RF, Analog & Semiconductor Device Engineering Portfolio

A collection of three hardware design, full-wave 3D electromagnetic simulation, and semiconductor TCAD physics projects completed at the Department of Electronics Engineering, German University in Cairo (GUC).

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1. 01_5GHz_Chebyshev_Microstrip_LPF_CST/

7th-Order 5.0 GHz Equal-Ripple Chebyshev Microstrip Low-Pass Filter (CST Microwave Studio)

• Analytical Synthesis (Richards' Transformation & Kuroda's Identities): Synthesized a $N=7$ Chebyshev prototype ($0.5\text{ dB}$ passband ripple, $f_c = 5.0\text{ GHz}$, $Z_0 = 50,\Omega$), mapped lumped elements to commensurate $\lambda_g/8$ ($\theta = 45^\circ$) transmission lines via Richards' transformation, and introduced Unit Elements (UEs) with Kuroda's identities to convert un-manufacturable series short-circuit stubs into planar open-circuit shunt stubs ($Z_{\text{Stub1,7}} = 178.77,\Omega$, $Z_{\text{UE1,6}} = 69.41,\Omega$, $Z_{\text{Stub2,6}} = 39.40,\Omega$, $Z_{\text{UE2,5}} = 136.65,\Omega$, $Z_{\text{Stub3,5}} = 37.98,\Omega$, $Z_{\text{UE3,4}} = 162.70,\Omega$, $Z_{\text{Stub4}} = 37.19,\Omega$).
• 3D EM Full-Wave Optimization: Modeled the planar layout on a $2.0\text{ mm}$ FR4 dielectric substrate in CST Microwave Studio and executed Trust Region Framework parametric optimization across 7 independent stub/UE lengths to compensate for open-end fringing capacitance ($\Delta l$) and 3D cross-junction parasitics (recovering the downward-shifted $3.5\text{ GHz}$ cutoff to the exact $5.0\text{ GHz}$ target with $S_{11} < -15\text{ dB}$ across $0\text{–}4.5\text{ GHz}$ and $S_{21} < -40\text{ dB}$ stopband rejection).
• Report & Figures: 5GHz_7th_Order_Microstrip_LPF_Report.pdf | figures/

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2. 02_InGaP_QW_Laser_Diode_Silvaco_TCAD/

Semiconductor Laser Diode TCAD Modeling & Confinement Optimization (Silvaco Atlas & MATLAB)

• Quantum Well (QW) vs. Bulk Heterostructure Physics: Simulated a $10\text{ nm}$ $\text{InGaP}$ ($E_g \approx 1.92\text{ eV}$) Quantum Well active layer sandwiched between $\text{InAlGaP}$ cladding layers using Silvaco Atlas (qwell Schrödinger-Poisson solver, gainmod=5), demonstrating a $20\times$ increase in peak local optical gain ($1160\text{ cm}^{-1}$ vs. $55\text{ cm}^{-1}$ in bulk $\text{InGaAsP}$) and a $100\times$ boost in pre-threshold radiative recombination rate ($2.4 \times 10^{26}\text{ cm}^{-3}\text{s}^{-1}$).
• Separate Confinement Heterostructure (SCH) & Buried Heterostructure (BH) Optimization: Engineered stepped waveguide refractive-index profiles to maximize the optical confinement factor $\Gamma$ (halving the required threshold material gain $g_{\text{th}}$ from $1160\text{ cm}^{-1}$ to $580\text{ cm}^{-1}$) and contrasted planar stripe geometry against Buried Heterostructure (BH) lateral confinement—achieving a 40% reduction in lasing threshold current ($I_{\text{th}}$ lowered from $5\text{ mA}$ to $3\text{ mA}$) with single-mode spectral narrowing ($10^5\times$ photon density surge at resonance).
• Quantum Tunneling Transfer Matrix Method (quantum_well_tmm_transmission.m): MATLAB implementation of the Transfer Matrix Method (TMM) solving the 1D time-independent Schrödinger equation across spatially varying heterostructure potentials ($0.01\text{–}3.0\text{ eV}$).
• Report & Scripts: InGaP_QW_SCH_BH_Laser_Diode_TCAD_Report.pdf | quantum_well_tmm_transmission.m | figures/

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3. 03_ClassAB_BJT_Audio_Power_Amplifier/

Four-Stage Discrete BJT Class-AB Audio Power Amplifier (KiCad, Proteus & Hardware Breadboard)

• 4-Stage Cascaded Architecture: Designed, simulated, and physically constructed a single-supply ($12\text{ V}$) discrete BJT audio amplifier driving an $8,\Omega$ low-impedance speaker load:
  1. Common-Emitter Voltage Gain Stage (2N3904): Biased at $I_{C1} = 2.225\text{ mA}$, $V_{CE} = 5.97\text{ V}$ with partial emitter bypass for $-20.26\text{ V/V}$ unloaded mid-band gain.
  2. Common-Collector Emitter-Follower Buffer (2N3904): High-current buffer ($I_{C2} = 28.0\text{ mA}$, $R_{\text{out}} = 15.4,\Omega$) isolating the high-impedance CE collector.
  3. Adjustable $V_{BE}$ Multiplier Biasing Network: Maintains a constant $1.86\text{ V}$ potential drop across the complimentary power bases ($I_Q = 33.1\text{ mA}$), completely eliminating zero-crossing crossover distortion.
  4. Complementary Push-Pull Class-AB Output Stage (TIP35C NPN / TIP36C PNP): Centers the quiescent output node at exactly $6.00\text{ V}$ ($V_{CC}/2$) and transforms the driving impedance down to $< 1,\Omega$.
• Theory, SPICE & Hardware Correlation: Matched theoretical small-signal hybrid-$\pi$ derivations, KiCad/Proteus SPICE transient simulations, and physical oscilloscope measurements at $-17.0\text{ V/V}$ loaded voltage gain across the $8,\Omega$ loudspeaker.
• Report & Figures: ClassAB_BJT_Audio_Amplifier_Report.pdf | 2N3904-APCT-ND.lib | figures/