Dynamic adjustment to preserve signal-to-noise ratio in a quadrature detector system

An apparatus for demodulating a frequency modulated signal, the apparatus comprising:

• a quadrature detector circuit which receives the frequency modulated signal and outputs a first signal that indicates the frequency of the frequency modulated signal and also includes an offset;
• an offset adjustment circuit which combines an offset correction with the first signal to compensate for the offset in response to a correction signal and that provides an offset adjusted signal at an output node;
• a control circuit operably connected to the offset adjustment circuit for supplying the correction signal;
• and
• a source of a training signal whose frequency is substantially equal to a reference frequency, and a switch to periodically supply the training signal to the quadrature detector.

In a system for the wireless transfer of frequency modulated information, a transmit/receive station comprising:

• an antenna;
• a transmit/receive switch;
• a transmitter connected to the antenna through the transmit/receive switch, which transmits a frequency modulated signal;
• and
• a receiver connected to the antenna through the transmit/receive switch, for receiving and demodulating a frequency modulated signal wherein the receiver comprises:
• a quadrature detector circuit which receives the frequency modulated signal and outputs a first signal that indicates the frequency of the frequency modulated signal and also includes an offset;
• an offset adjustment circuit which combines an offset correction with the first signal to compensate for the offset in response to a correction signal and that provides an offset adjusted signal at an output node;
• a control circuit operably connected to the offset adjustment circuit for supplying the correction signal;
• and
• a source of a training signal whose frequency is substantially equal to a reference frequency, and a switch to periodically supply the training signal to the quadrature detector.