HK1195365B - Navigation signal transmitter and navigation signal generating method - Google Patents

Description

Navigation signal transmitter and navigation signal generating method

Technical Field

The present invention relates to a navigation signal transmitter that is installed on the ground to transmit a navigation signal or a signal for positioning a receiver, and a method of generating the navigation signal.

Background

Satellite positioning systems position a receiver by passively measuring positioning signals transmitted from multiple satellites by the receiver. In this case, time synchronization is one of important technical elements, and a satellite-borne clock is used to generate a predetermined, usually continuous series of events called "epochs", the times of generation of which are encoded as random codes or pseudo-random codes (called spreading codes). The spectrum of the output signal is determined by the rate of change of the spreading code elements and the waveform of the spread signal as a result of the pseudorandom or random function of the time epoch encoding sequence. The frequencies are over a wide range. In general, the spread spectrum waveform is rectangular (rectangular) in shape, and has a power spectrum represented by a sinc function.

An example of the satellite positioning system is a Global Positioning System (GPS). Generally, the GPS operates using a plurality of frequencies, such as L1, L2, and L5, centered around 1575.42MHz, 1227.6MHz, and 1176.45MHz, respectively. These individual signals are modulated by respective spread spectrum signals. As those skilled in the art will readily appreciate, a CA (coarse acquisition) signal transmitted by the GPS satellite navigation system is broadcast at a frequency L1 of 1575.42MHz, the CA signal having a spreading code rate (chip rate) of 1.023 MHz.

On the other hand, in addition to a satellite positioning system represented by GPS, there is a ground compensation signal (imes) for the purpose of specifying position information in an indoor environment. The IMES signal is a positioning signal similar to GPS, broadcast at the same L1 frequency of 1575.42MHz, and has a spreading code rate (chip rate) of 1.023MHz that is in-line with the spreading code of the CA signal (Gold sequence).

IMES transmitters for transmitting IMES signals are often installed in buildings and underground streets, and transmit IMES signals by superimposing position information of the transmitters on the IMES signals. That is, a user having an IMES receiving apparatus receives and demodulates an IMES signal, and can know the position of the user by decoding the superimposed position information.

Here, the CA code of the IMES signal is the same as that of the GPS, and a sequence of 1023 bits (1023 chips) is repeated at a cycle of 1 ms. Therefore, in order to directly switch signals without searching for a carrier frequency and a code phase, it is necessary to make a difference between the carrier frequency and an expected value thereof within a range of 1kHz, which is the reciprocal of 1ms of a code period, and thus it is necessary to ensure accuracy within ± 500 Hz. Since 500Hz/1575.42MHz =0.33E-6, it can be considered that the frequency deviation of the clock is required to have an accuracy of about 0.2E-6(0.2ppm) or less with a slight margin. Since the length of 1 chip is about 1 μ sec, the code phase needs to have an accuracy of about ± 300ns or less.

Fig. 8 shows a case where a user having a conventional IMES receiver moves from the signal area of the conventional transmitter a to the signal area of the conventional transmitter B. When the user having IMES receiver 803 moves from the signal area (801E) of transmitter a (801) to the signal area (802E) of transmitter B (802), IMES receiver 803 also needs to switch the received signal from signal a corresponding to transmitter 801 to signal B corresponding to transmitter 802. In this way, when switching the received signal from, for example, signal a to signal b, it is desirable to reduce the interruption time of IMES signal reception as much as possible from the viewpoint of communication stability and user convenience.

Therefore, in order to reduce the signal cutoff time as much as possible, it is necessary to reduce the phase difference between the carrier frequency and the spreading code of the signal a transmitted from the IMES transmitter a (801) and the signal B transmitted from the transmitter B (802).

Here, in order to receive IMES signals, the receiver internally generates a signal called a replica signal composed of the same frequency and the same spreading code as those of the signals transmitted by the IMES transmitter, and demodulates the signal while correlating it with the broadcast signal, thereby performing reception. Fig. 9 shows a block structure of a typical positioning signal receiver. The positioning signal receiver 900 in fig. 9 includes: an antenna 901 which receives a reception signal; a reception unit 902 for performing reception processing such as amplification processing, down-conversion processing, and a/D conversion of a reception signal from the antenna 901, and processing of converting the reception signal into a digital intermediate frequency signal (digital IF signal, IF); a code replica generator 904 that generates a code replica signal; and multipliers 905 and 906 that multiply the signal from the receiving section 902 and the signal from the code replica generator 904, respectively.

Also, the positioning signal receiver 900 includes: a carrier replica generator 907 for generating a carrier replica signal within the receiver; and multipliers 908 and 909, the multipliers 908 and 909 multiplying the carrier replica signal, i.e., sin ω rt signal and cos ω rt signal, which are phase-shifted by 90 degrees from the carrier replica generator 904, by outputs of the multipliers 905 and 906, respectively, further comprising: an accumulator 910 for accumulating an output of the multiplier 908 for a predetermined period; an accumulator 911 for accumulating the output of the multiplier 909 for a predetermined period; and an arithmetic controller 912 which receives the outputs of the accumulators 910 and 911, performs accumulation for increasing S/N (accumulation before square and accumulation after square) by software, and controls the code replica generator 904 and the carrier replica generator 907 for signal addition and signal tracking.

Here, the arithmetic controller 912 can change the code generated by the code copy generator 904 by software. The arithmetic controller 912 extracts a navigation message based on the received satellite positioning signal, and performs processing such as positioning arithmetic.

In the demodulation process in the receiver, a frequency at which the broadcast carrier frequency is the same as the carrier frequency of the replica signal (more precisely, the accuracy within ± 500Hz described above) is searched for and a code phase at which the spreading code transmitted from the IMES transmitter is the same as the code phase of the spreading code of the replica signal is searched for. As shown in fig. 10, when the replica signal has the same carrier frequency and spreading code phase as the broadcast signal, the correlation value with the broadcast signal is the largest, and the broadcast signal can be received at this time.

In order to switch signals without searching for the carrier frequency and the code phase, as described above, the carrier frequency needs to have an accuracy of about 0.2E-6(0.2ppm) or less, and the code phase needs to have an accuracy of about ± 300ns or less.

Patent document 1: japanese laid-open patent publication No. 2009-85928

Patent document 2: japanese laid-open patent publication No. 2009-133731

Disclosure of Invention

Problems to be solved by the invention

In such a situation, in order for all IMES transmitters to transmit IMES signals of the same carrier frequency, low temperature dependency is required, such as small deviation of fundamental wave oscillation in the transmitters from the nominal frequency, small fluctuation of frequency, and no fluctuation of frequency due to ambient temperature fluctuation. Generally, an oscillator having such characteristics is housed in a thermostatic chamber or the like to perform strict temperature control and temperature control, and an atomic clock using atomic resonance of a certain specific frequency is used, which may result in a disadvantage that the equipment cost is high and the size thereof is large.

And, no matter how expensive the oscillator is, the frequency must change if used for a long time. Therefore, the frequency correction is required periodically.

As one method of suppressing such a long-term frequency change, there is a method of receiving a GPS signal and correcting a long-term fluctuation of an oscillator. However, if the environment is an outdoor environment, the GPS signal can be easily received, but there is a problem that the signal cannot be received in an indoor environment such as inside a building or an underground street.

As a solution to this problem, there is a solution called a GPS repeater. Is a device that introduces GPS signals received outdoors into the room through a wire and radiates them again indoors. However, when this scheme is applied to frequency synchronization of a navigation signal transmitter installed on the ground, a GPS repeater system needs to be separately introduced, and the installation and construction costs of the GPS repeater system need to be added. The GPS signal transmitted by the GPS repeater is a significant source of interference for a user who wants to receive an original GPS signal that is weak but coming from outdoors using a high-sensitivity receiver or the like.

In addition, as another scheme for achieving frequency synchronization of a navigation signal installed on the ground in an indoor environment, there is a scheme in which a timing signal is transmitted and received between transmitters by wire or wirelessly. However, when this scheme is applied to frequency synchronization of a navigation signal transmitter installed on the ground, the transmitter needs to have a transmission circuit for transmitting a timing signal in addition to the navigation signal, which causes a drawback that the number of components of the transmitter increases and power consumption increases.

A first object of embodiments of the invention of the present application is to at least reduce the problems of the prior art. The present invention relates to a method for reducing frequency deviation of a navigation signal transmitted on the ground at low cost and reliably, and the problem to be solved by the present invention is to provide a generation method thereof without requiring a high-precision and expensive oscillator which has been conventionally built in a transmitter.

A second object of the embodiments of the present invention is to match the timings of the navigation signals transmitted from the ground. The present invention is directed to a method for matching the time timing of a navigation signal transmitted on the ground with a reference, and aims to provide a method for generating a navigation signal in such a manner that the timings of a plurality of navigation signals transmitted on the ground, which are conventionally inconsistent with each other, are matched relatively, relatively and absolutely, so that the spread code phase difference between the navigation signals is reduced, and the signal acquisition time is shortened, thereby improving the convenience in reception.

Further, in view of the above-described technical problems, the present inventors have found that if the IMES signal a and the IMES signal b are the same carrier frequency and the same spreading code phase, the receiver can receive the IMES signal b without searching for the carrier frequency and the spreading code phase of the IMES signal b by using information on the carrier frequency and the spreading code phase specified by the received IMES signal a, and can smoothly switch from the IMES signal a to the IMES signal b.

Means for solving the problems

The navigation signal transmitter according to the present invention includes: a reception unit that receives a transmission wave and generates a synchronization pulse synchronized with a predetermined data frame; a reference signal synchronizing section for generating an internal clock fundamental wave oscillation using the pulse generated by the receiving section as a reference signal; an IMES signal generation unit that generates an IMES signal from the internal clock fundamental wave oscillation; and a transmission antenna that transmits the IMES signal generated by the IMES signal generation unit, wherein the reference signal synchronization unit includes a counter circuit that counts a number of pulses of a clock generated by the voltage control transmitter using a signal input from the transmission wave as a reference signal, a comparator that compares the counted value with a reference value, and a voltage control transmitter that controls to adjust a control voltage level of the voltage control transmitter when a magnitude relationship of a comparison result in the comparator is within a range within a predetermined value and continues for a predetermined number of times in one direction.

Further, the control unit may be configured to discard the count value when a magnitude relation of comparison results in the comparator exceeds a predetermined value.

Further, the comparator may be controlled to change the value to be the time constant when the magnitude relation of the comparison result exceeds a predetermined value and a value exceeding the predetermined value continues for a predetermined number of times within a predetermined time.

The navigation signal transmission method according to the present invention includes the steps of: receiving a transmission wave at a receiving unit and generating a synchronization pulse synchronized with a predetermined data frame; generating an internal clock fundamental wave oscillation in a reference signal synchronizing section using the pulse generated by the receiving section as a reference signal; an IMES signal generating unit configured to generate an IMES signal from the internal clock fundamental wave oscillation; and transmitting the IMES signal generated by the IMES signal generation unit to a transmission antenna, wherein the reference signal synchronization unit includes a counter circuit, a comparator, a low-pass control filter, a D/a converter, a voltage control transmitter, and a frequency division circuit, the counter circuit counts a number of pulses of a clock generated by the voltage control transmitter using a signal input from the transmission wave as a reference signal, the comparator compares a count value obtained by the counting with a reference value, and the comparator controls to adjust a control voltage level of the voltage control transmitter when a magnitude relationship of a comparison result in the comparator is within a range within a predetermined value and continues for a predetermined number of times in one direction.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the navigation signal transmitter or the navigation signal transmission method of the present invention, it is possible to reduce the frequency deviation of the navigation signal transmitted from the ground at low cost and reliably, and it is possible to eliminate the need for a high-precision and expensive oscillator that has been conventionally mounted on a transmitter. Further, by making the timings of the plurality of navigation signals transmitted on the ground coincide with each other relatively or relatively and absolutely, it is possible to reduce the spread code phase difference between the navigation signals, shorten the signal acquisition time, and improve the convenience in reception.

Drawings

Fig. 1 is an explanatory diagram illustrating a configuration of a navigation signal transmitter according to an embodiment of the present invention.

Fig. 2 is an explanatory diagram for explaining a block configuration of a reference signal synchronizing section in a navigation signal transmitter according to an embodiment of the present invention.

Fig. 3 is an explanatory diagram for explaining an operation of the frequency counting unit in the reference signal synchronizing unit of the navigation signal transmitter according to the embodiment of the present invention.

Fig. 4 is an explanatory diagram for explaining the frequency stability (allen standard deviation) of each signal in the reference signal synchronizing section of the navigation signal transmitter according to the embodiment of the present invention.

Fig. 5A is an explanatory diagram for explaining a configuration of a reference signal synchronizing section for acquiring time synchronization in a navigation signal transmitter according to another embodiment of the present invention.

Fig. 5B is an explanatory diagram for explaining a configuration of a reference signal synchronizing section for acquiring time synchronization in the navigation signal transmitter according to the other embodiment of the present invention.

Fig. 5C is a flowchart illustrating an operation flow in the reference signal synchronizing section for acquiring time synchronization in the navigation signal transmitter according to the other embodiment of the present invention.

Fig. 6 is an explanatory diagram for explaining a relationship between a time-of-day timing signal and a spreading code in a navigation signal transmitter according to another embodiment of the present invention.

Fig. 7 is an explanatory diagram illustrating a configuration of a navigation signal transmitter according to another embodiment of the present invention.

Fig. 8 is an explanatory diagram for explaining a case where a user having a conventional IMES receiver moves from the signal area of the conventional transmitter a to the signal area of the conventional transmitter B.

Fig. 9 is an explanatory diagram for explaining a block configuration of a receiving circuit of a conventional positioning signal receiver.

Fig. 10 is an explanatory diagram for explaining a concept of carrier frequency and code phase search of a conventional positioning signal.

Detailed Description

Next, the navigation signal transmitter and the navigation signal generating method according to the present invention will be described in detail.

Example 1

Fig. 1 shows a configuration of a navigation signal transmitter according to an embodiment of the present invention. Here, the PHS signal is assumed as "some signal (transmission wave) of the external system" in the present embodiment. The navigation signal transmitter 100 includes a PHS receiving section 101, a reference signal synchronizing section 102, an IMES signal generating section 103, and a transmitting antenna 104. Further, the PHS receiving section 101 and the reference signal synchronizing section 102 constitute an internal clock generating section (corresponding exactly to the internal clock generator 231 shown in fig. 2 of patent document 1). However, in a conventional internal clock generator such as the one shown in fig. 2 of patent document 1, an expensive OCXO (also referred to as a "temperature controlled crystal oscillator") or the like is used in order to ensure high frequency accuracy.

In the navigation signal transmitter 100, a PHS reception unit 101, which is a component of the internal clock generation unit in fig. 1, receives a PHS radio wave in a 1.9GHz band transmitted from a PHS base station, and generates a pulse of 100ms synchronized with a PHS data frame. Since the frequency offset of the PHS base station is small and a plurality of PHS base stations are synchronized, even if a clock built in a PHS receiving unit in the transmitter is deviated, the period of the PHS data frame satisfies a predetermined reference. That is, the frequency offset of the repetition frequency of the PHS data frame is small.

Here, when some signals of the external system are considered to be synchronized with the radio wave propagating through the air, a method of synchronizing with the carrier frequency of the radio wave propagating through the air, and a method of generating a timing signal based on the carrier are considered. However, since carrier frequencies may vary depending on the modulation scheme of radio waves (frequency dynamically changes such as FM modulation, FDMA, and CDMA hopping schemes), the present invention is characterized in that the carrier frequencies are synchronized not with the carrier but with the data frame period.

Next, the 100ms pulse output from the PHS receiving section 101 in fig. 1 is input to the reference signal synchronizing section 102 as a reference signal. The reference signal synchronizing section 102 generates an internal clock fundamental wave oscillation frequency synchronized with the frequency of the reference signal, and outputs the internal clock fundamental wave oscillation frequency to the IMES signal generating section 103. Instead of outputting the IMES signal to the IMES signal generation unit 103, the IMES signal may be output to a MUX232 as shown in fig. 2 of patent document 1.

Then, in the IMES signal generating unit in fig. 1, IMES signals disclosed in patent documents 1 and 2 are generated and transmitted via the transmission antenna 104.

Note here that the signal output by the PHS receiving section 101 and input as the reference signal of the reference signal synchronizing section 102 is synchronized with the PHS radio wave propagating in the air.

Note that the PHS receiving unit 101 may be a receiving unit that receives a signal other than the PHS signal (e.g., GSM, LTE, commercial power supply, etc.). Even for signals other than PHS signals, the details of the signal processing can be configured as described later. Next, the PHS signal received by the reception unit 101 will be described.

Fig. 2 shows a block diagram illustrating a detailed configuration of the reference signal synchronizing section 102. The reference signal synchronization unit 102 is composed of a frequency counter 201, a loop filter 202, and a VCO (voltage controlled oscillator) 203, and the reference signal input from the PHS receiving unit 101 is finally output to the IMES signal generation unit 103 as oscillation of the internal clock fundamental wave of 10 MHz.

Next, fig. 3 shows the operation of the frequency counter 201 in the reference signal synchronizer 102. In the frequency counter 201, a signal input from the PHS receiving section 101 is set as a reference signal of the reference signal synchronizing section 102, and the number of pulses of a clock generated by the VCO203 in the reference signal synchronizing section 102 is counted by a counter circuit (not shown) as shown in fig. 3, triggered by this signal. The counted value is compared with the number of pulses determined by the nominal frequency of the VCO203 and the nominal value of the pulse period of the reference signal in a comparator circuit (not shown), and the value as the difference is smoothed by the loop filter 202, converted into a dc voltage by appropriate gain setting and D/a conversion, and input to the VCO 203. This direct-current voltage is proportional to the frequency difference between the reference signal and the internal clock fundamental oscillation, and the VCO203 adjusts its frequency in accordance with the voltage, thereby keeping the frequency difference between the reference signal and the internal clock fundamental oscillation constant.

Here, when the nominal frequency of the VCO203 is 10MHz and the nominal value of the pulse period of the reference signal is 100ms, the number of pulses determined by the nominal frequency of the VCO203 and the nominal value of the pulse frequency of the reference signal is the number of pulses

10 x 6 x 0.1=1000000[ pulses ].

[ Effect of the navigation Signal transmitter and the like according to the present invention ]

Fig. 4 is an explanatory diagram for explaining the stability of the fundamental wave oscillation of the reference signal and the internal clock generated in accordance with the operation of the reference signal synchronizing section 102. First, in fig. 4, (a) is a typical example of the frequency stability (allen standard deviation) of the reference signal synchronizing section, that is, the PHS receiving section output signal, and (b) is a diagram showing an example of the frequency stability of the VCO single body embedded in the reference signal synchronizing section. It is known from the characteristic (a) that the reference signal is excellent in long-term frequency stability but insufficient in short-term frequency stability, and from the characteristic (b) that the VCO is insufficient in long-term frequency stability but excellent in short-term frequency stability.

As described above, the characteristic (c) shows the frequency stability of the clock signal output from the reference signal synchronizing section 102 in the navigation signal transmitter and the like according to the present invention. From the characteristic (c), it is understood that since the frequency stability in the long term is equivalent to that of the reference signal (i.e., PHS radio wave) and the frequency stability in the short term is equivalent to that of the VCO, stable performance is exhibited in a wide frequency range in the long and short term.

Example 2

Fig. 5A shows a configuration of a reference signal synchronizing section for acquiring time synchronization in a navigation signal transmitter as a second embodiment of the present invention. The reference signal synchronizing section 500 includes a phase comparing section 501, a loop filter 502, a VCO (voltage controlled oscillator) 503, and a frequency divider 504.

The signal output from the PHS receiving unit is used as a reference signal for the reference signal synchronizing unit, and the phase comparison unit 501 performs phase comparison with the signal generated by the frequency divider 504 in the PLL unit, thereby measuring the phase difference. The phase difference measured here is smoothed in the loop filter 502, converted into a direct-current voltage by appropriate gain setting and D/a conversion, and input to the VCO 503. The direct-current voltage is proportional to the phase difference between the reference signal and the frequency-divided signal, and thus the VCO503 adjusts its frequency in accordance with the voltage, thereby keeping the phase difference between the reference signal and the frequency-divided signal constant.

In this embodiment, the reference signal synchronizing section outputs, in addition to the internal clock fundamental wave oscillation, for example, a time synchronization timing signal pulse having a pulse period of an integral multiple of 1ms (for example, 10ms, 100ms, and 1000 ms. are different from the reference signal pulse in fig. 7) in order to control the timing of a PRN (pseudo random noise) code (this time synchronization timing signal pulse is supplied from 702 to 703 in fig. 7 described later).

Fig. 6 shows an example of timing control of the PRN code. Fig. 6 (a) shows a spreading code C having a cycle of 1ms generated by the IMES signal generation unit, and the time synchronization timing signal T is synchronized with the spreading code C. Fig. 6 (a) is an enlarged view of the interval T1-T2, and fig. 6 (B) is a view showing that the time timing is synchronized with the PHS radio wave by controlling the start (timing when code 1 coincides with chip 1) of the spreading code C 'having the bit number (chip number) of 1023 bits (1023 chips) to be synchronized with the pulse of the time synchronization timing signal T' and then broadcasting the signal.

Example 3

Fig. 7 shows a configuration when radio waves of a mobile phone such as GSM or LTE are used as some signals of an external system as a third embodiment of the present invention. The navigation signal transmitter 700 includes a GSM receiving unit or an LTE receiving unit (collectively referred to as a receiving unit 701) for receiving a GSM or LTE signal, a reference signal synchronizing unit 702, an IMES signal generating unit 703, and a transmitting antenna 704. That is, in the present embodiment, a GSM or LTE receiver 701 is used instead of the PHS receiver 101 to input a 10ms, 100ms, or 1000ms pulse as a reference signal to the reference signal synchronizer 702. The reference signal synchronizing section 702 may simply change the value to be compared with the number of pulses counted by the frequency counting section (not shown in fig. 7) to 10ms, 100ms, or 1000ms, and may easily use radio waves other than PHS such as GSM and LTE without changing the configuration of the transmitter other than the GSM or LTE receiving section 701.

Here, the periods (10ms, 100ms, 1000ms) of the reference signal pulses are used separately according to the environment of the communication infrastructure. For example, only a 100ms reference signal can be used in PHS and a 10ms reference signal can be used in CDMA.

Example 4

In the fourth embodiment of the present invention, a commercial power supply may be used as some of the signals of the external system. In the present embodiment, a commercial power supply receiving unit is used instead of the receiving unit 701, and a 10ms, 100ms, or 1000ms pulse is input as a reference signal to the reference signal synchronizing unit 702 in accordance with the power supply frequency (50/60 Hz in japan). Even if the power supply is a commercial power supply, the relative frequencies of IMES transmitters in a building are uniform because the power supply is the same, for example, in the building even if the absolute accuracy is poor. Thus, even in a place where radio waves such as PHS, GSM, and LTE cannot reach, the IMES transmitter can acquire frequency synchronization.

Example 5

Fig. 5B illustrates a configuration of a reference signal synchronizing section for acquiring time synchronization in a navigation signal transmitter according to a fifth embodiment of the present invention. The reference signal synchronizing section 550 includes a counter circuit 551, a holding circuit 552, a comparator 553, a filter 554 for low-pass control, a D/a converter 555, a voltage control transmitter 556, and a frequency dividing circuit 557.

The counter 551 counts the "pulse number (typically 10 MHz)" of the clock transmitted from the voltage control type transmitter (VCXO)556, and transmits a count value to the holding circuit 552 every time a reference signal pulse is transmitted, that is, every 100 ms. The count value is compared with a reference value for comparison (typically 1,000,000 times) in the comparator 553, and is ignored as an abnormal value (outlier) as a first filtering when the count value of the VCXO exceeds ± 10% with respect to the reference value.

Next, as the second filtering, when the magnitude relation of the comparison result continues to be large (+ direction) or small (-direction) n times in succession, control is performed to change the voltage control level by 1. That is, when the + direction is measured n times consecutively, the control voltage level is set to minus 1(-1) with respect to the current level, and when the-direction is measured n times consecutively, the control voltage level is set to plus 1(+1) with respect to the current level. Here, the voltage control amount corresponding to 1 level is 2.5(v)/4096(v) when the control is performed with a resolution of 12 bits.

Further, a time synchronization timing signal pulse is output from the frequency dividing circuit 557.

In fig. 5B, RIN is a reset input, CLIN is a clock input, CNTOUT is a counter value output, CNTIN is a counter value input, and STIN is a set timing input.

As described above, in fig. 5B, the comparator 553 and the low-pass control filter 554 are configured to apply a so-called random walk filter (randomwalk filter), but in the present invention, the adjustment of n (filter time constant) is characterized in that the time until convergence becomes long when the value of n is increased, and as a result of the experiment, when PHS is used as the reference signal pulse, a good result is obtained by setting n to about 10. When CDMA is used as the reference signal pulse, it is desirable that n be about 2.

Here, since the reference signal pulse has a period of every 100ms, the voltage control adjustment is performed at a rate of 1 time per 1 second when n =10, and at a rate of 1 time per 0.2 second when n = 2.

Generally, when PHS is used as the reference signal pulse, the frequency of the reference signal pulse is approximately synchronized with the frequency of the navigation signal transmitter within about 15 minutes to 30 minutes after the navigation signal transmitter is installed. However, in some cases, when a fire or the like occurs and the temperature of the navigation signal transmitter rises rapidly, it cannot be expected that the transmitter operates correctly. In this case, the frequency of the reference signal pulse is out of synchronization with the reference signal pulse, and it is necessary to quickly regain timing synchronization. Therefore, although a temperature sensor may be separately provided to detect an emergency such as a rapid temperature rise as in a fire, an additional circuit and cost are required, and thus, an emergency may be determined by detecting an abnormality in the counter value. Specifically, if the VCXO exceeds ± 10% for a predetermined time (for example, 20 seconds or 30 seconds) and continues for a predetermined number of times (for example, 100 times or 150 times), it is determined that the temperature is abnormal (emergency such as fire).

Fig. 5C shows a detailed flow in this case. When the timing synchronization is started in S501, the process proceeds to S502, and a flag (hereinafter, emergency flag) for checking whether or not there is an emergency such as a rapid temperature rise due to a fire or the like is initialized.

Next, the process proceeds to S503, where the counter counts the number of pulses transmitted from the VCXO. In S504, the time is measured from the fundamental wave oscillation of PHS, and it is determined whether or not 100ms has elapsed. If 100ms has not elapsed (no in S504), the process returns to S503, and if 100ms has elapsed, the process proceeds to S505, and it is checked whether or not the emergency flag is on. If the emergency flag is on in S505, the process proceeds to S510, and if the emergency flag is off, the process proceeds to S506.

In S506, it is determined whether VCXO is within ± 10%. If the VCXO is within ± 10%, the control voltage adjustment is performed as a normal variation (step S510), but if the VCXO exceeds ± 10%, it is determined whether the error (abnormal value) is to be discarded or the emergency is determined (step S507). In S507, it is determined whether or not the VCXO exceeding ± 10% continues for a predetermined number of times within a predetermined time. For example, it is determined whether or not the number of times is 100 times in 20 seconds or 150 times in 30 seconds. If the predetermined number of times of the operation continues for a predetermined time ("yes"), the process proceeds to S509, where it is determined that the ambient temperature rapidly increases due to an emergency such as a fire in the vicinity of the location where the navigation signal transmitter is installed, and the time constant n is changed to a value smaller than the currently set value (for example, from n =10 to n = 2). Then, the emergency flag is set to on.

In S507, if the VCXO exceeds ± 10% and is not continued for a predetermined number of times within a predetermined time, the value is discarded as an abnormal value.

In S510, when the pulse count transmitted from the VCXO shifts in the plus (+) direction, the count is incremented by 1, and when the pulse count shifts in the minus (-) direction, the count is decremented by 1, and the process proceeds to S511.

In S511, it is determined whether or not the value (+ or-) counted in S510 continues n times, and if n times continue ("yes") the process proceeds to S512, and if n times do not continue ("no"), the process returns to S502.

In S512, the control voltage is adjusted in the minus direction when the positive (+) direction is continued n times, and the control voltage is adjusted in the minus direction when the negative (-) direction is continued n times. Then, the process returns to S503.

In the flowchart shown in fig. 5C, in the case where VCXO exceeds ± 10% in S507, it is determined whether or not it continues for a certain number of times within the predetermined time, but the present invention is not limited to the case where VCXO continues for a certain time to exceed ± 10%, and the control may proceed to S509 when the number of times VCXO exceeds ± 10% within the predetermined time reaches a certain number of times, and control may be performed so that the emergency flag is turned on and the time constant n is changed to a value smaller than the currently set value. In this case, for example, when the cumulative total of the VCXO exceeding ± 10% in 3 minutes reaches 1000 times, or the cumulative total of the VCXO exceeding ± 10% in 5 minutes reaches 1000 times, the process proceeds to S509.

The procedure of determining whether VCXO exceeds ± 10% is continued for a certain number of times within a predetermined time has an advantage of being able to detect damage such as fire in a very short time. On the other hand, the flow of determining whether or not the VCXO exceeds ± 10% is accumulated a predetermined number of times within a predetermined time has an advantage that damage such as a fire can be detected in a short time to some extent while preventing an erroneous operation from being caused.

In the flowchart shown in fig. 5C, the process of turning off the emergency flag is omitted, and various processes can be considered according to the embodiment. For example, when a predetermined time has elapsed, the emergency flag is turned off, or turned off manually.

Alternatively, the emergency flag may be turned off by performing control when the VCXO converges within ± 10% a certain number of consecutive times within a predetermined time, or by performing control when the VCXO converges within ± 10% a certain number of times within a predetermined time.

It goes without saying that simple timing synchronization control without installing the above-described emergency detection logic (S502, S505, S509, and the like) can be implemented.

As described above, in the navigation signal transmitter and the like according to the present invention, focusing on the reception operation in the receiver that receives a signal based on a high-precision clock such as GPS and focusing on the problem of the navigation signal installed on the ground for improving the convenience of the receiver, an inexpensive means and method for realizing a transmitter that satisfies the above conditions are provided to overcome the problem of requiring a frequency offset of about 0.2 ppm.

Further, since the GPS is based on a high-precision clock, if it is based on natural ideas of those skilled in the art, it is easy to recognize that a high-precision clock is required even when a navigation signal used by being installed on the ground as in the GPS is generated. However, the frequency accuracy required for the navigation signal transmitters installed on the ground is not absolute, but relative frequency accuracy between the transmitters. Therefore, it is more important that each transmitter uses a common frequency standard than that the frequency standard used is highly accurate. On the other hand, it is desirable to have fewer functions and modules newly added to the navigation signal transmitter for realizing the above-described requirements. Therefore, the frequency standard of the terrestrial navigation signal transmitter can be used indoors even if it is not a property that is used as a general frequency standard, and is wider than the reachable range of the navigation signal transmitter, and a plurality of navigation signal transmitters can be used, and the following effects are obtained by using the existing standard as the frequency standard: the overall configuration of the system including the navigation signal transmitter according to the present invention can be reduced in size.

All the technical elements, methods, and processing steps described in the claims, the specification, the abstract, and the drawings can be formed as the structural elements or the constituent steps of the transmitter and the method according to the present invention by any combination except for a combination in which at least some of the elements and/or steps are mutually exclusive.

The present invention is not limited to any individual specific details of the above embodiments. The technical scope of the present invention is defined not only by the above description but also by the claims, and equivalents and modifications to the claims are also intended to be included therein.

Description of the reference numerals

100. 500: a navigation signal transmitter; 101: a PHS receiving section; 102. 702: a reference signal synchronizing section; 103. 703: an IMES signal generation unit; 104. 704: a transmitting antenna; 201: a frequency counting section; 202. 502: a circulating filter; 203. 503: VCO (voltage controlled transmitter); 501: a phase comparison unit; 504: a frequency divider; 551: a counter; 552: a holding circuit; 553: a comparator; 554: a filter for low-pass control; 555: a D/A converter; 556: a voltage control type transmitter; 557: a frequency dividing circuit; 701: a GSM or LTE reception section.

Claims (10)

1. A navigation signal transmitter includes: a reception unit that receives a transmission wave and generates a synchronization pulse synchronized with a predetermined data frame; a reference signal synchronizing section for generating an internal clock fundamental wave oscillation using the synchronization pulse generated by the receiving section as a reference signal; an IMES signal generation unit that generates an IMES signal from the internal clock fundamental wave oscillation; and a transmission antenna for transmitting the IMES signal generated by the IMES signal generation unit, wherein the navigation signal transmitter includes a plurality of antennas,

the reference signal synchronizing section is configured to connect a counter circuit, a comparator, a low-pass control filter, a D/a converter, a voltage control transmitter, and a frequency dividing circuit along a flow of a signal, wherein the counter circuit counts a number of pulses of a clock generated by the voltage control transmitter using the synchronization pulse as a reference signal, wherein the comparator compares a count value obtained by the counting with a reference value, and wherein the reference signal synchronizing section controls the voltage control transmitter to adjust a control voltage level of the voltage control transmitter when a magnitude relationship of a comparison result in the comparator is within a range within a predetermined value and continues for a predetermined number of times in one direction.

2. The navigation signal transmitter of claim 1,

when the magnitude relation of the comparison result in the comparator exceeds a predetermined value, control is performed so as to discard the count value.

3. The navigation signal transmitter of claim 2,

when the magnitude relation of the comparison result in the comparator exceeds a predetermined value and a value exceeding the predetermined value continues for a predetermined number of times within a predetermined time, control is performed to change the value to be the filter time constant of the low-pass control filter.

4. The navigation signal transmitter of any one of claims 1 to 3,

the transmission wave is a GSM wave or an LTE wave transmitted from a GSM base station or an LTE base station, the data frame is a GSM data frame or an LTE data frame, and the synchronization pulse is a pulse having a cycle of 10ms, 100ms, or 1000 ms.

5. The navigation signal transmitter of any one of claims 1 to 3,

the transmission wave is a PHS radio wave of a 1.9GHz band transmitted from a PHS base station, the data frame is a PHS data frame, and the synchronization pulse is a pulse having a period of 100 ms.

6. The navigation signal transmitter of any one of claims 1 to 3,

the transmission wave is an FM broadcast wave.

7. The navigation signal transmitter of any one of claims 1 to 3,

the transmission wave is a terrestrial digital broadcast wave.

8. A method for transmitting a navigation signal includes the steps of: receiving a transmission wave at a receiving unit and generating a synchronization pulse synchronized with a predetermined data frame; generating an internal clock fundamental wave oscillation in a reference signal synchronizing section using the synchronization pulse generated by the receiving section as a reference signal; an IMES signal generating unit configured to generate an IMES signal from the internal clock fundamental wave oscillation; and a navigation signal transmission method for transmitting the IMES signal generated by the IMES signal generation unit to a transmission antenna,

the reference signal synchronizing section is configured to connect a counter circuit, a comparator, a low-pass control filter, a D/a converter, a voltage control transmitter, and a frequency dividing circuit along a flow of a signal, wherein the counter circuit counts a number of pulses of a clock generated by the voltage control transmitter using the synchronization pulse as a reference signal, wherein the comparator compares a count value obtained by the counting with a reference value, and wherein the reference signal synchronizing section controls the voltage control transmitter to adjust a control voltage level of the voltage control transmitter when a magnitude relationship of a comparison result in the comparator is within a range within a predetermined value and continues for a predetermined number of times in one direction.

9. The method of claim 8,

when the magnitude relation of the comparison result in the comparator exceeds a predetermined value, control is performed so as to discard the count value.

10. The method of claim 9,

when the magnitude relation of the comparison result in the comparator exceeds a predetermined value and a value exceeding the predetermined value continues for a predetermined number of times within a predetermined time, control is performed to change the value to be the filter time constant of the low-pass control filter.