DEVICE FOR CONTROLLING AN ACTIVE ANTENNA WITH SAMPLING

Description

[0001] The invention relates to a device enabling the control of an ultra-fast scanning active antenna, high-efficiency and self-protected from disturbances such as coupling effects related to the antenna array, and / or mismatch effects related to Radio Frequency circuits.

[0002] The invention applies to all active antenna networks, therefore to all types of means of communication using such antennas, microwave links, cellular networks (5G) and any other means of high-frequency communication, for example in a frequency range above a few GHz.

[0003] The principle of active antennas is based on the use of an array of antennas in which each active element is controlled in phase and amplitude in order to form a beam.

[0004] In the applicant's prior art, the amplitude of each active antenna element is controlled at the input by an attenuator. The active element is thus configured to generate peak power across all the antenna elements in the antenna array. To manage beamforming, not all antenna elements are programmed at their maximum power; the programming depends on the desired viewing angle. When an active element is configured to generate its maximum power but with reduced control, its efficiency drops significantly. This leads to a rather poor electrical efficiency of the active antennas. To compensate for this inefficiency, more energy than necessary is used for the active elements. This proves to be a limiting factor in most antenna applications, which are increasingly integrated into devices.

[0005] The principle of active antennas illustrated at the figure 1 is based on an antenna array comprising n transmission channels Txi, where i = 1, ..., n. Each transmission channel Txi comprises a resistive element 1i, a phase control module 2i, and a power transistor 3i, at the output of which is a radiating element Ei, or active antenna element. Each active element Ei is controlled in phase and amplitude to form the beams. The active elements (radiating elements) are positioned very close to each other. The mutual impedance of all the radiating elements can lead to mismatches in some of them, potentially resulting in premature aging or even the destruction of their power amplifier.

[0006] Another solution is to install 4i attenuators ( figure 1 ) at the output of a 3i power transistor to protect the power chains.

[0007] Electrical efficiency becomes a concern when integrating active antenna arrays. US20190089070A1 describes a method for separate polarization of a power amplifier for power control. WO2019158207 A1 describes a method providing individual antenna configuration selections within a MIMO antenna array.

[0008] The idea of ​​the present invention is to propose a system in which the phase control of the antenna elements is preserved, the management of the amplitude of each active element is carried out at the level of the voltage of the power element disposed at the output of the system, using an envelope tracking technique instead of managing this envelope via attenuators disposed upstream of the power stage, a technique usually used in the prior art.

[0009] The invention is defined by the independent claim. Embodiments are described in the dependent claims. More generally, the invention relates to a control device for a swept active antenna comprising at least two transmission channels Txi, each transmission channel comprising a phase control module, a power stage at the output of which is disposed a radiating element characterized in that it comprises at least: A voltage modulator located upstream of the power stage of each of the radiating elements, A control device configured to emit a drain voltage PWM control signal configured to manage the gain of a power stage according to a predefined first bias law and to control the phase applied to the drain of the power stage according to a given second bias law.

[0010] The power stage is, for example, a power transistor, the modulator being adapted to handle the drain voltage of the power transistor.

[0011] The first bias law to manage the gain of a stage and the second bias law for phase control are defined during system calibration.

[0012] The control signal is, for example, determined by taking into account the calculation of altitude and azimuth of the desired radiation at the antenna level.

[0013] The radiating elements can be configured to operate in frequency bands above 800 MHz.

[0014] The radiating elements are, for example, configured to operate in the 4G / 5G communications domain.

[0015] Other features, details and advantages of the invention will become apparent from the description provided with reference to the accompanying drawings, which are given by way of non-limiting example and represent, respectively: There figure 1 , an example of architecture according to earlier art, The figure 2 , an example of a system according to the invention, The figure 3 , an example of an amplifier bias law, which allows its gain to be managed as a function of the drain voltage and a bias law for phase control as a function of the drain voltage.

[0016] Active antenna systems use uniformly distributed active modules, each of which includes a microwave power amplifier (HPA) used for transmission. Each active module emits a portion of the power required by the antenna system to achieve a given range. The summation of the different transmission sources is performed coherently at the level of an array antenna comprising a large number of sources. Since the active modules are all identical, the aim is generally to optimize efficiency and range by operating the power amplifiers in saturation mode, that is, at maximum power.

[0017] The idea behind the present invention is to integrate a voltage modulator directly into the power stage of each active cell in the antenna array. The voltage modulator's function is, in particular, to manage the transmit power of each active element at the drain voltage of the power transistor, thereby achieving optimal unit efficiency and, consequently, optimal overall efficiency of the antenna array. The corollary effect is to increase the efficiency of each amplifier when they are used below their saturation power, and thus reduce the overall power consumption of the active antenna compared to current state-of-the-art designs. Furthermore, using a very fast voltage modulator, such as the one disclosed in patent application WO2020016305, allows for faster gain control of the power amplifiers, by a factor of at least 100 compared to current state-of-the-art designs.This enables additional features for the active antenna, such as dynamic target tracking, or instant communication with two different targets.

[0018] There figure 2 illustrates an example of architecture according to the invention, in which the elements of the figure 2 common to those of the system described in the figure 1 they carry the same references.

[0019] The system comprises a set of n active antenna elements: E i = E 1 , ...E n .

[0020] A Txi transmission chain includes a phase adjustment device 2 i positioned upstream of an amplifier 3 i itself located upstream of an active antenna element.

[0021] A high-speed drain voltage modulation (DVM) device (5i) is connected to the output amplifier (3i). A PWM control signal generated by a control device (10) is sent to this DVM device to manage the gain of the output amplifier, thereby improving the pointing of the active antenna. The control device is also configured to control the phase applied to the amplifier's drain. The speed of the drain voltage control system allows the antenna to be reconfigured much faster (at least 10 times) than known prior art systems.

[0022] There figure 3 gives an example of biasing laws implemented by the control device 10. A biasing law of the amplifier ( figure 3 ) is implemented in a programmable logic circuit of the FPGA (Field Programmable Gate Array) type or an ASIC (Application-Specific Integrated Circuit) type. The bias law is extracted during the calibration of the antenna system and allows the gain G of the amplifier to be precisely determined as a function of the drain voltage Vds applied to it ( figure 3 Curve 31 corresponds to the biasing law, which controls the amplifier's gain G as a function of the drain voltage, while curve 32 controls the phase Φ as a function of the power amplifier's drain voltage Vds. The goal is to maintain a phase variation of less than 5° to ensure proper antenna control.

[0023] This new method of controlling the output power of a power amplifier by varying its gain through the applied drain voltage is not used in the state of the art. Typically, the output power of each amplifier is set according to the input power applied to it.

[0024] The extracted polarization law is used to calculate the drain voltage to be applied to each power amplifier constituting the active antenna for a given antenna azimuth and altitude configuration.

[0025] An analog PWM signal carrying the voltage information to be applied to each amplifier is sent to the drain voltage modulation circuit. This signal is calculated based on the altitude and azimuth of the desired antenna radiation pattern.

[0026] The self-protection circuit described in patent FR3134972 can be positioned at the output of each power amplifier to protect each element from excessive mismatch. This circuit can be coupled to the new, very fast active antenna architecture.

[0027] The invention finds its application in the field of active antennas operating in frequency bands above 800 MHz, Satcom, 4G / 5G networks, etc.

[0028] Prior art uses fixed bias on each amplifier, resulting in reduced power consumption when they are not used at full power. By using the method according to the invention, the system benefits in two ways: reduced power consumption when the amplifiers are used below their maximum power, and a more directional radiation pattern thanks to amplitude optimization on each amplifier. The use of this new architecture also allows for much faster antenna pointing / unpointing (at least ten times faster). This enables much more efficient target tracking and also opens the possibility of tracking and interacting with multiple targets almost instantaneously.

Claims

1. Active antenna with scanning system comprising at least two transmission paths (Txi), a transmission path comprising a phase control module (2i), and an amplifier (3i) at the output of which a radiating element (Ei) of the antenna system is disposed, the antenna system being characterized in that a transmission path comprises, in addition, at least one drain voltage modulator (5i) to modulate the drain voltage of the amplifier (3i), - a device (10) for controlling the antenna system transmitting control signals by pulse width modulation (PWM), determined by considering the calculation of altitude and azimuth of the radiation sought at the antenna, such that the drain voltage modulators manage the gain of the amplifiers according to a first predefined polarization law (31), the phase applied on the drain of the power stage being controlled according to a second polarization law (32).

2. Antenna system according to claim 1, characterized in that the amplifier is a power transistor, said modulator being adapted to manage the drain voltage of the power transistor.

3. Antenna system according to any one of claims 1 or 2, characterized in that the first polarization law for managing the gain and the second polarization law for phase control are defined during a calibration of said antenna system.

4. Antenna system according to any one of claims 1 to 3, characterized in that the antenna elements are configured to operate in frequency bands above 800MHz.

5. Antenna system according to any one of claims 1 to 3, characterized in that the antenna elements are configured to operate in the 4G / 5G communication field.