A pulse generator is provided for generating pulses with a selectable variable width and/or delay. The pulse generator comprises an oscillator (3) and a selecting arrangement for selecting how many of a first group (13) of delay elements are connected in series for delaying the oscillator signal (IF clock). Identical delay elements (26) are connected in series to form a second group, whose input receives the oscillator signal (IF clock). A measuring circuit (27) repeatedly measures the delay provided by the second group, for example providing output pulses (IP) whose width or duration (IPD) is equal to the delay. A reference pulse generator (29,30) generates a series of reference pulses (RP), each of which is of a predetermined duration equal to a fraction of the oscillator signal (IF clock) period. A control circuit, such as a charge pump and integrator (28), compares the measurement pulses (IP) and the reference pulses (RP) to generate an error signal which is fed back to timing delay control inputs of all of the delay elements such that the widths of the measurement and reference pulses (IP,RP) are made substantially equal to each other.