Communications: directive radio wave systems and devices (e.g. – Radar transponder system – Radar transponder only
Patent
1993-01-21
1995-05-09
Sotomayor, John B.
Communications: directive radio wave systems and devices (e.g.,
Radar transponder system
Radar transponder only
342 42, G01S 1380
Patent
active
054144272
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a device for information transmission, a so-called transponder, for receiving a first microwave signal, for modulation and coding, and for retransmitting a second microwave signal, comprising at least one antenna means made in microstrip technique.
BACKGROUND OF THE INVENTION
Using microwave technique for information transmission to and from transponders has been known for a long time and is described in inter alia U.S. Pat. Nos. 4,242,661 "Device for registration of objects" and 4,390,880 "Radio communication system and transmitter and receiver equipment therefor".
It is further known from U.S. Pat. No. 4,673,936 to integrate a microwave unit with a wrist watch, but that invention is intended as an emergency transmitter and comprises an active frequency sweeping microwave oscillator built into the watch and intended to be detected by a reconnaissance radar onboard a ship, thereby differing from the present invention in which no microwave oscillator in included, but in which information from the transponder is fetched through passive modulation and reflection of an illuminating microwave signal. In addition, the mentioned device uses an entirely different antenna technique than the one presented here.
In many applications simultaneous demands are placed on good range, directionality and compact dimensions in the transponder, while, at the same time, the transmission frequency, which determines the size of the antenna, is predetermined for technical reasons or due to authority regulations.
It is general for all antennae that their dimension in otherwise static conditions are in inverse proportion to their operational frequency. Thus, an antenna at e.g. 5 GHz has half the extension of a 2.5 GHz antenna.
Furthermore, the capability of the antenna to receive microwave radiation is directly proportional to its effective antenna area, and since a lower frequency antenna due to its larger physical dimensions has a larger antenna area (square meter), it is capable of detecting more power (Watt) if it is in a microwave field of a certain power density (Watt per square meter) than would a higher frequency antenna with the same direction characteristics.
A high-frequency antenna can per se be given an increased effective antenna area by grouping several smaller antenna means side by side, but then there is the disadvantage of greater complexity and in that its directionality increases unfavourably, because the transponder must be directed carefully at the write/read unit in order to obtain a good range.
A transponder with a large effective antenna area and few antenna means in proportion to its total physical area therefore gives great advantages in applications with simultaneously high demands on compactness, range and freedom of orientation at a given radiation level.
Usual transponder frequencies are 2.45 GHz and 5.72 GHz, as there are internationally provided frequency bands which are commonly used for identification systems. Also 24 GHz has been provided internationally but has not yet come into any practical use, foremost due to high costs and low range performance. 2.45 GHz is also used by microwave ovens and through their widely spread usage, among other things, it is anticipated that this frequency will remain publicly available in the foreseeable future.
The mentioned frequencies are sufficiently low to enable the use of inexpensive silicon semiconductors and microstrip solutions in the microwave circuits, at the same time as the requirements for mechanic precision in impedance determining microstrip elements are moderate. The frequency is, however, sufficiently high for printed microstrip antennae to be used, which makes thin and easily manufactured antenna designs possible.
A well designed transponder with microstrip antenna has usually a radiation diagram that has its principal direction in the normal plane of the antenna layer, outwards from the antenna layer, while its sensitivity in the opposite direction is considerably depressed provided that the transponder anten
REFERENCES:
patent: 4242661 (1980-12-01), Henoch et al.
patent: 4390880 (1983-06-01), Henoch
patent: 4442590 (1984-04-01), Stockton et al.
patent: 4600906 (1986-07-01), Blight
patent: 4673936 (1987-06-01), Kotoh
patent: 4771291 (1988-09-01), Lo et al.
patent: 4813025 (1989-03-01), Rowland et al.
patent: 4855749 (1989-08-01), DeFonzo
patent: 4893126 (1990-01-01), Evans
patent: 4908615 (1990-03-01), Bayraktaroglu
patent: 4926187 (1990-05-01), Sugawara et al.
patent: 4933680 (1990-06-01), Shapiro et al.
patent: 5001492 (1991-03-01), Shapiro et al.
patent: 5025247 (1991-06-01), Banks
patent: 5119099 (1992-06-01), Haruyama et al.
patent: 5212494 (1993-05-01), Hofer et al.
LandOfFree
Device for information transmission does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device for information transmission, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device for information transmission will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1709113