1. High Temperature Superconductor Filters for Sardinia Radio Telescope
INTRODUCTION Why a Filter?
HTS FILTRES The Process
HTS FILTERS Examples
NEXT STEPS
CONCLUSIONS
P. Bolli1, L. Cresci1, F. Huang2, S. Mariotti D. Panella1
INAF-Osservatorio Astrofisico di Arcetri – Firenze - ITALY
School of EECE, University of Birmingham, Edgbaston, Birmingham UK
INAF-Istituto di Radioastronomia – Bologna ITALY
Detection and measurement of RFI on radio astronomy – Yebes 8-9 June 2017

2. INTRODUCTION Why a Filter? HTS FILTRES The Process
Given a radio receiver chain, in order to reject RFI, a band pass filter and/or a notch may be placed just after LNA.
After LNA with typical Gain 35…40 dB, the increase of Tsys is negligible.
INTRODUCTION Why a Filter?
HTS FILTRES The Process
HTS FILTERS Examples
NEXT STEPS
CONCLUSIONS
Usually RFI became dangerous for receiver linearity at the end of the chain (mixer, IF Amp, final stage).
RFI is every time blinding, but if linearity will be affected, even the software mitigation will fails.
So, why a front-end filter?
Detection and measurement of RFI on radio astronomy – Yebes 8-9 June 2017

3. INTRODUCTION Why a Filter? HTS FILTRES The Process
The new frontier of RA calls for large bandwidth (1octave) or very large, as the case of BRAND-EVN ( 1 decade).
INTRODUCTION Why a Filter?
HTS FILTRES The Process
HTS FILTERS Examples
NEXT STEPS
CONCLUSIONS
For many years, usual and common LNA had a Po1 ~+5 dBm. An emerging brand sells excellent LNA but with Po1 ~ -12 dBm (C-band)
Given this conditions, if radar(s) or strong source(s) are located near the Radiotelescope, the risk of non linearity distortion will affect the LNA too.
For this reasons a front-end filter may help
Detection and measurement of RFI on radio astronomy – Yebes 8-9 June 2017

4. INTRODUCTION Why a Filter? HTS FILTRES The Process
FILTER REQUIREMENTS
The loss of the filter must not increase significantly the Noise Temperature.
INTRODUCTION Why a Filter?
HTS FILTRES The Process
HTS FILTERS Examples
NEXT STEPS
CONCLUSIONS
This mean the loss and the mismatch of the filter should be the lower as possible and Tsys still remain competitive.
|s21| and |s12| : the lowest possible |s11| and |s22| : the lowest possible
Detection and measurement of RFI on radio astronomy – Yebes 8-9 June 2017

5. HTS Filters appeared immediately as the best technological solution.
ON THE FILTER LOSS
HTS Filters appeared immediately as the best technological solution.
Due to the extremely low loss, HTS Filter has been used as narrow band Filters. For such applications the low loss performances cannot be overcome.
INTRODUCTION Why a Filter?
HTS FILTRES The Process
HTS FILTERS Examples
NEXT STEPS
CONCLUSIONS
Even more, with wide band, we expect an extremely low loss.
LF (intedigital, 20K) ≈ P Band LF (HTS, 20K) ≈ P Band (due to MgO substrate – estimated value)
Filter Loss
[ dB ]
Tsys w/o filter
[ K ]
Tsys with filter
0.05 5
5.3 15
15.4
0.10
5.6
15.8
0.15
5.9
16.2
0.20
6.2
16.6
0.25
6.5
17.1
Detection and measurement of RFI on radio astronomy – Yebes 8-9 June 2017

6. INTRODUCTION Why a Filter? HTS FILTRES The Process
THE FILTER
Filter Design
HTS furnisher
INTRODUCTION Why a Filter?
HTS FILTRES The Process
HTS FILTERS Examples
NEXT STEPS
CONCLUSIONS
Ti alloy Milling
Layout Optimization
Ti alloy house drawing
Assembly and Test & measurement
Ti alloy plating
Detection and measurement of RFI on radio astronomy – Yebes 8-9 June 2017

7. INTRODUCTION Why a Filter? HTS FILTRES The Process
HST STRUCTURE
Ion Beam Milling
GOLD mm
HTS (YBCO) mm
MgO Dielectric mm
GOLD mm
INTRODUCTION Why a Filter?
HTS FILTRES The Process
HTS FILTERS Examples
NEXT STEPS
CONCLUSIONS
Detection and measurement of RFI on radio astronomy – Yebes 8-9 June 2017

8. INTRODUCTION Why a Filter? HTS FILTRES The Process
HST DESIGN
INTRODUCTION Why a Filter?
HTS FILTRES The Process
HTS FILTERS Examples
NEXT STEPS
CONCLUSIONS
The filter may be band pass, low pass, high pass, notch or a combination of them
The synthesis is based on original circuital solutions and layout geometry
coming from the long experience of Lancaster’s group at Birmingham University.
More deeply, the design method is based on coupling coefficients of intercoupled resonators and the external quality factors of the input and output resonators.
Later , the geometry is fine tuned and analysed with Sonnet EM simulator
Detection and measurement of RFI on radio astronomy – Yebes 8-9 June 2017

9. INTRODUCTION Why a Filter? HTS FILTRES The Process
HST DESIGN
The housing should firmly host the PCB.
Excellent electrical contacts on both central pin and GND is required
The mechanical design must be robust against differential of Coeff. Of Thermal Expansion
INTRODUCTION Why a Filter?
HTS FILTRES The Process
HTS FILTERS Examples
NEXT STEPS
CONCLUSIONS
Ti6 Al4 V is the alloy that match the CTE of MgO, both at room temperature and in cryogenic environment.
In order to better match the CTE, a “gummous” epoxy is used. The Henkek Ablefilm 5025E – 4 mils is an electrical conductive, gommous, double-sided adhesive tape.
Detection and measurement of RFI on radio astronomy – Yebes 8-9 June 2017

10. INTRODUCTION Why a Filter? HTS FILTRES The Process
HST: ASSEMLING PHASE
INTRODUCTION Why a Filter?
HTS FILTRES The Process
HTS FILTERS Examples
NEXT STEPS
CONCLUSIONS
HTS C-Band : Assembling phase
Detection and measurement of RFI on radio astronomy – Yebes 8-9 June 2017

11. INTRODUCTION Why a Filter? HTS FILTRES The Process
HST TEST & MEASUREMENT
Test & Measurement were made in parallel in two laboratories, Florence and Bologna
Bologna Lab.
Florence Lab.
VNA 
cryogenic full 2 port calibration under refinement
full 2 port calibration at room temperature, then correction of the cold path in post-processing. LOW DRIFT
SNA
good for fast test, but less accurate
Radiometric Noise
Possible but complicated and not more accurate than VNA
INTRODUCTION Why a Filter?
HTS FILTRES The Process
HTS FILTERS Examples
NEXT STEPS
CONCLUSIONS
Detection and measurement of RFI on radio astronomy – Yebes 8-9 June 2017

12. Cavity filter tested on liq. N2
T&M of FILTERS
Cavity filter tested on liq. N2
INTRODUCTION Why a Filter?
HTS FILTRES The Process
HTS FILTERS Examples
NEXT STEPS
CONCLUSIONS
HTS C-Band : Cryostat measurement
Detection and measurement of RFI on radio astronomy – Yebes 8-9 June 2017

13. INTRODUCTION Why a Filter? HTS FILTRES The Process
T&M of FILTERS
INTRODUCTION Why a Filter?
HTS FILTRES The Process
HTS FILTERS Examples
NEXT STEPS
CONCLUSIONS
HTS C-Band : Noise temperature method
Detection and measurement of RFI on radio astronomy – Yebes 8-9 June 2017

14. INTRODUCTION Why a Filter? HTS FILTRES The Process
THE FILTERS INSTALLED
P-Band (VHF) HTS Filter
On prime focus receiver
INTRODUCTION Why a Filter?
HTS FILTRES The Process
HTS FILTERS Examples
NEXT STEPS
CONCLUSIONS
C-Band (5 GHz) HTS Filter
On Gregorian receiver
Detection and measurement of RFI on radio astronomy – Yebes 8-9 June 2017

15. INTRODUCTION Why a Filter? HTS FILTRES The Process
THE FILTERS INSTALLED
INTRODUCTION Why a Filter?
HTS FILTRES The Process
HTS FILTERS Examples
NEXT STEPS
CONCLUSIONS
P-Band ( MHz)
Detection and measurement of RFI on radio astronomy – Yebes 8-9 June 2017

16. INTRODUCTION Why a Filter? HTS FILTRES The Process
THE FILTERS INSTALLED
INTRODUCTION Why a Filter?
HTS FILTRES The Process
HTS FILTERS Examples
NEXT STEPS
CONCLUSIONS
P-Band ( MHz)
Detection and measurement of RFI on radio astronomy – Yebes 8-9 June 2017

17. INTRODUCTION Why a Filter? HTS FILTRES The Process
THE FILTERS BUILD
INTRODUCTION Why a Filter?
HTS FILTRES The Process
HTS FILTERS Examples
NEXT STEPS
CONCLUSIONS
C-Band (7 GHz) HTS Filters
Detection and measurement of RFI on radio astronomy – Yebes 8-9 June 2017

18. INTRODUCTION Why a Filter? HTS FILTRES The Process
THE FILTERS BUILD
INTRODUCTION Why a Filter?
HTS FILTRES The Process
HTS FILTERS Examples
NEXT STEPS
CONCLUSIONS
C-Band (7 GHz) HTS Filter
Detection and measurement of RFI on radio astronomy – Yebes 8-9 June 2017

19. INTRODUCTION Why a Filter? HTS FILTRES The Process
RECENT JOB
INTRODUCTION Why a Filter?
HTS FILTRES The Process
HTS FILTERS Examples
NEXT STEPS
CONCLUSIONS
C-Band, 4.3…5.8GHz for SRT
S-Band, 2.20…2.38 GHz credits: Jose A. Lopez-Perez Pablo García Carreño
Yebes Observatory
7 poles + notch
9 poles
Detection and measurement of RFI on radio astronomy – Yebes 8-9 June 2017

20. INTRODUCTION Why a Filter? HTS FILTRES The Process
THE FILTERS BUILD
INTRODUCTION Why a Filter?
HTS FILTRES The Process
HTS FILTERS Examples
NEXT STEPS
CONCLUSIONS
Detection and measurement of RFI on radio astronomy – Yebes 8-9 June 2017

21. INTRODUCTION Why a Filter? HTS FILTRES The Process
HTS FILTRERS PRO vs CONS
PRO
CONS
reliability
P-band is working on SRT since 3 years
only cold
It works only if the receiver is cooled
non microfonic
While the cavity filter can be. 
not of the shelf
Require in house development and expertise. Is it really a CONS or it is an opportunity to join international collaborations?
Small dimension
Due to er as high as Small dimension means small mass. Non impact on cool down time. 
cost
a 2” wafer costs 4500€ € mechanical and plating + assembly and T&M
low loss
lowest loss technology known
replicability
high
INTRODUCTION Why a Filter?
HTS FILTRES The Process
HTS FILTERS Examples
NEXT STEPS
CONCLUSIONS
Detection and measurement of RFI on radio astronomy – Yebes 8-9 June 2017

22. INTRODUCTION Why a Filter? HTS FILTRES The Process
FOUND PROBLEMS LESSON LEARNED
Loss is dominated by connectors body and pin joint. Loss of K connector is higher than SMA connector,
But SMA central tab tend to pull and crack the epoxy.
Consequently, K connector has been adopted.
INTRODUCTION Why a Filter?
HTS FILTRES The Process
HTS FILTERS Examples
NEXT STEPS
CONCLUSIONS
Ti alloy is hard and difficult to machine, especially threathed holes.
But a good mechanical workshop has been found. X
The plating of Ti alloy is extremely difficult.
Not easy find a galvanic plant. But found
For these reasons Ti alloy is a critical issue, we experimented also copper instead but the PCB cracks due to high DCTE
Detection and measurement of RFI on radio astronomy – Yebes 8-9 June 2017

23. INTRODUCTION Why a Filter? HTS FILTRES The Process
NEXT STEPS / CONCLUSIONS
Reflection coefficient does not match the simulated one. Need to understand why.
The loss of the connector body cannot be lowered. But the contact to microstrip can be. Bond-wires / ribbon against epoxy.
INTRODUCTION Why a Filter?
HTS FILTRES The Process
HTS FILTERS Examples
NEXT STEPS
CONCLUSIONS
More challenging solution: Integration of the HTS Filter and LNA in the same house.
Reconsider traditional metals as housing. Maybe drawing solutions can compensate the stress
More accurate / advanced VNA error correction techniques
Sincere (and not rhetoric) thanks to the SOC and the LOC for excellent organization.
Thanks to for the partial support to the travel
Detection and measurement of RFI on radio astronomy – Yebes 8-9 June 2017