# Quasar EE Blog

July 3, 2019

## What is Big-O notation anyway?

Big-O notation is a way of expressing the time complexity of an algorithm, and the Fourier transform is a mathematical technique that can be used to improve the time complexity of certain types of problems such as convolution. The time complexity of the convolution algorithm in the time domain is O(n^2) and the time complexity of the convolution algorithm in the frequency domain is O(n*log(n)), where n is the size of the input data. The Fourier transform can also be used to improve the time complexity of other problems such as filtering, correlation, and image processing.

July 3, 2019

## Using a red LED as an IR remote

IR communication is a simple and widely used method for wireless communication, it's used in many devices such as remote controls, televisions and home appliances. We have shown you how to create a simple IR transmitter/receiver pair using a red visible LED, this is a simple demonstration of the basic principles of IR communication.

July 3, 2019

## LED as an Antenna

Understanding the gain pattern of an antenna is essential for designing and optimizing wireless communication systems. The Friis transmission equation is a widely used method for understanding radiated power, which can be modified to include the gain pattern of the antenna by using the directional Friis transmission equation. Using an LED as an indicator can be a simple way to visualize the gain pattern of an antenna, although the actual measurements of received power should be made with appropriate equipment. It's also important to consider the limitations of the equation, such as the assumption of isotropic antennas and the fact that it is a simplified model.

July 3, 2019

## Decoupling Capacitors

Decoupling capacitors and bias tees play a crucial role in high-frequency PCBs by providing a stable power supply, reducing noise, and providing bias voltage to active devices. The proper placement and selection of these components is essential to ensure optimal performance and stability of the circuit. It's important to consider the current demand, switching speed, and component datasheets when selecting the value and type of these components.

July 3, 2019

## Coupling Problem

Coupling capacitance is a common problem in electronic systems, it can cause signal interference, cross-talk and EMI. There are several solutions to this problem, such as using a Faraday cage, twisted pair cable, transformer and using grounded metal shields. The effectiveness of these solutions is based on the principles of electromagnetic shielding, distance between shielded conductors and electrical conductivity of the material used for shielding. These solutions can be used together to provide a more effective shielding. It's important to consult the datasheet of the ICs and active devices to determine the best placement and values for these components.

July 3, 2019

## Motor Driver

Motor drivers are electronic circuits that are used to control the speed and direction of a motor. There are several different transistor circuit configurations that can be used to drive a motor, each with their own advantages and disadvantages. The single transistor, H-bridge, three-phase bridge, and four-quadrant bridge configurations are the most common. Resolver chip sets can also be used to help with the design of a motor driver by providing precise control of the motor's position and speed. It's important to consult the datasheet of the motor and the requirements of the application to determine the best circuit configuration and components to use.

July 3, 2019

## How an LED Works

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July 3, 2019

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July 3, 2019

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