22ghz mmic low noise amplifier. housing em analysis and ... · 22ghz mmic low noise amplifier....
TRANSCRIPT
InP CSR17
Printing Date: Thursday, 18 February 2010 File Location: D:\Documenti\ATTIVITA'\LNA\CSR17\Docs\22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for cavity resonances.doc
TITLE:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for cavity resonances
DOC. TYPE:
DESIGN REPORT DOC. REF. : IRA 434/10
PROJECT REF. :
InP CSR17 PAGE: 41
ISSUE/REV.: 1.0 DATE: 18 Feb 2010
Prepared by
Cremonini Andrea
Date:
Signature:
Dec 10, 20008 _______________________
Revised by
Alessandro Orfei
Renzo Nesti
Date:
Signature:
February 18,2010 _______________________
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 2/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
DISTRIBUTION LIST
RECIPIENT AFFILIATION E-MAIL ADDRESS N° Copies
A .ORFEI IRA [email protected] 1 S. MARIOTTI IRA [email protected] 1 R. NESTI IRA [email protected] 1 A. NAVARRINI OAC [email protected] 1 A. CREMONINI IRA [email protected] 1
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 3/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
CHANGE RECORD
ISSUE DATE SHEET DESCRIPTION RELEASE 1.0 ALL First issue of document ==
1.1 1.2
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 4/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
APPLICABLE DOCUMENTS
REF. CODE TITLE RELEASE
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 5/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
Index
1 - Introduction .................................................................................................................................... 8 2 - Executive summary ........................................................................................................................ 8 3 - Scenario Description ....................................................................................................................... 9 4 - EM Simulation activity: prologue and final results ...................................................................... 13 5 - Study of different strategies in order to modify the cavity propagation ....................................... 16 6 - When a solution hide a mistake .................................................................................................... 35 7 - And the winner is..... .................................................................................................................... 40
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 6/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
Figure Index
Fig.1 – Assembled 22GHz LNA .......................................................................................................... 9 Fig.2 – MMIC Noise characterization ................................................................................................. 9 Fig.3 – LNA Characterization @290K .............................................................................................. 10 Fig.4 – LNA Characterization @20K ................................................................................................ 10 Fig.5 – LNA Multifeed Receiver Noise ............................................................................................. 11 Fig.6 – LNAs Input matching ............................................................................................................ 11 Fig.7 - carrier 22 GHz – Measurement scenario ................................................................................ 12 Fig.8 - S21 measurement between RFin e RFout with cap (light green) and without cap (dark green)
................................................................................................................................................ 12 Fig.9 – CST Simulation - Open Carrier ............................................................................................. 13 Fig.10 – CST Simulation - Carrier with flat cap (present state) ........................................................ 13 Fig.11 – 26 GHz E-field with flat cap ................................................................................................ 14 Fig.12 – 26 GHz H-field with flat cap ............................................................................................... 14 Fig.13 – Preferred CAP Version with short diagonal septum and 0.8 mm recessed ceiling ............. 15 Fig.14 – Frequency response related to Fig. 8 configuration............................................................. 15 Fig.15 – cap with small baffle ............................................................................................................ 16 Fig.16 – Frequency response related to Fig. 15 configuration........................................................... 17 Fig.17 – cap with forwarded small baffle .......................................................................................... 17 Fig.18 – Frequency response related to Fig. 17 configuration........................................................... 17 Fig.19 – cap with more forwarded small baffle ................................................................................. 18 Fig.20 – Frequency response related to Fig. 19 configuration........................................................... 18 Fig.21 – cap of fig.19 and a mirror-like one on RF OUT .................................................................. 19 Fig.22 – Frequency response related to Fig. 21 configuration........................................................... 19 Fig.23 – cap of fig.19 with reduced thickness ................................................................................... 20 Fig.24 – Frequency response related to Fig. 23 configuration........................................................... 20 Fig.25 –Big septum near RF in connector post .................................................................................. 21 Fig.26 – Frequency response related to Fig. 25 configuration........................................................... 21 Fig.27 –Two Big septum near RF in connector post ......................................................................... 22 Fig.28 – Frequency response related to Fig. 27 configuration........................................................... 22 Fig.29 – RFIn shielded ....................................................................................................................... 23 Fig.30 – Frequency response related to Fig. 29 configuration........................................................... 23 Fig. 31 – RFIn and RFOut shielded ................................................................................................... 24 Fig.32 – Frequency response related to Fig. 31 configuration........................................................... 24 Fig.33 – RFIn and RFOut shielded (RFOut shield raised up) ......................................................... 25 Fig.34 – Frequency response related to Fig. 33 configuration........................................................... 25 Fig.35 – Diagonal baffle input and septum to RF Out ....................................................................... 26
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 7/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
Fig.36 – Frequency response related to Fig. 37 configuration........................................................... 26 Fig.37 – Two Diagonal baffles input and septum to RF Out ............................................................. 27 Fig.38 – Frequency response related to Fig. 37 configuration .......................................................... 27 Fig.39 – Three Diagonal baffles ........................................................................................................ 28 Fig.40 – Frequency response related to Fig. 39 configuration........................................................... 28 Fig.41 – Four Diagonal baffles .......................................................................................................... 29 Fig.42 – Frequency response related to Fig. 41 configuration........................................................... 29 Fig.43 – Four Diagonal smoothed baffles .......................................................................................... 30 Fig.44 – Frequency response related to Fig. 43 configuration.......................................................... 30 Fig.45 – Four Diagonal smoothed moved back baffles ..................................................................... 31 Fig.46 – Frequency response related to Fig. 45 configuration........................................................... 31 Fig.47 – Two big reflectors over the microstrips ............................................................................... 32 Fig.48 – Frequency response related to Fig. 47 configuration........................................................... 32 Fig.49 – We add a metal ring at the RFIn to the fig 47 configuration: RF Input connector post
shielded ................................................................................................................................ 33 Fig.50 – Frequency response related to Fig. 49 configuration........................................................... 33 Fig.51 – We add a metal ring also at the RF Output: RF Input and RF Output connector post
shielded ................................................................................................................................ 34 Fig.52 – Frequency response related to Fig. 51 configuration.......................................................... 34 Fig.53 – four diagonal septum flat caps ............................................................................................. 35 Fig.54 – CST Frequency response related to Fig. 53 configuration .................................................. 35 Fig.55 – HFSS Simulation of fig. 53 0.5 GHz Resolution ................................................................ 36 Fig.56 – HFSS Simulation of fig. 53 0.2 GHz Resolution ................................................................ 36 Fig.57 – HFSS Simulation of fig. 49 0.1 GHz Resolution ................................................................ 37 Fig.58 – Cap with diagonal septum and estruses ceiling ................................................................... 37 Fig.59 – Frequency response related to Fig. 58 configuration........................................................... 38 Fig.60 – Frequency response related to Fig. 58 configuration........................................................... 38 Fig.61 – Cap with diagonal septum and recessed ceiling .................................................................. 39 Fig.62 – Frequency response related to Fig. 60 configuration........................................................... 39 Fig.63 – Frequency response related to Fig. 60 configuration........................................................... 40 Fig. 64 – diagonal “short” baffle 0.8 mm recessed CAP preferred version ....................................... 41 Fig. 65 – Frequency response related to Fig. 60 configuration .......................................................... 41
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 8/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
1 - Introduction
In order to build state of the art Cryogenic receiver for Radioastronomical applications, our institute has been involved in a R&D activity programme. Its paramount aim was to exploit MMIC InP technology, designing and realising competitive extremely low noise amplifiers. For such devices not only the RF design has to be considered as crucial. MMIC housing and assembly method are crucial phases of the production chain which can deadly waste the RF design effort. In this report, EM cavity effects are considered. When the carrier was designed, we hadn’t the opportunity to simulate housing cavity EM behaviour. Only during the characterisation activity we discover a cavity housing tendency to resonate within the working frequency range. Aim of this activity is find a solution to oscillation which stand out when the MMIC LNA 22LNA_05A housed in a custom designed carrier is powered on with the cap on. Because 14 LNA have been already packaged and mounted inside the cryostat of the new 22GHz multifeed receiver installed in Medicina, the only possible solution, if we want avoid microwave absorber inside the housing cavity, is to operate on the cap shape, in order to reduce the propagation tendency in the 18-26GHz frequency range. At present the cavity shape cause oscillation tendency. From measurements it’s clear that’s a noise figure rise exactly at those frequencies. The same behaviour wasn’t highlighted when on chip measurements were performed. Those elements focus our attention on the carrier.
2 - Executive summary
As reported in chapter 3, we compared noise performances measured of warm MMIC and Packaged cold and warm LNA. Is clearly described by data reported how much the package increase the noise floor and introduce a rising slope noise in the upper end of the working frequency band. Consequently, the housing EM behaviour has been measured and results are reported in fig.8. Then, 3D simulator has been adopted in order to find a possible solution. We imported in CST (the 3DEM simulator) the IGES file provided by mechanical designer, which contains carrier walls information. Next, we extruded the microstrip layers described in the GDS file imported from Microwave Office (the RF simulator). We built the coaxial wall through according to the physical dimension reported in connector datasheets. Then we assigned RF ports and start to try configurations in order to decouple input and output. We initially try to obtain with the simulator results comparable with the measurements. Then we worked on the cap shape in order to modify the cavity behaviour. In chapter 5 all trials are reported and in chapter 4 the best configuration, which reduce the resonance tendency in the working bandwidth, is widely described.
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 9/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
3 - Scenario Description
. In fig. 1 assembled LNA is presented. In the middle is visible the MMIC. Its noise response is represented in fig. 2. Wire and passive components in the upper side of the carrier are drain bias lines. Gate bias lines are in the bottom side of the carrier. Every MMIC stage is independently tuneable then separate bias lines are necessary. RF in is on the left (K connector) RF out is on the right (also K connector)
Fig.1 – Assembled 22GHz LNA
Fig 2 shows MMIC characterization performed with different accuracy level, compared with MMIC simulation. Noise contribution can be defined around 90K
Noise Performances 4245-020 22LNA_05A
60
100
140
180
220
260
15,5
16,5
17,5
18,5
19,5
20,5
21,5
22,5
23,5
24,5
25,5
26,5
Frequency [GHz]
T e [K
]
050201 050201 High Accuracy Simulated
Fig.2 – MMIC Noise characterization
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 10/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
As previously announced, packaging and assembling are activities which introduce a relevant quantity of noise and waste the upper end of the working bandwidth as reported in fig 3.
Fig.3 – LNA Characterization @290K
Effect on the noise floor are consistently reduced at 20K (fig 4) where the excess noise introduced by the package can be estimated in a few Kelvin, but the rising slope tendency remains.
Fig.4 – LNA Characterization @20K
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 11/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
In Fig 5 channels noise of a 22GHz multifeed receiver are shown. It is clear that it is dominated by the LNA. Comparing it with the input match described in fig. 6 is evident that the noise peak corresponds to a worst input matching condition. The matching is certainly a cause of a noise peak but it could also depend by what happen inside the cavity by the electromagnetic point of view.
Fig.5 – LNA Multifeed Receiver Noise
Fig.6 – LNAs Input matching
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 12/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
As already expressed before, the closed package behaves like a resonant cavity. Two connector’s posts welded to the microstrips act like a probe launchers. Due to their physical dimensions, they can’t launch fundamental modes but inside the cavity, higher order modes primes resonances. In order to test the house behaviour, transmission response S21, with only the microstrip and connector feedthrough has been measured, as showed in fig.7
Fig.7 - carrier 22 GHz – Measurement scenario Measurements are reported in Fig. 8 where the dark green trace represents the transmission response when the cap is open. Light green line report the transmission characteristic when the cap is on the MMIC house.
Fig.8 - S21 measurement between RFin e RFout with cap (light green) and without cap (dark green)
It’s obvious the transmission tendency around 26 GHz (dark green line). This behaviour results emphasized when the box is closed (light green line).
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 13/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
4 - EM Simulation activity: prologue and final results
With CST, we rebuilt the cavity and open and close situations have been simulated. Consistently with a rough reality reconstruction, the simulator has provided comparable measurements results, showed in fig. 4 and fig. 5. As remark consider the two transmission responses S21 and S12 (green and blue lines). They are different, but it can’t be possible because the measured element is reciprocal and theoretically they must appear identical. Since S11,S21 and S22,S12 are obtained by different simulations but adaptive meshing is calculated only for one of them, numerical errors are possible. More evidence of this effect can be noted in chapter 5.
Fig.9 – CST Simulation - Open Carrier
Fig.10 – CST Simulation - Carrier with flat cap (present state)
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 14/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
Fig.11 – 26 GHz E-field with flat cap
Fig.12 – 26 GHz H-field with flat cap After several tentative, which will be illustrated in the chapter 5, we have defined a house cap with mechanical characteristic that seems to reduce the propagation inside the LNA cavity. The preferred topology has 4 diagonal septum which across the cavity and a 0.8 mm recessed area over the RF part of the cavity (fig. 13). Simulation in fig. 14 shows the cavity behaviour corrected by the shaped cap.
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 15/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
Fig.13 – Preferred CAP Version with short diagonal septum and 0.8 mm recessed ceiling
In order to verify that m2, m3, m4 resonances aren’t numerical spurious responses, several simulation has been performed between 15 to 21 GHz (described by dotted lines).
10.00 11.00 12.00 13.00 14.00 15.00 16.00 17.00 18.00 19.00 20.00 21.00 22.00 23.00 24.00 25.00 26.00 27.00 28.00 29.00 30.00 31.00 32.00 33.00 34.00 35.00 36.00 37.00 38.00 39.00 40.00Freq [GHz]
-120.00
-110.00
-100.00
-90.00
-80.00
-70.00
-60.00
-50.00
-40.00
-30.00
-20.00
-10.00
0.00
Y1
Ansoft Corporation HFSSDesign1Short Diagonal Septum CAP - 0,8mm recessed
m1
m2
m3
m4
m5
m6
m7m8
m9
Curve Info
dB(S(WavePort2,WavePort1))Setup1 : Sw eep1
dB(S(WavePort2,WavePort1))_1Setup2 : LastAdaptive
dB(S(WavePort2,WavePort1))_2Setup3 : LastAdaptive
dB(S(WavePort2,WavePort1))_3Setup4 : LastAdaptive
dB(S(WavePort2,WavePort1))_4Setup5 : LastAdaptive
dB(S(WavePort2,WavePort1))_5Setup6 : LastAdaptive
dB(S(WavePort2,WavePort1))_6Setup7 : LastAdaptive
dB(S(WavePort2,WavePort1))_7Setup8 : LastAdaptive
dB(S(WavePort2,WavePort1))_8Setup9 : LastAdaptive
dB(S(WavePort2,WavePort1))_10Setup8 : Sw eep1
dB(S(WavePort2,WavePort1))Setup2 : Sw eep1
dB(S(WavePort2,WavePort1))_11Setup3 : Sw eep1
dB(S(WavePort2,WavePort1))_12Setup10 : Sw eep1
Name X Y
m1 16.9000 -88.5359
m2 17.9000 -31.9616
m3 19.4000 -51.3299
m4 20.8000 -57.2060
m5 29.6000 -47.3199
m6 31.4000 -71.0584
m7 32.5000 -5.4469
m8 33.0000 -6.7775
m9 38.8000 -0.3148
Fig.14 – Frequency response related to Fig. 8 configuration
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 16/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
5 - Study of different strategies in order to modify the cavity propagation
In this chapter all trials we made are reported, hoping that it could be useful for other designer which has to face the same similar situations. At the beginning we try to understand what happens if we place septum inside the cavity and how the cavity behaviour change with the position, dimension and number of it. We started placing a small baffle inside the cavity in proximity of RFIN. Effect is showed in fig. 16. The resonance frequency moved up but another peak start to appear around 21 GHz.
Fig.15 – cap with small baffle
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 17/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
Fig.16 – Frequency response related to Fig. 15 configuration Moving forward the baffle, shift up the frequency of resonance. This effect is shown in fig. 17- 20
Fig.17 – cap with forwarded small baffle
Fig.18 – Frequency response related to Fig. 17 configuration
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 18/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
Fig.19 – cap with more forwarded small baffle
Fig.20 – Frequency response related to Fig. 19 configuration
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 19/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
Another septum is placed in the same position but referred to RFOUT. As Shown in fig.22 graph it appears a wrong way.
Fig.21 – cap of fig.19 and a mirror-like one on RF OUT
Fig.22 – Frequency response related to Fig. 21 configuration
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 20/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
Going back using a single baffle, reducing its thickness decrease the peak levels, especially at high frequency.
Fig.23 – cap of fig.19 with reduced thickness
Fig.24 – Frequency response related to Fig. 23 configuration
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 21/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
Fig.25 –Big septum near RF in connector post
Fig.26 – Frequency response related to Fig. 25 configuration
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 22/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
Fig.27 –Two Big septum near RF in connector post
Fig.28 – Frequency response related to Fig. 27 configuration
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 23/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
A shield seems to produce positive result but we have to take into account not only the EM behavior of the cavity. We have to find a solution that change the cavity behavior without perturb the EM response of components placed in. The following solutions lie close to the microstrip and change it electrical responses.
Fig.29 – RFIn shielded
Fig.30 – Frequency response related to Fig. 29 configuration
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 24/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
Fig. 31 – RFIn and RFOut shielded
Fig.32 – Frequency response related to Fig. 31 configuration
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 25/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
Fig.33 – RFIn and RFOut shielded (RFOut shield raised up)
Fig.34 – Frequency response related to Fig. 33 configuration
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 26/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
Here we start to insert diagonal septum and encouraging results drive us to a possible solution.
Fig.35 – Diagonal baffle input and septum to RF Out
Fig.36 – Frequency response related to Fig. 37 configuration
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 27/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
Fig.37 – Two Diagonal baffles input and septum to RF Out
Fig.38 – Frequency response related to Fig. 37 configuration
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 28/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
Fig.39 – Three Diagonal baffles
Fig.40 – Frequency response related to Fig. 39 configuration
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 29/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
Fig.41 – Four Diagonal baffles
Fig.42 – Frequency response related to Fig. 41 configuration
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 30/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
We introduce here smooth surfaces instead of sharp edge.
Fig.43 – Four Diagonal smoothed baffles
Fig.44 – Frequency response related to Fig. 43 configuration
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 31/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
We move back the baffle in order to avoid contacts with still assembled components on the carrier Here septum are shorted a little in order to guarantee more room between walls and the microstrip edges. This structure appears to be the best solution. We must verify if it is possible to mechanically realise it! In the following pages other solution.
Fig.45 – Four Diagonal smoothed moved back baffles
Fig.46 – Frequency response related to Fig. 45 configuration
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 32/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
The following solutions appear to be also interesting but they may perturb microstrip electrical behaviour.
Fig.47 – Two big reflectors over the microstrips
Fig.48 – Frequency response related to Fig. 47 configuration
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 33/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
Fig.49 – We add a metal ring at the RFIn to the fig 47 configuration: RF Input connector post shielded
Fig.50 – Frequency response related to Fig. 49 configuration
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 34/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
Fig.51 – We add a metal ring also at the RF Output: RF Input and RF Output connector post shielded
Fig.52 – Frequency response related to Fig. 51 configuration
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 35/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
6 - When a solution hide a mistake
In this chapter we would like to underline as a simulation could hide a mistake. We consider here the best solution achieved described in fig 45: Four diagonal septum and flat cap. Time domain simulation with CST and frequency domain HFSS simulation with 0.5 and 0.2 GHz resolution roughly gives comparable results. But HFSS simulation with 0.1 GHz resolution shows a critical behavior at the lower end of the working bandwidth (the most important for scientific observations). In the following pages tuning strategies are described.
Fig.53 – four diagonal septum flat caps
Fig.54 – CST Frequency response related to Fig. 53 configuration
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 36/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
16.00 18.00 20.00 22.00 24.00 26.00 28.00 30.00Freq [GHz]
-60.00
-50.00
-40.00
-30.00
-20.00
-10.00
0.00
Y1
Ansoft Corporation HFSSDesign1Diagonal Septum CAP - 500 MHz Resolution
m1
Curve Info
dB(S(WavePort1,WavePort1))Setup1 : Sw eep1
dB(S(WavePort1,WavePort2))Setup1 : Sw eep1
dB(S(WavePort2,WavePort1))Setup1 : Sw eep1
dB(S(WavePort2,WavePort2))Setup1 : Sw eep1
Name X Y
m1 17.5000 -31.5530
Fig.55 – HFSS Simulation of fig. 53 0.5 GHz Resolution
15.00 20.00 25.00 30.00Freq [GHz]
-80.00
-70.00
-60.00
-50.00
-40.00
-30.00
-20.00
-10.00
0.00
Y1
Ansoft Corporation HFSSDesign1Diagonal Septum CAP - 200 MHz Resolution
m1
m2m3
m4
m5
Curve Info
dB(S(WavePort1,WavePort1))Setup2 : Sw eep1
dB(S(WavePort1,WavePort2))Setup2 : Sw eep1
dB(S(WavePort2,WavePort1))Setup2 : Sw eep1
dB(S(WavePort2,WavePort2))Setup2 : Sw eep1
Name X Y
m1 15.6000 -72.5694
m2 16.2000 -25.6161
m3 17.6000 -24.5020
m4 18.8000 -22.0782
m5 19.4000 -47.7460
Fig.56 – HFSS Simulation of fig. 53 0.2 GHz Resolution
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 37/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
10.00 15.00 20.00 25.00 30.00 35.00 40.00Freq [GHz]
-120.00
-110.00
-100.00
-90.00
-80.00
-70.00
-60.00
-50.00
-40.00
-30.00
-20.00
-10.00
0.00
Y1
Ansoft Corporation HFSSDesign1Diagonal Septum CAP - 100 MHz Resolution
m1
m2
m3
m4
Curve Info
dB(S(WavePort1,WavePort1))Setup3 : Sw eep1
dB(S(WavePort1,WavePort2))Setup3 : Sw eep1
dB(S(WavePort2,WavePort1))Setup3 : Sw eep1
dB(S(WavePort2,WavePort2))Setup3 : Sw eep1
Name X Y
m1 16.4000 -18.5424
m2 17.9000 -11.1096
m3 19.9000 -40.3197
m4 38.4000 -3.9691
Fig.57 – HFSS Simulation of fig. 49 0.1 GHz Resolution
As shown in the graph of Fig. 57 the response a 17.9 GHZ could be dangerous. We now try to tune the response. We act on the cavity ceiling. Moving it down, reducing the volume of the cavity (Fig. 58-60) or up, increasing the volume of the cavity (Fig.61-63)
Fig.58 – Cap with diagonal septum and estruses ceiling
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 38/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
10.00 15.00 20.00 25.00 30.00 35.00 40.00Freq [GHz]
-120.00
-100.00
-80.00
-60.00
-40.00
-20.00
0.00
Y1
Ansoft Corporation HFSSDesign1Diagonal Septum CAP - 1.5 mm Estrused Celing
m1
m2
m3
m4 Curve Info
dB(S(WavePort1,WavePort1))Setup3 : Sw eep1
dB(S(WavePort1,WavePort2))Setup3 : Sw eep1
dB(S(WavePort2,WavePort1))Setup3 : Sw eep1
dB(S(WavePort2,WavePort2))Setup3 : Sw eep1
Name X Y
m1 15.5000 -111.7877
m2 17.2000 -55.6440
m3 19.7000 -12.4876
m4 32.5000 -1.8602
Fig.59 – Frequency response related to Fig. 58 configuration
10.00 15.00 20.00 25.00 30.00 35.00 40.00Freq [GHz]
-100.00
-90.00
-80.00
-70.00
-60.00
-50.00
-40.00
-30.00
-20.00
-10.00
0.00
Y1
Ansoft Corporation HFSSDesign1Diagonal Septum CAP - 1 mm Estrused Celing
m1
m2
m3
m4
Curve Info
dB(S(WavePort1,WavePort1))Setup3 : Sw eep1
dB(S(WavePort1,WavePort2))Setup3 : Sw eep1
dB(S(WavePort2,WavePort1))Setup3 : Sw eep1
dB(S(WavePort2,WavePort2))Setup3 : Sw eep1
Name X Y
m1 16.9000 -38.0443
m2 18.9000 -14.0780
m3 31.4000 -58.1448
m4 32.6000 -5.4186
Fig.60 – Frequency response related to Fig. 58 configuration
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 39/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
Fig.61 – Cap with diagonal septum and recessed ceiling
10.00 15.00 20.00 25.00 30.00 35.00 40.00Freq [GHz]
-120.00
-100.00
-80.00
-60.00
-40.00
-20.00
0.00
Y1
Ansoft Corporation HFSSDesign1Diagonal Septum Cap - 0.5 mm recessed celing
m1
m2
m3
m4
Curve Info
dB(S(WavePort1,WavePort1))Setup3 : Sw eep1
dB(S(WavePort1,WavePort2))Setup3 : Sw eep1
dB(S(WavePort2,WavePort1))Setup3 : Sw eep1
dB(S(WavePort2,WavePort2))Setup3 : Sw eep1
Name X Y
m1 16.3000 -30.8563
m2 17.5000 -14.6214
m3 19.1000 -33.7917
m4 32.8000 -25.0591
Fig.62 – Frequency response related to Fig. 60 configuration
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 40/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
10.00 15.00 20.00 25.00 30.00 35.00 40.00Freq [GHz]
-120.00
-110.00
-100.00
-90.00
-80.00
-70.00
-60.00
-50.00
-40.00
-30.00
-20.00
-10.00
0.00
Y1
Ansoft Corporation HFSSDesign1Diagonal Septum CAP - 0.8 mm recessed
m1
m2
m3
m4
Curve Info
dB(S(WavePort1,WavePort1))Setup3 : Sw eep1
dB(S(WavePort1,WavePort2))Setup3 : Sw eep1
dB(S(WavePort2,WavePort1))Setup3 : Sw eep1
dB(S(WavePort2,WavePort2))Setup3 : Sw eep1
Name X Y
m1 16.2000 -29.6979
m2 17.3000 -24.7720
m3 18.7000 -49.7386
m4 38.1000 -0.6891
Fig.63 – Frequency response related to Fig. 60 configuration
This simulated response satisfies the requirements. We have only to short the septum in order to increase the room between walls and microstrip edges. Final shape is illustrated in the following chapter.
7 - And the winner is.....
When dimensions of the structure under analysis are far from the wavelength at which meshing has been optimised some fake spurious response could arise and predicted results could be not so accurate. In fig. 65 the cavity behaviour with the preferred cap shape is illustrated. In the frequency range between 15 to 21 GHz several simulations are reported. Continuous blue line is obtained with a broad sweep simulation based on meshing at 40 GHz. Red Dots are obtained with adaptive single point simulations at the markers frequencies. Dotted lines represent narrow band sweep simulation centred on red dots.
Doc. Title:
22GHz MMIC Low Noise Amplifier. Housing EM analysis and solution for
cavity resonances Doc. Ref: IRA 434/10 Issue/Rev: 1/0
Date: Jun 2008 Pag.: 41/41
Istituto di Radioastronomia - Technical Report MEDICINA Receiver
Fig. 64 – diagonal “short” baffle 0.8 mm recessed CAP preferred version
10.00 11.00 12.00 13.00 14.00 15.00 16.00 17.00 18.00 19.00 20.00 21.00 22.00 23.00 24.00 25.00 26.00 27.00 28.00 29.00 30.00 31.00 32.00 33.00 34.00 35.00 36.00 37.00 38.00 39.00 40.00Freq [GHz]
-120.00
-110.00
-100.00
-90.00
-80.00
-70.00
-60.00
-50.00
-40.00
-30.00
-20.00
-10.00
0.00
Y1
Ansoft Corporation HFSSDesign1Short Diagonal Septum CAP - 0,8mm recessed
m1
m2
m3
m4
m5
m6
m7m8
m9
Curve Info
dB(S(WavePort2,WavePort1))Setup1 : Sw eep1
dB(S(WavePort2,WavePort1))_1Setup2 : LastAdaptive
dB(S(WavePort2,WavePort1))_2Setup3 : LastAdaptive
dB(S(WavePort2,WavePort1))_3Setup4 : LastAdaptive
dB(S(WavePort2,WavePort1))_4Setup5 : LastAdaptive
dB(S(WavePort2,WavePort1))_5Setup6 : LastAdaptive
dB(S(WavePort2,WavePort1))_6Setup7 : LastAdaptive
dB(S(WavePort2,WavePort1))_7Setup8 : LastAdaptive
dB(S(WavePort2,WavePort1))_8Setup9 : LastAdaptive
dB(S(WavePort2,WavePort1))_10Setup8 : Sw eep1
dB(S(WavePort2,WavePort1))Setup2 : Sw eep1
dB(S(WavePort2,WavePort1))_11Setup3 : Sw eep1
dB(S(WavePort2,WavePort1))_12Setup10 : Sw eep1
Name X Y
m1 16.9000 -88.5359
m2 17.9000 -31.9616
m3 19.4000 -51.3299
m4 20.8000 -57.2060
m5 29.6000 -47.3199
m6 31.4000 -71.0584
m7 32.5000 -5.4469
m8 33.0000 -6.7775
m9 38.8000 -0.3148
Fig. 65 – Frequency response related to Fig. 64 configuration