Abstract: Transistor package leads form quarter-wave antenna elements that directly radiate RF energy into free space without the need for a separate antenna. The transistor operates at a fundamental frequency and radiates a harmonic, thereby allowing radiation at frequencies normally considered “beyond cutoff” for a packaged transistor. This technique enables an additional 20 GHz of spectrum for use by surface mount technology. The transistor may be mounted on 1.6 mm thick glass-epoxy circuit board that also forms a quarter-wave reflector at 26 GHz. An optional dielectric lens produces a narrow beam and an optional planar filter rejects spurious fundamental emissions. A 26 GHz ultra-wideband (UWB) pulse-echo radar rangefinder implementation provides a low-cost upgrade to ultrasound.

Abstract: A varying magnetic field excites slight vibrations in an object and a radar sensor detects the vibrations at a harmonic of the excitation frequency. The synergy of the magnetic excitation and radar detection provides increased detection range compared to conventional magnetic metal detectors. The radar rejects background clutter by responding only to reflecting objects that are vibrating at a harmonic excitation field, thereby significantly improving detection reliability. As an exemplary arrangement, an ultra-wideband micropower impulse radar (MIR) is capable of being employed to provide superior materials penetration while providing range information. The magneto-radar may be applied to pre-screening magnetic resonance imaging (MRI) patients, landmine detection and finding hidden treasures.

Abstract: A non-contact radar sensor detects tire abnormalities such as tread delamination, sidewall ballooning, embedded nails, and impending flat or hazardous tires. The sensor also detects tire and wheel geometry errors such as out-of-round and run-out. Wheel rotational rate can be sensed for use as a speedometer or for detection of wheel lockup during braking, particularly for large trucks, or for detection of wheel slip in four-wheel drive and racing vehicles. Information from the radar sensor may be used to alert the driver or to control an antilock braking system or a traction control system. The radar sensor is preferably a range-gated 24 GHz pulse Doppler radar with spread spectrum emissions to permit four or more to operate on a single vehicle in an environment crowded with similar sensors.

Abstract: Two or more receivers of known location receive RF bursts from a wireless moving object containing a transmitter that transmits periodic RF bursts. The receivers are gated with precision swept timing that repeats at the exact transmit RF burst period to produce precision expanded time representations of the received RF bursts. The expanded time representations correspond to RF burst arrival times from the transmitter, which are used to calculate the location of the transmitter. A writing pen application includes an RF transmitter in a writing pen and four RF receivers beneath the surface of a writing tablet where RF propagation from the pen to the receivers cannot be blocked by a user's hand. Two RF transmitters, one located at each end of the pen, may be employed to measure pen tilt and for 3-D tracking. Spatial resolution is more than 600 dpi at 100 location fixes per second.

Abstract: A time-domain reflectometer (TDR) forms a pulse width modulated (PWM) signal directly on a transmission line, where the PWM width is proportional to range to a discontinuity on the transmission line. Two PWM detection methods can be used: (1) realtime, wherein the PWM signal is detected in realtime; and (2) expanded-time, wherein the PWM signal is time-expanded before detection for higher accuracy. Both methods convert the analog transmission-line PWM signal to a digital output PWM signal of identical duty-cycle for averaging, counting, or other processing to indicate range. In a preferred mode, a transmission line is sampled at a floating offset frequency relative to the transmission-line PWM frequency to form a PWM output having a floating time-expansion factor but a precise duty-cycle related to the location of the discontinuity. The essence of this TDR is low cost, precision and absolute simplicity. Applications include precision tank level sensing.

Abstract: Two or more receivers of known location receive RF bursts from a wireless moving object containing a transmitter that transmits periodic RF bursts. The receivers are gated with precision swept timing that repeats at the exact transmit RF burst period to produce precision expanded time representations of the received RF bursts. The expanded time representations correspond to RF burst arrival times from the transmitter, which are used to calculate the location of the transmitter. A writing pen application includes an RF transmitter in a writing pen and four RF receivers beneath the surface of a writing tablet where RF propagation from the pen to the receivers cannot be blocked by a user's hand. Two RF transmitters, one located at each end of the pen, may be employed to measure pen tilt and for 3-D tracking. Spatial resolution is more than 600 dpi at 100 location fixes per second.

Abstract: A pulse-echo radar measures non-contact range while powered from a two-wire process control loop. A key improvement over prior loop-powered pulse-echo radar is the use of carrier-based emissions rather than carrier-free ultrawideband impulses, which are prohibited by FCC regulations. The radar is based on a swept range-gate homodyne transceiver having a single RF transistor and a single antenna separated from the radar transceiver by a transmission line. The transmission line offers operational flexibility while imparting a reflection, or timing fiducial, at the antenna plane. Time-of-flight measurements are based on the time difference between a reflected fiducial pulse and an echo pulse, thereby eliminating accuracy-degrading propagation delays in the transmitters and receivers of prior radars. The loop-powered rangefinder further incorporates a current regulator for improved signaling accuracy, a simplified sensitivity-time-control (STC) based on a variable transconductance element, and a jam detector.

Abstract: The pulse center detector (PCD) produces an amplitude-independent center-triggered range output for precision radar rangefinders and TDR systems. Pulse center triggering is accomplished by triggering leading-edge and trailing-edge detectors and summing the outputs to produce a computed center-triggered result. Since the occurrence time of a pulse center does not vary with amplitude, the PCD is amplitude-independent. The PCD overcomes limitations of prior automatic pulse detectors, such as the inherent latency of a constant fraction discriminator (CFD) and the uncertainty of a time-of-peak (TOP) detector. The PCD can be implemented with a single analog component—a comparator—and thus requires appreciably fewer analog components than prior automatic detectors while providing lower jitter. Applications include radar and TDR tank gauges, and radar rangefinders for robotics and automotive applications.

Abstract: The pulse center detector (PCD) produces an amplitude-independent center-triggered range output for precision radar rangefinders and TDR systems. Pulse center triggering is accomplished by triggering leading-edge and trailing-edge detectors and summing the outputs to produce a computed center-triggered result. Since the occurrence time of a pulse center does not vary with amplitude, the PCD is amplitude-independent. The PCD overcomes limitations of prior automatic pulse detectors, such as the inherent latency of a constant fraction discriminator (CFD) and the uncertainty of a time-of-peak (TOP) detector. The PCD can be implemented with a single analog component—a comparator—and thus requires appreciably fewer analog components than prior automatic detectors while providing lower jitter. Applications include radar and TDR tank gauges, and radar rangefinders for robotics and automotive applications.

Abstract: A non-contact radar sensor detects tire abnormalities such as tread delamination, sidewall ballooning, embedded nails, and impending flat or hazardous tires. The sensor also detects tire and wheel geometry errors such as out-of-round and run-out. Wheel rotational rate can be sensed for use as a speedometer or for detection of wheel lockup during braking, particularly for large trucks, or for detection of wheel slip in four-wheel drive and racing vehicles. Information from the radar sensor may be used to alert the driver or to control an antilock braking system or a traction control system. The radar sensor is preferably a range-gated 24 GHz pulse Doppler radar with spread spectrum emissions to permit four or more to operate on a single vehicle in an environment crowded with similar sensors.

Abstract: A dual channel microwave sensor employs single sideband Doppler techniques in innumerable vibration, motion, and displacement applications. When combined with an active reflector, the sensor provides accurate range and material thickness measurements even in cluttered environments. The active reflector can also be used to transmit multi-channel data to the sensor. The sensor is a homodyne pulse Doppler radar with phasing-type Doppler sideband demodulation having a 4-decade baseband frequency range. Ranging is accomplished by comparing the phase of the Doppler sidebands when phase modulated by an active reflector. The active reflector employs a switch or modulator connected to an antenna or other reflector. In one mode, the active reflector is quadrature modulated to provide SSB reflections.

Abstract: A bi-static radar configuration measures the time-of-flight of an RF burst using differentially-configured sampling receivers. A precise differential measurement is made by simultaneously sampling a reference signal line and a free-space time-of-flight RF burst signal using separate sampling receivers having common sample timing. Two alternative sample timing systems may be used with the sampling receivers: (1) a swept delay using a delay locked loop (DLL), or (2) two precision oscillators slightly offset in frequency from each other. The receiver outputs are processed into a PWM signal to indicate antenna-to-antenna time-of-flight range or to indicate material properties. Applications include robotics, safety, material thickness measurement, material dielectric constant measurement, such as for fuel or grain moisture measurement, and through-tank fill-level measurement.

Abstract: A dither oscillator randomly modulates the instantaneous phase of a precision radar PRF oscillator. Radar spectral emission lines occurring at multiples of a transmit PRF oscillator are spread by the phase modulation, resulting in a continuous noise-like spectrum for reduced interference. The dither oscillator is based on a CMOS logic inverter and has adjustable coherence. The transition times of the PRF clock are decreased to 100 ps using negative resistance in an emitter follower to help injection-lock an RF oscillator to the PRF clock. Applications include spread-spectrum radar sensors operating in the crowded ISM bands, such as robotic and automotive pulse-echo rangefinders.

Abstract: A constant false alarm rate (CFAR) detector prevents false radar triggers due to RF interference by proportionally increasing the radar detection threshold as interference increases. The radar operates with a randomized PRF, which randomizes detected RF interference while maintaining echo signal coherence. Post-detection filters provide a signal channel and an interference channel. The interference channel augments the threshold of the signal threshold detector. The interference channel gain can be adjusted to ensure the detection threshold is always higher than noise in the signal channel, thereby eliminating false alarms due to RF interference. Accordingly, the CFAR detector eliminates a major false alarm nuisance, particularly in radar security sensors. Applications for the low-cost system include indoor and outdoor burglar alarms, automotive security alarms, home and industrial automation, robotics, and vehicle proximity sensors.

Abstract: A single-wire time-domain reflectometer (TDR) combines the best performance features of prior art “electronic dipsticks” in a high accuracy implementation that allows tank penetration though a small opening. A wire-horn structure is employed to launch TDR pulses onto a single wire transmission line, wherein the horn wires can be flexed inwards so the dipstick structure can be inserted through a small tank opening. Once inside the tank, the horn wires flex to their normal state to provide a controlled reference reflection while simultaneously providing high coupling efficiency to the dipstick. The TDR system determines the fill-level of a tank by measuring the time difference between a reflection created at the wire-horn, which all is at the top of a tank, and a reflection from a material in the tank. The TDR employs automatic time-of-peak (TOP) detectors and incorporates a 2-diode sampler, a low-aberration pulse generator, and a 0.001% accurate timebase.

Abstract: A range gated microwave motion sensor having adjustable minimum and maximum detection ranges with little response to close-in false alarm nuisances such as insects or vibrating panels. The sensor resolves direction of motion and can respond to target displacement in a selected direction and through a selected distance, in contrast to conventional hair-trigger motion sensors. A constant false alarm rate (CFAR) detector prevents false triggers from fluttering leaves, vibrating machinery, and RF interference. The sensor transmits an RF pulse and, after a modulated delay, mixes echo pulses with a mixer pulse. Thus, the echo pulses are modulated at the mixer output while transmit and mixer pulse artifacts remain unmodulated and easily filtered from the output. Accordingly, the sensor only responds to echoes that fall within its minimum and maximum range-gated region, and not to close-in or far-out objects.

Abstract: A single-antenna short-range radar transceiver emits 24 GHz RF sinewave packets and samples echoes with strobed timing such that the illusion of wave propagation at the speed of sound is observed, thereby forming an ultrasound mimicking radar (UMR). A 12 GHz frequency-doubled transmit oscillator is pulsed a first time to transmit a 24 GHz harmonic burst and pulsed a second time to produce a 12 GHz local oscillator burst for a sub-harmonically pumped, coherently integrating sample-hold receiver (homodyne operation). The time between the first and second oscillator bursts is swept to form an expanded-time replica of echo bursts at the receiver output. A random phase RF marker pulse is interleaved with the coherent phase transmitted RF to aid in spectrum assessment of the radar's nearly undetectable emissions.

Abstract: Two crystal oscillators are configured as a “plug-and-play” precision transmit-receive clock system that requires no calibration during manufacture. A first crystal oscillator generates a transmit clock and a second crystal oscillator generates a receive clock that operates at a small offset frequency &Dgr; from the transmit clock. A frequency locked loop regulates &Dgr; by regulating the frequency of the detected receive pulses from a radio, radar, laser, ultrasonic, or TDR system. The clock system further includes a wrong sideband reset circuit and a phase lock injection port. Applications include a timing system for automotive backup and collision warning radars, precision radar and laser rangefinders for fluid level sensing and robotics, precision radiolocation systems, and universal object/obstacle detection and ranging.

Abstract: Harmonic techniques are employed to leverage low-cost, ordinary surface mount technology (SMT) to high microwave frequencies where tight beamforming with a small antenna makes reliable, high-accuracy pulse-echo radar systems possible. The implementation comprises a 24 GHz short-pulse transceiver comprised of a pulsed harmonic oscillator employed as a transmitter and an integrating, pulsed harmonic sampler employed as a receiver. The transmit oscillator generates a very short (0.5 ns) phase-coherent harmonic-rich oscillation at a sub-multiple of the actual transmitter frequency. A receiver local oscillator operates at a sub-multiple of the transmit frequency and is triggered with controlled timing to provide a very short (0.5 ns), phase-coherent local oscillator burst. The local oscillator burst is coupled to an integrating harmonic sampler to produce an integrated, equivalent-time replica of the received RF.

Abstract: An equivalent time pulse-echo radar or other pulse-echo system employs a transmit reference sampler collocated with the transmitter to provide a transmit reference pulse, which initiates a pulse width modulated (PWM) pulse. A receive sampler connected to a receive antenna provides an echo-detection pulse that terminates the PWM pulse, such that the width of the PWM pulse indicates target range. The transmit reference sampler and the receive sampler are driven from a common clock such that transmit-receive timing offset drift precisely cancels on a picosecond scale, thereby enabling sub-mm range accuracy with common, low-cost circuit elements. The radar further includes automatically referenced pulse detectors that are responsive to either the magnitude or the phase of the sampler outputs. The radar can be used for precision tank level measurements, robotics, or automotive ranging applications.