JP4929831B2 - Position detection apparatus and position detection method - Google Patents

Description

  The present invention relates to a position detection apparatus and a position detection method, and more particularly to a position detection apparatus and a position detection method for receiving a radio wave from a satellite and detecting a current position.

  A GPS (Global Positioning System) is a system that receives radio waves from a plurality of satellites and detects a current position. The satellites in this case are not geostationary satellites, but 32 satellites that orbit the altitude of 20,000 km and change their positions with respect to the earth. In order to detect the current position, it is necessary to receive GPS signals from at least three of the 32 satellites. Actually, GPS signals are received from four satellites to detect the current position. A 30-second mainframe is transmitted from each satellite. This main frame is composed of 5 subframes each having 6 seconds, and each subframe is composed of 300-bit data. Of the first to fifth sub-frames, the first to third sub-frames store clock correction information unique to each satellite and “ephemeris” which is orbit information. The fifth two subframes store “almanac”, which is general orbit information common to all 32 satellites. FIG. 10 is a block diagram showing a configuration of a conventional position detecting device using a wristwatch. As shown in FIG. 10, the position detection device includes an antenna 11, an RF unit 12, a baseband processing unit 13, a system 14, and a power supply 15.

  The antenna 11 receives a GPS signal from a satellite and inputs it to the RF unit 12. The RF unit 12 demodulates the input GPS signal and inputs the baseband signal to the baseband processing unit 13. The baseband processing unit 13 includes a CPU 131, n search engines 132, and a synchronization detection unit 133. The synchronization detection unit 133 detects an 8-bit synchronization signal (referred to as “preamble”) at the head of each subframe, and inputs the start timing of the subframe to the CPU 131. The CPU 131 activates n search engines 132 based on the preamble from the synchronization detection unit 133. Each search engine takes one subframe and stores the data. Therefore, when receiving GPS signals from four satellites and detecting the current position, the data of five consecutive subframes transmitted simultaneously from each satellite is stored in order in five search engines, The current position is detected by data stored in a total of 20 search engines. The system 14 is, for example, a clock device, and displays the current position detected by the baseband processing unit 13. The power source 15 includes a small coin-type battery (for example, 2016 type) and a DC / DC converter, and supplies power to the RF unit 12, the baseband processing unit 13, and the system 14.

Many proposals have been made regarding position detection technology using GPS.
For example, in a proposed GPS navigation apparatus, ephemeris data is divided and collected in units of subframes and stored in a memory, thereby shortening the time required for data collection. Specifically, a subframe collection flag is provided, and this flag is set to 1 (valid) according to the collection of the subframe. Therefore, since it is determined by the flag whether or not the subframe has been collected once, it is not necessary to collect the subframe again, and the collection time can be shortened. (See Patent Document 1)
Further, in a proposed GPS receiver, a detection unit having a plurality of channels, a message collection unit that collects a navigation message transmitted from a satellite demodulated by the detection unit, a message analysis unit that analyzes the collected message, A positioning unit that calculates the position of the receiver from the propagation time and the position of the satellite, and a timing designating unit that designates a timing for scanning the navigation message for the message collection unit of each channel, and a navigation message in one or more channels When collecting messages, specify the message collection timing for other channels. Therefore, by quickly detecting a preamble pattern that is a bit pattern indicating the head of a navigation message transmitted from a GPS satellite, reducing the time to detect a preamble pattern in all channels, and quickly collecting navigation messages, Reduce positioning time. (See Patent Document 2)
In addition, in a proposed GPS receiver, GPS satellites can be captured in a plurality of channels, time information extracted from satellite data from the captured GPS satellites, and current time measured on the GPS receiver side Based on the time, the distance between the GPS satellite and the current position (the position of the GPS receiver) is measured. Further, the detailed orbit information (ephemeris) included in the satellite data is taken out, the satellite position is calculated, and the position of the GPS receiver is calculated in consideration of the measured distance. As a result, synchronization with the satellite data can be established at an early stage, and the time required to start positioning is shortened. (See Patent Document 3)
In a proposed position detection device, data from GPS satellites received by a GPS receiver has a hierarchical structure of mainframe, subframe, and word, and a parity bit for checking is incorporated in each word check. Therefore, the GPS receiver performs a parity bit for each word, and outputs how many words are NG in the parity check in the received subframe. The reception determination unit determines whether data reception is possible based on the number of parity checks NG. When it is determined that data cannot be received, the control unit turns off continuous energization for data collection, turns on the switch for data collection again after a predetermined time, and energizes the main power supply. As a result, when continuous energization is performed in order to acquire satellite orbit information, it takes a long time to collect data if the reception environment is bad, thereby avoiding unnecessary power consumption. (See Patent Document 4)
JP-A-3-42793 Japanese Patent Laid-Open No. 11-304899 JP 2000-292521 A JP 2003-194910 A

In the conventional position detection using the GPS including the above-described Patent Documents 1 to 4, the first to fifth subframes are continuously acquired. Since the five subframes are 30 seconds, if the margins before and after are included, the time for continuous energization needs 40 seconds or more. However, in the case of the wristwatch position detection device of FIG. 10 and other portable position detection devices using a coin-type battery, as in the case where a coin-type battery is used as a power source for supplying power to each part, as in FIG. If the battery is continuously energized for 40 seconds or more, the discharge characteristics of the battery deteriorate, and the apparatus itself may be stopped due to a significant voltage drop of the battery.
The present invention is for solving such a conventional problem, and even when a coin-type battery or other small battery is used as a power source, a significant voltage drop of the battery occurs and the apparatus stops functioning. An object of the present invention is to reliably receive a GPS signal from a satellite and detect the current position without causing such a situation.

The position detection device according to claim 1 is configured to receive power from the power supply means by receiving the GPS signal transmitted from the satellite in the operation mode in which the power is supplied from the power supply means and the power supply means that supplies power from the battery. In a non-operating mode, receiving means for stopping reception, on-timer means for counting a time shorter than the time for transmitting the main frame in the GPS signal, off-timer means, and operating the receiving means during counting of the on-timer means Mode control means for setting the mode to a non-operation mode while the off-timer means is counting, and setting the receiving means to the operation mode in response to an acquisition instruction from the outside, and starting the counting operation of the on-timer means The GPS signal received during counting by the start instruction means and the on-timer means First acquisition means for acquiring a part of specific data from the first to nth specific data transmitted in time series by the satellite from among the first specific means, and the acquired specific Based on the data, the count time of the off-timer means is set, the off-timer setting means for starting the count of the off-timer means, the count of the on-timer means is started in response to the end of the count of the off-timer means, The operations of the second acquisition means for acquiring data other than the acquired specific data during counting and the off-timer setting means and the second acquisition means are repeated until all the n pieces of specific data are acquired. and operation control means for causing, and a determining information determining unit position information by the acquired n pieces of the specific data has been It has become the example was constructed.

  2. The position detecting device according to claim 1, wherein, as described in claim 2, the device is configured to correspond to each of n pieces of specific data from the first to the nth transmitted in time series by the satellite. Storage means, and the information determination means stores in the storage means corresponding to the order of the specific data acquired from the GPS signals received by the reception means, and the specific data corresponding to all of the n storage means The position information may be determined when the information is stored.

3. The position detection apparatus according to claim 1, wherein, as described in claim 3, the operation control means receives arbitrary m (1 ≦ m ≦ n) specific data by the receiving means at the end of the operation mode. Alternatively, the time for switching from the non-operation mode to the operation mode may be calculated.
2. The position detection apparatus according to claim 1, wherein the operation control means is a period in which the reception means can receive at least one m (1 ≦ m ≦ n) specific data in the GPS signal. The operation mode may be controlled.
In the position detection device according to claim 1, as described in claim 5, the n specific data from the first to the n-th transmitted in time series by the satellite are the first to the fifth The sub-frame data may be configured as described above.

The position detection method according to claim 6 is a non-operation in which a GPS signal transmitted from a satellite is received and power is not supplied from the power supply means in an operation mode in which power is supplied from a power supply means that supplies power by a battery. In the mode, the operation mode is set during the counting of the step A for stopping the reception and the on-timer means counting the time shorter than the time for transmitting the main frame in the GPS signal, and the non-operation mode is set during the counting of the off-timer means. A mode control step, an operation mode in response to an external acquisition instruction, a start instruction step for starting the counting operation of the on-timer means, and a GPS signal received during the counting of the on-timer means 1st to nth transmitted in time series by the satellite A first acquisition step of acquiring a part of specific data among the n specific data, and setting a count time of the off-timer means based on the acquired specific data, and starting counting of the off-timer means An off-timer setting step; and a second acquisition step of starting counting of the on-timer means in response to the end of counting of the off-timer means and acquiring data other than the acquired specific data during the counting of the on-timer means; , An operation control step for repeating the operations of the off-timer setting step and the second acquisition step until all the n pieces of specific data are acquired, and a step of determining position information based on the acquired n pieces of specific data C. is executed.

7. The position detection method according to claim 6, wherein, as described in claim 7, n pieces of specific data from the first to the n-th data transmitted in time series by the satellite are respectively stored in n pieces. The step D is further stored in the storage means corresponding to the order of the specific data acquired from the GPS signals received in the step A, and the step C includes n storage means. The configuration may be such that the position information is determined when specific data corresponding to all of the above is stored.
7. The position detection method according to claim 6, wherein, as described in claim 8, step C is performed when any m (1 ≦ m ≦ n) th specific data is received by step A at the end of the operation mode. May be configured to calculate a time for switching from the non-operation mode to the operation mode next.
In the position detection method according to claim 6, as described in claim 9, step C includes a period in which at least one m (1 ≦ m ≦ n) specific data in the GPS signal can be received by step A. The operation mode may be controlled.
7. The position detection method according to claim 6, wherein the n specific data from the first to the n-th transmitted in time series by the satellite are the first to the fifth as described in claim 10. The sub-frame data may be configured as described above.

  According to the present invention, even when a coin-type battery or other small battery is used as a power source, a GPS voltage from a satellite can be obtained without causing a situation in which a significant voltage drop of the battery occurs and the device stops functioning. An effect is obtained that the current position can be detected by reliably receiving the signal.

  Hereinafter, a first embodiment and a second embodiment of a position detection device and a position detection method according to the present invention will be described in detail with reference to FIGS. 1 to 9. The following embodiment is an example for realizing the present invention, and the present invention is not limited to the following embodiment. That is, it goes without saying that the present invention can be variously modified by those skilled in the art as long as the technical scope of the present invention belongs.

FIG. 1 is a block diagram showing a configuration of a position detection device in each embodiment of the present invention. As shown in FIG. 1, the antenna 1, the RF unit 2, the baseband processing unit 3, the system 4, and the power source 5 are configured.
The antenna 1 receives radio waves from the satellite and inputs them to the RF unit 2. The RF unit 2 extracts and demodulates only the GPS signal from the input radio wave, amplifies it to a required level, converts it from an analog signal to a digital baseband signal, and inputs it to the baseband processing unit 3 . The baseband processing unit 3 includes a CPU 31, n search engines 32, a synchronization detection unit 33, an RF control unit 34, a RAM 35, and the like. The synchronization detection unit 33 detects a preamble that is an 8-bit synchronization signal at the head of each subframe, and inputs the start timing of the subframe to the CPU 131. The CPU 31 activates the n search engines 32 based on the preamble from the synchronization detection unit 33. Each search engine takes one subframe and stores the satellite identified by the data and the number of subframes in an internal memory (not shown). The CPU 31 stores the number of satellites and subframes stored in each of the n search engines 32 in the RAM 35 for management. That is, it is managed whether or not all of the first to fifth subframes transmitted from a predetermined number (for example, four) of satellites have been received. The RF control unit 34 controls the RF unit 2 in an operation mode or a non-operation mode according to a command from the CPU 31. In the operation mode, the clock of the RF unit 2 is enabled to enable the signal processing of the RF unit 2 described above. On the other hand, in the non-operation mode, the clock of the RF unit 2 is enabled and the signal processing of the RF unit 2 is stopped. Note that the RF control unit 34 is not necessarily configured by such a dedicated hardware system 4. A configuration in which the RF unit 2 is controlled to an operation mode or a non-operation mode by a control signal from the CPU 31 may be used. The system 4 is a clock device, for example, and displays the current time and the current position detected by the baseband processing unit 3. The power supply 5 includes a small coin-type battery (for example, 2016 type) and a DC / DC converter, and supplies power to the RF unit 2, the baseband processing unit 3, and the system 4. However, in the non-operation mode, the RF unit 2 does not consume power because the signal processing is stopped.

  FIG. 2 is a diagram illustrating a frame configuration in the GPS signal. FIG. 2A shows a main frame transmitted every 30 seconds from 32 satellites. Each main frame is composed of five subframes of subframes 1 to 5. Subframe 1 to subframe 3 are composed of unique data (referred to as “ephemeris”) in each satellite, and subframe 4 and subframe 5 are common to 32 satellites that transmit GPS signals in synchronization. It consists of data (referred to as “almanac”). When all the data of these five subframes are acquired, position information corresponding to the satellite is obtained. In order to detect the current position of this device, it is necessary to acquire position information corresponding to each of the four (at least three) satellites, so a total of 20 subframes are acquired. However, in the present invention, as will be described later, five consecutive subframes transmitted simultaneously from each satellite are divided and acquired.

  FIG. 2B shows each 300-bit subframe having a time length of 6 seconds. Usually, at the beginning of each sub-frame, there is 30-bit TLM (Telemetry) data, followed by 30-bit HOW (Handover Word) data, followed by an ephemeris such as a 240-bit clock. Data (subframe 1), ephemeris data such as detailed orbit information unique to each satellite (subframes 2 and 3), almanac data such as rough orbit information common to 32 satellites and ionospheric correction information (subframe) 4 and 5). Although not shown in the figure, the first 8 bits (10001011) of the TLM are a preamble pattern, and constitute a synchronization signal indicating the start of a subframe.

  In this way, the GPS signals from 32 satellites have the transmission timing of each subframe synchronized, and if the TLM of any subframe of any satellite is obtained, the satellite of that subframe is identified, It is possible to recognize the number of the subframe among the five subframes. Further, it is possible to predict the transmission timing of any other subframe based on the acquired TLM data of the subframe. The present invention detects the current position by utilizing such a characteristic configuration of the subframe.

FIG. 3 and FIG. 4 are flowcharts showing the position detection method of the first embodiment executed by the CPU 31.
In FIG. 3, after a predetermined initialization process (step SA1), the CPU 31 refers to the data stored in the RAM 35 and determines whether or not to give a GPS signal acquisition instruction (step SA2). When giving an acquisition instruction, the RF controller 34 is instructed to turn on RF (step SA3). In response to this instruction, the RF control unit 34 switches the RF unit 2 from the non-operation mode to the operation mode. The CPU 31 starts an internal on-timer (step SA4) and fetches data from the decoder unit of the search engine 32 (step SA5).

  Next, the CPU 31 determines whether or not establishment of synchronization is detected by the synchronization detection unit 33 (step SA6). That is, it is determined whether or not 8 bits (10001011) of the TLM preamble pattern are detected via the synchronization detection unit 33. When the synchronization establishment is not detected, it is determined whether or not the on-timer has passed a predetermined time (step SA7). In this embodiment, the predetermined time is set to 20 seconds. When the on-timer does not elapse for a predetermined time, the CPU 31 determines whether or not synchronization establishment is detected in step SA6. When the synchronization establishment is detected, the CPU 31 stores the synchronization detection timing (TLM start time) in the RAM 35. (Step SA8). Next, the CPU 31 acquires subframe data (step SA9), and determines whether or not it is correct data (step SA10). For example, when the reception environment is bad and C (carrier) / N (noise) is low, correct data cannot be obtained, so it is necessary to determine whether the acquired subframe data is correct or not.

  When it is determined that the acquired subframe data is correct, the CPU 31 stores the frame number and subframe data (satellite identification information, position information, etc.) in the subframe in the RAM 35 (step SA11). After the data store in step SA11 or when the CPU 31 determines that the acquired subframe data is not correct in step SA10, or if it cannot detect the establishment of subframe synchronization in step SA6, the CPU 31 executes step SA7. In step S1, it is determined whether the on-timer has passed a predetermined time. If the on-timer does not elapse for a predetermined time, it is determined in step SA6 whether or not the establishment of synchronization of the next subframe has been detected. Is performed (step SA12). In the initial stage where there are no subframes stored in the RAM 35, after acquiring one subframe, before the on-timer has elapsed for a predetermined time of 20 seconds, after the operation mode of about 6 seconds, RF An RF off instruction is given to the control unit 34.

  Thereafter, the CPU 31 extracts the subframe number stored in the RAM 35 (step SA13), and determines whether or not all five subframes respectively transmitted from the four satellites are prepared (step SA14). ). If all are available, the CPU 31 sends the subframe data in the RAM 35 to the system 4 (step SA15). That is, information on the current position and information on the current time obtained from the four satellites are sent to the system 4 for display.

On the other hand, if all the five subframes of each satellite are not complete in step SA14, the CPU 31 detects the missing subframe number (step SA16 in FIG. 4), and the detected subframe number. Then, the next RF on timing is calculated based on the synchronization detection timing (step SA17). Next, the CPU 31 sets a timing time obtained by calculation in the off timer (step SA18), starts the off timer (step SA19), and determines whether or not the off timer has counted up (step SA20). When the off timer counts up, the CPU 31 proceeds to step SA3 in FIG. 3 and instructs the RF control unit 34 to turn on RF.
Thereafter, the CPU 31 repeats the loop processing from step SA4 to step SA12 and step SA16 to step 20 in FIG. 4 until all the five subframes are prepared in step SA14 in FIG.

  FIG. 8A is a timing diagram illustrating an example of subframe acquisition in the first embodiment. In this figure, T is a TLM, H is a HOW, D is an ephemeris or almanac (including parity bits). In this example, an arbitrary subframe acquired first is subframe 4. Since the main frame is transmitted every 30 seconds, when the start time of the TLM preamble of subframe 4 is stored in the RAM 35 as a synchronization detection timing, 12 seconds, 42 seconds, 72 seconds after that timing, that is, T = (12 + 30 × m; m = 0, 1, 2,...) Seconds later, the TLM preamble of subframe 1 is transmitted. Therefore, considering the margin time α for stable reception, if the timing time of (T−α) is set in the off timer, the subframe 1 is surely detected when the off timer counts up and switches to RF on. Can be received. In the example of FIG. 8A, the time in the operation mode, that is, the time set in the on-timer is (18 + α) seconds. In this case, three subframes of subframes 1 to 3 can be acquired. Thereafter, the remaining subframe 5 may be acquired. For example, when switching to RF-on after (6-α) seconds or (36-α) seconds from the start time of the preamble of subframe 3 In addition, the remaining subframe 5 can be acquired.

As described above, according to the first embodiment, the RF unit 2 is intermittently switched from the non-operation mode that does not consume battery power to the operation mode that consumes battery power for a short period of time. A part of the data of the 5th subframe from the 1st to the 5th transmitted in time series by the satellite is acquired from the GPS signals received in the period, and the operation mode at another timing. At this time, the remaining subframe data is acquired, and the position information is determined based on the acquired data of the five subframes.
Therefore, even when a coin-type battery or other small battery is used as a power source, the GPS signal from the satellite can be reliably received without causing a situation where the battery voltage drops and the device stops functioning. You can receive and detect the current position.

5 to 7 are flowcharts showing the position detection method according to the second embodiment executed by the CPU 31.
In FIG. 5, after a predetermined initialization process (step SB1), the CPU 31 refers to the data stored in the RAM 35 and determines whether or not to give a GPS signal acquisition instruction (step SB2). When instructing acquisition, the RF control unit 34 is instructed to turn on RF (step SB3). In response to this instruction, the RF control unit 34 switches the RF unit 2 from the non-operation mode to the operation mode. The CPU 31 starts an internal on-timer (step SB4), and fetches data from the decoder unit of the search engine 32 (step SB5).

  Next, the CPU 31 determines whether or not establishment of synchronization is detected by the synchronization detection unit 33 (step SB6). That is, it is determined whether or not 8 bits (10001011) of the TLM preamble pattern are detected via the synchronization detection unit 33. When the synchronization establishment is not detected, it is determined whether or not the on-timer has passed a predetermined time (step SB7). Also in this case, the predetermined time is set to 20 seconds. When the on-timer does not elapse for a predetermined time, the CPU 31 determines whether or not synchronization establishment is detected in step SB6, and when synchronization establishment is detected, stores the synchronization detection timing (TLM start time) in the RAM 35. (Step SB8). Next, the CPU 31 acquires the subframe number (step SB9) and determines whether or not it is correct data (step SB10). For example, when the reception environment is poor and C (carrier) / N (noise) is low, correct data cannot be obtained, so it is necessary to determine whether the data of the acquired subframe number is correct. In the case of the first embodiment, in the initial stage where there is no subframe stored in the RAM 35, only one subframe is obtained. In this second embodiment, the subframe HOW is used. Only the included subframe numbers are acquired, and the ephemeris and almanac data are not acquired. Therefore, in the initial stage, the mode is switched to the operation mode only during a period in which data of 1.2 seconds, which is a period of TLM and HOW, can be acquired. For example, when switching from the non-operation mode to the operation mode about 0.8 seconds before the start of the TLM preamble, the operation mode time is about 2 seconds.

  When the CPU 31 determines that the acquired data of the subframe is correct, the CPU 31 instructs the RF controller 34 to turn off the RF (step SB11). When the CPU 31 determines that the acquired data of the subframe number is not correct in step SB10, or if it cannot detect the establishment of subframe synchronization in step SB6, the on-timer has passed a predetermined time in step SB7. Determine whether or not. If the on-timer does not elapse for a predetermined time, it is determined in step SB6 whether or not the establishment of the synchronization of the next subframe is detected. If the on-timer elapses for the predetermined time, the RF controller 34 is instructed to turn off the RF. (Step SB12).

  Thereafter, the CPU 31 calculates the next RF ON timing based on the detected subframe number and the synchronization detection timing (step SB13). Next, the CPU 31 sets the timing time obtained by calculation in the off timer (step SB14), starts the off timer (step SB15), and determines whether the off timer has been counted up (step SB16). When the off timer counts up, the CPU 31 instructs the RF control unit 34 to turn on RF (step SB17), starts the on timer (step SB18), and takes in data from the decoder unit of the search engine 32. Perform (step SB19).

  Next, the CPU 31 determines whether or not establishment of synchronization is detected by the synchronization detection unit 33 (step SB20). That is, it is determined whether or not a TLM preamble pattern is detected. When the synchronization establishment is not detected, it is determined whether or not the on-timer has counted up (step SB21). When the on-timer does not count up, the CPU 31 determines whether or not synchronization establishment is detected in step SB20. When the synchronization establishment is detected, the CPU 31 stores the synchronization detection timing (TLM start time) in the RAM 35. (Step SB22), the subframe data is acquired (step SB23). In step SB21, when the on-timer has counted up, the CPU 31 instructs the RF control unit 34 to turn off RF (step SB24).

  After acquiring the subframe data in step SB23, the CPU 31 determines whether the data is correct data (step SB25). If the data is correct data, the subframe number and the position of the subframe are determined. Data such as information is stored in the RAM 35 (step SB26). After storing the data in the RAM 35 in step SB26 or when determining that the data is not correct in step SB25, the CPU 31 determines in step SB21 in FIG. 6 whether the on-timer has counted up.

  After instructing the RF control unit 34 to turn off the RF in step SB24 of FIG. 6, the CPU 31 extracts the subframe number stored in the RAM 35 (step SB27), and is transmitted from each of the four satellites. It is determined whether or not all five subframes are prepared (step SB28). If all five sub-frames of each satellite are not complete, the CPU 31 detects the sub-frame number missing in the RAM 35 (step SB29), and the sub-frame detected in step SB13 in FIG. The next RF on timing is calculated from the number and the synchronization detection timing. Thereafter, the CPU 31 intermittently switches from the non-operation mode to the operation mode until all the subframes with the missing numbers are collected, and acquires the missing subframes. In step SB28 of FIG. 7, when all the five subframes of each satellite are prepared, the CPU 31 sends the subframe data of the RAM 35 to the system 4 (step SB30). That is, information on the current position and information on the current time obtained from the four satellites are sent to the system 4 for display.

FIG. 8B is a timing diagram illustrating an example of subframe acquisition in the second embodiment. In this example, the first subframe acquired is subframe 4, but only the TLM and HOW that are part of subframe 4 are acquired, and the almanac data of subframe 4 is not acquired. That is, when the reception environment is not good, the RF is switched on for a short time of about 2 seconds. Then, only the synchronization detection timing, which is the start time of the TLM preamble, and the subframe number of subframe 4 included in the HOW are stored in the RAM 35. Next, considering the margin time α for stable reception, for example, when (12−α) seconds are set in the off timer as the timing time, when the off timer counts up, as shown in FIG. Thus, subframe 1 can be acquired after RF is turned on. At this time, subframe 2 can be acquired by setting the on-timer with (12 + α) seconds as the timing time. After that, as shown in FIG. 8B, subframe 5 is acquired during the next operation mode, and thereafter, subframe 3 and subframe 4 are acquired during the next operation mode.
Note that the subframe in which only TLM and HOW are acquired is not necessarily the first subframe to be acquired as shown in FIG. If the reception environment is not good, even if there are 1 to 4 subframes already acquired, the RF is switched on for only a short time of about 2 seconds, and only TLM and HOW are acquired.

As described above, in the second embodiment, the RF unit 2 is intermittently switched from the non-operation mode that does not consume battery power to the operation mode that consumes battery power for a short period of time. A part of the data of the 5th subframe from the 1st to the 5th transmitted in time series by the satellite is acquired from the GPS signals received at the same time, and the operation mode is set at other timings. Then, the remaining subframe data is acquired, and position information is determined based on the acquired data of the five subframes.
Therefore, even when a coin-type battery or other small battery is used as a power source, it does not cause a situation in which a significant voltage drop of the battery occurs and the device stops functioning. By switching intermittently from the operation mode to the operation mode, it is possible to reliably receive the GPS signal from the satellite and detect the current position.

  In the second embodiment, only the TLM and HOW of an arbitrary subframe are first acquired. However, as a modified example of the second embodiment, only the preamble start time of an arbitrary subframe is acquired first. Then, the RAM 35 may be stored as the synchronization detection timing. In other words, when the reception environment is bad, even if the TLM and HOW of an arbitrary subframe cannot be acquired and only the preamble of the arbitrary subframe can be acquired, the number of the subframe is not known, but the stored synchronization Since the same subframe is transmitted 30 seconds after the detection timing, the operation mode time is set according to the reception environment, and subframes 1 to 5 from the satellite are acquired to detect the current position.

  As described above, even in this modification, even when a coin-type battery or other small battery is used as a power source, even when the reception environment is bad, by avoiding wasteful power consumption, a significant voltage drop of the battery is caused. The current position can be detected by reliably receiving the GPS signal from the satellite without causing a situation where the device stops functioning.

  FIG. 9 is a diagram showing a transition (discharge characteristic) of a battery voltage drop from the start of positioning to the end of positioning when a coin-type battery is used as the power source of the position detection device. After the positioning is started at the time t1 by the RF control unit 34 in FIG. 1, the battery voltage drops according to the positioning duration as shown in FIG. When the positioning is completed at time t2, the battery voltage is restored to the original. However, when the positioning time is increased until five subframes are acquired continuously as in the conventional case, when the battery voltage drops below the limit value, the variation of individual batteries can be considered. The device will no longer recover to its original voltage and will stop functioning, or it will take a long time to recover to the original voltage. End up.

  According to the result of an experiment using an unused 2016 coin-type battery at an ambient temperature of minus 10 degrees, if the operation mode time from RF on to RF off was set to 60 seconds, four positionings were possible. . On the other hand, if the operation mode time was set to 20 seconds under the same conditions, 66 positioning operations were possible. Therefore, if the operation mode time is 20 seconds and the operation is repeated three times, the operation can be performed 22 times, and the use of the battery can be improved by a factor of 5.5 compared to the case of 4 times in 60 seconds. Become.

The block diagram which shows the structure of the position detection apparatus in 1st and 2nd embodiment of this invention. The figure which shows the frame structure in a GPS signal. The CPU flowchart which shows the position detection method in 1st Embodiment. The flowchart of CPU following FIG. The flowchart of CPU which shows the position detection method in 2nd Embodiment. The flowchart of CPU following FIG. The flowchart of CPU following FIG. The timing diagram which shows an example of the sub-frame acquisition in 1st and 2nd embodiment. The figure which shows transition of the voltage drop of a coin type battery from the positioning start to the positioning end. The block diagram which shows the structure of the position detection apparatus in a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna 2 RF part 3 Baseband part 4 System 5 Power supply 31 CPU
32 Search Engine 33 Synchronization Detection Unit 34 RF Control Unit 35 RAM

Claims (10)

Power supply means for supplying power by a battery;
Receiving means for receiving a GPS signal transmitted from a satellite in an operation mode supplied with power from the power supply means, and stopping reception in a non-operation mode where power is not supplied from the power supply means;
On-timer means for counting a time shorter than the time for transmitting the main frame in the GPS signal;
Off-timer means;
A mode control means for setting the receiving means to an operation mode during the counting of the on-timer means, and a non-operation mode during the counting of the off-timer means;
In response to an external acquisition instruction, the receiving means is set to an operation mode, and a start instruction means for starting the counting operation of the on-timer means;
During the counting of the on-timer means, a part of specific data among the first to n-th specific data transmitted in time series by the satellite is acquired from the received GPS signals. First acquisition means to perform,
Off timer setting means for setting the count time of the off timer means based on the acquired specific data, and starting counting of the off timer means;
A second acquisition means for starting the counting of the on-timer means in response to the end of the counting of the off-timer means, and acquiring data other than the acquired specific data during the counting of the on-timer means;
Operation control means for repeating the operations of the off-timer setting means and the second acquisition means until all the n specific data are acquired;
And determining information determining unit position information by the acquired n pieces of specified data,
A position detection device comprising: The apparatus further includes n storage means corresponding to each of the n specific data from the first to the nth transmitted in time series by the satellite,
The information determination means stores in the storage means corresponding to the order of the specific data acquired from the GPS signals received by the reception means, and stores the specific data corresponding to all of the n storage means, The position detection apparatus according to claim 1, wherein position information is determined.   The operation control means calculates a time for switching from the non-operation mode to the operation mode next when arbitrary m (1 ≦ m ≦ n) specific data is received by the reception means at the end of the operation mode. The position detection device according to claim 1, wherein:   The operation control unit controls an operation mode during a period in which the reception unit can receive at least one m (1 ≦ m ≦ n) specific data in a GPS signal. Position detector.   The n-th specific data from the first to the n-th transmitted in time series by the satellite is the first to the fifth sub-frame data, according to claim 1, Position detection device. Step A for receiving a GPS signal transmitted from a satellite in an operation mode in which power is supplied from a power supply means for supplying power by a battery, and stopping reception in a non-operation mode in which power is not supplied from the power supply means;
A mode control step for setting the operation mode during the counting of the on-timer means for counting a time shorter than the time for transmitting the main frame in the GPS signal, and for setting the non-operation mode during the counting of the off-timer means;
In response to an external acquisition instruction, the operation mode is set, and a start instruction step for starting the counting operation of the on-timer means;
During the counting of the on-timer means, a part of specific data among the first to n-th specific data transmitted in time series by the satellite is acquired from the received GPS signals. A first acquisition step,
An off-timer setting step for setting the count time of the off-timer means based on the acquired specific data and starting counting of the off-timer means;
A second acquisition step of starting counting of the on-timer means in response to the end of counting of the off-timer means, and acquiring data other than the acquired specific data during the counting of the on-timer means;
An operation control step for repeating the operations of the off-timer setting step and the second acquisition step until all the n pieces of specific data are acquired;
A step C for determining the position information by the acquired n pieces of specified data,
Position detection method to execute. The method further includes a step D of storing n pieces of specific data from the first to the n-th time series transmitted by the satellite in time series in corresponding n storage means,
This step D is stored in the storage means corresponding to the order of the specific data acquired from the GPS signals received in the step A, and the step C is stored specific data corresponding to all of the n storage means. The position detection method according to claim 6, wherein position information is determined when the position information is detected.   In step C, when any m (1 ≦ m ≦ n) th specific data is received by the step A at the end of the operation mode, a time for switching from the non-operation mode to the operation mode is calculated. The position detection method according to claim 6.   The step C controls an operation mode during a period in which at least one m (1 ≦ m ≦ n) specific data in a GPS signal can be received by the step A. Position detection method.   The n-th specific data from the first to the n-th transmitted in time series by the satellite is the first to the fifth sub-frame data according to claim 6, Position detection method.

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