Abstract: A satellite system operates at altitudes between 100 and 350 km relying on vehicles including a self-sustaining ion engine to counteract atmospheric drag to maintain near-constant orbit dynamics. The system operates at altitudes that are substantially lower than traditional satellites, reducing size, weight and cost of the vehicles and their constituent subsystems such as optical imagers, radars, and radio links. The system can include a large number of lower cost, mass, and altitude vehicles, enabling revisit times substantially shorter than previous satellite systems. The vehicles spend their orbit at low altitude, high atmospheric density conditions that have heretofore been virtually impossible to consider for stable orbits. Short revisit times at low altitudes enable near-real time imaging at high resolution and low cost. At such altitudes, the system has no impact on space junk issues of traditional LEO orbits, and is self-cleaning in that space junk or disabled craft will de-orbit.

Abstract: A satellite system operates at altitudes between 100 and 350 km relying on vehicles including a self-sustaining ion engine to counteract atmospheric drag to maintain near-constant orbit dynamics. The system operates at altitudes that are substantially lower than traditional satellites, reducing size, weight and cost of the vehicles and their constituent subsystems such as optical imagers, radars, and radio links. The system can include a large number of lower cost, mass, and altitude vehicles, enabling revisit times substantially shorter than previous satellite systems. The vehicles spend their orbit at low altitude, high atmospheric density conditions that have heretofore been virtually impossible to consider for stable orbits. Short revisit times at low altitudes enable near-real time imaging at high resolution and low cost. At such altitudes, the system has no impact on space junk issues of traditional LEO orbits, and is self-cleaning in that space junk or disabled craft will de-orbit.

Abstract: A satellite system operates at altitudes between 100 and 350 km relying on vehicles including a self-sustaining ion engine to counteract atmospheric drag to maintain near-constant orbit dynamics. The system operates at altitudes that are substantially lower than traditional satellites, reducing size, weight and cost of the vehicles and their constituent subsystems such as optical imagers, radars, and radio links. The system can include a large number of lower cost, mass, and altitude vehicles, enabling revisit times substantially shorter than previous satellite systems. The vehicles spend their orbit at low altitude, high atmospheric density conditions that have heretofore been virtually impossible to consider for stable orbits. Short revisit times at low altitudes enable near-real time imaging at high resolution and low cost. At such altitudes, the system has no impact on space junk issues of traditional LEO orbits, and is self-cleaning in that space junk or disabled craft will de-orbit.

Abstract: A satellite system operates at altitudes between 100 and 350 km relying on vehicles including a self-sustaining ion engine to counteract atmospheric drag to maintain near-constant orbit dynamics. The system operates at altitudes that are substantially lower than traditional satellites, reducing size, weight and cost of the vehicles and their constituent subsystems such as optical imagers, radars, and radio links. The system can include a large number of lower cost, mass, and altitude vehicles, enabling revisit times substantially shorter than previous satellite systems. The vehicles spend their orbit at low altitude, high atmospheric density conditions that have heretofore been virtually impossible to consider for stable orbits. Short revisit times at low altitudes enable near-real time imaging at high resolution and low cost. At such altitudes, the system has no impact on space junk issues of traditional LEO orbits, and is self-cleaning in that space junk or disabled craft will de-orbit.

Abstract: A satellite system operates at altitudes between 100 and 350 km relying on vehicles including a self-sustaining ion engine to counteract atmospheric drag to maintain near-constant orbit dynamics. The system operates at altitudes that are substantially lower than traditional satellites, reducing size, weight and cost of the vehicles and their constituent subsystems such as optical imagers, radars, and radio links. The system can include a large number of lower cost, mass, and altitude vehicles, enabling revisit times substantially shorter than previous satellite systems. The vehicles spend their orbit at low altitude, high atmospheric density conditions that have heretofore been virtually impossible to consider for stable orbits. Short revisit times at low altitudes enable near-real time imaging at high resolution and low cost. At such altitudes, the system has no impact on space junk issues of traditional LEO orbits, and is self-cleaning in that space junk or disabled craft will de-orbit.

Abstract: A power detection system is disclosed that determines a power level of a transmission signal. The power detection system includes an adjustable comparator circuit, an algorithmic state machine, and an output node. The adjustable comparator circuit receives the transmission signal and provides an adjusted transmission signal, and further compares the adjusted transmission signal to a reference signal. The algorithmic state machine iteratively adjusts the adjustable comparator circuit until the adjusted transmission signal is substantially close to the reference signal. The output node is coupled to the algorithmic state machine and provides an output signal that is responsive to the power level of the transmission signal and to the reference signal.

Abstract: The present invention describes a voltage controlled attenuator (VCA) to control an output power level of a radio frequency (RF) signal and to direct the RF signal to an appropriate path for a multi-mode and multi-band radiotelephone without using an external switch and without using multiple common VCAs. The present invention comprises a single differential amplifier and a plurality of steering blocks with each of steering blocks having a path dedicated to a specific RF band and a specific RF mode, having a pair of steering lines to control the RF signal level by having a differential voltage applied, and being capable of being disabled by having its steering lines grounded.

Abstract: A near-unity divider apparatus in a direct conversion communication device includes a reference frequency, that is not on-channel, input to a multiply-by-two circuit that doubles the reference frequency. A divide-by-three circuit divides the doubled frequency by three to provide a first fractionally-divided frequency at a transmit or receive frequency. A delay generator inputs the first fractionally-divided frequency from the divide-by-three circuit and provides a second fractionally-divided frequency delayed a predetermined time period. A gate circuit combines the first and second fractionally-divided frequencies to provide a transmit or receive frequency with an adjustable duty cycle dependant upon the predetermined time period.

Abstract: The present invention describes an apparatus capable of producing a radio frequency (RF) transmit (Tx) signal for a radiotelephone low enough in noise without requiring a post power amplifier (PA) cleanup filter.

Abstract: The present invention describes a voltage controlled attenuator (VCA) to control an output power level of a radio frequency (RF) signal and to direct the RF signal to an appropriate path for a multi-mode and multi-band radiotelephone without using an external switch and without using multiple common VCAs. The present invention comprises a single differential amplifier and a plurality of steering blocks with each of steering blocks having a path dedicated to a specific RF band and a specific RF mode, having a pair of steering lines to control the RF signal level by having a differential voltage applied, and being capable of being disabled by having its steering lines grounded.

Abstract: A low noise direct conversion transmitter architecture without a post-PA filter is described. A high power/low noise differential LO (110), controlled by a near unity divide ratio PLL (112) for re-modulation protection, is coupled a polyphase quadrature generator (120) generating amplitude-balanced and phase-shifted limited differential LO signals. The quadrature mixers (130 and 132) receive the limited differential LO signals and the filtered differential baseband signals to produce up-converted differential signals. The combiner (168) receives the up-converted differential signals and combines them to produce a differential RF transmission signal. A VCA (174) amplifies the differential RF transmission signal, and the resulting differential signal is converted to a single-ended RF transmission signal through a balun (180). A linear amplifier (184) is coupled to the single-ended RF transmission signal for amplification before radio transmission by an antenna (188).

Abstract: A variable gain element for adjusting a magnitude of an input signal. The variable gain element includes a first differential transistor pair having a first transistor coupled to a second transistor. A second differential transistor pair couples the second transistor to a supply voltage and to an output terminal of the first transistor. A load resistor couples the output terminal to the supply voltage. A control voltage applied to an input of the second differential pair causes a varying amount of current cancellation through the load resistor.