EFFICIENT
LOW–NOISE THREE PORT X-BAND
Laboratoire U.E.R. des
FET OSCILLATOR
USING
aretheconstan~ electrical length (63) arcs. It may be noted that instability (S1l or S22 > l)is created for values of coupling factor as low as = 0.8. The optimum values of the transmission line length ’83 and coupling
Introduction
(one
pled The are
main
presents total in addition and
two
resonator
Equivalent
circuit
to a microstrip input impedance given by : z.
In
=
elimination to possessing
of
a dielectric
1 + 2j
rin
at
f
o
=&
e
oscillation figure 1, (
{S}
Det.
(
respectively.
{I}
The coupling for the dielectric to optimise the
resonator
cou–
in figure coefficient
2 {2} rin
0,
represents the the microstrip
15 GF has
factor of the is a function
series
{S’} {S}
feedback
By using the dielectric resonator feedback element at the source terminal, selective instability in an F.E.T. can
-
for
the
{4}
{I}
{S’}
-
mapping.
)1
>0 O
S-matrices embedding
the
factor 6 resona~or oscillation
oscillator
:
{1})=
represent the of the passive represents
unit
of the network
matrix.
and electrical 1 can now be condition.
configuration oscillator. output while
oscillator the
using
following
length 6 calculat~d
results in a three (drain) output @ output @ (gate) and
a Thomson-CSF
characteristics
frequency
f.
Efficiency -----——--Pushing
: 22
:4V;
ID:23mA
% 300
DSB FM Noise -.-.--_-----—
element
MHZ
: ‘DS
figure
transistor :
: 853o
‘ias
at as
above
realisation
oscillation
of the distance between the resonator and the line, for fixed shielding conditions {2} . (3 represents the electrical length in degrees and Q , the unloaded qua– resonator lity factor of the resonator. The dielectric used for the present work, fabricated by THOMSON–CSF, consists of lead doped Zirconium titanate oxide, has a relative permittivity of = 38 and Q. of = 4,000 at 9 GHz, under the employed shielding conditions. Dielectric resonator of an F.E.T.
the
Using the above approach two oscillators were realised. An oscillator using NEC 13’700 delivered 8 mW at 10.5 GHz at the main power output port with a total efficiency of 21 %.
A/2,...)
-2j8
coupling line and
from
@ (source) represent auxiliary outputs where afraction of the main output power is available. Due to the presence of the dielectric resonators in series the outputs ~ and @ present with the output lines, a very high external Q {3} .
Another where (3= R/2Zo resonator with
found
ports
Practical
=
be
condition given by
is
where {S } and {Sf} transistor and that
2B Qo(f-fo)/fo
~+ 1
can
This oscillator output ports stable represents the main
line is presented Z,in and reflection
1 +
63
condition
I Det
be used design low FM
of parasitic 3 output
The in
Arg.
characterisation
(for6 and
shown
auxiliary).
Dielectric
factor
Oscillation
A new type of highly stable oscillator using two identical dielectric resonators is presented here {1 }. The dielectric resonators coupled to 50 ohms microstrip lines acting as high Q reactance for gate and source terminals of the transistor, are used to realize the oscillation condition. Drain terminal connected to a 50 ohms line, serves as the main RF output port (figue 1). The oscillator presented has a number of interesting features. The microstrip circuit part is simplified to 50 ohms line at each terminal of the
noise, and oscillations
-France-.
shows for example these parameters for a THOMSON-CSF 15 GF at 8.5 GHz as a function of E and 6 . transistor The non concentric’ circles represent the const$nt COU2 pling factor (B ) circles while the intersecting arcs
A new, simple to realize, X band, 3 port stable FET oscillator is presented. The oscillator using 2 identical dielectric resonators as oscillator circuit elements, operates at 8.53 GHz, has an overall effi– ciency of 22 $ and FM noise better than 0.2 Hz/ & at 10 KHz from carrier.
can
o-4
RESONATORS.
A.P.S. Kbanns., J. Obregon, Y. Garault d’Electronique des Microondes - E. R.A. au CNRS 535 Sciences - 123, rue Albert Thomas 87060 LTMOGES Cedex
Abstract
transistor, hence the same transistor chip for S–parameter chare,cteriaation, theoretical and final realisation. It has high efficiency,
TWO DIELECTRIC
KHz/VDS
:
10KHz:<.2Hz/= 100
KHz
:
< .07HZ
/
l&-
as
a series the desired be simply and
effectively created {3} (figure 3). Using the series feedback mapping technique, the impedance presented can be mapped into the S-parameby the resonator Zi ters of the two pod shown in figure 3. Figure 4
19821EEEMTT-s
DIGEST
277
0149 -645 X/82/0000-0277
$00.75 @ 19821EEE
Acknowledgement
Power
Output
External
Q
‘
‘+
I
Thanks Corbeville help.
‘“*
.
1. A.P.S.
Khanna and des ~ transistor, et trois sorties”, 198I. sept.
Discussion In addition the oscillator resting features .)
to high presented :
efficiency above has
and low a number
2.
FM noise, of inte-
simplification ..-.-—— _______
The microstrip part of the oscillator has been simplified to 50 ohms lines on every terminal of the transistor and the oscillation condition is optimised by placing the two dielectric resonators at predetermi– ned distances (d and 8 ) from the gate and source terminals, This also indicates the broadband nature of the passif circuitry, as changing the oscillator frequency calls placing titular
only for changing the them at the calculated frequency. ..)
dielectric distances
resonators for the
and par–
elimination _____________________________ of parasitic oscillations --—--_-—
Another advantage of the oscillator configuration presented is the total elimination of the parasitic oscillations due to highly selective transistor instability created by using dielectric resonators. The oscillation condition is satisfied only at the resonator centre frequency and all the transistor terminals are loaded by 50 ohms impedances at all other frequencies. . ..)
multiple Output Ports _-_— _________________
This oscillator has one main and output ports. This aspect is generally ture for system applications, as this cing the number of passive components and power very high frequency, . ...)
dividers. external immune
to DCM and LCR of France – for their
Both the auxiliary Q factor , making to their respective
two auxiliary a desired fea– can help in redulike couplers
outputs thus the use in
have a oscillator the system.
maximum power output -———________________
It may be noted that the power ther optimised by using a quarterwave former at the drain terminal (figure
output can impedance 1).
THOMSON-CSF technological
References
17,200
1650
28,000
are due ORSAY -
be furtrans-
278
P. Guillon et al. using a dielectric Pt. H No 3 June
Y. Garault, “Oscillateur microon5 deux r6sonateurs di61ectriques French CNRS Patent no 81/17934
, “Microstrip resonator”, 198I, pp.
bandstop IEE Proc. 151-154.
filter vol.
128
“Oscillateurs microondes stables Khanna, ~ transistors et r6sonateurs di61ectriques”, Docteur-Ing6nieur, University of Limoges Sept. 1981.
3.
A.P.S. t6gr6a Thesis France,
4.
A.P.S. Khanna and J. Obregon, “Microwave oscillator analysis”, IEEE Trans. on MTT, vol. MTT-29 no june 1981, pp. 606-607.
in-
6
,---
LJ i ~ib:ure two
1
Three
port
stable
oscillator
Resonators
Dielectric
z
3
.F’igu~e
using
Dielectric
Resonator
as
a series
(D.R.l & D.R.2)
A
i1
i
I
=0
/rb
Al
Figure Dielectric #--,# *
Resonator -*,*&I t
coupled
to
2 a micro:]trip
line
and
its
equivalent
-.. ‘\
,/
~--
,.
circuit
--T---8
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\ \
--+--y;--; I $ 1s
\ ‘<
\
\\
1’ t’
/
1
y-.”
\
4’
;?5 ‘.
‘--
,.’” ..”
------- :
~-.--,---,0
#“
‘.,
1 I \
,/
\ \\ \
tl
It 1’
/
t
1 \
\
\
%22
Transistor
two
coupling
port
S–parameters
(B3)
and
as
transmission
a i’unctioll line
279
length
of
\\
‘\
/
~# %
t \\ t’ \ ‘. : -. --J----
dielectric (03)
‘\
. ‘\
~\
x+
+.+
,/
/
-_-$” -d”
1 I
.“
resonator
parameters.
\
\ \ ,----#~\
~----.-------:----.--==.-
\
I
45f
@
\
s ?2
s
\
~->$-?,
75
\ \ \
.>
/ If k
t I \
\\
- .*
/.
1) 1’ L-+--’ \
●* .
tT4’\
/’
1
-.
1
~;’ q q ,’ Cl”
4!9
4 /’
(IJ.R.2)