I/Q Modulator and Demodulator with Wide Instantaneous Bandwidth and High Local-Oscillator-Port-to-Radio-Frequency-Port Isolation

摘要

An improved quadrature modulator/demodulator (IQMD) may use two-phase quadrature local oscillator (LO) signal generation for generating 0° and 90° LO signals, and an anti-phase combiner/divider (at 0° and 180°) on the RF (radio frequency) port. The IQMD may include mixers (which may be double-balanced passive mixers) that function as downconverters when a signal is incident at their radio frequency (RF) ports, and function as upconverters when signals are incident on their intermediate frequency (IF) ports. Accordingly, the IQMD may function as an I/Q modulator by connecting digital-to-analog converters (DAC) to the differential I and Q ports, and/or it may also function as an I/Q demodulator by connecting analog-to-digital converters (ADC) to the differential I and Q ports.

主权项

1. A modulator/demodulator comprising:
an RF port; a first circuit comprising a first port coupled to the RF port, and further comprising a second port and a third port, wherein the first circuit is configured to:
generate a pair of out-of-phase input signals at the second port and third port, responsive to the first port being excited by a first signal received at the RF port; andgenerate a summed output signal at the first port, responsive to the second port and the third port being excited by a pair of out-of-phase output signals; a first mixer coupled to the second port, and configured to:
downconvert a first out-of-phase input signal of the pair of out-of-phase input signals to a first pair of incoming baseband signals; andupconvert a first pair of outgoing baseband signals to a first out-of-phase output signal of the pair of out-of-phase output signals; and a second mixer coupled to the third port, and configured to:
downconvert a second out-of-phase input signal of the pair of out-of-phase input signals to a second pair of incoming baseband signals; andupconvert a second pair of outgoing baseband signals to a second out-of-phase output signal of the pair of out-of-phase output signals.