RF design book suggestions 2

[blcpro]

Hello all,
I was just beginning a project which will require me to build and specify an antenna for low frequency RFID (134 kHz). I've designed a module to handle the RFID communications, and have built working prototypes using a design template from the manufacturer of the chip I'm using. However, I have no experience designing RF antennas. I'm hoping some of you can suggest some good RF design books.

Thanks a bunch!

 

[leonar40]

Try a book called "Antenna Theory and Design" by Warren L. Stutzman. It's a great book. If you like more interactive stuff, Georgia Tech Professional Studies has an Antenna Design class in Atlanta GA coming up in April.

 

[blcpro]

thanks leonar40, I'll check it out!

 

[maged541946]

Another book, Antenna Engineering Handbook
By Henry Jasik
McGraw-Hill Book company

 

[blcpro]

Thanks to you too maged!

 

[malofquISt]

stutzman was my advisor at VA Tech!! he's so funny

 

[sensortech]

Do you know any 134 KHz antenna products or designs you can share? I also started to design an RFID system for 125/134 KHz band. Thanks.

 

[blcpro]

sensortech,

All of my work with RFID is based on chips from Texas Instruments. While they do have good documentation on the use of their chips, I still thought I needed more antenna design knowledge.

Anyway... that's besides the point of your question. I found Texas Instruments to be a valuable source of information and design examples (using their chips, of course).

 

[Warpspeed]

Strictly speaking, an antenna is designed (and impedance matched) to transmit and receive electromagnetic energy in the far field. That is, greater than several wavelengths from the source. At 135 Khz that will be a very considerable distance (several miles). The physical dimensions of a self resonant antenna at that frequency will also become excessively large for typical localized RFID applications within buildings.

Due to range and wavelength requirements at that low operating frequency, any "antenna" will of necessity be operating in the very near field, and a different approach is needed. I doubt if classical antenna theory from books will help very much, because this is not a normal antenna application.

The texts mainly concern the design of antennas for launching and receiving signals into free space over very long distances.

A better way might be a very open inductive pickup loop made to enclose as large an area as possible consisting of several turns, and tuned broadly to resonance. As a rule of thumb, the bigger it is the more energy it will intercept. The tuned Q should be high enough to increase sensitivity, but not so high it becomes easily detuned by surrounding objects. It is just a length of multicore cable formed into a loop, with the individual wires joined in series.

For receiving low frequency signals, the most compact method possible is a ferrite rod antenna, again broadly tuned to resonance.

Some experimentation and ingenuity may be required, but a workable system should not present too many difficulties.