chip scale atomic clock
Microsemi’s new SA.45s chip-scale atomic oscillator outputs a 10-MHz, 3.3Vsquare wave and a 400-nsec, 1-pulse/sec signal. You can use an RS-232 interface to the device’s internal DSP to provide status and modify the pulse output. The SA.45s hasa center-frequency accuracy of ±5×10−11 and can survive 500g shock on any axis. It occupies16 cc of volume, weighs 35g, and requires115 mW of power. Allan-deviation stability is2×10−10 over a tau of 1 sec. The device features SSB (single-sideband) RF-output phase noise at 1 Hz of less than −53 dBc (decibels referred to carrier)/Hz. With a 110-second warm-up,the oscillator has MTBF (mean time between failures) of greater than 100,000 hours.
microsemi
Alternative PNT systems (A-PNT)
The Army is in the midst of testing new assured position, navigation and timing equipment (A-PNT) as it searches for more ways to thwart jamming and spoofing and stay operational if GPS is denied or unavailable.
The tests support the Mounted Assured PNT System or MAPS program, which is working to replace multiple hand-held Defense Advanced GPS Receivers (DAGRs) with a single receiver, thereby reducing the SWAP — that is the size, weight and power — that must be allowed for in equipment design and integration.
In addition to atomic clocks the Army is looking at other ways of getting or devising PNT data including using, for example,
- signals from other GNSS constellations,
- timing information from cross-linked communication satellites and
- developments in real-time imaging and mapping.
- vision-based navigation
- M-code:
Until now, the military has relied on the encrypted P(Y) code to provide advantage on the battlefield. Compared to the civilian C/A code, the P(Y) offered improved accuracy, ionospheric correction, resistance to spoofing and a marginal level of jamming resistance.
This power spectral density can be seen in the figures below, along with legacy C/A and P(Y) codes (and also the new L2C signal on L2).
The M-code BOC signal is able to support navigation warfare activities. Because the energy in the signal is spread in two lobes away from the center, it allows for the C/A code to be selectively jammed without affecting the military receivers. This is often referred to as “blue force jamming” or “blue on blue jamming,” where friendly forces might wish to perform jamming in an environment in which they are themselves operating. Currently, such blue force jamming is not possible with P(Y) code receivers, without also degrading the friendly force’s receiver.
Another promise of M-code is the ability to use spot-beam transmissions from Block III satellites. This is where a high-gain antenna on the satellites aims the M-code signal at a specific region of the earth, with much greater received satellite power in that region. The received signal from the spot beam is expected to be around 20-dB more powerful than the conventional full-Earth coverage beam. This means that, in a given conflict region, military GPS receivers should be able to benefit from a large increase in jamming resistance.
The US Army will field a system called Mounted Assured Positioning, Navigation and Timing, or MAPS, on some of the regiment’s vehicles — news first reported by Inside the Army. The system uses the Selective Availability Anti-Spoofing Module for GPS, a chip-scale atomic clock for timing an anti-jamming antenna to distribute position, navigation and timing information across a unit’s mission equipment.
The 1st Generation (Gen-1) version of the MAPS GPS system was developed by General Dynamics Mission Systems subsidiary, GPS Source, Inc. These jam-resistant GPS systems are designed to provide trusted and reliable positioning, navigation, and timing data, independent of the availability or integrity of GPS signals.
The MAPS Gen-1 system includes GPS Source’s latest Assured Positioning, Navigation, & Timing (APNT) products:
Microsemi’s new SA.45s chip-scale atomic oscillator outputs a 10-MHz, 3.3Vsquare wave and a 400-nsec, 1-pulse/sec signal. You can use an RS-232 interface to the device’s internal DSP to provide status and modify the pulse output. The SA.45s hasa center-frequency accuracy of ±5×10−11 and can survive 500g shock on any axis. It occupies16 cc of volume, weighs 35g, and requires115 mW of power. Allan-deviation stability is2×10−10 over a tau of 1 sec. The device features SSB (single-sideband) RF-output phase noise at 1 Hz of less than −53 dBc (decibels referred to carrier)/Hz. With a 110-second warm-up,the oscillator has MTBF (mean time between failures) of greater than 100,000 hours.
microsemi
Alternative PNT systems (A-PNT)
The Army is in the midst of testing new assured position, navigation and timing equipment (A-PNT) as it searches for more ways to thwart jamming and spoofing and stay operational if GPS is denied or unavailable.
The tests support the Mounted Assured PNT System or MAPS program, which is working to replace multiple hand-held Defense Advanced GPS Receivers (DAGRs) with a single receiver, thereby reducing the SWAP — that is the size, weight and power — that must be allowed for in equipment design and integration.
In addition to atomic clocks the Army is looking at other ways of getting or devising PNT data including using, for example,
- signals from other GNSS constellations,
- timing information from cross-linked communication satellites and
- developments in real-time imaging and mapping.
- vision-based navigation
- M-code:
Until now, the military has relied on the encrypted P(Y) code to provide advantage on the battlefield. Compared to the civilian C/A code, the P(Y) offered improved accuracy, ionospheric correction, resistance to spoofing and a marginal level of jamming resistance.
M-code is quite a different picture. Rather than the traditional BPSK
modulation schemes used by legacy signals, M-code utilizes a type of
binary offset carrier (BOC) signal. In the case of M-code, the signal is
a BOCsin(10,5) modulation, which has a power spectral density given by:
This power spectral density can be seen in the figures below, along with legacy C/A and P(Y) codes (and also the new L2C signal on L2).
The M-code BOC signal is able to support navigation warfare activities. Because the energy in the signal is spread in two lobes away from the center, it allows for the C/A code to be selectively jammed without affecting the military receivers. This is often referred to as “blue force jamming” or “blue on blue jamming,” where friendly forces might wish to perform jamming in an environment in which they are themselves operating. Currently, such blue force jamming is not possible with P(Y) code receivers, without also degrading the friendly force’s receiver.
Another promise of M-code is the ability to use spot-beam transmissions from Block III satellites. This is where a high-gain antenna on the satellites aims the M-code signal at a specific region of the earth, with much greater received satellite power in that region. The received signal from the spot beam is expected to be around 20-dB more powerful than the conventional full-Earth coverage beam. This means that, in a given conflict region, military GPS receivers should be able to benefit from a large increase in jamming resistance.
The US Army will field a system called Mounted Assured Positioning, Navigation and Timing, or MAPS, on some of the regiment’s vehicles — news first reported by Inside the Army. The system uses the Selective Availability Anti-Spoofing Module for GPS, a chip-scale atomic clock for timing an anti-jamming antenna to distribute position, navigation and timing information across a unit’s mission equipment.
The 1st Generation (Gen-1) version of the MAPS GPS system was developed by General Dynamics Mission Systems subsidiary, GPS Source, Inc. These jam-resistant GPS systems are designed to provide trusted and reliable positioning, navigation, and timing data, independent of the availability or integrity of GPS signals.
The MAPS Gen-1 system includes GPS Source’s latest Assured Positioning, Navigation, & Timing (APNT) products:
- Enhanced D3 (ED3) Receiver – Provides access to SAASM and M-Code protected GPS data
- VICTORY CSAC Accessory Module (VCAM) – Contains a Chip Scale Atomic Clock (CSAC), software designed for electronic surveillance / electronic protection (ES/EP), and allows for integration of other solutions such as an Inertial Navigation System (INS) and anti-jam antennas
- Anti-Jam Antenna System (AJAS) – Mitigates impact of enemy jammers with the use of a FRPA antenna and Anti-Jam Antenna Integration Module (AJAIM)
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