A frequency-agile transmitter tunable to operate in each of a plurality of predetermined frequency bands, comprising: a programmable digital up-converter comprising a complex baseband tuner, a digital up-sampler, a complex channel selection filter and a quadrature modulator, wherein the programmable digital up-converter has a first input configured to receive a pre-distorted baseband signal and a second input configured to receive at least one first control input, wherein the at least one first control input provided to the programmable digital up-converter includes at least one of: filter information associated with a selected one of the predetermined frequency bands, complex tuner frequency and an up-sampling parameter associated with the selected one of the predetermined frequency bands, wherein the programmable digital up-converter is configured to up-convert the pre-distorted baseband signal into a digital signal in a selected one of the predetermined frequency bands according to the received at least one first control input, wherein the pre-distorted baseband signal is generated based on a received digital complex input signal and a first digital feedback signal; a digital to analog converter connected to the programmable digital up-converter, and configured to receive the digital signal and to convert the digital signal to an analog signal; an analog filter connected to the digital to analog converter, and configured to receive the analog signal, and to output a filtered analog signal including substantially only components having frequencies in the selected one of the frequency bands; a power amplifier connected to the analog filter, and configured to receive the filtered analog signal, and to amplify the filtered analog signal; an analog to digital converter configured to receive an analog feedback signal corresponding to the amplified filtered analog signal, to sample the analog feedback signal, and to output a second digital feedback signal; and a programmable digital down-converter connected to the analog to digital converter, and configured to receive the digital feedback signal, to convert the second digital feedback signal to a lower sample rate based on at least one second control input, into the first digital feedback signal. a programmable digital up-converter comprising a complex baseband tuner, a digital up-sampler, a complex channel selection filter and a quadrature modulator, wherein the programmable digital up-converter has a first input configured to receive a pre-distorted baseband signal and a second input configured to receive at least one first control input, wherein the at least one first control input provided to the programmable digital up-converter includes at least one of: filter information associated with a selected one of the predetermined frequency bands, complex tuner frequency and an up-sampling parameter associated with the selected one of the predetermined frequency bands, wherein the programmable digital up-converter is configured to up-convert the pre-distorted baseband signal into a digital signal in a selected one of the predetermined frequency bands according to the received at least one first control input, wherein the pre-distorted baseband signal is generated based on a received digital complex input signal and a first digital feedback signal; a digital to analog converter connected to the programmable digital up-converter, and configured to receive the digital signal and to convert the digital signal to an analog signal; an analog filter connected to the digital to analog converter, and configured to receive the analog signal, and to output a filtered analog signal including substantially only components having frequencies in the selected one of the frequency bands; a power amplifier connected to the analog filter, and configured to receive the filtered analog signal, and to amplify the filtered analog signal; an analog to digital converter configured to receive an analog feedback signal corresponding to the amplified filtered analog signal, to sample the analog feedback signal, and to output a second digital feedback signal; and a programmable digital down-converter connected to the analog to digital converter, and configured to receive the digital feedback signal, to convert the second digital feedback signal to a lower sample rate based on at least one second control input, into the first digital feedback signal.