Telefonaktiebolaget Lm Ericsson (Publ)

Thorsten Schier

Svante Signell

A down-converter converts an amplitude modulated high frequency signal into a low frequency or baseband signal. A first mixer ( ) mixes the high frequency signal into a composite signal having an in-phase component and a quadrature component. A complex bandpass filter ( ) bandwidth limits the composite signal into a bandwidth limited signal with an in-phase component and a quadrature component. A second mixer ( ) mixes the bandwidth limited signal into an intermediate signal with an in-phase component and a quadrature component, and an adder ( ) adds one component of the intermediate signal to the other. A similar up-converter performs the reverse process.

Down/up-conversion apparatus and method

A base station in a radio telecommunication system, transforms real digital wideband high-frequency signals into a set of complex digital baseband signals and vice versa. The base station receives a set of complex digital baseband signals having an &ldquo;I&rdquo; and a &ldquo;Q&rdquo; components. A portion of these signals are modulated and then converted into complex digital high-frequency signals. The complex digital high-frequency signals are then filtered via bilinear digital ladder bandpass filters to retrieve real digital narrowband high-frequency signals. The outputs of these filters are the same corresponding &ldquo;I&rdquo; and &ldquo;Q&rdquo; components at the narrowband frequencies. These signals are further combined to form real digital wideband high-frequency signals. Finally, the combined signals are converted through a D/A converter to real analog wideband high-frequency bandpass signals.

Signal transformation method and apparatus

A base station in a radio communication system uses complex bandpass filters &OHgr;,, &OHgr;,, . . . ,&OHgr;,and down-sampling to channelize a wideband signal containing many channels or channel groups.

A desired programmable complex analog bandpass filter is replaced by a 'black box' that receives an analog continuous-time signal and delivers an analog continuous-time signal, just as the analog filter would, but internally realizes the programmability with a programmable discrete-time system. The transfer function of the 'black box' is the same as the transfer function of the analog filter. The 'black box' includes an anti-aliasing filter, an A/D-converter, a complex digital bandpass filter (16), a D/A-converter (18) and an anti-imaging filter (20).

Growing community of inventors

Sundbyberg, Sweden

Thorsten Schier