JP5549557B2 - Transceiver and synchronization system - Google Patents

Description

  The present invention relates to an apparatus for transmitting and receiving signals between two transmission / reception apparatuses by wire or wireless, and for synchronizing the two transmission / reception apparatuses and measuring a distance between the apparatuses.

As an apparatus for measuring the distance to an object that reflects electromagnetic waves, an apparatus described in Patent Document 1 is known. This device forms a phase-locked loop between a transmission / reception device and a reflection object, and measures the distance from the synchronization frequency at that time.
Further, as in Patent Documents 2 and 3 invented by the present inventor, two transmitting / receiving devices are used as one set, a phase-locked loop is formed between the two transmitting / receiving devices, and several hundreds of square waves of about several MHz are generated. There is known an apparatus for detecting a phase delay of a square wave of about several MHz on a high frequency carrier wave of several GHz.

JP2004-198306 JP2008-032535 JP2008-122255A

However, the method disclosed in Patent Document 1 detects a frequency that is synchronized between the transmission signal and the reception signal of the reflected wave, and measures the distance between the transmitter and the reflector from the frequency. Is the method. There is a problem that it is difficult to detect the frequency to be synchronized by sequentially changing the frequency. In the methods of Patent Documents 2 and 3, since a phase-locked loop is used between two transmission / reception apparatuses, the distance can be measured stably.
However, even if a phase-locked loop is formed between the two transmission / reception devices, if the distance between the two transmission / reception devices varies, the signal propagation delay time changes, so the two transmission / reception devices must be synchronized. I can't. For example, by transmitting a signal from a master transmission / reception device to a plurality of slave transmission / reception devices, timing cannot be synchronized in all the slave transmission / reception devices and the master transmission / reception device. If timing can be synchronized among a plurality of transmission / reception devices, channels can be allocated to each transmission / reception device by time division based on the synchronization time, and data communication can be performed without collision. In Patent Documents 2 and 3, the reciprocal distance between the transmitting and receiving apparatuses is measured, and a half of the distance is defined as the distance between both apparatuses, and the distance between both apparatuses is not directly measured.
Therefore, an object of the present invention is to realize a transmission / reception device for synchronizing timing among a plurality of transmission / reception devices.
Another object is to directly measure the distance between two transmission / reception devices and improve measurement accuracy.

The first invention transmits a first signal to another second transmission / reception device, returns the first signal received by the second transmission / reception device, and returns the second signal as a second signal. A reference oscillator that outputs a reference signal having a predetermined reference frequency, a signal oscillator that generates a transmission baseband signal, a variable phase and frequency, and a signal in a transmission / reception device that is synchronized by a phase-locked loop (PLL) A transmitter for transmitting a first signal obtained by modulating a carrier wave with a transmission baseband signal generated by an oscillator, and a receiver for demodulating a second signal received from a second transceiver to obtain a reception baseband signal A first phase comparator for detecting a first phase difference between a transmission baseband signal input to the transmitter and a reference signal output from the reference oscillator, and demodulation by the receiver A second phase comparator for detecting a second phase difference between the received baseband signal obtained from the reference signal and a reference signal output from the reference oscillator, and an absolute value difference between the first phase difference and the second phase difference is output. And a feedback control of the phase and frequency of the signal oscillator so that the output of the comparator becomes zero.

  In the present invention, when the transmitting / receiving apparatus according to the present invention transmits the first signal, the other second transmitting / receiving apparatus may be single or plural. The second transmission / reception device is a device that ideally loops back the received first signal without a delay time and sends it back as a second signal. The delay time in the apparatus is usually a processing time by a circuit. The in-device delay time is a value that is sufficiently smaller than the propagation delay time from the transmission / reception device of the present invention to the second transmission / reception device, and that is a known time that does not fluctuate. It doesn't matter. The synchronization timing between the transmitting and receiving apparatuses and the measured distance may be corrected by a known in-apparatus delay time.

  Transmission of the first signal and the second signal may be wired or wireless. In the second transmitter / receiver, when the received first signal is returned as the second signal, it is preferable to return with a carrier having a frequency different from the frequency of the carrier of the first signal. The transmission / reception apparatus according to the present invention can be recognized as a signal returned from the second transmission / reception apparatus when a second signal having a frequency different from that of the first signal is received. That is, there is no possibility of erroneously detecting, as the second signal, a reception signal due to reflection by another object of the first signal or a reception signal due to the wraparound of the first signal.

  When there are a plurality of second transmission / reception devices, it is desirable that the frequency of the carrier wave of each second signal is different between the first transmission / reception devices. That is, a frequency to be used is assigned to each second transmission / reception device, and the transmission / reception device of the present invention selects and demodulates the second signal according to the frequency, thereby the second transmission / reception device and a plurality of second transmission / reception devices. It is possible to sequentially scan and synchronize with the transmission / reception apparatus. Synchronizing with a plurality of second transmission / reception devices on the basis of this transmission / reception device means that synchronization is achieved between the second transmission / reception devices. Further, the transmitter / receiver of the present invention selects and demodulates the second signal according to the frequency, thereby sequentially scanning and measuring the distance between the transmitter / receiver and each of the plurality of second transmitter / receivers. can do.

  Further, in the second transmission / reception device, when the second signal is generated in synchronization with the reception of the first signal, the first signal that is a high-frequency signal may be simply frequency-shifted as the second signal. . That is, if the frequency of the received first signal is shifted to a frequency higher by a predetermined frequency, the sine wave of the predetermined frequency and the first signal are mixed, and the second frequency after the shift by the band-pass filter is mixed. What is necessary is just to extract a signal. Alternatively, after the first signal is demodulated and a transmission baseband signal is obtained, the carrier wave is modulated by this transmission baseband signal, and a second signal may be generated and returned.

  In another aspect of the invention, in the above invention, the distance measuring device for obtaining a distance to the second transmitting / receiving device from the first phase difference output from the first phase comparator or the second phase difference output from the second phase comparator. It is a transmitter / receiver characterized by having.

  In the above invention, the transmission baseband signal may be a square wave or a periodic pulse. Any baseband signal can be used as long as the synchronization timing is known. Besides a square wave and a pulse, a sawtooth wave, a sine wave, and the like can be used. Also, code data such as a spread code may be used. Although a periodic function is desirable for the baseband signal, it is not always necessary to be a periodic function as long as the synchronization timing is known. The modulation method may be amplitude modulation, frequency modulation, or phase modulation. Further, amplitude shift keying (ASK), frequency shift keying (FSK), and phase shift keying (PSK) may be used. The first phase difference and the second phase difference may be measured as a time difference with respect to the reference phase of the reference signal, and these phase differences include the concept of time difference.

  In addition, another invention includes a transmission / reception device according to the above-described invention and a plurality of second transmission / reception devices, and each second transmission / reception device receives a first signal and transmits each demodulated transmission baseband signal. A synchronization system characterized in that it is a synchronization signal between a plurality of second transmission / reception devices. By transmitting the first signal and receiving the second signal using the transmission / reception apparatus of the present invention, PLL synchronization can be established between the plurality of transmission / reception apparatuses. Thereby, the transmission baseband signal demodulated by each second transmitting / receiving device can be used as a timing signal for synchronization.

  In the present invention, the first signal is transmitted from the transmitting / receiving device according to the present invention to the second transmitting / receiving device. In the second transmitter / receiver, the first signal is returned as a second signal. In this transmission / reception apparatus, the second phase difference θ2 that is the phase difference between the received baseband signal obtained by demodulating the second signal and the reference signal is measured. Further, a first phase difference θ1 that is a phase difference between the transmission baseband signal and the reference signal is measured. Then, the phase of the transmission baseband signal is advanced with respect to the reference signal so that the absolute values of the first phase difference θ1 and the second phase difference θ2 are equal. Now, based on the phase of the reference signal, the phase of the transmission baseband signal is θ1 (positive value) and the phase of the reception baseband signal is θ2 (negative value). θ1 and θ2 are defined with the leading phase being positive and the lagging phase being negative with respect to the reference signal.

  The second transmitter / receiver has no delay time from the reception of the first signal to the transmission of the second signal, and the delay phase amount of the transmission baseband signal generated by the propagation delay time between the transmitter / receiver and the second transmitter / receiver is Δφ (correct Value). Then, the phase of the transmission baseband signal with respect to the reference signal when the first signal is received by the second transmission / reception device is θ1−Δφ. Furthermore, the phase is delayed by Δφ while propagating as the second signal from the second transmitting / receiving device to the transmitting / receiving device. Therefore, the phase of the received baseband signal obtained by demodulating the second signal with this transmission / reception apparatus is θ1-2Δφ. This phase becomes equal to the phase θ2 of the received baseband signal. Therefore, θ1-2Δφ = θ2 is established.

  The phase θ1 of the transmission baseband signal is feedback controlled so that the absolute values of the first phase difference θ1 and the second phase difference θ2 are equal. Therefore, since θ1 = −θ2, θ1 = Δφ. That is, from the first phase difference θ1 or the second phase difference θ2, the distance L between the transmission / reception apparatus and the second transmission / reception apparatus is obtained by L = cθ1 / (2πf). Where c is the speed of light and f is the frequency of the transmission baseband signal. In this manner, the distance between the two devices can be directly and accurately obtained in a state where PLL synchronization is applied between the present transmitting / receiving device and the second transmitting / receiving device.

  In the second transceiver, the phase of the transmission baseband signal obtained by demodulating the first signal with respect to the reference signal is θ1−Δφ as described above. As described above, θ1 = Δφ when the PLL synchronization is applied so that the absolute values of the first phase difference θ1 and the second phase difference θ2 are equal. Therefore, the phase of the transmission baseband signal obtained in the second transceiver is the same as that of the reference signal output from the reference oscillator of the transceiver. If such PLL synchronization is established between the present transmission / reception device and the plurality of second transmission / reception devices, a transmission baseband signal obtained by demodulating the first signals received by all the second transmission / reception devices. Is synchronized with the reference signal. As a result, synchronization can be established between the present transmitting / receiving device and all the second transmitting / receiving devices at different distances. Therefore, for example, time division multiplex communication can be performed by assigning each time slot to a plurality of second transmission / reception devices on the basis of the synchronized transmission baseband signal.

The block diagram of the transmitter / receiver which concerns on the specific Example 1 of this invention. The block diagram of the 2nd transmission / reception apparatus which communicates with the transmission / reception apparatus which concerns on Example 1. FIG. FIG. 3 is an explanatory diagram illustrating a relationship between a phase of a transmission baseband signal and a phase of a reception baseband signal in a state where PLL synchronization is established with a second transmission / reception device in the transmission / reception device according to the first embodiment. FIG. 6 is a configuration diagram of a system according to a second embodiment. FIG. 10 is an operation explanatory diagram of a transmission / reception apparatus that controls transmission frequency and reception frequency by time division according to the third embodiment.

  Hereinafter, specific embodiments of the present invention will be described with reference to block diagrams. The present invention is not limited to the following examples.

FIG. 1 is a configuration diagram of a transmission / reception apparatus 1 according to the present invention. The reference oscillator 10 is an oscillator that oscillates a 1 MHz square-wave reference signal S0. The reference signal S0 output from the reference oscillator 10 is input to the first phase comparator 11 and the second phase comparator 12. A transmission baseband signal B 1 output from the voltage controlled oscillator 17 is input to the first phase comparator 11. As described later, the transmission baseband signal B1 is a square wave that is frequency-synchronized with the reference signal S0 and phase-synchronized so that the phase difference becomes a predetermined value. The transmission baseband signal B 1 output from the voltage controlled oscillator 17 is input to a modulator (mixer) 18. The reference signal S0 output from the reference oscillator 10 is input to the PLL voltage controlled oscillator 19, and the PLL voltage controlled oscillator 19 generates a sine wave obtained by multiplying the frequency of the reference signal S0 based on the reference signal S0 as a carrier wave. To do. This carrier wave is input to the modulator 18, and the carrier wave is amplitude-modulated by the modulator 18 using the transmission baseband signal B 1. The signal output from the modulator 18 is input to the band-pass filter 20 and only the upper sideband of the modulation signal is extracted. The output signal of the band pass filter 20 is amplified by the amplifier 22 and then radiated to the space as the first transmission signal S1 through the transmission antenna 21.

  The second transmitting / receiving device 2 will be described later, but it is assumed that the second transmitting / receiving device 2 receives the first signal, simply shifts the frequency, and returns the second signal S2. The second signal S2 is received by the receiving antenna 30, and the received signal is amplified by the amplifier 31 and then input to the demodulator 33. The demodulator 33 is a synchronous demodulator, generates a demodulated carrier wave having a frequency synchronized with the carrier wave of the second signal S2, and synchronously demodulates the second signal S2 with the demodulated carrier wave. The output signal of the demodulator 33 passes through the band pass filter 34 and is input to the second phase comparator 12 as a reception baseband signal B2. The reception baseband signal B2 is a square wave, the same frequency as the transmission baseband signal B1, and a signal delayed by a predetermined phase.

  The second phase comparator 12 detects the second phase difference θ2 between the reception baseband signal B2 and the reference signal S0. The second phase difference θ2 is defined as the phase of the received baseband signal B2−the phase of the reference signal. That is, it is the phase of the received baseband signal B2 when the phase of the reference signal is 0 degree. A negative value of θ2 represents a delayed phase. The second phase comparator 12 is composed of a flip-flop circuit as is well known. A pulse signal having a width proportional to the phase difference of the received baseband signal B2 with respect to the reference signal S0 is output. When the reception baseband signal B2 and the reference signal S0 are in phase, the output of the second phase comparator 12 is a square wave with a duty ratio of 50%, and the reception baseband signal B2 is only π with respect to the reference signal S0. When the phase is advanced, a square wave with a duty ratio of 100% (high level direct current) is obtained, and when the received baseband signal B2 is delayed in phase by π with respect to the reference signal S0, the duty ratio is 0. % Square wave (low level direct current). The output signal of the second phase comparator 12 is input to a low pass filter (loop filter) 14 and smoothed (averaged). The output level of the low-pass filter 14 gives the second phase difference θ2. As will be described later, the phase of the reception baseband signal B2 is always delayed with respect to the reference signal S0. Therefore, the second phase difference θ2 is a negative value. Therefore, in the inverter 16, the signal level is inverted, and the absolute value of the second phase difference θ2 is obtained. That is, the output signal of the inverter 16 gives the absolute value (−θ2) of the second phase difference.

  Similarly, a reference signal S0 and a transmission baseband signal B1 are input to the first phase comparator 11. The first phase comparator 11 has the same configuration as the second phase comparator 12 and performs the same function. Therefore, when the transmission baseband signal B1 and the reference signal S0 are in phase, the output of the first phase comparator 11 is a square wave with a duty ratio of 50%, and the transmission baseband signal B1 is compared with the reference signal S0. When the phase is advanced by π, a square wave with a duty ratio of 100% (high level direct current) is obtained, and when the transmission baseband signal B1 is delayed by π with respect to the reference signal S0, the duty is It is adjusted to be a square wave (low level direct current) with a ratio of 0%. The output signal of the first phase comparator 11 is input to a low pass filter (loop filter) 15 and smoothed (averaged). The output level of the low-pass filter 15 gives the first phase difference θ1. As will be described later, the phase of the transmission baseband signal B1 always advances with respect to the reference signal S0. Therefore, the first phase difference θ1 is a positive value. For this reason, the output level of the low-pass filter 15 gives the absolute value (θ1) of the first phase difference θ1.

比較器１３の出力信号は、電圧制御発振器１７の制御端子に入力している。Δθが正の場合には、電圧制御発振器１７の出力する送信ベースバンド信号Ｂ１の位相を進めて、比較器１３の出力Δθが０となるようにフィードバック制御される。また、Δθが負の場合には、電圧制御発振器１７の出力する送信ベースバンド信号Ｂ１の位相を遅らせて、比較器１３の出力Δθが０となるようにフィードバック制御される。このようにして、比較器１３の出力Δθが、常に、０となるように、送信ベースバンド信号Ｂ１の位相は制御されることになる。すなわち、送受信装置１と第２送受信装置２との間で、ベースバンド信号に関してＰＬＬ同期が確立したことになる。 The absolute value θ1 of the first phase difference and the absolute value of the second phase difference (−θ2 ≧ 0) are input to the comparator 13. The output of the comparator 13 calculates a difference Δθ between the absolute value of the second phase difference and the absolute value of the first phase difference. Therefore, the following equation is established.

The output signal of the comparator 13 is input to the control terminal of the voltage controlled oscillator 17. When Δθ is positive, the phase of the transmission baseband signal B1 output from the voltage controlled oscillator 17 is advanced, and feedback control is performed so that the output Δθ of the comparator 13 becomes zero. When Δθ is negative, feedback control is performed so that the phase of the transmission baseband signal B1 output from the voltage controlled oscillator 17 is delayed and the output Δθ of the comparator 13 becomes zero. In this way, the phase of the transmission baseband signal B1 is controlled so that the output Δθ of the comparator 13 is always 0. That is, PLL synchronization is established between the transmission / reception device 1 and the second transmission / reception device 2 with respect to the baseband signal.

第１位相差θ１と第２位相差θ２の絶対値は等しくなる。この同期をした時の第１位相差θ１と第２位相差θ２の関係を図３に示す。 In a state where PLL synchronization is established, Δθ which is the output of the comparator 13 is zero. That is, the following equation is established.

The absolute values of the first phase difference θ1 and the second phase difference θ2 are equal. FIG. 3 shows the relationship between the first phase difference θ1 and the second phase difference θ2 when this synchronization is performed.

Next, the first phase difference θ1 and the second phase difference θ2 in this state represent the distance between the transmission / reception device 1 and the second transmission / reception device 2. Now, in the second transmitting / receiving apparatus, it is assumed that the delay time in the apparatus is zero until the second signal is returned after receiving the first signal. The propagation delay time from the transmission device 1 to the second transmission / reception device is Δt, and the frequency of the transmission baseband signal B1 is f. A phase difference Δφ corresponding to the delay time Δt is expressed by the following equation.

第１信号Ｓ１が伝搬して、第２送受信装置２で受信された時の送信ベースバンド信号Ｂ１の位相φ３は、次式で表される。

第２送受信装置２では、この送信ベースバンド信号Ｂ１の位相は保持されて、第２信号Ｓ２として、送受信装置１に返信される。送受信装置１において、この第２信号Ｓ２を復調して得られる受信ベースバンド信号Ｂ２の位相φ２は、さらに、Δφだけ遅延するので、次式で表される。

The phase of the reference signal S0 is φ0. Then, the phase φ1 of the transmission baseband signal B1 at the output terminal of the voltage controlled oscillator 17 is expressed by the following equation.

The phase φ3 of the transmission baseband signal B1 when the first signal S1 propagates and is received by the second transceiver 2 is expressed by the following equation.

In the second transmission / reception device 2, the phase of the transmission baseband signal B1 is held and returned to the transmission / reception device 1 as the second signal S2. In the transmission / reception device 1, the phase φ2 of the received baseband signal B2 obtained by demodulating the second signal S2 is further delayed by Δφ, and is expressed by the following equation.

（２）式の関係があるので、θ１、θ２に関して、次式が成立する。

すなわち、送受信装置１と第２送受信装置２との間でＰＬＬ同期が確立している状態では、第１位相差θ１と第２位相差θ２とは、送受信装置１と第２送受信装置２の間の伝搬遅延時間Δｔに基づく位相差を表す。送受信装置１と第２送受信装置２間の距離をＬとすると次式が成立する。

Since the second phase difference θ2 is a phase difference of the phase φ2 of the received baseband signal B2 with respect to the phase φ0 of the reference signal, it is expressed by the following equation using the equation (6).

Since there is a relationship of formula (2), the following formula is established for θ1 and θ2.

That is, in a state where PLL synchronization is established between the transmission / reception device 1 and the second transmission / reception device 2, the first phase difference θ1 and the second phase difference θ2 are between the transmission / reception device 1 and the second transmission / reception device 2. Represents the phase difference based on the propagation delay time Δt. When the distance between the transmission / reception device 1 and the second transmission / reception device 2 is L, the following equation is established.

  In this way, the distance L between the transmission / reception device 1 and the second transmission / reception device 2 can be measured using the first phase difference θ1 or the second phase difference θ2. For this purpose, the output of the low-pass filter 15 is input to the distance calculation device 70. The distance calculation device 70 is a device that performs the calculation of equation (9), and is configured by a computer system. Thus, after the PLL synchronization is established between the transmission / reception device 1 and the second transmission / reception device 2, even if the distance between the two fluctuates in time, the PLL synchronization is continued. The distance between the two can be measured continuously.

The second transmitting / receiving device 2 is a device that receives the first signal S1, simply converts the frequency, and transmits it as the second signal. The frequency converter can be composed of a mixer and a band pass filter.
The signal oscillator in the present invention is composed of a voltage controlled oscillator 17, and the transmitter in the present invention includes a modulator 18, a PLL voltage controlled oscillator 19, a reference oscillator 10, a band pass filter 20, an amplifier 22, and a transmitting antenna 21. It is configured. The receiver according to the present invention includes a receiving antenna 30, an amplifier 31, a band pass filter 32, a demodulator 33, and a band pass filter.

  Next, another configuration example of the second transmission / reception device 2 will be described. In FIG. 2, the first signal S1 received by the receiving antenna 51 is amplified by the amplifier 52 and then input to the band-pass filter 53 that extracts the carrier band of the first signal S1. The first signal S1 output from the band-pass filter 53 is synchronously demodulated by a synchronous demodulator 54 configured by a Costas loop or the like, and input to a band-pass filter 55 for extracting a baseband band. The output signal of the band pass filter 55 becomes the transmission baseband signal B1. The transmission baseband signal B1 is input to the modulator 56. A square wave having a frequency f 2 is input from the fixed frequency oscillator 58 to the PLL voltage controlled oscillator 57. In the PLL voltage controlled oscillator 57, a sine wave having a frequency Mf2 is generated by multiplying the frequency of the square wave by a predetermined number of times. The output of the PLL voltage controlled oscillator 57 is input to the modulator 56 as a carrier wave. The frequency of this carrier is different from the frequency f1 of the carrier of the received first signal, and is a frequency uniquely assigned to the second transceiver 2. The carrier wave of the frequency Mf2 is amplitude-modulated by the transmission baseband signal B1 by the modulator 56, input to the band pass filter 59 that passes only the upper side band wave, amplified by the amplifier 60, and then as the second signal S2. Radiated from the transmitting antenna 61 into space. The second signal S2 is received by the transmission / reception device 1, and PLL synchronization is established as described above.

  When PLL synchronization is established between the transmission / reception device 1 and the second transmission / reception device 2, the phase of the transmission baseband signal B1 obtained by demodulation by the second transmission / reception device 2 is φ3 = φ0 + θ1-Δφ according to the equation (6). However, since θ1 = Δφ is established, φ3 = φ0. That is, the transmission baseband signal B1 obtained by being demodulated by the second transmission / reception device 2 is a signal that is phase-synchronized with the same frequency as the reference signal S0 of the transmission / reception device 1. Thereby, synchronization can be established between the transmission / reception device 1 and the first transmission / reception device 2. As described above, after the PLL synchronization is established between the transmission / reception device 1 and the second transmission / reception device 2, even if the distance between the two fluctuates with time, the PLL synchronization is continued. A common reference signal S0 can be obtained and synchronized between the transmission / reception device 1 and the second transmission / reception device regardless of the fluctuations.

  In the present embodiment, as shown in FIG. 4, distance measurement and synchronization establishment are possible when a plurality of second transmission / reception devices 2 exist for one transmission / reception device 1. The transmission / reception device 1 includes transmission basebands such as the first phase comparator 11, the second phase comparator 12, the comparator 13, the voltage control oscillator 17, the modulator 18, the PLL voltage control oscillator 19, and the demodulator 33 shown in FIG. The number n of the second transmission / reception devices includes a modulation system that generates the signal B1 and the first signal S1, and a demodulation system that demodulates the second signal S2 to obtain the reception baseband signal B2. And the frequency of the carrier wave of 1st transmission signal S1 is allocated to each system | strain F1-Fn. The frequencies F1 to Fn are uniquely assigned to the second transmission / reception devices A1 to An, respectively. Each second transmitting / receiving apparatus is configured using a band-pass filter or the like so that the first signal S1 other than the frequency allocated to itself can not be frequency-shifted or demodulated. The frequencies of the carrier waves of the second signal S2 returned by the second transmitting / receiving devices A1 to An are respectively assigned to unique values of Mf1 to Mfn.

  Each demodulator 33 of the transmission / reception apparatus 1 is configured to select and demodulate the second signals S2 of these frequencies Mf1 to Mfn using a band pass filter. With such a configuration, PLL synchronization can be established even when the distance between the transmission / reception device 1 and the plurality of second transmission / reception devices A1 to An varies with time. As a result, the distance between the transmission / reception device 1 and each of the second transmission / reception devices A1 to An can be continuously measured in real time even if the distance varies with time. Further, even if the distance between the transmission / reception device 1 and each of the second transmission / reception devices A1 to An varies with time, the phase of the transmission baseband signal B1 demodulated by the second transmission / reception devices A1 to An is always the reference signal S0. Can be synchronized with the phase of That is, in all of the transmission / reception device 1 and all the second transmission / reception devices A1 to An, the synchronization signal can be obtained even if the distances thereof fluctuate, and synchronization can be established. Thereby, time division multiplex communication is realizable by assigning a time slot to each 2nd transmission / reception apparatus A1-An on the basis of a synchronizing signal.

  In the third embodiment, the modulation and demodulation systems of the transmission / reception device 1 are not provided in parallel in n systems as in the second embodiment, but are divided into n time intervals, and each of n frequencies F1 to Fn is sequentially provided. This is an embodiment in which the transmission of the first signal S1 and the reception of the second signal S2 having the frequencies Mf1 to Mfn are repeated. As shown in FIG. 5, the transmission / reception device 1 executes the PLL synchronization establishment with each of the second transmission / reception devices A1 to An in order by repeatedly changing the transmission frequency and the reception frequency. In the case of the present embodiment, each of the second transmission / reception devices A1 to An establishes PLL synchronization only with each time interval with the transmission / reception device 1. In each time interval, the distance between each of the second transmission / reception devices A1 to An and the transmission / reception device 1 is measured. Accordingly, distance measurement can be obtained discretely in time, but by shortening one cycle of frequency change, the distance can be varied with time, and distance measurement in real time becomes possible.

  Each of the second transmission / reception devices A1 to An is provided with a synchronous oscillator that oscillates a synchronization signal synchronized with the transmission baseband signal B1 obtained by demodulation when the PLL is established. This synchronous oscillator always stores the oscillation frequency and phase in a register. The synchronous oscillator can be composed of, for example, a digital synthesizer. In the time interval in which PLL synchronization is performed, the frequency difference and phase difference between the transmission baseband signal S1 and the synchronization signal obtained by demodulation are fed back by an update pulse or an absolute value, and the register value is always Updated. Thereby, PLL synchronization is established. In this synchronous oscillator, the feedback signal is not input and the value of the register is not updated except during the time interval in which PLL synchronization is established. Therefore, this synchronous oscillator oscillates a synchronization signal in synchronization with the frequency and phase held in the register at the end of the time interval for establishing PLL synchronization except for the time interval for establishing PLL synchronization.

  In this way, by configuring the synchronous oscillator of the second transmission / reception device, PLL synchronization with the transmission / reception device 1 can be established in a time-sharing manner. In all of the transmission / reception device 1 and the second transmission / reception devices A <b> 1 to An, a synchronization signal can be obtained and establishment of synchronization can be realized even if their distances fluctuate. In addition, when a synchronization signal is obtained in a plurality of second transmission / reception devices, if the synchronization signal is obtained once by PLL synchronization establishment, even if the distance to the transmission / reception device 1 changes with time, the first 2 The phase of the synchronization signal in the transmitting / receiving device is not affected by the distance. Therefore, as described above, if the synchronization signal is generated using a digital synthesizer and periodically synchronized with the transmission baseband signal B1 transmitted from the transmission device 1, the phase of the synchronization signal can be finely adjusted. good.

  The present invention can be used for distance measurement between a plurality of transmission / reception devices and synchronization establishment.

DESCRIPTION OF SYMBOLS 1 ... Transmission / reception apparatus 2 ... 2nd transmission / reception apparatus 11 ... 1st phase comparator 12 ... 2nd phase comparator 13 ... Comparator 17 ... Voltage controlled oscillator

Claims (4)

The first signal is transmitted to another second transmission / reception device, and the first signal received by the second transmission / reception device is looped back and returned as a second signal, whereby a phase lock is established with the second transmission / reception device. In a transmission / reception device that is synchronized by droop ,
A reference oscillator that outputs a reference signal of a predetermined reference frequency;
A signal oscillator of variable phase and frequency that generates a transmit baseband signal;
A transmitter for transmitting the first signal obtained by modulating a carrier wave with the transmission baseband signal generated by the signal oscillator;
A receiver that demodulates a second signal received from the second transceiver to obtain a received baseband signal;
A first phase comparator for detecting a first phase difference between the transmission baseband signal input to the transmitter and the reference signal output from the reference oscillator;
A second phase comparator for detecting a second phase difference between the received baseband signal obtained by demodulation by the receiver and the reference signal output from the reference oscillator;
A comparator that outputs a difference in absolute value between the first phase difference and the second phase difference;
The transmission / reception apparatus, wherein the phase and frequency of the signal oscillator are feedback-controlled so that the output of the comparator becomes zero.   A distance measuring device for obtaining a distance to the second transmitting / receiving device from the first phase difference output from the first phase comparator or the second phase difference output from the second phase comparator. The transmission / reception apparatus according to claim 1.   The transmission / reception apparatus according to claim 1, wherein the transmission baseband signal is a square wave or a periodic pulse.   A transmission / reception device according to any one of claims 1 to 3 and a plurality of the second transmission / reception devices, wherein each of the second transmission / reception devices receives and demodulates the first signal. A synchronization system, wherein each transmission baseband signal is a synchronization signal between the plurality of second transmission / reception devices.

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