Abstract: An improved calibration system for a receiver is configured to calibrate the I and Q paths to correct for gain mismatch and quadrature phase errors. In a preferred embodiment, the calibration system calibrates the I and Q paths by using a calibration signal and a reference signal coherently generated from the same single frequency source. The calibration signal is input into the receiver and propagated along the I and Q paths of the receiver simultaneously with a received signal. The reference signal coherently extracts the calibration signal from the I and Q paths. The resulting calibration signals include a component at zero frequency that can be used to measure the phase and gain error. The calibration system is configured to adaptively calibrate the gain and phase error by iteratively measuring the gain and phase error and reducing it to the desired level or eliminating it altogether.

Abstract: An improved calibration system for a receiver is configured to calibrate the I and Q paths to correct for gain mismatch and quadrature phase errors. In a preferred embodiment, the calibration system calibrates the I and Q paths by using a calibration signal and a reference signal coherently generated from the same single frequency source. The calibration signal is input into the receiver and propagated along the I and Q paths of the receiver simultaneously with a received signal. The reference signal coherently extracts the calibration signal from the I and Q paths. The resulting calibration signals include a component at zero frequency that can be used to measure the phase and gain error. The calibration system is configured to adaptively calibrate the gain and phase error by iteratively measuring the gain and phase error and reducing it to the desired level or eliminating it altogether.

Abstract: A digital error corrected Fractional-N synthesizer having a reference frequency generator for providing a reference frequency signal and a voltage controlled oscillator for providing an output signal having a frequency equal to a fractional multiple of said reference frequency signal. The output signal of the Fractional-N synthesizer includes a residual error signal. An error signal compensation circuit is provided for generating a correction signal to cancel the residual error signal. In a preferred embodiment, the reference frequency signal is delivered to a loop phase detector which provides an error voltage proportional to a phase difference between the reference frequency signal and a feedback signal. The frequency of the output signal, which is a fractional multiple of the reference frequency signal and proportional to the error voltage, is operated upon by a plurality of divisors of a loop divider circuit to provide the feedback signal.

Abstract: An automatic gain control (AGC) circuit for microwave applications is disclosed. The AGC circuit includes a power divider for splitting the signal to be controlled into two signal paths. In one signal path the signal is passed through a GaAs monolithic attenuator. In the other signal path, an RF detector provides a detector output signal to a shaper circuit, which responds to the detector signal to provide control signals to the attenuator. Thus, the AGC circuit employs a feed forward technique for gain control, to provide fast settling times for the circuit.