Microwave Office 2005 Training Linear Simulation – Low Noise Amplifier

AWR, Inc. Company Confidential Linear Simulation The design of a Low Noise Amplifier (Hands-on work) Creating schematics Data libraries Editing schematic symbols (adding explicit ground nodes) Creating graphs Adding measurements to the graphs Advanced measurements Tuning as a design aid We will now work with the linear simulator in MWO, by looking at a low noise amplifier example. In going through this example, we will learn about a number of the important features of MWO. AWR, Inc. Company Confidential

The Design of a Low Noise Amplifier (Hands on work) Design Goals for a 5GHz amplifier: Gain : > 10 dB NF: < 1.2 dB Stability: Unconditional at all frequencies Create schematic and name the schematic ‘Device’ Select Device suitable for design from the device library. Use the Fujitsu FHX35LG data set. This will import the S-Parameter and Noise data for the device. Add simple schematic, graphs and measurements Add the port parameters S11 and S22, gain parameters S21 and MSG Add the stability parameters K and B1, noise parameters NF and NFmin The design goals of the amplifier are shown. We create a schematic, import the transistor model (an S parameter file). We will look at the various S parameters, stability factors, and noise parameters. Remember that the necessary and sufficient conditions for unconditional stability are K>1 and B1 positive. AWR, Inc. Company Confidential

The Design of a Low Noise Amplifier (Hands on work) Place FHX35LG HEMT into schematic Alternatively, you can import the data file from the project view (Right click Data Files, select “Import Data Files”) HINT: The HEMT will be found in the data library, use the element tree and browse to Fujitsu parts. NOTE: When a data file has been read into a project it will be visible in the project tree. AWR, Inc. Company Confidential

The Design of a Low Noise Amplifier (Hands on work) Edit the symbol to use an explicit ground node NOTE: Double click a schematic symbol to open the Element Options dialog box. AWR, Inc. Company Confidential

The Design of a Low Noise Amplifier (Hands on work) Change the symbol to a FET symbol NOTE: Only symbols with three nodes will be listed. AWR, Inc. Company Confidential

The Design of a Low Noise Amplifier (Hands on work) Add two ports and connect these to the transistor HINT: Use the right mouse button to rotate the PORT symbol before placement into schematic. AWR, Inc. Company Confidential

The Design of a Low Noise Amplifier (Hands on work) Set Project frequencies 0.1GHz to 20GHz Step 0.1GHz From the Project Tree double click ‘Project Options’ HINT: CLICK the Apply button to set the frequencies before closing the Project Options dialogue box. AWR, Inc. Company Confidential

The Design of a Low Noise Amplifier (Hands on work) Examine the data set belonging to the transistor Right click the transistor symbol, and select “Edit Subcircuit” Examine the data, linear S-Parameters and Noise data NOTE: A window containing the S-Data will open. NOTE: It is possible to edit this data. BEWARE! AWR, Inc. Company Confidential

The Design of a Low Noise Amplifier (Hands on work) Create a graph called Input Port, add a measurement for S11 (measurement type = Port Parameters) Create a graph called Output Port, add a measurement for S22 Note: You might get the warning message that the noise data has problems at 20 GHz. This is because the noise data only goes to 18 GHz. If you do, proceed anyway – the software extrapolates the noise data. AWR, Inc. Company Confidential

The Design of a Low Noise Amplifier (Hands on work) Create a graph called Two Port Gain, add measurements for S21 (measurement type = Port Parameters) and MSG (measurement type = Linear Gain) Double click the trace definition to open the Graph Properties dialog box Uncheck the Auto limits box, and set the minimum frequency to 0 Explain graph re-scaling, axes format, ident symbols. For example, run the frequency range down to DC … makes for a neater display on the X-axis. AWR, Inc. Company Confidential

The Design of a Low Noise Amplifier (Hands on work) Create a graph called Two Port Noise Parameters, add measurements for NF and NFmin (measurement type = Noise) Double click the trace definition to open the Graph Properties dialog box Uncheck the Auto limits box, and set the minimum frequency to 0 AWR, Inc. Company Confidential

The Design of a Low Noise Amplifier (Hands on work) Create a graph called ‘Stability Data’, add measurements for K and B1 (measurement type = linear) Add a marker to the K factor plot and search for the K value “1” Save the project and then Quit MWO NOTE: Do not select dB for K and B1 Show how to add markers! NOTE: Select the legend box, Right click, choose ‘Search’ AWR, Inc. Company Confidential

The Design of a Low Noise Amplifier (Hands on work) Start MWO and load the previous project Add the extra components shown below Rename schematic ‘Stable Device’ We are now building a gain block that is unconditional stable over the entire operating range of the transistor by adding resistors. The shunt stub tunes out the effect of the shunt resistor at the design frequency. The resistor values are important but not critical. Explain that there are other means of achieving stability, again an engineering topic … don’t get distracted. HINT: Drag the first resistor from the element browser, then copy and paste the second and third resistors. AWR, Inc. Company Confidential

Schematic ‘Stable Device’

The Design of a Low Noise Amplifier (Hands on work) Examine the changes in ‘amplifier gain block performance’ For example the the S21 and the port parameters S11,S22 Seeing the effects of adding the extra components. AWR, Inc. Company Confidential

The Design of a Low Noise Amplifier (Hands on work) Examine the changes in ‘amplifier gain block performance’ Note that K and B1 are consistent with a wideband stable device We now see the stable gain block ready for the next design stage. Operating Point AWR, Inc. Company Confidential

The Design of a Low Noise Amplifier (Hands on work) With the project frequencies unchanged add NF circles and Stability circles. (measurement type = Circle) (To get to this point load Linear Simulation_p17.emp if required) This is fun! It shows the speed of calculation. With slightly incorrect values for the resistors we will see potential instability. Students will have to adjust the values of the resistors to make sure that the potential instability has been removed. Though this is academic! Stress that the project frequency range needs to be changed reduced to prevent too many plots being drawn. HINT: Reset the project frequency range to a few frequencies to reduce the amount of data visible. AWR, Inc. Company Confidential

The Design of a Low Noise Amplifier (Hands on work) Set project frequency to 5GHz Create a new schematic named “Input Matching Circuit” as shown Create a new schematic named “Amp” using the subcircuits The next stage is to match the input port for a compromise between noise figure, gain and match. It also introduces hierarchy. AWR, Inc. Company Confidential

Details of Input Matching Circuit AWR, Inc. Company Confidential

The Design of a Low Noise Amplifier (Hands on work) Activate “L” for tuning and limit the tuning ranges of both L1 and L2 from 0 – 10 nH as shown below HINT: The Min and Max range of the tuner will be set by these element properties. AWR, Inc. Company Confidential

The Design of a Low Noise Amplifier (Hands on work) Change the Input Smith Chart to show “Amp” parameters and tune the inductors to obtain a compromise between Gain and NF Gain Circles. Noise Circles. Explain that for a narrow band design one could look up the standard tables for a series inductor/ shunt inductor L-Matching section to do the job. BUT; MWO and the tuner does the same job, faster. With the use of the tuner the engineer can see immediately the trade off between the various design goals, which is something the formal design route cannot do. By plotting the S22 of the matching circuit along with the gain block’s S11 on a Smith chart and tuning both shunt and series inductors one can examine circuit performance instantly. AWR, Inc. Company Confidential

The Design of a Low Noise Amplifier (Hands on work) Add a simple output matching circuit, maximize the gain of the amplifier and use the tuner to adjust circuit values The output matching circuit is trivial … don’t worry …. it something extra for the students to-do nearing the end of the first lesson. As this lesson has not employed simultaneous matching design methods, the output matching circuit will affect the design of the input matching circuit. Just acknowledge that this is the case. AWR, Inc. Company Confidential

The Design of a Low Noise Amplifier (Hands on work) Reset the project frequency plan to the original wideband set Save project, giving it a suitable name, and quit MWO Having arrived at a narrow band design in terms of gain/noise/match reset the project frequencies to view the wideband performance. AWR, Inc. Company Confidential

AWR, Inc. Company Confidential TXLine Calculator Under the Tools menu…TXLine…. We can predict the practical equivalent line dimensions Introduce the TX Line calculator to convert the electrical line parameters to physical line parameters. Mention all of the technology types covered. This lesson is a fill in. It uses the tuner, it gets engineers to compare electrical and physical models AWR, Inc. Company Confidential

The Design of a Low Noise Amplifier (Hands on work) Run MWO Create two new schematics (ideal and physical) The objective here is to absorb the inductance of the via into the microstrip line in a fashion that the engineer can readily see. In doing so we convert an electrical circuit description to a physical circuit description. AWR, Inc. Company Confidential

The Design of a Low Noise Amplifier (Hands on work) Create a graph called ‘Both’ and add S11 measurements from both schematics Tune length of MLIN until they have similar performance Please note: In the example project provided with the training material the Microstrip line has bends. AWR, Inc. Company Confidential