DESC:Field of the invention

The present invention generally relates to calibration systems and methods and more particularly, relates to a method of system level calibration for achieving high parameter accuracies in radio technology systems.

Background of the invention

Generally, surveillance systems require to measure parameters with high accuracies. These systems are built with many radio frequency active components, whose characteristics are temperature and frequency dependant. Hence, these characteristics need to be corrected with suitable correction factors to ensure high accuracy in parameter measurements from time to time.
One of the conventional systems discloses a calibration system for calibrating a radio frequency, RF, device comprising a plurality of signal paths, each signal path comprising at least an amplifier and an antenna element. This system has a measurement system measures a physical parameter, which is influenced by emissions on the antenna elements in response to the test signal, in front of the antenna elements as the output and provides respective measurement values. The disadvantage in this system is that the calibration with antenna means it requires emissions which is not possible all the time.
Another conventional system and method disclose a method for generating calibration signals for calibrating spatially remote signal branches of antenna systems. In this method, a base signal is generated by mean of a timer and is fed to a distributor unit for distribution of the base signal to amplifier circuits on the signal distribution lines respectively allocated to them. At the output of the amplifier circuits, a calibration signal is generated respectively via amplification of the base signal within a specifiable upper amplitude limit and a specifiable lower amplitude limit, which is fed to the respective feed-in point of the signal branch to be calibrated that is allocated to an amplifier circuit. The disadvantage is that the large amount of space required for the measuring devices, complicated and changing parameters with environmental conditions.
There is still a need of an invention which solves the above defined problems and provides a method of system level calibration for achieving high parameter accuracies in radio technology systems.

Summary of the Invention

An aspect of the present invention is to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below.
Accordingly, in one aspect of the present invention relates to an automatic system level calibration 100, the system comprising: an antenna array 110 coupled and configured to receive signals from an environment, a down-convertor 120 coupled and configured to receive each of signals of plurality of paths from the antenna array, wherein the down-convertor converts the high frequency signal to low frequency signal, a selected frequency source 130 coupled to the down convertor, wherein the selected frequency source injects an excitation signals to the down convertor for calibration, a receiver 140 coupled to receive the signals from the down convertor, wherein the receiver digitises and calibrates a parameters of the signals received from the down convertor; and a display device 150 coupled to the receiver to display parameters of the signals.

Another aspect of the present invention relates to a method of system level calibration 300, the method comprising: receiving signals from an environment by an antenna array 310, down-converting each of signals of plurality of paths received from the antenna array by a down convertor 320, injecting an excitation signals to the down convertor for calibration by a selected frequency source, wherein the selected frequency source is coupled to the down convertor 330, digitizing the received signal and measuring parameters of the received signals based on the excitation signals from the selected frequency source and a calibrated values stored in a receiver to obtain a precise signal parameters of the received signal by a receiver 340, and displaying the corrected parameters of the signals by a display module 350.
Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

Brief description of the drawings
The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:
Figure 1 shows block diagram of a surveillance system with automatic system level calibration according to an exemplary implementation of the present disclosure.
Figure 2 shows a receiver of the surveillance system according to an exemplary implementation of the present disclosure.
Figure 3 shows a method of system level calibration according to an exemplary implementation of the present disclosure.
Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.
Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

Detailed description of the invention

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces.
By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.
Figs. 1 through 3, discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way that would limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged communications system. The terms used to describe various embodiments are exemplary. It should be understood that these are provided to merely aid the understanding of the description, and that their use and definitions, in no way limit the scope of the invention. Terms first, second, and the like are used to differentiate between objects having the same terminology and are in no way intended to represent a chronological order, unless where explicitly stated otherwise. A set is defined as a non-empty set including at least one element.
The various embodiments of the present disclosure describe about a method of system level calibration for achieving high parameter accuracies in radio technology systems e.g. ultra-wide band system and a method for use in an industrial environment.
The proposed method of system level calibration overcomes the disadvantages of prior art. The system level calibration is done repeatedly without antenna at any time and the calibration set up is included within the system. Calibration is done at factory including antennae with reference point prior to installation of the system. After installation, changes need to be calibrated for measuring parameters with high accuracy. Reference point and generating calibration signals pose a challenge after installation of the system. Factory calibration techniques cannot be implemented. A Repeated calibration needs to be performed for Ultra-wide band systems for high accuracy of frequency measurement and direction finding. Calibration for frequency and direction finding is included in system for automatic system level calibration. Further, the calibration for any frequency or a band of frequencies can be chosen in ultra-wide frequency bandwidths at any time.
Calibration is done at two levels, namely factory level and system level. In factory level, antennae are calibrated in anechoic chamber and calibrated values are stored in the receiver. The errors are calculated between antennae to RF down converter and calibrated values at selected frequency are utilised at system level calibration. Thus, the errors are stored in the memory available in receiver. Antennae and antennae to RF down converter are passive elements. Repeated calibration is not necessary for passive elements. In repeated calibration, when a frequency or a band of frequencies are selected, calibration takes place from RF down converter and the calibrated values are stored in the receiver. And by using signal processing algorithms, the signal parameters are calculated with high accuracy.
Generally, surveillance systems measure pulse parameters like Frequency, pulse width, amplitude, TOA (Time of Arrival) and DOA (Direction of Arrival). The pulse parameters need to be measured with high accuracies.
Figure 1 shows a block diagram of a surveillance system with automatic system level calibration according to an exemplary implementation of the present disclosure. The ultra-wide band frequency coverage antennae are used to receive signals from the environment. The signal from antenna array is passed through a down converter and the receiver digitises the signal and measures the parameters. Calibration of the system is necessary to meet specified high accuracies. The calibration is required to balance antenna arrays and receivers.
There are several techniques that are currently used for calibration of the systems. A commonly used technique is a "factory calibration" approach. The factory calibration is utilized to measure system parameters. Moreover, the factory calibration techniques are employed prior to installation of the system. Furthermore, the technique does not consider variations that occur after the system leaves the factory. In an example, DOA and frequency accuracies are degraded over time due to thermal variations and aging in RF (Radio Frequency) components.
To overcome variation and to meet the required specifications, repeated calibration is performed after system installation. Factory calibration method cannot be performed after installation of the system. Factory calibration requires reference point and antenna emissions. To overcome these problems, repeated calibration is performed with selected frequency source excitation signal connected at the input of RF down converter.
Antenna arrays are passive components. Repeated calibration is not necessary for passive components. Once the antennae are calibrated at factory level and the calibrated values are stored in the receiver. The down converter and receiver need repeated calibration for high accuracies. Selected frequency source gives excitation signal to the down converter for a given frequency or a band of frequencies.
In one embodiment, the present invention relates to an automatic system level calibration 100, the system comprising: an antenna array 110 coupled and configured to receive signals from an environment, a down-convertor 120 coupled and configured to receive each of signals of plurality of paths from the antenna array, wherein the down-convertor converts the high frequency signal to low frequency signal, a selected frequency source 130 coupled to the down convertor, wherein the selected frequency source injects an excitation signals to the down convertor for calibration, a receiver 140 coupled to receive the signals from the down convertor, wherein the receiver digitises and calibrates a parameters of the signals received from the down convertor; and a display device 150 coupled to the receiver to display parameters of the signals.
The antenna array 110, down convertors 120 and receivers are calibrated at factory level and the calibrated values are stored in the memory of the receiver 140, wherein the calibration is performed by injecting known signal in the input of down convertor using the selected frequency source.
The RF down converter includes module for receiving signals from frequency source or from antenna arrays. The excitation signals comprises a radio frequency signals, the signal values are measured and stored in the memory in the receiver for calibrating the signal. The receiver includes digital calibration module and parameters estimation modules. The down convertor receives pre-determined excitation signals (known signal) from the selected frequency source for calibration.
The calibration is performed by measuring and correcting the parameters in the received signals based on the excitation signal calibrated values from the selected frequency source and a calibrated values stored in the receiver and outputting the corrected parameters of the received signal.
The system level calibration is done repeatedly without antenna array at any time to correct the parameters of the received signals. Further, the calibration set up is included within the system for automatic system level calibration (repeated calibration). The calibration is performed after installing (repeated calibration) the system for improving the measured parameters of the signals.
The amplitude based direction finding calibration comprises adjusting amplitude differences through the signal path from down converter to the receiver using an excitation signal from the selected frequency source and the calibrated values stored in the receiver. The phase based direction finding calibration comprises adjusting phase differences through the signal path from down converter to the receiver using an excitation signal from the selected frequency source and the calibrated values stored in the receiver.
In the present invention, the repeated calibration is done for improving direction finding and frequency accuracies. It can be applied for any method such as amplitude based Direction finding or Phase based Direction finding. The calibration process takes only few microseconds for a particular excitation signal. The repeated calibration is performed for one or a band of signals and the calibration is performed for any one of the parameters of the signals.
Figure 2 shows a receiver of the surveillance system according to an exemplary implementation of the present disclosure. The figure explains detailed calibration in the receiver. When a particular frequency is selected on the display, the automatic system level calibration is initiated, and the calibrated values are measured and stored in the memory of receiver. System parameters are measured with high accuracy and presented on the display.
Surveillance system set up includes automatic system level calibration. Once Calibration is completed at factory level including antenna arrays. After installation of the system repeated calibration is performed without antenna arrays. Repeated Calibration can be completed for a wide band within few microseconds to improve accuracies of system parameters.
The down converted signal is digitized in the receiver. When the known excitation signal is sent to down converter, the signal values are measured and stored in a memory in the receiver for calibrating the signal. When the environment signal is received from the antenna, the signal values are measured and corrected/calibrated with the stored values in the receiver. These corrected values represent the actual signal parameters and sent to the display console.
Figure 3 shows a method of system level calibration according to an exemplary implementation of the present disclosure.
The figure shows a method of system level calibration. The method comprises few steps: receiving signals from an environment by an antenna array 310, down-converting each of signals of plurality of paths received from the antenna array by a down convertor 320, injecting an excitation signals to the down convertor for calibration by a selected frequency source, wherein the selected frequency source is coupled to the down convertor 330, digitizing the received signal and measuring and correcting a parameters of the received signals based on the excitation signals from the selected frequency source and a calibrated values stored in a receiver to obtain a precise signal parameters of the received signal as a corrected signal by the receiver, where the parameters are corrected against the calibrated values stored in the receiver and displaying the corrected parameters of the signals by a display module 350.
The antenna array 110 and down convertors 120 are calibrated at factory level and the calibrated values are stored in the memory of the receiver 140, wherein the repeated calibration is performed by injecting known signal in the input of down convertor using the selected frequency source.
The calibration is performed by measuring the parameters in the received signals based on the excitation signal calibrated values from the selected frequency source and a calibrated values stored in a receiver and outputting the corrected parameters of the received signal.
Those skilled in this technology can make various alterations and modifications without departing from the scope and spirit of the invention. Therefore, the scope of the invention shall be defined and protected by the following claims and their equivalents.
FIGS. 1-3 are merely representational and are not drawn to scale. Certain portions thereof may be exaggerated, while others may be minimized. FIGS. 1-3 illustrate various embodiments of the invention that can be understood and appropriately carried out by those of ordinary skill in the art.
In the foregoing detailed description of embodiments of the invention, various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments of the invention require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus, the following claims are hereby incorporated into the detailed description of embodiments of the invention, with each claim standing on its own as a separate embodiment.
It is understood that the above description is intended to be illustrative, and not restrictive. It is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined in the appended claims. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein,” respectively.

,CLAIMS:

1. An automatic system level calibration 100, the system comprising:
an antenna array 110 coupled and configured to receive signals from an environment;
a down-convertor 120 coupled and configured to receive each of signals of plurality of paths from the antenna array, wherein the down-convertor converts the high frequency signal to low frequency signal;
a selected frequency source 130 coupled to the down convertor, wherein the selected frequency source injects an excitation signals to the down convertor for calibration;
a receiver 140 coupled to receive the signals from the down convertor, wherein the receiver digitises and calibrates a parameters of the signals received from the down convertor; and
a display device 150 coupled to the receiver to display parameters of the signals.

2. The system as claimed in claim 1, wherein the antenna array 110 and down convertors 120 are calibrated at factory level and the calibrated values are stored in the memory of the receiver 140.

3. The system as claimed in claim 1, wherein the excitation signals (known signal) comprises a radio frequency signals, the signal values are measured and stored in the memory in the receiver for calibrating the signal.

4. The system as claimed in claim 1, wherein the calibration is performed by measuring and correcting the parameters in the received signals based on the excitation signal calibrated values from the selected frequency source and a calibrated values stored in the receiver and outputting the corrected parameters of the received signal.

5. The system as claimed in claim 1, wherein the system level calibration is done repeatedly without antenna array at any time to correct the parameters of the received signals.

6. The system as claimed in claim 1, wherein the calibration set up is included within the system for automatic system level calibration (repeated calibration).

7. The system as claimed in claim 1, wherein the calibration is performed after installing (repeated calibration) the system for improving the parameters of the signals.

8. The system as claimed in claim 1, wherein the amplitude based direction finding calibration comprises adjusting amplitude differences through the signal path from down converter to the receiver using an excitation signal from the selected frequency source and the calibrated values stored in the receiver.

9. The system as claimed in claim 1, wherein the phase based direction finding calibration comprises adjusting phase differences through the signal path from down converter to the receiver using an excitation signal from the selected frequency source and the calibrated values stored in the receiver.

10. The system as claimed in claim 1, wherein the repeated calibration is performed for one or a band of signals and the calibration is performed for any one of the parameters of the signals.

11. A method of system level calibration 300, the method comprising:
receiving signals from an environment by an antenna array 310;
down-converting each of signals of plurality of paths received from the antenna array by a down convertor 320;
injecting an excitation signals to the down convertor for calibration by a selected frequency source, wherein the selected frequency source is coupled to the down convertor 330;
digitizing the received signal and measuring parameters of the received signals based on the excitation signals from the selected frequency source and a calibrated values stored in a receiver to obtain a precise signal parameters of the received signal; and
displaying the corrected parameters of the signals by a display module 350.

12. The method as claimed in claim 11, wherein the antenna array 110 and down convertors 120 are calibrated at factory level and the calibrated values are stored in the memory of the receiver 140, wherein the repeated calibration is performed by injecting known signal in the input of down convertor using the selected frequency source.

13. The method as claimed in claim 11, the calibration is performed by measuring and correcting the parameters in the received signals based on the excitation signal calibrated values from the selected frequency source and a calibrated values stored in the receiver and outputting the corrected parameters of the received signal.