Bhavani Sankar. Appalla
To work in the field of Electronics where I could make use of test instruments like Vector Network Analyzer, Spectrum Analyzer, LCR Meter, RF Signal Generator, Power supplies, Multimeters or any other test equipment to characterize Radio Frequency Integrated Circuits or any other Integrated Circuits and assist the organization to get the FCC and CE certificates for various IOT devices. EXPERIENCE
Senior Test Engineer 2 @ Tessolve India July 2017 to till February 6 2020
Reviewing Printed Circuit Boards with RF perspective, whether the CPWG,CPW, MICROSTRIP LINE widths are 50 ohm or not (by plugging in the information from the allegro board file in to National Instruments Transmission line calculator), sharing the laid out board to the simulation team for getting the S parameters of critical nets, MAKING SURE THAT RF CIRCUITS,SYSTEMS AND ANTENNA ARE FARAWAY FROM
DIGITAL TRACES AND CLOCK NETS to avoid problems which might creep later while doing RF characterization and board bring up.
Conducting the range tests and observing the stability of transmitter and receiver,measuring the packet error rate, RSSI,bit error rate on Texas Smart RF Studio software, measuring receiver sensitivity, performing blocking test on receiver, polite spectrum access related tests.
Working towards FCC and CE certification for a module based on Texas Instruments CCXXXXR RF +MCU (FCC Part 15 subpart C, 15.247 & ETSI EN 300 220-1)
worked in the team where I was instrumental in getting the CE Certification for the product XXXXXX (for GSM LB GSM MB, GPS ) and testing was done @ TUV Rheinland India, and I was like a bridge between our company and testing agency.
Near field PCB probing (E & H probes) on XXXXXX navigational device to find the root cause of the low SNR of GPS signals, found a 121.2 MHz clock very close to GPS antenna, whose 13 th harmonic is interfering GPS(1575.42 MHz) signal and just changed that to a slightly different frequency(113 MHz) and the 13 th harmonic was not falling in GPS band and there was a drastic improvement in SNR of GPS signals which can be observed on GPS Locker App
Worked in the RF team where a product called as XXXXXX was built making use of XXXXXXXX chipsets like QPAXXXX PA, WTRXXXX RF Transceiver, and QATXXXX Antenna Tuner IC etc…
Test Automation (using SCPI commands) using open source Python/PyVISA (on and above NI-VISA or Keysight IO Libraries Suite) on Keysight 33GHz/24GHz DSA oscilloscopes and 81150A waveform Generator.
Got basic training on Lab view Environment(by watching some NI Wednesday YouTube videos myself )
Engineer Test & Measurement @ Analog & Radio Frequency Systems Laboratory, Department of Electrical Communication Engineering, Indian Institute of Science Bangalore(May 2015 to June 2017)
Wafer probing on signatone wavelink probe station with Cascade and GGB Probes, along with calibration substrates like CS-3, CS-5 and Cascade ISS P/N 101-190 100 to 250 um pitch
Measurement of S parameters (S11, S21,S12,S22), noise figure of Millimeter Wave amplifiers (Dies/wafer and connectorized) on Network analyzer Keysight PNAN5247A and also on KeysightFieldfoxN9912A along with a calibration kit 85033E DC to 9 GHz, Handling, storage and maintenance of various Consumables/Equipment like High Frequency Probes (GSG and GSSG), 60 GHz Amplifier from Norden, 60GHz Mixer from Marki Microwave, OML Frequency extenders which will extend the frequency range of Keysight
(250 KHz- 20GHz) E8267Dto 55GHz to 70GHz and various PXI cards from NI, conducted some impedance matching experiments by following the Keysight manuals from Prof Bruce Darling of University of Washington Seattle and Mr.w2aew’s YouTube channel on Field Fox N9912 and understood various concepts like smith charts, open, short, load, thru etc…
Undergraduate Instructor @ Indian Institute of Science (08/11/2012 to 27/05/2015).
Assisted course instructor in electronics lab instruction for course on Introduction to electrical and electronics engineering and conducted some experiments like measurement and control of temperature, voltage etc with PIC microcontrollers built in ADC module, and interfaced LCD to microcontrollers(wrote some LCD subroutines by reading the data sheet of the LCD like LCD in command mode or in data mode and LCD in 4 bit mode or 8 bit mode and couldn’t interface the LCD in a single wire mode which is a serial communication mode), linear voltage regulators with short circuit protection, Inductive Proximity Sensor(constant current source+Hartley oscillator(audio range) with only one half of the Ferrite E core),Hartley oscillator (where the inductor is wound on a Ferrite core with two E sections and a bobbin), interfacing LEDs to microcontrollers taking in to account of the dot, BI and RBO etc.., Digital Counter based experiments and viewing the results on the Keysight logic analyzer which is in built on to the oscilloscope,some experiments with MPLAB ICD3, PIC KIT2 and ZIF socket, understood the Incircuit Serial Programming of PIC Microcontrollers, soldered a pick kit2 clone on a perforated board (couldn’t make a PCB at that time),a Short Range FM Transmitter (88MHz-108MHz) where the 22 SWG wire was wound and soldered on to a PCB(some of the images can be seen on my LinkedIn profile)
Lecturer @ Raghu Institute of Technology for 42 months (7 semesters) in ECE Department (29-12-2008 to 19-06-2012).
Instructed Analog and Digital Electronic Circuits, Networks and Systems, Control Systems
Instructed Analog Communications and Linear Integrated Circuits.
Instructed VLSI Technology, Electronic Devices and Circuits.
Integrated NPTEL Courses (Digital Circuits and Systems IITM, Electronics for analog Signal Processing IITM) in my class work for knowledge up-gradation and for benefit of student and academic community.
Instructed Analog Electronics Lab and Digital Electronics Lab in Raghu Institute of Technology.
M.Tech in VLSI & Embedded Systems,
International Institute of Information Technology, Hyderabad.
B.Tech in Electronics and Communications,
Raghu Engineering College,
Vikas Junior College 1998-2000
Secondary School Certificate
St Joseph’s Vizianagaram
Cleared Graduate Aptitude Test in Engineering conducted by IIT Mumbai with a score of 635/1000 PROJECTS
1. Advanced Encryption Standard (AES)
AES is a block cipher, which operates on plain text blocks of a given size (128 bits) and key(128bits)and returns cipher text blocks of the same size (128).In The original Rijndael cipher there are some variants on the block size and key size, in my AES core which is 128 bit key version the key (128 bit) is expanded to 176 byte key, i.e. 1408 bit key or 11 sub keys each of which is 128 bit in length and which are used in the 10 encryption rounds which have operations like Mix Columns, addroundkey, sub bytes and shift rows, in the final round Mix Columns is omitted. After the final round the encrypted cipher text is obtained. 2. Data Encryption Standard (DES)
DES is a block cipher, which operates on plain text blocks of a given size (64bits) and Key (64bits) and returns cipher text blocks of the same size. Thus DES results in a Permutation among the 2^64 possible arrangements of 64 bits, each of which may be either 0or1. 3. PIC Kit2 Clone on bread board and perforated board Followed the Microchips PICKIT2 open source schematic and developed the same for our laboratory, first of all I have burnt the FIRMWARE in to PIC18F2550 using another PIC burner and bread-boarded the components, later these were soldered firmly on to a perforated board. 4. CxxxxE
Going through the Qualcomm datasheets for PA,WTR RF Transceiver
, Antenna Tuner IC and providing the design guidelines (like the 50 ohm CPWG or Stripline or Micro-stripline etc.. and checking their trace widths ) to PCB designers and after that characterizing the RF traces for checking their input and output matching S11 and S22 along with trace loss S21 on VNA and if at all at antenna output port if sufficient amount of power is not seen on Spectrum Analyzer then some amount of tweaking the impedance matching circuits
(after measuring respective S11 or S22 at corresponding ports ) and apart from this my job in this project was to improve the SNR of GPS signals on the navigational device and with lot of R & D, finally the problem was solved.
(My work is completed in this project)
5.6lowpan module for XXX USA
RF measurements, range testing, board bring up etc.. 6. NB IOT for XXX USA
PCB review with RF perspective
Operating Systems : Linux, Microsoft Windows.
Programming Languages : C, PIC16F677 and Arduino.
Assembly Languages and
EDA Tools : MPLAB, Micro-electronica, PSPICE, Texas Instrumensts Smart RF Studio
Soldering : PCB, Perforated boards, footprints,
pastemasks, Wave soldering in an oven.
Equipment : Agilent E3631A Triple output DC Power
supply,Agilent 34405A five and half Digit
Multimeter, Agilent MSOX-2002A 70 M-Hz
Mixed signal Oscilloscope, Network Analyzer
PNAN5247A, MXAN9020A, FieldFox
Watching wonderful educational videos on basic and advanced characterization of electronic circuits in YouTube by Mr. W2AEW (this is his HAM radio call sign) who works in Tektronix as RF Engineer.
Watching wonderful equipment (VNA, SA, SG, Power Supplies, Multimeters etc...) repair videos, equipment review and tear down videos from Dr.Shahriar of signal path blog in my free time.
Reading different circuit schematics from HAM radio books and trying to build them by winding the coils (like the crystal radio,short range FM transmitter, PLL based FM Transmitter along with a PIC Micro-Controller)