Abstract: Disclosed is a system and method for widening base linear chirp signals from a first bandwidth to a larger second bandwidth while controlling the proliferation of spurious (unwanted) signals. One aspect of the invention provides for using a phase locked loop (PLL) for generating an output signal having a greater bandwidth than the bandwidth associated with the chirp signal. The PLL effectively tracks a reference signal generated at least in part by the chirp source to reduce spurious signals in the output signal. Another aspect of the invention is to use a common local oscillator in the signal transmit and receive paths to cancel consistent phase non-linearity's.

Abstract: A high frequency sweep generator uses a DDS-PLL method for frequency sweep over wide frequency spans. A digital sweep generator produces a linear ramp signal using DDS techniques that is applied to a coarse tuning port of a high frequency tunable oscillator, such as a YIG tunable oscillator (YTO). A PLL has as inputs an accurate linear swept frequency sinusoid from a DDS and a linear swept frequency output signal from the YTO to produce an error correction signal that is applied to a fine tuning port of the high frequency tunable oscillator. The error correction signal compensates for any non-linearities introduced into the linear swept frequency output signal by the high frequency tunable oscillator.

Abstract: A high frequency sweep generator uses a DDS-PLL method for frequency sweep over wide frequency spans. A digital sweep generator produces a linear ramp signal using DDS techniques that is applied to a coarse tuning port of a high frequency tunable oscillator, such as a YIG tunable oscillator (YTO). A PLL has as inputs an accurate linear swept frequency sinusoid from a DDS and a linear swept frequency output signal from the YTO to produce an error correction signal that is applied to a fine tuning port of the high frequency tunable oscillator. The error correction signal compensates for any non-linearities introduced into the linear swept frequency output signal by the high frequency tunable oscillator.

Abstract: In the method of the invention, a signal is injected into the power cord of an appliance and a reference voltage is set in response corresponding to a reference impedance at the point of signal injection. The reference impedance is present with the appliance connected to the power source. The reference voltage is continuously compared against a present voltage corresponding to present impedance at the point of signal injection. An alarm sounds if the present voltage changes to exceed the reference voltage, indicating a higher impedance because the appliance has been disconnected. In one embodiment, the apparatus includes an impedance bridge having an adjustable reference arm for producing a reference voltage corresponding to the impedance of the cord and appliance and a sensing arm for producing the present voltage. In a second embodiment, the apparatus injects an adjustable current into the power cord and appliance for a predetermined time to provide a present voltage.