JPS5853870B2 - Decca receiver phase comparison method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved phase comparison method for a digital receiver that does not require a multiplier.

The Detsuka navigation system uses main stations 6f and 2 or 3 whose transmission frequencies are in a harmonic relationship with respect to a constant fundamental frequency f.
Radio waves from slave stations 5f, 8f, and 9f are received by a mobile object such as a ship or an aircraft, and the phase difference between the signals of the main and slave stations is measured to obtain an equal phase difference hyperbola. This is a radio navigation system that determines the position of a moving object from the intersection of two or three hyperbolas.

In mobile DETSUKA receivers, in order to find the phase difference between transmit signals of different frequencies that are harmonic related to each station, after receiving amplification, the received signals are multiplied to the least common multiple frequency of each received signal. Then, the signals are converted to have the same frequency, and then the phase difference is determined by a phase discriminator.

For example, the frequency of the main station is 6f and the frequency of the slave station is 5f.
If so, the signals are multiplied by 5 or 6, respectively, so that the frequency becomes the least common multiple of 3Of, and the phases of the obtained signals are compared to determine the phase difference.

As described above, the phase comparison method that has been generally used in conventional deck equipment is a method in which the received signal is multiplied by the least common multiple frequency and the phases are compared.

FIG. 1 is a block diagram showing the configuration of a phase comparison method for a conventional digital receiver.

In the figure, 1 is a receiving antenna, 2.3 is a high frequency amplifier, 4.5 is a mixing circuit, 6 is a local oscillator circuit, 7 is an M dividing and pulse shaping circuit, 8.9 is a multiplier, and 10 .11 is an intermediate frequency amplifier, 12.13 is a phase difference detection circuit, 14.1
5 is a voltage controlled oscillator, 16.17 is a low pass filter, 18
．． 19 is a multiplier, 20 is a phase difference detection circuit, and 21 is a phase difference indicator.

As shown in FIG. 1, the reception input of the antenna 1 is connected to the high frequency amplifier 2.
Added to 3.

The high frequency amplifiers 2.3 each have, for example, the main station signal mf(
m is the multiplication order, m=6), and the frequency nf of the slave station (n is the multiplication order, n=5, 8, 9) is selectively amplified and applied to mixers 4 and 5, respectively.

Here, f is the fundamental frequency of the received wave (If214 KHz
).

The local oscillation source circuit 6 is 11 (A is the fundamental frequency of the local oscillation signal, M
is a multiplication order).

The M frequency divider and pulse shaping circuit 7 divides the signal MA by M and pulse shapes the signal MA to generate a pulse signal of frequency A.

Multiplier circuits 8 and 9 multiply the pulse signal A by m and n, respectively, to generate signals with frequencies of mA and nJ, respectively, and apply them to mixer 4.5.

The mixers 4.5 each receive a signal of difference frequency mF=mJ−m
f, nF=nJ-nf are taken out and applied to intermediate frequency amplifiers 10 and 11, respectively.

Here, F is the fundamental frequency of the intermediate frequency (1F in the conventional method)
= 16 KHz), and there is a relationship of F=A−f.

The intermediate frequency amplifiers 10 and 11 each receive an intermediate frequency signal m
F and nF are amplified and each phase difference detection circuit 12.1
Add to 3.

The phase difference detection circuits 12 and 13 each receive an intermediate frequency signal m
F and nF are compared in phase with a signal button having a frequency mF generated by the voltage controlled oscillator 14 and a signal having a frequency nF generated by the voltage controlled oscillator 150, respectively, to generate signals corresponding to the respective phase differences.

The phase difference output signals of the phase difference detection circuits 12.13 are smoothed through low-pass filters 16.17, and then fed back to the voltage controlled oscillators 14.15, respectively.
The oscillation frequency is controlled so that each phase difference output approaches zero.

In this way, the respective outputs mF, nF of the voltage controlled oscillators 14.15 are phase-locked to the intermediate frequency signals mF, nF, respectively.

Phase difference detection circuit 12, voltage controlled oscillator 14 button and low pass filter 16, phase difference detection circuit 13, voltage controlled oscillator 15
and the low-pass filter 17 each operate as a narrow band variable frequency active filter (tracking loop filter).

The output signals mF and nF of the voltage controlled oscillator 14.15 are multiplied by p or q, respectively, to a multiplier 18.19 to generate signals having frequencies of mpF and nqF, respectively.

Here, the multiplication factor mp-nq with respect to the fundamental frequency F is selected.

The signals mpF and nqF are phase-compared in a phase difference detection circuit 20 to generate an output according to the phase difference, and a phase difference indicator 21 indicates this.

FIG. 2 is a waveform diagram showing the frequency and phase relationship of each part signal of the conventional method shown in FIG. 1.

In the same figure, d is the voltage controlled oscillator 14.1.
5, and a and c are the signals mpF and nq generated by multiplying the output signals mF and nF, respectively.
It shows F.

As shown in FIG. 3, the signals mpF and rrLF, and the signal n
The frequency and phase relationship between qF and nF is fixed by the multiplier circuit and remains unchanged unless the filter of the multiplier circuit changes.

As described above, the conventional phase comparison method is a method in which the least common multiple frequency is multiplied by 1''c and then phase comparison is performed.

Such a method has the following drawbacks.

(1) Phase drift is likely to occur due to temperature changes and aging.

That is, when frequency multiplication is performed, a fundamental wave is usually converted into a pulse waveform, and then a desired signal is extracted from its harmonic components through a filter tuned to a desired harmonic.

Therefore, as the tuning frequency of the filter (usually an LC filter) changes due to temperature changes and aging,
It is inevitable that phase drift will occur.

(2) It is expensive and difficult to downsize.

Since the above-described filter for extracting harmonic signals requires accurate phase adjustment, a variable tuning filter is usually used to adjust the amplitude and phase of the output to obtain desired characteristics.

Therefore, it is extremely difficult and expensive to make no adjustments.

Although the dimensions of the filter vary depending on the frequency used, this method uses a long wave band frequency, so it is difficult to miniaturize the filter.

The present invention attempts to eliminate such drawbacks of the prior art by using a variable frequency active filter including a voltage controlled oscillator or a voltage controlled phase shifter in combination with a frequency dividing circuit. The purpose of this invention is to provide a method that can perform phase comparison without frequency multiplication.

To achieve this purpose, the phase comparison method of the digital receiver of the present invention includes a voltage controlled oscillator or a voltage controlled phase shifter that shifts the phase of the signal of the voltage controlled oscillator, and a voltage controlled oscillator or voltage controlled phase shifter that shifts the phase of the signal of the voltage controlled oscillator. a frequency divider that divides the frequency of the output signal of the frequency divider, the output signal of the frequency divider and the received signal are compared in phase, and the voltage controlled oscillator or the voltage controlled phase shifter is controlled by the phase difference output. Active filters that generate multiplied waves having a constant phase relationship with the received signal are provided for the main station and the slave station, and a voltage controlled oscillator or voltage controlled phase shifter for the main station button and the slave station active filter is provided. It is characterized in that the output signal is taken out through a frequency divider included in the tit or the loop of the active filter and the phases are compared to detect the phase difference between the main station signal and the slave station signal.

Examples will be described below.

FIG. 3 is a block diagram showing the configuration of an embodiment of the phase comparison method of the digital receiver of the present invention.

Components in this figure that are the same as those in FIG. 1 are designated by the same reference numerals.

22.23 is a voltage controlled oscillator, and 24.25 is a frequency dividing circuit.

Click the button in Figure 3 to connect the receiving input to the intermediate frequency amplifier 10.11.
The configuration buttons and operations at output 1 are the same as in FIG.

Voltage controlled oscillators 22 and 23 generate signals with frequencies of mpF and nqF, respectively, and these signals are applied to frequency divider circuits 24 and 25, where they are divided by p and q, respectively, to output mF and nqF, respectively. yields nF.

The phase difference detection circuit 12 compares the output of the frequency divider 24 and the output mF of the intermediate frequency amplifier 10, and generates an output according to the phase difference.

This output is smoothed through a low-pass filter 16 and fed back to the voltage controlled oscillator 22, where the oscillation frequency is controlled so that the phase difference output approaches zero, and the voltage controlled oscillator 22
The output mpF of is phase-locked with the intermediate frequency signal mF.

Voltage controlled oscillator 22, frequency dividing circuit 24, phase difference detection circuit 1
2. The low pass filter 16 operates as a narrow band variable frequency active filter as in FIG.

Similarly, the voltage controlled oscillator 23, the frequency dividing circuit 25, the phase difference detection circuit 13, and the low-pass filter 17 form a narrow band variable frequency active filter, and the voltage controlled oscillator 23 is phase synchronized with the output nF of the intermediate frequency amplifier 11. produces an output with a frequency nqF.

Here, the signal mpF and the signal nqF are selected so that the magnification mp=nq for the fundamental frequency F is satisfied.

The phase difference detection circuit 20 uses the output mpF of the voltage controlled oscillator 22.
and the output nqF of the voltage controlled oscillator 23 to generate an output according to the phase difference, and the phase difference indicator 21 indicates this.

FIG. 4 is a waveform diagram showing the frequency and phase relationships of various signals in the system of the present invention shown in FIG.

In the figure, a is the output signal waveform of the voltage controlled oscillator 22 or 23, b is the signal waveform obtained by converting the voltage controlled oscillator output signal into a square wave, C is the output signal waveform of the frequency divider 24 or 25, d indicates a sine wave component of the frequency divider output signal waveform.

Phase comparison using the phase difference detection circuit 12 or 13 is performed between the frequency divider output signal shown in FIG. 4C or its sine wave component shown in FIG. 4D and the intermediate frequency output signal. The voltage controlled oscillator is controlled according to the result and the voltage controlled oscillator is controlled as shown in FIG.
The frequency of the output signal shown in is varied to phase-lock the frequency divider output signal or its sinusoidal component to the intermediate frequency signal.

Here, the phase relationship between the pre-frequency-divided signal shown in Figure 4 and the frequency-divided signal shown in Figure 4C is determined by the state of the frequency divider at the start of operation. It won't change.

Therefore, the phase relationship between the pre-divided signal and the divided signal may change each time the power is turned on, but the degree of this change is 2π (rad)t or ]
Changes in integer multiples of cycles.

However, the phase difference of the received signal between the master station and the slave station is
Since these signals are measured within one cycle between the voltage-controlled oscillator output signal shown in Figure a or the signal corresponding to the square wave signal shown in Figure a, it is assumed that these signals are integer multiples of one cycle. Even if the phase changes, there is no problem in measurement.
Moreover, no measurement error occurs.

In this way, the oscillation frequency of the voltage controlled oscillator constituting the active filter is set to a comparison frequency (mpFt
or nqF), it is possible to compare the phases of the signals of both the master and slave stations without using a multiplier.

FIG. 5 is a block diagram showing the configuration of another embodiment of the phase comparison method of the digital receiver according to the present invention.

In the figure, 31 is a receiving antenna, 32.33 is a high frequency amplifier, 34.35 is a mixing circuit, 36.3T is a frequency dividing circuit,
38.39 is an intermediate frequency amplifier, 40.41 is a phase difference detection circuit, 42 is a mixing circuit, 43 is a voltage controlled oscillator, 44 is a reference oscillator, 45 is a frequency dividing circuit, 46 is a low-pass filter, 4
7 is a multiplier, 48 is a voltage controlled phase shifter, 49 is a frequency dividing circuit,
50 is a low-pass filter, 51 is a phase difference detection circuit, 52 is a phase difference indicator, 53 is a variable frequency oscillator, 54 is a mixing circuit, 55 is a band filter, 56 is a variable frequency dividing circuit, 57 is a reception chain setter, 58 is a fixed frequency dividing circuit, 59 is a phase difference detection circuit, and 60 is a low-pass filter.

In FIG. 5, the receiving inputs of the antenna 31 (main station 6f, slave station 5f) are amplified by high-frequency amplifiers 32, 33, respectively, and sent to mixing circuits 34, 35, respectively, and generated by frequency dividers 36, 37. The received local oscillator signals 6A and 5A are mixed to produce intermediate frequency signals 6F and 5F, respectively.

Each of these intermediate frequency signals is sent to an intermediate frequency amplifier 38.
．． After being amplified by phase difference detection circuit 40.
Added to 41.

On the other hand, the mixing circuit 42 mixes the signal f 1 from the voltage controlled oscillator 43 and the signal fR from the reference oscillator 44 to generate a signal 1080F of the difference frequency.

The signal 1080F is frequency-divided by 180 by the frequency dividing circuit 45 to generate a signal 6F, which is applied to the phase difference detection circuit 40.

The phase difference detection circuit 40 compares both signals and generates an output according to the phase difference, and this output is fed back to the voltage controlled oscillator 43 via a low-pass filter 46 to control its oscillation frequency.

The voltage controlled oscillator 43, mixing circuit 42, frequency divider 45, phase difference detection circuit 40, and low pass filter 46 constitute a narrow band variable frequency active filter similar to that shown in FIG.

Further, the output signal 1080F of the mixing circuit 42 is sent to a multiplier 47 and multiplied by 4 to produce a signal 4320F.

Signal 4320F is applied to voltage controlled phase shifter 48 (1
44±1) to produce output signal 30F.

The output signal 30F is frequency-divided by 6 in the frequency divider circuit 49 to generate an output signal 5F, which is applied to the phase difference detection circuit 41.

The phase difference detection circuit 41 compares both signals and generates an output according to the phase difference, and this output is fed back to the voltage-controlled phase shifter 48 through a low-pass filter 50 to control its frequency division ratio. control the output frequency.

Voltage control phase shifter 48, frequency divider circuit 49, phase difference detection circuit 4
The L low-pass filter 50 similarly constitutes a narrow band variable frequency active filter.

The 36 frequency divided output 30F to the frequency dividing circuit 45 and the output signal 30F of the voltage controlled phase shifter 48 are phase-compared and sent to a phase difference detection circuit 51 to produce an output according to the phase difference, and a phase difference indicator. A variable frequency oscillator 53, designated by 52, generates a local frequency signal 1080J.

This signal is mixed with the signal from the reference oscillator 44 by a mixing circuit 54, selectively extracting a desired frequency band by a bandpass filter 55, and then divided by a variable frequency dividing circuit 56.

1A variable frequency divider circuit 560 frequency division ratio is receive chain setter 57
Can be set externally by

On the other hand, the fixed frequency divider circuit 58 receives the output signal f of the reference oscillator 44.
Divide R using a fixed frequency division ratio.

The output signals of both frequency dividing circuits are phase-compared by a phase difference detection circuit 59 to generate an output according to the phase difference.

This output is passed through a low-pass filter 60 to a variable frequency oscillator 5.
The oscillation frequency of the reference oscillator 44 is controlled to achieve phase synchronization with the reference oscillator 44.

In this way, the loop including the variable frequency oscillator 53 constitutes a synthesizer circuit, and generates local oscillation frequency signals at constant frequency intervals in correspondence with the receiving chain.

Local oscillator frequency signal generated by variable frequency oscillator 53] 0
80J is frequency-divided by 180 in the frequency divider circuit 36, and frequency-divided by 216 in the divided frequency divider circuit 37 to generate signals of 6A and 5A, respectively, which are respectively applied to the mixing circuits 34 and 35 as described above.

For the embodiment shown in FIG. 5, signal fv corresponds to signal mpF in the embodiment of FIG.

However, in the method of this embodiment, the intermediate frequency is selected to be extremely low for the purpose of improving selectivity, so the frequency drift of the local reference signal fR becomes a problem. Signal mF (6F), mpF
This is solved by configuring to obtain (30F).

As explained above, according to the phase comparison method of the digital receiver of the present invention, the circuit can be made without adjustment by not using a multiplier circuit, and the phase change due to frequency division is extremely small (usually compared to digital ICs). (The fall and fall delay time changes due to temperature changes are very small.) Therefore, a phase comparison method with extremely high stability can be realized, and it is inexpensive and provides excellent effects.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of a phase comparison method for a conventional digital receiver, Fig. 2 is a waveform diagram showing the frequency and phase relationship of each part signal for the method shown in Fig. 1, and Fig. 3 is a diagram of the present invention. FIG. 4 is a waveform diagram showing the frequency and phase relationship of each part of the signal in the method of FIG. 3, and FIG. FIG. 3 is a block diagram showing the configuration of another embodiment of the phase comparison method of the device. 1... Receiving antenna, 2.3... High frequency amplifier, 4.
5...Mixing circuit, 6...Local oscillator circuit, 7...M
Frequency division and pulse shaping circuit, 8.9...multiplier, 10
．． 11... Intermediate frequency amplifier, 12.13... Phase difference detection circuit, 14.15... Voltage controlled oscillator, 16.1
7...Low pass filter, 18.19...Multiplier, 20
... Phase difference detection circuit, 21 ... Phase difference indicator, 22
．． 23... Voltage controlled oscillator, 24.25... Frequency dividing circuit, 31... Receiving antenna, 32.33... High frequency amplifier, 34.35... Mixing circuit, 36.37... Min. Frequency circuit, 38.39...Intermediate frequency amplifier, 40.41
...Phase difference detection circuit, 42...Mixing circuit, 43...
・Voltage controlled oscillator, 44... Reference oscillator, 45...
Frequency divider circuit, 46...Low pass filter, 47...Multiplier, 48...Voltage control phase shifter, 49...Frequency divider circuit, 5
0...Low pass filter, 51...Phase difference detection circuit, 5
2... Phase difference indicator, 53... Variable frequency oscillator, 5
4...Mixing circuit, 55...Band filter, 56...
・Variable frequency divider circuit, 57... Receive chain setting device, 58
. . . Fixed frequency dividing circuit, 59 . . . Phase difference detection circuit, 60
...Low pass filter.

Claims (1)

[Claims] 1 includes a voltage controlled oscillator or a voltage controlled phase shifter that shifts the phase of the signal of the voltage controlled oscillator, and a frequency divider that divides the output signal of the voltage controlled oscillator or the voltage controlled phase shifter, An active filter for the main station that compares the phases of the output signal and the received signal and controls the voltage controlled oscillator or voltage controlled phase shifter using the phase difference output to generate a multiplied wave having a constant phase relationship with the received signal. The output signal of a voltage controlled oscillator or a voltage controlled phase shifter provided for the master station and the slave station, and which is switched to the active filter for the master station and the slave station, is divided into 11 or 1 part included in the loop of the active filter. A phase comparison method for a DETSUKA receiving device characterized by detecting a phase difference between a main station signal and a slave signal by extracting the signal through a frequency converter and comparing the phases.