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United States Patent 
 VEHICLE MOUNTING APPARATUS OF AN AUTOMATIC VEHICLE LOCATION SYSTEM
 Inventor: Hyun-Chul Park, Ahnsan, Rep. of Korea
 Assignee: Samsung Electronics Co., Ltd., Suwon, Rep. of Korea
 Appl. No.: 473,047
 Filed: Jan. 31, 1990
 Foreign Application Priority Data
May 16, 1989 [KR] Rep. of Korea 1989-6524
 Int. CI.5 G08G 1/123
 U.S. CI 340/991; 340/989;
 Field of Search 340/991, 993, 988, 989,
340/901, 904; 342/457, 450, 357; 364/460, 449;
 References Cited
U.S. PATENT DOCUMENTS 4,596,988 6/1986 Wanka 342/457
 Patent Number: 5,142,281  Date of Patent: Aug. 25, 1992
4.622,557 11/1986 Westerfield 342/357
4,700,179 10/1987 Fancher 340/572
4,742,357 5/1988 Racklev 342/457
4,783.654 11/1988 Ichikawa 340/825.44
4,818.998 4/1989 Apsell et al 342/457
4,931,788 6/1990 Creswick 340/825.54
Primary Examiner—Jin F. Ng
Assistant Examiner—Brent A. Swarthout
Attorney, Agent, or Firm—Robert E. Bushnell
A vehicle mounting apparatus for an automatic vehicle location system having a omni-directional antenna, a transmitting and receiving switch, an oscillator frequency converters, a frequency-shift keying demodulator, post office committe standard associate group decoder, a pseudorandom noise signal generator, a phaseshift keying modulator, a transmitting signal generator, a power amplifier, and a power supplier. The vehicle mounting apparatus receives a referencing signal from a control center and transmits an answer signal relating to location of a vehicle to be located.
19 Claims, 2 Drawing Sheets
U.S. Patent Aug. 25,1992 sheet 1 of 2 5,142,281
U.S. Patent Aug. 25, 1992 Sheet 2 of 2 5,142,281
VEHICLE MOUNTING APPARATUS OF AN AUTOMATIC VEHICLE LOCATION SYSTEM
BACKGROUND OF THE INVENTION
The present invention relates to an automatic vehicle location system, more particularly, to a transmitting and receiving apparatus mounted on a vehicle. Generally, the vehicle location system uses a central controller and a vehicle mounted apparatus. A global positioning system (GPS) using a satellite, and a long range navigation C(LORAN C) system using an ultra high frequency(UHF) signal represent the vehicle location system. The GPS has an advantage in that it may exactly reference a vehicle, while it has a disadvantage in that it costs a great deal and its application is limited. The LORAN C, unlike the GPS, may not exactly locate a vehicle.
The object of the present invention is to provide a vehicle mounted apparatus of an automatic vehicle location system playing a role for transmitting a vehicle location signal to a control center in response to a refer- 25 ence signal from the control center.
According to one aspect of the present invention, a vehicle mounted apparatus of an automatic vehicle location system includes:
a non-directional antenna; -,q
a transmitting and receiving (T/R) switch for transmitting an answer signal to the antenna, and for receiving a signal from the antenna;
a first frequency converter for converting the received signal into a signal of a first intermediate fre- 35 quency;
a frequency generator having a temperature compensated oscillator which generates a signal of a given frequency, for generating a signal of a first frequency in order to provide a first radio frequency mixer of the 49 first frequency converter with the signal of the first frequency, and for generating a signal of a second frequency and a signal of a third frequency;
a second frequency converter for converting an output of the first frequency converter into a signal of a 45 second intermediate frequency;
a frequency-shift keying (FSK) demodulator for encoding an output of the second frequency converter in a format of post office committee standard association group code (POCSAG code) by demodulating the out- 50 put of the second frequency converter with the signal of the second intermediate frequency in the manner of frequency-shift keying demodulation;
a POCSAG decoder for producing a flag signal only when an output code of the FSK demodulator and an 55 identifying address code of the vehicle are equal to each other;
a controller for producing a control signal in response to the flag signal, wherein said control signal is sent to the T/R switch; 60
a pseudo random noise (PRN) signal generator for converting the signal of the second frequency into the PRN signal under the control of the controller;
a phase shift keying modulator for modulating an output of the PRN signal with the signal of the third 65 frequency in the manner of the PSK modulation;
an answer signal generator for generating the answer signal informing the location of the vehicle;
a transmitting signal generator for generating the transmitting signal by converting output of the answer signal generator into a signal of the first frequency; and
a power amplifier, operably associated with the control signal from the controller, for amplifying the output of the transmitting signal generator.
BRIEF DESCRIPTION OF THE ATTACHED DRAWINGS
FIG. 1 illustrates an automatic vehicle location system of the present invention; and
FIG. 2 is a circuit diagram for schematizing a inventive vehicle mounted apparatus of the automatic vehicle location system.
DETAILED DESCRIPTION OF THE
The present invention will now be described more specifically with reference to the drawings attached only by way of example.
Referring to FIG. 1, an automatic vehicle location system of the present invention includes a control center CC, a plurality of base station site antennas S1-S3 a paging antenna, and a vehicle mounted apparatus. The vehicle mounted apparatus has an identifying address code in the format of a Post Office Committee Standard Association Group(POCSAG) code. The control center CC modulates POCSAG coded address information in the manner of ,the frequency shift keying and transmits the modulated signal, that is, a referencing signal to the vehicle to be located. The referencing signal is transmitted to the receiver of the vehicle mounted apparatus by way of the antenna in the vehicle mounted apparatus, and the vehicle mounted apparatus then transmits to the site antennas an answer signal relating to the location of the vehicle to the site antennas only when the address code which is changed from the received signal is equal to the identifying address code. The answer signal is transmitted to the control center CC via the site antennas Si-S3, whereby the control center CC can reference the location of the vehicle.
Referring to FIG. 2, the vehicle mounted apparatus has a non-directional antenna 12, a transmitting and receiving switch (T/R switch) 14, a first frequency converter 22, a frequency generator 31, a second frequency generator 39, a frequency shift keying(FSK) demodulator 40, a POCSAG decoder 42, a controller 44, an answer signal generator 49, a phase shift keying(PSK) modulator 53, a transmitting signal generator 57, and a power amplifier 58.
The T/R switch 14 receives the referencing signal from the antenna 12, or transmits the transmitting signal to the antenna 12. The first frequency converter 22 converts a received signal from the T/R switch 14 into a signal of a first intermediate frequency (lst-IF). The frequency generator 31 having a temperature compensated oscillator, generates the signal of the first frequency, the signal of the second frequency, and the signal of the third frequency. The second frequency converter 39 converts an output of the frequency converter 22 into a signal of the second intermediate frequency (2nd-IF). The frequency shift keyinq (FSK) demodulator 40 demodulates an output of the second frequency converter 39 in the manner of frequency shift keying modulation in order to encode the output of the second frequency converter 39 in the format of the POCSAG code. The POCSAG decoder 42 compares the output of the FSK demodulator with the identifying