Radar Apparatus

Abstract

A radar apparatus includes a signal generation unit and a temperature sensing means. The signal generation unit is arranged to generate radar signals at an output power and has an output for the radar signals. The temperature sensing means has an output and is arranged to produce an output signal indicative of a temperature of at least part of the radar apparatus. The output of the temperature sensor is coupled to the signal generation unit. The signal generation unit is configured so the output power is a first power when the output signal is indicative of a temperature within a first temperature range and is a second power lower than the first power when the output signal is indicative of a temperature within a second temperature range higher than the first temperature range.

Claims

1. A radar apparatus, comprising: a signal generation unit arranged to generate radar signals at an output power, the signal generation unit having an output for the radar signals, a temperature sensor having an output and arranged to produce at its output an output signal indicative of a temperature of at least part of the radar apparatus, the output of the temperature sensor being coupled to the signal generation unit, in which the signal generation unit is configured so the output power is a first power when the output signal is indicative of a temperature within a first temperature range and is a second power that is lower than the first power when the output signal is indicative of a temperature within a second temperature range that is higher than the first temperature range.

2. The radar apparatus of claim 1, in which the first and second temperature ranges are adjacent.

3. The radar apparatus of claim 1, in which there is a third temperature range between the first and second temperature ranges, with the signal generation unit being arranged to as to decrease the output power as the output signal indicates a temperature increasing through the third range.

4. The radar apparatus of claim 1, in which the signal generation unit is arranged so as to cease generating radar signals when the output signal indicates a temperature above a threshold, the threshold being higher than the second range.

5. The radar apparatus of claim 1, comprising a transmitter for the radar signals, coupled to the output of the signal generation unit, the transmitter comprising at least one antenna.

6. The radar apparatus of claim 1, comprising a receiver for received radar signals, which comprises at least one receiving antenna and optionally a reception unit which is arranged to detect and process the received radar signals.

7. A method of operating a radar apparatus, comprising: generating radar signals at an output power using the radar apparatus; measuring the temperature of at least part of the radar apparatus; and varying the output power to a first power when the temperature is within a first temperature range and to a second power lower than the first power when temperature is within a second temperature range higher than the first temperature range.

8. The method of claim 7, in which the first and second temperature ranges are adjacent.

9. The method of claim 7, in which there is a third temperature range between the first and second temperature ranges.

10. The method of claim 9, comprising decreasing the output power as the temperature increases through the third range, typically from the first power to the second power.

11. The method of claim 7, in which the second power is 3 decibels less than the first power, to within one of 0.5, 0.25 or 0.1 decibels.

12. The method of claim 7, in which the highest temperature in the first range may be between 80 and 90 degrees Celsius.

13. The method of claim 12, in which the highest temperature in the first range may be between 84 and 86 degrees Celsius.

14. The method of claim 7, comprising ceasing to generate radar signals should the output signal indicate a temperature above a threshold, the threshold being higher than the second range.

15. The method of claim 7, comprising using a radar apparatus, the radar apparatus comprising: a signal generation unit arranged to generate radar signals at an output power, the signal generating unit having an output for the radar signals, temperature sensing means having an output and arranged to produce at its output an output signal indicative of a temperature of at least part of the radar apparatus, the output of the temperature sensor being coupled to the signal generation unit, in which the signal generation unit is configured so the output power is a first power when the output signal is indicative of a temperature within a first temperature range and is a second power lower than the first power when the output signal is indicative of a temperature within a second temperature range higher than the first temperature range.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 shows a schematic diagram depicting a radar apparatus in accordance with an embodiment of the invention;

[0028] FIG. 2 shows a graph of output power against temperature of the radar apparatus of FIG. 1;

[0029] FIGS. 3a and 3b depict the beam pattern of the radar apparatus of FIG. 1 at different powers in a first mode;

[0030] FIGS. 4a and 4b depict the beam pattern of a radar apparatus of FIG. 1 in a second mode; and

[0031] FIG. 5 depicts an alternative graph of output power against temperature of the radar apparatus of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] A radar apparatus in accordance with a first embodiment of the invention is shown in FIG. 1 of the accompanying drawings. The radar apparatus comprises a signal generation unit 1 of the form of an oscillator, which generates radar signals. The signal generation unit 1 has an output which is coupled to a transmitter circuit 2 which is itself coupled to a transmission antenna 3.

[0033] The transmission antenna 3 is arranged to transmit the radar signals to an area where there may be targets 4. Radar signals reflected off the targets 4 are received by a reception antenna 5 and processed by a reception circuit 6 and passed to a mixer 7, which downmixes the received radar signals with a portion of the generated radar signal for processing by a processor 8.

[0034] A control unit 9 such as a microprocessor controls the operation of the radar apparatus. The radar apparatus is housed within a housing 11. The radar apparatus is also provided with a temperature sensor 10, such as a thermocouple. This is used to determine the temperature of part of the radar apparatus, for example the housing 11 or alternatively the signal generation unit 1. In order to still allow the radar apparatus to function at all above its otherwise usual high temperature limit, the control unit 9 controls the signal generation unit 1 to reduce the power of the signals generated by the signal generation unit 1 at high temperatures, as shown in FIG. 2 of the accompanying drawings, in order to avoid malfunctioning of the radar apparatus due to overheating.

[0035] FIG. 2 shows schematically the power at which the signal generation unit 1 will operate with the temperature as detected by the temperature sensor 10. In a first range, in FIG. 2 from −40° C. to +85° C., the signal generation unit operates at a first power P.sub.H. In a second range, in FIG. 2 from 95° C. to 105° C., the signal generation unit 1 operates at a second power P.sub.L, which is 3 dB lower than P.sub.H—that is half the power of P.sub.H. In a third range between the first and second ranges (so between 85° C. and 95° C.), there is a linear transition from P.sub.H to P.sub.L. Thus, the power applied gradually reduces over the third range. Alternatively, there could be no third range, and there could be an abrupt drop in power between the adjacent first and second ranges, as shown in FIG. 5 of the accompanying drawings.

[0036] Above the second range—so above 105° C., the signal generation unit 1 ceases operating. This value of 105° C. is higher than would have previously been achieved with the same circuit operating at full power.

[0037] The inventors have appreciated that even at reduced transmission power, useful results can be had from the radar apparatus. This can be seen in FIGS. 3a and 3b, and FIGS. 4a and 4b of the accompanying drawings. In FIGS. 3a and 3b, the beam pattern used with a particular transmission antenna 3 used in a higher range mode is shown at full power (P.sub.H) in FIG. 3a and at low power (P.sub.L) in FIG. 3b. We have highlighted particular distances to show where it would still be possible to detect certain elements. Line 20 shows where it would be possible to detect a car, line 21 a cyclist and line 22 a pedestrian. As such, whilst there is some reduction in range, it is still possible to detect these elements at short range, which is arguably the most important part of the detection field to maintain. There is also an increase in the angular field of view.

[0038] In FIGS. 4a and 4b, equivalent diagrams to FIGS. 3a and 3b for a second embodiment of the radar apparatus are shown, with the transmission antenna 3 in a lower range mode. The same lines are depicted for full power (FIG. 4a) and low power (FIG. 4b) respectively. The same conclusions can be drawn.

[0039] The following table shows the maximum ranges for the different detected elements at full and low power:

TABLE-US-00001 Mode Higher range - Lower range - FIGS. 3a/3b FIGS. 4a/4b Power P.sub.H P.sub.L P.sub.H P.sub.L Car 200 m 170 m  110 m  80 m Cyclist 115 m 95 m 60 m 50 m Pedestrian  75 m 65 m 40 m 35 m

[0040] This still gives useable results, even when reducing the power to avoid the effects of overheating.

[0041] The principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.