High Order Harmonic Oscillators in Microwave and Millimeter-wave ...

3 8th Harmonic Oscillator
λg/2@f0
2
3
λg/8@f0
4
N.R.
1
Output(8f0)
5
N.R.
8
6
7
(a) Layout of the proposed oscillator.
+
f0
2f0 4f0 6f0 8f0
0
-
1 2 3 4 5 6 7 8 1
Position
(b) Resonant mode in the one wave-length (λ g ) ring resonator.
Fig. 3.4: Push-push resonant mode in the proposed oscillator.
output circuits is connected to the microstrip ring resonator with the interval of λ g /8 at
the fundamental frequency, that is, one wave length at the 8th harmonic frequency. Figure
3.6 shows the detailed layout at the coupling points. The line width at the coupling points
is narrow to form the loose coupling between the resonator and the output circuit in order
to stabilize the resonant fields. Figure 3.7 shows the input impedance characteristic of the
two same negative resistance circuits simulated by the ADS. HEMTs (FHX35LG, Fujitsu)
are used in the negative resistance circuits. The impedance at the port 1 and port 2 in
Fig. 3.5 shows negative resistance at the fundamental frequency of 6.5 GHz. Gate and
33