Radio Frequency Sniffer Design Review by Liem Nguyen

Radio Frequency Sniffer : Design Review by Liem Nguyen 1

Problem statement • Radio frequency: good and bad • Bad – Unwanted radio freq. during device testing/ medical zones – i. e Cell phones in WAT 322 – RF interference with medical devices – “Spying”/ eavesdropping • Solution – 1. 8 GHz RF detector (i. e cell phone) 2

Methods: Block Diagram Figure 1: Block Diagram of RF receiver used in Sniffer Circuit. 3

Methods: Circuit Figure 2: Directional RF Sniffer circuit with speaker output. Original Schematics Courtesy: Kainka B. [1], Varner G. [2] 4

Methods: Specs • Dual λ/2 Dipole antennae at 90° – Target frequency = 1. 8 Ghz – Dipole arm length : λ/4 • LM 358 – High gain • Speaker output Figure 3 [3]: LM 358 pin layout – Adjust gain with 1 M-ohm Linear Pots 5

Summary • Antenna - Dipole arm lengths ~ 3 cm • Circuit layout 75% Complete -Missing Schottky diodes, Speaker + Driver • Further improvements - Calibration with known rf source - Tune Inductance loading 6

Timeline Dec. 12, 2013 • Build Dipole antenna • Observe signals on scope Dec. 17, 2013 Final Presentation Dec. 13 -15, 2013 • Refine antenna length • Build and test w/ speakers • Gather final materials Dec. 16, 2013 • Final Calibration • Solder to permanent board 7

References [1] Kainka, B. (2002). “Mobile Phone Sniffer” Elektor Electronics. Pp 64 -66. Web. 21 November, 2013. [2] Varner, G. (2013) Physics 475 Website. [3] Texas Instruments Website: LM 358 Op Amp Available [Online]: http: //www. ti. com/product/lm 358 8

Questions? ? 9