Abstract: Systems and methods for protecting an electrical component in an alternating current system that includes a transformer are disclosed. In one aspect, a circuit includes a switch assembly connected between a transformer neutral of a transformer and a ground and having an open position and a closed position. In normal operation, the switch remains in a closed position.

Abstract: An adjustable directional coupler circuit includes a directional coupler and a correction circuit. The directional coupler includes a first port for receiving an input signal; a second port for outputting the input signal to a load; a third port for outputting a first coupled signal including a desired first coupled signal proportional to forward power of the input signal and an extraneous first coupled signal proportional to reverse power of a reflected signal; and a fourth port for outputting a second coupled signal including a desired second coupled signal proportional to the reverse power and an extraneous second coupled signal proportional to the forward power. The correction circuit adjusts magnitude and phase of a sample of the second coupled signal to provide an adjusted second coupled signal, and to sum the adjusted second coupled signal and the first coupled signal to cancel the extraneous first coupled signal.

Abstract: Detectors and other apparatus for determining the presence of electromagnetic events are disclosed. One such system includes an electromagnetically shielded enclosure and a detector configured to detect an electromagnetic field event occurring in the proximity of the enclosure. The detector includes an antenna and a circuit electrically connected to the antenna. The circuit includes electronics communicatively connected to the antenna via a direct current isolation circuit, and an equalizer compensating for the differentiating frequency response of the antenna. The circuit also includes a logarithmic amplifier electrically connected to the equalizer and configured to generate a range of signals based on signals received at the antenna, and a peak detector receiving signals from the logarithmic amplifier and configured to capture a peak value of the signals. An electromagnetic field event is detected at least in part based on the peak signal value.

Abstract: An adjustable directional coupler circuit includes a directional coupler and a correction circuit. The directional coupler includes a first port for receiving an input signal; a second port for outputting the input signal to a load; a third port for outputting a first coupled signal including a desired first coupled signal proportional to forward power of the input signal and an extraneous first coupled signal proportional to reverse power of a reflected signal; and a fourth port for outputting a second coupled signal including a desired second coupled signal proportional to the reverse power and an extraneous second coupled signal proportional to the forward power. The correction circuit adjusts magnitude and phase of a sample of the second coupled signal to provide an adjusted second coupled signal, and to sum the adjusted second coupled signal and the first coupled signal to cancel the extraneous first coupled signal.

Abstract: A method and apparatus configured to detect electromagnetic field events are disclosed. One apparatus includes an antenna and a circuit electrically connected to the antenna. The circuit includes electronics communicatively connected to the antenna via a direct current isolation circuit and an equalizer compensating for the differentiating frequency response of the antenna. The circuit also includes a logarithmic amplifier electrically connected to the equalizer and configured to generate a range of signals based on signals received at the antenna. The circuit further includes a peak detector receiving signals from the equalizer and configured to capture a peak value of the signals. The electromagnetic field event is detected at least in part based on the peak signal value.

Abstract: A method and apparatus configured to detect electromagnetic field events are disclosed. One apparatus includes an antenna and a circuit electrically connected to the antenna. The circuit includes electronics communicatively connected to the antenna via a direct current isolation circuit and an equalizer compensating for the differentiating frequency response of the antenna. The circuit also includes a logarithmic amplifier electrically connected to the equalizer and configured to generate a range of signals based on signals received at the antenna. The circuit further includes a peak detector receiving signals from the equalizer and configured to capture a peak value of the signals. The electromagnetic field event is detected at least in part based on the peak signal value.

Abstract: Detectors and other apparatus for determining the presence of electromagnetic events are disclosed. One such system includes an electromagnetically shielded enclosure and a detector configured to detect an electromagnetic field event occurring in the proximity of the enclosure. The detector includes an antenna and a circuit electrically connected to the antenna. The circuit includes electronics communicatively connected to the antenna via a direct current isolation circuit, and an equalizer compensating for the differentiating frequency response of the antenna. The circuit also includes a logarithmic amplifier electrically connected to the equalizer and configured to generate a range of signals based on signals received at the antenna, and a peak detector receiving signals from the logarithmic amplifier and configured to capture a peak value of the signals. An electromagnetic field event is detected at least in part based on the peak signal value.

Abstract: A transmission system for RF signals, power and control signals over RF coaxial cables is disclosed. A coaxial cable line interconnects two devices, such as an instrument and a remote coupler. A control signal (e.g., data bit) and RF signals are multiplexed onto the coaxial cable line using a bias network at each end of the coaxial cable. In certain embodiments, power is generated at the coupler based on the state of the control bits. Each coaxial cable carries one control bit on the center conductor of the cable. A table maps the states of the one or more control bits to the desired states in the remote coupler. The all-zeroes state for the control bits is disallowed, such that at any given time, at least one of the control lines is high (e.g., at +5V). A passive network at the coupler generates the power voltage for the coupler from the control bits. In further embodiments, a power supply filter is provided at the coupler to supply power to the coupler during transitions of the passive network.

Abstract: A network analyzer is capable of measuring the antenna return loss in a live cellular network. The network analyzer receives and analyzes the base station transmitted signal to determine which transmit frequencies are active. Based on information relating to the correlation between the transmit frequency and the associated receive frequency, the network analyzer determines the active receive frequencies. An unmodulated source that avoids inclusion of the active receive frequencies is generated by the network analyzer. To fill in the antenna sweep with the previously avoided frequencies, the network analyzer generates another source containing only those avoided frequencies when no calls are active on the avoided frequencies. Alternatively, the antenna return loss on the avoided frequencies is interpolated from the measured frequencies.

Abstract: A network analyzer is capable of measuring the antenna return loss in a live cellular network. The network analyzer receives and analyzes the base station transmitted signal to determine which transmit frequencies are active. Based on information relating to the correlation between the transmit frequency and the associated receive frequency, the network analyzer determines the active receive frequencies. An unmodulated source that avoids inclusion of the active receive frequencies is generated by the network analyzer. To fill in the antenna sweep with the previously avoided frequencies, the network analyzer generates another source containing only those avoided frequencies when no calls are active on the avoided frequencies. Alternatively, the antenna return loss on the avoided frequencies is interpolated from the measured frequencies.

Abstract: A shielded serpentine extension, internal signal path and receptor result in a flexible shielded interface for a circuit board that can be formed consistent with efficient circuit board fabrication processes. The shielded serpentine extension, continuous with the circuit board, has a receptor at an end that is distal from the circuit board. The receptor has a signal contact and a shield contact adapted to receive a surface mount connector. A signal path internal to the serpentine extension couples the signal contact of the receptor to the circuit board. The serpentine extension has shielding disposed about the signal path that couples the shield contact to the circuit board.

Abstract: A shielded serpentine extension, internal signal path and receptor result in a flexible shielded interface for a circuit board that can be formed consistent with efficient circuit board fabrication processes. The shielded serpentine extension, continuous with the circuit board, has a receptor at an end that is distal from the circuit board. The receptor has a signal contact and a shield contact adapted to receive a surface mount connector. A signal path internal to the serpentine extension couples the signal contact of the receptor to the circuit board. The serpentine extension has shielding disposed about the signal path that couples the shield contact to the circuit board.

Abstract: A high-power coupler formed from a substrate, such as a dielectric printed circuit board, is disclosed. The through arm and coupled arm(s) of the coupler have a conductor plated on the top, bottom and edges of the dielectric printed circuit board, completely enclosing the dielectric material in the conductor. A metal package surrounding the coupler forms the outer ground. Thin non-conductive struts of the dielectric material of the printed circuit board interconnect the separate arms of the coupler. The coupler may be integrated with microstrip circuitry, such as switches and resistors.

Abstract: A high-power coupler formed from a substrate, such as a dielectric printed circuit board, is disclosed. The through arm and coupled arm(s) of the coupler have a conductor plated on the top, bottom and edges of the dielectric printed circuit board, completely enclosing the dielectric material in the conductor. A metal package surrounding the coupler forms the outer ground. Thin non-conductive struts of the dielectric material of the printed circuit board interconnect the separate arms of the coupler. The coupler may be integrated with microstrip circuitry, such as switches and resistors.

Abstract: A reflection measurement method and apparatus measures reflection characteristics of a device under test (DUT) when access to the DUT is through a dispersive element. The method and apparatus measure a composite reflection response of a network that includes the DUT and the dispersive element coupled to the DUT via a transmission line. A reflection response of the dispersive element is isolated from a remainder of the composite reflection response of the network. A set of transmission parameters for the dispersive element is generated from the isolated reflection response of the dispersive element and is then applied to the remainder of the composite reflection response of the network to extract the reflection characteristic of the DUT.

Abstract: A reflection measurement method and apparatus measures reflection characteristics of a device under test (DUT) when access to the DUT is through a dispersive element. The method and apparatus measure a composite reflection response of a network that includes the DUT and the dispersive element coupled to the DUT via a transmission line. A reflection response of the dispersive element is isolated from a remainder of the composite reflection response of the network. A set of transmission parameters for the dispersive element is generated from the isolated reflection response of the dispersive element and is then applied to the remainder of the composite reflection response of the network to extract the reflection characteristic of the DUT.