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Design Notes

Multi-rate Harmonic Balance Basics

This project shows a simple single stage up conversion circuit using behavioral amplifiers, mixer and filter.   The intent of this project is to introduce Multi-rate Harmonic Balance (MRHB) for Aplac harmonic balance on a very simple circuit.    

Overview

 

This simple circuit uses an IF frequency of 50 MHz at the input of the mixer and a 1 GHz LO of the mixer.  The filter after the mixer is designed to pass the up converted signal (f1+f2) at 1.05 GHz.   There will not be significant speed or memory differences in this case due to the simplicity of the example.  The intent is to demonstrate the setup basics on a very simple circuit.    You will need at least an APL-150 license to run the Muli-rate portion of this circuit.  

Simulation Setup

"Upconverter" schematic is the traditional HB setup.  The input port is tone 1 and the voltage source on the LO of the mixer is tone 2.   All measurements in this project use Aplac HB as the simulator.  

“Upconverter_MRHB” is the MRHB setup for this same circuit.   Note there are three MRHB blocks added to the schematic.   The paragraphs below will explain the setup for each block.  Note, TRUNC is set to Diamond and the MAXHARMDIA is set due to the harmonic truncation scheme chosen, they are not specific to the type of blocks used.   You assign each schematic model (including subcircuits) to the proper MRHB block by selecting the model in the schematic, right-click, select  Properties, go to the Model Options tab and find the Multi-rate Harmonic Balance section.  

The MRHB block with ID=HB1 sets up the frequencies to simulate the first amplifier.   Therefore NTONES is set to 1 and TONESPEC1 is set to “f1”.  “f1” signifies the tone set 1 in the project. The input port and first amplifier are assigned to use this MRHB block.  Now the input amplifier has been reduced to a one tone simulation where in the traditional method, this amplifier must solve all the tones for the two tones (IF and LO) specified.  

The MRHB block with ID=HB2 sets up the frequencies to simulate the mixer and the filter.   Therefore the NTONES is set to 2, TONESPEC1 is set to “f1”, and TONESPEC2 is set to “f2”.  “f2” signifies the tone set 2 in the project.  The mixer voltage source, the mixer and the filter are assigned to use this MRHB block.  Now the mixer and amplifier are configured to simulate as a two tone simulation, identical to how the mixer simulates in the traditional method. 

The MRHB block with ID=HB3 sets up the frequencies to simulate the second amplifier.   Therefore the NTONES is set to 1.  Since the main tone at the output of the fixer is the up converted signal, TONESPEC1 is set to “f1+f2”.  The output port and second amplifier are assigned to use this MRHB block.  Now the output amplifier has been reduced to a one tone simulation where in the traditional method, this amplifier must solve all the tones for the two tones (IF and LO) specified.  

Graphs

“Output Waveforms” shows the voltage waveform at the output of the circuit.  Notice the results are nearly identical.  

“Spectrum Output” shows the output power spectrum. Double click the measurements to see the setup.

“Spectrum After 1st Mixer” shows the power spectrum at output of the Mixer. Double click the measurements to see the setup.

Schematic - Upconverter_MRHB

Schematic - Upconverter

Graph - Output Waveforms

Graph - Spectrum Output