My 433MHz oscillator did not work!
My 433MHz oscillator did not work!
(OP)
I am designing a 433MHz oscillator using a SAW resonator and a Philips wideband transistor BFT25A connected as a Colpitts circuit. The circuit is described by the PSPICE file as attached below. According to the PSPICE simulation results, the oscillating frequency was totally controlled by the LC values. The SAW device contributed no effect to the circuit. How can I make the circuit oscillate at 433.92MHz with high stability?
433MHz Oscillator
VCC 2 0 3V
L1 2 4 26nH
R2 2 5 150k
C3 4 6 12pF IC=3
C4 6 0 10pF IC=3
R3 6 0 3.9k
XSAW 5 0 NMR433A
XQ1 4 5 6 BFT25A
.LIB MYLIB.LIB
.TRAN 10p 500n UIC
.OPTIONS ITL5=500000
.END
The PSPICE library "MYLIB.LIB" is attached as follows:
* My Own Library
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
* 433.92MHz SAW Resonator, Unloaded Q = 12,800, Ceratronics Limited.
*
.subckt NMR433A 1 2
*
rm 1 11 18
lm 11 12 86.0075uH
cm 12 2 1.56417fF
cp 1 2 1.7pF
cpar1 1 0 0.5pF
cpar2 2 0 0.5pF
.ends
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
* BFT25A SPICE MODEL
* PHILIPS SEMICONDUCTORS
* Date : September 1995
*
* PACKAGE : SOT23 DIE MODEL : BFT25A
* 1: COLLECTOR; 2: BASE; 3: EMITTER;
.SUBCKT BFT25A 1 2 3
Q1 6 5 7 7 QBFT25A
* SOT23 parasitic model
Lb 4 5 0.4n
Le 7 8 0.83n
L1 2 4 0.35n
L2 1 6 0.17n
L3 3 8 0.35n
Ccb 4 6 71f
Cbe 4 8 71f
*
* PHILIPS SEMICONDUCTORS Version: 1.0
* Filename: BFT25A.PRM Date: Feb 1992
*
.MODEL QBFT25A NPN
+ IS = 1.37749E-017
+ BF = 8.56539E+001
+ NF = 9.79900E-001
+ VAF = 5.08049E+001
+ IKF = 1.00000E+001
+ ISE = 2.19977E-015
+ NE = 1.85715E+000
+ BR = 1.69751E+001
+ NR = 9.85511E-001
+ VAR = 2.49144E+000
+ IKR = 1.88014E-001
+ ISC = 2.05160E-016
+ NC = 1.10731E+000
+ RB = 8.00000E+001
+ IRB = 1.00000E-006
+ RBM = 8.00000E+001
+ RE = 7.91100E+000
+ RC = 5.30000E+000
+ EG = 1.11000E+000
+ XTI = 3.00000E+000
+ CJE = 2.23030E-013
+ VJE = 6.69700E-001
+ MJE = 5.96638E-002
+ TF = 5.11209E-012
+ XTF = 7.90917E+000
+ VTF = 1.33880E+000
+ ITF = 5.66263E-003
+ PTF = 1.53714E+001
+ CJC = 2.29018E-013
+ VJC = 3.94786E-001
.ENDS
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
* end of library file
433MHz Oscillator
VCC 2 0 3V
L1 2 4 26nH
R2 2 5 150k
C3 4 6 12pF IC=3
C4 6 0 10pF IC=3
R3 6 0 3.9k
XSAW 5 0 NMR433A
XQ1 4 5 6 BFT25A
.LIB MYLIB.LIB
.TRAN 10p 500n UIC
.OPTIONS ITL5=500000
.END
The PSPICE library "MYLIB.LIB" is attached as follows:
* My Own Library
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
* 433.92MHz SAW Resonator, Unloaded Q = 12,800, Ceratronics Limited.
*
.subckt NMR433A 1 2
*
rm 1 11 18
lm 11 12 86.0075uH
cm 12 2 1.56417fF
cp 1 2 1.7pF
cpar1 1 0 0.5pF
cpar2 2 0 0.5pF
.ends
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
* BFT25A SPICE MODEL
* PHILIPS SEMICONDUCTORS
* Date : September 1995
*
* PACKAGE : SOT23 DIE MODEL : BFT25A
* 1: COLLECTOR; 2: BASE; 3: EMITTER;
.SUBCKT BFT25A 1 2 3
Q1 6 5 7 7 QBFT25A
* SOT23 parasitic model
Lb 4 5 0.4n
Le 7 8 0.83n
L1 2 4 0.35n
L2 1 6 0.17n
L3 3 8 0.35n
Ccb 4 6 71f
Cbe 4 8 71f
*
* PHILIPS SEMICONDUCTORS Version: 1.0
* Filename: BFT25A.PRM Date: Feb 1992
*
.MODEL QBFT25A NPN
+ IS = 1.37749E-017
+ BF = 8.56539E+001
+ NF = 9.79900E-001
+ VAF = 5.08049E+001
+ IKF = 1.00000E+001
+ ISE = 2.19977E-015
+ NE = 1.85715E+000
+ BR = 1.69751E+001
+ NR = 9.85511E-001
+ VAR = 2.49144E+000
+ IKR = 1.88014E-001
+ ISC = 2.05160E-016
+ NC = 1.10731E+000
+ RB = 8.00000E+001
+ IRB = 1.00000E-006
+ RBM = 8.00000E+001
+ RE = 7.91100E+000
+ RC = 5.30000E+000
+ EG = 1.11000E+000
+ XTI = 3.00000E+000
+ CJE = 2.23030E-013
+ VJE = 6.69700E-001
+ MJE = 5.96638E-002
+ TF = 5.11209E-012
+ XTF = 7.90917E+000
+ VTF = 1.33880E+000
+ ITF = 5.66263E-003
+ PTF = 1.53714E+001
+ CJC = 2.29018E-013
+ VJC = 3.94786E-001
.ENDS
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
* end of library file





RE: My 433MHz oscillator did not work!
The SAW doesnot contain any RLC component inside. SAW stand for surface acoustic wave. Inside the SAW their is a Glass or ceramic with 2 forks to transmite and recieive the ultra sound wave through the media.
The Q-value of SAW is very high. You can't implement it by RLC as the small size as SAW. The problem of SAW is high insertsion lost and the time delay may find in it.
The SPICE model is just a MODEL not the real. Just like the transistors' model does not contain any cap or R inside.
The SAW reject all the signal, taking about around 30db, except the frequency SAW's passband signal. I suggest you try to build the other SPICE circuit to figure out the respond of the SAW only. You will understand what I mean.
RE: My 433MHz oscillator did not work!
How can I make the circuit oscillate at the frequency of the SAW resonator? Your help will be highly appreciated.
RE: My 433MHz oscillator did not work!
Visit:
http://www.giscafe.com/DACafe/EDATools/EDAbooks/SpiceHandBook/09_chapter08-01.html
http://www.uoguelph.ca/~antoon/circ/circuits.htm
http://www.qct.nl/theory/types.htm
http://www.ee.washington.edu/conselec/Sp96/projects/mst/final/circoper.htm
http://www.sss-mag.com/cosc.html
etc. for more info. Also, the following papers appear to be informative:
O. De Feo, G. M. Maggio, M. P. Kennedy: "The colpitts oscillator : families of periodic solutions and their bifurcations", I. Journal of Bifurcation and Chaos, Vol. 10, Nr 5, pp 935-958, 2000.
G.M. Maggio, O. De Feo, M. P. Kennedy: "Nonlinear analysis of the colpitts oscillator and applications to design", IEEE CAS Transactions on Circuits and systems I, Vol. 46, Nr 9, pp 1118-1130, 1999.