High gamma compact harmonic tuner
View Patent ↗Compact, high Gamma, wideband, multi-carriage-multi-harmonic tuners use a meandering slabline structure and multiple probes and carriages. The meandering structure reduces the overall tuner length by more than half at 0.4 GHz. The required slabline bends are made using a vertical-to-horizontal slabline transition. Multiple probes are employed within the slabline segment closest to the test port, in order to minimize the insertion loss at higher frequencies, caused by the slabline bends. This tuner structure is mostly effective starting at fundamental frequencies below 1 GHz and operating at fundamental or harmonic frequencies as high as 18 GHz.
1. A multi-carriage slide screw impedance tuner comprising two ports, a test port and an idle port, and a slotted, meandering, low loss airline (slabline) between the ports,
whereby the slabline comprises three parallel straight sections, SL 1 to SL 3 and two “U” bends, U 1 and U 2 , the total forming an “S”;
and whereby U 1 connects SL 1 with SL 2 and U 2 connects SL 2 with SL 3 ;
and whereby SL 1 is attached to the test port and SL 3 to the idle port;
and five mobile carriages C 1 to C 5 , sliding independently along the axis of the straight slabline sections SL 1 to SL 3 , said carriages having vertically movable axes, each axis holding one reflective tuning probe (slug) P 1 to P 6 , said probes being vertically insertable into the slabline slot and capacitively coupled with the center conductor of the slabline,
whereby carriages C 1 to C 3 are mount on section SL 1 , carriage C 4 is mount on SL 2 and carriage C 5 on SL 3 ;
and whereby carriage C 1 is a double carriage comprising two independent vertical axes and carriages C 2 to C 5 are single carriages comprising one vertical axis each;
and whereby carriage C 1 controls a low frequency probe P 4 and a high frequency probe P 1 , carriages C 4 and C 5 control low frequency probes P 5 and P 6 and carriages C 2 and C 3 control high frequency probes P 2 and P 3 respectively.
2. A tuner as in claim 1 , whereby probes P 1 to P 3 are high frequency probes capable of creating high reflection between a frequency F 1 and the maximum frequency Fmax, and whereby probes P 4 to P 6 are low frequency probes capable of creating high reflection between a minimum frequency Fmin and a frequency F 2 ;
whereby Fmin is smaller than F 1 (Fmin <F 1 ), F 2 is larger than F 1 (F 2 >F 1 ) and Fmax is larger than F 2 (Fmax >F 2 ).
3. A tuner as in claim 2 , whereby the first slabline section SL 1 has a length of at least three times the width (LC) of the single mobile carriage, plus one time the width of the double carriage plus one half of the wavelength at the lowest frequency, λ/2(Fmin), and whereby the second and third sections SL 2 and SL 3 have a length of at least one half of the wavelength at the lowest frequency, λ/2(Fmin), plus the width (LC) of the single mobile carriage.
4. A tuner as in claim 3 whereby all carriages and vertical axes are remotely controlled using electric stepper motors, appropriate gear, electronic control boards and control software operated by an external PC controller.
5. A tuner as in claim 1 , whereby the slabline sections SL 1 to SL 3 comprise two vertical metallic walls and a center conductor;
and whereby the bends U 1 and U 2 comprise a center conductor and two lateral metallic walls, forming horizontal slabline sections, dimensioned in order to create the same characteristic impedance as the adjacent vertical straight slabline sections SL 1 to SL 3 , and
whereby the center conductor of bend U 1 joins the center conductors of SL 1 and SL 2 and the center conductor of U 2 joins the center conductors of SL 2 and SL 3 .
6. A tuner as in claim 5 whereby the characteristic impedances of the slablines SL 1 to SL 3 and bends U 1 and U 2 are 50 Ohms.