Date: Mar 06, 2014 Source: Company Data (
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Bedford Signals Corporation has delivered a prototype Low Latency Self Calibrating Programmable RF Filter-Equalizer. This filter uses advanced DSP techniques to implement low latency tunable filters that can be programmed over a wide range of bandwidths along with user specified equalization. The project was selected under the highly competitive Small Business Innovation Research (SBIR) Phase II solicitation by the United States Army.
The Army was looking to research and develop a programmable multichannel radio frequency filter-equalizer having a programmable number of channels, each programmable with potentially unequal spacing, bandwidth, and equalization. The challenging goals included low latency, narrow channel bandwidth, wide instantaneous bandwidth, and high dynamic range. Bedford Signals' approach to meeting the objectives was to combine our capabilities in high precision high bandwidth custom DSP hardware with our expertise in digital filtering and calibration. Phase I consisted of a comprehensive study of hardware architectures, FPGA building blocks, filter architectures, filter design algorithms, and calibration/equalization algorithms. Phase II tasks included integrating equalization and calibration algorithms, and merge them into a low latency version of our frequency hopping notch filter architecture implemented on a custom card.
Our prototype is a 6U-160 CompactPCI Serial Eurocard implementing up to six low latency programmable filter channels covering 20 to 300 MHz center frequency, nominal channel bandwidth from less than 15 KHz to over 100 MHz, calibrated flatness ±0.1 dB ±0.2 nS, 90 dB stopband rejection, transition bandwidth less than 1 passband width, and about 88 nS latency. Filters having programmable channel bandwidth, passband ripple, stop band rejection, and transition bandwidth are designed using a GUI that incorporates "draw your own response" User Equalization. The desktop GUI controls the card using a SCPI-like protocol over Gigabit Ethernet. Internal loopback supports self calibration using just on board components. Calibration data can be merged with the filter design to improve gain and delay flatness along with image rejection.
The current product supports very low latency, high instantaneous dynamic range and bandwidth, and very narrow channel bandwidth for band pass and/or band reject filters. It is suitable for use in applications that require programmable filtering with equalization or calibration to account for distortion in other subsystems. With minor software modifications it can be customized to emulate target reflections or frequency dependent fading. Delay limits the minimum distance that can be emulated, so our low latency design is critical for these applications. Combined with our patented Multiple Channel Waveform Generator with Dynamic Delay Emulation the hardware can generate ultra-wideband signals feeding a phased array or MIMO transmitter. The same technique can emulate the received phased array or MIMO signal for testing. Applications include testing and subsystems for RADAR, GPS, communications, jamming, and anti-jam.
Bedford Signals Corporation is a privately held company, established in May of 2003 to hurdle the challenges of high bandwidth Digital Signal Processing for Satellite and Terrestrial Communications Systems. Core competencies include communications systems, networks, and protocols - with a focus on sophisticated spatial and temporal array processing for wireless communications systems.
