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60 GHz Amplifier Module Using Low Temperature Co-fired Ceramic Technology
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- Issue Date
- 2009-07
- Citation
- International Technical Conference on Circuits/Systems, Computers and Communications (ITC-CSCC) 2009, pp.1-3
- Publisher
- IEEE
- Language
- English
- Type
- Conference Paper
- Abstract
- Figure 1 shows the microscopic view of the designed and fabricated DA (Drive Amplifier) and PA (Power Amplifier) MMICs (Monolithic Microwave Integrated Circuits) using GaAs PHEMT (Pseudomorphic High Electron Mobility Transistor) 4-inch process. The chip sizes of the DA and PA MMICs have been 3.8 × 1.6 mm 2 and 3.7 × 1.4 mm 2 , respectively. The fabricated 60 GHz DA MMIC was measured the small signal gain (S21) of 20.0 ~ 20.6 dB, the gain-flatness of 0.6 dB, the input reflection coefficient (S11) of -13 ~ -9 dB and the output reflection coefficient (S22) of -7 ~ -6 dB for 59.5 ~ 60.5 GHz as shown in Fig. 2. The gain of the each stages of the 4-staged PA have been designed to have broadband characteristics of input/output matching for the first and the fourth stages and get more gains of edge regions of operating frequency range for the second and the third stages in order to make the gain-flatness of the PA for wide band. The fabricated 60 GHz PA MMIC was measured the S21 of 16.5 ~ 17.2 dB and the gain-flatness of 0.7 dB for 56 ~ 62.5 GHz. And it was also measured the S21 of 16.5 ~ 16.8 dB, the S11 of -16 ~ -13 dB and the S22 of -13 ~ -11 dB for 59.5 ~ 60.5 GHz as shown in Fig. 3. The 60 GHz PA MMIC has maximum output power of 13 dBm as shown in Fig. 4. The Ferro A6S TM LTCC (Low Temperature Co-fired Ceramic) green sheet was chosen because it has a low loss tangent (<0.002 up to 100 GHz) and a low dielectric constant (5~6 for DC ~ 60 GHz). The low loss tangent and the low dielectric constant make the low loss of transmission line on the substrate. In the fabrication process, the via-holes were filled with silver and the ground plane and the transmission lines were also printed with the same conductor to reduce the conductor loss. The width of signal line and the gap between signal line and ground plane were designed to be 70 ㎛ and 80 ㎛. For measuring loss from ribbon bonding, as shown in Fig. 5, we implemented the 3 mm thru-line and the interconnected 3 mm line with ribbon bonding on the LTCC substrate made of a green sheet thickness of 100 ㎛ after co-firing. Interconnection length is 200 ㎛ and the size of ribbon used for bonding is 2 x 0.5 mil 2 . The scattering parameters of the thru-line and the interconnected line with ribbon bonding were measured for 50 ~ 70 GHz. The insertion losses of the thru-line and the interconnected line were 0.2 dB and 0.3 dB at 60 GHz, respectively. The bare chips and the one layer of LTCC after co-firing have the thickness of about 100 ㎛. For shortening length of ribbon-bonding between bonding pads of the chips and the LTCC, the DA and the PA chips were mounted in the cavity formed on the top layer of 7-layer LTCC substrate. And the length between the bonding pads of the DA and PA chips and the CPW line on the LTCC substrate is about 200 ㎛. Figure 6 shows photograph of the implemented module with one DA and one PA chips using the Ferro A6S TM LTCC. The transformer on the LTCC substrate was designed for improving the performance of the module. The module size is 10 mm x 6 mm. Figure 7 shows the measured scattering parameters for LTCC module for 50 ~ 70 GHz. The fabricated 60 GHz amplifier module was measured the S21 of 34.8 ~ 35.0 dB, the gain-flatness of 0.2 dB, the S11 of -12 ~ -7 dB and the S22 of -6 ~ -5 dB for 59.5 ~ 60.5 GHz. The S21 of the module is decreased about 2 dB compared with the bare chips. This indicates that the LTCC is suitable solution for 60 GHz-band package.
- KSP Keywords
- 5 GHz, 60 GHz, 70 GHz, CPW line, Ceramic technology, GaAs pHemt, Green sheet, High electron mobility transistor(HEMT), Input Reflection Coefficient, Input/Output Matching, LTCC substrate