Calibration techniques for sigma delta transceivers

A transceiver front-end circuit for a cellular radio, said transceiver circuit comprising:

• an antenna operable to transmit signals and receive signals;
• a switch module including a switching network that directs analog transmit signals to be transmitted to the antenna and receives receive signals from the antenna, said switch module further including a multiplexer module coupled to the switching network and including a plurality of signal paths, where each signal path includes a bandpass filter that passes a different frequency band than the other bandpass filters and a circulator that provides signal isolation between the transmit signals and the receive signals;
• a receiver module including a separate signal channel for each of the signal paths in the multiplexer module, each signal channel in the receiver module including a receiver delta-sigma modulator that converts analog receive signals to representative digital signals;
• a transmitter module including a transmitter delta-sigma modulator for converting digital signals to the transmit signals, said transmitter module including a tunable bandpass filter and a power amplifier for amplifying the transmit signals before transmitting;
• and
• a compensation module that provides timing, phase, frequency and bias setting signals to the receiver module and the transmitter module.

A transceiver front-end circuit for a cellular radio, said transceiver circuit comprising:

• an antenna operable to transmit signals and receive signals;
• a switch module including a switching network that directs analog transmit signals to be transmitted to the antenna and receives receive signals from the antenna, said switch module further including a multiplexer module coupled to the switching network and including a plurality of signal paths, where each signal path includes a bandpass filter that passes a different frequency band than the other bandpass filters and a circulator that provides signal isolation between the transmit signals and the receive signals;
• a receiver module including a separate signal channel for each of the signal paths in the multiplexer module, each signal channel in the receiver module including a receiver delta-sigma modulator that converts analog receive signals to representative digital signals;
• and
• a transmitter module including a transmitter delta-sigma modulator for converting digital signals to the transmit signals, said transmitter module including a tunable bandpass filter and a power amplifier for amplifying the transmit signals before transmitting, wherein the switching network directs the transmit signals from the power amplifier to the receiver module to provide transmit signal calibration, said switch module further including a variable low/attenuator module for attenuating the transmit signals before being sent to the receiver module, wherein the switching network includes a second switch that selectively directs the transmit signals to the antenna or the variable low/attenuator module and a third switch that selectively directs the attenuated transmit signals from the variable low/attenuator module to the receiver module or the transmit signals from the multiplexer module to the receiver module.