ANALOG BEHAVIORAL MODELING WITH THE VERILOG-A LANGUAGE- P6: Verilog-A is a new hardware design language (HDL) for analog circuit and systems design. Since the mid-eighties, Verilog HDL has been used extensively in the design and verification of digital systems. However, there have been no analogous high-level languages available for analog and mixed-signal circuits and systems. | Voltage Regulator 180 degrees Celsius is shown in Figure . The bow in the voltage with respect to temperature is a typical characteristic for bandgap based voltage reference. FIGURE Bandgap reference voltage a and total current b over temperature for the behavioral model. Figure shows the output voltage and the cell current as the supply voltage is varied over the expected range of usage from 4 to 6 volts. 135 Please purchase PDF Split-Merge on to remove this watermark Figure testing the dynamic response of models verifies the output voltage as a function of the switch current between the reference and the buffer amplifier. figure Voltage regulator control signal a and output voltage b 136 Verilog-A HDL Please purchase PDF Split-Merge on to remove this watermark QPSK Modulator Demodulator QPSK Modulator Demodulator Quadrature phase-shift keying or QPSK is an example of a modulation technique in which the information carried within the signal is contained in the phase. The phase of the signal can take on one of four values such as shown in the constellation diagram of Figure . figure QPSK modulator constellation diagram showing the allowable states between the in-phase and quadrature components. Modulator As shown in the QPSK modulator schematic Figure the incoming binary sequence is transformed into polar form by a nonreturn-to-zero NRZ encoder. Here the binary 1 and 0 symbols are transformed into 1 and -1 respectively. The NRZ data stream is de-multiplexed into two separate binary sequences consisting of the odd-and even-numbered input bits. These binary sequences are used to modulate a pair of quadrature carriers which are added together to produce the QPSK signal. The QPSK modulator module consists of two primary components for the polarization of the input data sequence and the modulation of the quadrature components to produce the QPSK signal. The modulator samples the input data .
