1 at the rising clock edge, and the value of the signal output by the T flip-flop is preserved when the value applied to the data input is 0 at the rising clock edge. Therefore, the value of the signal output by the T flip-flop oscillates at half the frequency of the signal applied to the clock input when the frequency of the applied detected signal is positive and it will be either the constant 0 or 1 when the frequency of the detected signal is negative. The oscillation detector is used to generate digital outputs 0 and 1. Optionally, the oscillating T flip-flop output can be used as a trigger for other operations in the device 100.

[0090] The different implementations of the first and second amplitude sign detection circuits 114, 118 described above can be applied for the device 100 shown in Fig. 8.

[0091] An RF spectrum monitoring and signal detection device 100 according to a second embodiment is described below in connection with Fig. 10. Compared to the device 100 according to the first embodiment, the device 100 according to the second embodiment comprises a first filter unit comprising, in the example described herein, the first low-pass filter 112 and a first baseband complex bandpass filter 140 connected to each other in series. The output of the first multiplier 106 is coupled to the input of the first low-pass filter 112. The output of the first low-pass filter 112 is coupled to the input of the first baseband complex bandpass filter 140. The output of the first baseband complex bandpass filter 140 is coupled to the input of the first amplitude sign detection circuit 114.

[0092] The device 100 also includes a second filtering unit having, in the example described herein, the second low-pass filter 116 and a second baseband complex bandpass filter 142 connected to each other in series. The output of the second multiplier 108 is coupled to the input of the second low-pass filter 116. The output of the second low-pass filter 116 is coupled to the input of the second baseband complex bandpass filter 142. The output of the second baseband complex bandpass filter 142 is coupled to the input of the second amplitude sign detection circuit 118.

[0093] In Figure 10, filters 140, 142 are shown as being interconnected to illustrate that each of the filters 140, 142 receives, on the inputs, the outputs of the previous stage, namely here the outputs of the first and second low-pass filters 112, 116. The device 100 further comprises a counter 122 having an input coupled to one of the outputs of the first and second amplitude sign detection circuits 114, 118 (coupled to the output of the first amplitude sign detection circuit 114 in the example shown in Fig. 10). The counter 122 can count, during a predetermined period of time, the number of rising edges of the signal l S ig n or Qsign, and is configured to output an average frequency of the down-converted baseband RF signal, obtained by normalizing the counter value with the predetermined time period, which will give the zero crossing rate, hence the average frequency.

[0094] In this second embodiment, the device 100 performs, in addition to the frequency detection function, an average frequency extraction. Indeed, a zero crossing rate of a single signal corresponds to the center frequency of this signal. A zero crossing rate of multiple signals corresponds to the average of signal center frequencies weighted according to their power levels. If a strong out-of-band signal is located on the same side as the band of interest, or in the case where multiple signals exist in the spectrum and the majority of the power is located on the same side of the spectrum as the filter, using only the energy detection and frequency sign characteristic elements only makes it possible to detect the existence of a signal and the location of the majority of the power of the existing signal (on the positive or negative side of the spectrum).With the average frequency extraction performed in this second embodiment, if the average frequency, called f. av g, is not close to the center frequency of the spectrum obtained at the output of the filter units, namely the low-pass filter 112 or 116 in the example described here, the detected signal will be correctly identified as an interfering signal. If f avg is close to the center frequency of the spectrum obtained at the output of the filtering units, the detected signal will be correctly identified as belonging to the band of interest.

[0095] The different implementations of the first and second amplitude sign detection circuits 114, 118 and the frequency sign detection circuit 120 described previously can be applied for the device 100 according to the second embodiment.

[0096] When a single sinusoid or single modulated signal exists in the spectrum, a frequency sign characteristic is expected to be robust and a constant 0 or 1 depending on the frequency sign. However, when multiple signals exist on opposite sides of the spectrum, a frequency sign characteristic will fluctuate between 0 and 1 depending on the signal center frequencies and signal powers. Therefore, the existence of a single and multiple signals can be distinguished by observing the activity on the output of the frequency sign characteristic. This additional information can be used to analyze the complexity (clutter) of the spectrum.

[0097] An RF spectrum monitoring and signal detection device 100 according to a third embodiment is described below in connection with Fig. 11.

[0098] To distinguish between the existence of a single and multiple signals, the device 100 according to the third embodiment further comprises:

[0099] - an average value calculator 124 comprising an input coupled to the output of the frequency sign detection circuit 120, and configured to output an analog signal whose value corresponds to the average of the frequency sign signal Freq. Sign;

[0100] - a comparator circuit 126 configured to compare the signal output by the average value comparator 124 to a high threshold value and / or a low threshold value;

[0101] In this third embodiment, the average of the frequency sign signal Freq. Sign will depend on the signal content on the positive and negative side spectrum content. Tl

[0102] The existence of a single and multiple signal is then detected by comparing this average value to the determined high and / or low threshold values. Thus the device 100 according to the third embodiment can be used to identify the existence of a multiple signal and can be configured in a more powerful processing mode to resolve erroneous detections in the event of the existence of a multiple signal.

[0103] Fig. 12 shows an exemplary implementation of the average value calculator 124 and the comparator circuit 126. In this example, the average value calculator 124 includes an integrator, and the comparator circuit 126 includes:

[0104] - a first voltage comparator 128 comprising a first input (inverting input in Fig. 12) coupled to the output of the average value calculator 124 and a second input (non-inverting input in Fig. 12) to which a high threshold value is applied, and

[0105] - a second voltage comparator 130 comprising a first input (non-inverting input in Fig. 12) coupled to the output of the average value calculator 124 and a second input (inverting input in Fig. 12) on which a low threshold value V t h,L is applied, and

[0106] - an exclusive OR gate 132 having two inputs coupled to the outputs of the first and second voltage comparators 128, 130.

[0107] In this configuration, the integrator calculates the average of the frequency sign signal Freq. Sign, called avg(f.sign) in Fig. 12. When signals exist on only one side of the monitored spectrum, this average signal avg(f.sign) is below Vth,L or above V th,H and the output value delivered by the exclusive OR gate 132 will be 1. When signals exist on both sides of the monitored spectrum, the average signal avg(f.sign) will be between the thresholds and the output value delivered by the exclusive OR gate 132 will be 0.

[0108] The different implementations of the first and second amplitude sign detection circuits 114, 118 and the frequency sign detection circuit 120 described above may be applied for the device 100 according to the third embodiment. In addition, the device 100 according to the third embodiment may comprise the counter 122 as previously disclosed in the second embodiment. Fig. 13 shows an example of the device 100 according to the second embodiment, in a configuration comprising several additional optional elements.

[0109] A first additional optional element of the device 100 is an antenna 134 through which the RF signal is received.

[0110] The device 100 also includes an RF bandpass filter 136, one input of which is coupled to the antenna 134. The filter 136 filters the received RF signal at the band of interest.

[0111] Another optional element of the device 100 is an LNA (low noise amplifier) ​​138 having an input coupled to an output of the filter 136 and an output coupled to the first inputs of the first and second multipliers 106, 108.

[0112] In the configuration shown in Fig. 13, the device 100 includes the RF bandpass filter 136 and the LNA 138, the input of the bandpass filter 136 being coupled to the antenna 134, the output of the bandpass filter 136 being coupled to the input of the LNA 138, and the output of the LNA 138 being coupled to the first inputs of the first and second multipliers 106, 108.

[0113] In one variation, the device 100 may include the RF bandpass filter 136 without the LNA 138 (i.e., with the output of the filter 136 directly coupled to the first inputs of the first and second multipliers 106, 108). In another variation, the device 100 may include the LNA 138 without the RF bandpass filter 136 (i.e., with the input of the LNA 138 directly coupled to the antenna 134). In another variation, the device 100 may include the LNA 138 having its input coupled to the antenna 134 and its output coupled to the input of the RF bandpass filter 136. In another variation, the device 100 may include neither the RF bandpass filter 136 nor the LNA 138 (the antenna 134 being directly coupled to the first inputs of the first and second multipliers 106, 108).

[0114] The device 100 shown in Fig. 13 comprises a first filtering unit comprising, in addition to the first low-pass filter 112, a first baseband complex bandpass filter 140, one input of which is coupled to the output of the first low-pass filter 112. The signal output by the first low-pass filter is called the BBi signal. The output of the first baseband complex bandpass filter 140 is coupled to the input of the first amplitude sign detection circuit 114. The device 100 also comprises a second filtering unit comprising, in addition to the second low-pass filter 116, a second baseband complex bandpass filter 142, one input of which is coupled to the output of the second low-pass filter 116. The signal output by the second low-pass filter is called the BBQ signal. The output of the second baseband complex bandpass filter 142 is coupled to the input of the second amplitude sign detection circuit 118.The first and second baseband complex bandpass filters 140, 142 allow processing to focus on a small portion of the baseband signal prior to operations performed by the first and second amplitude sign detection circuits 114, 118.

[0115] Fig. 14 shows an example of the device 100 according to a fourth embodiment. Compared to the previous embodiments, the device 100 according to this fourth embodiment comprises several additional elements in order to determine several other information concerning the RF signal received by the device 100.

[0116] As previously disclosed, the device 100 includes elements 134, 136, 138, 106, 108, 110, 112, and 118. However, in alternative embodiments, the device 100 may include only a portion of the elements.

[0117] The signals obtained at the outputs of the low-pass filters 112, 116 are applied to the inputs of a first block 200 which comprises at least the circuits 114, 118 and 120 corresponding to those described previously for the other embodiments. In the example shown in Fig. 14, the first block 200 also comprises the counter 122. The first block 200 may also comprise the circuits 124, 126 described previously.

[0118] In addition to detecting the frequency sign of the complex signal and determining the average frequency of the down-converted RF signal in baseband performed by block 200 (and also identifying the existence of a multiple signal if first block 200 includes circuits 124, 126), device 100 includes a block 202 performing energy detection in the down-converted band, and thus in the RF band. To perform this energy detection, block 202 includes a first energy detection circuit 204. This first circuit 204 is non-linear. In the example of Fig. 14, first circuit 204 includes a circuit 206 for calculating the square or absolute value of the signal(s) present in the band under study.Such a circuit 206 for calculating the absolute value of the square of the signal(s) comprises for example a rectifier that only lets through positive signals or a rectifier circuit based on diodes or a circuit calculating the absolute value of the signal. The calculation of the square of the signal(s) may be carried out using a mixer or a differential circuit as described for example in the document "Performance of a Simple Architecture of an Analog CMOS Detector for MB-UWB Receiver" by M Mroue et al., IEEE ICUWB, Sep 2009, Vancouver, Canada. Pages 107-112. Alternatively, the circuit 206 may correspond to an envelope detector circuit.

[0119] The first circuit 204 also comprises, in the example of Fig. 14, a low-pass filter 208 used to stabilize the signal output by the circuit 206 by averaging the energy of this signal over a certain period. The cut-off frequency of this filter 208 is advantageously chosen in such a way that it is neither too low (which makes it possible to have satisfactory energy precision but, on the other hand, a long measurement duration) nor too high (rapid but inaccurate measurement). For example, the cut-off frequency of the low-pass filter 208 may be between the value of the bandwidth of the signal and 1 / 5 of this value. Such a low-pass filter 208 comprises, for example, a current source coupled to a capacitor.

[0120] This energy detection may be repeated until non-zero energy is detected in the RF frequency band, meaning that at least one signal is present in the RF frequency band in which the detection is performed. In the absence of energy detection, the rate at which the first circuit 204 performs the energy detection and / or the duration during which each energy detection is performed by the first circuit 204 may be adjusted according to the characteristics of one or more signals being searched for and / or an occupancy rate of the RF frequency band.

[0121] Between two consecutive energy detections, the device 100 may be placed in a reduced operating state, or standby, in which certain circuits of the device 100 are not powered, thereby reducing the power consumption of the device 100.

[0122] The frequency of the signal representing the energy of the RF signal is also determined. For this, the signal obtained at the output of the first circuit 204 is applied to the input of a first high-pass filter 210 which makes it possible to remove the DC component of the signal(s) present in the frequency band. The signal obtained at the output of the first high-pass filter 210 is applied to the input of a threshold crossing detection circuit 212. This circuit 212 counts, during a given period, the number of times that the input signal crosses a threshold value which corresponds for example to 0 (with in this case the circuit 212 which corresponds to a ZCR detector (“zero crossing”)). The value obtained at the output of circuit 212 will make it possible to determine the average frequency of the energy of the received signal.

[0123] When one or more signals are detected in the frequency band, the energy detection steps may be repeated so as to define the evolution of the energy of the detected RF signal(s) as a function of time.

[0124] In the exemplary embodiment shown in Fig. 14, the device 100 further comprises circuitry for determining other characteristic elements of the detected signal(s):

[0125] - a circuit 214 determining, from the signal obtained at the output of the first circuit 204, the establishment time of the detected signal(s). For example, to measure the adjustment time, the circuit 214 can perform a comparison between two different integrations of the detected energy obtained by using different cut-off frequencies in the low-pass filter 208 of the energy detection circuit 204. The adjustment time is then determined by detecting the passage of the two functions obtained, or by sampling several values ​​obtained at the output of the two integrations;

[0126] - a peak value detector 216 receiving as input the signals delivered as output by the first high-pass filter 210. This peak detector 216 comprises for example an integrator circuit;

[0127] - a circuit 218 determining, from a signal delivered at the output by the detector 216, Tl the maximum amplitude of the signal(s);

[0128] - a circuit 220 determining, from a signal delivered at the output by the circuit 218, the bandwidth of the signal(s).

[0129] Other characteristic elements of the detected signal(s) may be determined, such as for example the initial slope of the energy and / or the value after establishment of the energy and / or the standard deviation after establishment of this or these signals. The various characteristic elements determined by the block 202 are obtained from the signal BB / . The device 100 also comprises a second block 222 comprising circuits similar to those of the block 202, but receiving the signal BBQ as input. The operations described previously carried out by the block 202 are thus also carried out by the block 222 on the signal BBQ.

[0130] In the device 100 described in connection with Fig. 14, the determination of the signal characteristic elements is carried out simultaneously for the entire RF frequency band by the circuits of the blocks 200, 202 and 222 described previously, and also for one or more sub-bands of the RF spectrum in order to refine the characterization of the signal(s) present in the RF frequency band. For this, the detection and characterization is carried out in one or more frequency sub-bands by other elements similar to those described previously for the blocks 200, 202 and 222, and which form one or A / other detection chains, A / being an integer greater than or equal to 2.

[0131] Thus, the device 100 comprises one or more first complex baseband bandpass filters 140I-140N and one or more second complex baseband bandpass filters 142I-142N receiving as inputs the signals BBi and BBQ, each detection chain comprising one of these first complex baseband bandpass filters 140I-140N and one of these second complex baseband bandpass filters 142I-142N. The output of each of the filters 140I-140N and the filters 142i-142N is coupled to the input of a block 200I-200N, for example identical to the block 200 described previously. The output of each of the first filters 140I-140N is also coupled to the input of a block 202I-202N, for example identical to the block 202 described previously, and the output of each of the second filters 142I-142N is also coupled to the input of a block 222I-222N, for example identical to the block 222 described previously.

[0132] Thus, each detection chain comprising one of the first baseband complex bandpass filters 140I-140N and one of the second baseband complex bandpass filters 142I-142N makes it possible to determine the characteristic elements of the signal as explained previously for the blocks 200, 202, 222, but for the different sub-bands defined by the filters 140I-140N and 142I-142N. Other characteristic elements of the RF signal(s) present in the RF sub-bands can be determined, such as the initial slope of the energy and / or the value after establishment of the energy and / or the standard deviation after establishment of this or these signals.

[0133] Depending on the information obtained with the previously described elements of the device 100 and the information sought, several additional steps can be implemented by the device 100, corresponding to several operating modes of the device 100, in order to complete these previous steps and refine the detection and identification of the signals present in the RF spectrum.

[0134] In a first operating mode, if the information obtained previously is sufficient, it is possible to carry out a classification and / or a count of the signals identified previously. The classification is carried out from the characteristic elements of the signals which have been determined. The classification which is carried out may correspond for example to a classification of the detected signals according to their type (WiFi, Bluetooth, Microwave, etc.), their standard (802.11b, 802.11g, etc.), their bandwidth, their speed, etc. To be able to obtain a classification of the signals, the device 100 may implement deterministic algorithms or data processing of the artificial intelligence type such as machine learning.

[0135] In a second mode of operation, the steps implemented previously may be repeated in one or more other sub-bands of the RF spectrum comprising one or more desired signals.

[0136] In a third mode, it is possible to repeat the steps previously implemented by masking one or more unwanted signals in the spectrum, when such unwanted signals have been previously identified. For this, it is possible to choose the times of implementation of the frequency identification steps so as to avoid the presence of this or these unwanted signals in the analyzed spectrum and / or to cancel this or these previously identified signals in the analyzed spectrum (by means of a subtraction of this or these signals). This is similar to an increase in the processing dynamics of the reception chain by separation of the signals thanks to the first and second baseband complex bandpass filters 140I-140N, 142I-142N, taking advantage of the analysis of the strongest signal or signals in a dedicated filter and canceling this or these signals through a feedback loop.

[0137] The control of the circuits of the device 100, namely the sending of signals in the various circuits of the device 100 and the adjustment of the parameters of these circuits, can be carried out by a control circuit.

[0138] The various circuits of the device 100 may be implemented in the form of a semiconductor chip.

[0139] As an alternative to the configuration shown in Fig. 14, the device 100 may comprise the filters 140I-140N, 142I-142N and the blocks 200I-200N, 202I-202N, 222I-222N, but not the blocks 200, 202 and 222. In this alternative, the characteristic elements of the received signal are extracted only for the different sub-bands defined by the filters 140I-140N, 142I-142N, and not from the entire RF spectrum.

[0140] In all the embodiments described above, it is possible that the low-pass filters 112, 116 correspond to complex or real low-pass filters.

Claims

CLAIMS 1. RF spectrum monitoring and signal detection device (100), comprising: - an I / Q baseband downconverter circuit (102), comprising an input (104) configured to receive an RF signal, a first output configured to output an in-phase baseband downconverted component of the RF signal, and a second output configured to output a quadrature baseband downconverted component of the RF signal; - a first amplitude sign detection circuit (114) comprising an input coupled to the first output of the l / Q baseband downconverter circuit (102), and configured to output a first amplitude sign signal whose amplitude value depends on the sign of the amplitude of the in-phase baseband downconverted component; - a second amplitude sign detection circuit (118) comprising an input coupled to the second output of the l / Q baseband downconverter circuit (102), and configured to output a second amplitude sign signal whose amplitude value depends on the sign of the amplitude of the quadrature baseband downconverted component; - a frequency sign detection circuit (120), comprising inputs coupled to outputs of the first and second amplitude sign detection circuits (114, 118), and configured to output a frequency sign signal whose amplitude value, or a presence or absence of oscillations in the frequency sign signal, depends on the sign of the phase difference between the first and second amplitude sign signals, and is representative of the frequency sign of a baseband downconverted RF signal comprising the in-phase baseband downconverted component of the RF signal and the quadrature baseband downconverted component of the RF signal.

2. The RF spectrum monitoring and signal detection device (100) of claim 1, wherein the frequency sign detection circuit (120) comprises a D flip-flop, a data input of the D flip-flop being coupled to one of the outputs first and second amplitude sign detection circuits (114, 118), and a clock input of the D flip-flop being coupled to the other of the outputs of the first and second amplitude sign detection circuits (114, 118).

3. The RF spectrum monitoring and signal detection device (100) of claim 1, wherein the frequency sign detection circuit (120) comprises: - a T flip-flop, a data input of the T flip-flop being coupled to one of the outputs of the first and second amplitude sign detection circuits (114, 118), a clock input of the T flip-flop being coupled to the other of the outputs of the first and second amplitude sign detection circuits (114, 118), and - an oscillation detector comprising an input coupled to the output of the T flip-flop and configured to output a signal whose value depends on whether or not the signal output by the T flip-flop oscillates.

4. The RF spectrum monitoring and signal detection device (100) of claim 1, wherein each of the first and second amplitude sign detection circuits (114, 118) comprises one of the following: an amplitude limiting amplifier, a comparator, a Schmitt trigger comparator, a clock time adjusted comparator, a transconductor circuit coupled to a current comparator.

5. The RF spectrum monitoring and signal detection device (100) according to one of claims 1 to 4, further comprising a first filter unit comprising a first low-pass filter (112) and / or a first baseband complex bandpass filter (140) and comprising at least one input coupled to the first output of the l / Q baseband down-converting circuit (102) and an output coupled to the input of the first amplitude sign detection circuit (114), and a second filter unit comprising a second low-pass filter (116) and / or a second baseband complex bandpass filter (142) and comprising at least one input coupled to the second output of the l / Q baseband down-converting circuit (102) and an output coupled to the input of the second amplitude sign detection circuit (118).

6. The RF spectrum monitoring and signal detection device (100) of claim 1, further comprising at least one counter (122) having an input coupled to one of the outputs of the first and second amplitude sign detection circuits (114, 118), and configured to output an average frequency of the down-converted baseband RF signal.

7. An RF spectrum monitoring and signal detection device (100) according to one of claims 1 to 6, further comprising: - an average value calculator (124) comprising an input coupled to the output of the frequency sign detection circuit (120), and configured to output a signal whose value corresponds to the average of the frequency sign signal, and - a comparator circuit (126) configured to compare the signal output by the average value comparator (124) to a high threshold value and / or a low threshold value.

8. An RF spectrum monitoring and signal detection device (100) according to claim 7, wherein the average value calculator (124) comprises a low-pass filter, for example an integrator.

9. RF spectrum monitoring and signal detection device (100) according to one of claims 7 and 8, wherein the comparator circuit (126) comprises: - a first voltage comparator (128) comprising a first input coupled to the output of the average value calculator (124) and a second input configured to receive the high threshold value, and - a second voltage comparator (130) comprising a first input coupled to the output of the average value calculator (124) and a second input configured to receive the low threshold value, and - an exclusive OR gate (132) having two inputs coupled to the outputs of the first and second voltage comparators (128, 130).

10. An RF spectrum monitoring and signal detection device (100) according to one of claims 1 to 9, further comprising a receiving element comprising a low noise amplifier and / or an RF bandpass filter, an input of the receiving element being configured to receive the RF signal, and an output of the receiving element receiving being coupled to the input of the l / Q baseband down-converter circuit (102).

11. RF spectrum monitoring and signal detection device (100) according to one of claims 1 to 10, wherein the RF spectrum monitoring and signal detection device (100) is configured to detect at least one signal belonging to a 2.4 GHz ISM band.

12. An RF spectrum monitoring and signal detection device (100) according to one of the preceding claims, further comprising: - a first energy detection circuit (204) comprising an input coupled to the first output of the l / Q baseband downconverter circuit (102); - a first threshold crossing detection circuit (214) comprising an input coupled to an output of the first energy detection circuit (204); - a second energy detection circuit comprising an input coupled to the second output of the l / Q baseband down-converting circuit (102); - a second threshold crossing detection circuit comprising an input coupled to an output of the second energy detection circuit.

13. An RF spectrum monitoring and signal detection device (100) according to claim 12, comprising: - a plurality of first baseband complex bandpass filters (140I-140N) each having inputs coupled to the first and second outputs of the l / Q baseband downconverter circuit (102) and an output coupled to an input of one of a plurality of first amplitude sign detection circuits (114); - a plurality of second baseband complex bandpass filters (142I-142N) each having inputs coupled to the first and second outputs of the l / Q baseband downconverter circuit (102) and an output coupled to an input of one of a plurality of second amplitude sign detection circuits (118); - several first energy detection circuits (204) each comprising an input coupled to the output of one of the first baseband bandpass filters (140i-140N); - several first threshold crossing detection circuits (214) comprising each an input coupled to an output of one of the first energy detection circuits (204); - several second energy detection circuits each comprising an input coupled to the output of one of the second baseband bandpass filters (142i- 142 N ) ; - several second threshold crossing detection circuits each comprising an input coupled to an output of one of the second energy detection circuits.

14. A method of RF spectrum monitoring and signal detection, comprising: - reception of an RF signal; - down-converting the RF signal into an in-phase baseband down-converted component and a quadrature baseband down-converted component; - generating a first amplitude sign signal whose amplitude value depends on the sign of the amplitude of the in-phase baseband down-converted component, and a second amplitude sign signal whose amplitude value depends on the sign of the amplitude of the quadrature baseband down-converted component; - generating a frequency sign signal whose amplitude value, or the presence or absence of oscillations in the frequency sign signal, depends on the sign of the phase difference between the first and second amplitude sign signals, and representative of the frequency sign of a baseband down-converted RF signal comprising the in-phase baseband down-converted component of the RF signal and the quadrature baseband down-converted component of the RF signal.

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