JPH0823577B2 - GPS receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION INDUSTRIAL FIELD OF APPLICATION The present invention is a global positioning satellite system, NAVSTAR.
(Navster) GPS for positioning using satellite radio waves
(GPS: Global Positioning System) Related to receivers.

Recently, GPS receivers have attracted attention in the field of navigation. This GPS receiver is, for example, “GDM / GPS Receiv
er Hardware Implementation ”(GDM / GPS receiver hardware implementation: NAECON 1977,303-309) and other multi-channel methods and“ Applications of a Malt ”.
iplexed GPS User Set "(GLOBAL POSITIONING SYSTEM vol.II 1984,61
-77) and the like are known. Hereinafter, referring to FIG. 7 to FIG. 10, conventional GPS
The receiver will be described.

FIG. 7 is a block connection diagram showing the configuration of a conventional multi-channel GPS receiver. In FIG. 7, 2
Is an antenna for receiving the radio wave of the satellite 1, 3 is a preamplifier for amplifying the received signal, 4 and 5 are local oscillators and mixers for frequency-converting the output signal of the preamplifier 3, and 6 is an output from the mixer 5. A bandpass filter for filtering the intermediate frequency signal to be generated, 7 is an amplifier for amplifying the output of the bandpass filter 6, 9 is a controller for demodulating the signal of the amplifier 7 and converting it into a digital signal.
The four demodulators 10 and 10 are pseudo noise generators for despreading the spread spectrum signal from the satellite. Reference numeral 11 is a numerically controlled oscillator that reproduces a carrier wave. Reference numeral 12 is a numerically controlled oscillator that generates the timing of the output signal of the pseudo noise generator 10, and the control unit 8 is the two numerically controlled oscillators.
11 and 12 are controlled, and the position of the antenna 2 is calculated from the received signal.

The operation of the above configuration will be described below.

First, the omnidirectional antenna 2 receives radio waves from four satellites, amplifies them with a preamplifier 3, and frequency-converts them with an output signal of a local oscillator 4 by a mixer 5. This signal is band-limited by the band filter 6 and then amplified by the amplifier 7. The gain of the amplifier 7 is adjusted by the control unit 8. This output signal includes signals from four satellites, which are individually separated and demodulated by the four demodulators 9, digitized into about 8 bits, and output to the controller 8. Separation of satellites is carried out by outputting in parallel a Gold code of 1023 chip length, which is unique to each satellite, generated by the pseudo noise generator 10 and obtaining the correlation with these four signals. Further, it corresponds to the Doppler shift of the satellite signal due to the relative speed between the receiver and the satellite, and of the numerically controlled oscillator 11 which regenerates the carrier wave for receiving the data sent from the satellite by the two-phase modulation. The signal is supplied to the demodulation unit 9. Further, the phase of the Gold code output from the pseudo noise generator 10 is controlled independently of the four satellites via the numerical control oscillator 12 under the control of the control unit 8. The oscillation frequency of the numerically controlled oscillator 11 is also controlled by the control unit 8.

Further, the control unit 8 reads the data sent from each satellite from the output of the demodulation unit 9 and obtains the orbital elements of each satellite and the coarse portion of the GPS time which is the reference of the satellite in 1 msec unit. Furthermore, the detailed GPS time of each satellite is obtained from the phase of the Gold code. The satellites in orbit are very accurately time-aligned, with four GPS signals showing the received signal.
The position of the receiving point is obtained by solving a simultaneous equation using the time, the propagation time of the radio wave, and the position of the satellite as the unknown three-dimensional position of the receiving point and the GPS time at the receiving point.
The obtained position can be output as data to the outside.

FIG. 8 is a block connection diagram for explaining the demodulation unit 9 in more detail.

First, the output of the amplifier 7 shown in FIG.
And 9-2, the phase shifter 9-3 performs orthogonal transformation.
The mixer 9-1 outputs a component in phase with the carrier wave of the received signal, and further, in the mixers 9-4, 9-5 and 9-6, the Gold code generated by the pseudo noise generator 10 shown in FIG. The correlation between the central phase, the slightly advanced phase, and the slightly delayed phase is calculated, and the reception of the transmitted data and the advance / delay of the Gold code generated by the receiver are detected. On the other hand, the output of the mixer 9-2 obtains the correlation between the central phase of the Gold code and the mixer 9-7, obtains the phase difference between the received signal and the reproduced carrier wave output from the numerically controlled oscillator 11, and performs the numerical control. The frequency of the oscillator 11 is controlled by the control unit 8.
The outputs of the mixers 9-4 to 9-7 are sequentially scanned by the switch 9-12 via the low-pass filters 9-8 to 9-11, digitally converted by the A / D converter 9-13, and controlled. It is output to the unit 8.

Next, another GPS receiver according to the conventional multiplex system will be described with reference to FIG.

In FIG. 9, as in FIG. 7, 2 is an antenna for receiving the radio wave of the satellite 1, 3 is a preamplifier for amplifying the received signal, and 4 and 5 are frequency conversion of the output signal of the preamplifier 3. A local oscillator and a mixer, 6 is a bandpass filter for filtering the intermediate frequency signal output from the mixer 5, 7 is an amplifier for amplifying the output of the bandpass filter, 29 is a signal for sequentially demodulating this signal for four satellites in a time division manner. Then, the demodulation section 30 outputs the pseudo-noise to the control section 28, the pseudo-noise generator 30 generates pseudo-noise for despreading the spread spectrum signals specific to each of the four satellites in a time-division manner, and 31 denotes the four satellites. It is a numerically controlled oscillator that sequentially generates a carrier wave. Reference numeral 32 is a numerically controlled oscillator that outputs the output timing of the pseudo noise generator 30 for each of the four satellites. The control unit 28 controls these two numerically controlled oscillators 31 and 32 to position the antenna 2 from the received signal. To calculate.

The operation of the above configuration will be described below. The basic operation is the same as that of FIG.
There is only one 29, and it receives four satellites in sequence. The demodulation unit 29 has the same configuration as that shown in FIG. 8, but the pseudo noise generator 30 and the numerically controlled oscillator 31 sequentially output signals for each of the four satellites at fixed time intervals. FIG. 10 illustrates the timing at which the demodulator 29 receives the satellites indicated by SV1 to SV4, and FIGS. 10 (a), (b), (c),
(D) is the filter 9-8, 9-11, 9 of FIG.
It corresponds to the output signals of -9 and 9-10. Also, FIG. 10 (a)
(D) outputs signals of the same satellite at the same timing.

The phase Φ is determined with the carrier wave output from the numerically controlled oscillator 31 as a reference, and the phase difference from the gold code generated by the pseudo noise generator 30 at the central timing is defined as τ. Figure 10 (a) shows the phase Φ
Is 0 ° and the phase difference τ is 0 chip.
Φ is 90 ° and τ is 0 chip signal, FIG. 10 (c) is Φ or 0 ° and τ is 1/2 chip signal, and FIG. 10 (d) is Φ 0 ° and τ The timing of switching the satellites when mixing the 1/2 chip signal with the signals from the satellites is shown. The phase difference between the carrier signal and the pseudo noise code between the signal from the satellite and the signal generated in the receiver is detected by the four kinds of signals shown in FIGS. 10 (a) to 10 (d), and the results are used to detect the satellite. By tracking the signal, it is possible to receive the transmitted data and to determine the time when the satellite emitted the radio wave.

Problems to be Solved by the Invention In the configurations shown in FIGS. 7 and 8, the differences between the signals generated by the four satellites and the signals internally generated are constantly observed for each of the four satellites. It is possible to measure the time when the satellite actually emitted the radio wave. However, four demodulators shown in FIG. 8 are required, the circuit scale becomes large, and the receiver becomes large,
There has been a problem that the power is increased and the cost is increased.

On the other hand, with regard to the configurations shown in FIGS. 9 and 8, only one demodulation unit in FIG. 8 is required, and the circuit scale can be small.
Since the timing for switching satellites is commonly applied to each satellite as shown in Fig. 10, the data signal sent from the satellite and the switching of the receiving satellite are not synchronized.
It is very difficult to detect the change timing of the data signal that shows the satellite time in seconds. Also, if you look at one moment, you are observing only one satellite,
There is a drawback that it takes a long time to track the satellite signal.

The present invention is intended to solve such problems of the prior art, and is intended to be small in size, low in power, inexpensive, easy to catch the timing of data transmission, and shorten the time until the satellite signal is tracked. To do.

Means for Solving the Problems The present invention provides pseudo noise generating means for simultaneously generating pseudo noise signals corresponding to radio waves of two or more satellites, and carrier waves respectively corresponding to radio waves of the two or more satellites. In order to individually demodulate the signals of the plurality of satellites and the oscillating means which are simultaneously generated, the first pseudo noise generating signal generated by the pseudo noise generating means is mixed with the radio waves of the two or more satellites. A mixer, a second mixer for mixing one carrier wave generated by the oscillating means with the radio waves of the two or more satellites, and a filter for filtering the final output from the first and second mixers. A plurality of demodulating means, and switching control of the phase of the pseudo noise generated by the pseudo noise generating means and the carrier wave generated by the oscillating means by time division, and the phase switching control timing is
It is an object of the present invention to achieve the above object by providing control means for switching control in synchronization with the timing of change of the data signal of each satellite received by each demodulation means.

Operation The present invention has one or two demodulating means for each satellite, and compares the phase of the received signal with the phase of the carrier wave and pseudo noise code generated in the receiver by time division using each demodulating means. By providing a means for measuring and tracking the phase difference and reducing the number of mixers and filters in this demodulating means to simplify, the timing for switching the phase of the carrier wave and the pseudo noise signal in the demodulating means is improved. The above object is achieved by synchronizing the demodulation means with the change timing of the data signal sent from the satellite which is received.

First Embodiment A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block connection diagram of a GPS receiver according to the first embodiment of the present invention.

In FIG. 1, 2 is an antenna for receiving radio waves from four satellites 1, 3 is a preamplifier for amplifying the received signals, and 4 is a preamplifier.
Reference numerals 5 and 5 denote a local oscillator and a mixer for frequency-converting the output signal of the preamplifier 3, 6 is a bandpass filter for filtering an intermediate frequency signal from the output signal of the mixer 5, and 7 is an amplifier for amplifying the output signal of the bandpass filter 6. , 49 are four demodulators for demodulating the signal of the amplifier 7, 49-12 are switches for sequentially switching the output signals of the demodulator 49, and 49-13 are sequential analog outputs of the demodulator 49 via the switch 49-12. -A / D converter for digital conversion, 48 controls a numerically controlled oscillator 51 and a numerically controlled oscillator 52, which will be described later, in accordance with the output digital signal of the A / D converter 49-13, as well as the GPS receiver. A control unit that calculates and outputs the position, 50 is a pseudo noise generator that outputs the pseudo noise code unique to each of the four satellites that it receives to the demodulation unit 49, and 51 is the regenerated four for demodulating the data. Numerically controlled oscillation that outputs the carrier waves of each satellite to the demodulation unit 49 , 52 is a numerically controlled oscillator in parallel output corresponding to the pseudo noise generator 50 four hygiene code output timing.

FIG. 2 is a block connection diagram for explaining the demodulation unit 49 of FIG. 1 in more detail.

In FIG. 2, 49-1 is a mixer for mixing the output signal of the amplifier 7 and the output signal of the numerically controlled oscillator 51, and 49-4 is a mixer for mixing the output of the amplifier 49-1 and the output of the pseudo noise generator 50. Reference numeral 49-8 is a low-pass filter that passes only the low-frequency signal component demodulated from the output of the mixer 49-4.

The operation of the above configuration will be described below.

First, radio waves of four satellites are received by the omnidirectional antenna 2, amplified by the preamplifier 3, and the amplified signal and the output of the local oscillator 4 are mixed by the mixer 5, and the received signal is frequency-converted. To do. The converted signal is added to the bandpass filter 6 to remove unnecessary components. The band filter 6 has a frequency band of 2 MHz, and a signal (C / A code) modulated by a Gold code made with a clock of 1.023 MHz passes without distortion. The output of the bandpass filter 6 is amplified by the amplifier 7. The gain of the amplifier 7 is controlled by the controller 48 so that the dynamic range is widened. The amplified signals include the signals of all satellites received by the antenna 2. The output signal of the amplifier 7 and the carrier wave reproduced by the numerically controlled oscillator 51 are mixed by the mixer 49-1 shown in FIG. 2, and the received signal is dropped to the base band. Further, the correlation between this signal and the Gold code peculiar to the satellite generated by the pseudo signal generator 50 is obtained by the mixer 49-4. The Gold code is used to identify the satellite. From the output of the mixer 49-4, a change rate of 20 msec is demodulated as a data signal indicating satellite time through a low-pass filter 49-8 having a cutoff frequency of 1 KHz and a transfer rate of 20 msec. The signals of four satellites synchronized with this are independently demodulated by the demodulation unit 49. The demodulated output signal of the low-pass filter 49-8 is A / D-converted by the A / D converter 49-13 sequentially through the switch 49-129 which switches at a cycle of 1000 μsec, and the output is received to the control unit 48. Detects the phase difference between the pseudo noise code phase and the reproduced carrier wave and controls the numerically controlled oscillator 51 and the numerically controlled oscillator 52 to track the satellite signal. Furthermore, the control unit 48 uses a pseudo noise generator 50.
By measuring the time when each satellite emits radio waves by tracking the carrier wave, and receiving the orbit information of the satellite and the data related to the time, etc., the three-dimensional position where the antenna 2 is installed can be determined. You can ask.

FIG. 3 illustrates the change in the output of the low-pass filter 49-8, which is obtained when the phase of the pseudo noise code is changed, and the horizontal axis represents the phase of the Gold code output by the pseudo noise generator 50. The vertical axis represents the output of the low-pass filter 49-8 obtained when the phase of the data signal sent from the satellite by BPSK matches the phase of the numerically controlled oscillator 51.

However, the vertical axis in FIG. 3 (d) is the result of obtaining the absolute value of the correlation outputs of FIGS. 3 (b) and 3 (c) and obtaining the difference between the former and the latter. The broken line indicates the phase of the pseudo noise code that matches the phase of the pseudo noise code included in the satellite signal. The Gold code generated in the pseudo noise generator 50 outputs a signal having three types of phases. That is, with the signal at the center timing as a reference, the phase difference from this is defined as τ, and this signal distinguishes these signals. Phase difference τ of output signal is 0 chip, 1/2 chip, -1/2
There are three types of chips.

FIG. 3A shows the phase difference τ output by the pseudo noise generator 50.
Is an output obtained by mixing the signal of 0 chip and the signal from the satellite. The phase difference τ is 1/2 in Figs. 3 (b) and (c).
This is the output obtained by mixing the chips and -1/2 chips and the signals from the satellites. Therefore, FIGS. 3 (a), (b) and (c) correspond to the correlation results between the satellite signal and the signal generated by the receiver. As shown in Fig. 3, Fig. 3 (a) shows a phase that matches the phase of the satellite signal, Fig. 3 (b) shows a phase delayed by 1/2 chip, and Fig. 3 (c) shows a chip advanced by 1/2 chip. Maximum amplitude in phase. Figure 3 (a), (b) and (c)
, The BPSK data signal has the same phase as the numerically controlled oscillator 51. The positive and negative of the signal are inverted by the data sent from the satellite, and the control unit 48 reads this to receive the data. Further, when the difference between the absolute values of FIGS. 3 (b) and 3 (c) is positive, the phase of the Gold code output from the pseudo noise generator 50 is advanced, and when it is negative, it is delayed. As described above, by controlling the control unit 48 via the oscillation frequency of the numerically controlled oscillator 52,
Tracking is performed so that it has a phase shown by a broken line in FIG. 3, that is, a phase that coincides with the pseudo noise code included in the satellite signal.

Also, the carrier wave signal output from the numerically controlled oscillator 51 is based on a signal that is in phase with the carrier wave of a satellite signal, and Φ, which is the phase of this signal, is determined, and two kinds of signals, Φ being 0 ° and 90 °, are output. To do. The signal output from the numerically controlled oscillator 51 is
It is independent for each of the four satellites it receives, but for each satellite it selectively outputs a signal with either Φ of 0 ° or 90 °. Similarly, the pseudo noise generator 50 that outputs three types of signals also selectively outputs one of the three phase differences for each satellite over time. FIG. 4 is a diagram showing combinations of these output signals and timings for changing the combinations.

More specifically, FIGS. 4 (a) to 4 (d) show satellite SV1.
4 to 4 show timings for changing combinations of output signals. For each satellite, the types of output signals of the numerically controlled oscillator 51 and the pseudo noise generator 50 are changed at individual timings, and the correlation result is obtained by another demodulator 49. The signals corresponding to FIGS. 3 (a), (b), and (c) are Φ = 0 ° and τ = 0, Φ = 0 ° and τ = 1 /, respectively.
2. Measure at the timing of combination of Φ = 0 ° and τ = -1 / 2.

The phase is switched every 5 msec. The demodulator 49 obtains the correlation result of the combination of Φ = 90 ° and τ = 0 and the combination of Φ = 0 ° and τ = 0, and the amplitude of the correlation result of the combination of Φ = 90 ° and τ = 0 becomes small. As shown in FIG.
Control and track the carrier wave of the satellite signal.

 As described above, the carrier wave and the pseudo noise can be tracked.

FIG. 5 illustrates the relationship between the timing of switching the phase and the transmission timing of the data sent from the satellite. The data sent has a cycle of 20 msec and 1 m
The phase relationship with the pseudo-noise code having a period of sec is fixed, and is related to the satellite time.

FIG. 5 (a) shows the timing at which the transmitted data changes from 0 to 1. To capture this timing,
It is important for knowing the time when the radio wave being received is emitted from the satellite.

FIG. 5B shows the timing of changing this data and the timing of changing the phase of the pseudo carrier and the reproduced carrier wave. Here, the vertical solid line is the timing at which the phase is changed, and the broken line is the timing at which the pseudo noise code makes one round and the next starts.

FIG. 5 (c) shows the output of the low-pass filter 49-8, which is supposed to be able to track the carrier of the satellite signal and the pseudo noise code, and Φ = 0 ° and τ = 1 / shown in (b). In the period of 2, the amplitude is about half of the maximum, the maximum amplitude is in the period of Φ = 0 ° and τ = 0, and is approximately zero in the period of Φ = 90 ° and τ = 0. In the portion where the data in (a) changes from 0 to 1, the positive / negative of the signal is inverted in the state of maximum amplitude. Thus, Φ = 0
The timing of changing the combination of the output signals is changed so that the changed portion of the data comes during the period in which the maximum amplitude is 0 and τ = 0. Once this timing can be found, since the cycle is set to 20 msec, it matches the bit rate at which the data is sent, and after that, this relationship can be maintained continuously. Even if the signal is weak and it is impossible to determine whether or not the timing relationship is established at one time, it can be easily determined by repeatedly examining the timing relationship. Also, since the timing to change the combination of output signals is set independently for each satellite, it is possible to easily and quickly find the part where the data changes, and 1 msec
You can know the satellite time of. Switch 49-12 and A / D
The converter 49-13 sequentially measures the outputs of the four demodulation units 49 at a fixed timing, but it only needs to have a rate sufficient to measure the signal shown in FIG. 5 (c).

As is clear from the above description, according to this embodiment,
The demodulation unit 49 is provided with the same number of four as the satellite 1, and the demodulation unit 49 has a simple structure of two mixers 49-1 and 49-4 and a filter 49-8. As shown, the pseudo noise and the phase of the reproduced carrier are switched in time sequence, and at the timing when the data signal sent from each satellite that is tracking this switching timing changes, the output of the demodulator becomes the maximum amplitude, By switching in synchronism with the data signal, it is possible to reliably capture all the satellites that are tracking the data of the satellites whenever necessary. In addition, similarly to the conventional multi-channel receiver shown in FIG. 7, the time when the radio waves of each satellite are emitted can be quickly obtained. Moreover,
Since the structure of the demodulation unit 49 is greatly simplified, it is possible to obtain an inexpensive, compact and lightweight receiver equivalent to the multiplex system shown in FIG.

 Next, a second embodiment of the present invention will be described.

FIG. 6 illustrates the timing of changing the combination of the signals output by the numerically controlled oscillator 51 and the pseudo noise generator 50 according to the second embodiment of the present invention. The structure of the receiver is the same as that of the first embodiment, and the difference is that the timing of switching the phase shown in FIG. 6 is different. Less than,
This timing will be described.

FIG. 6 (a) shows the timing at which the data sent from the satellite is inverted. FIGS. 6 (b), (c), and (d) show timings for switching phases. 6 (b) and 6 (d) are enlarged views of the 10 msec period shown in FIG. 6 (c), and the output is switched at intervals of 2 msec. Also, the entire cycle is 10 msec, which is matched to the transmission rate of the data signal sent from the satellite. In FIG. 6 (b), the combination of output signals is set so that the center of the 2 msec period, which is a combination of Φ = 0 ° and τ = 0 chips, coincides with the timing at which the data in FIG. 6 (a) is inverted. Change the timing to change. In this change operation, it is possible to easily and quickly find the portion where the data changes. In FIG. 6 (d), Φ = 90
In the period in which the combination of ° and τ = 0 chips, the carrier frequency of the satellite signal and the phase of the numerically controlled oscillator 51 are compared, and the oscillation frequency of the numerically controlled oscillator 51 is controlled so that the amplitude of the correlation result becomes small. Track the satellite signal carrier.
Furthermore, Φ = 0 °, τ = 1/2 chip period and = 0 °, τ
By comparing the correlation results in the period of = −1 / 2 chip, the phase of the Gold code output from the pseudo noise generator 50 is controlled, as in the first embodiment, and the pseudo noise included in the satellite signal is controlled. Follow the code. The period of τ = 1/2 chip and τ = −1 / 2 chip at Φ = 0 ° is the period for measuring the phase difference of pseudo noise.

As described above, according to the present embodiment, since the time during which the pseudo noise that affects the position measurement accuracy is measured is longer than that in the first embodiment and the conventional multiplex method, the positioning result is stable from the start of tracking. It takes less time, and accuracy is easy to obtain even when the observation point moves at an accelerated rate. Moreover, it can be realized with a circuit scale equivalent to that of the multiplex system.

As described above, as is apparent from the first and second embodiments, the demodulator 49 having a simple structure is used, and the pseudo noise and the reproduced carrier wave are tracked with respect to the signal from the satellite in a time division manner. By providing a plurality of demodulation units 49 having the structure so that signals of different satellites can be independently demodulated, the transmission timing of data sent from the satellites can be detected quickly and easily.

In the above description, the circuit of FIG. 2 is described as being included in the demodulation unit 49 one by one, but it may be included in two. As a result, although the circuit scale increases, the tracking performance of the carrier wave and the pseudo noise code can be improved. When the demodulation unit 49 is doubled to improve the tracking performance of either the carrier wave or the pseudo noise code, the demodulation unit 49 of the same satellite shares the same function part,
It is also possible to eliminate some circuits. The order of the mixers 49-1 and 49-4 may be reversed. Alternatively, the pseudo noise and the reproduced carrier wave may be mixed in advance, and the mixed signal and the received signal from the satellite may be mixed.

The timing for switching the phases of the pseudo noise and the reproduced carrier wave has been described with reference to FIGS. 4 and 6, but the timing is not limited to this.

As described above, according to the present invention, the demodulation means is simplified, and the simplified demodulation means detects the pseudo noise and the error of the reproduced carrier in a time division manner, and the signal of one satellite is tracked to one demodulation means. By providing a plurality of such simplified demodulation means, the time division is used for tracking at independent timings, and a plurality of satellites are tracked at the same time. Data transmission timing can be calculated in parallel at the same time. Moreover, the time when radio waves are emitted from a plurality of satellites can be quickly determined, and the position can be obtained, which is a great effect.

[Brief description of drawings]

FIG. 1 is a block connection diagram of a GPS receiver in the first embodiment of the present invention, FIG. 2 is a block connection diagram of a demodulation section in a main part of FIG. 1, and FIG. 3 is a pseudo in the configuration of FIG. FIG. 4 is a diagram showing the correlation output of a noise signal, FIG. 4 is a timing diagram in the configuration of FIG. 1, FIG. 5 is a more detailed timing diagram, and FIG. 6 is a timing diagram in the second embodiment of the present invention. The figure shows the block diagram of the conventional GPS receiver, No. 8
FIG. 9 is a block connection diagram of a demodulation unit which is a main part of FIG.
FIG. 10 is a block diagram of another conventional GPS receiver, and FIG. 10 is a timing diagram of the GPS receiver of FIG. 49 ... Demodulator, 49-1 ... Mixer, 49-4 ... Mixer,
49-8 ... Low-pass filter, 49-12 ... Switch, 49
-13 ... A / D converter, 50 ... Pseudo noise generator, 51 ... Numerically controlled oscillator.

Claims (3)

[Claims] 1. Pseudo noise generating means for simultaneously generating pseudo noise signals respectively corresponding to radio waves of two or more satellites, and oscillating means for simultaneously generating carrier waves respectively corresponding to radio waves of the two or more satellites. A first mixer for mixing the pseudo-noise generation signals generated by the pseudo-noise generation means with the radio waves of the two or more satellites to individually demodulate the signals of the plurality of satellites, and the two or more satellites. A second mixer that mixes the carrier wave generated by the oscillating means with the radio wave of 1., a plurality of demodulating means configured by a filter that filters the final output from the first and second mixers, and the demodulating means by time division. The phase of the pseudo noise generated by the pseudo noise generating means and the phase of the carrier wave generated by the oscillating means are switched and controlled, and the phase switching control timing is controlled by the demodulator of each satellite received by the demodulator. GPS receiver and a control unit for switching control in synchronism with the timing of change of the data signal. 2. The phase of pseudo noise generated by the pseudo noise generating means is switched to a center phase, a lead phase, and a lag phase, and in this center phase, the in-phase and quadrature phase of a carrier wave generated by the oscillating means are sequentially switched. The GPS reception according to claim 1, wherein the vicinity of the center of the period when the phase of the pseudo noise is the central phase and the phase of the carrier wave is in-phase is synchronized with the timing when the data signal from the satellite changes. Machine. 3. The method according to claim 2, wherein the frequency of switching the phase of the pseudo noise generated by the pseudo noise generating means is set higher than the frequency of switching the carrier wave generated by the oscillating means. GPS receiver.