Radar sensor having a two-dimensional beam scan and L-, U- or T-shaped structure for mounting in the region of the front radiator of an automobile

Abstract

Apparatuses and methods for two-dimensional beam scanning for determining the position of an object in three-dimensional space are provided. An apparatus comprises a multiplicity of transmitters and receivers, which are arranged orthogonal to one another in an L-, U- or T-shaped structure. In one apparatus, the transmission signals are frequency and phase modulated in combination; and in another apparatus a single frequency carrier signal is subject to binary phase modulation. Here, this is a high-frequency encoding with a great code length, which is generated according to the pseudo-random number principle. The received signals, which include information from all transmitters, are decoded and consequently split into sub-signals, which can be assigned to a two-dimensional virtual array. According to the method of digital beamforming, the individual signals of the virtual antenna elements are formed into a plurality of highly focused beams in the horizontal and vertical direction.

Claims

1. An apparatus for determining the position of an object in three-dimensional space, the apparatus comprising: an antenna structure, wherein the antenna structure has an L-, U- or T-shaped structure and is mounted in the region of the front radiator of a vehicle.

2. The apparatus of claim 1, wherein the antenna structure comprises a plurality of radar transmit/receive devices, wherein each transmit/receive device has a plurality of receivers and a plurality of transmitters and forms a virtual antenna array for two-dimensional horizontal and vertical beam scanning, wherein the virtual antenna array corresponds to the region of the ventilation openings of a radiator grille of the front radiator.

3. The apparatus of claim 2, wherein the antenna structure is provided positioned behind the air-impermeable region of the radiator grille, so that air flow is not adversely affected.

4. The apparatus of claim 2, wherein a combined frequency-phase modulation of transmitted signals and simultaneous operation of the plurality of transmitters is enabled.

5. The apparatus of claim 4, further comprising an evaluation unit, wherein the evaluation unit decodes an incoming received signal in the plurality of receivers with fixed transmission codes to generate a plurality of sub-signals from the incoming received signal, wherein the plurality of sub-signals corresponds to the plurality of transmitters.

6. The apparatus of claim 5, wherein a high-frequency phase modulation of a continuous-wave transmission signal with simultaneous operation of the plurality of transmitters is provided, and wherein a binary 180 phase encoding is provided, the binary 180 phase encoding generated using a pseudo-random number generator.

7. A method for determining a position of an object, the method comprising: transmitting and receiving signals using an antenna structure in an L- or T-shaped arrangement, wherein the antenna structure is mounted in the region of the front radiator of a vehicle and includes a plurality of transmitters and a plurality of receivers; generating a code sequence for a transmitter of the plurality of transmitters in accordance with a pseudo-random principle using a feedback shift register; generating sub-signals from a received signal using a decoding procedure; allocating individual sub-signals to individual emitters of a virtual array structure generated by the antenna structure; associating the sub-signals using one or more digital beam forming techniques with a plurality of focused antenna beams in horizontal and vertical directions; and displaying the horizontal and vertical position of the object.

8. The method of claim 7, further comprising: generating a binary 0/180 phase encoding of a transmitted signal from frequency ramp to frequency ramp using sawtooth-shaped frequency modulation of the transmitted signal.

9. The method of claim 8, wherein the decoding procedure is performed by decoding with individually generated code sequences of the plurality of transmitters.

10. The method of claim 7, wherein a high-frequency binary phase modulation of a continuous-wave transmission signal is provided.

11. The method of claim 10, wherein the decoding procedure is performed by cross-correlation with time-delayed individually-generated code sequences of transmitting antennas of the antenna structure.

12. The method of claim 7, wherein generating sub-signals from the received signal using a decoding procedure comprises: decoding the received signal using the plurality of receivers with fixed transmission codes to generate the sub-signals from the received signal, wherein the sub-signals correspond to the plurality of transmitters.

Description

EXEMPLARY EMBODIMENTS

[0017] In the following, exemplary embodiments of the invention are explained in more detail based on a drawing. Equivalent parts are provided with the same reference labels in all figures.

Example 1

FMCW Radar with Phase Encoding from Frequency Ramp to Frequency Ramp

[0018] The invention relates to a frequency modulated continuous-wave radar (FMCW Radar) according to FIG. 2, which monitors an area with the aid of digital beam forming. The radar sensor in this case consists of a transmitter with a plurality of, e.g. 12, outputs (Tx) and a plurality of, e.g. 16, receivers (Rx). The transmitter consists of a voltage-controlled oscillator (1) with integrated frequency modulator (2) and 12 parallel outputs (3). The outputs are equipped with power amplifiers (4), which by applying a control signal (11) can change the phase of the transmitted signal by 180.

[0019] FIG. 3 shows the sawtooth-shaped temporal waveform of the transmission frequency. During a frequency ramp the received signal is sampled, for example with 512 points. Approximately 256 ramps are recorded during one measurement cycle. The transmitted signal during the individual frequency ramps is binary-coded in phase by means of a so-called pseudo-random code generator. 0 means the phase is rotated by 180, 1 means the phase remains the same.

[0020] The pseudo-random code is preferably generated by means of a shift register. FIG. 4 shows a 3-stage shift register. Depending on the initial encoding, a different code is set. The code length is calculated to give N=2.sup.n1, where n=number of register stages. In the register shown here with 3 stages, the code is thus repeated after 7 time steps. In practice, however, longer codes are preferred, since in this case the decoupling between the individual transmission signals is better.

[0021] In the receiver of the radar sensor according to FIG. 2, the signal reflected from the object and received by the antenna (5) is initially converted into the baseband with a mixer (6) and sampled by an AD-converter (7). The sampled signal is then decoded with the codes of the respective transmitters (8). Thus, with 16 receivers and 12 transmitters this results in 12*16=192 receive signals. These signals can be assigned to the elements of the virtual array that are shown in FIG. 5.

[0022] After the decoding a signal processing takes place such as that described, for example, in DE 10 2008 061 932 A1. This consists initially of a two-dimensional FFT, which generates a so-called distance-speed-matrix for each reception signal. FIG. 6 shows an example of such a matrix with an echo signal at distance cell 100 and speed cell 0. Due to the finite decoupling between the individual transmission codes, secondary lines are produced in the speed direction, which for the code length N=255 chosen here are approximately 20 dB below the useful signal. The dynamic range in the speed direction is thus restricted. The dynamic range in the distance direction is not affected. This means, for example, that objects at the same distance but with different speeds must differ in their echo amplitude by less than 20 dB in order still to be detected separately.

[0023] After the two-dimensional FFT (9), the antenna lobes (10) are formed. This is carried out by a weighting, phase shift depending on the desired viewing direction and summing of the individual channels, as is described e.g. in DE 10 2008 061 932 A1. Alternatively, a third FFT can be computed over the received signals, which then generates a plurality of antenna lobes in three-dimensional space, a subset of which is then used for the detection in the selected field of view. FIG. 7 shows the antenna lobe of a 1612 antenna array. It has a beam width of 8 horizontally and 11 vertically, and a scanning range of +/60 in the vertical plane and +/65 in the horizontal plane.

Example 2

CW Radar with Phase Encoding Synchronous with the Sampling Frequency

[0024] Another exemplary embodiment is a binary phase encoding of a mono-frequency continuous-wave signal (so-called CW signal). FIG. 8 shows the block circuit diagram of this radar system. An oscillator (1) is operated with a mono-frequency carrier signal. This signal is first allocated over all 12 transmission channels (3) and subjected to a binary phase modulation for each channel by means of a pseudo-random code generator (4). The object echoes detected by the receiving antennas (5) are converted into the baseband with a mixer (6) and digitized with an AD-converter (7). This is followed by a cross-correlation (13) of the digitized signal with the respective time-delayed code of the transmitter (14), so that 12 signal paths are generated per receive channel. To improve the signal-to-noise ratio, multiple code sequences are then accumulated (12) and then fed to a signal processing stageequivalent to example 1consisting of 2D FFT (9) and beam forming (10).

[0025] In contrast to the relatively slow phase encoding according to example 1, here the phase of a mono-frequency signal is changed with each sample value. For the so-called chip length Tc, the following applies: Tc=2*AR/c with

[0026] R: distance resolution

[0027] c: speed of light

[0028] Thus if the aim is to achieve a resolution of 10 cm, then a chip length of 0.67 nsec and a sampling rate of 1.5 giga-samples/sec. is necessary. For a code length of 2.sup.131=8192 the duration of the code Lc=5.46 s. The code duration determines the maximum unique range. This is given by Lc=2*Rmax/c.

[0029] The maximum range in this example is thus 800 meters, which is sufficient for use in the automotive field.