| Summary: | 碩士 === 國立交通大學 === 電信研究所 === 83 === Two type of different mixer are designed,Fabricated,and
measured in this thesis. One is the millimeter-wave Ka-band
cross-bar waveguide balanced diode mixer,the other is the
microwave X-band subharmonically resistive mixer, the two-stage
RF low-noise prea- mplifier are also made for the X-band mixer.
The nonlinear CAD tools are used to simulate their performance.
Comparison of these mixers are also discussed. The first type
of the mixer is a ka-band low-conversion loss, high LO-RF-IF
isolation balanced cross-bar waveguide diode mixer. The
suspended stripline circuit is used, it is very suitable for
millimeter-wave because of its low dilectric loss and low
disper sion. The use of hybrid circuit technologies and beam-
lead diodes provides the advantage of low cost, light weight
and small size which is suitable for communication systems.
Experimental results from 32 GHz to 34 GHz exhibits a
conversion loss of less than 8 dB,and more than 22 dB
isolation. The second type of the mixer is a new type of
resistive mixer. The mixer conversion loss is the same as the
diode mixer, the noise figure is lower than the diode mixer;and
the IP3 and P1-dB is higher than the diode mixer, which uses
the zero drain bias channel resistance of a GaAs MESFET to
achieve frequency mixing. This channel resistance is high
linear,very low intermodulation can be achieved. To understand
this mixer, first, we design a single MESFET X-band resistive
mixer. The mixer conversion loss is less than 9 dB from 9.5GHz
to 11 GHz, 16.9 dBm output third- order intermodulation
intercept point, and 4.5 dBm output 1-dB compression point.
After this single-end mixer,a subharmonical MESFET X-band
resistive mixer is made, the mixer LO-frequency is only half of
the RF frequency. The AM-LO noise is suppressed. A high
isolation is obtained intrinsically due to LO-cancellation. The
conversion loss is less than 11 dB from 9.5 Hz to 10.5 Hz.
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