JPS63140972A - Doppler shift detector - Google Patents

Abstract

PURPOSE:To detect a Doppler shift with high accuracy by making drift components of the oscillation frequency of crystal that a transmitting and a receiving state have cancel each other. CONSTITUTION:The transmitting station A and receiving station B are provided with modulator demodulators 7. The transmitting station A measures its oscillation frequency actually, modulates a subcarrier by the modulator demodulator with a modulating signal based upon the measured frequency, and transmits the modulated subcarrier to the receiving station B with a radio wave. The receiving station B demodulates the modulated signal of the radio wave by the modulator demodulator 7 to obtain the oscillation frequency and finds the difference between it and the reception frequency of the radio wave by an arithmetic device part 6A to derive a Doppler shift.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a Doppler shift detection device, and particularly to a device for detecting a single Doppler shift using radio waves in mobile communications.

[Conventional technology]

Figure 2 is a block diagram showing a conventional Doppler shift detection device disclosed on page 1696 of "Electronic Communication Handbook" published by Ohmsha on March 20, 1978. ) is the antenna, (2) is this antenna (1)
(3) is the receiver connected to this duplexer (2), (U) is the frequency measuring device connected to this receiver (3), (r) is the duplexer (co ) is connected to the transmitter, (6) is connected to the frequency measuring device (ri) and the storage unit (
(not shown). Furthermore, the elements constituting the transmitting station (8) are not shown in FIG. 2 because they are exactly the same as those of the receiving station (B). Therefore, in the following, the elements of the transmitting station (A) corresponding to the elements of the receiving station (B) will be explained.
) do not include signs in the explanations of the elements.

In the conventional Doppler shift detection device as described above, a radio wave of the transmission frequency (f7) oscillated by the transmitter of the transmitting station (A) and transmitted via the antenna 7 is transmitted to the antenna (7) of the receiving station (B). 1) receives 4g, and transmits it to the receiver (
3). The receiver (3) band-limits the number of received signals and then sends them to a frequency measuring device (Hiro). This frequency measuring device (tI) measures the reception frequency (f, ) of the received radio wave, and transfers this reception frequency (f) to the arithmetic unit (A) as child digital data.

The oscillation frequency of the transmitter of the transmitting station (A) is stored in advance in this arithmetic unit (6) as a known frequency fi (f,). The arithmetic unit (6) calculates the known frequency tj, (f,) which is this digital data and the current frequency measuring device (<z
Doppler shift is detected by comparing the received frequency (f, ), which is digital data measured by
) and the reception frequency (f, ) is known to be given by the following equation.

f knee f7−△f, ... (1) In this example, instead of the transmission frequency (f7) of transmission &v actually transmitted from transmitting station (A), Since the transmitting frequency is stored in advance as a known frequency a(f,) at the receiving station (Fl), the known frequency (f
, ) and the reception frequency (f, ), the Doppler shift (Δr,) directly above ff″ is obtained as shown in the following equation.

f, −f, =△f7 ・ ・ ・ (
However, the reason why the reception frequency Cf,
(not shown) has an inherent oscillation frequency drift (the fluctuation range is within a certain range).

Therefore, it is actually necessary to consider the drift frequency (Δfo) caused by the drift of the oscillation frequency of the crystal.

However, if the detection method uses equation (2), the reception frequency (f
, ) will include the drift. Therefore, the calculated Doppler shift (△f) in this case needs to be given by the following formula, taking into account the above-mentioned drift frequency (△fo), in addition to the true Doppler shift (△f,). . That is, △f - △f, △fo... (3) λ In addition, the true Doppler shift (△f,) is determined by the relative velocity (VR) between the moving transmitting station (A) and receiving station (B). , ), and the following relationship is obtained (however, (
3) Among △fo and △f in the equation, the relative velocity (VRL)
It is △f and take that receive the shadow of).

△fD■■RL... (≠) [Problem to be solved by the invention] In the conventional Doppler shift detection device as described above, the relative velocity between the transmitting station (A) and the receiving station CB) When (VRL) is small, the true Doppler shift (△f0) proportional to the relative velocity (vRL) becomes small and approaches the value of the drift frequency (△f) from equations (3) and 2). Therefore, the calculated Doppler shift (△
f, ) is directly affected by the drift of the oscillation frequency of the crystal of the transmitting station (A), and the true Doppler shift (△f,
), there was a problem that the required resolution could not be obtained and the detection could not be performed correctly.

This invention was made to solve this problem, and the relative velocity (v) between the transmitting station (A) and the receiving station CB)
The present invention aims to provide a highly accurate Doppler shift detection device that can accurately detect the true Doppler shift (Δf, ) even when RL) is small. Also, the reception frequency V number (f,)
and the number of transmission frequencies (f7) include the drift (Δfo) of the unique excavation frequency of the same crystal, and when detecting Doppler shift, cancel this drift (Δfo) to obtain the true value. The purpose is to obtain a Doppler shift (△1.).

[Means for solving problems]

The Doppler shift detection device according to the present invention is installed at a transmitting station and a receiving station, and includes a transmitter that transmits radio waves, a receiver that receives radio waves subjected to Doppler shift according to the relative speed between the transmitting and receiving stations. The frequency of the transmitted 1L received radio wave was measured and the frequency of each 1L received radio wave was measured. a frequency measuring device that converts into second digital data; a modulator/demodulator that decodes the demodulated output of the multiplied radio wave by the receiver and converts it into third digital data; and arithmetic processing of the third digital data. and an arithmetic unit for detecting Doppler shift.

[Effect]

In this invention, the transmitting station measures the oscillation frequency of the transmitter and modulates the subcarrier using this and transmits it on radio waves, while the receiving station measures the transmitting frequency of the radio waves received by the receiver and The modulated signal of the subcarrier is demodulated using the aforementioned oscillation frequency, and both oscillation frequencies are compared.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the Doppler shift detection device of the present invention, and in the figure, (1) and (2)
Since it is exactly the same as the conventional example, the explanation will be omitted.

(3A) is the receiver corresponding to the receiver (,7) in Figure 2, (+A) is the frequency measuring device corresponding to the frequency measuring device (, 7), and (5A) is the transmitter (3). (6A) is an arithmetic unit corresponding to the arithmetic unit (A), and (7) is a newly added element in this invention, which is a modulation/demodulator connected to the arithmetic unit (6A). In this invention, the receiver (3A) is also connected to the modem (7), the frequency measuring device (nA) is also connected to the transmitter (5A), and this transmitter (rA) is also connected to the transmitter (5A). ) is the modem (7)
) is also connected.

In FIG. 1, like FIG. 2, only the receiving station (B) is shown in detail, and in the following explanation, the elements of the transmitting station (A) are completely different from those of the receiving station CB) Although they are the same, the reference numeral is not added for convenience to avoid confusion between the two.

In the Doppler shift detection device configured as described above, the oscillation frequency of the transmitter in the transmitting station (A) is measured by a frequency measuring device. The oscillation frequency, which includes a drift component, measured by this frequency measuring device is converted into first digital data and then sent to the arithmetic unit, and this first digital data is encoded in accordance with the transmission standard in the arithmetic unit. digitized and then sent to the modem. A modem modulates a subcarrier with this first digital data and sends the modulated subcarrier to a transmitter. The transmitter puts this modulated subcarrier on a radio wave, radiates it into space through a duplexer and an antenna, and sends it to the receiving station (B). On the other hand, at the receiving station (B), the receiving station (
B) and the transmitting station (A) due to the deviation and drift according to the relative speed (RL); The Gami wave receives the Puller shift through the antenna (1) and the duplexer (K). received by the machine (3A). Next, the reception frequency of the radio wave received by this receiver (3A) is measured by a frequency measuring device (lIA), and the measurement result is sent to the arithmetic unit (AA) as digital data.
). In addition to this, the demodulated output of the receiver (3A) is decoded by the modulator (7), that is, the modulated signal of the above-mentioned subcarrier is transmitted to the third subcarrier corresponding to the oscillation frequency of the transmitting station (A).
is decoded as digital data and sent to the arithmetic unit (6A).
sent to. The arithmetic unit (6A) converts the first digital data from the frequency measuring device (DAA) and the third digital data from the modem (RI) into destandardized data, that is, data indicating the oscillation frequency. The true Doppler shift (Δf,) is detected by taking in the difference between the two. In this way, in this invention, both the transmitting station (A) and the receiving station (B) each include a drift frequency (△fo) of the unique oscillation frequency of the crystal [in equation (1), the receiving frequency ( The drift frequency mantissa (△f
o) is considered to be included], this drift frequency (△to) is canceled by taking the difference between the two, so even if the relative velocity (■RL) of both stations becomes small, it is still true Doppler. The deviation (Δf,) will be detected.

In the above embodiment, both the receiving station (B) and the transmitting station (A) are mobile stations, but one of the stations may be a fixed station (the same effect as in the above embodiment can be achieved). .

〔Effect of the invention〕

As explained above, in this invention, a transmitting station and a receiving station each have a modulator/demodulator, and the transmitting station actually measures the excavated frequency and uses this as a modulation signal to modulate the subcarrier in the modulator and demodulator. is transmitted to the receiving station on a radio wave, and the receiving station demodulates the modulated signal of this radio wave with a modem to obtain the above-mentioned oscillation frequency, and derives the Doppler shift by taking the difference between this and the receiving frequency of the radio wave. (Since I configured it like this,
The drift of the oscillation frequency of the crystal contained in both is canceled out, and the shift lid can be detected by the actual Doppler shift received by the radio wave, which has the effect of making it possible to obtain an extremely accurate Doppler shift detection device. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional Doppler shift detection device. (1) is the antenna, (c) is the duplexer, (3A) is the receiver,
(DA) is a frequency measuring device, (5A) is a transmitter, (6A)
is an arithmetic unit section, and (7) is a modem. In addition, in each figure, the numeral 4 indicates the same or equivalent part. Procedural Judgment 1j Author (Spontaneous) May 14, 1986

Claims (3)

[Claims] (1) A Doppler shift detection device installed at a transmitting station and a receiving station, which includes a transmitter that transmits radio waves, and a receiver that receives radio waves that are Doppler shifted according to the relative speed between the transmitting and receiving stations. a frequency measuring device that measures the frequencies of the transmitted radio waves and the received radio waves and converts them into first and second digital data, respectively; A Doppler shift detection device comprising: a modulator/demodulator that converts into digital data; and an arithmetic unit that performs arithmetic processing on the second and third digital data to detect the Doppler shift. (2) The Doppler according to claim 1, characterized in that the modulator/demodulator modulates a subcarrier wave with the first digital data, and the transmitter transmits the modulated subcarrier wave on a radio wave. Deviation detection device. (3) The Doppler shift detection device according to claim 1 or 2, wherein at least one of the transmitting station and the receiving station is a mobile station.