JPH04238419A - Pilot signal insertion circuit - Google Patents

Abstract

PURPOSE:To use a double frequency converter being a standard unit by multiplying a difference frequency between the output frequency of a crystal oscillator and a reference signal for frequency correction, and synthesizing it with an IF signal. CONSTITUTION:The multiplication degree of a phase oscillator 5 is set to be N, and the frequency of the crystal oscillator 8 to be FP/N, and the multiplication degree of an IF multiplier 10 to be N, the center value of the reference signal for frequency correction to be fR, and the frequency fluctuation of a satellite repeater to be F. Then, fR- F/N is inputted to a correction frequency inputted to a frequency correction reference signal input terminal 6 from the AFC receiver of a sea side station. Thus, fR- F/N is inputted to the output frequency of the phase synchronous oscillator 5 from the AFC receiver of the sea side station. Thus, the output frequency of the oscillator 5 becomes N(fR- F/N)=NfR- F. When the IF frequency of the communication signal in an IF input terminal is set to be fI, the output frequency of a first mixer 2 becomes fI+NfR- F, and it is corrected inversely to the frequency fluctuation of the satellite repeater. Then, frequency fluctuation is cancelled in the output of the satellite repeater.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pilot signal insertion circuit applied to maritime satellite communication earth stations and the like.

0002

[Prior Art] In general, maritime satellite communications employ a narrowband SCPC communication system, so fluctuations in the local frequency of the satellite repeater are large compared to the channel spacing. Local frequency correction is required. Particularly in communication from a coast station to a ship station via a satellite, a pilot signal is inserted in order to correct the frequency at the coast station in order to simplify the equipment on the ship station side.

Conventionally, this type of pilot signal insertion circuit for frequency correction has an IF input terminal 1, as shown in FIG.
Consists of first and second mixers 2, 3, local oscillator 4, phase-locked oscillator 5, frequency correction reference signal input terminal 6, RF output terminal 12, crystal oscillator 13, phase-locked oscillator 14, and synthesizer 15 .

Next, its operation will be explained. IF input terminal 1
The communication IF signal applied to the terminal 6 is mixed with the output of the phase synchronized oscillator 5 synchronized with the frequency correction reference signal applied to the terminal 6 in the first mixer 2, and then mixed with the output of the phase synchronized oscillator 5 which is synchronized with the frequency correction reference signal applied to the terminal 6. It is combined with the output of the phase-locked oscillator 14 synchronized with the output of the oscillator 13 and input to the second mixer 3. The mixer 3 mixes the signal with the output of the local oscillator 4 and converts the frequency into an RF band. The output of the phase synchronized oscillator 14 is used as a pilot signal. An RF band signal including a communication IF signal and a pilot signal is transmitted from a coast station to a satellite, frequency-converted by a satellite repeater, and then transmitted as a down line to a coast station and a ship station. Although not shown, the satellite return signal received by the coast station is used by an AFC receiver to detect local frequency fluctuations of the satellite repeater using a pilot signal, generate a frequency correction reference signal, and input the reference signal for frequency correction. Supplied to terminal 6. By doing this, the communication signal transmitted from the coast station is corrected in frequency with the opposite polarity to the frequency fluctuation of the satellite repeater, so when it is transmitted from the satellite, the frequency fluctuation of the satellite itself is canceled out.
A constant frequency will always be radiated to the down line. Therefore, the ship station can receive signals without using a complicated AFC device.

[0005]

Problems to be Solved by the Invention In the conventional pilot signal insertion circuit described above, since the pilot signal combiner is located between the first mixer and the second mixer constituting the dual frequency conversion device, There was a drawback that standard equipment having the first mixer, second mixer, local oscillator, and phase-locked oscillator as constituent units could not be used.

[0006]

[Means for Solving the Problems] The pilot signal insertion circuit of the present invention includes a reference signal distributor that distributes a reference signal for correcting frequency deviation caused by a satellite repeater, and a crystal oscillator that generates the original oscillation of the pilot signal. , an IF mixer that mixes the output signal of this crystal oscillator and one output signal of the reference signal distributor and outputs a difference frequency, and the output of this IF mixer is multiplied by N (N is an integer). an IF component that takes a sum signal of the output signal of this multiplier and a communication IF signal, and a phase synchronized oscillator that is synchronized with the other output signal of the reference signal distributor. a first mixer that mixes the output signal and the output signal of the IF combiner;
It has a second mixer that mixes the local oscillation signal of the RF frequency and the output signal of the first mixer.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. In FIG. 1, the same symbols as in the conventional example in FIG. 2 have the same functions. That is, in this embodiment, a reference signal distributor 7, a crystal oscillator 8, an IF mixer 9, an IF multiplier 1
0, a configuration such as an IF band synthesizer 11 is added, and the first
A part that converts an IF band signal into an RF band signal, which is composed of a mixer 2, a second mixer 3, a local oscillator 4, and a phase synchronized oscillator 5, is incorporated as standard equipment.

Next, the operation of this embodiment will be explained. The communication IF signal applied to the IF input terminal 1 is sent to the IF synthesizer 11.
It is combined with a pilot signal whose source oscillation is a crystal oscillator 8, which will be described later. The synthesized signal is mixed in the first mixer 2 with the output of the phase synchronized oscillator 5 synchronized with the reference signal that has passed from the frequency correction reference signal input terminal 6 through the reference signal distributor 7, and a sum signal is generated. This sum signal is further input to the second mixer 3 and mixed with the output of the local oscillator 4 to generate the next sum signal, which is supplied to the RF output terminal 12. On the other hand, the reference signal distributed by the reference signal distributor 7 is input to the IF band mixer 9, where it is mixed with the output of the crystal oscillator 8, which is the original oscillation of the pilot signal, and the difference signal is sent to the IF band mixer 10.
is input. The output of the IF multiplier 10 is applied to the IF combiner 10 as a pilot signal. Now, let FP be the output frequency of the phase-locked oscillator 14 in FIG. 2 of the conventional example, let the multiplier order of the phase-locked oscillator 5 in FIG.
The multiplication order is N, and the center value of the frequency correction reference signal is f.
R, the frequency fluctuation of the satellite repeater is △F, the correction frequency input to the frequency correction reference signal input terminal 6 is fR-△ from the AFC receiver of the coast station in the same procedure as the conventional example.
F/N is input. Therefore, the output frequency of the phase synchronized oscillator 5 is N(fR-ΔF/N)=NfR-ΔF. If the IF frequency of the communication signal at the IF input terminal 1 is fI, the output frequency of the first mixer 2 is fI + NfR - △F, which is corrected inversely to the frequency fluctuation of the satellite repeater. In the output of , the frequency fluctuation is canceled out and the output is always constant. Also, the output of the IF band mixer 9 is FP/N
-(fR-△F/N), the output frequency of the IF multiplier 10 is multiplied by N(FP/N-(fR-△F/N).
F/N))=FP-NfR+ΔF. The output of the IF multiplier 10 is combined with the communication signal by the IF band combiner 11,
It is input to the first mixer 2. Next, the output frequency of the first mixer 2 is (FP-NfR+△F)+N(fR-△F/N
)=FP, which is exactly the same as the output frequency of the phase synchronized oscillator 14 in FIG. Even if the pilot signals are combined in the IF band in this way, the output of the first mixer 2 is always constant without being affected by the correction variation of the frequency correction reference signal. By inputting the IF signal into which a pilot has been inserted in the IF band in this manner, standard equipment having the above-described configuration can be used for subsequent conversion to an RF signal.

0010

As explained above, the present invention multiplies the difference frequency between the output frequency of the crystal oscillator and the frequency correction reference signal by the same order as that of the phase synchronized oscillator 5 using the IF multiplier. By combining the pilot signal with a communication IF signal in the IF band, it is possible to use a dual frequency converter, which is a standard device shown by a dotted line in FIG. 1, and has the effect of improving productivity.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a pilot signal insertion circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional pilot signal insertion circuit.

[Explanation of symbols]

1 IF input terminal 2 First mixer 3 Second mixer 4 Local oscillator 5, 14 Phase synchronized oscillator 6 Frequency correction reference signal input terminal 7 Reference signal distributor 8, 13 Crystal oscillator 9 IF mixer 10 IF multiplier 11 IF synthesizer 12 RF output terminal 15 synthesizer

Claims (2)

[Claims] 1. A reference signal distributor that distributes a reference signal for correcting frequency deviations caused by a satellite repeater, a crystal oscillator that generates an original oscillation of a pilot signal, an output signal of the crystal oscillator, and the reference signal distributor. an IF mixer that mixes the output signal of one of the two output signals and outputs the difference frequency;
A multiplier that multiplies the output of the F mixer by N (N is an integer), an IF component that takes a sum signal of the output signal of the multiplier and a communication IF signal, and the other of the reference signal distributors. a first mixer that mixes an output signal multiplied by N of a phase-locked oscillator synchronized with an output signal of the IF synthesizer, and a local oscillation signal of an RF frequency and an output signal of the first mixer. A pilot signal insertion circuit characterized by having a second mixer for mixing. 2. The pilot signal insertion circuit according to claim 1, wherein the frequency of the first mixer output signal is always constant without being affected by correction fluctuations of the frequency correction reference signal.