Patent ID: 7750749

Claim:
A switching circuit operable to reduce phase noise in an output of the switching circuit comprising: first, second, third and fourth steering switches operable to make or break a path between first and second terminals thereof, and each steering switch further having a control terminal for controlling the switch, the first, second, third and fourth steering switches having their control terminals driven by first, second, third and fourth switching signals, respectively, provided by a frequency divider, the first, second, third and fourth switching signals having a first frequency and the second switching signal being in anti-phase with the first switching signal and the third switching signal being in anti-phase with the fourth switching signal, the first steering switch having at most one of its first, second and control terminals connected directly to a corresponding terminal of the second steering switch; and first and second chopping switches operable to make or break a path between first and second terminals thereof and each having a control terminal, the first chopping switch being connected in series with the first and second steering switches at a first common node, the first chopping switch receiving at its first terminal a baseband signal to be modulated and up-converted by the switching circuit and receiving at its control terminal a first switching control signal, and the second chopping switch is connected in series with the third and fourth steering switches at a second common node, the second chopping switch receiving at its control terminal a second switching control signal and the first and second chopping switches are connected at a third common node wherein, in a phase noise reducing mode, the control terminal of the first chopping switch is driven by the first switching control signal which has a frequency that is a multiple of the first frequency, the first switching control signal and the first switching signal having a relative phase relationship such that the first chopping switch is always non-conducting while the first and second steering switches are changing between being conducting and being non-conducting, and the second chopping switch is driven by the second switching control signal in anti-phase with the first switching control signal, the second switching control signal and the third switching signal having a relative phase relationship such that the second chopping switch is always non-conducting while the third and fourth steering switches are changing between being conducting and being non-conducting.