Chapter 1. Introduction to RF and Wireless Technology
Compare two RF transceivers designed for cell phones:
“A 2.7-V GSM RF Transceiver IC” [1] (published in 1997)
“A Single-Chip 10-Band WCDMA/HSDPA 4-Band GSM/EDGE SAWLess CMOS Receiver with DigRF 3G Interface and +90-dBm
IIP
2
” [2] (published in 2009)
Why is the latter much more complex than the former? Does the latter have a higher performance or only greater functionality?
Which one costs more? Which one consumes a higher power? What do all the acronyms GSM, WCDMA, HSDPA, EDGE, SAW, and IIP
2
mean? Why do we care?
The field of RF communication has grown rapidly over the past two decades, reaching far into our lives and livelihood. Our cell
phones serve as an encyclopedia, a shopping terminus, a GPS guide, a weather monitor, and a telephone—all thanks to their
wireless communication devices. We can now measure a patient’s brain or heart activity and transmit the results wirelessly, allowing
the patient to move around untethered. We use RF devices to track merchandise, pets, cattle, children, and convicts.
1.1. A Wireless World
Wireless communication has become almost as ubiquitous as electricity; our refrigerators and ovens may not have a wireless device
at this time, but it is envisioned that our homes will eventually incorporate a wireless network that controls every device and
appliance. High-speed wireless links will allow seamless connections among our laptops, digital cameras, camcorders, cell phones,
printers, TVs, microwave ovens, etc. Today’s WiFi and Bluetooth connections are simple examples of such links.
How did wireless communication take over the world? A confluence of factors has contributed to this explosive growth. The principal
reason for the popularity of wireless communication is the ever-decreasing cost of electronics. Today’s cell phones cost about the
same as those a decade ago but they offer many more functions and features: many frequency bands and communication modes,
WiFi, Bluetooth, GPS, computing, storage, a digital camera, and a user-friendly interface. This affordability finds its roots in
integration, i.e., how much functionality can be placed on a single chip—or, rather, how few components are left off-chip. The
integration, in turn, owes its steady rise to (1) the scaling of VLSI processes, particularly, CMOS technology, and (2) innovations in RF
architectures, circuits, and devices.
Along with higher integration levels, the performance of RF circuits has also improved. For example, the power consumption
necessary for a given function has decreased and the speed of RF circuits has increased. Figure 1.1 illustrates some of the trends in
RF integrated circuits (ICs) and technology for the past two decades. The minimum feature size of CMOS technology has fallen from
0.5 μm to 40 nm, the transit frequency,
[1]
f
T
, of NMOS devices has risen from about 12 GHz to several hundred gigahertz, and the
speed of RF oscillators has gone from 1.2 GHz to 300 GHz. Also shown is the number of RF and wireless design papers presented at
the International Solid-State Circuits Conference (ISSCC) each year, revealing the fast-growing activity in this field.
[1]
The transit frequency is defined as the frequency at which the small-signal current gain of a device falls to unity.
Figure 1.1. Trends in RF circuits and technology.
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