JPH0435140A - Frequency synchronizing system - Google Patents

Abstract

PURPOSE:To always make a frequency of a reference carrier coincident with an intermediate frequency by frequency-dividing an output of a reference oscillator so as to obtain a reference carrier, multiplying it, comparing the phase of it with an output of a frequency divider and controlling the frequency of the reference oscillator. CONSTITUTION:A carrier oscillated at a reference oscillator 8 is inputted respectively to 1st and 2nd local oscillators 2, 5, and 1/m frequency-divided by a 1/m frequency divider 9, 1/8 frequency-divided by a 1/8 frequency divider 10 and the result is fed to an orthogonal detector 11 as a reference carrier. Moreover, part of the signal of a 2nd intermediate frequency outputted from a 2nd intermediate frequency filter 7 is inputted to a 8 multiplier 13, in which the signal is multiplied by a multiple of 8, in which a modulation component of 8-phase modulation wave is eliminated and the result is inputted to a phase detector 12. The phase detector 12 uses an output from a 8 multiplier 13 and an output from the 1/m frequency divider 9 to apply phase detection. The phase detection output of the phase detector 12 is fed back to the reference oscillator 12 to control the oscillating frequency so that the synchronization detection is implemented by the orthogonal detector 11. Thus, circuit integration is facilitated and an inexpensive system is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to frequency synchronization of an N-phase phase modulation receiver.

(Prior Art) FIG. 2 is a block diagram showing a frequency synchronization method of a conventional superheterodyne receiver for N-phase phase modulation. In the figure, a received signal received by an antenna 1 is mixed with a signal from a first local oscillator 2, which is a frequency synthesizer, by a first mixer 3, converted to a first intermediate frequency, and then filtered by a first intermediate frequency filter. Unnecessary waves are removed by the wave generator 4 and input to the second mixer 6. The first intermediate frequency signal input to the second mixer 6 is mixed with the signal from the second local oscillator 5, which is a frequency synthesizer, and converted to a second intermediate frequency, which is then unnecessary by the second intermediate frequency filter 7. The waves are removed and input to the quadrature detector 11. The second intermediate frequency signal input to the quadrature detector 11 is converted to baseband using a signal from a reference carrier generator 15, which is a frequency synthesizer, and is output from an output terminal 14. Further, a part of the signal output from the quadrature detector 11 is input to a frequency error detector I6, and a frequency difference between the second intermediate frequency and the signal from the reference carrier generator 15 is detected. The detected deviation is applied as an error signal to the reference oscillator 8 to control its oscillation frequency, and the output of the reference oscillator 8 is applied to the first local oscillator 2 and the second local oscillator 5.
are added to each to control their oscillation frequencies.

In this way, the oscillation frequency of the reference oscillator 8 is controlled so that the quadrature detector 11 performs synchronous detection.

Note that as a method for reproducing carrier waves for synchronous detection by the frequency error detector 16, reference oscillator 8, and reference carrier wave generator 15, a Costas-Srusot type regeneration method or the like may be used.

(Problem to be Solved by the Invention) However, in the frequency synchronization method described above, the oscillation frequency of the reference oscillator 8 and the second intermediate frequency generally do not have a multiple relationship, so the reference carrier generator 15 must be constructed from a synthesizer, which is expensive. Moreover, there is a drawback that the frequency error detector 16 becomes complicated for polyphase phase modulation.

The present invention has been made in order to eliminate the drawbacks mentioned above, and is an inexpensive frequency synchronization method that can perform frequency synchronization without using an expensive reference carrier generator J5 or a complicated frequency error detector 16. The aim is to provide a method in January.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a frequency synchronization method for an N-phase phase modulation hetero gain receiver in which a received signal converted to an intermediate frequency is orthogonally detected using a reference carrier wave. a reference oscillator that outputs a carrier wave, a 10th frequency divider that divides the output of the reference oscillator by 7M (M: an integer), and a 10th frequency divider that divides the output of the 10th frequency divider by 17N (N: an integer). It has a 20th frequency divider that outputs as the reference carrier wave, a multiplier that multiplies the received signal of the intermediate frequency by N, and a phase detector that compares the phases of the outputs of the multiplier and the 10th frequency divider. , the output of the phase detector is input to a reference oscillator, and its oscillation frequency is controlled so that the frequency of the reference carrier wave coincides with the intermediate frequency.

(Function) The intermediate frequency and the oscillation frequency of the reference oscillator are related by multiples (NX
M) K is determined, and the output of the reference oscillator is divided by ], /M by a first frequency divider, and further divided by ]/N by a second frequency divider to obtain a reference carrier wave for intermediate frequency detection. I am getting . Then, the intermediate frequency signal is converted to N by a multiplier.
The modulation component of the N-phase phase modulation is removed by multiplication, the phase is compared with the output of the first frequency divider by a phase detector, and the oscillation frequency of the reference oscillator is controlled based on the comparison result.

As a result, the oscillation frequency of the reference oscillator is controlled so that the frequencies of the output of the first frequency divider and the output of the multiplier match, and as a result, the frequency of the reference carrier wave always matches the intermediate frequency.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the present invention.
This is an example of application to frequency synchronization of a superhederodyne receiver for phase modulation. In FIG. 1, a received signal received by an amplifier 1 is mixed with a signal from a first local oscillator 2, which is a frequency synthesizer, by a first mixer 3, and converted into a first intermediate frequency of the frequency difference, Unnecessary waves are removed by the intermediate frequency filter 4 and input to the second mixer 6. The signal of the first intermediate frequency inputted to the second mixer 6 is mixed with the signal from the second local oscillator 5, which is a frequency synthesizer, and converted to a second intermediate frequency of the frequency difference,
Unnecessary waves are removed by the second intermediate frequency filter 7 and input to the quadrature detector 11 .

The second intermediate frequency signal B1 input to the quadrature detector 11
The signal is converted to baseband using the reference carrier wave from the /8 frequency divider and outputted from the output terminal 14.

On the other hand, the carrier wave oscillated by the reference oscillator 8 is the first local oscillator 2,
In addition to being input to the second station 5, 1. /m frequency divider 9], /m frequency division, and further 1/8 frequency divider 10
The frequency is divided into 1/8 by the quadrature detector 1 as the reference carrier wave.
Added to 0. A part of the second intermediate frequency signal outputted from the second intermediate frequency filter 7 is transferred to the 8 multiplier 1.
3 and is multiplied by 8 to remove the modulation components of the 8-phase phase modulated wave and input to the phase detector 12.

The phase detector I2 performs phase detection using the output from the 8-multiplier I3 and the output from the z/m frequency divider 9. The phase detection output of this phase detector 120 is fed back to the reference oscillator 12, and its oscillation frequency is controlled so that the quadrature detector 11 performs synchronous detection.

f8 is the frequency of the received signal received by antenna 1, fR1 is the oscillation frequency of reference oscillator 8, nl is the frequency of the output of the first local oscillator 2, nl is fR1 is the frequency of the output of the second local oscillator, n 2 f
R, the frequency of the signal input from the 8-multiplier 13 to the phase detector 12 is 5 (fs ] 11fRn2fR)
Therefore, the frequency of the carrier wave input from the 1/m frequency divider 9 to the phase detector 12 is fR//fm, and the frequency of the carrier wave input from the 1/m frequency divider 9 to the phase detector 12 is fR//fm.
The oscillation frequency of is the above two frequencies 8 (fS-n1fR-
n2fR) and fR//m are controlled to be equal. The force is 1.7'R/m=8(J'8-nlfRn
2fR) holds true.

Transforming this, f 3-(, fR/8) ・(nl
+n2 + 17in), and the received signal (f6) and the reference oscillator 80 oscillation output (fR) are synchronized.

Note that since the output of the phase detector 12 contains some noise and phase fluctuation components, the output is applied to the reference oscillator 8 through a time constant circuit having a sufficient time constant.

In addition to the above-mentioned 8-phase phase modulation method, this frequency synchronization method uses two-phase,
It can also be applied to a phase modulation method such as 4-phase, a π/4 shift FQPSK method, etc.

(Effects of the Invention) As described in detail above, according to the present invention, a detection standard is provided using a frequency divider, a multiplier, and a phase detector in place of the conventional reference carrier generator and frequency error detection circuit. Since a carrier wave is generated, it can be configured with a digital circuit that can be easily integrated into an IC, and an inexpensive frequency synchronization method can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional frequency synchronization method. DESCRIPTION OF SYMBOLS 1... Antenna, 2... 1st station oscillation, 3... 1st mixer, 4... 1st intermediate frequency filter, 5... 2nd station oscillation, 6... 1st station oscillation 2 mixer, 7... second intermediate frequency filter, 8... reference oscillator, 9... 1//m frequency divider, I
O...IA frequency divider, 11...Quadrature detector, 12...
・Phase detector, 13...8 multiplier, 14...output terminal.

Claims (1)

[Claims] In a frequency synchronization method of a heterodyne receiver for N-phase phase modulation in which a received signal converted to an intermediate frequency is orthogonally detected using a reference carrier wave, there is provided a reference oscillator that outputs a carrier wave, and an output of the reference oscillator. a first frequency divider that divides the output of the first frequency divider by 1/M (M: an integer), and a second frequency divider that divides the output of the first frequency divider by 1/N (N: an integer) and outputs the result as the reference carrier wave. a frequency divider, a multiplier that multiplies the received signal of the intermediate frequency by N, and a phase detector that compares the phases of the outputs of the multiplier and the first frequency divider, A frequency synchronization method characterized by inputting an output to a reference oscillator and controlling its oscillation frequency so that the frequency of the reference carrier wave matches an intermediate frequency.