4-signal-transport/4.2.md

@@ -3,7 +3,7 @@
 [<< Section 4.1](./4.1)
 ## 4.2 Transmitter Design
 
-The four channel production design expands on the single channel module used for testing by incorporating four channels on one PCB, along with the following additions:
+The transmitter card production design incorporates four channels on one PCB, along with the following additions:
 - Bias tees for each channel to power the cryo-LNAs
 - Sense lines from each bias tee to monitor cryo-LNA voltage and current
 - A single calibration signal injection SMP connector with onboard 1:4 splitter
@@ -11,13 +11,7 @@ The four channel production design expands on the single channel module used for
 - A ganged 4 way SMP connector that interfaces with the flexible stripline
 - A fixture to hold the four SC/APC fiber connections to mate with a coupler on the I/O plate
 
-<div align="center">
-<img src="../uploads/d5258598cefab9cfd796c1d78836ad0a/4ch_top_level_schematic.PNG" width="600"/>
-
-Figure 4: Four channel top level schematic 
-</div>
-
-The first 4-channel TX card PCBs shown in Figure 5 have been delivered to BYU, are being fabricated, and will soon be under test.
+The first 4-channel TX card PCBs shown below have been delivered to BYU, are being fabricated, and will soon be under test.
 
 <div align="center">
 <img src="../uploads/357348f0582791b4ea451a3cce4b31bb/tx_4ch_r3-4_render.PNG" width="600"/>
@@ -25,17 +19,14 @@ The first 4-channel TX card PCBs shown in Figure 5 have been delivered to BYU, a
 Figure 5: Four Channel TX Card 
 </div>
 
-### 4.2.3 RF Over Fiber Performance Analysis
 #### Single Channel Analysis
 
-The single channel transmit module was originally designed with a matching network at the laser, with the intent of improving gain and in-band spectral flatness.  However, it was later removed from the design as it was found to be unnessary with the four layer board stackup. While the matching network was working to improve gain and flatness in early tests with a different substrate, it reduced both gain and flatness on the OshPark 4-layer boards. With an extensive campaign of redesign and testing a variety of approaches, it was found that best gain and flatness was achieved using no matching network and the shortest possible coplanar waveguide traces between final TX amplifier and the laser diode.  This design is now implemented on the new 4 channel PCBs.
-
-The "TX r3-3" transmit module was also tested at different attenuation levels and input power levels to ensure linearity. As seen below, the single channel transmit module maintains its spectral response shape over a wide range of variable attenuator levels and input power levels up to about -40 dBm. 
+Single channel versions of the transmit - receive board modules were tested at different attenuation levels and input power levels to ensure linearity. As seen below, the single channel transmit module maintains its spectral response shape over a wide range of variable attenuator levels and input power levels up to about -40 dBm. 
 
 <div align="center">
 <img src="../uploads/2e233fa91f9e84fb46493100274513da/tx_r3-3_attenuation_test.png" width="500"/>
 
-Figure 8: TX r3-3 tested at different attenuation levels to show the spectral shape remains the same
+Tests were performed at different attenuation levels to show the spectral shape remains the same
 
 <img src="../uploads/0ebf782652409c70c4d94af7154a732d/tx_r3-3_linearity_test.png" width="500"/>