Abstract: Two crystal oscillators are configured as a "plug-and-play" precision transmit-receive clock that requires no calibration during manufacture. A first crystal oscillator generates a transmit clock and a second crystal oscillator operates at a small offset from a harmonic of the first oscillator. A turnstile circuit selects pulses from the second oscillator to trigger a receive clock. Both the transmit and receive clocks operate at the same frequency. One edge of the receive clock is smoothly slipped, or swept, in phase across a limited range such as 0 to 36 degrees relative to the transmit clock with the slip rate set by the harmonic frequency offset. In one embodiment, a quadrature frequency-locked-loop is used to accurately control the slip rate while preventing false frequency locks. This timebase can be used to clock equivalent time radar, laser, and TDR ranging systems with picosecond accuracy.

Abstract: A wideband sample-hold circuit is formed with a single diode in a minimum component configuration. A gate circuit comprised of a first capacitor and an impedance element forms a gate pulse, stores the sampled signal charge on the first capacitor, and transfers the charge to a second capacitor via the impedance element. The impedance element also defines the gate pulse width, in combination with the first capacitor. In a preferred mode, the first capacitor is responsive to individual gate pulses while the larger second capacitor integrates charge packets from the first capacitor due to multiple gate pulses to provide an integrated baseband output. In radar rangefinder applications, the baseband output is an equivalent time replica of the RF input. The sample-hold circuit has other applications in radar motion sensing and time domain reflectomitry.

Abstract: A delay locked loop clock circuit employs an analog control loop for generating picosecond-accurate clock delays. A linear analog comparison circuit operating on integrated DC levels replaces the usual digital phase comparator for substantially improved timing accuracy. In operation, clock pulses from a first delay path are integrated and applied to a loop control amplifier. Clock pulses from a second delay path are integrated and applied to a differencing input of the loop control amplifier. The loop control amplifier regulates the delay in the second delay path to balance the integrated clock pulse voltages against externally applied control voltages. The delay between the first path and the second path is thereby precisely controlled by external voltage inputs. The first and second path clock output timing relationship is directly measured by analog voltage devices, eliminating error-prone high-speed phase comparators employed in prior art approaches.

Abstract: A pair of adjacent antennas are configured to transmit and receive wideband signals with low direct coupling. The antennas are horns with extended walls and a shaped septum. At a typical operating frequency of 5.8 GHz, coupling levels are as low as -60 dB. Low coupling levels are needed to reduce measurement errors in radar rangefinders operating at less than 1-meter target range.

Abstract: A controlled-gain amplifier has a gain control port responsive to a control voltage Vc, and produces a gain proportional to Vc raised to a fixed or continuously variable power X, such that gain=K(Vc).sup.X, where K is a constant. Precise gain control is achieved through the use of pulse width modulation (PWM) control of cascaded amplifier stages. A PWM regulator linearly controls the gain of each amplifier stage, and multiple stages are cascaded for (Vc).sup.N gain control, where N is an integer. One or more amplifier stages may contain a variable low pass filter that allows continuous control of the control exponent to produce non-integer exponents. The circuit can be used as a Sensitivity-Time-Control (STC) circuit in sampling-type radar systems, or in ultrasonic rangefinders, where the gain of the receiver needs to increase exponentially with increasing range.

Abstract: A pulsed RF oscillator employing a BIAS-ON path and a QUENCH path to produce fast turn-on and fast turn-off RF bursts with well-controlled burst width. The oscillator further includes amplitude and stability control elements, and a 5.8 GHz microstrip implementation is disclosed. The pulsed RF oscillator can be configured with quadrature RF homodyne detectors to form a range-gated pulse-Doppler motion sensor system for sensing target motion within a gated region. The sensor includes a transmitter for transmitting a sequence of RF bursts comprised of a number of cycles at the transmitter frequency. The sensor further includes a receiver responsive to the transmitted bursts and burst echoes from moving targets within its sensing field. The receiver produces Doppler signal with an amplitude representative sum of the transmitted burst and the echo burst. A Doppler motion response occurs for moving targets within a region sharply defined by the transmitted burst width.

Abstract: A pulse Doppler radar motion sensor system and method for sensing target motion within a gated region is provided with approximately constant response versus target distance. The sensor includes a transmitter for transmitting a sequence of RF bursts comprised of a number of cycles at the transmitter frequency. The transmitted burst width alternates at a pattern frequency to provide a pattern of varying burst widths. The sensor includes a receiver responsive to the transmitted bursts and burst echoes from moving targets within its sensing field. The receiver produces a pattern frequency with a signal amplitude representative of the difference in moving target response for two different range gated regions defined by the transmitted burst widths. This difference is detected to provide a range invariant target motion response in a sharply defined region. Another mode provides a quadrature receive channel for target direction determination.

Abstract: The ultra-wideband impedance sensor (UWBZ sensor, or Z-sensor) is implemented in differential and single-ended configurations. The differential UWBZ sensor employs a sub-nanosecond impulse to determine the balance of an impedance bridge. The bridge is configured as a differential sample-and-hold circuit that has a reference impedance side and an unknown impedance side. The unknown impedance side includes a short transmission line whose impedance is a function of the near proximity of objects. The single-ended UWBZ sensor eliminates the reference side of the bridge and is formed of a sample and hold circuit having a transmission line whose impedance is a function of the near proximity of objects. The sensing range of the transmission line is bounded by the two-way travel time of the impulse, thereby eliminating spurious Doppler modes from large distant objects that would occur in a microwave CW impedance bridge. Thus, the UWBZ sensor is a range-gated proximity sensor.

Abstract: A level detector or proximity detector for materials capable of sensing through plastic container walls or encapsulating materials is of the sensor. Thus, it can be used in corrosive environments, as well as in a wide variety of applications. An antenna has a characteristic impedance which depends on the materials in proximity to the antenna. An RF oscillator, which includes the antenna and is based on a single transistor in a Colpitt's configuration, produces an oscillating signal. A detector is coupled to the oscillator which signals changes in the oscillating signal caused by changes in the materials in proximity to the antenna. The oscillator is turned on and off at a pulse repetition frequency with a low duty cycle to conserve power. The antenna consists of a straight monopole about one-quarter wavelength long at the nominal frequency of the oscillator.

Abstract: An impulse forming circuit is disclosed which produces a clean impulse from a nonlinear transmission line compressed step function without customary soliton ringing by means of a localized pulse shaping and differentiating network which shunts the nonlinear transmission line output to ground.

Abstract: A radar range finder and hidden object locator is based on ultra-wide band radar with a high resolution swept range gate. The device generates an equivalent time amplitude scan with a typical range of 4 inches to 20 feet, and an analog range resolution as limited by a jitter of on the order of 0.01 inches. A differential sampling receiver is employed to effectively eliminate ringing and other aberrations induced in the receiver by the near proximity of the transmit antenna (10), so a background subtraction is not needed, simplifying the circuitry while improving performance. Techniques are used to reduce clutter in the receive signal, such as decoupling the receive (24) and transmit cavities (22) by placing a space between them, using conductive or radiative damping elements on the cavities, and using terminating plates on the sides of the openings.

Abstract: A radar range finder and hidden object locator is based on ultra-wide band radar with a high resolution swept range gate. The device generates an equivalent time amplitude scan with atypical range of 4 inches to 20 feet, and an analog range resolution as limited by a jitter of on the order of 0.01 inches. A differential sampling receiver is employed to effectively eliminate ringing and other aberrations induced in the receiver by the near proximity of the transmit antenna, so a background subtraction is not needed, simplifying the circuitry while improving performance. Uses of the invention include a replacement of ultrasound devices for fluid level sensing, automotive radar, such as cruise control and parking assistance, hidden object location, such as stud and rebar finding. Also, this technology can be used when positioned over a highway lane to collect vehicle count and speed data for traffic control.

Abstract: A non-acoustic pulse-echo radar monitor is employed in the repetitive mode, whereby a large number of reflected pulses are averaged to produce a voltage that modulates an audio oscillator to produce a tone that corresponds to the heart motion. The antenna used in this monitor generally comprises two flat copper foils, thus permitting the antenna to be housed in a substantially flat housing. The monitor converts the detected voltage to an audible signal with both amplitude modulation and Doppler effect. It further uses a dual time constant to reduce the effect of gross sensor-to-surface movement. The monitor detects the movement of one or more internal body parts, such as the heart, lungs, arteries, and vocal chords, and includes a pulse generator for simultaneously inputting a sequence of pulses to a transmit path and a grating path. The pulses transmitted along the transmit path drive Oh impulse, generator and provide corresponding transmit pulses that are applied to a transmit antenna.

Abstract: A "laser tape measure" for measuring distance which includes a transmitter such as a laser diode which transmits a sequence of electromagnetic pulses in response to a transmit timing signal. A receiver samples reflections from objects within the field of the sequence of visible electromagnetic pulses with controlled timing, in response to a receive timing signal. The receiver generates a sample signal in response to the samples which indicates distance to the object causing the reflections. The timing circuit supplies the transmit timing signal to the transmitter and supplies the receive timing signal to the receiver. The receive timing signal causes the receiver to sample the reflection such that the time between transmission of pulses in the sequence in sampling by the receiver sweeps over a range of delays.

Abstract: A radar range finder and hidden object locator is based on ultra-wide band radar with a high resolution swept range gate. The device generates an equivalent time amplitude scan with a typical range of 4 inches to 20 feet, and an analog range resolution as limited by a jitter of on the order of 0.01 inches. A differential sampling receiver is employed to effectively eliminate ringing and other aberrations induced in the receiver by the near proximity of the transmit antenna, so a background subtraction is not needed, simplifying the circuitry while improving performance. Uses of the invention include a replacement of ultrasound devices for fluid level sensing, automotive radar, such as cruise control and parking assistance, hidden object location, such as stud and rebar finding. Also, this technology can be used when positioned over a highway lane to collect vehicle count and speed data for traffic control.

Abstract: An ultra-wideband horn antenna transmits and receives impulse waveforms for short-range radars and impulse time-of flight systems. The antenna reduces or eliminates various sources of close-in radar clutter, including pulse dispersion and ringing, sidelobe clutter, and feedline coupling into the antenna. Dispersion is minimized with an abrupt launch point radiator element; sidelobe and feedline coupling are minimized by recessing the radiator into a metallic horn. Low frequency cut-off associated with a horn is extended by configuring the radiator drive impedance to approach a short circuit at low frequencies. A tapered feed plate connects at one end to a feedline, and at the other end to a launcher plate which is mounted to an inside wall of the horn. The launcher plate and feed plate join at an abrupt edge which forms the single launch point of the antenna.

Abstract: A field disturbance sensor operates with relatively low power, provides an adjustable operating range, is not hypersensitive at close range, allows co-location of multiple sensors, and is inexpensive to manufacture. The sensor includes a transmitter that transmits a sequence of transmitted bursts of electromagnetic energy. The transmitter frequency is modulated at an intermediate frequency. The sequence of bursts has a burst repetition rate, and each burst has a burst width and comprises a number of cycles at a transmitter frequency. The sensor includes a receiver which receives electromagnetic energy at the transmitter frequency, and includes a mixer which mixes a transmitted burst with reflections of the same transmitted burst to produce an intermediate frequency signal. Circuitry, responsive to the intermediate frequency signal indicates disturbances in the sensor field. Because the mixer mixes the transmitted burst with reflections of the transmitted burst, the burst width defines the sensor range.

Abstract: A bi-static radar configuration measures the direct time-of-flight of a transmitted RF pulse and is capable of measuring this time-of-flight with a jitter on the order of about one pico-second, or about 0.01 inch of free space distance for an electromagnetic pulse over a range of about one to ten feet. A transmitter transmits a sequence of electromagnetic pulses in response to a transmit timing signal, and a receiver samples the sequence of electromagnetic pulses with controlled timing in response to a receive timing signal, and generates a sample signal in response to the samples. A timing circuit supplies the transmit timing signal to the transmitter and supplies the receive timing signal to the receiver. The receive timing signal causes the receiver to sample the sequence of electromagnetic pulses such that the time between transmission of pulses in the sequence and sampling by the receiver sweeps over a range of delays.

Abstract: A safety device includes a wire loop embedded in the glass of a passenger car window and routed near the closing leading-edge of the window. The wire loop carries microwave pulses around the loop to and from a transceiver with separate output and input ports. An evanescent field only and inch or two in radius is created along the wire loop by the pulses. Just about any object coming within the evanescent field will dramatically reduce the energy of the microwave pulses received back by the transceiver. Such a loss in energy is interpreted as a closing area blockage, and electrical interlocks are provided to halt or reverse a power window motor that is actively trying to close the window.

Abstract: A micropower RF transdponder employs a novel adaptation of the superregenerative receiver wherein the quench oscillator is external to the regenerative transistor. The quench oscillator applies an exponentially decaying waveform rather than the usual sinewave to achieve high sensitivity at microampere current levels. Further improvements include circuit simplifications for antenna coupling, extraction of the detected signal, and a low-voltage bias configuration that allows operation with less than a 1-volt rail voltage. The inventive transponder is expected to operate as long as the battery shelf life.