Low Probability of Intercept Altimeters (LPIA)

The LPIA was developed and tested by the U.S. Navy for tri-service use. At its core is a high-speed digital signal processor and radio frequency module, operating on a frequency-hopped, spread-spectrum, phase-encoded, low-power signal waveform.

This highly effective waveform and signal processing allows the LPIA to extend altimeter accuracy, performance envelope (roll, pitch, and altitude), jamming resistance, and low probability of intercept capabilities far beyond existing altimeters.

High gain achieved in the receiver signal processing yields to low power output, resulting in a simple radio frequency design and eliminating multiple power amplifier circuits. These unique features help drive the in-field reliability to greater than 6800 hours.

The LPIA modular design has complete backward compatibility with existing installations of the APN-194, APN-232, APN-209, and APN-171, eliminating A-kit costs by using interchangeable front panels, mounting plates, analog input and output cards, and reuse of existing antennas. The common design reuses five of the seven subassemblies in all configurations, which lets users share cost savings from a broader production base. High reliability and extensive BIT coverage supports cost-effective maintenance with minimal replacement and pipeline spare requirements. Waveform and signal processing are all software controlled, allowing custom performance. Software is field-reprogrammable, keeping installation and maintenance costs low.

LPIA benefits

• Minimal probability of detection provided by low-wattage beam, increasing mission success
• High jam resistance
• Low life-cycle cost and high dependability
• Reduced logistics burden through enhanced testability features
• High accuracy at all altitudes and attitudes
• Software-based processing allows for easy modification to meet new requirements
• High commonality across system variants