RKE REPEATER RIT SEINOR DESIGN ‘04 INTRODUCTION Nearly all modern cars are equipped with a Remote Keyless Entry system. Such systems allow the user to remotely: Lock/Unlock doors Open trunks Open Doors Arm Alarms Set off Panic Alarms Other uses for the system have evolved, such as using the horn beep from the car to help locate it in a parking lot

RKE REPEATER RIT SEINOR DESIGN ‘04 OBJECTIVE The nature of RKE implementation often leads to limited range. There are several advantages to extending the range of the system. Among these is locating a lost car in a parking lot. Normal Range: 15 to 100 ft.

RKE REPEATER RIT SEINOR DESIGN ‘04 OBJECTIVE The objective of this design will be to extend the range of an existing RKE system to greater than 200 ft. by placing a high performance repeater in the automobile Extended Range: 200+ ft. RF Repeater

RKE REPEATER RIT SEINOR DESIGN ‘04 PROJECT SCOPE Customer Specifications The repeater must be a stand alone device. The repeater must be easy to install, not attaching to anything in the vehicle. The repeater should be able to be sold for between $20 and $50. The repeater should be able to interact with all or most existing RKE systems.

RKE REPEATER RIT SEINOR DESIGN ‘04 PROJECT SCOPE Final Design Specifications: A repeater for RKE systems will be designed and constructed to extend the range of the preexisting systems. It will be a stand alone device independent of the vehicle and the existing RKE system. It will have its own power supply. It will be small and portable. It will be able to work with most existing RKE systems.

RKE REPEATER RIT SEINOR DESIGN ‘04 PROJECT SCOPE Design Constraints Frequency Shift Keying (FSK) key fobs cannot be used Separate units for 315 MHz and 433 MHz operation Use of ASK modulation Power supply is limited to batteries Antenna must be omni-directional

RKE REPEATER RIT SEINOR DESIGN ‘04 RKE BACKGROUND The systems commonly operate on an unlicensed portion of the spectrum intended for intermittent transmission of digital control signals. Some common RKE systems specifications: Frequency: 315 or 433 MHz Data Rate: < 5000 bps Modulation: ASK Range: 15 to 100 ft Output Power: 1 mW

RKE REPEATER RIT SEINOR DESIGN ‘04 RKE BACKGROUND In order to ensure the security of the transmission, a pseudo-random “hopping code” is combined with a control code. b0 | b 1 |... | b n | b n+1 | b n+2 | | b 60 Intro and control code “Hopping” Security Code *Note: Encoding of actual systems varies. For security reasons, exact specifications of many systems are not available. This is meant as a representation of such systems. Key Fob Sends: Car Receives Signal and Compares: Received Code Code 0 Code 1 Code 2 Code 255 Execute Command

RKE REPEATER RIT SEINOR DESIGN ‘04 REPEATER BACKGROUND Repeating is not a new technology. Most existing repeater systems operate as follows: Normal Repeater Design: Receives signal at some frequency ƒ Shifts input signal by some frequency ƒ 1 Retransmits shifted signal ƒ+ƒ 1 Normally receives and retransmits on the same antenna.  The receiver and transmitter are isolated due to frequency shift Many different repeater designs exist using this method and are used in communications.  i.e. Cellular and radio networks

RKE REPEATER RIT SEINOR DESIGN ‘04 SYSTEM OVERVIEW Transmitter/Receiver Switch Antenna ReceiverTransmitter Repeater Circuitry Controller Division of Labor: Naanzem – Antenna Surat – Receiver, Transmitter, and T/R Switch Brian - Receiver, Transmitter, and T/R Switch Bill – Controller, Detection

RKE REPEATER RIT SEINOR DESIGN ‘04 DESIGN: ANTENNA  The design of the antenna is limited by the wavelength, ~1m, and the fact that it has to be omni-directional. Possible antenna designs are:

RKE REPEATER RIT SEINOR DESIGN ‘04 FEASIBILITY: ANTENNA

RKE REPEATER RIT SEINOR DESIGN ‘04 ANTENNA DESIGN The antenna used is a quarter wavelength dipole. Freq (MHz) Resistance (  ) Reactance (  ) Impedance (  ) Phase (Deg) VSWR dB S11 dB S12 dB

RKE REPEATER RIT SEINOR DESIGN ‘04 Impedance Matching The impedance of the antenna does not match the input impedance of T/R switch. A miss-match in impedance creates a loss in the signal. Therefore, a match was designed and is shown:

RKE REPEATER RIT SEINOR DESIGN ‘04 DESIGN: RECEIVER The basic receiver design is: Requirements: Low power consumption Low cost High Gain There are two design options: Build from discrete components Use a Receiver Chip that has been designed for RKE systems. Filter # 1Filter # 2 RF Amplifier Injection Filter 1 st IF Stages 1 st IF Amplifier Detector 1 st Local Oscillator

Evaluate each additional concept against the baseline, score each attribute as: 1 = much worse than baseline concept 2 = worse than baseline 3 = same as baseline 4 = better than baseline 5= much better than baseline Discrete Parts Existing Parts Relativ e We igh t Sufficient Student Skills? 44 11% Sufficient Lab Analysis Equipment? 44 3% Cost of Materials? 24 6% Cost of Purchased Components? 24 8% Complete within 2 quarters? 34 14% Complete by a student? 34 17% Has a similar technology been used before? 45 0% Is it theoretically possible? 45 19% Power Consumption 15 22% Does it use the spectrum well? 45 22% Weighted Score Normalized Score 64.9%100.0%

RKE REPEATER RIT SEINOR DESIGN ‘04 RECEIVER DESIGN The rfRXD0420, produced by Microchip, was chosen as the receiver chip because it best suited the specifications for the receiver. This receiver has the following properties: Frequency Range: MHz Modulation Types: ASK/FSK Price: $2.79 Current Draw: 8.2 mA and <100 nA standby Bit Rate: 80 kbps COMPONENT: Microchip rfRXD0420

RKE REPEATER RIT SEINOR DESIGN ‘04 RECEIVER DESIGN The main receiver functions are already implemented. The filter must still be designed.

RKE REPEATER RIT SEINOR DESIGN ‘04 Rx/Tx Switch Design There is only a single antenna for this system. Therefore, a switch is needed to keep the receiver and transmitter isolated. The switch used is ADG919, manufactured by Analog Devices. Bandwidth: 4GHz Isolation: 43dB Price: $1.07 Current Draw:<1uA

RKE REPEATER RIT SEINOR DESIGN ‘04 Rx/Tx Switch Design (cont.) The Rx/Tx Switch Circuit is:

RKE REPEATER RIT SEINOR DESIGN ‘04 Design Concepts: Transmitter The basic transmitter design is: Requirements Low power consumption Low cost There are two design options: Build from discrete components Use a Transmitter Chip that has been designed for RKE systems. Directional coupler Low Pass filter Power Controller Modulation Input Diagnostics Forward Reverse

Evaluate each additional concept against the baseline, score each attribute as: 1 = much worse than baseline concept 2 = worse than baseline 3 = same as baseline 4 = better than baseline 5= much better than baseline Discrete Parts Existing Parts Relative We ight Sufficient Student Skills? 44 11% Sufficient Lab Analysis Equipment? 44 3% Cost of Materials? 24 6% Cost of Purchased Components? 24 8% Complete within 2 quarters? 34 14% Complete by a student? 34 17% Has a similar technology been used before? 45 0% Is it theoretically possible? 45 19% Power Consumption 15 22% Does it use the spectrum well? 45 22% Weighted Score Normalized Score 64.9%100.0%

RKE REPEATER RIT SEINOR DESIGN ‘04 TRANSMITTER DESIGN The MAX1472 Chip is produced by MAXIM. This transmitter has the following properties: Frequency Range: MHz Modulation: ASK Amplification: up to +10dBm Current Draw: 5.3 mA Price: $3.74

RKE REPEATER RIT SEINOR DESIGN ‘04 Transmitter Design (cont.) The Transmitter Output Circuit is shown:

RKE REPEATER RIT SEINOR DESIGN ‘04 Design Concepts: Filters Noise is an important consideration in this system. Therefore, there are different filters needed in the system. The different filters are: Preselector IF Filter Transmitter Output Filter SAW Filters Passive Filters Active Filters sf16/images/sf16_01.jpg

RKE REPEATER RIT SEINOR DESIGN ‘04 Feasibility: Filters The most important consideration for the filter design is the power consumption of the filter. SAW Filters Passive Filters Active Filters Use for: IF filter Tx Filter Use for: Preselector tro/new/sf16/images/sf16_01.jpg

RKE REPEATER RIT SEINOR DESIGN ‘04 Preselector Design The Preselector used is a SAW filter. Product number: Manufacturer: COM DEV Saw Products Center Frequency: 315 MHz Bandwidth: 430 kHz Price: $1.67

RKE REPEATER RIT SEINOR DESIGN ‘04 Low Pass Filter Designs The designs for the Low Pass filters are:

RKE REPEATER RIT SEINOR DESIGN ‘04 Design Concepts: Repeater Sample the Signal The signal is sampled using an A/D converted and then stored in memory. Demodulate Microcontroller The signal is demodulated using an envelop detector and then delayed using memory. This process uses a microcontroller. Demodulate DSP The signal is demodulated and then processed using a DSP. Simultaneous Retransmission The signal is received on one antenna and then retransmitted using a separate antenna.

Evaluate each additional concept against the baseline, score each attribute as: 1 = much worse than baseline concept 2 = worse than baseline 3 = same as baseline 4 = better than baseline 5= much better than baseline Sample Signal Demodulation Microco ntroller Demodulation DSP Simaltanous Retransm ission Relativ e Weight Sufficient Student Skills? % Sufficient Lab Analysis Equipment? % Cost of Materials? % Cost of Purchased Components? % Complete within 2 quarters? % Complete by a student? % Has a similar technology been used before? % Is it theoretically possible? % Power Consumption % Does it use the spectrum well? % Weighted Score Normalized Score 94.2%100.0%55.2%86.6%

RKE REPEATER RIT SEINOR DESIGN ‘04 Control System Design A Microchip PIC16F87 was selected as the microcontroller. Features: 1.High speed, low power operation. 2.Sufficient I/O Capabilities 3.Low cost 4.Simple but adequate instruction set.

RKE REPEATER RIT SEINOR DESIGN ‘04 Microcontroller Design Set System on Startup Listen for Signal Receive Signal Transmit Signal Set inputs, outputs and interrupts -RX Enabled -TX Disabled

RKE REPEATER RIT SEINOR DESIGN ‘04 Microcontroller Design Set System on Startup Listen for Signal Receive Signal Transmit Signal Wait for interrupt on signal change

RKE REPEATER RIT SEINOR DESIGN ‘04 Microcontroller Design Set System on Startup Listen for Signal Receive Signal Transmit Signal Record received data until end

RKE REPEATER RIT SEINOR DESIGN ‘04 Microcontroller Design Set System on Startup Listen for Signal Receive Signal Transmit Signal Send Data

RKE REPEATER RIT SEINOR DESIGN ‘04 Receive Schematic

RKE REPEATER RIT SEINOR DESIGN ‘04 Transmit Schematic

RKE REPEATER RIT SEINOR DESIGN ‘04 Full Schematic

RKE REPEATER RIT SEINOR DESIGN ‘04 Conclusion The object for this project is to design an RF repeater that will extend the range of most vehicle’s existing RKE systems. The repeater design demodulates the input signal and then stores the signal in a microcontroller. The signal is then demodulated and transmitted. The total cost of the design is estimated to $23.31.

RKE REPEATER RIT SEINOR DESIGN ‘04 Acknowledgements  Dr. Phillips  Dr. Venkataraman  Professor Perlman  Professor Slack  Paul Jacobs  Jan Van Nekeerk 1.

RKE REPEATER RIT SEINOR DESIGN ‘04 Question & Answer