Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

capacitor selection for antenna tuning

Status
Not open for further replies.

dharithothi

Junior Member level 3
Joined
Dec 19, 2014
Messages
27
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
229
Hello Guys,

In antenna tuning for EM Prox (LF) can we use X7R capacitors??? They recommend NP0 capacitor only for antenna tuning... If I use X7R what will happen???
 

mtwieg

Advanced Member level 5
Joined
Jan 20, 2011
Messages
3,618
Helped
1,272
Reputation
2,550
Reaction score
1,273
Trophy points
1,393
Activity points
27,282
X7R is a class II dielectric while NP0 is a class I dielectric. Class I will tend to have higher stability in terms of voltage/temperature, and generally lower losses. Also class I dielectrics tend to have less piezoelectric effects. But these classifications are quite broad and if you really want to be sure then you should look at specific devices and their datasheets.
 

FvM

Super Moderator
Staff member
Joined
Jan 22, 2008
Messages
49,131
Helped
14,380
Reputation
29,024
Reaction score
13,134
Trophy points
1,393
Location
Bochum, Germany
Activity points
283,200
Intended coupler bandwidth and respective frequency stability requirements will answer the question. I won't use X7R for any kind of resonant circuit.
 

vfone

Advanced Member level 5
Joined
Oct 10, 2001
Messages
5,369
Helped
1,556
Reputation
3,115
Reaction score
1,167
Trophy points
1,393
Activity points
34,034
Yes, for high frequencies (>30MHz) X7R capacitors are not recommended for resonators, but for lower frequencies they should be fine.

**broken link removed**
 

D.A.(Tony)Stewart

Advanced Member level 5
Joined
Sep 26, 2007
Messages
7,059
Helped
1,721
Reputation
3,441
Reaction score
1,715
Trophy points
1,413
Location
Richmond Hill, ON, Canada
Activity points
51,810
What frequency?

The term "proximity card" refers to the older 125 kHz devices as distinct to the newer 13.56 MHz contactless smartcards.

You can also use diodes used as a varicap for fine tuning which increase in pF size with power rating but wide tolerance for any diode.
 

Quark-elec

Newbie level 3
Joined
Apr 16, 2015
Messages
4
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
21
Intended coupler bandwidth and respective frequency stability requirements will answer the question. I won't use X7R for any kind of resonant circuit.

Definitely! X7R normally used for digital and power area not RF/antenna field.
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top