JPS5853871B2 - Decca receiver phase calibration method - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a phase calibration method for a DETSUKA receiver used in a DETSUKA navigation system, and in particular to a phase calibration method that enables phase calibration without using a dedicated oscillator for calibration. be.

In the Detsuka navigation system, the ground transmitting stations are usually centered on the main station and three slave stations arranged in a star shape, each with a common frequency]f (1f214M■) harmonics (for example, the main station is 6f, the slave station is 5f, 8f, 9f) while maintaining a constant phase relationship.

The Detsuka receiving station (for example, a ship) receives radio waves from the main station and each slave station, multiplies the frequency of each by the least common multiple of 1 to make the same frequency, and then compares the phases.
The position of the own station is measured as the intersection of hyperbolic points based on the phase difference between the main station and each slave station.

In this way, the Detsuka navigation system measures the position of its own station from the phase difference between the radio waves from the main station and slave station.
When the DETSUKA receiving station is located at a distance between the main station and the slave station whose distance difference is an integral multiple of the transmission wavelength, and the radio waves from both stations are in the same phase, the DETSUKA receiving equipment installed at the DETSUKA receiving station The phase difference indicator must be adjusted to show zero phase difference.

In reality, the phase of the receiver is calibrated prior to position measurement.

As a method, a phase calibration signal consisting of a pulse signal with a sharp frequency of 1f so that all the harmonic signals have the same phase is applied to the receiving input terminal, and the harmonic signals of 5f, 6f, 8f and 9f are selectively amplified. A method is used to adjust the local signal phase of each slave receiving channel so that each phase difference indicator all shows a zero phase difference.

Figure 1 shows a conventional Detsuka receiver and a phase calibration signal generator used therein, showing a main station (reception frequency 6f) and one slave station (reception frequency 5f). However, since the configurations and operations of the other slave stations are similar to this, their description is omitted.

In Figure 1, 1 is an antenna, SL is a changeover switch that switches between "operation" and "calibration", 2 is a high frequency amplifier that selectively amplifies the main station's radio wave 6f, and 3 is a generator that generates a local oscillation signal with a frequency of 6△. Multiplier 4 mixes 6f from high frequency amplifier 2 and 6△ from multiplier 3 to obtain a frequency of 6F (6F=6△-6
5 is a narrowband intermediate frequency amplifier with a center frequency of 6F.

Further, 6 is a phase discriminator, 7 is a vCO (voltage controlled oscillator) as a periodic oscillator that generates a frequency of 6F, and 8 is a phase discriminator 6 that is proportional to the phase difference between the output 6FR of the intermediate frequency amplifier 5 and the output 6FO of the vCO7. Take out the DC component and convert it to vCO
With a low-pass filter applied to 7, by the configuration of vCO7
The phase of the output 6FO is controlled, and in the synchronized state, there is a 90° gap between the output 6FO and the intermediate frequency output 6FR as shown in FIG.
The signal has a frequency of 6F and has a phase difference of .

The characteristics of the button phase discriminator 6 are as shown in FIG.
The output is zero at a phase difference of 0.degree., and the output has a maximum negative and positive value at 0.degree. and 180.degree.

In this way, vCO7 becomes a phase synchronized oscillator that operates as an active filter for intermediate frequency output 6FR, and high output 6FO having a 90° phase difference with 6FR is stably generated.

As described above, the high frequency amplifier 2 to the low pass filter 8 form the main station reception channel.

Similarly to the main station reception channel, the slave reception channel that selectively amplifies the frequency 5f includes a high frequency amplifier 9 that selectively amplifies the frequency 5f, and a multiplier/phase shifter 1 that generates a local oscillation signal of the frequency 5Δ.
0 (the phase shift function will be explained later), intermediate frequency 5FC
5F=5Δ-5f), a mixer 11.5F, a narrow band intermediate frequency amplifier 12 for amplifying the 5F, and a phase discriminator 13.5.
It consists of a VCO14 as a synchronous oscillator that oscillates F and a low-pass filter 15.

In the synchronous state, VCOl 4 is the output 5 of the intermediate frequency amplifier 12.
Generates an output 5Fo having a 90° phase difference with respect to FR.

Next, 16 is a 5x transmitter, and 17 is a 6x transmitter, which makes the output 6Fo of vCO7 and the output 5F of VCOl 4.
o will both be multiplied by the same 30F.

18 is a phase discriminator, 19 is a phase difference indicator, and if each multiplied wave 30F of 6Fo of the main station receiving channel and 5Fo of the slave station receiving channel is in phase, the phase difference indicator 19 will show zero.

Then, 5f is input to each receiving channel of the master station and slave station.
When the radio waves of and 6f are in the same phase, it is necessary that each 30F multiplied by the intermediate frequency output 5FO16FO of both receiving channels is in the same phase, but in reality, the shift within each receiving channel of the main station and slave station is Since the phase amounts are different, they are not necessarily in phase.

Therefore, by controlling the multiplier/phase shifter 10 by the phase adjuster 20 and adjusting the phase of the local oscillator signal 5, Δ, the phase of the intermediate frequency output 5Fo, that is, the output 30F of the multiplier 17 is adjusted.
Calibrate so that the phase is the same as that of 30F on the main station receiving channel side.

In addition, 21 is a local source oscillator that oscillates at a fixed frequency, 22
is a frequency synthesizer, and 23 is a receive chain setter. The receive chain setter 23 generates a signal with a frequency corresponding to the radio waves of each digital transmitting station, and applies it to the frequency synthesizer 22 together with the frequency of the local source oscillator 21. and synthesizes the local oscillator fundamental wave frequency 1△.

This 1△ corresponds to the above-mentioned relationship, that is, the radio wave 6f from the transmitting station
, 5f, 6F-6Δ-6f, 5F=5Δ-5
It was set to satisfy f.

Next, to explain the phase calibration signal generator part, 2
4 is a vCO125 that generates a frequency of 8F, is a 1/8 frequency divider, 26 is a phase discriminator, 27 is a low-pass filter, and 28 is a 6
1/1 frequency divider, 29 is a mixer, 30 is a pulse shaper, S
2 is the same "operation" and "calibration" changeover switch as Sl.

In this configuration, when the changeover switches S1 and 82 are on the "operation" side, vCO24 is outputted via the phase discriminator 26 to the output 6Fo of vCO7, similar to vCO7 and VCO14 described above.
It oscillates at a frequency of 8F, which is phase-synchronized with.

During "operation", this 8F has no involvement in the operation of the master/slave receiving channel.

If you synchronize the output of vCO24 and the output of vCO7 in advance during operation, you can not only shorten the time required to pull the output of vCO7 to the output of vCO24 during calibration, but also
It is possible to prevent the lane value being accumulated from being affected.

That is, it is possible to prevent the decometer from rotating and retracting during calibration.

If the outputs of the vCO 24 are synchronized in advance, there is no need to reset the lanes.

Even if it is necessary to reconfigure lanes, it will only take about ± lanes.

When you switch the Detsuka receiver from "operation" to "calibration",
The output of the phase discriminator 26 is disconnected from the vCO 24, but the vCO 24 retains the frequency and phase just before it was switched to "calibration."

The output 8F of this VCO 24 is divided into 1F by the frequency divider 25, and then the local oscillator fundamental wave frequency 1△ is output from the frequency synthesizer 22.
The fundamental wave component 1f of the received signal is mixed in the mixer 29 with
The pulse shaper 30 generates a calibration pulse with a frequency exactly equal to 1f, which is further converted by the pulse shaper 30 into a calibration pulse with a narrow frequency 1f.

Since the harmonic components 5f, 6f, 8f, and 9f of the calibration pulse are in a relationship of equal amplitude and equal phase, respectively (the calibration pulse is shaped sufficiently sharply), these harmonic components are connected to each other via the changeover switch S1. If the phase adjuster 20 is adjusted so that the phase difference indicator 19 shows a zero phase difference in addition to the main and slave receiving channels, the zero phase calibration of the Detsuka receiver has been performed correctly.

At that time, the output of VCO 7 and intermediate frequency amplifier 5 is 9
The phase difference is 0°.

However, such a conventional phase calibration device has the following drawbacks.

(1) It requires an extra VCO 24 for calibration and a phase discriminator 26 for phase synchronizing this oscillator.

(2) Since the VCO 24 performs free-running oscillation during calibration, the frequency shift and phase drift during the calibration period appear as a calibration signal frequency difference, and since calibration is performed with a frequency signal different from the received signal, the phase There is a risk that the calibration will be inaccurate.

To prevent this, an expensive crystal controlled oscillator is required to stabilize the VCO 24.

(3) VCO2 with good stability over a wide range of ambient temperatures
In order to synchronize 4 with VCO7, it is necessary to precisely control the temperature coefficient of each crystal oscillator.
It becomes expensive.

In other words, the difference in temperature coefficient tends to make the operation unstable.

Therefore, in order to improve the conventional drawbacks, the present invention uses VCO 7 (not necessarily VCO 7) forming an active filter as its 11 calibration oscillation source,
By providing a voltage-controlled phase shifter that shifts the phase of the VCO 7 output in order to form a 90° phase difference between the VCO 7 output and the intermediate frequency output, the calibration VCO 24 and phase discriminator 26 are unnecessary. It is an object of the present invention to provide a phase calibration method that performs the following steps.

For this reason, in the phase calibration method of the digital receiver according to the present invention, a master station reception channel, a slave station reception channel, and a synchronous oscillator provided corresponding to at least one of these reception channels and synchronized with the reception signal. and a phase calibration method for a DETSUKA receiver equipped with a phase synchronization means and a local oscillation signal synthesis means, the output of a synchronous oscillator provided in one of the reception channels is added to another phase control means, Furthermore, the phase control signal from the phase control means of the same receiving channel is added to the above-mentioned another phase control means, and based on the output from the another phase control means and the local oscillation output from the above-mentioned local oscillation signal synthesis means, an equivalent signal for calibration is obtained. The present invention is characterized in that a received signal is generated and in addition to each receiving channel, the input/output amount phase of each receiving channel is calibrated.

An embodiment of the present invention will be described below based on FIG.

In the figure, the same reference numerals as in other countries indicate the same parts.

A voltage-controlled phase shifter 31° DC amplifier 32 as a phase control means, a 1/6 frequency divider 34 that generates a square wave for a low-pass filter 33.1F, an "operation" and "calibration" changeover switch 83, etc. , which is mainly new to FIG.

Referring to Fig. 4, when the selector switches S1 and S3 are on the "operation" side, the master station/slave station reception channels select and receive 6f and 5f, and the phase difference is displayed, as in the case of Fig. 2. Do this.

The output 6F of the VCO 7 has a phase difference of 90° with respect to the intermediate frequency output 6FR.

When the changeover switches S1 and S3 are switched to "calibration", the VCO 7 stores and holds the frequency and phase immediately before switching.

On the other hand, the voltage-controlled phase shifter 31 receives the output of the phase discriminator 6 of the main station receiving channel via the DC amplifier 32 and the low-pass filter 33, and the output is sent to the mixer 29, pulse shaper 30, selector switch S1, The signal is applied to the phase discriminator 6 again after passing through the high frequency amplifier 2, the mixer 4, and the intermediate frequency amplifier 5, so that these circuits form a phase control loop.

Therefore, with the output of the phase discriminator 6, the voltage controlled phase shifter 31
The amount of phase shift is controlled, and the voltage is adjusted so that the output of the phase discriminator 6 becomes zero, that is, the phase difference between the output 6F of the VCO 7 and the output 6FR of the intermediate frequency amplifier becomes 90°. The 1F output phase from the control phase shifter 31 is controlled.

The 1F output thus obtained is the same as the IF output generated by the frequency divider 25 in the case of FIG.

Note that it is clear that VCO 14 can be used instead of VCO 7.

As the voltage controlled phase shifter, there are various methods such as a method using a monostable multivibrator and a combination of a sawtooth wave oscillator and a voltage comparator as shown in FIG.

As an example, the one shown in FIG. 5 will be explained.

In Figure 5, the sawtooth oscillator consists of a capacitor C2, a resistor R2, a transistor Q1, a diode CR1, and a high input impedance operational amplifier A1 (voltage gain +1).
Consists of A2 etc.

Referring to FIG. 5, the capacitor C1 and the resistor R1 are a square wave differentiating circuit for applying a narrow drive pulse to the transistor.

The slope of the sawtooth wave is determined by the value of C2R2, and the linearity of the slope portion is maintained by the positive feedback provided by the operational amplifier A1 and by the current backflow prevention diode CR1.

A2 is an operational amplifier for amplifying the error voltage, and its output is applied to one input terminal of the voltage comparator A3.

By applying the sawtooth wave output from the operational amplifier A1 to the other input terminal of A3 and slicing it with the error voltage from the low-pass filter 33, the rising phase of the output signal of the voltage comparator A3 is controlled.

The Zener diode CR2 is a DC level converter for slicing the sawtooth wave at the center when the error voltage is 0.

As described above, the voltage-controlled phase shifter does not require the use of particularly expensive components such as a crystal resonator, and can be easily constructed using inexpensive components.

In addition, since the voltage controlled phase shifter outputs a signal with exactly the same frequency as the input signal frequency but with a different phase, the calibration signal generated during the "calibration" operation is a problem when using a crystal controlled oscillator as in the conventional method. There is no fear of frequency drift occurring.

As explained above, in the present invention, one VCO is used to output the intermediate frequency signal indirectly via the voltage controlled phase shifter.
By synchronizing the phase with the CO output, the vCO can operate as an active filter as before, and can also be used as a clock source for the voltage-controlled phase shifter.
An oscillator for calibration can be made unnecessary.

Moreover, two oscillators (VCO7 and VCO24) in the conventional method
) has excellent effects such as being able to eliminate the problem of frequency differences that tend to occur between the two.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional Detsuka receiver and the phase calibration signal generation method used therein; Fig. 2 shows the phase relationship when the input signals of the phase discriminator are in a synchronized state; FIG. 3 is an input/output characteristic diagram of a phase discriminator, FIG. 4 shows the configuration of an embodiment of the present invention, and FIG. 5 is an example of a voltage-controlled phase shifter. In the figure, 1 is an antenna, 2.9 is a high frequency amplifier, and 4.11.
29 is a mixer, 5.12 is an intermediate frequency amplifier, 6.13.
26 is a phase discriminator, 7.14.24 is a voltage controlled oscillator,
3.16.17 is a multiplier, 25.28.34 is a frequency divider,
8.15.27.33 is a low-pass filter, 10 is a multiplier/phase shifter, 21 is a local source oscillator, 22 is a frequency synthesizer, 23
30 is a pulse shaper, 31 is a voltage controlled phase shifter, 32 is a DC amplifier, and 81 to S3 are changeover switches.

Claims (1)

[Claims] 1 A decker equipped with a main station reception channel, a slave station reception channel, a synchronous oscillator provided corresponding to at least one of these reception channels and synchronized with the reception signal, phase synchronization means, and local oscillation signal synthesis means. In the phase calibration method of the receiving device, one of the above receiving channels
The output of the synchronous oscillator provided in one reception channel is added to another phase control means, and the phase control signal from the phase control means of the same reception channel is added to the phase control means on the above side, and and the local oscillation output from the local oscillation signal synthesizing means to generate an equivalent reception signal for calibration and calibrate the input and output phases of each reception channel in addition to each reception channel. phase calibration method.