UWB TRANSMIT ANTENNA

UWB_TRANSMIT_ANTENNA

The transmit filter component represents frequency-dependent effects in the pulser, antenna, and environment.

The UWB_TRANSMIT_ANTENNA subnetwork consists of an SBlock component that reads a file of S-parameters representing the RF front-end and antenna of the transmit pulser. The S-parameters can be measured using a network analyzer. In the default setup, they are created by conducting RF simulations of a series of filters.

HighPassFilter_RFsim.dsn (HighPassFilter_RFSim.dsn Schematic ) is used to generate the default S-parameter file. After reading S-parameters from the file, the SBlock component produces the equivalent impulse response for use in ADS Ptolemy simulations. To produce a practical impulse response, a high-frequency cutoff lowpass filter must be applied when the S-parameters for a highpass filter are generated.

The SBlock component determines transmit filter characteristics by reading S-parameters from a file. S-parameter files can be generated using templates provided in the DesignGuide > UWB > Frequency Dependent Models menu. These designs use the ADS RF simulator (S_Param) to generate S21 for a series combination of lowpass and highpass filters. The default combination of filters provides a representation of the response of a transmit chain and antenna so the transmitter can meet FCC indoor spectral mask regulations. The Test Impulse Response for use with SBlock template ( HighPassFilter_SBlockTest.dsn, HighPassFilter_SBlockTest.dsn Schematic) provides an ADS Ptolemy simulation for testing the impulse response using filter S-parameters.

Note
The SBlock N value must be large enough for the filter impulse response to adequately decay. The impulse response will be truncated after a time of N×TStep. Using the lowest acceptable value of N will speed simulation.

If a highpass filter is used in the RF simulator, a lowpass filter must be included to limit the high-frequency response; otherwise, the SBlock component cannot generate a practically solvable impulse response from the resulting set of S-parameters. S-parameters of the user's circuits can be included in the simulation using the SBlock component.

S-parameters measured using a network analyzer can be used in the input file for the filter. Refer to SBlock component Help for input file format information.