Analog/digital converter and milimeter wave radar system

A MASH (Multi stAge Noise SHaping) type and sigma-delta type analog/digital converter comprising:

• a first modulator to which an external input signal as an analog signal is input, and which includes a first quantizer;
• a second modulator which is coupled to a latter stage of the first modulator and includes a second quantizer;
• a probe signal generation circuit which generates a first probe signal and injects the first probe signal to the first modulator;
• a first adaptive filter which searches for a transfer function of the first modulator by observing an output signal of the first quantizer in accordance with the first probe signal;
• a second adaptive filter which searches for a transfer function of the second modulator by observing an output signal of the second quantizer;
• and p1 a noise cancel circuit which cancels an quantization error generated by the first quantizer using a search result of the first adaptive filter and a search result of the second adaptive filter,
• wherein the first modulator includes
• a first analog integrator which includes an analog circuit,
• the first quantizer which quantizes an output signal of the first analog integrator,
• a first digital/analog converter circuit which converts an output signal of the first quantizer into an analog signal, and
• a first analog adder/subtracter which outputs a differential signal between the external input signal and an output signal of the first digital/analog converter circuit.

A millimeter wave radar system comprising:

• a high frequency unit which transmits a transmission wave to an object, and generates a plurality of beat signals by down-converting a reflected wave from the object which is received by a plurality of antennas, using the transmission wave;
• a low-pass filter to which the beat signals are input;
• and
• a baseband unit which processes the beat signals from the low-pass filter,
• wherein the baseband unit includes a plurality of MASH (Multi stAge Noise SHaping) type and sigma-delta type analog/digital converters each of which converts each of the beat signals from the low-pass filter into a digital signal,
• wherein each of the analog/digital converters includes
• a first modulator which includes a first analog integrator including an analog circuit and a first quantizer quantizing an output signal of the first analog integrator, and to which a corresponding beat signal of the beat signals is input,
• a second modulator which is coupled to a latter stage of the first modulator, and includes a second analog integrator including an analog circuit and a second quantizer quantizing an output signal of the second analog integrator,
• a probe signal generation circuit which injects a probe signal to the first modulator,
• a first adaptive filter which searches for a transfer function of the first modulator by observing an output signal of the first quantizer in accordance with the probe signal,
• a second adaptive filter which searches for a transfer function of the second modulator by observing an output signal of the second quantizer in accordance with the probe signal, and
• a noise cancel circuit which cancels a quantization error generated by the first quantizer using a search result of the first adaptive filter and a search result of the second adaptive filter.