Impedance Matching of 640 GHz SIS Mixer Impedance Matching of 640 - PowerPoint PPT Presentation

Impedance Matching of 640 GHz SIS Mixer Impedance Matching of 640 GHz SIS Mixer of 640 GHz SIS Mixer Impedance Matching Impedance Matching of 640 GHz SIS Mixer in a High IF Band of 11 in a High IF Band of 11- -13 GHz 13 GHz 13 GHz in a High IF Band of 11 in a High IF Band of 11 13 GHz KIKUCHI 1 , Seikoh ARIMURA 1 , J NATANI 1 , Ken’ichi Ken’ichi KIKUCHI , Seikoh ARIMURA , J unji INATANI unji II 1,2 1,2 , Toshiaki SUZUKI , Toshiaki SUZUKI 3 , Akiko IWAMOTO , Akiko IWAMOTO 3 , Yasunori Yasunori FUJ FUJ II , AMAMOTO 3 and Akihito YAMAMOTO and Akihito 1 J apan Aerospace Exploration Agency 2 J apan Communication Equipment Co., Ltd 3 Mitsubishi Electric TOKKI System Co., Ltd http://smiles.tksc.jaxa.jp http://smiles.tksc.jaxa.jp/ ~ sis

Abstract Two 640 GHz SIS mixers are used for SMILES, an atmospheric research mission to be aboard the International Space Station. Those SIS mixers, are operated at a relatively high IF band of 11-13 GHz, which is selected from the scientific reason of the mission. That high IF frequency, however, makes it more difficult to match the SIS device to the subsequent 50 Ω IF line. In addition to an impedance difference in real part, parasitic effects due to bonding wires, RF choke circuit as well as the capacitance of the SIS junctions will play an important role. When the IF matching is poor, the SIS mixer under test often exhibits significant gain ripples in its IF characteristics. A solution for that is to insert a proper impedance transformer between the SIS mixer device and the IF output port and compensate the undesirable parasitic effects. To experimentally derive the output impedance of the SIS device, we have repeated measurements of the receiver gain with respect to an SIS device combined with several different types of matching transformers. We utilized the set of data with different IF characteristics to determine the SIS mixer parameters by means of a fitting technique. This has worked well and allowed us to establish the SIS mixer model to reproduce the measured data. With a proper impedance transformer designed based on the above fitting results, we successfully realized a small ripple and better flatness in the gain profiles of the mixer.

640 GHz SIS Mixer for SMILES 640 GHz SIS Mixer for SMILES LO : 637.32 GHz IF port IF : 11-13 GHz SIS Junction: Nb/AlOx/Nb 500 µ m Junction Size: ~1 x 1 µ m 2 Current Density: 6-7 kA/cm 2 RF Matching: PCTJ GND Sideband Separation: Quasioptical SIS Mixer SIS Device separation with FSP (Engineering Model) In some cases of high IF system, the frequency Characteristics of EM Mixer Receiver separation between upper and lower sideband is not negligible as compared with the RF band- width of an SIS mixer. For SMILES, each mixer USB Mixer 300 I-V Characteristics is selected to have good performance at each band. LSB Mixer 250 (LO-pumped) Receiver Noise (DSB) 200 350 I ( µ A) 150 300 T RX,DSB (K) 250 100 200 50 150 0 100 0.5 1 1.5 2 2.5 3 3.5 4 620 630 640 650 660 LO frequency (GHz) V (mV)

Analytical Model of SIS Mixer Analytical Model of SIS Mixer Z out Z load SIS Device + Bonding Wire SIS Junction with Embedding Impedance at Impedance 50 Ω Superconducting Feed-point Transformer ( Ｉ Microstrip-line ncluding Bonding-wire) SuperMix HFSS (based on measurement) Measurement 5 mm Both SIS device and IF impedance transformer are installed in a mixer block. Connection between ribbon wire and SMA SIS device and connector pin. bonding wire.

LO Frequency Determination of SIS device Determination of SIS device F LO 1 F LO 2 F LO 3 parameters by Fitting Analysis parameters by Fitting Analysis I I I SIS Mixer V V V G G G Transformer 1 SIS Device A Transformer Type IF IF IF G G G Transformer 2 Receiver measurements IF IF IF were repeated with respect to an SIS device combined G G G with several different types Transformer 3 of transformers. IF IF IF Receiver gains and I-V characteristics, measured with different types of transformers and different LO frequencies, were simultaneously fitted to G determine SIS device parameters. n i G 0 = a G ( ) G − 2 1 rR r e v i e c G ∗ − = 0 S I S H E M T e Z Z G ( ) load out = R + 2 R 1 rR M i x e r A m p . + Z Z R r load out I F

Example of Fitting Result : SIS Device A with F LO = 654 GHz Example of Fitting Result : ・ J c = 6813 A/cm 2 , R n = 15.9 Ω I - V C h a r a c t e r i s t i c ・ Relatively high dynamic resistance of 0.3 550 Ω at bias point Data 0.25 Model 0.2 1 1.0 I (mA) 0.15 0.8 2.0 0.5 0.1 0.6 0.05 0.4 0.2 0.2 0 R e c e i v e r G a i n 0 0.5 1 1.5 2 2.5 3 3.5 4 V (mV) 0.2 0.5 1.0 2.0 5.0 0 Z out (output imped- 0 -0.2 ance of SIS device) 5 0 Ω T h r u L i n e -0.2 -2 in 10-14 GHz 。 -0.4 -4 Gain (dB) -0.6 -6 -0.5 -8 -0.8 -2.0 -10 -1.0 -1 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 -12 10 10.5 11 11.5 12 12.5 13 13.5 14 Frequency (GHz) 0 Receiver gain profile with impedance T r a n s f o r m e r N o . 1 - 1 -2 transformer No. 3-1 -4 Gain (dB) 0 -6 -8 -2 -10 -12 -4 10 10.5 11 11.5 12 12.5 13 13.5 14 Gain (dB) Frequency (GHz) -6 0 T r a n s f o r m e r N o . 1 - 2 -2 -8 -4 Gain (dB) -6 -10 -8 -12 -10 10 10.5 11 11.5 12 12.5 13 13.5 14 -12 10 10.5 11 11.5 12 12.5 13 13.5 14 Frequency (GHz) Frequency (GHz)

Example of Fitting Result : SIS Device B with F LO = 618 GHz Example of Fitting Result : ・ J c = 5962 A/cm 2 , R n = 13.7 Ω I - V C h a r a c t e r i s t i c ・ Relatively low dynamic resistance of 0.3 150 Ω at bias point. Data 0.25 Model 0.2 1 1.0 I (mA) 0.15 0.8 2.0 0.5 0.1 0.6 0.05 0.4 0.2 0.2 0 R e c e i v e r G a i n 0 0.5 1 1.5 2 2.5 3 3.5 4 V (mV) 0.2 0.5 1.0 2.0 5.0 0 Z out (output imped- -4 -0.2 ance of SIS device) 5 0 Ω T h r u L i n e -0.2 -6 in 10-14 GHz 。 -0.4 -8 Gain (dB) -10 -0.6 -12 -0.5 -0.8 -2.0 -14 -1.0 -16 -1 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 -18 10 10.5 11 11.5 12 12.5 13 13.5 14 Frequency (GHz) -4 Receiver gain profile with impedance T r a n s f o r m e r N o . 1 - 2 -6 transformer No. 3-2 -8 Gain (dB) -4 -10 -12 -6 -14 -16 -8 -18 10 10.5 11 11.5 12 12.5 13 13.5 14 Gain (dB) Frequency (GHz) -10 -4 T r a n s f o r m e r N o . 2 - 2 -12 -6 -8 -14 Gain (dB) -10 -12 -16 -14 -18 -16 10 10.5 11 11.5 12 12.5 13 13.5 14 -18 10 10.5 11 11.5 12 12.5 13 13.5 14 Frequency (GHz) Frequency (GHz)