No Output Voltage from Voltage Doubler Circuit in Ansys Nexxim  - Page 1
Forum section: electronics / beginners

author: Cynthia
author_rank: Newbie
timestamp: June 20, 2025, 08:27:35 am
content: I am simulating a voltage doubler rectifier circuit in Ansys Electronics Desktop 2024 R2 using Nexxim. I have connected:A sinusoidal input source (VSIN) with Pin = 5 dBm, impedance 50Ω.A matching network modeled as a subcircuit (connected via Port1/Port2).Two diodes (D1, D2) in a voltage doubler configuration.Two capacitors (C1 = 10 pF, C2 = 36 pF).Load resistor RL = 2kΩ.I am using Harmonic Balance (HB) simulation and measuring voltages across:Port4 (input),net_5 (between C1 and D1/D2),net_12 (load side).The HB simulation runs successfully without major errors. However, I observe no output (DC or AC) across the load (net_12), even though the input and node voltages show expected waveforms.Can someone help identify why I’m not getting any output voltage across the load in this rectifier topology, even though all parts are connected and simulation runs successfully?

author: MariuszD
author_rank: Regular Contributor
timestamp: June 20, 2025, 09:36:18 am
content: What is the voltage in net_5?You need to exceed 1.4Vpp to get the significant output voltage.What is in the matching circuit?

author: D2236
author_rank: Regular Contributor
timestamp: June 20, 2025, 10:15:04 pm
content: In principle, it works. We will need more information on your setup.

author: Andy Watson
author_rank: Super Contributor
timestamp: June 20, 2025, 10:38:36 pm
content: What frequency are you using? C1 (and C2) needs to have a much lower impedance than the 2000load for efficient operation.

author: Cynthia
author_rank: Newbie
timestamp: June 23, 2025, 07:07:11 am
content: The rectifier is designed for operation at 2.45 GHz, and the input matching network has been implemented using a combination of a transmission line, shunt stub, and series inductor. The matching circuit was optimized for S11 minimization at 2.45 GHz, and simulated results confirm proper impedance matching to 50 Ω at the rectifier input.At net_5 (input to the rectifier), the waveform amplitude is approximately 635.2 mV peak (1.27 Vpp) at -5 dBm input power. I have attached output at net_5 below. This was verified via harmonic balance simulation. A swept input power from -20 dBm to 0 dBm was simulated, but even at 10 dBm input power, the DC output voltage remains approximately 0 V.

author: Cynthia
author_rank: Newbie
timestamp: June 23, 2025, 07:31:10 am
content: Thank you for your feedback. Here's more detail about my setup:Operating Frequency: 2.45 GHzInput Power Sweep: -20 dBm to +10 dBmInput Matching Network: Designed using a transmission line, shunt stub, and series inductor; S11 optimized for 50 Ω at 2.45 GHz using HFSS and imported into Nexxim as an S-parameter block.Rectifier Topology: Voltage doubler using two HSMS-282E Schottky diodes, with capacitors and a 2 kΩ load resistor.Diode Model: Custom Level 6 SPICE model based on Avago datasheet parameters: IS = 2.2e-8 A, RS = 6 Ω, CJO = 0.7 pF, N = 1.08, TT ≈ 5e-12 s, etc.Voltage at Rectifier Input (net_5): ~635 mV peak at -5 dBm inputSimulation Type: Harmonic Balance, 1-tone, sweeping input powerEven at +10 dBm input, the DC output voltage remains close to 0 V. I have attached the circuit and output images below in the following order:C1: Rectifier circuit with impedance matching subcircuitC2: Warnings generated in the Nexxim simulatorC3: Voltage response at port 4C4: Voltage response at net_7C5: Voltage response at net_5C6: Voltage response at net_12A1: Diode model parameters used in the simulationA2: Harmonic Balance simulation settings

author: MariuszD
author_rank: Regular Contributor
timestamp: June 23, 2025, 07:39:39 am
content: Quote from: Cynthia on June 23, 2025, 07:31:10 amMeasure the voltage after the matching circuit. I suspect it doesn't work.

author: Cynthia
author_rank: Newbie
timestamp: June 23, 2025, 07:48:30 am
content: I'm using 2.45 GHz as the operating frequency. C1 is 100 pF and C2 is 36 pF. Based on calculations, their impedance at 2.45 GHz is about 0.65 Ω (C1) and 1.8 Ω (C2), which is much lower than the 2000 Ω load. So they should be allowing the RF signal to pass through.

author: MariuszD
author_rank: Regular Contributor
timestamp: June 23, 2025, 08:20:54 am
content: This circuit is too simple to contain hidden errors. If voltage is applied, it must work. There is no voltage at point net_5 or it is too low.EDIT: You have errors related to net_5, something is not connected.I don't know this program, but in some programs, it happens that a line can be drawn close to the element's pin, but the program won't register it as connected.In the schematic I see three elements connected to net_5, but the program reports that there is only one.