Description
ECE 404L: Radio Frequency Electronic Circuits Laboratory is a 1-credit course taught at Michigan State University for Electrical and Computer Engineering majors. The catalog description for this course is: Radio frequency active and passive circuit design. Impedance matching for specific bandwidths. Tuned amplifier, filter, mixer, and oscillator analysis. High frequency measurements and equipment. The prerequisites for this course are ECE 302, ECE 303 and ECE 305.
Lab Manual and e-Notes
The lab experiments consist of e-Notes explaining the ideas and concepts of each lab experiment. This lab is intended to teach design as well as reinforce concepts taught in ECE 404.
The lab lectures are recorded and can be found on the ECE 404L YouTube channel at: https://www.youtube.com/user/ECE404Lmsu
Table of Contents
Lab I – Introduction to the Oscilloscope, Function Generator and Digital Multimeter
PURPOSE:
The oscilloscope, function generator and digital multimeter are the basic tools in the measurement and testing of circuits. This lab reviews the operation of these instruments along with the use of a compensated probe.
Lab II – AM/FM Radio – Audio Amplifier
PURPOSE:
Over the next few labs we are going to build an AM/FM radio. This lab will focus on soldering and testing of the Audio Amplifier portion of the radio.
The concepts covered are:
1. IC power amps
2. dc and ac models for bipolar transistors;
3. class AB complementary Darlington pair amplifier;
4. small-signal bandwidth;
5. efficiency.
The laboratory techniques covered are:
1. soldering;
2. troubleshooting by doing static measurements with a digital multimeter;
3. measuring gain and bandwidth with a scope;
4. measuring efficiency.
Lab III – AM/FM Radio – AM Radio
PURPOSE:
This lab will focus on soldering and testing of the AM portion of the radio.
The concepts covered are:
1. amplitude modulation (AM);
2. superhetrodyne receiver;
3. AM detector and automatic gain control (AGC);
4. Intermediate Frequency (IF) transformers;
5. IF amplifiers;
6. AM oscillator and mixer.
The laboratory techniques covered are:
1. using the AM feature on the function generator;
2. troubleshooting by doing static measurements with a digital multimeter;
3. measuring gain, bandwidth and quality factor with a scope;
4. tuning.
Lab IV – AM/FM Radio – FM Radio
PURPOSE:
This lab will focus on soldering and testing of the FM portion of the radio.
The concepts covered are:
1. frequency modulation (FM);
2. superhetrodyne receiver;
3. FM ratio detector and automatic frequency control (AFC);
4. Intermediate Frequency (IF) transformers;
5. IF amplifiers;
6. FM oscillator and mixer.
The laboratory techniques covered are:
1. using the FM feature on the function generator;
2. troubleshooting by doing static measurements with a digital multimeter;
3. measuring gain, bandwidth and quality factor with a scope;
4. tuning.
Lab V – Radio Frequency Test Equipment and Applications
PURPOSE:
There have been many types of test equipment developed for high frequency applications. In this lab some of the more common RF test equipment are the spectrum analyzer and signal generator. The spectrum analyzer allows for the searching of sinusoidal signals at very high frequencies and very low power levels. The signal generator can create high frequency signals used to test other RF equipment.
Most RF signals are at very small power levels, so noise plays a large roll in any measurement done in an RF lab. This lab will focus on the common issues that appear when trying to measure radio frequencies. After a few of the equipment concepts are covered, the spectrum analyzer and signal generator are used to tune a Motorola pager receiver.
The concepts covered are:
1. amplitude modulation;
2. superhetrodyne receiver;
3. equivalent circuits of the spectrum analyzer inputs and function generator outputs;
4. noise temperature and noise floor.
The laboratory techniques covered are:
1. operation of a signal generator;
2. operation of a spectrum analyzer.
Lab VI – Measurement of Passive Elements Using a Network Analyzer
PURPOSE:
Spectrum analyzers allow visualization of only the magnitude of RF signals. The network analyzer gives both magnitude and phase information. With the network analyzer, RF components can be measured at very high frequencies.
Resistors, capacitors and inductors have limitations at high frequencies. Models of these elements, in reality, are made up of all three elements which will resonate. With the network analyzer, this resonant frequency can be found and the upper useable frequency of any component can be identified.
The concepts covered are:
1. Phase plane adjustments;
2. Equivalent circuit of a resistor;
3. Equivalent circuit of a capacitor;
4. Equivalent circuit of an inductor;
5. Formula for winding an inductor.
The laboratory techniques covered are:
1. Calibrating the network analyzer;
2. De-embedding the test fixture;
3. Measuring the reflection coefficient;
4. Extracting impedance versus frequency.
Lab VII – Introduction to Ansoft Designer
PURPOSE:
Ansoft Designer is a suite of design tools that fully integrate high-frequency, physics-based electromagnetic simulation, modeling, and automation into an environment for circuit and system analysis.
As with any robust software package, it is best to start with known examples and re-create these in simulation. In this way we can see how our existing knowledge meshes with the tools developed. It can also clear up misconceptions.
The concepts covered are:
1. first time use of Designer;
2. schematic creation and parameter adjustment;
3. creating and editing graphs.
The examples covered are:
1. Lab VI network analyzer plots;
2. Input impedance of a coaxial cable with load;
3. S-parameters of a two-port.
Lab VIII – Filters and Impedance Matching
PURPOSE:
We will continue the use of a spectrum analyzer and network analyzer to evaluate RF circuits.
The concepts covered are:
1. Butterworth low-pass filter;
2. Scaling;
3. Scattering parameters;
4. Matching network for an antenna.
The laboratory techniques covered are:
1. Calibrating the network analyzer for two-port measurements;
2. De-embedding the test fixture;
3. Measuring the scattering parameters:
4. Measuring VSWR
Lab IX – AM Voice Transmitter
PURPOSE: An oscillator is needed to make a transmitter. In this experiment we will make a radio frequency (RF) LC oscillator with a frequency of oscillation in the AM radio band (540 kHz to 1.7 MHz). By coupling an audio signal to the biasing current of the oscillator circuit, the transconductance of that transistor is varied. This causes the oscillator to partially collapse and restart with the audio signal. You will test your transmitter with your AM radio.
