WEBVTT 00:00.400 --> 00:07.440 This is three videos series on single diode mixer design and optimization using Microwave Office. 00:07.560 --> 00:13.600 In this video, we are going to simulate the mixer circuit and optimize the output spectrum by changing 00:13.600 --> 00:19.480 parameters, and at the end we are going to design the RF filter to remove all the extra frequencies 00:19.480 --> 00:20.240 or spurs. 00:20.320 --> 00:21.400 So let's get started. 00:21.440 --> 00:26.600 In the first step we are going to download the demo project using the link given in the description. 00:26.600 --> 00:30.360 Then run or design environment from start menu. 00:30.480 --> 00:32.160 Let's open the project first. 00:32.280 --> 00:33.960 So I have saved that on desktop. 00:34.120 --> 00:41.160 Go to Diode mixer folder and from there you will find this single diode mixer amp file. 00:41.280 --> 00:42.800 Let's click on open button. 00:42.800 --> 00:46.600 So as you can see till here we have designed this mixer circuit. 00:46.600 --> 00:49.640 And next we are going to run the harmonic balance simulation. 00:49.680 --> 00:52.760 To run the simulation we are going to create a new graph. 00:53.000 --> 00:57.160 And that we can easily do by clicking over this Add New Graph button. 00:57.240 --> 01:02.600 I'm going to name it Eve out because this is the intermediate frequency output from the mixer. 01:02.720 --> 01:06.580 Make sure you have selected the selected the rectangular plot and click over create button. 01:06.620 --> 01:08.420 Next we are going to add the measurements. 01:08.540 --> 01:12.100 So right click on the plot and click on Add New Measurements. 01:12.220 --> 01:14.380 This time the measurements will be nonlinear. 01:14.380 --> 01:17.940 So we'll just go to nonlinear tab. 01:18.140 --> 01:20.940 And from here we have to select the power. 01:21.740 --> 01:25.420 And then we have to select the power harmonics which is here. 01:25.460 --> 01:30.180 Data source should be mixer and the harmonics. 01:30.180 --> 01:34.580 We are going to calculate on port two which is the output port of the mixer. 01:34.620 --> 01:35.260 Here we go. 01:35.300 --> 01:40.060 And make sure you have selected the DBM here and click on okay. 01:40.100 --> 01:43.100 Now just I want to verify the frequency. 01:43.340 --> 01:46.340 So just go to the option of your mixer schematic. 01:46.460 --> 01:53.180 And here as you can see the single point frequency should be 4.25 because this is the project frequency. 01:53.180 --> 01:54.060 So this is fine. 01:54.100 --> 01:57.580 Just cancel that and run the analysis. 01:57.620 --> 01:58.020 Right. 01:58.020 --> 02:01.660 So as you can see this is our if output spectrum. 02:01.660 --> 02:04.540 And here we have lot of extra frequencies as you can see. 02:04.540 --> 02:09.040 Because as of now we are not using any attenuators or filters in the design. 02:09.040 --> 02:14.600 So I just want to show you what will happen if we change the power of the local oscillator. 02:14.840 --> 02:20.080 So as of now the PLO is zero DBM will go back to your mixer circuit. 02:20.200 --> 02:25.240 Here you can clearly see PLO is equal to zero which is assigned to the local oscillator power. 02:25.280 --> 02:25.560 Right. 02:25.600 --> 02:31.040 So if I go back to our IAF output plot first I'm just going to adjust the parameters. 02:31.040 --> 02:33.200 So go to options go to access. 02:33.440 --> 02:37.360 So I want to optimize the left axis. 02:37.640 --> 02:39.760 And it is set to -100. 02:39.760 --> 02:43.920 So instead of going for auto limit I'm just going to uncheck that. 02:44.040 --> 02:50.680 And let's put the parameter let's say 100 and make this plus 20. 02:50.720 --> 02:51.520 Click on apply. 02:51.520 --> 02:55.720 And okay now I'm going to add the marker at the output frequency. 02:55.720 --> 03:01.600 So if you remember from the previous discussion the target or the desired output frequency of mixer 03:01.640 --> 03:04.080 should be 0.5GHz right. 03:04.120 --> 03:08.040 So I'll just right click add marker. 03:08.200 --> 03:12.050 And this is our Point five gigahertz. 03:12.170 --> 03:12.970 Output frequency. 03:13.010 --> 03:13.410 Right. 03:13.450 --> 03:18.850 So apart from that, we are also getting a lot of strong signals, which we can easily remove by adding 03:18.970 --> 03:21.170 bandpass filter so that we'll see later. 03:21.210 --> 03:25.330 Next I'm just going to add a tuner on the low power. 03:25.330 --> 03:29.850 So we can clearly see the effect of low power on the mixer output. 03:29.890 --> 03:32.890 So let's click over this tune button add tuner. 03:33.770 --> 03:35.770 Go back to I.F. out. 03:35.930 --> 03:38.290 Click over this tuner. 03:38.330 --> 03:40.330 Now I'm going to remove this L code. 03:40.570 --> 03:41.570 It's not required. 03:41.690 --> 03:47.130 Let's make it zero to let's say 5 or 10 DBM. 03:48.770 --> 03:49.210 Right. 03:49.250 --> 03:54.210 So as you can see, as I'm changing the low power, you can just look at this marker. 03:54.250 --> 03:57.250 The output power of the mixer is increasing. 03:57.290 --> 03:57.730 All right. 03:57.770 --> 03:59.050 Which totally makes sense. 03:59.050 --> 04:02.210 So as we are increasing the low power the output power is increasing. 04:02.250 --> 04:08.130 Next I'm going to design a bandpass filter which will use on our mixer circuit and see the effect of 04:08.170 --> 04:09.970 that on the spectrum. 04:10.010 --> 04:17.350 Next we are going to design the filter for the if output to remove all the extra frequencies or spurs, 04:17.750 --> 04:21.230 and keep the signal which is at 0.5GHz. 04:21.550 --> 04:28.750 Now to design that IO filter, we are going to use an open source tool, which is RF SIM 99 that you 04:28.750 --> 04:32.150 can easily find inside the same folder I have shared with you. 04:32.310 --> 04:37.590 So if we go to the folder and there you will find this RF sim 99 standalone. 04:37.990 --> 04:41.310 Here you will find this RF sim 99 x file. 04:41.470 --> 04:42.750 Just double click on that. 04:42.950 --> 04:46.150 Now to design a filter we will just simply go to tools. 04:46.670 --> 04:48.870 Click on Design Filters. 04:50.350 --> 04:55.430 And here make sure you have selected the Chebyshev filter which will be a bandpass. 04:55.630 --> 04:58.150 So let's select the bandpass topology. 04:58.630 --> 05:00.470 First branch will be in series. 05:00.670 --> 05:01.990 Everything else will be same. 05:02.230 --> 05:08.270 The center frequency we want should be 500MHz or 0.5GHz. 05:08.270 --> 05:12.470 The bandwidth of the filter should be ten megahertz. 05:12.470 --> 05:17.370 And we'll just leave everything else as it is and click on Calculate. 05:17.370 --> 05:21.410 So from this tool we got all these inductor and capacitance values. 05:21.410 --> 05:26.170 So I'm going to design the exact same filter on our design environment. 05:26.170 --> 05:29.050 So go back to or just close this tuner. 05:29.090 --> 05:32.730 Go to your project panel and I'm going to create another schematic. 05:33.130 --> 05:38.330 Let's name it I of filter and click on create button. 05:39.130 --> 05:43.170 Now to place all the components we'll simply go back to elements. 05:43.170 --> 05:45.450 And these are all the lumped elements. 05:45.610 --> 05:48.650 And so first we will start with placing inductor. 05:48.650 --> 05:50.170 So let's go back to inductor. 05:50.170 --> 05:52.330 We have to place the closed form of inductor. 05:53.250 --> 05:56.410 Select it drag and drop here. 05:56.490 --> 05:58.090 Then we'll need capacitor. 05:58.250 --> 06:03.610 So I'll go to close form of capacitor drag and drop on schematic canvas. 06:03.770 --> 06:05.850 And then we'll just copy paste. 06:05.850 --> 06:09.450 So one capacitor here there will be another inductor. 06:11.850 --> 06:15.010 So you can clearly see the schematic which we are designing here. 06:15.130 --> 06:21.990 And then we'll have another inductor like that and a capacitor at the output. 06:21.990 --> 06:24.310 And then I'm going to quickly assign all the values. 06:24.310 --> 06:29.150 So this inductor will be 82.09 nano Henry. 06:29.390 --> 06:33.790 This capacitor will be 1.234 picofarad. 06:33.830 --> 06:37.990 Similarly this will be 36.523 Picofarad. 06:38.030 --> 06:42.430 Then we have this parallel inductor 2.774 nano. 06:42.470 --> 06:50.070 Henry will be precise here and this will be 82.091, which is same as here Nano Henry. 06:50.190 --> 06:55.350 And then we'll have the capacitor 1.234 Picofarad. 06:55.390 --> 06:57.830 Next I'm just going to make the connection here. 06:57.830 --> 07:01.470 So let's connect all these components together. 07:04.990 --> 07:06.510 I'm just going to shift it. 07:07.910 --> 07:08.430 There we go. 07:08.430 --> 07:11.310 And then this will be ground. 07:11.470 --> 07:14.510 So I'm just going to add the ground port here. 07:14.910 --> 07:19.990 And then I'm going to add two ports at the input and output of the filter. 07:23.210 --> 07:24.850 Just rotate it by right click. 07:25.050 --> 07:25.610 Here we go. 07:25.930 --> 07:27.850 So here we have added the filter. 07:28.010 --> 07:36.050 Now I'm just going to verify the filter by adding a graph and simulate it for S21 and S21. 07:36.370 --> 07:40.930 And we'll see what is happening exactly at 0.5GHz. 07:41.050 --> 07:41.450 All right. 07:41.490 --> 07:44.370 To do that we will just simply add new graph. 07:44.690 --> 07:52.690 Let's name it filter as parameters should be rectangular plot. 07:52.810 --> 07:54.370 Click on create. 07:54.370 --> 08:01.530 And next we are going to add the measurement which will be our linear measurement. 08:01.530 --> 08:05.410 So we just go to linear port parameters as parameters. 08:05.730 --> 08:08.250 Source will be I of filter. 08:08.530 --> 08:10.530 So first we will plot for S1 one. 08:10.530 --> 08:17.250 We will just add that and then we'll plot for S2 one and add this one as well and close. 08:17.370 --> 08:19.930 And next I'm just going to run the simulation. 08:19.970 --> 08:22.090 Now before running the simulation. 08:22.090 --> 08:24.770 As you can see I'm getting just some garbage value. 08:24.810 --> 08:27.030 I just want to add the frequencies. 08:27.270 --> 08:32.910 So let's go back to the schematic which is our air filter. 08:32.910 --> 08:34.590 Right click go to options. 08:35.150 --> 08:45.310 Here I'm just going to add the sweep frequency which will be start from let's say 0 to 1GHz and step 08:45.310 --> 08:45.830 size. 08:46.110 --> 08:48.550 Let's keep it 0.01 apply. 08:48.550 --> 08:50.070 So we'll have 101 points. 08:50.070 --> 08:52.270 Click on okay and rerun the analysis. 08:53.510 --> 08:54.070 Here we go. 08:54.070 --> 08:55.670 Now here we have to adjust the. 08:55.830 --> 09:00.310 Since you can see the amplitude is going up to -800 which we don't want here. 09:00.670 --> 09:03.470 So I'll just go to options. 09:03.710 --> 09:05.510 Go to access left. 09:05.630 --> 09:06.950 Remove the auto limit. 09:07.310 --> 09:09.870 Let's make it -100. 09:10.110 --> 09:13.310 And the maximum value can go up to let's say 20. 09:13.470 --> 09:13.910 Apply. 09:14.030 --> 09:14.670 And okay. 09:14.870 --> 09:21.550 So as you can clearly see the return loss at 0.5GHz is minimum. 09:21.590 --> 09:21.910 All right. 09:21.910 --> 09:27.230 So as you can see and all other frequencies you can see this band, all the other frequencies will be 09:27.230 --> 09:30.640 rejected except this band of between. 09:30.640 --> 09:33.200 I'm just going to add marker here so we can clearly see. 09:33.360 --> 09:39.240 So this band will be approx 450MHz to just move it here. 09:39.720 --> 09:43.400 553.8MHz. 09:43.440 --> 09:43.840 Right. 09:43.880 --> 09:46.640 And the center frequency will be 500MHz. 09:46.760 --> 09:54.040 So if I add another marker on this return loss parameter, you can clearly see it's at 500MHz. 09:54.200 --> 09:57.120 It is minimum which is approx 60dB. 09:57.320 --> 10:01.440 So there will be approximately negligible return loss at this frequency. 10:01.440 --> 10:06.640 That means all the signal will be passed from port one to port two. 10:06.680 --> 10:10.840 So we are going to implement this filter to our mixer circuit. 10:10.920 --> 10:13.400 So let's go back to our mixer circuit. 10:13.560 --> 10:16.560 Let's make some space after diode biasing. 10:16.600 --> 10:20.560 Just going to shift it a bit toward left side. 10:20.760 --> 10:21.920 Make some space here. 10:22.080 --> 10:22.960 Delete this. 10:23.160 --> 10:27.640 And I'm going to add another sub circuit which will be our air filter. 10:28.320 --> 10:28.720 Okay. 10:30.080 --> 10:30.840 Connect it. 10:33.180 --> 10:33.740 Like that. 10:33.780 --> 10:36.700 Now go back to our RF output spectrum. 10:36.820 --> 10:37.300 Here we go. 10:37.380 --> 10:42.060 And now I'm going to run the analysis again and close it. 10:42.100 --> 10:42.580 Here we go. 10:42.660 --> 10:47.060 So as you can clearly see we have removed all the extra frequencies right. 10:47.100 --> 10:51.020 So you can simply compare the plot with and without filter. 10:51.020 --> 10:59.620 And you can clearly see the bandpass filter we have added is able to pass 500MHz frequency and rejecting 10:59.620 --> 11:00.900 all other frequencies. 11:00.980 --> 11:03.860 So this is the desired output we want amplitude. 11:03.860 --> 11:06.860 We can simply increase by adding amplifiers. 11:06.940 --> 11:11.180 Or you can increase the Alo and RF power of the mixer. 11:11.300 --> 11:17.020 So you can simply play with these values and you can plot for different spectrums. 11:17.020 --> 11:20.420 And you can also try different filters at the output of the mixer. 11:20.700 --> 11:26.820 Similarly, you can plot for different Alo powers and RF power and run the different sweeps to plot 11:26.820 --> 11:29.740 for SFR phase shift and other measurements. 11:29.860 --> 11:34.900 So hope you can design and customize diode Mixer for your mixer design requirements. 11:35.020 --> 11:36.500 Using our microwave.