ADS 匹配和优化.pdf-资料库

nick_nuo-11141953-16359647255600619814.pdf-第1页.png

第1页 / 共18页

nick_nuo-11141953-16359647255600619814.pdf-第2页.png

第2页 / 共18页

nick_nuo-11141953-16359647255600619814.pdf-第3页.png

第3页 / 共18页

nick_nuo-11141953-16359647255600619814.pdf-第4页.png

第4页 / 共18页

nick_nuo-11141953-16359647255600619814.pdf-第5页.png

第5页 / 共18页

nick_nuo-11141953-16359647255600619814.pdf-第6页.png

第6页 / 共18页

nick_nuo-11141953-16359647255600619814.pdf-第7页.png

第7页 / 共18页

nick_nuo-11141953-16359647255600619814.pdf-第8页.png

第8页 / 共18页

5 This chapter shows various ways of creating matching networks by sweeping values and using optimization. Lab 5: Matching & Optimization

Lab 5: Matching and Optimization OBJECTIVES • Create an input match to the RF and an output match to the IF • Tune and Optimize to achieve matching goals Mixer Design Note: From the Smith Chart S-11 results in the last lab, it appears that a series inductor can be added to the input as a first step in moving toward the center of the Smith chart for the RF match at 900 MHz. However, this does not take into consideration the other L and C components. But as a first step, it is reasonable to add the series inductor and see the effects of tuning as ideal components are replaced with real values. PROCEDURE 1. Create a new schematic design for the input match. a. Use the s_params design (last lab) and save it as: s_match. b. Insert an inductor L in series to the input, as shown. Your circuit should look like the one here where the Sweep Plan and Z-ports are removed and set the S-parameter controller to sweep 15 MHz to 2.7 GHz – this will simulate most of the frequencies that will result when the LO is added. 5-2

Lab 5: Matching and Optimization c. Check the sub-circuit to be sure there is no capacitor across the base- collector (from the last lab). d. Simulate and display S-11 in a new data display window. Position the dds window next to the schematic so you can see both at the same time. The default dataset should be the same name as the schematic: s_match. The results of the swept analysis should look like the plot here where a marker is added to show the value of S-11 at 900 MHz: Use the keyboard arrow keys and the mouse to position the marker. 2. Start tuning the inductor a. Select the inductor and start the tuning mode. b. After the tuning dialog and status appear, open and position a new data display window near the tune control so you can see them both – move the schematic aside if necessary. Notice that the default dataset name s_match will appear (same as the schematic). Insert a Smith chart with S11 data and put a marker at 900 MHz. Notice that the S-11 trace is now changed with the real values of C and L. c. Now, set the tune control to slider mode and move the slider back and forth between the ends. Notice that the value of S-11 changes very little because the range of inductance is too narrow. 5-3

Lab 5: Matching and Optimization d. Increase the tuning range: click the Details button and the more detailed tune control appears. Increase the range from 0 to 30 by typing over the existing value. Based on the imaginary part of the impedance (- j3.1), the conjugate value of inductance of 30 nH is close enough. Also, set the resolution Step Size to step to something small such as 0.1 or 0.01 and increase Trace History to 20. e. You should now be able to carefully move the slider and click the step buttons until you reach the impedance of j0.000 as shown by the marker on the last trace. You can use this technique for determining the sensitivity of any component. f. Click the Update button on the tune control and the value of L will appear on the component: g. Save the data display as s_match. 5-4

Lab 5: Matching and Optimization 3. Build a new input matching network (new configuration) CIRCUIT DESIGN NOTE: At this point, the addition of the series inductor is only a first approximation. The remaining ideal components ( DC feeds and blocks) must be replaced by realistic values and this may require a completely different topology other than just adding a series inductance. Also, a shunt capacitor needs to be added to the input to remove the IF signal that may appear there. Therefore, instead of continuing to add components in an attempt to create a match, you will use the following configuration that will solve all the matching problems for the input. This will speed up the lab exercise. a. On the input, remove the series inductor you just tuned. It will be replaced by a network which will achieve the desired RF match and also provide the filtering. b. Change the DC_Blocker to a real capacitor by highlighting the component name (see drawing - DC_Block) and typing in the new component name C and pressing Enter on the keyboard. The DC Block will automatically become a lumped capacitor: Highlight the name, type in the new name, and press Enter. omponent by typing c. Continue modifying the input topology: Insert C=470 pF to shunt the IF (470 pF is a short to 45 MHz). Also, change the DC_Feed1 to L=16 nH to allow the dc to flow but it will block (choke) the RF. Lastly, be sure the Z-ports have been removed. d. Simulate the new input network with a new dataset name: s_match_in. 5-5

Lab 5: Matching and Optimization e. Plot the results and you should see a response like the one shown here where marker 1 is at the RF and marker 2 is the IF (almost an open). However, the response can be more finely tuned (next steps) so that the trace crosses directly through the 50 ohm point. Tuning the blocking cap to widen the sweep and cross the 50 ohm point (shown by dotted line) will be done in the next step to get a better match.. f. Select the blocking capacitor and start tune mode. Adjust the value of capacitance until the trace cuts though the center of the Smith chart. The next step will be done to adjust the inductor so that 900 MHz is directly in the center. g. Tune the inductor by adding it: click Details. When the dialog Tuning produces trace cutting through desired impedance. Next step: tune L to decrease input inductance and maker should be at desired point. 5-6 In the Details dialog (Component button), add the inductor to the tuner by clicking on the parameter.

Lab 5: Matching and Optimization appears, select the Component Button and add the inductor by clicking on the parameter value (not the component) L=16 nH. h. Adjust the inductance and you should get an almost perfect match at 900 MHz. In addition, the matching network is very efficient because it uses a minimum of components to block the dc, choke the RF, and shunt the unwanted IF frequency to ground. Click the Update button and the values will be updated on the schematic. Design Note – L and C values: The tuned values of L and C will vary depending upon how finely you tune. However, C should be just about 1 pF and L should be between 15 and 16 nH for the following steps. 4. Examine the S-22 data a. In the data display, insert a plot of S-22 from the last tuning simulation. You should see that S-22 is close to an open circuit over the frequency range. b. Zoom into the trace area and double click on the trace. When the Trace Options dialog appears, thicken the trace and try using the other settings if you have time. You may need to do this whenever the trace is Trace Options used to thicken trace. 5-7

Lab 5: Matching and Optimization difficult to see or when it is in a very narrow range. Build the output circuit. Output Match Design Note: For the next part of the lab exercise, you will use the optimizer to achieve the output match with a given topology. 5. Build the IF output matching network Build the output to look like the one shown here. The DC feed is a 100 nH inductor in parallel with R_gain resistor (10K) which controls conversion gain. The capacitor (RF_shunt = 1 pF) will help short higher frequencies. Looking into the transistor from the 50 ohm load are two other capacitors for blocking (470 pF is a short to the IF) and C_match for matching. 6. Simulate and plot the S-22 results Simulate (dataset name= s_match_out) and then note your results. The trace should be similar to the one shown here. S-22 at 45 MHz (shown by marker 3) is not matched to the characteristic impedance of 50 ohms. While you could use the tuner to try and achieve a match, the optimizer can also achieve the same goals. Optimization NOTE: The following steps show how to set up an optimization in three steps: 1) Enabling the components to be optimized, 2) Defining the Goals, and 3) setting up the Optimization control. 7. Enable the components to be optimized a. Edit (double click) the DC_Feed2 inductor and click the Optimization/Statistics Setup button. 5-8

资料库

ADS 匹配和优化.pdf

相关推荐

行业

热门标签

最新资料