Conversion Circuit For Converting Complex Analog Signal Into Digital Representation

摘要

A conversion circuit for converting a complex analog input signal having an in-phase (I) component and a quadrature-phase (Q) component is disclosed. It comprises a channel-selection filter configured to filter the complex analog input signal, thereby generating a channel-filtered I and Q components, and one or more processing circuits. Each processing circuit comprises four mixers for generating a first and a second frequency-translated I component, and a first and a second channel-filtered Q component based on two LO signals with equal LO frequency and a 90° mutual phase shift. Each processing circuit also comprises a combiner circuit for generating a first, a second, a third, and a fourth combined signal proportional to sums and differences between the frequency translated I and Q components. The first and the fourth combined signals form a first complex signal, and the second and the third combined signals form a second complex signal.

主权项

1. A conversion circuit for converting a complex analog input signal having an in-phase (I) component and a quadrature-phase (Q) component resulting from frequency down conversion of a radio frequency (RF) signal to a frequency band covering 0 Hz into a digital representation, the conversion circuit comprising:
a channel selection filter configured to filter the complex analog input signal, thereby generating a channel-filtered I component and a channel-filtered Q component, wherein the channel selection filter unit has a passband that covers 0 Hz; and one or more processing circuits, each comprising:
a first mixer configured to mix the channel-filtered I component with a first local-oscillator (LO) signal to generate a first frequency-translated I component;a second mixer configured to mix the channel-filtered I component with a second LO signal to generate a second frequency-translated I component;a third mixer configured to mix the channel-filtered Q component with the first LO signal to generate a first frequency-translated Q component;a fourth mixer configured to mix the channel-filtered Q component with the second LO signal to generate a second frequency-translated Q component;a combiner circuit configured to generate:
a first combined signal proportional to a sum of the first frequency translated I component and the second frequency-translated Q component;a second combined signal proportional to a difference between the first frequency translated I component and the second frequency-translated Q component;a third combined signal proportional to a sum of the second frequency-translated I component and the first frequency-translated Q-component; anda fourth combined signal proportional to a difference between the first frequency-translated Q component and the second frequency-translated I component;wherein the first and the fourth combined signals form a first complex signal; andwherein the second and the third combined signals form a second complex signal; anda first analog-to-digital converter (ADC), a second ADC, a third ADC, and a fourth ADC configured to provide digital representations of the first complex signal and the second complex signal for forming the digital representation of the analog complex input signal;wherein the first and the second LO signal of a given processing circuit have a common LO frequency associated with the processing circuit and a mutual 90° phase shift; andwherein the RF signal is a cellular communication signal.