An apparatus for generating a signal at a carrier frequency, comprising: a first digital-to-analog converter, DAC, (11 I ) adapted to receive a sequence of first digital signals at a sub-carrier frequency and to convert said sequence of first digital signals into a corresponding first sequence of first analog voltage values; a second DAC, (11 Q ) adapted to receive a sequence of second digital signals at said sub-carrier frequency and to convert said sequence of second digital signals into a corresponding second sequence of second analog voltage values; an analog electronic combiner ; said apparatus being characterized by : a first electronic switch (10 I ) configured to connect an output of the first DAC (11 I ) to a first input of the combiner , and to be operated by a first periodic signal at said carrier frequency so as to sequentially deliver the first analog voltage values of said first sequence to the combiner; a second electronic switch (10 Q ) configured to connect an output of the second DAC (11 Q ) to a second input of the combiner , and to be operated by a second periodic signal at said carrier frequency so as to sequentially deliver the second analog voltage values of said second sequence to the combiner; and wherein the analog electronic combiner is configured to combine signals output by the first and second electronic switches (10 I , 10 Q ) to produce a quadrature modulated signal at the carrier frequency. a first digital-to-analog converter, DAC, (11 I ) adapted to receive a sequence of first digital signals at a sub-carrier frequency and to convert said sequence of first digital signals into a corresponding first sequence of first analog voltage values; a second DAC, (11 Q ) adapted to receive a sequence of second digital signals at said sub-carrier frequency and to convert said sequence of second digital signals into a corresponding second sequence of second analog voltage values; an analog electronic combiner ; said apparatus being characterized by : a first electronic switch (10 I ) configured to connect an output of the first DAC (11 I ) to a first input of the combiner , and to be operated by a first periodic signal at said carrier frequency so as to sequentially deliver the first analog voltage values of said first sequence to the combiner; a second electronic switch (10 Q ) configured to connect an output of the second DAC (11 Q ) to a second input of the combiner , and to be operated by a second periodic signal at said carrier frequency so as to sequentially deliver the second analog voltage values of said second sequence to the combiner; and wherein the analog electronic combiner is configured to combine signals output by the first and second electronic switches (10 I , 10 Q ) to produce a quadrature modulated signal at the carrier frequency. a first electronic switch (10 I ) configured to connect an output of the first DAC (11 I ) to a first input of the combiner , and to be operated by a first periodic signal at said carrier frequency so as to sequentially deliver the first analog voltage values of said first sequence to the combiner; a second electronic switch (10 Q ) configured to connect an output of the second DAC (11 Q ) to a second input of the combiner , and to be operated by a second periodic signal at said carrier frequency so as to sequentially deliver the second analog voltage values of said second sequence to the combiner; and wherein the analog electronic combiner is configured to combine signals output by the first and second electronic switches (10 I , 10 Q ) to produce a quadrature modulated signal at the carrier frequency. <EOS>