AWR eBooks

RF Electronics Chapter 6: Oscillators Page 194 2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0. Table 6.1. S parameter file from Mini-Circuits with added line in blue. !MAR-6 (TA = 25°C, Id = 16mA) !FREQ. S11 S21 S12 S22 !MHz dB Ang dB Ang dB Ang dB Ang # MHZ S DB R 50 100 -27.96 171 20.1 171 -22.50 5 -27.96 -30 500 -26.02 -105 18.7 138 -21.30 21 -20.00 -104 1000 -17.72 -118 16.4 107 -18.80 28 -17.08 -150 1500 -13.56 -140 14.1 84 -17.10 28 -16.48 180 2000 -10.75 -163 12.0 65 -15.80 26 -15.92 157 2500 -9.37 -176 10.3 55 -15.20 28 -15.92 150 3000 -7.74 169 8.7 42 -14.80 25 -16.48 143 3500 -6.74 157 7.2 30 -14.20 22 -17.72 144 4000 -6.20 146 6.1 18 -13.80 20 -20.00 156 This file can be imported into Microwave Office so that those S parameters for the device can be used in a simulation. To import the s parameter file, it needs to be in the "Touchstone" file format [7]. The only change that needs to be made to the S parameter file as obtained from Mini-Circuits, is the addition of the line shown in blue: # MHZ S DB R 50 That line indicates to Microwave Office that the file has frequencies in MHz, contains S parameters, which must be in the order S11(Real, Imag), S21(Real, Imag), S12(Real, Imag) and S22(Real, Imag), The real part is in DB and the reference impedance is 50 ohm. Any line beginning with "!" is a comment line and is ignored in the data file import. For other formats for data-files see the Microwave Office help files on "Adding Data Files to a project", which includes details on the Touchstone Import files format. That data file is then used as a sub-circuit in the circuit diagram. Example 6.3: 1 GHz Microstrip Oscillator Design This data file is now used to design a 1 GHz oscillator using this MAR6 amplifier and using Microstrip circuits on a Rogers RO4003 substrate. The oscillator consists of three parts: The MAR6 amplifier, A Microstrip resonator (TL1) with tap coupling in order to obtain the correct impedance levels for the coupling into and out of the resonator and thirdly transmission lines TL2 to TL11, which are required to connect the output back to the input and thus provide feedback. The path length around the loop must have the appropriate phase shift to ensure that oscillations will result. In addition, two coupling capacitors are used to provide the correct DC levels at the input to the MAR6 and prevent the output from being shorted at DC. The impedance of the resonator should be as low as possible to provide a reasonable Q, with low radiation losses and a good frequency stability. This is achieved by making the width of the resonator 5 mm. As shown in figure 2.27, for the current version of AWRDE, the Transmission line Calculator can be opened by right clicking on a MLIN element in the project and selecting Synthesize. The resonator (TL5) shown in figure 6.39 uses an MLEF circuit element for which the Synthesize function is not implemented. The MLEF element must thus be temporarily changed to MLIN, or the older program TXLine, which is part of MWO can be used for the calculations of the resulting resonator impedance and the required length of the resonator. For the RO4003 substrate with Er = 3.38, using the Transmission line Calculator, results in a characteristic impedance of 24.8 and 44.0 mm length for a quarter wavelength. The same values are obtained from TXLine as shown in figure 6.37. RF Electronics: Design and Simulation 194 www.cadence.com/go/awr

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