Merge branch 'main' of https://github.com/ryanrocket/caravel_ft8_receiver into main
diff --git a/.DS_Store b/.DS_Store index f93c433..1515b05 100644 --- a/.DS_Store +++ b/.DS_Store Binary files differ
diff --git a/docs/.DS_Store b/docs/.DS_Store new file mode 100644 index 0000000..125470d --- /dev/null +++ b/docs/.DS_Store Binary files differ
diff --git a/docs/documentation.md b/docs/documentation.md index 8740c3e..b0e2a2e 100644 --- a/docs/documentation.md +++ b/docs/documentation.md
@@ -3,9 +3,9 @@ --- ## Table of Contents 1. Introduction -1.1. Introduction to FT8 -1.2. Architecture Overview -1.3. Toolchain / Technology + 1. Introduction to FT8 + 2. Architecture Overview + 3. Toolchain / Technology 2. PDK Characterization 3. Architecture Refinement 4. Circuit Design and Simulation @@ -34,11 +34,12 @@ ### Characterization of `nfet_01v8` #### 1. Sweep of $V_{GS}$ -[image of circuit] +[image of circuit] <br/> Start by placing a `sky130_fd_pr__nfet_01v8` device with the default parameter values into a new schematic in Xschem. Attach a voltage source V1 to the gate and another V2 to the drain. Ensure that the bulk and source are grounded. Also ensure that V2 or $V_{DS}$ is held at $V_{DD}/2$ or 0.9V. Create a new code block and run a dc sweep of V1. ```spice .control - dc V1 0 3 0.01 + dc V1 0 3 0.01 % dc sweep of Vgs + plot -i(V2) % plot drain current .endc .saveall ``` @@ -69,5 +70,26 @@ $$\int_0^LI_D\mathrm dx \ = \ \mu_{n}C_{OX}\int_0^{V_{GS}-V_{TH}}[V_{GS}-V_{TH}-V(x)]\mathrm dV$$ $$ -\therefore \ I_D \ = \ \frac{1}{2}\mu_nC_{OX}\frac{W}{L}(V_{GS}-V_{TH})^2(1+\lambda V_{DS}) \ \ \ \ \forall \ V_{DS}>V_{DSAT} +\therefore \ \ I_D \ = \ \frac{1}{2}\mu_nC_{OX}\frac{W}{L}(V_{GS}-V_{TH})^2(1+\lambda V_{DS}) \ \ \ \forall \ V_{DS}>V_{DSAT} $$ + +This concludes the basic characterization of the `nfet_01v8` device. In order to obtain accurate circuit simulations and successful circuit design, one should characterize every device they intend to use from the PDK. + +## 3. Architecture Refinement +Typical FT8 recievers should be able to successfuly decode a received signal at atleast -80dBm with an SNR as low as -21dB. In order to conform to these specifications, a strong, simulation-proven architecture will be needed. The basic architecture of the RF front end was known from the start; a filter following the antenna to pass the target band of 7-70 MHz, followed by a low-noise amplifier and ADC. +### 3.1 Filter Derivation +[image of matlab architecture] <br> +Different topologies of bandpass filters were simulated to meet specification. The final decision was a 4th order Butterworth LC bandpass. This allowed for minimum insertion loss, nominal phase delay, and a relatively low noise figure. The generalized transfer function for it's frequency response has been provided below. + +$$ +| \ H(j\omega) \ | = [1+(\frac{\omega}{\omega_{c}})^{2n}]^{-1/2} +$$ + +The intrinsic attenuation can be calculated aswell. + +$$ +A_{d} = 10\log_{10}(1+(\frac{\omega}{\omega_{c}})^{2n}) +$$ + +### 3.2 LNA Derivation +[image of matlab architecture] <br>