80211b Transmitter Test Using Instrument Links

Introduction

WLAN_80211b_ESGc_prj project for IEEE 802.11b transmitter test design example is described in this chapter.

• WLAN_80211b_CCK_ESG4438C.dsn for generating CCK signal and sending the CCK signal to ESG 4438C to test WLAN CCK transmitter components.
• WLAN_80211b_25M_ESGc.dsn for providing adjacent channel test environment for testing CCK transmitter components.

Specification Requirements

Transmitter performance requirements are:

• Data rate: 11 Mbps
• Modulation type: CCK
• PSDU length: 1024 octets
• Modulation accuracy - EVM: 35%

Basic Transmitter System Test Using ADS-ESGc Link

WLAN_80211b_CCK_ESG4438C.dsn

Signal Parameters

• Data rate is 5.5 Mbps
• CCK modulation
• PSDU length is 100 octets

Description

This design demonstrates how to use the ADS-ESGc link to test a WLAN 802.11b/802.11g CCK transmitter system. Hardware and software requirements and setup information are provided.

Hardware Requirements

• Agilent E4438C signal generator with 100 MHz clock rate and 6 GHz carrier frequency.
• Agilent 89641A Vector Signal Analyzer (VSA) with 6 GHz carrier frequency or 89640A with 2.7 GHz carrier frequency.

Software Requirements

• Advanced Design System (ADS) version 2003A with WLAN option
  • To run complex designs of WLAN systems 500 MB RAM and 500 MB virtual space is required.
• Agilent Instrument Library version 2003A with GPIB and/or LAN interface component model.

PC Setup and Software Installation

1. Install ADS version 2003A or later version on your PC (Win2000, XP)
2. Install the WLAN Design Library.
3. Install ADS instruments library and set up the IO library using VISA layer for communicating to instruments

WLAN-ESGC link Setup

1. Connect ADS, ESGC, the device under test (DUT), and Agilent 89641A (or 89640A) as shown in the following figure. With this setup users can bring waveforms captured from VSA back to ADS for performing BER/PER performance in ADS.
   
   

   Transmitter Test System setup for WLAN 802.11b System

2. Switch on all instruments and the PC.
3. Start ADS and load schematic design WLAN_80211b_CCK_E4438C.dsn for signal generation as shown in the following figure.
   
   

   Signal Generation Design for CCK Transmitter

In the design, the model WLAN 802.11b/802.11g CCK signal source with hierarchical structure can generate an RF WLAN CCK signal with specific data rate, burst length, symbol clock, carrier frequency, and power. All signal parameters can be easily modified in the top level of the design. Two Var blocks (Signal Generation and RF_Measurement) are designed for ease of setting key parameters.The data rate is set to 5.5 Mbps. The signal is sent to ESG4438CSink E1, the ADS-ESGc interface for driving the Arb signal generator in ESGc.

Key parameters for the ESG4438Csink E1 must be set properly.

• Interface is the HPIB/GPIB interface or IP address. In this example we use the IP address to set this parameter Interface=141.121.237.165 (IP address).
• Address is the instrument address. We set it to 20 (the ESGc address).
• Start and Stop define the signal sequence length sent to ESGc that must be carefully set to keep the signal sequence contents an integer number of burst. In the example project, Start is set to 0, and Stop is set by an equation in RF_Var block.
  Stop is calculated as described next.
  Stop=[RampTime × 11e6 × 2+Idletime × 11e6+PLCP+PSDU]*Ratio;
  where Ramptime and Ideltime in µ are the 11b Signal Source parameters, PLCP = 192 × 11 for Long PLCP preamble, PLCP = (72+48/2) × 11 for short PLCP preamble. PSDU = Octets × 8 × 2 for 5.5 Mbps, PSDU = Octets × 8 for 11 Mbps.
  Ratio is determined by the 11b Signal Source parameter, Oversampling:
  Ratio=2: OverSampling=0
  Ratio=2.5: OverSampling=1
  Ratio=3: OverSampling=2
  Ratio=3.5: OverSampling=3
  Ratio=4: OverSampling=4
  Ratio=4.5: OverSampling=5
  Ratio=5: OverSampling=6
  Ratio=5.5: OverSampling=7
  Ratio=6: OverSampling=8
  Ratio=6.5: OverSampling=9
  Ratio=7: OverSampling=10
  Ratio=7.5: OverSampling=11
  Ratio=8: OverSampling=12

ESGc Settings

ARB generator in ESGc is driven by WLAN RF signal source in ADS through HPIB/LAN. Follow the ESGc setup sequence

ARB Settings

1. Press panel button Mode > Dual ARB
2. Press ARB on/off to ARB off
3. Press ARB set up
4. Set the ARB sample clock to 80 MHz for this example
5. Set the ARB Reference to Int
6. Set the Reconstruction Filter to Through
7. Press Select/Waveform and select the name of the file defined in the model ESG4438CSink, for example wlan_24
8. Press panel button Mod On/Off to ensure Mod On
9. Press panel button RF On/Off to ensure RF On
10. Press Frequency and set to 2.4 GHz
11. Press Amplitude and set to -5dBm
12. Press ARB On/Off to ensure ARB On

Set up the design under test.

1. The DUT can be any component in a transmitter. As an example, we test a power amplifier as the DUT. The expected performances are listed are: output power 15 dBm for carrier 2.4 GHz.
2. Connect the input to the ESGc and Output to VSA89641A.
3. Make sure the power supply is set properly and turned on.

VSA 89641A Settings

The VSA 89641A must be connected to a PC that has an IEEE 1394 card and VSA software with WLAN flavor (option B7R) installed. When installing the VSA software, the IEEE 1374 option must be turned on.
Set up the measurement settings:

1. Click MeasSetUp, then set the demodulator type by clicking Modulator , then select Wireless Networking > DSSS/CCK/PBCC
2. Set frequency:
   • Click Frequency , then enter the correct center frequency and frequency span (you can use the full span button).

Set up the input settings:

1. Click Input , then set data format to hardware .

The VSA software settings for transmission test can now be saved as a set file for example, 11b.set . The saved set file can then be called and will use the above settings. A set file has been made that can be found in the data directory under this project; make sure you use the correct set file.

Under this setting, the EVM is measured to see if the power amplifier can be used as a transmitter power amplifier based on IEEE 802.11b std. Simulation results are compared to the standard.

Simulation Results

EVM = 3%, that is less than the standard value 35%.

Benchmark

• Hardware platform: Pentium IV 1.8GHz, 512 MB memory
• Software platform: Windows 2000, ADS 2002C
• Simulation time: approximately 10 minutes

References

1. IEEE Standard 802.11b-1999, "Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: High-speed Physical Layer Extension in the 2.4 GHz Band," 1999.

Transmitter Test Under Adjacent Channel Environment

WLAN_80211b_25M_ESGc.dsn

Features

• Data rate is 11 Mbps
• CCK modulation
• PSDU length is 1024 octets
• In-channel carrier: 2.412 MHz, adjacent channel carrier: 2.437 MHz
• Adjacent channel power is 35 dB higher than in-channel

Description

This design tests a WLAN IEEE 802.11b CCK transmitter under adjacent channel environment. Hardware and software requirements and setup information are provided.

Hardware Requirements

• Agilent E4438C Signal generator with 100 MHz clock rate and 6 GHz carrier frequency.
• Agilent 89641 A Vector Signal Analyzer (VSA) with 6GHz carrier or Agilent 89640A with 2.7 GHz carrier frequency plus PSA E4440A as a down-converter.

Software Requirements

• Advanced Design System (ADS) version 2003A or later with WLAN option
  • To run complex designs of WLAN systems 500 MB and 500 M bytes virtual space is required.
• Agilent Instrument Library version 2003A with GPIB and/or LAN interface component model.

PC Setup and Software Installation

1. Install ADS version 2003A or later version on your PC (Win2000, XP).
2. Install WLAN library.
3. Install ADS instruments library for and set up the IO library using VISA layer for communicating to instruments.

WLAN-ESGC Link Setup

1. Connect ADS, ESGC, the device under test (DUT), and Agilent 89641A as shown in the following figure. With this setup users can bring waveforms captured from VSA back to ADS for performing BER/PER performance in ADS.
   
   

   Test Setup

2. Switch on all instruments and the PC.
3. Start ADS and load schematic design WLAN_80211b_CCK_E4438C.dsn for signal generation as shown in the following figure.
   
   

   Signal Generation for Adjacent Channel Test

In the design, the model WLAN 802.11b/802.11g CCK Signal Source with hierarchical structure can generate an RF WLAN CCK signal with specific data rate, burst length, symbol clock, carrier frequency, and power. All signal parameters can be easily modified in the top level of the design. Two Var blocks (Signal Generation and RF_Measurement) are designed for ease of setting key parameters. The data rate is 5.5 M bps. The signal is sent to ESG4438CSink E1, the ADS-ESGc interface for driving the Arb signal generator in ESGc.
Key parameters for ESG4438Csink E1 must be set properly.

• Interface is the HPIB/GPIB interface or IP address. In this example we set Interface=141.121.237.165 (IP address).
• Address is the instrument address. We set it to 20 (the ESGc address).
• Start and Stop define the signal sequence length sent to ESGc that needs to be set very carefully to keep the signal sequence contents an integer number of burst. In our example projects for transmitter and receiver tests, Start and Stop have been set automatically. For understanding the way to calculate them the process steps are described in the schematic design.

ESGc Settings

The ARB generator in ESGc is driven by the WLAN RF signal source in ADS through HPIB/LAN. Follow the ESGc setup sequence.
Set up the ARB.

1. Press panel button Mode > Dual ARB
2. Press ARB on/off to ARB off
3. Press ARB set up
4. Set the ARB sample clock to 80 MHz for this example
5. Set the ARB Reference to Int
6. Set the Reconstruction Filter to Through
7. Press Select/Waveform and select the name of the file defined in the model ESG4438CSink, for example wlan_24
8. Press panel button Mod On/Off to ensure Mod On
9. Press panel button RF On/Off to ensure RF On
10. Press Frequency and set to 5.8 GHz
11. Press Amplitude and set to -5dBm
12. Press ARB On/Off to ensure ARB On

Set up the design under test.

1. The DUT can be any component in a transmitter. As an example, we test a power amplifier called TT-64 as the DUT. The expected performances are: output power 17 dBm for carrier 5.8 GHz.
2. Connect the input to the ESGc and Output to VSA89641A.
3. Make sure the power supply is set properly and turned on.

VSA 89641a Settings

The VSA 89641A must be connected to a PC that has an IEEE 1394 card and VSA software with WLAN flavor (option B7R) installed. When installing the VSA software, the IEEE 1374 option must be turned on.
Set up the measurement settings:

1. Click MeasSetUp and set demodulator type by clicking Modulator ; then select Wireless Networking > DSSS/CCK/PBCC.
2. Set frequency:
   • Click Frequency and enter the correct center frequency and frequency span (you can use full span button).

Set up the input settings:

1. Click Input and set data format to hardware .

The VSA software settings for transmission test can now be saved as a set file; for example, 11b.set . The saved set file can then be called and will use the above settings. A set file has been saved in the data directory under this project: make sure you use the correct set file.

Simulation Results

Simulation results displayed in WLAN_80211b_RxMaxInput_Sensitivity.dds are shown in the following figure. BER and PER at given input levels are simulated.

WLAN_80211b_RxMaxInput_Sensitivity.dds

Benchmark

• Hardware platform: Pentium IV 1.8 GHz, 512 MB memory
• Software platform: Windows 2000, ADS 2002C
• Simulation time: approximately 85 minutes

References

1. IEEE Standard 802.11b-1999, "Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: High-speed Physical Layer Extension in the 2.4 GHz Band," 1999.