Abstract: An amplification circuit (10) is used in a radio receiver (12) to achieve both constant phase shift over the gain range and low intermodulation. A gain-controlled amplifier (16) is desirably optimized for good fidelity, even if at the expense of poor phase linearity. A phase shift compensator (48) compensates for phase non-linearity by imposing a delay of variable duration downstream of the gain-controlled amplifier (16). The delay duration is determined in response to a gain-control signal (20) generated by an AGC circuit (42). The gain-control signal (20) is translated through a look-up table (62) into delay values which control a programmable delay element (64). The programmable delay element (64) generates an adjusted clock signal (54) that drives a digitizer (36). The digitizer (36) both digitizes and delays an amplified signal (32) produced by gain-controlled amplifier (16).

Abstract: An amplification circuit (10) is used in a radio receiver (12) to achieve both constant phase shift over the gain range and low intermodulation. A gain-controlled amplifier (16) is desirably optimized for good fidelity, even if at the expense of poor phase linearity. A phase shift compensator (48) compensates for phase non-linearity by imposing a delay of variable duration downstream of the gain-controlled amplifier (16). The delay duration is determined in response to a gain-control signal (20) generated by an AGC circuit (42). The gain-control signal (20) is translated through a look-up table (62) into delay values which control a programmable delay element (64). The programmable delay element (64) generates an adjusted clock signal (54) that drives a digitizer (36). The digitizer (36) both digitizes and delays an amplified signal (32) produced by gain-controlled amplifier (16).

Abstract: Additional resources and services are provided in a satellite communication system (100) through the use of seam satellites (52). One or more seam satellites (52) are coupled to communication satellites (12) in an existing constellation using previously unused crosslinks. The seam satellites (52) are located between orbital planes (31 and 36) in which the communication satellites (12) are moving in opposite directions with respect to each other. Seam satellites (52) can provide new services such as earth sensing and observation. Seam satellites (52) can also provide attachment points for other new space-based users. Some of the communication units (26) can communicate with the seam satellites (52) via communication satellites (12). This allows these communication units (26) to use the new services provided by the seam satellite (52). Seam satellites (52) can be controlled by separate control centers or can be controlled by the control center for the communication satellites (12).