Harris Corporation

George M Walley

William Dean Killen

Michael Paul Zeitfuss

Daniel L Boritzki

Michael James Lynch

Charles Michael Newton

Roy A Vaninetti

Laurence S D'Agati

The bandwidth of a 'single loop' bit synchronizer is maintained constant over a relatively wide baud rate range, by making the loop's phase/frequency detector gain constant proportional to the loop's clock divider ratio. The phase/frequency detector may include charge pump that charges a capacitor with a current representative of the phase/frequency difference between an input data signal and the clock signal produced by the loop's clock divider. By resistor-coupling the loop filter to the capacitor, the loop filter sees a voltage that is proportional to the integral of the phase/frequency detector's output current over the symbol period of the received data signal. Since the data symbol period is the inverse of the data rate, and corresponds to the ratio of the clock frequency divisor N to the fixed output frequency produced by the VCO, the gain constant of the phase detector is proportional to the clock divisor N. Since loop bandwidth is defined in accordance with the ratio of the phase detector gain constant (which is proportional to N) to the clock divisor N, the contribution of the clock frequency divisor N is canceled, so that the loop bandwidth can be maintained constant regardless of data rate (which sets N).

Multiple data rate bit synchronizer having phase/frequency detector gain constant proportional to PLL clock divider ratio

An antenna test range uses direct spread-spectrum based test signals to test the performance of an antenna. Since a spread spectrum waveform has high autocorrelation properties with itself and high cross-correlation properties with signals other than itself, in the receiver coupled to the antenna it is possible to effectively electronically reject all unwanted signals that may be present in the test range, and thereby allow both main beam and off-axis performance of the antenna to be completely and accurately measured.

Mitigation of antenna test range impairments caused by presence of undesirable emitters

An antenna test range uses a direct spread-spectrum based test signal to effectively electronically reject all unwanted signals that may be present in the test range, and thereby allow both main beam and off-axis performance of the antenna to be completely and accurately measured. For increased dynamic range, the test signal comprises a carrier signal that is sequentially modulated with low rate, respectively different, direct spreading PN sequences applied to a cascaded plurality of N mixer stages through successive ones of which the carrier signal is coupled. The plurality of PN spreading sequences are mutually offset in time by a fraction of a chip, and thereby produce, at an output of an Nth mixer stage, a direct sequence spread spectrum carrier signal having its energy spread out over a bandwidth that is N times the spreading bandwidth of an individual one of the PN spreading sequences.

Extension of dynamic range of emitter and detector circuits of spread spectrum-based antenna test range

An RF interface is configured as a laminate structure having a core layer of a ferromagnetic ceramic material, such as barium strontium titanate, whose permitivity is electrically controllable to modify the behavior of impinging electromagnetic energy, as one of minimally attenuated transmission, maximally attenuated absorption, and highly unattenuated reflection. Opposite surfaces of the ceramic core are coated with an electrically lossy material, such as indium tin oxide, to which a differential DC voltage is applied, and thereby imparting a DC electric field to the core layer. For an antenna application, during transmit/receive mode, the differential voltage has a magnitude that renders the laminate's core highly conductive, and thereby reflective to the RF wavelength being sourced from or received by an associated feed horn. During other times, the differential voltage renders the laminate effectively transparent to RF wavelengths in a prescribed band of interest (e.g., a search radar emanating from a threat platform, such as an aircraft).

Antenna having electrically controllable radar cross-section

In order to rapidly acquire and track a clock signal embedded in a reduced length synchronization preamble, a bit synchronizer contains a digital counter, which counts clock signals from a local clock generator having a frequency that is a multiple of the frequency of the data modulations in the received signal. The inverse of the most significant bit output of the counter sources the regenerated clock signal. In response to transitions in the monitored signal, the contents of the counter are coupled to an accumulator to provide successive measures of the (phase) difference between the times of occurrence of the regenerated clock signal and the actual times of occurrence of the sync preamble transitions. The contents of the accumulator are averaged over a prescribed number of monitored transitions and the resulting average is coupled to comparator, which compares the phase difference average output of the accumulator with the contents of the counter. When the phase difference average coincides with the contents of the counter, the counter is reset, thereby aligning the phase of the regenerated clock with that of the monitored signal. In addition, as the accumulator is updated, its input values from the counter are made available over a separate dedicated output link, to permit an attendant communications control processor to monitor the tracking performance of the apparatus.

Growing community of inventors

San Jose, CA, United States of America

George M Walley