Wireless Test Bench Basics
Introduction
ADS wireless test benches enable system designers to make wireless system measurements available to RF designers to validate RF designs for use with wireless systems.
Previously, RF designers used traditional Analog/RF measurements such as spectrum, TOI, etc. to validate their designs. Empirical methods used to map Analog/RF measurements to determine wireless system performance were error prone. Typically, they could not perform more complex wireless system measurements successfully such as EVM and BER. And, a system designer using ADS Ptolemy simulator could not easily deliver a system test bench to the RF designer for more accurate and complete RF verification.
Wireless test bench templates available in the Analog/RF schematic provide easy access to pre-configured ADS WTB models (the models are complete, so the RF designer does not need to know internal test bench details). By simply inserting a WTB template the RF designer need only replace Amplifier2 with their RF DUT, specify test bench test frequency and/or power levels, and rely on the other default settings.
WTB models are provided for transmitter and receiver RF testing. Transmitter models provide standards-specific wireless transmitter tests such as constellation, CCDF, and EVM. Transmitter models can be linked to Agilent signal generator test instruments to further enable designers to use the same test signals from the WTB models to test their RF designs as well as hardware prototype of their RF designs. Receiver models provide standards-specific wireless receiver tests such as RF sensitivity.
The RF designer typically should use the WTB analysis after doing traditional measurements to achieve an acceptable performance from the RF designs. In the initial design stages the RF designer may have to stimulate the design with proper wireless standard signals.
Wireless sources are provided under Analog/RF Sources-Modulated-DSP-based library. These are configurable source components and their use model is similar to power sources such as P_1Tone; and, they can be used in different analyses such as Circuit Envelope, and S-parameter just like other sources.
Wireless sources generate RF signals that can be used in traditional simulations. Additionally, these can be used for wireless system measurements, such as WLAN EVM, using the set of wireless expressions. These wireless expressions can be used in MeasEqn block. For more complex receiver measurements, such as BER, you must use the wireless test bench models using the WTB analysis.
The wireless sources and expressions are useful in the initial phases of the RF development for traditional Analog/RF measurements. As the design matures, the RF designer must use WTB analysis and the corresponding wireless test bench models for more complete transmitter and transmitter system verification.
Wireless Test Bench Models
The following table lists the pre-configured wireless test bench models. These test benches provide comprehensive transmitter and receiver testing for 3GPP FDD, TD-SCDMA, and WLAN technologies. All measurements are performed according to wireless technology industry standard specifications. For details about using these models, see the online documentation:
Wireless Test Bench Models
Wireless Sources
The following table lists the wireless sources in A/RF schematic. These wireless sources provide standard compliant RF signals for WLAN, TD-SCDMA, and 3GPP FDD wireless technologies. In addition to the RF signal, the TD-SCDMA and 3GPP FDD sources provide baseband I and Q signals. These sources are highly configurable and can generate signals with different rates, power levels, impairments, etc. For details about these sources, see the online Components documentation Sources, Modulated-DSP-Based.
Wireless Expressions
The following table lists the commonly used wireless expressions for testing 3GPP FDD, WLAN, and TD-SCDMA transmitters.
See Measurement Expressions for details about using these expressions.
| Measurement | Expression Name |
|---|---|
| Baseband signal in time-domain | real() |
| EVM measurement for WLAN DSSS/CCK/PBCC | evm_wlan_dsss_cck_pbcc() |
| EVM measurement for WLAN OFDM | evm_wlan_ofdm() |
| Magnitude of carrier in time-domain | mag() |
| Phase of carrier in time-domain | phase() |
| Power - CCDF† | power_ccdf() |
| Power - Peak | peak_pwr() |
| Power - Peak to Average | peak_to_avg_pwr() |
| Power - Power vs. Time | pwr_vs_t() |
| Power - Total | total_pwr() |
| Spectrum analyzer † † | spectrum_analyzer() |
| Spectrum of carrier in dB | dB( fs() ) |
| Spectrum of carrier in dBm | dBm( fs() ) |
| Voltage | |
| † The power_ccdf_ref() expression, which generates a reference curve for the Power-CCDF measurement, can be used in transmitter testing. This expression is not available in the Expression Builder. † † The spectrum_analyzer() and fs() expressions can be used for spectrum measurement. Although spectrum_analyzer() uses fs() internally, it provides an easy way to set the measurement resolution bandwidth as well as video averaging. | |
RF Verification Examples
RF Verification examples demonstrate how to use wireless test benches, sources, and expressions. The examples can be accessed from the ADS Main window > File > Example Project :
- TDSCDMA > TDSCDMA_RF_Verification_prj
- WCDMA3G > WCDMA3G_RF_Verification_prj
- WLAN > WLAN_RF_Verification_prj
Required Licenses
Licenses required to use wireless test bench models, wireless sources, and wireless expressions are listed in the following table.
| Feature | Required Licenses |
|---|---|
| Wireless Test Bench Models, Sources, and Expressions (general) | sim_envelope sim_systime |
| 3GPP FDD W-CDMA Wireless Design Library for 3GPP FDD Wireless Test Bench Models, Sources, and Expressions |
mdl_wcdma3g |
| TD-SCDMA Wireless Design Library for TD-SCDMA Wireless Test Bench Models, Sources, and Expressions |
mdl_tdscdma |
| WLAN Wireless Design Library for WLAN Wireless Test Bench Models, Sources, and Expressions |
mdl_wlan |
| Connection Manager (for WTB models with instrument connectivity) download to Agilent ESG instruments | link_connect_mgr |
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