RF Measurements for Cellular Phones and Wireless Data Systems

Allen W. Scott, Rex Frobenius

• Publisher: Wiley-IEEE Press
• Year: 2011
• ISBN:
  9781118210314
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Electrical Engineering & Telecommunications
• Index: Technology & Engineering

The only source for practical, real-world information on RF measurements for cellular phones and wireless data systems

It is predicted that by the year 2010, all digital wireless communications equipment—including cellular, PCS, and 3G phones; wireless LANs; GPS navigation systems; and DBS TV—will have data transfer capabilities of over 1 Mbps. Now, as this significant turning point quickly approaches, this book presents everything industry professionals need to know about the Radio Frequency (RF) measurements and tests that must be made on this new generation of digital wireless communications equipment.

Presenting just enough theory as is absolutely required for comprehension, RF Measurements for Cellular Phones and Wireless Data Systems:

• Provides a review of basic RF principles and terminology
  
  

• Describes RF measurement equipment, including signal generators, power meters, frequency meters, vector network analyzers, spectrum analyzers, and vector signal analyzers
  
  

• Explains the RF devices that are used in cellular phones and wireless data transmission equipment—how they work, what their critical performance parameters are, how they're tested, and typical test results
  
  

• Illustrates the testing of RF devices and systems with digitally modulated signals that represent the voice, video, or data that the RF wave is carrying
  
  

RF Measurements for Cellular Phones and Wireless Data Systems has been written to serve as the industry standard for RF measurements and testing. It is an indispensable resource for engineers, technicians, and managers involved in the construction, installation, or maintenance of cell phones and wireless data equipment.

CHAPTER 1

INTRODUCTION

1.1 THE MARKET FOR CELLULAR PHONES AND WIRELESS DATA TRANSMISSION EQUIPMENT

The market for cellular phones and wireless data transmission equipment has changed dramatically since the late 1970s when cellular phones were first introduced and the late 1980s when wireless data equipment became available. As would be expected, during this time RF test requirements and RF test equipment has changed dramatically.

The original cellular phones, which were introduced in North America in the 1970s, were FM analog voice phones with a limited data capability of less than 10 kbps. These analog phones are now called first generation (1G). Cellular phones were digitized in the early 1980s to provide for an increased number of user channels in a given RF frequency band. These digital phones are now called second generation (2G).

During the 1990s the use of 2G cell phones increased dramatically throughout the world, growing to over 2 billion handsets worldwide by 2005. Eighty percent of 2G phones are Global System for Mobile Communications (GSM), using digital FM modulation. The reasons for the expansive growth of GSM phones was (1) the excellent voice quality of the digital signal, which could accurately digitize any language, and (2) an effective worldwide management and billing system for all of its customers.

During the growth of GSM phone capacity worldwide, the North American cellular industry was divided between proponents of using a Time Division Multiple Access (TDMA) system similar to GSM, but carefully designed to be backward compatible with the RF part of the original analog system, and a new Code Division Multiple Access (CDMA) concept advocated by Qualcomm, which provided greater user capacity in a given RF bandwidth. After extensive field trials conducted throughout the United States in the late 1980s, the CDMA system demonstrated an approximate doubling of voice capacity compared to TDMA.

As digital voice cell phone usage grew in the 1980s, equipment manufacturers began the development of third generation (3G) phones that, in addition to providing high-quality wireless voice service, could also provide a wide range of data related services including the following:

• Data rate transfer exceeding 1 Mbps at any location within the cell where voice phones worked
• Wireless connected photographic cameras
• Wireless connected video cameras
• GPS information
• Windows operating system with Word, Excel, and PowerPoint
• Internet access

In order to accomplish this high data rate capacity, the greater bit rate transfer capability of CDMA systems is required. It is predicted that all cellular phone systems will be converted to CDMA by 2012.

The 20% of system operators who had originally opted for CDMA voice phones are already providing data transfer capability up to 1 Mbps, even though voice service still accounted for 90% of their business in 2005.

The GSM service providers, who provide 80% of worldwide cellular voice service, face an economic problem because of the vast amount of installed GSM base station equipment. However, the GSM community now has a worldwide evolution plan to grow from the limited 100 kbps data capability of GSM phones to a data capability of several gigabits per second using Wideband Code Division Multiple Access (WCDMA)/High-Speed Downlink Packet Access (HSDPA). However, the implementation of this high data rate equipment by the GSM community will lag that of the current CDMA carriers by about 3 years.

The importance of these facts is that the measurement equipment needs for cellular phone equipment are stabilized for the next 5 years, until fourth generation (4G) phones replace the 3G phones.

In a similar way, the requirements for short-range, high data rate equipment like Wi-Fi (802.11a, b, g, and n) are stabilized. These systems achieve data rates up to 200 Mbps because their ranges are short. Consequently, the received power is high and complex modulation schemes like 64-quadrature amplitude modulation (64QAM), which transmits 6 digital bits in every Hertz of bandwidth, can be used.

A significant change in RF test equipment occurred in the early 2000s in order to meet the needs of testing the evolving cell phone and wireless local area network (LAN) equipment. Extensive digital processing was added to conventional RF signal generators, vector network analyzers (VNAs), and spectrum analyzers to improve their measurement uncertainty and increase their capability.

For example, many of the newest VNAs now use a Windows operating system instead of a proprietary operating system. This change gives increased capacity for data processing and allows measurements to be easily transferred to laptops or other computers for further analysis and archiving. Electronic calibration of the VNAs is now available to reduce the uncertainty of their measurements that is due to handling damage of the calibration standards and operator error. Measurement of absolute power in decibels relative to 1 mW (dBm) in a VNA is about ±1 dBm. Provision is now available to calibrate the VNA with a power meter and achieve power measurements within an uncertainty of only ±0.2 dBm.

Hardware and software options can now be added to the latest generation of spectrum analyzers to permit them to make the specialized signal analysis measurements required for cell phone and wireless LAN. These upgrades to the spectrum analyzers include the following:

• Measurement of phase noise and noise figure
• Measurement of the spectral regrowth of digitally modulated RF carriers
• Ability to function as a vector signal analyzer (VSA)
• Measurement of the key specifications for any cell phone or wireless LAN system

The life cycle of RF measurement equipment (with hardware and software upgrades) is about 15 years, so the latest versions of RF measurement equipment will cover RF measurement needs throughout the lifetime of the current cell phone and wireless LAN evolutions.

1.2 ORGANIZATION OF THE BOOK

RF Measurements for Cellular Phone and Wireless Data Equipment is organized as follows:

Part I (Chapters 2–4) provides a review of basic RF principles. Many of the users of this book already have knowledge of basic RF terminology, but many do not. For those users who do not, Part I will provide this knowledge and should be studied first. For those users who have this knowledge already, Part I will provide a good review.

Part II (Chapters 5–14) describes RF measurement equipment, including signal generators, power meters, frequency meters, VNAs, spectrum analyzers, VSAs, and other equipment.

Part III (Chapters 15–28) describes the RF devices that are used in cellular phones and wireless data transmission equipment: how they work, what their critical performance parameters are, how they are tested, and what typical test results are.

Part IV (Chapters 29–36) describes the testing of RF devices and systems that use digitally modulated signals to represent the voice, video, or data that the RF wave is carrying. The same RF device will have different performance, depending on the data modulation being used.

1.3 PART I: RF PRINCIPLES

Chapters 2–4 in Part I describe RF principles.

1.4 SUMMARY OF CHAPTER 2: CHARACTERISTICS OF RF SIGNALS

Chapter 2 describes the characteristics of RF signals, which include frequency and wavelength, power (dB and dB relative to 1 mW), and phase.

The range of RF power that must be measured in cellular phones and wireless data transmission equipment varies from hundreds of watts in base station transmitters to picowatts in receivers.

For calculations to be made, all powers must be expressed in the same power units, which is usually milliwatts. A transmitter power of 100 W is therefore expressed as 100,000 mW. A received power level of 1 pW is therefore expressed as 0.000000001 mW. Making power calculations using decima...

Table of contents

• COVER
• TITLE PAGE
• COPYRIGHT
• FOREWORD
• ACKNOWLEDGMENTS
• CHAPTER 1: INTRODUCTION
• PART I: RF AND WIRELESS PRINCIPLES
• PART II: RF MEASUREMENT EQUIPMENT
• PART III: MEASUREMENT OF INDIVIDUAL RF COMPONENTS
• PART IV: TESTING OF DEVICES WITH DIGITALLY MODULATED SIGNALS
• TERMINOLOGY
• INDEX