Abstract: A switching circuit (100) is provided, comprising: a signal coupler (110) configured to receive first and second input signals and provide first and second coupled signals; a first phase shifter (130) configured to shift a first phase of the first coupled signal by zero degrees or ninety degrees based on a first control signal to generate a first shifted signal; a second phase shifter (135) configured to shift a second phase of the second coupled signal by zero degrees or ninety degrees based on a second control signal to generate a second shifted signal; and a combiner (150) configured to combine the first and second shifted signals. The first coupled signal includes an in-phase copy of the first input signal and a ninety-degree-shifted copy of the second input signal; and the second coupled signal includes an in-phase copy of the second input signal and a ninety-degree-shifted copy of the first input signal.

Abstract: An apparatus for converting a digital input signal to an analog signal for transmission. The input signal can include more than one carrier signal. A plurality of delta-sigma modulation loop circuits are connected in an increasing order of operating frequency so as to reduce a word length of the input signal. A tuning circuit adjusts the signal frequency to a transmitting frequency for conversion to analog by a digital-to-analog converter. A first loop circuit is implemented using CMOS gates, and a second loop circuit and the tuning circuit are implemented using indium phosphide gates. The apparatus allows a high-resolution, wide-band RF multiple-carrier signal to be re-quantized to a lower-resolution signal while an acceptable signal-to-noise ratio is maintained.

Abstract: An apparatus for converting a digital input signal to an analog signal for transmission. The input signal can include more than one carrier signal. A plurality of delta-sigma modulation loop circuits are connected in an increasing order of operating frequency so as to reduce a word length of the input signal. A tuning circuit adjusts the signal frequency to a transmitting frequency for conversion to analog by a digital-to-analog converter. A first loop circuit is implemented using CMOS gates, and a second loop circuit and the tuning circuit are implemented using indium phosphide gates. The apparatus allows a high-resolution, wide-band RF multiple-carrier signal to be re-quantized to a lower-resolution signal while an acceptable signal-to-noise ratio is maintained.