Time Domain Corp. : Technology Overview

Historical Reference: Since the late 1880s, when wireless communications were first demonstrated, all practical uses of radio have relied on the transmission of continuous sine waves. The modulation of those sine waves allows the transmission and reception of information in either amplitude (AM radio) or frequency (FM radio). From 1890 to the present, industry has searched relentlessly for ways to send more information more reliably. Radio researchers have evolved techniques such as CDMA, TDMA, etc.

Now, the entire wireless landscape has changed. Larry Fullerton discovered that single RF monocycles could be transmitted through an antenna, and by precisely positioning these monocycles in time and then using a matched receiver to recover the transmissions, a whole new wireless medium was created, 'Digital Pulse Wireless' - a medium that does not rely on sine waves, does not require an assigned frequency, does not need a power amplifier, and is so random and low powered that it is indistinguishable from noise. The medium does require precise pulse placement in time (pulses are positioned with an accuracy of trillionths of a second), and it also requires a coherent correlating receiver - a Fullerton correlator. Larry Fullerton developed and patented the technology over the last decade.

Continuous Sine Waves vs. Coherent Cyclets.

Continuous sine waves are transmitted with information embedded in the modulation of the wave's amplitude or frequency. This technology is approaching its limit in being able to improve bandwidth (amount of information sent) and channelization (number of users).

Coded cyclets, transmitted and measured precisely in time can carry orders of magnitude more data and support an essentially unlimited number of users. (Think of it as super high-speed Morse Code with 40 million dots and dashes per second.)

Conventional signals transmitted in the frequency domain are highly "visible" electronically because all the power is packed into a narrow bandwidth, for example: 1 watt over 1 MHz. Time Modulation transmits millions of unstructured coded monocycles (cyclets) per second with emissions indistinguishable from noise and across an ultra wideband - yielding a virtually undetected communications link.

To understand this technology better, Time Domain offers several in depth technical papers:

Impulse Radio Overview, by Paul Withington of Time Domain Corporation

Multiple Access with Time-Hopping Impulse Modulation, by R. A. Scholtz, Invited Paper, IEEE MILCOM '93, Boston, MA, Oct. 11-14, 1993

In-building Propagation of Ultra-wideband RF Signals, by Paul Withington of Time Domain Corporation

Ultrawideband beamforming in sparse arrays, by F. Anderson, W. Christensen, L. Fullerton & B. Kortegaard, IEEE Proceedings - H, Vol. 138, No. 4, August 1991

Also, more information on UWB in general can be found on the Ultra Wideband Working Group site; http://www.uwb.org.

Click here for the URSI Radar Presentation given 1/4/99.