Patent ID: 8571133

Claim:
A transmitting apparatus for transmitting a signal within a predetermined spectral mask defining a range of power density limits across a frequency range, the apparatus comprising: a first signal source for providing a first input signal; a second signal source for providing a second input signal; a filter coupled to the first signal source for low-pass filtering the first input signal to produce a first filtered signal and coupled to the second signal source for low-pass filtering the second input signal to produce a second filtered signal, the filter being selectively operable in a first mode in which an input signal is filtered within a narrower bandwidth and in a second mode in which an input signal is filtered within a broader bandwidth, wherein the first signal is filtered according to the first mode and the second signal is filtered according to the second mode; a modulator coupled to the filter for modulating the first filtered signal to produce a first modulated signal and the second filtered signal to produce a second modulated signal; a transmitter, coupled to the modulator, for transmitting the first modulated signal at a required power level as a transmitted signal having a spectral envelope and for transmitting the second modulated signal, wherein the first modulated signal and the second modulated signal are transmitted substantially simultaneously; and a controller for controlling operation of the filter depending on the required power level such that the first input signal is so filtered in the first mode, when the required power level is higher, that the spectral envelope of the transmitted signal is within the spectral mask, and is so filtered in the second mode, when the required power level is lower, that the spectral envelope of the transmitted signal remains within the spectral mask.