2011 S DARN W k h2011 SuperDARN Workshop2011 SuperDARN Workshop2011 SuperDARN WorkshopD t th C ll N H hi USADartmouth College, New Hampshire, USADartmouth College, New Hampshire, USA

May 30 June 3May 30 - June 3y

I d t hi f S DARN t A i d t h iImpedance matching for SuperDARN antennas: An improved techniqueImpedance matching for SuperDARN antennas: An improved techniqueImpedance matching for SuperDARN antennas: An improved techniquep g p p qCustovic E Elton D Devlin J Whittington J & Console ACustovic E., Elton D., Devlin J., Whittington J. & Console A.Custovic E., Elton D., Devlin J., Whittington J. & Console A.

Department of Electronic EngineeringDepartment of Electronic Engineeringp g g

Whil th h b i t i i d t hi i tWhile there has been an improvement in impedance matching in recentWhile there has been an improvement in impedance matching in recentd l t ll b d th f t id l t f This LC networked has been specifically designed for a 1 2kW system Thedevelopments, all are based on the use of toroidal transformers. This LC networked has been specifically designed for a 1.2kW system The

1800Ω 1p ,

prototype was tested with an 1800Ω termination and achieved a 1:5.5 VIn recent years we have witnessed the development of the Twin Terminated

prototype was tested with an 1800Ω termination and achieved a 1:5.5 Vt f ti L i it bl d d t iti i t dIn recent years we have witnessed the development of the Twin Terminated transfer ratio. Losses are inevitable and are due to parasitic resistance and

Folded Dipole (TTFD) Antenna which has replaced the deployment of thep

the skin effect and the dielectric loss of the FR4 PCBFolded Dipole (TTFD) Antenna which has replaced the deployment of theb lk d tl LPDA [1] N th l th TTFD i till k i

the skin effect and the dielectric loss of the FR4 PCB.bulky and costly LPDA [1]. Never the less, the TTFD is still a work inbulky and costly LPDA [1]. Never the less, the TTFD is still a work in

ith th S DARN it hi h i ti ll ti i i thprogress with the SuperDARN community which is continually optimising thep g p y y p goriginal design to extract maximum performance characteristics [2]original design to extract maximum performance characteristics [2].g g

Unlike an LPDA array where impedance does not vary excessively acrossUnlike an LPDA array where impedance does not vary excessively acrossthe 8-18 MHz bandwidth the TTFD’s performance is primarily handicapped Figure 4: TTFD balun enclosure on pole Figure 5: TTFD frequency dependence the 8 18 MHz bandwidth, the TTFD s performance is primarily handicappedb h f d d

g p g q y p

by a heavy frequency dependence.by a ea y eque cy depe de ceThis method of antenna matching is most effective when there is minimalThis method of antenna matching is most effective when there is minimali d i ti th d i d b d idth A i l i d iimpedance variation across the desired bandwidth. A nominal impedance is Figure 7. a) Top view of proposed system b) Side view of proposed systemp pchosen in this case 1800Ω and a 50Ω feeder line is matched through 6 turns

g ) p p p y ) p p y

chosen in this case 1800Ω and a 50Ω feeder line is matched through 6 turnsgof wire (√1800/50) around the toroid An ideal balun would see a 1:6 step upof wire (√1800/50) around the toroid. An ideal balun would see a 1:6 step-upin voltage but this is not the case due to loss in the ferrite core especiallyin voltage but this is not the case due to loss in the ferrite core especially

An improved technique for TTFD antenna matching has been demonstratedwhen working at higher powers Additionally this will work well only for the An improved technique for TTFD antenna matching has been demonstratedi LC t k i t d f t id l t f Thi t h i

when working at higher powers. Additionally this will work well only for thei l i d b t ill h i ifi tl di i i h d f f using an LC network instead of a toroidal transformer. This techniquesnominal impedance but will have significantly diminished performance for using an LC network instead of a toroidal transformer. This techniques

id i ifi tl l t d fl ibilit bli b tt t h t th hi hnominal impedance but will have significantly diminished performance for

th b f th l f d d f th TTFD (Fi 5) provides significantly elevated flexibility enabling a better match to the highothers because of the large frequency dependence of the TTFD (Figure 5). p g y y g gfrequency dependence of the TTFD

g q y p ( g )frequency dependence of the TTFD.y

Figure 1: LPDA model Figure 2: Frequency response of LPDAg g q y pSimulations conducted on the variation of impedance across each antenna

From Figure 2 we can see that the nominal impedance of the LPDASimulations conducted on the variation of impedance across each antenna

From Figure 2 we can see that the nominal impedance of the LPDA Having identified this shortcoming within the current system we believe that within the array are shown in Figure 8 For the development we plan to(Modified 608 model manufactured by Sabre Communications Corporation) Having identified this shortcoming within the current system we believe that within the array are shown in Figure 8. For the development we plan to

h i di id l t i d it t d l(Modified 608 model, manufactured by Sabre Communications Corporation) we can provide a better solution by using a matching LC network The LC measure each individual antenna impedance on site to produce a realvaries from 40 to 150 Ohms in the real domain and from 80 to -40 in the we can provide a better solution by using a matching LC network. The LC

k d i d i G hi h i l hi heasu e eac d dua a e a peda ce o s e o p oduce a ea

comparison to Fig re 8 This ill allo s to design a realistic impedancevaries from 40 to 150 Ohms in the real domain and from 80 to 40 in thei i d i C i f th ll f f th LPDA network was designed using Genesys which is a low-cost, high- comparison to Figure 8. This will allow us to design a realistic impedanceimaginary domain. Comparisons of the overall performance of the LPDA network was designed using Genesys which is a low cost, high

f i t t d l t i d i t ti ft fp g g p

model load which can then replace the 1800Ω load (Figure 6a) to test theimaginary domain. Comparisons of the overall performance of the LPDAd TTFD h b t di d f hil d it i l l id t th t performance integrated electronic design automation software for model load which can then replace the 1800Ω load (Figure 6a) to test the

and TTFD have been studied for a while and it is clearly evident that on p g gRF/microwave circuit board and subsystem designers circuit with With the aid of Genesys we will then optimise the LC network toy

average the LPDA has a slightly higher gain but significantly worse RF/microwave circuit board and subsystem designers. circuit with. With the aid of Genesys we will then optimise the LC network toaverage the LPDA has a slightly higher gain but significantly worse y g

match the realistic antenna impedance and in turn provide a more accurateg g y g g g ydirectivity The TIGER consortium is currently deploying its’ third RADAR

match the realistic antenna impedance and in turn provide a more accuratefdirectivity. The TIGER consortium is currently deploying its third RADAR 50Ω coaxial cable is wound approx 13 times around a plastic former solution. The result will be an individual match for each antenna within the

(Buckland Park Adelaide) and has developed a completely digital based 50Ω coaxial cable is wound approx 13 times around a plastic former solution. The result will be an individual match for each antenna within the(Buckland Park, Adelaide) and has developed a completely digital based (110mm diameter) (Figure 7 a & b) to form a 50Ω unbalanced to 50Ω arraytransceiver which could potentially improve the system’s signal to noise ratio (110mm diameter) (Figure 7 a & b) to form a 50Ω unbalanced to 50Ω

b l d t f Thi t f th f d th t hi t ky

transceiver which could potentially improve the system s signal to noise ratiot 60dB [3] T th t i i b fit f th balanced transformer. This transformer then feeds the matching networkup to 60dB [3]. To ensure that we gain maximum benefit from the new balanced transformer. This transformer then feeds the matching networkup to 60d [3] o e su e t at e ga a u be e t o t e e

h d it i t l i t t t thhardware it is extremely important to ensure there are no unnecessaryy p ylosses throughout the system in particular at the filtering matching antennalosses throughout the system, in particular at the filtering, matching antennastagesstages.

C tl th l t d S DARN t hi h Figure 8: Impedance variation amongst antennas in arrayCurrently there are almost a dozen SuperDARN antenna arrays which are Figure 8: Impedance variation amongst antennas in arrayy p yutilising the TTFD antennas where each main array consists of 16 antennasutilising the TTFD antennas where each main array consists of 16 antennasg yas shown in Figures 3 & 4as shown in Figures 3 & 4.

[1] Custovic E Devlin J Whittington J Console A “Three-wire Twin Terminated Folded[1] Custovic, E., Devlin, J., Whittington, J., Console, A., Three-wire Twin Terminated FoldedDi l f S DARN R d ” P di f 12th A t li S iDipole array for SuperDARN Radars”, Proceedings of 12th Australian Symposium onFigure 6: a) 25Ω to 900Ω schematic from Genesys b) Frequency response of LC network p y p , g y pAntennas pp 33 34 Sydney Australia 16 17 Feb 2011

Figure 6: a) 25Ω to 900Ω schematic from Genesys b) Frequency response of LC networkAntennas, pp 33-34, Sydney, Australia, 16 - 17 Feb. 2011

The feed matching network has two identical sides as shown in Figure 7b.The feed matching network has two identical sides as shown in Figure 7b.[2] Custovic E and Console A “TTFD Array Variations for TIGER 3” InternationalThe shield of the coaxial cable is attached to the ground on the PCB The [2] Custovic, E., and Console, A. TTFD Array Variations for TIGER 3 ,InternationalThe shield of the coaxial cable is attached to the ground on the PCB. The SuperDARN Conference Proceedings Hermanus South Africa June 2010

benefit of this is that there is significantly less stress on the capacitorsSuperDARN Conference Proceedings, Hermanus, South Africa, June 2010

benefit of this is that there is significantly less stress on the capacitors( lt ) d lth h i d t i d th i i i d d(voltage) and although more inductors are required their size is reduced [3] Devlin J Whittington J Elton D Console A Custovic E Nguyen H(voltage) and although more inductors are required their size is reducedd ti ll It b f Fi 6b th t th f th LC i it

[3] Devlin, J., Whittington, J., Elton, D., Console, A., Custovic, E., Nguyen, H., K l kk K B i A G til M W S d N M “U d t TIGER 3drastically. It can be seen from Figure 6b that the response of the LC circuit Kamalakkannan, K., Borgio, A., Gentile, M., Wang, S., and Nguyen, M. “Update on TIGER-3 y g p

is more than adequate for the 8 18MHz band Capacitors are etched on, , g , , , , g, , g y , p

Hardware Development” International SuperDARN Conference Proceedings Hermanusis more than adequate for the 8-18MHz band. Capacitors are etched on Hardware Development , International SuperDARN Conference Proceedings, Hermanus, custom designed FR4 PCB and have approximate 1% tolerance while South Africa, June 2010custom designed FR4 PCB and have approximate 1% tolerance while ,

Inductors are wound on ABS plastic bobbins (aircore) which allows creationInductors are wound on ABS plastic bobbins (aircore) which allows creation Thanks to Mick Parsons (Department of Physics & Astronomy, Leicester University) forFi 3 M i d ili (TIGER 3) of a wide range of inductor values.Thanks to Mick Parsons (Department of Physics & Astronomy, Leicester University) forproviding the LPDA model

Figure 3: Main array and auxiliary array (TIGER 3) of a wide range of inductor values. providing the LPDA model