RF Design Environment ExamplesRFIC BJT IQ Modulator

RFIC BJT Amplifier

Location: $HPEESOF_DIR/examples_rfde/RFIC_BJT_Amp/

Objective

This example shows various simulations of a differential-mode amplifier. The amplifier consists of two emitter-coupled pair stages followed by two emitter-follower stages. There are saved data display files that correspond to each of the simulation (top-level) cellviews described below.

Setup

  1. OutputStgTest simulates the power delivered to a load resistor by the output stage, as a function of the load resistance.
  2. Amp_DC_Swp simulates the amplifier's DC transfer curve.
  3. Amp_AC_Test simulates the amplifier's common- and differential-mode gains, as well as the common-mode rejection ratio.
  4. Amp_HB_LogSwp simulates the amplifier's gain, output power, and harmonic distortion, with a single, differential-mode input tone, whose amplitude is swept logarithmically as a dB value.
  5. Amp_IMD_LogSwp is a two-tone, intermodulation distortion simulation of the amplifier, versus input signal amplitudes.
  6. Amp_wIS95RevLinkSrc simulates the amplifier with an IS95 reverse link signal source. The simulation results include the output spectrum, ACPR, trajectory diagram, output power versus time, peak-to-average power ratio, and the complementary cumulative distribution function.

Schematic from Amp_IMD_LogSwp cellview

Analysis

Notes

  • The "Spectrum" equation gives the differential-mode output voltage in dB.
  • The "tones" equation defines which spectral tones will be selected for the "Spectrum_zoomed" equation. So in this example, mixing tones at 3X the first fundamental - 2X the second fundamental, at 2X the first fundamental - 1X the second fundamental, at 1X the first fundamental, etc. will be selected. The first fundamental is at Freq_In-Fspacing/2 and the second fundamental is at Freq_In+Fspacing/2, where Freq_In and Fspacing are design variables.
  • The third-order intercept (TOI) calculations are based on simple extrapolations of the fundamental and third-order spectral tones when the input signal amplitudes are at their lowest simulated value. The [0] index selects the first (and in this case lowest) simulated value. If the first input signal amplitude is already high enough to drive the amplifier into compression, then these TOI calculations will be inaccurate.
  • Each of the two voltage gains are computed as the output signal amplitude (dBV) of one of the desired output tones minus the amplitude of one of the two input signals (dBV).
  • The marker m1 used in this data display enables you to run a swept simulation, save all the data, and then quickly change what "slice" of the data you are displaying.