Patent Description:
A radar transceiver with improved signal-to-noise ratio in the presence of a strong reflector is described herein. In one example, a device includes a phase shifter, an I/Q signal generator, a first mixer, a second mixer, and a feedback path. The phase shifter includes a signal input, a control input, and an output. The I/Q signal generator includes an input, a first output, and a second output. The input is coupled to the output of the phase shifter. The first mixer includes an input coupled to the first output of the I/Q signal generator. The second mixer includes an input coupled to the second output of the I/Q signal generator. The feedback path is coupled between an output of the second mixer and the control input of the phase shifter.

In another example, a radar transceiver includes a receiver. The receiver includes a low noise amplifier a mixer, a baseband filter, an integrator, and a phase shifter. The mixer includes an input coupled to an output of the low noise amplifier. The baseband filter includes an input coupled to an output of the mixer. The integrator includes an input coupled to an output of the baseband filter. The phase shifter includes a control input and an output. The control input is coupled to an output of the integrator. The output of the phase shifter is coupled to the mixer.

In a further example, a radar transceiver includes a receiver. The receiver includes a low noise amplifier a mixer, a baseband filter, an integrator, and a phase shifter. The mixer includes an input coupled to an output of the low noise amplifier. The baseband filter includes an input coupled to an output of the mixer. The integrator includes an input coupled to an output of the baseband filter. The phase shifter includes a control input. The control input is coupled to an output of the integrator.

The term "couple" or "couples" means either an indirect or direct wired or wireless connection. Thus, if a first device couples to a second device, that connection may be through a direct connection or through an indirect connection via other devices and connections. Also, the recitation "based on" means "based at least in part on. " Therefore, if X is based on Y, then X may be a function of Y and any number of other factors.

In a frequency modulated continuous wave (FMCW) radar system, the transmitter and receiver are simultaneously operated. The signal transmitted by an FMCW radar system is a linear frequency modulated continuous wave sequence of chirps, where a chirp is linear frequency sweep (a ramp or sawtooth shaped frequency sweep). The chirp sequence is amplified by a power amplifier and transmitted from a transmit antenna. A receive antenna receives reflections of the transmitted signal. The received signal is amplified and mixed with the chirp sequence being transmitted to generate a beat frequency that is digitized and processed.

When a strong reflector is disposed near the antennas of the radar system, the signal returned by the reflector can substantially degrade radar performance. For example, in a vehicular radar system, if the transmit and receive antennas are disposed behind a bumper of the vehicle, then the uncorrelated phase noise (UPN) of the receiver, the transmitter, and the frequency synthesizer severely degrades the receiver noise floor and limits the signal-to-noise ratio (SNR) of object detection, which, in turn reduces the range of the radar system. Twelve decibels (dB) of noise floor degradation due to UPN reduces the range of the radar system by one-half.

For an interfering bumper (e.g., a bumper behind which the antennas are mounted) at range Rbump from the antennas, the frequency shift in the received signal is: <MAT> with respect to the local oscillator signal, where:.

Some radar receivers attempt to compensate for the frequency and phase shift induced by a strong reflector by adding a fixed delay to the local oscillator used in the receiver. The fixed delay cancels the delay in received signal caused by the strong reflector (e.g., the bumper), and reduces the effect of radio frequency (RF) synthesizer UPN, but does not compensate for changes in the delay caused by movement (e.g., vibration) of the strong reflector or reduce UPN from the transmitter, receiver, or local oscillator buffers. Other radar receiver implementations apply digital post-processing to shift the receiver spectrum. Digital post-processing introduces a number of issues, for example: (<NUM>) the phase detected at the analog-to-digital converter (ADC) output after nullifying Δfbump may not be related to the RF phase shift to attain amplitude noise (AN) condition, (<NUM>) phase shift inaccuracy is induced by sampling clock uncertainty in the digitization, (<NUM>) phase shift errors are caused by phase shifting in the receiver's filters, and/or (<NUM>) digital processing is unable to track reflector vibrations due to processing time constraints.

The radar transceivers described herein include an analog control loop that cancels the frequency shift and phase shift caused by the strong reflector. The analog control loop may operate in the quadrature (Q) channel of the receiver, which puts the in-phase (I) channel of the receiver in AN condition, and increases the SNR of the receiver in the presence of a strong reflector. The noise floor of the radar transceivers may be improved by up to <NUM> dB or more relative to other receiver implementations. Also, the analog control loop can track and cancel frequency and phase shift variation caused by vibration of the strong reflector.

<FIG> shows a block diagram for a radar system <NUM> that includes an example radar transceiver having a phase/frequency feedback loop in this description. The radar system <NUM> includes a radar transceiver <NUM>, an antenna <NUM>, an antenna <NUM>, and an RF synthesizer <NUM> (radio frequency synthesizer <NUM>). The antenna <NUM> is coupled to the radar transceiver <NUM> for reception of reflected radar signals (reflections of radar signals transmitted by the antenna <NUM>). The antenna <NUM> is coupled to the radar transceiver <NUM> for transmission of radar signals. The RF synthesizer <NUM> is coupled to the radar transceiver <NUM>, and generates the local oscillator signal <NUM> that is transmitted by the radar transceiver <NUM> and used by the radar transceiver <NUM> to down-convert received radar reflections.

The radar transceiver <NUM> includes a receiver <NUM> and a transmitter <NUM>. The transmitter <NUM> includes a power amplifier <NUM> that is coupled to the RF synthesizer <NUM> and the antenna <NUM>. The receiver <NUM> includes a low-noise amplifier (LNA) <NUM> coupled to an in-phase (I) channel and a quadrature-phase (Q) channel, an I/Q signal generator <NUM>, and a phase shifter <NUM>. The I/Q signal generator <NUM> receives the local oscillator signal <NUM> and generates in-phase and quadrature phase versions of the local oscillator signal <NUM>. The I channel includes an LNA <NUM>, a mixer <NUM> (in-phase channel mixer), a baseband filter <NUM>, and an integrator <NUM>. The Q channel includes an LNA <NUM>, a mixer <NUM> (quadrature channel mixer), a baseband filter <NUM>, and an integrator <NUM>. The mixer <NUM> includes an input 116A coupled to the LNA <NUM>, and an input 116B coupled to an output 118B of the I/Q signal generator <NUM> via the buffer <NUM>, and an output 116C coupled to an input 130A of the baseband filter <NUM>. The mixer <NUM> multiplies the reflected radar signals provided via the LNA <NUM> and the LNA <NUM> and the in-phase version of the local oscillator signal <NUM> to downconvert the reflected radar signals and generate an intermediate frequency signal. The baseband filter <NUM> includes an output 130B coupled to an input 132A of the integrator <NUM>, and an output 130C coupled to an ADC <NUM>. The ADC <NUM> may be a delta-sigma ADC. The baseband filter <NUM> filters the output of the mixer <NUM> for digitization by the ADC <NUM>. The integrator <NUM> is coupled to the baseband filter <NUM>, and is provided in the I channel to match the impedance and loading presented to the baseband filter <NUM> to the impedance and loading presented to the baseband filter <NUM> of the Q channel.

In the Q channel, the mixer <NUM> includes an input 128A coupled to the LNA <NUM>, an input 128B coupled to an output 118C of the I/Q signal generator <NUM> via the buffer <NUM>, and an output 128C coupled to an input 134A of the baseband filter <NUM>. The mixer <NUM> multiplies the reflected radar signals provided via the LNA <NUM> and the LNA <NUM> and the quadrature-phase version of the local oscillator signal <NUM> to downconvert the reflected radar signals and generate an intermediate frequency signal. The baseband filter <NUM> includes an output 134B coupled to an input 136A of the integrator <NUM>, and an output 134C coupled to an analog-to-digital converter (ADC) <NUM>. The ADC <NUM> may be a delta-sigma ADC. The baseband filter <NUM> filters the output of the mixer <NUM> for digitization by the ADC <NUM>. The signal reflected by the strong reflector <NUM> is provided at the output 134B of the <NUM> an integrated by the integrator <NUM> to produce a control signal <NUM> for the phase shifter <NUM>.

A linear time varying phase shift provides a constant frequency offset proportional to the slope of the linear phase shift with time. For a strong reflector <NUM> at range Rbump from the antennas <NUM> and <NUM>, the frequency shift Δfbump to be added to the ramp is <MAT>, where is the time delay from transmission to reflection by the strong reflector <NUM>, and is the slope of the FMCW chirp. With the phase shifter <NUM> having a <NUM> to <NUM>° phase shifter with a <NUM> volt range for the control signal <NUM>, the maximum frequency shift generated is <MAT>. As long as Δfphs_max > Δfbump the control signal <NUM> can correct for the frequency difference of Δfbump between the received radar signals and the local oscillator signal <NUM>.

The phase shifter <NUM> includes a signal input 124A that is coupled to an output of the RF synthesizer <NUM>, a control input 124B that is coupled to an output 136B of the integrator <NUM>, and an output 124C that is coupled to the input 118A of the I/Q signal generator <NUM>. The integrator <NUM> compares the output of the baseband filter <NUM> to zero and integrates the difference to generate the control signal <NUM> for the phase shifter <NUM>. The phase shifter <NUM> receives the local oscillator signal <NUM> generated by the RF synthesizer <NUM> and shifts the phase of the local oscillator signal <NUM> based on control signal <NUM>. The baseband filter <NUM> and the integrator <NUM> are part of a feedback path that is coupled between the output 128C of the mixer <NUM> and the control input 124B of the phase shifter <NUM>. A feedback loop is formed by coupling the output 128C of the mixer <NUM> to the input 134A of the baseband filter <NUM>, coupling the output 134B of the baseband filter <NUM> to the input 136A of the integrator <NUM>, coupling the output 136B of the integrator <NUM> to the control input 124B of the phase shifter <NUM> to control the phase shifter <NUM>. The output 124C of the phase shifter <NUM> is coupled to the input 118A of the I/Q signal generator <NUM>, and the output 118C of the I/Q signal generator <NUM> is coupled to the input 128B of the mixer <NUM> to close the feedback loop. The control signal <NUM> shifts the frequency of the local oscillator signal <NUM> to match the frequency shift of the frequency ramp transmitted via the power amplifier <NUM> as reflected by the strong reflector <NUM> (e.g., a bumper behind which the antenna <NUM> and the antenna <NUM> are mounted), and forces the phase shift of the shifted local oscillator and the reflected radar signal provided to the mixer <NUM> to <NUM>°. The frequency and phase adjustments minimize DC voltage in the Q channel, and maximize DC voltage in the I channel, thereby putting the I channel in AN condition and reducing or eliminating the effects of phase noise of the RF synthesizer <NUM> and UPN on SNR of the receiver <NUM> in the I channel. The control signal <NUM> tracks vibration of the strong reflector <NUM> to maintain an AN condition in the I channel.

In some implementations of the radar system <NUM>, the receiver <NUM> is provided on an integrated circuit <NUM>. The integrated circuit may be enclosed in a package <NUM>.

<FIG> shows an example of the frequency ramp <NUM> generated by the RF synthesizer <NUM> and transmitted via the power amplifier <NUM>, the signal <NUM> reflected by the strong reflector <NUM> and received by the receiver <NUM>, and the control signal <NUM> generated by the integrator <NUM> for controlling the phase shifter <NUM> over the interval of the signal <NUM>. <FIG> shows the control signal <NUM>, which includes a step <NUM> and ramp <NUM> that corrects for a frequency difference of Δfbump between the reflected signal and the local oscillator signal <NUM> and ensures that the phase shift between the reflected signal and the local oscillator signal <NUM> is <NUM>°. <FIG> shows the frequency ramp <NUM> and the signal <NUM> aligned (Δfbump=<NUM>) after application of the control signal <NUM> to the local oscillator signal <NUM> in the phase shifter <NUM>.

<FIG> shows a block diagram for a radar system <NUM> including a second example radar transceiver having a phase/frequency feedback loop in this description. The radar system <NUM> includes a radar transceiver <NUM>, an antenna <NUM>, an antenna <NUM>, and an RF synthesizer <NUM>. The antenna <NUM> is coupled to the radar transceiver <NUM> for reception of reflected radar signals. The antenna <NUM> is coupled to the radar transceiver <NUM> for transmission of radar signals. The RF synthesizer <NUM> is coupled to the radar transceiver <NUM>, and generates the local oscillator signal <NUM> that is transmitted by the radar transceiver <NUM> and used by the radar transceiver <NUM> to down-convert received radar reflections.

The radar transceiver <NUM> includes a receiver <NUM> and a transmitter <NUM>. The transmitter <NUM> includes a power amplifier <NUM>, a phase shifter <NUM>, and a transmitter modulation control circuit <NUM>. The phase shifter <NUM> is coupled to the RF synthesizer <NUM>, the power amplifier <NUM>, and the transmitter modulation control circuit <NUM>. The transmitter modulation control circuit <NUM> generates an output signal <NUM> that the phase shifter <NUM> applies to modulate the phase of the local oscillator signal <NUM> before amplification by the power amplifier <NUM>.

The receiver <NUM> includes an LNA <NUM> coupled to an I channel and a Q channel, an I/Q signal generator <NUM>, a phase shifter <NUM>, and a summation circuit <NUM>. The I/Q signal generator <NUM> receives the local oscillator signal <NUM>, via the phase shifter <NUM>, and generates in-phase and quadrature phase versions of the local oscillator signal <NUM>. The I channel includes an LNA <NUM>, a mixer <NUM>, a baseband filter <NUM>, and an integrator <NUM>. The Q channel includes an LNA <NUM>, a mixer <NUM>, a baseband filter <NUM>, and an integrator <NUM>. The mixer <NUM> includes an input 316A coupled to the LNA <NUM>, an input 316B coupled to an output 318B of the I/Q signal generator <NUM> via the buffer <NUM>, and an output 316C coupled to an input 330A of the baseband filter <NUM>. The baseband filter <NUM> includes an output 330B coupled to an input 332A of the integrator <NUM>, and an output 330C coupled to an analog-to-digital converter (ADC) <NUM>. The ADC <NUM> may be a delta-sigma ADC. The integrator <NUM> is coupled to the baseband filter <NUM> to match the impedance and loading presented to the baseband filter <NUM> to the impedance and loading presented to the baseband filter <NUM> of the Q channel.

In the Q channel, the mixer <NUM> includes an input 328A coupled to the LNA <NUM>, an input 328B coupled to an output 318C of the I/Q signal generator <NUM> via the buffer <NUM>, and an output 328C coupled to an input 334A of the baseband filter <NUM>. The baseband filter <NUM> includes an output 334B coupled to an input 336A of the integrator <NUM>, and an output 334C coupled to an analog-to-digital converter (ADC) <NUM>. The ADC <NUM> may be a delta-sigma ADC.

The summation circuit <NUM> is coupled to the integrator <NUM> and the phase shifter <NUM>. The summation circuit <NUM> includes an input 354A that is coupled to the output 336B of the integrator <NUM>, an input 354B that is coupled to an output 352B of the transmitter modulation control circuit <NUM>, and an output 354C that is coupled to a control input 324B of the phase shifter <NUM>. The summation circuit <NUM> adds a modulation control signal generated by the transmitter modulation control circuit <NUM> for use in modulating the local oscillator signal <NUM> for transmission to the output signal of the integrator <NUM> to account for transmitter modulation in the control signal <NUM> so that the transmission modulation does not affect the AN condition in the I channel.

The phase shifter <NUM> includes a signal input 324A that is coupled to an output of the RF synthesizer <NUM>, and an output 324C that is coupled to an input 318A of the I/Q signal generator <NUM>. The integrator <NUM> compares the output of the baseband filter <NUM> to zero and integrates to generate the output signal <NUM>. The summation circuit <NUM> adds the output signal <NUM> and the output signal <NUM> generated by the transmitter modulation control circuit <NUM> to produce the control signal <NUM> provided to the phase shifter <NUM>. The phase shifter <NUM> receives the local oscillator signal <NUM> generated by the RF synthesizer <NUM> and shifts the phase of the local oscillator signal <NUM> based on control signal <NUM>. The baseband filter <NUM> and the integrator <NUM> are part of a feedback path that is coupled between the output 328C of the mixer <NUM> and the control input 324B of the phase shifter <NUM>. The control signal <NUM> shifts the frequency of the local oscillator signal <NUM> to match the frequency shift of the frequency ramp transmitted via the power amplifier <NUM> as reflected by reflector <NUM>, and forces the phase shift of the shifted local oscillator and the reflected radar signal provided to the mixer <NUM> to <NUM>°. The frequency and phase adjustments minimize DC in the Q channel, and maximize DC in the I channel, thereby putting the I channel in AN condition and reducing or eliminating the effects of phase noise of the RF synthesizer <NUM> and UPN on SNR of the receiver <NUM> in the I channel. The control signal <NUM> tracks vibration of the reflector <NUM> to maintain an AN condition in the I channel.

In the receiver <NUM> and the receiver <NUM>, a feedback path included in the Q channel automatically put the I channel in AN condition to lower the receiver noise floor. <FIG> shows a block diagram for an example receiver <NUM> that includes a phase/frequency feedback loop in a single receiver channel. Implementations of the receiver <NUM> lack Q channel circuitry. The receiver <NUM> includes an LNA <NUM>, a mixer <NUM>, baseband filter <NUM>, and integrator <NUM>, a phase shifter <NUM>, a buffer <NUM>, an ADC <NUM>, and a digital phase shift circuit <NUM> (quadrature phase shift circuit).

The LNA <NUM> is coupled to an antenna (not shown) for reception of reflected radar signals. The mixer <NUM> includes an input 416A coupled to the LNA <NUM>, and an input 416B coupled to an output 424C of the phase shifter <NUM> via the buffer <NUM>, and an output 416C coupled to an input 430A of the baseband filter <NUM>. The baseband filter <NUM> includes an output 430B coupled to an input 432A of the integrator <NUM>, and an output 430C coupled to the ADC <NUM>. The ADC <NUM> may be a delta-sigma ADC.

The phase shifter <NUM> includes a signal input 424A that is coupled to an output of an RF synthesizer (not shown), a control input 424B that is coupled to an output 432B of the integrator <NUM>, and an output 424C that is coupled to the mixer <NUM> via the buffer <NUM>. The integrator <NUM> compares the output of the baseband filter <NUM> to zero and integrates to generate a control signal <NUM> for the phase shifter <NUM>. The phase shifter <NUM> receives the local oscillator signal <NUM> and shifts the phase of the local oscillator signal <NUM> based on control signal <NUM>. The baseband filter <NUM> and the integrator <NUM> are part of a feedback path that is coupled between the output 416C of the mixer <NUM> and the control input 424B of the phase shifter <NUM>. The control signal <NUM> shifts the frequency of the local oscillator signal <NUM> to match the frequency shift of a transmitted frequency ramp reflected by a strong reflector, and forces the phase shift of the shifted local oscillator and the reflected radar signal provided to the mixer <NUM> to <NUM>°.

The digital phase shift circuit <NUM> is coupled to the ADC <NUM>. To put the receiver <NUM> in AN condition, the digital phase shift circuit <NUM> shifts the phase of the digitized data produced by the ADC <NUM> by <NUM>°, thereby eliminating the effects of phase noise of the RF synthesizer and UPN on SNR of the receiver <NUM>.

In the receiver <NUM>, the receiver <NUM>, and the receiver <NUM> the phase and frequency of the local oscillator is shifted to suppress phase noise in the receiver. <FIG> shows a block diagram for an example receiver <NUM> that includes a phase shifter in the LNA path rather than the local oscillator path. The receiver <NUM> includes an LNA <NUM>, a phase shifter <NUM>, and an I/Q signal generator <NUM>. The I/Q signal generator <NUM> receives a local oscillator signal <NUM> and generates in-phase and quadrature phase versions of the local oscillator signal <NUM>. The LNA <NUM> is coupled to a phase shifter <NUM>. The LNA <NUM> receives reflected radar signals. The phase shifter <NUM> is coupled to an I channel and a Q channel. The I channel includes an LNA <NUM>, a mixer <NUM>, a baseband filter <NUM>, and an integrator <NUM>. The Q channel includes an LNA <NUM>, a mixer <NUM>, a baseband filter <NUM>, and an integrator <NUM>. The mixer <NUM> includes an input 516A coupled to the output 524C of the phase shifter <NUM> via the LNA <NUM>, an input 516B coupled to an output 518B of the I/Q signal generator <NUM> via the buffer <NUM>, and an output 516C coupled to an input 530A of the baseband filter <NUM>. The baseband filter <NUM> includes an output 530B coupled to an input 532A of the integrator <NUM>, and an output 530C coupled to an ADC <NUM>. The ADC <NUM> may be a delta-sigma ADC. The integrator <NUM> is coupled to the baseband filter <NUM> to match the impedance and loading presented to the baseband filter <NUM> to the impedance and loading presented to the baseband filter <NUM> of the Q channel.

In the Q channel, the mixer <NUM> includes an input 528A coupled to the output 524C of the phase shifter <NUM> via the LNA <NUM>, an input 528B coupled to an output 518C of the I/Q signal generator <NUM> via the buffer <NUM>, and an output 528C coupled to an input 534A of the baseband filter <NUM>. The baseband filter <NUM> includes an output 534B coupled to an input 536A of the integrator <NUM>, and an output 534C coupled to an ADC <NUM>. The ADC <NUM> may be a delta-sigma ADC.

The phase shifter <NUM> includes a signal input 524A that is coupled to an output of the LNA <NUM>, a control input 524B that is coupled to an output 536B of the integrator <NUM>, and an output 524C that is coupled to the mixer <NUM> and the mixer <NUM>. The integrator <NUM> compares the output of the baseband filter <NUM> to zero and integrates the difference to generate a control signal <NUM> for the phase shifter <NUM>. The phase shifter <NUM> receives the reflected radar signals and shifts the phase of the reflected radar signals based on control signal <NUM>. The baseband filter <NUM> and the integrator <NUM> are part of a feedback path that is coupled between the output 528C of the mixer <NUM> and the control input 524B of the phase shifter <NUM>. The control signal <NUM> shifts the frequency of the reflected radar signals to match the frequency shift of a transmitted frequency ramp as reflected by strong reflector, and forces the phase shift of the local oscillator and the reflected radar signal provided to the mixer <NUM> to <NUM>°. The frequency and phase adjustments minimize DC in the Q channel, and maximize DC in the I channel, thereby putting the I channel in AN condition and eliminating the effects of phase noise of the RF synthesizer <NUM> and UPN on SNR of the receiver <NUM> in the I channel.

In the receiver <NUM>, the receiver <NUM>, and the receiver <NUM> the phase and frequency of the local oscillator signal applied in the receiver is shifted to suppress phase noise in the receiver. <FIG> shows a block diagram for a radar system <NUM> that includes a phase shifter in the transmitter rather than the receiver. The radar system <NUM> includes a radar transceiver <NUM>, an antenna <NUM>, an antenna <NUM>, and an RF synthesizer <NUM>. The antenna <NUM> is coupled to the radar transceiver <NUM> for reception of reflected radar signals. The antenna <NUM> is coupled to the radar transceiver <NUM> for transmission of radar signals. The RF synthesizer <NUM> is coupled to the radar transceiver <NUM>, and generates the local oscillator signal <NUM> that is transmitted by the radar transceiver <NUM> and used by the radar transceiver <NUM> to down-convert received radar reflections.

The radar transceiver <NUM> includes a receiver <NUM> and a transmitter <NUM>. The transmitter <NUM> includes a power amplifier <NUM> and a phase shifter <NUM>. An input 624A of the phase shifter <NUM> is coupled to the RF synthesizer <NUM> for receipt of the local oscillator signal <NUM>. An output 624C of the phase shifter <NUM> is coupled to the power amplifier <NUM> for transmission of the local oscillator signal <NUM> as shifted by the phase shifter <NUM>. The receiver <NUM> includes an LNA <NUM> coupled to an I channel and a Q channel, and an I/Q signal generator <NUM>. The I/Q signal generator <NUM> receives the local oscillator signal <NUM> at an input 618A and generates in-phase and quadrature phase versions of the local oscillator signal <NUM>. The I channel includes an LNA <NUM>, a mixer <NUM>, a baseband filter <NUM>, and an integrator <NUM>. The Q channel includes an LNA <NUM>, a mixer <NUM>, a baseband filter <NUM>, and an integrator <NUM>. The mixer <NUM> includes an input 616A coupled to the LNA <NUM>, an input 616B coupled to an output 618B of the I/Q signal generator <NUM> via the buffer <NUM>, and an output 616C coupled to an input 630A of the baseband filter <NUM>. The baseband filter <NUM> includes an output 630B coupled to an input 632A of the integrator <NUM>, and an output 630C coupled to an ADC <NUM>. The ADC <NUM> may be a delta-sigma ADC. The integrator <NUM> is coupled to the baseband filter <NUM> to match the impedance and loading presented to the baseband filter <NUM> to the impedance and loading presented to the baseband filter <NUM> of the Q channel.

In the Q channel, the mixer <NUM> includes an input 628A coupled to the LNA <NUM>, an input 628B coupled to an output 618C of the I/Q signal generator <NUM> via the buffer <NUM>, and an output 628C coupled to an input 634A of the baseband filter <NUM>. The baseband filter <NUM> includes an output 634B coupled to an input 636A of the integrator <NUM>, and an output 634C coupled to an ADC <NUM>. The ADC <NUM> may be a delta-sigma ADC. The integrator <NUM> compares the output of the baseband filter <NUM> at the output 634B to zero and integrates to generate a control signal <NUM> for the phase shifter <NUM>.

The phase shifter <NUM> includes an input 624A that is coupled to an output of the RF synthesizer <NUM>, a control input 624B that is coupled to an output 636B of the integrator <NUM>, and an output 624C that is coupled to the power amplifier <NUM>. The phase shifter <NUM> receives the local oscillator signal <NUM> generated by the RF synthesizer <NUM> and shifts the phase of the local oscillator signal <NUM> based on the control signal <NUM>. The baseband filter <NUM> and the integrator <NUM> are part of a feedback path that is coupled between the output 628C of the mixer <NUM> and the control input 624B of the phase shifter <NUM>. The control signal <NUM> shifts the frequency of the local oscillator signal <NUM> to match the frequency shift of the frequency ramp of the radar signal reflected by reflector <NUM>, and forces the phase shift of the shifted local oscillator and the reflected radar signal provided to the mixer <NUM> to <NUM>°. The frequency and phase adjustments minimize DC in the Q channel, and maximize DC in the I channel, thereby putting the I channel in AN condition and eliminating the effects of phase noise of the RF synthesizer <NUM> and UPN on SNR of the receiver <NUM> in the I channel.

<FIG> shows equations used to determine and set loop bandwidth for cancellation of vibration of a strong reflector in this description. The bandwidth of the feedback loop <NUM> is: <MAT> where:.

The bandwidth of the feedback loop <NUM> is set to track vibrations of the strong reflector <NUM>.

<FIG> shows an example simulation of amplitude noise and uncorrelated phase noise produced using a feedback loop in this description. The amplitude noise level generated at the output of the in-phase mixer <NUM> of the feedback loop <NUM> is a good match with the amplitude noise level measured at the ADC <NUM> in the receiver <NUM>. The phase noise level also matches the phase noise at the ADC <NUM> if the large signal noise factor of the LNA <NUM> is treated as uncorrelated phase noise.

<FIG> shows an example vehicle <NUM> that includes a radar system having a phase/frequency feedback loop in this description. The vehicle <NUM> includes a radar system <NUM> and a computer system <NUM>. The radar system <NUM> is, for example, an implementation of the radar system <NUM>, the radar system <NUM>, the radar system <NUM>, or a radar system that includes the receiver <NUM>, or the radar system <NUM> described herein. The noise floor of the radar system <NUM> in the vehicle <NUM> may be improved by up to <NUM> dB or more relative to other radar system implementations, which improves detection range.

The radar system <NUM> provides radar signals <NUM> to the computer system <NUM>, and the computer system <NUM> processes the radar signals <NUM> to identify objects in the environment of the vehicle <NUM> and control the vehicle <NUM> based on the identified objects. The computer system <NUM> may be mounted anywhere in the vehicle <NUM>, and the radar system <NUM> may be mounted adjacent any outer surface of the vehicle <NUM>. The computer system <NUM> includes one or more processors (e.g., general-purpose microprocessors, microcontrollers, digital signal processors, etc.) that process the radar signals <NUM>. The computer system <NUM>, based on identification of an object via the radar system <NUM>, may control autonomous driving of the vehicle <NUM>, control automated parking of the vehicle <NUM>, control blind spot monitoring in the vehicle <NUM>, control a cruise control system of the vehicle <NUM>, or control other automotive system of the vehicle <NUM>.

<FIG> shows a flow diagram for a method <NUM> for controlling a vehicle using a radar receiver having a phase/frequency feedback loop in this description. Though depicted sequentially as a matter of convenience, at least some of the actions shown can be performed in a different order and/or performed in parallel. Also, some implementations may perform only some of the actions shown. Operations of the method <NUM> may be performed by an implementation of the vehicle <NUM>. While the method <NUM> is described with reference to the radar system <NUM>, the method <NUM> is applicable to use of any of the receivers described herein.

In block <NUM>, the radar system <NUM> receives radar signals reflected from objects in the operating environment of the vehicle <NUM>.

In block <NUM>, the radar system <NUM> mixes the received radar signals with I and Q versions of the local oscillator signal <NUM> in the mixer <NUM> and the mixer <NUM>.

In block <NUM>, the radar system <NUM> filters the I and Q mixer outputs. More specifically, the radar system <NUM> filters the output of the mixer <NUM> and the mixer <NUM> in the baseband filter <NUM> and the baseband filter <NUM>.

In block <NUM>, the radar system <NUM> integrates the Q filter output. More specifically, the radar system <NUM> filters the output of the baseband filter <NUM> in the integrator <NUM>.

In block <NUM>, the radar system <NUM> phase modulates the local oscillator signal <NUM> used generate the I and Q oscillator signals. More specifically, the radar system <NUM> applies the output of the integrator <NUM> to phase modulate the local oscillator signal <NUM> used to generate the I and Q oscillator signals.

In block <NUM>, the radar system <NUM> digitizes the filter output. More specifically, the radar system <NUM> digitizes the output signal of the baseband filter <NUM> and the baseband filter <NUM> in the ADC <NUM> and the ADC <NUM>. The radar system <NUM> provides the digitized radar signals to the computer system <NUM>.

In block <NUM>, the computer system <NUM> identifies an object based on digitized radar signals. More specifically, the computer system <NUM> processes the digitized radar signals to identify an object in the operational environment of the vehicle <NUM>.

In block <NUM>, the computer system <NUM> controls the vehicle <NUM> based on the object identified in block <NUM>. For example, the computer system <NUM>, based on identification of an object, may control autonomous driving of the vehicle <NUM>, control automated parking of the vehicle <NUM>, control blind spot monitoring in the vehicle <NUM>, control cruise control of the vehicle <NUM>, or control other automotive system of the vehicle <NUM>.

Claim 1:
A device, comprising:
a radar receiver (<NUM>) comprising an analog control loop for cancelling frequency shift and phase shift caused by a strong reflector;
the analog control loop comprising:
a phase shifter (<NUM>) comprising:
a signal input (124A) configured to receive a local oscillator signal (<NUM>);
a control input (124B); and
an output (124C);
an in phase channel/quadrature phase channel, I/Q, signal generator (<NUM>), comprising:
an input (118A) coupled to the output (124C) of the phase shifter (<NUM>);
a first output (118B); and a second output (118C);
a first mixer (<NUM>) comprising an input (116B) coupled to the first output (118B) of the I/Q signal generator (<NUM>);
a second mixer (<NUM>) comprising an input (128B) coupled to the second output (118C) of the I/Q signal generator (<NUM>);
a baseband filter (<NUM>), the input (134A) of the baseband filter (<NUM>) coupled to an output (128C) of the second mixer (<NUM>);
an integrator (<NUM>), the output (134B) of the baseband filter (<NUM>) coupled to an input (136A) of the integrator (<NUM>); and
a feedback path coupled between an output (136B) of the integrator (<NUM>) and the control input (124B) of the phase shifter (<NUM>);
wherein the phase shifter (<NUM>) is configured for shifting the phase of the local oscillator signal (<NUM>) based on a control signal (<NUM>).