In this episode Shahriar explores the principle operation of automotive FMCW radars. Thanks to a donated automotive radar module, various components of the system can be examined and explored. The PCB reveals three die-on-PCB ASICs responsible for generating and receiving 77GHz FMCW signals coupled to a 2D array of antennas. Several microwave components such as rat-race couplers and branchline couplers can also be observed. PCB rulers from SV1AFN Design Lab also show these microwave components at much lower frequencies. Two other ICs are used for ramp generation and PLL as well as a multi-input LNA/PGA/AAF with 12-bit ADC for IF processing. All components are examined under the microscope and the frequency of operation is calculated by measuring the branchline coupler’s dimensions.
Finally a simple Doppler effect radar is constructed by using a doubler, power divider, mixer and a pair of Vivaldi horn antennas. The Doppler effect can be observed by moving an object in front of the antenna pair.
In this episode Shahriar presents the inner workings of an Agilent 86109B optical/electrical DCA-X oscilloscope module. This particular model offers up to 50GHz of electrical bandwidth and an optical input capable of receiving up to 40Gb/s data rates. The differences between a real-time and sub-sampling oscilloscopes are presented with focus on ADC resolution, signal periodicity requirements and input bandwidth. The block diagram of the module as well as a sub-sampling oscilloscope is also presented.
The teardown of the module shows various components such as samplers, O/E conversion block, impulse generator as well as a step-recovery diode driver. I/O interfaces as well as various analog blocks are also shown. Several modules are further disassembled to observe the inner semiconductor designs under the microscope.
In this episode Shahriar demonstrates the architecture and design considerations for high-power microwave amplifiers. Two architectures are presented, the balanced and Doherty microwave amplifiers. The block diagram, circuit properties and the pros/cons of each architecture are presented. Two available high-power amplifiers modules for cellular applications are also examined. The PCBs show an implementation instance of each amplifier type capable of delivering 100W of RF power. The datasheet of various components as well as an overall system structure are also presented.
In this episode, Shahriar and Shayan discuss the design and characterization of a deceptively simple CMOS inverter-based transimpedance amplifier. The the large and small signal behavior of the CMOS inverter is discussed and measured using the Keithley 2450 and 2460 source meters. The transient response is also measured using a Keysight MSO-S series oscilloscope.
The small signal gain of the circuit is calculated from small signal parameters which are extracted directly by measuring the devices I/V characteristics. The NMOS/PMOS devices used are from an ADL1105 quad-discrete transistor IC. Through the use of a shunt-shunt feedback, the CMOS amplifiers is converted to a transimpedance amplifier which is capable of amplifying the current from a photo-detector diode by a gain of 30kV/A. The feedback theory is used to calculate the gain of the amplifier. The slides for this tutorial can be downloaded here.
In this episode Shahriar explores the functionality of the popular ESP8266 SoC chip. This IC incorporates a full ISM radio as well as the physical/MAC layer for 802.11b/g/n network communication. Furthermore it includes a uC core for code execution making it a low-cost candidate for Internet of Thing applications. This video uses a Sparkfun Thing evaluation board which also includes a LiPo batter charger, voltage regular, flash memory and all the I/O pins which are accessible to the user. The block diagram of the ESP8266 is reviewed as well as the schematic of the complete Sparkfun Thing board.
By using an Arduino library and the Blynk iOS application, a cell phone and the ESP8266 can simultaneously communicate with a server running the Blynk application and transfer data between the application and the module. In this demo various components such as NeoPixel (WS2812), OneWire temperature sensor and battery monitoring functionality are implemented. The code is available here.
The Signal Path (TSP) is an electrical engineering video blog for industry professionals, students and hobbyists. TSP is a non-for-profit website dedicated to provide free education spanning a wide range of electrical engineering topics. Equipment reviews, tutorials and repair videos are posted regularly.