Raytheon Company

Richard G Berard

Robert G Curtis

Randall L Baumbach

Macdonald J Andrews

Arnold E Vandoren

Gary H Hochstadt

A PCMCIA electronics package adapted to enclose, and provides EMI shielding to, a printed circuit board (PCB). The PCB has an electrical connector adapted for plugging into a computer is at a one end and RF circuitry at the other end. Electronic components are disposed on an inner region of the surfaces of the PCB. The PCB has a ground plane conductor disposed therein. Electrically conductive strips are disposed on the surfaces of the PCB along opposing side edges and the other end of the PCB. A plurality of conductive vias pass through a portion of the PCB electrically connecting the electrical strip conductors to the ground plane conductor. A plurality of resilient, electrically conductive clips is provided. Each one of the clips has: a cup-shaped region disposed over a corresponding one of the PCB edges and the other end of the PCB. Side portions of the cup-shaped regions are in contact with conductive strips. The clips have an arm with a distal end elevated from the PCB. The package includes a pair of electrically conductive covers disposed over the PCB and in contact with the distal ends of the arms. Each clip is elongated and has an array of slots disposed in the distal end of the arm. The arm has a intermediate portion adjacent to the edge of the printed circuit board and the distal end of the arm curves outwardly from the intermediate portion of the arm.

Electronics package having electromagnetic interference shielding

A timing recovery apparatus for a burst mode communication receiver. The apparatus provides for optimum sampling and digitizing of received data at a plurality of data rates. In particular, a VCO is phase-locked to a local frequency reference prior to data being received. A reference timing preamble transmitted prior to the data is filtered and fed to the VCO causing it to injection lock such that the VCO becomes phase aligned with the preamble. The VCO is then permitted to 'free run' during data transmission and continues to operate at substantially the same frequency. A synchronous divider and multiplexer, responsive to the VCO, allows selection of sampling clocks for the plurality of data rates. The divider is forced to a known state during VCO injection locking, to assure that the sampling clocks have maintained the proper phase for optimal sampling at the corresponding data rate. Further, means is provided to monitor the frequency of the VCO. Should the VCO frequency drift more than a predetermined amount an indication of such is produced.

Timing recovery scheme for burst communication systems having a VCO with

Timing recovery scheme for burst communication systems

A receiver including two optimizers for demodulation, sampling and quantization of received QPSK digital data. One optimizer adjusts the phase of a reference signal used for demodulating the QPSK data into baseband in-phase and quadrature channels and another optimizer adjusts a sampling clock used to sample and quantize the baseband channels. The reference signal and the sampling clock are dithered in quadrature. Variations in the amplitude of the quantized data extracted by an eye quality monitor. Each optimizer multiplies the eye quality monitor output by a corresponding dither clock and integrates to form an error signal. Phase shifters, responsive to corresponding error signals and dithered clocks, adjust the phase of the demodulation reference signal and sampling clock. The data quality signal monitor translates the magnitude of the quantized data signals to a common set of signals for each state of the data signal. These common signals are translated into a voltage representing the degree to which the data signal amplitude corresponds to a predetermined value. Additionally, a phase shifter is shown which splits its input signal into two signals in quadrature. Theses two signals, when multiplied by two corresponding values and the products summed, form a phase shifted version of the input signal. The two values correspond to a nominal phase shift and vary to impart a linear phase change to the input signal proportional to a control voltage.

QPSK demodulator

A receiver including two optimizers for demodulation, sampling and quantization of received QPSK digital data. One optimizer adjusts the phase of a reference signal used for demodulating the QPSK data into baseband in-phase and quadrature channels and another optimizer adjusts a sampling clock used to sample and quantize the baseband channels. The reference signal and the sampling clock are dithered in quadrature. Variations in the amplitude of the quantized data extracted by an eye quality monitor. Each optimizer multiplies the eye quality monitor output by a corresponding dither clock and integrates to form an error signal. Phase shifters, responsive to corresponding error signals and dithered clocks, adjust the phase of the demodulation reference signal and sampling clock. The data quality signal monitor translates the magnitude of the quantized data signals to a common set of signals for each state of the data signal. These common signals are translated into a voltage representing the degree to which the data signal amplitude corresponds to a predetermined value. Additionally, a phase shifter is shown which splits its input signal into two signals in quadrature. These two signals, when multiplied by two corresponding values and the products summed, form a phase shifted version of the input signal. The two values correspond to a nominal phase shift and vary to impart a linear phase change to the input signal proportional to a control voltage.

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Chelmsford, MA, United States of America

Richard G Berard