Radar transmitter circuitry and techniques

• US 20020075178A1
• Filed: 08/16/2001
• Published: 06/20/2002
• Est. Priority Date: 08/16/2000
• Status: Active Grant

• Current Assignee: Valeo Radar Systems, Inc. (Valeo SE)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Pleva, Joseph S., Woodington, Walter Gordon, Russell, Mark E., Delcheccolo, Michael Joseph, Van Rees, H. Barteld, Hanson, James T.
• Granted Patent: US 6,707,419 B2
• Time in Patent Office: Days
• US Class Current: 342/27
• CPC Class Codes: B60K 31/0008 including means for detecting potential obstacles in vehicle path
• CPC Class Codes: B60Q 9/008 for anti-collision purposes
• CPC Class Codes: B60T 2201/08 Lane monitoring; Lane Keeping Systems
• CPC Class Codes: B60T 2201/081 using distance control
• CPC Class Codes: B60T 2201/088 using transmission control
• CPC Class Codes: B60W 2530/10 Weight
• CPC Class Codes: B60W 2554/4043 Lateral speed
• CPC Class Codes: B60W 2554/803 Relative lateral speed
• CPC Class Codes: G01S 13/003 Bistatic radar systems; Multistatic radar systems
• CPC Class Codes: G01S 13/04 Systems determining presence of a target based on relative movement of target G01S13/56
• CPC Class Codes: G01S 13/282 using a frequency modulated carrier wave G01S13/286 takes precedence
• CPC Class Codes: G01S 13/343 using sawtooth modulation
• CPC Class Codes: G01S 13/346 using noise modulation
• CPC Class Codes: G01S 13/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S13/46
• CPC Class Codes: G01S 13/48 using multiple beams at emission or reception
• CPC Class Codes: G01S 13/584 adapted for simultaneous range and velocity measurements
• CPC Class Codes: G01S 13/726 Multiple target tracking
• CPC Class Codes: G01S 13/865 Combination of radar systems with lidar systems
• CPC Class Codes: G01S 13/87 Combinations of radar systems, e.g. primary radar and secondary radar
• CPC Class Codes: G01S 13/878 Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector G01S13/874 takes precedence
• CPC Class Codes: G01S 13/931 : of land vehicles
• CPC Class Codes: G01S 2013/0245 : Radar with phased array antenna
• CPC Class Codes: G01S 2013/9315 : Monitoring blind spots
• CPC Class Codes: G01S 2013/9321 : Velocity regulation, e.g. cruise control
• CPC Class Codes: G01S 2013/93271 : in the front of the vehicles
• CPC Class Codes: G01S 2013/93272 : in the back of the vehicles
• CPC Class Codes: G01S 2013/93274 : on the side of the vehicles
• CPC Class Codes: G01S 2013/93275 : in the bumper area
• CPC Class Codes: G01S 7/023 : Interference mitigation, e.g. reducing or avoiding non-intentional interference with other HF-transmitters, base station transmitters for mobile communication or other radar systems, e.g. using electro-magnetic interference [EMI] reduction techniques auxiliary means for detecting or identifying radar signals or the like G01S7/021; means for anti-jamming G01S7/36
• CPC Class Codes: G01S 7/0232 : Avoidance by frequency multiplex
• CPC Class Codes: G01S 7/032 : Constructional details for solid-state radar subsystems
• CPC Class Codes: G01S 7/038 : Feedthrough nulling circuits
• CPC Class Codes: G01S 7/06 : Cathode-ray tube displays or other two dimensional or three-dimensional displays
• CPC Class Codes: G01S 7/288 : Coherent receivers
• CPC Class Codes: G01S 7/352 : Receivers
• CPC Class Codes: G01S 7/354 : Extracting wanted echo-signals Doppler systems G01S13/50
• CPC Class Codes: G01S 7/356 : involving particularities of FFT processing
• CPC Class Codes: G01S 7/4004 : of parts of a radar system
• CPC Class Codes: G01S 7/4008 : of transmitters
• CPC Class Codes: G01S 7/4021 : of receivers
• CPC Class Codes: H01Q 1/3233 : particular used as part of a sensor or in a security system, e.g. for automotive radar, navigation systems
• CPC Class Codes: H01Q 1/3258 : using the gutter of the vehicle; Means for clamping a whip aerial on the edge of a part of the vehicle
• CPC Class Codes: H01Q 1/3283 : side-mounted antennas, e.g. bumper-mounted, door-mounted mounted on windscreens H01Q1/1271
• CPC Class Codes: H01Q 1/38 : formed by a conductive layer on an insulating support patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface H01Q15/142
• CPC Class Codes: H01Q 1/42 : Housings not intimately mechanically associated with radiating elements, e.g. radome
• CPC Class Codes: H01Q 13/10 : Resonant slot antennas
• CPC Class Codes: H01Q 13/18 : the slot being backed by, or formed in boundary wall of, a resonant cavity longitudinally slotted cylinder H01Q13/12 ; Open cavity antennas
• CPC Class Codes: H01Q 21/0043 : Slotted waveguides combination with horns H01Q13/0233
• CPC Class Codes: H01Q 21/0075 : Stripline fed arrays H01Q21/065 takes precedence
• CPC Class Codes: H01Q 21/0087 : Apparatus or processes specially adapted for manufacturing antenna arrays manufacturing waveguides H01P11/00
• CPC Class Codes: H01Q 21/065 : Patch antenna array
• CPC Class Codes: H01Q 25/00 : Antennas or antenna systems providing at least two radiating patterns arrangements for changing or varying the orientation or the shape of the directional pattern H01Q3/00
• CPC Class Codes: H01Q 3/24 : varying the orientation by switching energy from one active radiating element to another, e.g. for beam switching
• CPC Class Codes: H01Q 3/40 : with phasing matrix

Abstract

A radar transmitter includes a digital ramp generator circuit for generating a VCO control signal. The ramp generator includes a digital signal processor and a digital-to-analog converter. In one embodiment, the VCO output signal is up-converted to provide the transmit signal and in another embodiment, the VCO operates over the transmit frequency. Also described is a VCO comprising a DR and a phase shifter. A temperature compensation feature includes detecting the transmit frequency and comparing the DSP output generating the detected frequency to a DSP output stored in association with the detected frequency. Also described is a technique for compensating for non-linear VCO operation in which the DSP output words are adjusted to provide a waveform complementary in shape to the non-linear VCO characteristic. Susceptibility of the radar to interference is reduced by randomly varying at least one parameter of the ramp signal, such as offset interval or voltage range, in at least one ramp signal cycle.

Claims

1. A radar transmitter comprising:

a DSP having an output terminal at which a digital output word is provided;

a D/A converter having an input terminal coupled to the output terminal of the DSP and an output terminal at which an analog ramp signal is provided; and

a VCO having an input terminal responsive to the analog ramp signal and an output terminal at which a frequency modulated signal is provided.

2. The radar transmitter of claim 1 further comprising a smoothing circuit having an input terminal coupled to the output terminal of the D/A converter and an output terminal coupled to the input terminal of the VCO.

3. The radar transmitter of claim 1 further comprising an up-converter having an input terminal coupled to the output terminal of the VCO and an output terminal at which a transmit signal is provided.

4. The radar transmitter of claim 3 wherein said up-converter comprises a DRO.

5. The radar transmitter of claim 1 wherein said VCO comprises:

an amplifier having an input terminal to which a terminator is coupled and an output terminal;

a phase shifter having an input terminal coupled to the output terminal of the amplifier, an output terminal at which a frequency modulated signal is provided, and a control terminal; and

a DR positioned to couple energy from the output terminal of the phase shifter to the input terminal of the amplifier.

6. The radar transmitter of claim 1 further comprising:

a memory in which is stored a look-up table containing a plurality of DSP output words in association with an expected transmit frequency;

a frequency detection circuit for detecting the frequency of a transmit signal generated by the frequency modulated signal; and

a comparator for comparing a DSP output word from which the detected frequency is generated with a DSP output word stored in the look-up table in association with the detected frequency to provide an error value.

7. The radar transmitter of claim 6 wherein said frequency detection circuit comprises a DR having a fundamental frequency substantially equal to the detected frequency.

8. The radar transmitter of claim 6 further comprising an offset generator for adjusting the output word of the DSP in response to the error value.

9. The radar transmitter of claim 1 further comprising a random number generator for varying at least one parameter of the analog ramp signal.

10. The radar transmitter of claim 9 wherein the at least one parameter is selected from an offset interval and a voltage range.

11. The radar transmitter of claim 1 wherein said transmitter is mounted on a vehicle and comprises a side object detection module of a near object detection system.

13. The method of claim 12 wherein said adjusting step includes offsetting each word of the predetermined sequence of digital words by the error value.

14. The method of claim 12 wherein said detecting step includes detecting the actual frequency of the transmit signal with a DR having a fundamental frequency substantially equal to the actual frequency.

16. The method of claim 15 wherein said ramp signal comprises a plurality of cycles, each comprising an offset portion, a ramp portion, and a CW portion and wherein said at least one parameter is randomly varied in at least one of said plurality of cycles.

17. The method of claim 16 wherein the at least one parameter is selected from the duration of said offset portion and a voltage range of said ramp portion.

12. A method for compensating for temperature induced variations in a radar system comprising the steps of:

generating, from a predetermined sequence of digital words, a transmit signal having a frequency associated with a respective word of the predetermined sequence of digital words;

storing each word of the predetermined sequence of digital words in association with an expected transmit signal frequency;

detecting the actual frequency of the transmit signal;

comparing the digital word from which the actual frequency is generated to a digital word stored in association with the actual frequency to provide an error value; and

adjusting each word of the predetermined sequence of digital words in response to the error value.

15. A method for reducing interference between radar systems comprising the steps of:

generating a ramp signal for controlling to a VCO; and

randomly varying at least one parameter of said ramp signal.

18. A method for compensating for non-linear operation of a VCO in a radar transmitter, comprising the steps of:

measuring the output frequency of the VCO in response to a plurality of input voltage levels to the VCO to provide a characteristic curve of the VCO;

determining a complementary waveform with respect to the characteristic curve; and

providing a sequence of output words of a DSP operable to generate a transmit signal for generating the complementary waveform.