COMPLEX EXAMPLE: WLAN RECEIVER
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9.4
Example Calibration
At this point of the design flow the initial specification of the receiver is
subdivided into basic building blocks. The respective behavioral models in
VHDL-AMS are basically developed from theory based on the system
specification. Further refinement is necessary in order to improve the
behavioral models in the way of accuracy and to fit them to circuit level
models.
In this section an algebraic equation is fitted to a chosen characteristic
that is extracted from a circuit level model. The equation can be used to
describe the behavioral model. This step introduces an abstraction to reduce
the simulation effort of the behavioral model compared to the circuit level
model. Simulation effort is determined by the simulation time and the
computational power that is required to execute the model. Furthermore the
behavioral model should not strongly deviate from the extracted
characteristic.
In the WLAN receiver model three amplifiers are specified, one low-
noise amplifier at the input and two baseband amplifiers (I- and Q-channel)
at the output of the receiver. The circuit level model lnaSimple is chosen
from the Cadence library. This model is assumed to be the circuit level
model of the baseband amplifiers. As an example characteristic the operating
voltage dependency of the power gain is chosen. The nominal operating
voltage of lnaSimple is 15 V. The input frequency is set to 1 MHz because
the input signal of the baseband amplifier is a downconverted OFDM signal.
The circuit level model lnaSimple is simulated using SpectreRF. The
power gain is plotted versus the operating voltage in a range from 0 V to
20 V. Figure 9-6 shows the simulation results.
Figure 9-6. Power gain versus operating voltage of lnaSimple
Summary :
Further refinement is necessary in order to improve the behavioral models in the way of accuracy and to fit them to circuit level models. This step introduces an abstraction to reduce the simulation effort of the behavioral model compared to the circuit level model. This model is assumed to be the circuit level model of the baseband amplifiers.
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circuit,leel,behaioral,operating,lnasimple,power,oltage,simulation,receier,example,input,chosen,amplifiers