High Current RF-testing ing . R.O. de Meijer AR Benelux BV

1. High Current RF-testinging. R.O. de MeijerAR Benelux BV HF Technology, Eindhoven, April 2012

2. Customer’s target • Testing of RF-current breakdown levels for currents > 50A rms • Improvement of quality and reliability of the product. • Not all the customer’s suppliers specify these breakdowns. • Perform the testing in-house, as part of the design cycle and QA program HF Technology, Eindhoven, April 2012

3. Customer’s target (cntd) • Various components: • Connects • Capacitors • PIN diode switches • Preferably making use of the customer’s amplifiers • Pulse with 30 kW peak power @ 3% duty • 63 and 127 MHz HF Technology, Eindhoven, April 2012

4. Problem definition • RF amplifiers have 50Ω output impedance • Because 50Ω is not low, the maximum deliverable current will not be high • In case of Pout = 30 kWatt into 50 Ohm HF Technology, Eindhoven, April 2012

5. Enlarging the current • With a constant power level the only option is lowring the impedance in the test cicrcuit. • Transformation from 50Ωto 5Ω • The implication for the current now flowing through 5Ω is • This complies to the customer’s spcification HF Technology, Eindhoven, April 2012

6. Impedance transformation • With 30kW pulse and 3% duty cycle  Pavg ~ 1kW • Low-loss transformation is a must. • Loss less transformation with a ¼λ coaxial transformer • Two operational frequencies • 63 MHz λ = 4m75 • 127 MHz λ = 2m36 Ztr 5Ω 50Ω 30kW LOAD • L= λ/4 HF Technology, Eindhoven, April 2012

7. ¼ λ coaxial transformer • Coaxial cables with this characteristic impedance is not easily available • The impedance of a coaxial line • D = diameter outer conducter • d = diameter inner conducter • εr = rel. dielectrical constant HF Technology, Eindhoven, April 2012

8. Creation of the ¼λ coaxial transformer • Brass pipes with 17 and 13 mm diameter • Make up a Z0 of 16Ω • Two models, 63 MHz and 127 MHz 127 MHz 63 MHz HF Technology, Eindhoven, April 2012

9. The transformed impedance on the Smith-Chart 5Ω 50Ω HF Technology, Eindhoven, April 2012

10. Test set-up L 15.8Ω 5Ω 50Ω EUT BOX 5Ω 1 kW HF Technology, Eindhoven, April 2012

11. 1 kWatt 5Ω load The 5Ωpoint 20 x 100Ω parallel HF Technology, Eindhoven, April 2012

12. Unwanted effetcs in the set-up • Electrical lengths inside the EUT box • Zload = R + jωL • The ¼ λtransformator will not supply 50Ω to the amplifier. HF Technology, Eindhoven, April 2012

13. Solution (theoretical) HF Technology, Eindhoven, April 2012

14. The solution (practical) Stub-tuner detail 2 x 50Ω stub-tuner HF Technology, Eindhoven, April 2012

15. Conclusion • All transmission lines have air-dielectricum, with de εr = 1 • No dielectrical losses. • With the ¼ golf transmission line and the supporting stub tuners all paracitic effects in the EUT box are eliminated. • The amplifier ‘sees’ under all conditions 50 Ω • Full power available for the ‘destructive’ test HF Technology, Eindhoven, April 2012

16. More information AR Benelux B.V. Frankrijklaan 7 2391 PX HAZERSWOUDE-DORP Telefoon : +31 (0)172 423000 Web-site : www.arbenelux.com E-mail : arbeneluxinfo@arworld.us HF Technology, Eindhoven, April 2012