Multiband frequency generation using a single PLL-circuit

A sending/receiving unit for a mobile radio unit with multiband operation, comprising:

• at least one receiving branch for each receiving frequency band with a mixer stage, whereto a first local oscillator signal is supplied in a suitable manner,
• at least one transmitting branch for each transmitting frequency band in which an intermediate frequency modulated sending signal is converted into a sending frequency band, wherein
• the conversion into said sending frequency band is achieved through a phase comparison of an intermediate frequency modulated sending signal with a sending signal re-converted into an intermediate frequency band and through control of a voltage-controlled oscillator in accordance with a phase difference, and
• a multiband frequency generator adapted to generate the local oscillator signals, the multiband frequency generator comprising:
• a voltage-controlled multiband oscillator adapted to generate a local oscillator signal at one output terminal for each local oscillator signal,
• a frequency synthesis unit adapted to derive a phase difference between a control input signal for a frequency and said generated local oscillator signal,
• at least one control unit for said voltage-controlled multiband oscillator using said phase difference generated through said frequency synthesis unit as correcting variable,
• wherein each output terminal of said multiband oscillator is coupled to said frequency synthesis unit via a frequency selective filterbank adapted to achieve a decoupling of said different multiband oscillator output signals through a frequency selective behaviour of filters before feedback to said frequency synthesis unit, and
• wherein the filterbank comprises at least one filter selected from a group consisting of a low pass filter, a bandpass filter, and a high pass filter.

A method of operating a multiband frequency generator to generate an output signal in at least two frequency bands, comprising the steps of:

• outputting the output signal via one output of a voltage-controlled multiband oscillator for each frequency band,
• deriving a phase difference between a frequency control input signal and the generated output signal in a frequency synthesis unit,
• controlling the voltage-controlled multiband oscillator using said phase difference as correcting variable,
• coupling the output signal at said output terminal of said voltage-controlled multiband oscillator via a frequency selective filterbank adapted to achieve a decoupling of the different multiband output signals through a frequency selective behaviour of filters before feedback to said frequency synthesis unit, and
• wherein the filterbank comprises at least one filter selected from a group consisting of a low pass filter, a bandpass filter, and a high pass filter.