Frequency adjustable pre-matching coaxial transistor test fixture
View Patent ↗Coaxial microwave transistor test fixtures provide lowest insertion loss possible and include, as part of the input and output sections, transformer networks in form of single stage λ/4 segments bringing (pre-matching) the system 50 Ω load closer to the conjugate internal impedance of power transistors. The transforming networks are flat, cylindrical or have oval or elliptical cross sections and have adjustable length, thus operating optimally for transistors with varying optimum frequency and internal impedance and/or capacitive or inductive impedance part. The change in length is done without affecting the overall fixture geometry and structure. The fixtures can be calibrated using standard TRL method.
1. A frequency adjustable, coaxial, pre-matching RF transistor (DUT) test fixture comprising
an input section attached to input port,
an output section attached to output port,
a metallic block (INSERT) inserted between the sections, which said INSERT carries the DUT, and
a metallic cover extending from the input port to the output port,
whereby
the input section and the output section form sections of slablines, each comprising
a bottom metallic block,
sections of the metallic cover,
coaxial connector associated with the corresponding port, and
center conductor attached to the connector and reaching from the connector to the INSERT,
and whereby
at least one of the center conductors comprises a 50Ω segment and a non-50Ω segment, whereby the non-50Ω segment is inserted between the 50Ω segment and the DUT,
and whereby
the axial physical length of the non-50Ω segment is adjustable,
and whereby
the minimum axial physical length of the non-50Ω segment is one quarter wavelength (λ/4) at the highest resonance frequency.
2. The test fixture of claim 1 ,
whereby
at least one non-50Ω segment comprises a hollow fixed part and a solid mobile part,
and whereby
the fixed part comprises an axial cavity open towards the mobile part,
and whereby
the mobile part slides on the center conductor and enters into the cavity of the fixed part,
and whereby
the center conductor is attached on one side to the coaxial connector and on the other side to the bottom of the cavity of the fixed part,
and whereby
the fixed part is attached to the DUT and the mobile part is closest to the connector, and whereby
the axial length of the fixed part is λ/4 at the highest resonance frequency and the mobile part fits entirely into the cavity of the fixed part.
3. The test fixture of claim 1 or 2 ,
whereby
the fixed and mobile parts of the at least one non-50Ω segment are parallelepipeds,
and whereby
the fixed part is hollow and the mobile part is solid.
4. The test fixture of claim 1 or 2 ,
whereby
the fixed and mobile parts of the at least one non-50Ω segment are co-axial cylinders,
and whereby
the fixed part is hollow and the mobile part is solid.
5. The test fixture of claim 1 or 2 ,
whereby
the fixed and mobile parts of the at least one non-50Ω segment are co-axial ellipsoids,
and whereby
the fixed part is hollow and the mobile part is solid.
6. The test fixture of claim 1 , whereby at least one non-50Ω segment is exchangeable.