Electronic generator of pulsed signals under modulated carrier and associated radio frequency signal transmitter

Abstract

Electronic generator of pulse signals under modulated carrier and associated radio frequency signal transmitter This electronic generator of pulse signals under modulated carrier includes a module (15) for modulating a pulse train whose position and amplitude are controllable, forming a switching signal (S3); a switching module (16), connected at the output of the pulse train modulation module (15), comprising at least one transistor (22), controlled by said switching signal (S3); a voltage-controlled frequency-locked oscillation module (18), having a frequency-locked band around a free oscillation frequency controlled by a control voltage, connected at the output of the switching module (16); the switching module allowing the injection of a periodic pulse signal (S4) having a frequency spectrum comprising at least one frequency line in said frequency-locked band.This arrangement allows the output of the oscillation module to produce pulsed signals (S5) with a modulated carrier controlled in frequency, phase, and amplitude. See Figure 1 for abbreviations.

Description

Title of the invention: Electronic generator of pulse signals under modulated carrier and associated radiofrequency signal transmitter

[0001] The present invention relates to an electronic generator of pulsed signals under modulated carrier and an associated radiofrequency signal transmitter.

[0002] The invention lies in the field of generating ultra-wideband pulsed signals under phase and amplitude modulated carrier.

[0003] It finds numerous applications, in particular in high-speed telecommunications, in low-power telecommunications, in particular in low-power pulse radars, in the field of object location, in the field of self-powered sensors, in the field of radiofrequency sensors.

[0004] In the state of the art, ultra-wideband pulse modulation systems are known, in particular using pulse position modulation or PPM (for "Pulse Position Modulation" in English), on-off amplitude modulation OOK (for "On Off Keying" in English), QAM vector modulations (for "quadrature amplitude modulation") or a combination of these modulations. QAM vector modulations, such as BPSK modulation (for "❖Binary phase-shift keying" in English) for example, require the generation of a reference signal, the carrier, with significant constraints in terms of phase noise. One of the limitations of these pulse vector modulation techniques lies, among other things, in the complexity and the electrical consumption of the blocks for generating the reference signal, the carrier, and of the modulation blocks.

[0005] Most direct generators of ultra-wideband pulsed signals synthesize the carrier frequency using a phase-locked loop (PLL) block, which is an electronic device for controlling the output phase or frequency as a function of the phase or frequency of a reference input signal. This synthesized signal requires complex modulation blocks to ensure the generation of a pulse envelope signal with vector modulation. To synthesize high carrier frequencies, of several tens of GHz, it is necessary to develop complex PLLs with significant power consumption and size. In addition, one of the objectives to be achieved is to reduce the phase noise of the output signals.

[0006] The object of the invention is to remedy the aforementioned drawbacks of the state of the art.

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[0013] To this end, the invention proposes, according to one aspect, an electronic generator of pulsed signals under modulated carrier comprising: - a module for modulating a pulse train whose position and amplitude are controllable, forming a switching signal; - a switching module, connected to the output of the pulse train modulation module, comprising at least one transistor, the switching of which is controlled by said switching signal, - a voltage-controlled frequency-locked oscillation module, having a frequency-locked band around a free oscillation frequency controlled by a control voltage, the oscillation module being connected to the output of the switching module, the switching module allowing the injection of a periodic pulse signal into the oscillation module, - the periodic pulse signal having a frequency spectrum comprising at least one frequency line in said frequency locking band, the arrangement of said modules making it possible to obtain at the output of the oscillation module pulse signals under modulated carrier controlled in frequency, phase and amplitude. Advantageously, the proposed generator makes it possible to achieve direct generation of pulsed signals under modulated carrier, locked by pulsed injection, controlled in frequency, phase, amplitude and pulse width, without using a phase-locked loop. The electronic generator of pulsed signals under modulated carrier according to the invention may also have one or more of the characteristics below, taken independently or in all technically conceivable combinations. The module for modulating a pulse train comprises a generator of periodically repeated pulses forming an input signal, connected to the input of a delay module configured to introduce programmable delays so as to generate a position-modulated signal, said position-modulated signal being provided as the input of a switching signal generation module, controlled by a voltage signal. The pulse signals under modulated carrier are further pulse width controlled as a function of said input signal. The delay module configured to introduce programmable delays is a voltage-to-time or current-to-time converter module. The switching signal generation module comprises at least one component for amplifying electrical signals with very short switching time, amplitude controlled by said voltage signal.

[0014] The switching signal generation module comprises a number N of transistor inverters connected in series.

[0015] Each of said modulation module, switching module and oscillation module is implemented in the form of CMOS components.

[0016] According to another aspect, the invention relates to a radiofrequency signal transmitter comprising an electronic generator of pulse signals under modulated carrier as briefly introduced and a transmission antenna connected to said electronic generator of pulse signals under modulated carrier. According to one characteristic, the radiofrequency signal transmitter further comprises a power amplifier connected between the output of said electronic generator of pulse signals under modulated carrier and said transmission antenna.

[0017] Other characteristics and advantages of the invention will emerge from the description given below, for information purposes only and in no way limiting, with reference to the appended figures, among which:

[0018] [Fig-1] [Fig.l] is a block diagram of a radio frequency signal transmitter comprising an electronic generator of pulse signals under modulated carrier according to one embodiment of the invention;

[0019] [Fig.2] [Fig.2] schematically represents a signal waveform im generated undercarrier impulse;

[0020] [Fig.3] [Fig.3] schematically represents an embodiment of an electronic generator of pulse signals under modulated carrier.

[0021] [Fig.l] schematically represents a radiofrequency signal transmitter 2 comprising an electronic generator 4 of pulse signals under modulated carrier, the input of which is connected to a pulse generator 6 and the output of which is connected to a power amplifier 8 and to a transmission antenna 10.

[0022] The power amplifier is optional, it may not be present in alternative embodiments.

[0023] According to a variant, the pulse generator 6 is integrated into the electronic generator 4 of pulse signals under modulated carrier.

[0024] The pulse generator 6 provides a periodic input signal Si formed of periodically repeated pulse trains, with a pulse repetition period PRP=1 / PRF where PRF is the pulse repetition frequency.

[0025] The electronic generator 4 of pulse signals under modulated carrier, called generator 4 hereinafter, comprises: - a module 15 module for modulating a pulse train forming a switching signal S3, the position and amplitude of which are controllable; the module 15 comprises, in the illustrated embodiment, a delay module 12 configured to introduce programmable delays on the input signal Sb generating at output a modulated signal in position S2, and a module 14 for generating switching signals, of voltage amplitude controlled by a signal VAm, receiving at input the modulated signal in position S2 - a switching module 16, connected to the output of the module 15, comprising at least one transistor, the switching of which is controlled by the switching signal S3, the switching module 16 allowing the injection, at the input of an oscillator 18, of a signal composed of the modulated periodic pulse signal S4; - an oscillation module 18 (or oscillator), having a free oscillation frequency controlled by a control voltage VT, connected to the output of the switching module 16. Such an oscillator is also known as a VCO (for “Voltage-Controlled Oscillator”). The oscillator 18 has a frequency locking band around its free oscillation frequency.

[0026] The modulated periodic pulse signal S4 has a frequency spectrum comprising at least one frequency line in the frequency locking band of the oscillator 18.

[0027] Thus, advantageously, the switching times in the switching module 16, controlled by the module 14, ensure the shortest possible transitions in order to generate a spectrum of lines of which at least one of the lines is present with sufficient energy to ensure locking in the frequency locking band of the oscillator 18.

[0028] At the output of the oscillator 18, pulse signals under carrier S5 are obtained, comprising the following characteristics: • a relative phase controlled by the delay signal r of module 12, • an amplitude controlled by the VAm signal from module 14, • a locking frequency and a phase controlled by the VT signal of the oscillator, • a pulse width controlled by the pulse signal of the input signal Sp

[0029] The arrangement of said modules makes it possible to obtain pulse signals under modulated carrier, controlled in frequency, position (or phase), width and amplitude.

[0030] [Fig.2] illustrates an example of a carrier pulse signal as a function of time. In other words, [Fig.2] illustrates an example of a generated waveform.

[0031] The pulse signal S5 under modulated carrier is characterized by:

[0032] -its power Pout, or indirectly its amplitude,

[0033] -its central frequency Foqui is an integer submultiple of the pulse repetition frequency of the signal Si,

[0034] -the phase relative to the previous pulse q>0,

[0035] -the width at mid-height of the envelope Tw,

[0036] -the PRP repetition period.

[0037] [Fig. 3] illustrates an embodiment of a generator 6, in which the modules 12, 14, 16, 18 are implemented with electronic components according to CMOS technology (for “Complementary Metal Oxide Semi-Conductor”).

[0038] Module 12 is adapted to introduce programmable delays rm(t).

[0039] In the illustrated embodiment, the module 12 is produced by a delay circuit which performs a voltage-time conversion, from the voltage signal Vin, for example implemented using a “shunt” capacitor circuit.

[0040] Of course, any other controllable delay circuit can be used, for example a current starved delay circuit, or a variable resistance circuit.

[0041] The delay signals act as control signals allowing the start time of the oscillator 18 to be defined with great granularity.

[0042] In one embodiment, the delay module 12 is controlled by three delay signals (or control signals), corresponding respectively to phase shifts of 45°, 90° and 180° for a sinusoidal reference signal, for example of frequency equal to 60 GHz.

[0043] At the output of the delay module 12, a position-modulated (PPM) signal S2 is obtained, which results in a phase modulation in the modulated carrier pulse signal S5.

[0044] The signal S2 is transmitted to the input of the module 14 for generating switching signals S3, the amplitude of the output signal of this module being controlled by a voltage VAm-

[0045] In one embodiment, the module 14 is made by a number N of inverters connected in series, N being equal to 3 in the example. The module 14 comprises N=3 inverters 14i, 142 and 143 with transistors, which have the advantage of having short switching times, for example less than 10 picoseconds in 65nm SOI CMOS technology.

[0046] The transistors of the inverters 14b 142 and 143 are sized as a function of the frequency locking band of the oscillator 18 and the free oscillation frequency of the oscillator 18, in order to allow the switching of the module 16, on the rising edge, with the shortest possible switching time. For example, the switching time of the module 16 is less than 10 picoseconds for a free oscillation frequency of 60 GHz.

[0047] Indeed, the use of a number N of inverters in series makes it possible asymptotically to obtain the shortest transition times, and more particularly the shortest rise times.

[0048] If the number N of inverters is even, the pulse signal S5 at the output of the generator 6 starts on a rising edge of the input signal Sp If the number N of inverters is odd, the pulse signal S5 at the output of the generator 6 starts on a falling edge of the input signal Sp

[0049] The switching signal S3 obtained at the output of the module 14 is supplied at the input of the switching module 16, which performs switching between a blocked mode (“off”) and a passing mode (“on”).

[0050] When the switching signal S3 is in the low state (0V by convention), no current flows in the module 16. When the switching signal S3 goes to the high state (voltage equal to VAm by convention), the module 16 becomes conducting, a current flows towards the oscillation module 18. This current comprises the amplitude-controlled pulse current, denoted S4 rich in harmonics of the input signal Sp

[0051] In the embodiment of [Fig.3], the switching module 16 is composed of a transistor 22. More generally, the switching module 16 comprises at least one transistor.

[0052] The control voltage on the gate of transistor 22 makes it possible to control the current injected into the main branch of oscillator 18, and thus to control the output power of this oscillator and to promote injection locking.

[0053] The supply voltage VAm of the module 14 makes it possible to control the control voltage on the gate of the transistor 22. Thus, the supply voltage VAm makes it possible to control the output power of this oscillator.

[0054] The oscillator 18 comprises variable capacitance diodes 24, 26, also called varactor or varicap diodes, driven by the control voltage VT, a field effect transistor 28 and a capacitor 30.

[0055] The free oscillation frequency fO of the oscillator 18 is a function of the control voltage VT. A modulation of the applied voltage around the control voltage modifies the instantaneous phase of the output center frequency. For example, in an exemplary implementation, the center average frequency is between 55 and 65 GHz.

[0056] The pulse signal S4 and the control voltage VT make it possible to lock the output frequency of the oscillator 18 to an integer multiple of the frequency of the input signal Si. This phenomenon is known as injection locking of an oscillator.

[0057] An oscillator of this type starts from a low energy coming from a harmonic component present in its AF frequency locking band, close to its

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[0071] free oscillation frequency f0. The locking phenomenon is transient and strongly depends on the external quality coefficient of the oscillator Qext, the power of the oscillator Posc and the power of the injected signal S4, noted Pinj. The locking band is defined by Adler's formula: During ignition, in transient mode, the two powers Posc(t) and Pinj(t) are functions of time. Initially, the oscillator power Posc(t) is much lower than the injected signal power, Pinj(t), and the locking band is large. In steady state, the oscillator power Posc(t) is greater than the injected signal power, Pinj(t), the locking band decreases. In order to ensure that the oscillator is locked, in other words to ensure the presence of a harmonic component in the oscillator locking band, the control voltage VT is applied to modulate the frequency f0. Advantageously, the electrical energy consumption of an electronic generator of pulsed signals under modulated carrier as described is low. When the oscillator is not in operation, only a leakage current, of low amplitude, flows. When CMOS technology is used, the generator's power consumption is a function of the pulse repetition rate and the oscillator's power consumption. For example, for a peak transmission power of Pout=10mW (10dBm) and an energy efficiency q=20% (i.e. a static oscillator consumption of 50 mW), if the RF pulse is switched on for TON=500 ps (i.e. 30 periods for a 60 GHz carrier and an occupied bandwidth of 4 GHz), the energy consumed per RF pulse is 50 mWx300 ps=15 pJ. Advantageously, the invention allows rapid and time-controlled ignition of an oscillation module using pulses with short transition times. Advantageously, the programmable delay introduced makes it possible to determine the start time of the oscillator. Advantageously, in the described electronic generator of pulsed signals under carrier, the initial starting conditions of the oscillator, in particular the starting time, are determined before the frequency synthesis. Advantageously, the applied control voltage VT makes it possible to control the phase when starting the oscillator. Advantageously, the electronic generator of pulse signals under modulated carrier makes it possible to carry out modulation in n-PSK phase, in n-AM amplitude and / or joint phase and amplitude n-QAM, with a number of phase states for example between 2 and 16.

Claims

Claims

1. Electronic generator of pulse signals under modulated carrier, characterized in that it comprises - a module (15) for modulating a pulse train whose position and amplitude are controllable, forming a switching signal (S3); - a switching module (16), connected to the output of the module (15) for modulating a pulse train, comprising at least one transistor (22), the switching of which is controlled by said switching signal (S3), - an oscillation module (18) with voltage-controlled frequency locking, having a frequency locking band around a free oscillation frequency controlled by a control voltage, the oscillation module (18) being connected to the output of the switching module (16), the switching module allowing the injection of a periodic pulse signal (S4) into the oscillation module (18),- the periodic pulse signal (S4) having a frequency spectrum comprising at least one frequency line in said frequency locking band, the arrangement of said modules making it possible to obtain at the output of the oscillation module (18) pulse signals (S5) under modulated carrier controlled in frequency, phase and amplitude.,

2. Generator according to claim 1, in which the module (15) for modulating a pulse train comprises a generator (6) of periodically repeated pulses forming an input signal (Si), connected to the input of a delay module (12) configured to introduce programmable delays so as to generate a position-modulated signal (S2), said position-modulated signal (S2) being supplied to the input of a module (14) for generating switching signals (S3), controlled by a voltage signal (VAm)-

3. Generator according to claim 2, wherein said pulse signals (S5) under modulated carrier are further controlled in pulse width as a function of said input signal (Si).

4. A generator according to any one of claims 1 to 3, wherein the delay module (12) configured to introduce programmable delays is a voltage-to-time or current-to-time converter module.

5. Generator according to any one of claims 1 to 4, in which the module (14) for generating switching signals (S3) comprises at least one component for amplifying electrical signals with very short switching time, with an amplitude controlled by said voltage signal (VAm)-

6. Generator according to claim 5, wherein said switching signal generation module (14) comprises a number N of transistor inverters (14b 142, 143) connected in series.

7. An electronic generator according to any one of claims 1 to 6, wherein each of said modulation module (15), switching module (16) and oscillation module (18) is implemented as CMOS components.

8. Radiofrequency signal transmitter comprising an electronic generator of pulse signals under modulated carrier (4) according to claims 1 to 7 and a transmission antenna (10) connected to said electronic generator of pulse signals under modulated carrier (4).

9. A radio frequency signal transmitter according to claim 8, further comprising a power amplifier (8) connected between the output of said electronic modulated carrier pulse signal generator (4) and said transmitting antenna (10).

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