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