This invention relates to apparatus and methods for radio receivers, in
particular low (IF) frequency receivers. Embodiments of the invention are
particularly suitable for digital audio broadcast receivers. A low-IF
radio receiver circuit, the circuit comprising: an rf input for a
received rf signal; a first local oscillator having a quadrature output
to provide a quadrature first local oscillator signal at a first
frequency; a quadrature first mixer coupled to said rf input and to said
quadrature-output of said first local-oscillator and having a quadrature
first mixer output, and said first mixer and said first local oscillator
being configured to provide quadrature mixing of said quadrature first
local oscillator signal and said received rf signal to downconvert said
received rf signal to a first quadrature IF Signal at a first IF
frequency; a bandpass filter coupled to said quadrature first mixer
output and having a filtered output to provide a bandpass filtered first
IF signal; a second local oscillator having a second local oscillator
output to provide a second local oscillator signal at a second frequency;
a second mixer coupled to said filtered output of said bandpass filter
and to said second local oscillator and having a second mixer output,
said second mixer and said second local oscillator being configured to
provide mixing of said second local oscillator signal and said bandpass
filtered first IF signal to up-convert said bandpass filtered first IF
signal to a second IF signal at a second IF frequency, wherein said
second IF frequency is greater than said first IF frequency; and an
output coupled to said second mixer output to provide an output signal
from said second IF signal.