A Low Power Radar for Short-Range Moving Object Measurement

Abstract

Fig 8 The application relates to a radar system for measuring moving objects. The radar system comprises a pulse generation means being switchable between a Doppler radar mode and a pulse radar mode,

Description

TECHNICAL FIELD The invention relates to a radar system for measuring moving objects. The invention also relates to a method for measuring moving objects. BACKGROUND ART There is a growing interest in radar technology enabling short-range and high precision measurements. For most consumer radar applications, there is a need to detect the locations of moving objects. Pulse radar is a type of radar that emits electromagnetic waves from an antenna in short bursts with a given pulse repetition time interval (PRI). The waves are interrupted for a period of time so that the wave can reach a reflecting target and a portion of the energy can return to the same antenna before the next burst of waves is transmitted. A pulse radar transmits a pulse wave (Tx) with a carrier frequency (f0) and measures a reflected pulse to determine the object’s position. As shown in Figure 1, a conventional set up of a pulse radar 100 includes a pulse generator 110, a power amplifier 120, an antenna 130, a low-noise amplifier 140, a local oscillator 160, a mixer 150, and N range gates 170 connected with a digital signal processor 180. The pulse generator 110 transmits pulse waves (Tx) which are emitted from the transceiver 120. A reflected pulse (Rx) is then received by the antenna 130 and sent to the N range gates 170. In practice, the Tx pulse and integration process need to be repeated hundreds of times to average the signal noise out for better single-to-noise ratio (SNR). This is because the energy of a single-pulse signal is very low. However, the integration process of taking multiple pulses would consume a considerable amount of power. For example, a radar detecting a 10-metre object might consume several mA of current. Doppler radar, on the other hand, is another type of radar that transmits a wave (Tx) as a continuous wave. Doppler radar systems correlate the Tx wave to the reflected Rx wave continuously via a mixer. As shown in Figure 2, a conventional Doppler radar circuit 200 includes a Doppler-frequency detector 210, a power amplifier 220, an antenna 230, a low-noise amplifier 240, a mixer 250, a local oscillator 260, and a high-pass filter 270 with a capacitor 280. Assuming that the moving speed of a typical moving object is around 1 m / s, this is equivalent to around only several hundred hertz in frequency. In this case, a short duration of signal waves can be sent out to detect such moving object. The detection may include periodically switching on and off of the transmission of the signal waves. This periodic configuration is therefore equivalent to sampling the moving object under Doppler frequencies. In this way, the Doppler radar can be operated with a very low power consumption, if the duration of the signal waves being switched on can be kept short enough to maintain a reasonable SNR. For example, the accumulation of M pulses in a pulse radar system has a SNR equal to one MxTpU|Se signal pulse in a Doppler radar. Therefore, in order to achieve an optimum short duration of detection, only one MxTpUise Doppler signal pulse is needed with an acceptable SNR. Further details are shown and discussed in Figure 3. For a Doppler radar, the reflected wave from a static object will appear as a DC voltage in a Doppler radar baseband. The reflected waves from a moving object are in the form of low-frequency sine waves which are known as Doppler-frequency waves. A high-pass filter or a DC offset cancellation circuit can block these DC signals. As shown in Figure 2, the high-pass filter 270 is used to block the DC signals and hence the DC voltage is stored in the capacitor 280. The sine waves resulting from a moving object are then detected by the Doppler-frequency detector 210. Doppler radar saves much more power compared to pulse radar. This is because firstly, processing is much easier since the calculation does not calculate range information (e.g. being indicative of a position of the moving object) but just movement information. Secondly, the longer continuous waves have much better SNR compared to short pulses, meaning that the whole circuit can be operated with relatively low power. Thirdly, the doppler radar may only be periodically on for very low duty cycle for moving object detection. During a power off state, the DC information is stored in the capacitor (e.g. capacitor 280 of Figure 2). This helps reduce the amount of power consumption. Therefore, in short-range radar applications, such as in many home appliance applications, the Doppler radar can be used as a wake-up detector of indoor moving objects. However, in long-range radar applications, such as military or airfield applications, using a Doppler radar as a wake-up detector may not be appropriate due to the large amount of possible moving objects. In addition, the longer continuous wave of Doppler radar is not appropriate to distinguish any two objects, since the reflected waves from the two objects may overlap each other. A radar system that combines both the benefits of the Doppler radar and the pulse radar is desired, in particular for short-range detection in industrial, medical, security, consumer applications, etc. Non-limiting example applications include ranging and positioning, presence and gesture detection, and investigation of material properties such as thickness, size, dielectric properties, material composition etc. Therefore, it is desirable to provide a radar system for measuring short-range moving objects that enables both power saving and accurate measurements. SUMMARY OF THE INVENTION The invention is defined by the independent claims to which reference should now be made. Advantageous features are set out in the dependent claims. According to a first aspect of the present invention, there is provided a radar system for measuring moving objects, the radar system comprising: a pulse generation means being switchable between a Doppler radar mode and a pulse radar mode, wherein the pulse generation means is configured to generate a continuous wave in the Doppler radar mode and generate a pulse wave in the pulse radar mode; a frequency detector configured to determine, in the Doppler radar mode, the presence of a moving object by detecting a frequency shift in a returning wave; and a position detection means configured to determine, in the pulse radar mode, a position of the moving object by detecting a position signal reflected by the moving object. Optionally, the pulse generation means is configured to switch from the Doppler radar mode to the pulse radar mode when a frequency shift is detected. Optionally, the pulse generation means is configured to switch from the pulse radar mode to the Doppler radar mode when no position signal is detected by the position detection means. Optionally, the position detection means comprises a range gate detector comprising a plurality of range gates for collecting position signal from the moving object. The position detection means may further comprises a digital signal processor and / or the position detection means may be configured to detect a position signal when at least one of the plurality of range gates collects energy from the moving object. Optionally, the pulse generation means is configured to generate a pulse wave at a pulse width of 1ns in the pulse radar mode and to generate a continuous wave at a pulse width of 100ns. Optionally, the pulse generation means is configured to generate a pulse wave at a pulse repetition interval of 100ns and to generate a continuous wave at a pulse repetition interval of 1ms. The radar system may optionally further comprise a filter circuit configured to offset DC voltage signal as a static-object signal in a returning wave. Optionally, the filter circuit is configured to store the DC voltage signal in a capacitor and / or the filter circuit is configured to pass through an AC voltage signal as a moving-object signal. Optionally, the filter circuit is one of a low-pass filter with a DC offset cancellation circuit. Further, the filter circuit comprises a capacitor configured to store the DC voltage signal and a switch configured to switch off when a DC voltage signal is stored. The radar system optionally further comprises a low noise amplifier configured to amplify the returning wave received at an input of the radar system. The radar system optionally further comprises a power amplifier coupled to the pulse generation means wherein the power amplifier is configured to amplify the generated wave by the pulse generation means. Further, the radar system further optionally comprises a local oscillator and a mixer configured to continuously correlate a transmitted wave with a reflected wave. Optionally, a detection range of the radar system is within 15 metres. The radar system further optionally comprises an antenna configured to detect the returning wave. In a second aspect, a method for measuring moving objects is provided. The method comprises: generating, by a pulse generation means, a continuous wave in a Doppler radar mode; determining, by a frequency detector, the presence of a moving object by detecting frequency shift in a returning wave in the Doppler radar mode; switching to a pulse radar mode in response to the detected moving object; generating, by the pulse generation means, a pulse wave in the pulse radar mode; determining, by a position detection means, a position of the moving object by detecting a position signal reflected by the moving object in the pulse radar mode. Optionally, the method further comprises switching to the Doppler radar mode when no position signal is detected by the position detection means. Optionally, the method further comprises collecting a position signal from at least one of a plurality of range gates of a range gate detector. Further, the method further comprises storing a DC signal in a capacitor as a staticobject signal; and passing an AC signal as a moving-object signal. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be described by way of example and in relation to the accompanying drawings, in which: Figure 1 shows a conventional pulse radar circuit 100; Figure 2 shows a conventional Doppler radar circuit 200; Figure 3 shows a set of signal waves (signal waves 310 to 350) as a comparison of power consumption between pulse waves and continuous waves; Figure 4 shows a schematic circuit diagram of a radar system circuitry 400 according to an aspect of the present invention; Figure 5a shows a schematic circuit diagram of a filter circuit 500a in an active mode; Figure 5b shows a schematic circuit diagram of a filter circuit 500b in an idle mode; Figure 6 shows a set of signal waves 610 in a Doppler radar mode when a moving object is present and a corresponding charging curve of a capacitor of a filter circuit of figures 5a and 5b. Figure 7 shows a schematic illustration of N range gates to determine the position information of a received wave reflected by a moving object. Figure 8 shows a flow chart showing operational steps 810 to 850 of the radar system according to the present invention; Figure 9 shows a set of corresponding illustrations 910 to 930 during the operational steps 810 to 850 shown in figure 8. DETAILED DESCRIPTION This application relates to a radar system for measuring moving objects. Figure 3 shows a comparison between pulse waves and continuous waves used in radar systems according to the present invention. Signal wave 310 is a pulse wave having a pulse width of Tpuise generated by a pulse radar. In order to obtain a reliable signal, such as achieving an acceptable signal-to-noise ratio (SNR), it is necessary to emit the pulse wave multiple times and determine the average value of the received reflected signal. This means that it is necessary to keep the pulse radar on for the period of time of repeating the pulse waves. Shown as signal wave 320 in Figure 3, is a representative signal wave that models the “on-period” of the pulse radar emitting M pulses with a pulse width of TPuise for each pulse. The time duration Ton_Puise represents the time period required for the pulse radar to be switched on. However, this causes a large amount of power to be consumed because the pulse radar is kept on for a long period of time. As shown in Figure 3, a signal wave 330 (same as signal wave 310) is a pulse wave having a pulse width of Tpuise generated by a pulse radar. If the pulse radar integrates the signal over the M pulses with the pulse width of Tpuise, the SNR is equal to that of a signal wave 340, which is equivalent to a continuous wave in a Doppler radar system sampling at a rate of MxTpU|Se. Hence, the transmission of M times of the Tpuise pulse wave is equivalent to the transmission of the MxTpUise continuous wave. Signal wave 350 in Figure 3 is a representative signal wave that models the “on-period” of the Doppler radar emitting a continuous wave with a pulse width of MxTpUise. The time duration Ton_Doppier represents the time period required for the Doppler radar to be switched on to transmit MxTpuise which is the same as M times of Tpuise as shown in signal waves 310 and 330. By comparing signal wave 320 and signal wave 350, it clearly shows that the time duration of Ton_Doppier is much shorter than the time duration Tonjmse, which means the use of continuous wave under Doppler radar mode saves much more power. For example, assuming that a pulse radar emits a pulse wave having a pulse width of 1ns with a PRI of 100ns from an antenna. Since the speed of light is 3* 108 meters per second, the distance covered by the electromagnetic wave emitted by the radar in 1 nanosecond is 30 centimetres. Assuming, the wave is reflected back from an object, this corresponds to a range of 15 centimetres. Therefore, for 100ns between pulses, the radar will be able to detect objects located within a range of 15m from the antenna. In order to achieve a better SNR, the pulse radar is configured to repeatedly emit the pulse waves multiple times and obtain an average. For example, if the pulse radar emits 100 pulses over an averaging period, the active time duration of the pulse radar is 100x100ns=10jus. Therefore, it means that it is necessary to keep the pulse radar active during the entire 10gs of time period to achieve an acceptable SNR of the detected signals. If using a Doppler radar, a continuous 100ns pulse may be transmitted, which is a much longer wave compared to the 1 ns pulse wave transmitted by the pulse radar. However, the active time duration of the Doppler radar is 100ns, which is much shorter than the 10^s active time duration of the pulse radar, and which hence saves much more power. Therefore, a Doppler radar (or a Doppler radar mode) is used to achieve a low-power detection of moving objects according to the present invention. However, a long and continuous wave transmitted under Doppler radar mode is not able to distinguish two objects since the returning waves reflected by the two objects could overlap each other. Therefore, in the present invention, once the Doppler radar (or the Doppler radar mode) successfully detects the presence of a moving object, it wakes up the pulse radar (or the pulse radar mode) to determine an accurate location of such moving object using short pulse waves. This will now be described in more detail. Figure 4 shows a radar system circuitry 400 for measuring moving objects according to the present invention. The radar system circuitry 400 comprises an antenna 490, a pulse generator 410 coupled to the antenna 490 through a power amplifier 480, a frequency detector 420 coupled to a position detection means 430, a mixer 450 coupled to a local oscillator 460 and a low-noise amplifier 470, and a filter circuit 440 coupled to the frequency detector 420. The radar system circuitry 400 may be controlled by a signal processor (not shown). The signal processor may be a digital signal processor (DSP) implemented in a dedicated circuitry, or in an application-specific integrated circuit (ASICs) or field-programmable gate arrays (FPGAs). The radar system circuitry 400 may alternatively be controlled by a microprocessor. The radar system circuitry 400 is configured to be switchable between a Doppler radar mode for detecting movement, and a pulse radar mode for detecting position. When in the Doppler radar mode, the pulse generator 410 is configured to generate a continuous wave. When in the pulse radar mode, the pulse generator 410 is configured to generate a pulse wave. The power amplifier 480 is configured to amplify the continuous wave or pulse wave generated by the pulse generator 410. The radar system circuitry 400 is configured to transmit a continuous wave in the Doppler radar mode through the antenna 490. A returning signal is then received at the antenna 490 and is input back to the radar system for data processing. The low-noise amplifier 470 is coupled to an input of the radar system circuitry 400. The low-noise amplifier 470 is configured to amplify the received returning signal for following processing as described below. The received returning signal is processed first at the low-noise amplifier 470 and fed into the filter circuit 440 before being processed by the frequency detector 420. The filter circuit 440 is configured to filter out any DC voltage signal in the returning signal. This is because moving and static objects both reflect waves and generate return signals. However, the difference is that the reflected waves from static objects are always the same shape. If the reflected waves are integrated multiple times in a certain period of time, it would result in a direct current (DC) return signal. In practice, the radar emits a pulse wave shape and upconverts this to the RF band to emit wave as: Wherein ro is the RF carrier which is frequency-fixed (e.g. 10GHz); and p(t) is the baseband pulse wave (e.g. a rectangular pulse). It can be a 1ns short width or 100ns longer width, for example, depending on the mode (pulsed or doppler). The reflected signal is o ■ p(t - where a represents a reflection coefficient, and td represents the delay time between the transmitted signal and the reflected signal. After down-conversion with a LO signal eja>t, the baseband signal produced is: o-p(t —td) e“)0 wherein = eje. If td is fixed (e.g. signifying a static object), the returning signal is always the same; if td is not fixed (e.g. signifying a moving object), then the phase of the returning signals is rotated, based on the basic Doppler Theory. Hence, the returning signals reflected by static objects are always of the same value, which means a DC signal is received. Since only moving objects are to be detected in this example, the DC signals resulting from static objects are subtracted from the received signals and only the AC signal (called the Doppler-frequency signal) is passed on to the frequency detector 420 for detection of a moving object. Hence, the filter circuit 440 is used to filter out the DC signals and pass through the AC signals for further detection. Figure 4 further shows that the position detection means 430 comprises a plurality of range gates 431 and a digital signal processor 432. The plurality of range gates 431. Each range gate is an electronic circuit that selects signals within a given time period. The gate allows signals to pass through only within the selected time. Figure 5 shows a schematic circuit diagram of an exemplary filter 500 circuit according to the present invention. The filter circuit 500 includes a low pass filter 501 coupled with a DC offset cancellation loop 510. The DC offset cancellation loop 510 includes an amplifier 502 wherein the inverting input of the amplifier 502 is coupled to a first port of the low-pass filter 501 through a first resistor 503 and the output of the amplifier 502 is coupled to a second port of the low-pass filter 501 through a second resistor 504. The filter circuit further comprises a capacitor 505 coupled between the inverting input of the amplifier 502 and the output of amplifier 502. In some embodiments, the amplifier 502 is also called a baseband amplifier. The baseband amplifier 502 may be switchable between an active mode and an idle mode. The active mode corresponds to an on-period of the radar system 400, and the idle mode corresponds to an off-period of the radar system. Figure 5a shows the filter circuit 500a when the filter circuit 501 and amplifier 502 are in the active mode, and Figure 5b shows the filter circuit 500b when the filter circuit 501’ and the amplifier 502’ are in the idle mode. When returning signals are received, the signals reflected by stationary objects are always the same, which means that DC signals are obtained by the radar system. On the other hand, the signals reflected by moving objects give rise to AC signals. Therefore, it is necessary to subtract DC signals resulting from the stationary objects and only allow the Doppler AC signals resulting from the moving objects to pass through the baseband amplifier 502 of the DC offset cancellation 510 as shown in Figure 5a. When, the radar system is turned on, a moving object can be detected within the radar detection range. A corresponding signal wave of the radar system in the Doppler mode is shown as signal wave 610 in Figure 6 and a corresponding charging process of the capacitor 505 is shown as a curve 620 in Figure 6. When the radar system 400 is on and operates in the Doppler radar mode, a long signal wave is transmitted with a duration of 100ns with a PRI of 1ms. As shown in Figure 6, the signal wave 610 is active at time markers 611, 612, 613, 614 and 615, and is turned off during the time intervals between the time makers 611 to 612, 612 to 613, 613 to 614 and 614 to 615. At the same time, the filter circuit 501 is in the active mode at time markers 611, 612, 613, 614 and 615, and in the idle mode during the time intervals between the time makers 611 to 612, 612 to 613, 613 to 614 and 614 to 615. Figure 6 shows an example when an object suddenly appears within the radar detection range between the time markers 611 to 614 and then remains stationary. As described above, the filter circuit 501 is in active mode at time markers 611,612, 613, 614 and 615. This means that the capacitor 505 of the filter circuit experiences a charging process during each active mode as shown by the charging curve 620. When the filter circuit 501’ is in idle mode (shown in Figure 5b) during the time intervals between the time makers 611 to 612, 612 to 613, 613 to 614 and 614 to 615, the charges are stored in the capacitor 505 of the DC offset cancellation circuit 510. Initially, the uncharged capacitor 505 has little resistance and acts like a short circuit allowing current to flow through the resistor 504 of the DC offset cancelation circuit 510. As shown by the charging curve 620, the capacitor 505 is then charged at time markers 611, 612 and 613 when the radar system is on as signal voltage is received as an input of the DC offset cancelation circuit 510. After three cycles of charging (e.g. at time markers 611, 612 and 613), the capacitor 505 of the DC offset cancelation circuit 510 is fully charged. When the capacitor 505 is fully charged, the capacitor 505 acts as an open circuit, blocking any more flow of DC current. As the object remains stationary, the received returning signals are always the same which give rise to DC signals as inputs to the DC offset cancellation circuit 510. Therefore, when the capacitor 505 is fully charged (e.g. from the time marker 614), the DC signal resulting from the stationary object input to the DC offset cancellation circuit 510 is then blocked. The frequency detector 420 is then used to determine the presence of a moving object based on a returning wave in the Doppler radar mode. The frequency detector 420 determines the presence of a moving object based on a detection of a frequency shift of the returning wave when compared with the transmitted wave. In some embodiments, the frequency detector 420 may be a simple amplitude detector, a phase detector or a Doppler-frequency detector. As will be described later, if the frequency detector detects a frequency shift, it is configured to send a signal to the position detector means 430. The position detection means 430 is configured to determine position information of the moving object which is detected by the radar system 400 under the Doppler radar mode. The position detection means 430 determines the position of the moving object based on a detection of a position signal reflected by the moving object under the pulse radar mode. In some embodiments, the position detection means 430 includes a plurality of range gates 730 (shown in Figure 7). In contrast to known radars which utilise either a single pulse radar or a single Doppler radar, the present invention provides a radar system that is switchable between a pulse radar mode and a Doppler radar mode. In addition, as can be seen in Figure 4, both modes share the same components, including power amplifier 480, low-noise amplifier 470, mixer 450 and local oscillator 460. There is therefore no need to duplicate these circuit components for both modes, therefore reducing the complexity of the circuit. As shown in Figure 4, the position detection means 430 comprises a plurality of range gates 431 and a digital signal processor 432. Figure 7 shows that a plurality of range gates (e.g. N range gates) are divided into N time positions, for time To to Tn. Each of the N range gates is open and closed sequentially for a specific time window. For example, a first range gate is open during the time window of To to Ti, a second range gate is open during the time window of Ti T2, a third range gate is open during the time window of T2toT3, ... and a Nth range gate is open at the time window of Tn-i to Tn. An integration of any received signals over each time window is obtained to determine if any signals are received. The radar system circuitry 400 is then configured to determine the corresponding time windows of the returning signals. Once the time windows are determined, the distance from which the received signal is returned is therefore calculated which therefore determines the location of the objects. When in operation, the radar system 400 as described above switches between a Doppler radar mode and a pulse radar mode for an accurate and low-power measurement of short-range moving objects. Figure 8 shows a flow chart of operational steps 810 to 850 of the radar system under operation. At the start, the radar system is turned on at a step 810. The radar system 700 is initially set to a Doppler radar mode at a step 820. In the Doppler radar mode, continuous waves are transmitted to detect the presence of moving objects. In step 830, a determination is made as to whether a moving object is detected or not (see discussion above). The result of the determination is indicated by Flago. If a frequency shift is detected which indicates the presence of a moving object, the digital signal processor of the radar system determines a Flago value of 1 (e.g. Flago = 1); if no frequency shift is detected which indicates no presence of any moving object, the digital signal processor of the radar system determines a Flago value of 0 (e.g. Flago = 0). If no moving object is detected, e.g. Flago = 0, then control flows back to step 820, and steps 820 and 830 are repeated in the Doppler mode. When a moving object is detected, e.g. Flago = 1, then pulse mode is then triggered at step 840. The radar system 400 then switches to pulse mode operation, in which pulse waves are transmitted to determine the position of the moving object. As described above, the radar system comprises a position detection means, such as a plurality of range gates, to determine the location of the moving object. This is done by a set of integrations over the respective range gates in step 850. When an integration value is non-zero which means a received signal is present in the corresponding range gate, the position of the moving object is determined. In this case, the digital signal processor determines a Flagp value of 1 (e.g. Flagp= 1). The radar system continues with the pulse mode 840 and the digital signal processor of the radar system determines the integrations over the remaining range gates to further determine the location of the moving object until all integrations over the range gates have been done. When the integration over the range gates has been completed and the range of the detected object determined, the digital signal processor of the radar system sets a checked Flagp of a value 0 (e.g. Flagp = 0). The radar system then switches back to the Doppler mode and repeat the process from the step 820 to detect further moving objects. The detected position of the object may be output to a screen or other apparatus for further processing. Figure 9 shows a set of corresponding schematic illustrations 910, 920 and 930 of the operational steps 810 to 850 shown in figure 8. As shown by modes illustration 910, the radar system begins with the Doppler mode and the corresponding Flago 920 and Flagp 930 are both at value 0 because no signal is detected yet. At a time 901, a moving object appears and is detected by the radar system which results in a value 1 at Flago 920. The radar system then switches to the pulse radar mode at the time 901. When the position of the moving object is determined by the radar system in the pulse mode at a time 902, the Flagp has a value 1 at time 902. The radar system then continues with the pulse mode until there is no further position information determined by the radar system. As illustrated at a time 903, when there is no further position information determined, the checked Flagp has a value 0 at time 903. This therefore switches back to the Doppler radar mode at the time 903 for further detection of any moving object. If no moving object is detected, the radar system is maintained in the Doppler radar mode, such as at a time 904 where Flago = 0. The operational process therefore does not repeat again until a moving object is detected (when Flago = 1).

Claims

1. A radar system for measuring moving objects, the radar system comprising: a pulse generation means being switchable between a Doppler radar mode and a pulse radar mode, wherein the pulse generation means is configured to generate a continuous wave in the Doppler radar mode and generate a pulse wave in the pulse radar mode;a frequency detector configured to determine, in the Doppler radar mode, the presence of a moving object by detecting a frequency shift in a returning wave; and a position detection means configured to determine, in the pulse radar mode, a position of the moving object by detecting a position signal reflected by the moving object.

2. The radar system according to claim 1, wherein the pulse generation means is configured to switch from the Doppler radar mode to the pulse radar mode when a frequency shift is detected.

3. The radar system according to claim 1 or 2, wherein the pulse generation means is configured to switch from the pulse radar mode to the Doppler radar mode when no position signal is detected by the position detection means.

4. The radar system according to any preceding claim, wherein the position detection means comprises a range gate detector comprising a plurality of range gates for collecting position signal from the moving object.

5. The radar system according to claim 4 wherein the position detection means further comprises a digital signal processor.

6. The radar system according to any of claims 4 or 5, wherein the position detection means is configured to detect a position signal when at least one of the plurality of range gates collects energy from the moving object.

7. The radar system according to any preceding claim, wherein the pulse generation means is configured to generate a pulse wave at a pulse width of 1ns in the pulse radar mode and to generate a continuous wave at a pulse width of 100ns.

8. The radar system according to any preceding claim, wherein the pulse generation means is configured to generate a pulse wave at a pulse repetition interval of 100ns and to generate a continuous wave at a pulse repetition interval of 1ms.

9. The radar system according to any preceding claim, further comprising a filter circuit configured to offset DC voltage signal as a static-object signal in a returning wave.

10. The radar system according to claim 9, wherein the filter circuit is configured to store the DC voltage signal in a capacitor.

11. The radar system according to claim 9 or 10, wherein the filter circuit is configured to pass through an AC voltage signal as a moving-object signal.

12. The radar system according to any of claims 9 to 11, wherein the filter circuit is one of a low-pass filter with a DC offset cancellation circuit.

13. The radar system according to any of claims 9 to 12, wherein the filter circuit comprises a capacitor configured to store the DC voltage signal and a switch configured to switch off when a DC voltage signal is stored.

14. The radar system according to any preceding claim, further comprising a low noise amplifier configured to amplify the returning wave received at an input of the radar system.

15. The radar system according to any preceding claim further comprising a power amplifier coupled to the pulse generation means wherein the power amplifier is configured to amplify the generated wave by the pulse generation means.

16. The radar system according to any preceding claim further comprising a local oscillator and a mixer configured to continuously correlate a transmitted wave with a reflected wave.

17. The radar system according to any preceding claim wherein a detection range of the radar system is within 15 metres.

18. The radar system according to any preceding claim further comprising an antenna configured to detect the returning wave.

19. A method for measuring moving objects, the method comprising:generating, by a pulse generation means, a continuous wave in a Doppler radar mode;determining, by a frequency detector, the presence of a moving object by detecting frequency shift in a returning wave in the Doppler radar mode;switching to a pulse radar mode in response to the detected moving object;generating, by the pulse generation means, a pulse wave in the pulse radar mode;determining, by a position detection means, a position of the moving object by detecting a position signal reflected by the moving object in the pulse radar mode.

20. The method according to claim 19 further comprising:switching to the Doppler radar mode when no position signal is detected by the position detection means.

21. The method according to claim 19 or 20 further comprising: collecting a position signal from at least one of a plurality of range gates of a range gate detector.

22. The method according to any of claims 19 to 21 further comprising: storing a DC signal in a capacitor as a static-object signal; and passing an AC signal as a moving-object signal.AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWS30 01 2515CLAIMS1. A radar system for measuring moving objects, the radar system comprising: a pulse generation means being switchable between a Doppler radar mode5 and a pulse radar mode, wherein the pulse generation means is configured togenerate a continuous wave in the Doppler radar mode and generate a pulse wave in the pulse radar mode;a frequency detector configured to determine, in the Doppler radar mode, the presence of a moving object by detecting a frequency shift in a returning wave; and 10 a position detection means configured to determine, in the pulse radar mode,a position of the moving object by detecting a position signal reflected by the moving object, wherein the pulse generation means is further configured to switch from the pulse radar mode to the Doppler radar mode when no position signal is detected by the position detection means.

152. The radar system according to claim 1, wherein the pulse generation means is configured to switch from the Doppler radar mode to the pulse radar mode when a frequency shift is detected.20 3. The radar system according to any preceding claim, wherein the position detectionmeans comprises a range gate detector comprising a plurality of range gates for collecting position signal from the moving object.

4. The radar system according to claim 3 wherein the position detection means further 25 comprises a digital signal processor.

5. The radar system according to any of claims 3 or 4, wherein the position detection means is configured to detect a position signal when at least one of the plurality of range gates collects energy from the moving object.

306. The radar system according to any preceding claim, wherein the pulse generation means is configured to generate a pulse wave at a pulse width of 1ns in the pulse radar mode and to generate a continuous wave at a pulse width of 100ns.30 01 257. The radar system according to any preceding claim, wherein the pulse generation means is configured to generate a pulse wave at a pulse repetition interval of 100ns and to generate a continuous wave at a pulse repetition interval of 1ms.5 8. The radar system according to any preceding claim, further comprising a filter circuitconfigured to offset DC voltage signal as a static-object signal in a returning wave.

9. The radar system according to claim 8, wherein the filter circuit is configured to store the DC voltage signal in a capacitor.1010. The radar system according to claim 8 or 9, wherein the filter circuit is configured to pass through an AC voltage signal as a moving-object signal.

11. The radar system according to any of claims 8 to10, wherein the filter circuit is one of 15 a low-pass filter with a DC offset cancellation circuit.

12. The radar system according to any of claims 8 to 11, wherein the filter circuit comprises a capacitor configured to store the DC voltage signal and a switch configured to switch off when a DC voltage signal is stored.2013. The radar system according to any preceding claim, further comprising a low noise amplifier configured to amplify the returning wave received at an input of the radar system.25 14. The radar system according to any preceding claim further comprising a poweramplifier coupled to the pulse generation means wherein the power amplifier is configured to amplify the generated wave by the pulse generation means.

15. The radar system according to any preceding claim further comprising a local 30 oscillator and a mixer configured to continuously correlate a transmitted wave with areflected wave.

16. The radar system according to any preceding claim wherein a detection range of the radar system is within 15 metres.3517. The radar system according to any preceding claim further comprising an antenna configured to detect the returning wave.

18. A method for measuring moving objects, the method comprising:generating, by a pulse generation means, a continuous wave in a Doppler radar mode;determining, by a frequency detector, the presence of a moving object by5 detecting frequency shift in a returning wave in the Doppler radar mode;switching to a pulse radar mode in response to the detected moving object;generating, by the pulse generation means, a pulse wave in the pulse radar mode;determining, by a position detection means, a position of the moving object by10 detecting a position signal reflected by the moving object in the pulse radar mode;andswitching, by the pulse generation means, from the pulse radar mode to the Doppler radar mode when no position signal is detected by the position detection means.1519. The method according to claim 18 further comprising:collecting a position signal from at least one of a plurality of range gates of a range gate detector.30 01 2520 20. The method according to claim 18 or 19 further comprising:storing a DC signal in a capacitor as a static-object signal; and passing an AC signal as a moving-object signal.25

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