Table of Contents:
What is Impedance?
Based on the Oxford English Dictionary, electrical impedance is defined as:
The total opposition presented by a circuit or device to the flow of alternating current, comprising resistance, inductance, and capacitance.
In other words, impedance is a measure of how difficult it is for alternating current (AC) to flow through a circuit.
Impedance vs Resistance
Impedance acts in a similar way to resistance in DC circuits. However, in AC circuits, resistance serves as a component of impedance. Let's further dive into the difference between the two before getting more familiar with impedance.

Impedance (Z） 
Resistance (R) 
Property 
Vector, made up of Resistance (R) and Reactance (X).
Z = R + jX

Scalar. 
Units 
Measured in ohms (Ω)

Measured in ohms (Ω).

Circuit type 
AC circuit 
DC circuit

Phase relationship 
NO phase shift between voltage and current 
Reactance might introduce phase shift in voltage and current 
Power dissipation 
Real power dissipation (P = V^2 / R) and heating effects. 
Both real and reactive power dissipation in AC circuits 
Table 1 Resistance vs Impedance
Reactance, Capacitance, Inductance
Reactance, the vector component of impedance, is made up of capacitance and inductance.
Hence, the equation for impedance can be formulated to be:
Impedance (Z) = Reactance (X) j + Resistance
Impedance (Z) = [Capacitance (C) + Inductance (L)] j + Resistance
Where j indicates an imaginary value.
Figure 1 Voltage and Current phases with resistance, inductance, and capacitance.
Reactance
Reactance is the component of impedance that accounts for the phase shift in AC circuits.
Inductance
Inductance is the property of a material or component to store energy in a magnetic field when current flows through it. It's measured in Henrys (H).
Inductance contributes to inductive reactance, which is measured by
Z=jωL
where Z is the reactance, ω is the frequency in rad/s, and L is the inductance.
Capacitance
Capacitance is the ability of a material or component to store electrical energy in an electric field. It's measured in Farads (F).
Capacitance contributes to capacitive reactance, which is measured by
Z = j*(1/ωC)
where Z is the reactance, ω is the frequency in rad/s, and C is the capacitance.
Impedance Importance for IoT Applications
Optimizing impedance is always an iterative process, especially during the process of designing PCBs. IoT PCBs, most importantly, should have optimized impedance design to function properly. This includes several factors, such as:

Signal Integrity: Proper impedance matching ensures signals are transmitted accurately, preventing distortion or loss of data. This is critical for reliable communication in IoT devices.

Wireless Connectivity: Impedance control is crucial for optimizing antenna performance. It ensures that signals are efficiently transmitted and received, enhancing wireless connectivity in IoT applications.

Reducing Interference: Consistent impedance values help minimize electromagnetic interference (EMI) and crosstalk between traces. This is vital in densely populated IoT PCBs to prevent signal degradation.

Power Efficiency: Impedance control helps in efficient power distribution across the PCB. This is crucial for batterypowered IoT devices, as it minimizes energy wastage and prolongs battery life.

RF Performance: In IoT devices that use wireless communication protocols, such as WiFi or Bluetooth, maintaining proper impedance is essential for maximizing RF signal strength and range.

Sensitivity to Environmental Factors: IoT devices often operate in varied environments. Impedance control helps in ensuring consistent performance, even in conditions with temperature fluctuations or exposure to moisture.
Conclusion
Impedance is a measure of electrical resistance in AC circuits that takes into consideration both resistance and reactance. Reactance itself is also made up of two other components, capacitive and inductive reactance.
In the IoT realm, Impedance is essential as it ensures the authenticity of signals passing via IoT devices and enables consistent connectivity. In addition, strict impedance management should be implemented to reduce electromagnetic interference and enhance signal integrity. This is especially important in wireless communicationdependent IoT devices, where antenna performance is heavily influenced by impedance tuning. As a result, impedance is an important issue when designing IoT devices that work smoothly and efficiently.