An improved receiver system may include an input to receive an input signal, and a signal generating circuit to generate a desired oscillator signal that is a single sideband radio frequency signal of time varying frequency. The receiver may also include a downconversion stage to generate an intermediate frequency (IF) signal based on the input signal and the desired oscillator signal. A signal processing block in the receiver may be used to produce an output signal based on the IF signal by frequency shifting the IF signal by an amount that compensates for the time varying frequency of the desired oscillator signal. The desired oscillator signal may be generated using a vector signal generator that receives a control value from the signal processing block, converts the control value to a pair of analog input signals, and generates the desired oscillator signal by quadrature modulating the pair of analog input signals.