Over the Sea Transmission of GPS data using RF ... the Sea Transmission of GPS data using RF Transceivers for Fishermen Boats ... a system at 433 MHz with high gain microstrip antenna

Over the Sea Transmission of GPS data using RF Transceivers for Fishermen Boats

Chintan Kaur

Student Member IEEE E&EC Department

PEC University of Technology Chandigarh, India

[email protected]

Mahima Arrawatia Student Member IEEE

Electrical Engineering Department Indian Institute of Technology

Powai, Mumbai, India [email protected]

Abstract— In this paper a GPS module based Transceiver for over the sea applications is developed with a range of few Kms. To achieve a larger range, a system at 433 MHz with high gain microstrip antenna and low power transceiver IC from Texas Instruments CC1101 is developed. The gain of receiver antenna is 9dB. To enhance the portability of the transmitter, gain of the transmitter antenna is kept 1.5dB. A reliable GPS data parsing algorithm has also been developed in the paper.

Keywords— GPS, Transceivers, Microstrip Antenna, Over the Sea communication

I. INTRODUCTION Global Positioning System (GPS) based tracking and

surveillance systems are becoming increasingly popular due to reliable information of location and time provided by it in all climatic conditions. Surveillance using GPS in over the sea application is challenging due to the presence of water vapor over the sea surface and harsh weather conditions decreases the received signal strength considerably. In this paper we have proposed a system to enhance the range of the transmitted data. The system can be used for distress management of fishermen boat or life boats. Size and power consumption are also major challenges if the system has to be placed on the small boats.

At 433 MHz, propagation losses reduce significantly as compared to 2.45GHz with the same output power and current consumption [1]. 800 and 900 MHz bands are generally used due to smaller antenna size but the range achieved is half compared to 433 MHz. In this paper we have designed a variation in monopole antenna at 433 MHz which is small enough for these applications. 433 MHz also has ability to transmit/receive over very long non-line of sight ranges without large power draw on a battery. Hence we are able to achieve a larger range together with small size and minimum power consumption.

Attenuation of propagation over the sea depends upon

several factors, such as, frequency of operation, transmitter and receiver antenna heights, distance of propagation, climate conditions and sea state. Additional propagation loss due to over the sea communication in comparison with free space loss at 433 MHz up to a distance of 10 Km can vary from 20 to 40 dB [2-5]. In the link budget, we have taken worst case of 40 dB.

The link budget is designed for sending location information available at GPS on the transmitter end to control room on a ship at a distance of up to few Kms. Based

on free space path loss, power received at receiver 10 Km away from transmitter is:

Pr = Pt Gt Gr [λ/(4πR)]2 (1) Pr = Pt + Gr + Gt – 22 + 20log(λ/R) in dB (2)

Where:

Pr = received power Pt = transmitted power = 1W = 30 dBm, Gr = gain of receive antenna = 9 dB, Gt = gain of transmit antenna = 0 dBm, λ = wavelength at 433 MHz = 0.69 m, R = distance between transmitter and receiver = 10 Km, Therefore,

Pr = 30 + 9 + 0 - 22 + 20 log (0.69 / 10000) = -66 dBm Hence, we will have margin of -66 + 110 (receiver sensitivity) = 44 dBm to take care the propagation losses over the surface of Sea.

II. TRANSMITTER The block diagram of the transmitter system is shown in Fig.1. The details of each block are given below.

Figure 1: Transmitter System Block Diagram

A. Transmitter Antenna Transmitter antenna is a variation of monopole antenna

designed with dimensions of ground plane 98 mm x 74 mm, which will fit inside easily in a box of diameter 140mm. Height of the antenna is 30 mm. Fig.2 shows the transmitted antenna. Antenna has been designed in such a way that its

radiation is in all direction along the sea surface, so that power received at the ship is least affected with the rotation of boats. To increase the portability of the system transmitted antenna gain is kept small.

Figure 2: Transmitter Antenna (a) Top View (b) Side View (c) 3-D View

B. GPS Receiver with integrated antenna GPS module M10214 [6] is used to get location

information of the fishermen boat. The GPS antenna is integrated within the module to reduce overall dimensions. The module is based on high performance SiRF starIII GPS architecture. The module supports low power mode to reduce power consumption.

C. Microcontroller Atmega8L microcontroller from Atmel [7] is selected to provide interface to GPS module and 433 MHz transmitter. The Atmega8L is a low power controller which draws relatively smaller current while in operation. It also supports extremely low power consumption in sleep mode. The microcontroller draws maximum current of 28μA while in sleep mode. It is also very rich in peripherals eliminating need of any external peripheral, which saves board space and reduce power consumption.

The controller receives data from GPS module via UART port and sends it to 433 MHz transmitter using SPI port. It also puts transmitter in low power idle mode while transmission of data is not required.

D. 433 MHz Transmitter The 433 MHz transmitter is designed using a low power sub 1GHz RF transceiver CC1101 [8] chip from Texas Instruments. CC1101 can operate in 387 – 464 MHz frequency band and supports 2-FSK, GFSK, MSK, OOK and ASK modulations. It can transmit maximum power of 10dBm which can be adjusted within the range of 30dB. It supports programmable data rate from 1.2 K Bauds to 500 K Bauds.

The transmitter is fully configured by microcontroller

using SPI port. Data to be transmitted wirelessly is also transferred to it via SPI port. It also supports extremely low power Sleep mode. The microcontroller can put the transmitter in sleep mode when transmission of data is not required. The transmitter consumes only 200nA current during sleep mode.

A 1 Watt amplifier can be designed to enhance the

transmitted signal strength hence improve the range considerably. Microcontroller can also be used to terminate power to this power amplifier when the transmitter is not transmitting data. This will reduce power consumption significantly.

III. RECEIVER The block diagram of receiver system, which will be

placed on Ship, is shown in Fig. 3. The details of each block are given below.

Figure 3: Receiver System Block Diagram

A. Reciever Antenna The receiver antenna at Ship is designed using a square microstrip patch. The total size of the antenna is 45 cm x 45 cm x 4 cm. The receiver antenna is shown in Fig.4.

Figure 4: Receiver Antenna (a) Top (b) Side and (c) 3-D View

This Block will be mounted on Mast

B. Band Pass Filter and LNA A band pass filter with centre frequenconnected at the output of the receiving apass filter will filter-out unwanted freincrease sensitivity of receiver at 433 MHAmplifier amplifies the weak signal receantenna with minimum addition of thermablocks: Antenna, BPF and LNA will be massembly on a Mast. A low loss coaxial cabat the output of LNA to input of receiver at

The connection of LNA right at the outpreduce overall system Noise Figure signinoise Figure of the system will be Noise Finsertion loss of BPF. If the LNA is instalreceiver within control room, the coaxAntenna on Mast to control room) loss wilthe total system Noise Figure which will rsensitivity.

LNA is designed using SGL-0622 MMThe LNA provides gain of 33dB and Noise433 MHz. It requires supply of 3.3V, supply to the LNA is provided through sused to receive 433 MHz RF signal at conDC extraction circuit is used at the LNvoltage from the RF.

C. 433MHz Receiver Receiver at 433 MHz will be installed

room. The receiver receives signal from Amounted on mast using a low loss coaxial cis designed using CC1101 IC from TexasCC1101 has received sensitivity of -112 data rate. In the link budget, only -110 dtaken giving an additional link margin of 2

Another GPS module can also be placedget location information of Ship. The locatShip can be compared with location infishermen boat, received from receiver tolocation of boat to ship. Fig. 5 shows the fa

Figure 5: Complete System (a) Transmit

Additionally, since the transmitter and (CC1101) are transceivers, they can be uway communication links. GPS location oother required data can also be transmittedwithout any need of additional hardware.make the distress management easier by gof the nearest ship to the boat.

cy at 433 MHz is antenna. The band equency bands to

Hz. The Low Noise eived at receiving al noise. All three

mounted as a single ble will take signal control room.

put of Antenna will ficantly. The total igure of LNA plus lled at input of the xial cable (From ll also be added to reduce the receiver

MIC from Sirenza. e Figure of 0.88 at 10.5mA. The DC ame coaxial cable ntrol room. Proper

NA to extract DC

inside the control Antenna assembly cable. The receiver s Instruments. The dBm at 1.2kBaud dBm sensitivity is dB.

d on the receiver to tion information of nformation of the o calculate relative abricated system.

tter (b) Receiver

receiver ICs used used to set-up two of the ships or any d back to the boats . This will further giving the location

IV. GPS AFigs. 6 and 7 show the GPS

and receiver part, respectivelreceived in NMEA 0183 formparsed and transmitted in the fo

Time, Date, Latitude, N/S, L

To increase the reliability oreceived in both GPRMC anensures that altitude, longitudtransmitted to the base station same instant of time.

Figure 6: The algorit

21

20. Give required d

19. Issue Stx Str

18. Transmit t

17. If not equal, j

16. If equa

15. Compare time of re

14. Check GPRMC for d

13. If received, save a

12. Receive; simultane

11. Wa

10. If received, save a

9. Receive; simultane

8. Wai

7. Configure CC110

6. Initial

5. Set ATMEGA8L as m

4. Initializ

3. Generate a pu

2. Make PC2

1. S

LGORITHM S algorithm for the transmitter ly. The data from GPS is mat [9]. The received data is ollowing sequence:

Longitude, E/W, Altitude, M

of the processed data, the time nd GPGGA is compared. It de and latitude value getting are received from GPS at the

thm of GPS transmitter

. End

delay and go to Step 8

robe, write TxFIFO

through CC1101

jump back to Step 8

al, parse data

eception: GPRMC, GPGGA

data valid i.e. look for "A"

all data till "*" received

eously compare GPRMC

ait for "$"

all data till "*" received

eously compare GPGGA

it for "$"

1 register through SPI

lize USART

master, CC1101 is slave

zation of SPI

lse with 1 ms delay

an output port

Start

Figure 7: GPS Algorithm for rece

V. RESULTS

A. Results of Reciever Antenna Figs. 8 and 9 show VSWR plot and gaiantenna. Resonance frequency is 433 MHfor VSWR < 2 is from 426 to 441 MHz. Gis 9 dB at the center frequency. Fig. 10 shpattern of the receiver antenna. Half-powapproximately 65 degrees. Front to back ra

Fig. 11 shows the fabricated receiver athe results on Network Analyzer.

Figure 8: VSWR Plot for Receiver

12. End

11. Interface with comp./

10. Receive rest of the data ac

9. Save the first byte as le

8. Burst Read Rx FIFO

7. Wait for data to be rec

6. Issue SRx Strobe

5. Configure CC1101 registers t

4. Initialize USART

3. Set ATMEGA as Master, CC1

2. Intilization of SPI

1. Start

eiver side

in plot of receiver Hz and bandwidth

Gain of the antenna hows the radiation wer beamwidth is atio is 15 dB.

antenna along with

r Antenna

Figure 9: Gain Plot fo

Figure 10: Radiation Patte

Figure 11: Fabricated Receive

Side View (c) Testing on Ne

laptop

ccordingly

ength

O

ceived

through SPI

101 is slave

or Receiver Antenna

ern for Receiver Antenna

er Antenna (a) Top View (b) etwork Analyzer (d) Result

B. Results of Transmitter Antenna Figs. 12 and 13 show VSWR plot and the gain plot of the

transmitter antenna, respectively. The bandwidth of the antenna at VSWR less than 2 is from 431.5 MHz to 435 MHz and gain of 1.5 dB at the centre frequency is achieved. Fig 14 shows the radiation pattern of the transmitter antenna.

Figure 12: VSWR Plot for Transmitter Antenna

Figure 13: Gain Plot for Transmitter Antenna

Figure 14: Radiation Pattern for Transmitter Antenna

C. Results of Band Pass Filter Fig. 15 shows the Band pass filter response at 433

MHz.

Figure 15: 433 MHz Band Pass Filter Response

D. Results of GPS Fig. 16 shows the spectrum of the transmitted data at the

output of CC1101. 9.22 dBm output power is transmitted at 433 MHz frequency.

Figure 16: Spectrum of the Transmitted Data at the output of CC1101

Figs. 17 and 18 show the data received from GPS and

the parsed data received at a distant place, respectively. Data received from GPS module is in NMEA format [4]. GPRMC tells about the validity of data. The time of reception of both GPRMC and GPGGA is compared and the time, date, longitude, latitude, altitude information is retrieved and transmitted to a far off place.

Figure 17: Received data from GPS on HyperTerminal

On HyperTerminal, for testing purposes SYNC TX and

PACKET TX are displayed on reception of sync bytes and packet data bytes, respectively. “3” is the ASCII representation of the number of data bytes in each packet. Time follows next, then date separated by a comma, then latitude, N/S, longitude, E/W, altitude and M (unit of altitude) respectively.

Figure 18: Parsed data received at distant place on

HyperTerminal

Information is received accurately till approx. 50m for quick testing using a basic monopole antenna of 21cm

length at the RF output of CC1101 at transmitter end and RF input of CC1101 at the receiver end.

On addition of 1 watt amplifier at the transmitter end with

designed receiver and transmitted antenna, filter and LNA the range would be increased to few Kms as every 6 dB improvement doubles the range.

VI. CONCLUSION In this paper, we have presented a system for over the sea

transmission of GPS data using RF transceivers for fisherman boats. Range of about 50m has been achieved on quick testing which can further be increased to few Kms easily by using the power amplifier at the transmitter end and a high gain antenna and LNA at the receiver end. The connection of LNA right at the output of antenna reduces the overall noise figure significantly which otherwise on installation at the input of the receiver within control room would have lead to the addition of coaxial cable loss to the total system noise figure, hence reducing the receiver sensitivity. The circuit has been developed for over the sea distress management applications but can also find use in torpedoes in sea and on land surveillance.

REFERENCES

[1] e2e.ti.com/cfs-filesystemfile.ashx/__key/CommunityServer.Components.PostAttachments/00.00.10.84.00/Designers_5F00_Guide_5F00_to_5F00_LPRF.ppt

[2] K.Bullington, ”Radio propagation at frequencies above 30 Megacycles,” I.R.E Proc. Wave and Electrons Section ,pp. 1122-1136, October

[3] K.Bullington, “Radio propagation for vehicular communications,” IEEE Trans. on vehicular technology, vol.vt-26, no.4, pp. 295-308, Nov. 1997

[4] R.E Collin, “Hertzian dipole radiating over a lossy earth or sea: some early and late 20th- century controversies,” IEEE Antennas and Propagation magazine, vol. 46, no. 2, pp. 64-79, April 2004

[5] Albert A. Smith, “Electric field propagation in the proximal region,” IEEE Trans. on electromagnetic compatibility, pp. 151-163, Nov. 1969

[6] www.antenova.com/?id=1036 [7] www.atmel.com/atmel/acrobat/doc2486.pdf [8] focus.ti.com/lit/ds/swrs061f/swrso61f.pdf [9] www.usglobalsat.com/downloads/NMEA_commands.pdf