Aircraft vision system Analog Front End

  • Automotive
  • High Voltage

AnSem · Aircraft vision system Analog Front End

The real world problem

In-vehicle cameras displaying real time driver's aid video are rapidly becoming standard in high-end cars. Imagine how valuable that additional real time video feed would be in an aircraft. However, aviation is a much more demanding market than automotive in many ways not least the longer service life of aircraft which necessitates the ability to retrofit new technologies into older aircraft.

Understanding that taking an aircraft out of service for a wiring refit is prohibitively expensive, Edgewater Computer Systems, Inc (ECSI) developed "Extended 1553" (E1553®), an avionics grade VHDSL-like overlay network on top of the existing Mil-Std-1553B in-aircraft data bus network wiring allowing the wiring to be used in new high-performance applications, such as a real time video network, without affecting the legacy network running underneath. E1553® is an adaptation of ECSI's commercial Xi-Channel® networking technology for hard real-time industrial applications.

The Analog Front End (AFE) for the Xi-Channel® system was particularly challenging in terms of high speed, high precision Analog-to-Digital and Digital-to-Analog converters, a high power, high linearity, high frequency PA and accurate, effective filtering. Worse, the AFE had to maintain this performance over temperatures of -65°C to +125°C.

The solution

ECSI came to AnSem for the design of an AFE that met the Xi-Channel® system requirements. A two die solution was devised with the PA and line interface designed in high voltage 0.18µm BCD CMOS and the remaining circuitry in 0.13µm CMOS to take advantage of the higher frequency transistors and lower power of this technology. A full MATLAB™ system model built by AnSem during the architectural design phase allowed the exploration of which system tradeoffs could be made without sacrificing performance of the Xi-Channel®. A 160Ms/s, 12 bit ADC and 240Ms/s 12 bit DAC formed the heart of the AFE supported by an on chip fractional-N synthesizer and highly accurate, on chip multi-pole filters featuring on-chip calibration. The AFE dies sit alongside ECSI's Xi-Channel® digital modem device inside a hermetically sealed MCM.

Result for the customer

AnSem is almost unique in having the rigor of ISO9001:2008, the breadth of expertise in analog system design and the flexibility to work closely with ECSI on the design of the Xi-Channel® AFE. AnSem and ECSI jointly specified the AFE design to meet the tight performance, environmental and power consumption goals required to realize a system suitable for the avionics market.

Key technical statistics

  • 12 bit 160Ms/s low power pipelined ADC
  • 12 bit 240Ms/s DAC featuring up-sampling FIR filter to ease TX filtering requirements
  • Fractional-N synthesizer featuring 1.98GHz PLL, low jitter and avionics temperature range
  • High power (+20dBm into 39Ω), high linearity (50dB MTPR) Power Amplifier