Radio Receiver for Carrier Aggregation

A method of operating a radio receiver circuit for a cellular communication system, wherein the radio receiver circuit comprises:

• a first direct conversion receiver arranged to be operatively connected to an antenna and comprising a quadrature mixer arranged to be driven by a first local oscillator (LO) signal, a filter unit connected to an output port of the quadrature mixer, and an analog-to-digital converter (ADC) unit connected to an output port of the filter unit;
• a second direct conversion receiver arranged to be operatively connected to the same antenna and comprising a quadrature mixer arranged to be driven by a second LO signal, a filter unit connected to an output port of the quadrature mixer, and an ADC unit connected to an output port of the filter unit;
• and
• a digital signal processor configured to process output signals from the ADC unit of the first direct conversion receiver and the ADC unit of the second direct conversion receiver;
• wherein the method comprises:
• controlling, in a first mode of operation, the first and second LO signals to have different frequencies, whereby the first direct conversion receiver and the second direct conversion receiver are operable to receive different radio frequency carriers;
• and
• controlling, in a second mode of operation, the first and second LO signals have the same frequency, whereby the first direct conversion receiver and the second direct conversion receiver are operable to receive the same radio frequency carrier.