GB2484305A

GB2484305A - Dual frequency radar

Info

Publication number: GB2484305A
Application number: GB201016769A
Authority: GB
Inventors: Robert Pitman
Original assignee: Thales Holdings UK PLC
Current assignee: Thales Holdings UK PLC
Priority date: 2010-10-05
Filing date: 2010-10-05
Publication date: 2012-04-11
Also published as: GB201016769D0

Abstract

An intermodulation radar system comprises means simultaneously transmitting two signals whose frequencies f1 & f2 are sufficiently close (frequency difference 1 Hz to 100 kHz) that a single receiver can receive both after they have been reflected. The two received signals are mixed, and a difference signal or a higher order intermodulation signal (2 f2 f1 or 3 f2 2 f1) is obtained and processed digitally.

Description

I

INTERMODULATION RADAR SYSTEM

Embodiments described herein relate generally to an intermodulation radar system.

In typical intermodulation radar systems, two radio frequency (RF) receivers are required. This imposes limitations on such systems in terms of size weight, power consumption, complexity and cost. Further, if a system furnished with two RF receivers is required to compare the signal strengths between two intermodulation signals, then the gain of both RF receivers will need to be known.

An aspect of the invention provides an intermodulation radar system comprising transmitting means for transmitting two radio frequency, RF, signals and receiving means for receiving reflected RF artefacts of such signals, the transmitting means being so configured that a single receiving means is capable of receiving intermodulation artefacts of both sighals.

Another aspect of the invention provides a method of conducting intermodulation radar comprising transmitting two radio frequency, RF, signals and receiving reflected RF artefacts of such signals, such that a single act of receiving comprises receiving intermodulation artefacts of both signals.

Since the arrangement can operate with only one RF receiver collecting two RF signals, certain embodiments thereof can benefit, in comparison with previously described examples using two RF receivers, with regard to at least one of size, weight power consumption, complexity and cost.

In certain embodiments, amplitude and phase information of the two received signals is preserved. This can only be achieved in examples using two RF receivers, by ensuring that the receivers are amplitude and phase calibrated, which imposes a complexity constraint on such arrangements.

Further aspects, features, advantages and effects of the invention may be ascertained from the following description of an embodiment thereof (provided by way of example only), with reference to the accompanying drawing.

Figure 1 illustrates schematically a single receiver intermodulation radar system in accordance with an embodiment of the invention.

In figure, 1, a radar system 10 comprises two signal generators 12 each driving an RF transmit antenna 14. The resultant transmitted RF signals are marked t1 and t2 respectively.

The transmitted RF signals t1 and t2 are illustrated as being incident on a target 20.

The signals are reflected, at least in part towards an RF receive antenna 30. The components of the reflected signals directed towards the RF receive antenna 30 are marked r1 and r2 in figure 1.

The RF receive antenna 30 passes an electrical signal resultant from the incident reflected signals r1 and r2 to a receiver 40. The receiver 40 will now be described in terms of its function -its structure will be apparent from this and a skilled reader will be able to devise a suitable structure to deliver the function based on knowledge of the art.

For the purpose of this example, it is anticipated that the receiver 40 will include a Digital Signal Processor (DSP) for signal processing functionality.

The two transmission frequencies at which the respective signal generators 12 generate signals are arranged such that the two intermodulation signals generated by the target 30 are separated by a small frequency difference (in the order of a few Hz to a few tens of kHz). This permits a narrow bandwidth RF receiver to collect the two signals. The Digital Signal Processor (DSP) in the receiver 40 is used to analyse the two signals (by measurement of frequency, amplitude and phase).

The two interrnodulation signals can be represented as: r2 This assumes that t > which is the frequency difference between second order and third order intermodulation signals, and which will be in the order of tens of kI-iz, can be detected from the received signal, using standard signal processing techniques, and is: A1 =k -iI=2xti -3xt21 This frequency difference is thus relatively small, and permits a narrow bandwidth RF receiver to collect the two signals.

While the above embodiment has been described, both in general and specific terms, in the context of a DSP implementation, it will be appreciated that this is but one of many different implementations possible.

The reader will appreciate, for instance, that a software implemented solution, operable to cause configuration of general purpose equipment to operate in accordance with an embodiment of the invention, is also possible. Alternatively, application specific hardware could be designed to achieve the same end result.

While a specific embodiment has been described, this embodiment has been presented by way of example only, and is not intended to limit the scope of the invention. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit and scope of the invention. The accompanying claims and their equivalents are intended to cover such forms and modifications as would fall within the scope and sprit of the inventions. The claims may be read in the light of the foregoing description and appended drawing, but may not be specifically limited thereby.

Claims

CLAIMS: 1. An intermodulation radar system comprising transmitting means for transmitting two radio frequency, RF, signals and receiving means for receiving reflected RF artefacts of such signals, the transmitting means being so configured that a single receiving means is capable of receiving intermodulation artefacts of both signals.
2. A system in accordance with claim 1 wherein the transmitting means comprises two RF transmitters, each operable to transmit an RF signal at a given frequency, the transmitters being operable to transmit at frequencies such that reflected intermodulation artefacts thereof are spaced in the frequency domain sufficiently closely that they can be detected by said single receiving means.
3. A system in accordance with claim 2 wherein said transmitters are operable to transmit at frequencies spaced apart by an amount in the range of 1 Hz to 100kHz.
4. A system in accordance with any one of the preceding claims wherein said receiving means is operable to determine from a signal received thereby a difference between secondary and tertiary order intermodulation peaks on said signal.
5. A method of conducting intermodulation radar comprising transmitting two radio frequency, RF, signals and receiving reflected RF artefacts of such signals, such that a single act of receiving comprises receiving intermodulation artefacts of both signals.
6. A method in accordance with claim 5 wherein the transmitting comprises two transmitting two RF signal at given frequencies, the transmit frequencies being such that reflected intermodulation artefacts thereof are spaced in the frequency domain sufficiently closely that they can be detected in said single act of receiving.
7. A method in accordance with claim 6 wherein said transmitting is at frequencies spaced apart by an amount in the range of 1 Hz to 100kHz.
8. A method in accordance with any one of claims 5 to 7 wherein said receiving comprises determining from a received signal a difference between secondary and tertiary order intermodulation peaks on said signal.