JPS60226231A - Pilot receiver - Google Patents

Abstract

PURPOSE:To simplify the constitution by decreasing the number of a phase locked oscillator being a component of a PLL section in a pilot receiver applied to a satellite communication earth station. CONSTITUTION:A transmission section Tx of the earth station frequency-converts an output signal of a modulator 1 by using an oscillator of the phase locked oscillator 4, a pilot signal is superimposed on the converting frequency and the result is transmitted toward a satellite from an antenna ANT. On the other hand, a reception section Rx converts a signal reflected on the satellite at a mixing section 12 into an intermediate frequency, outputs it to a demodulator 15 and inputs it to a pilot reception section PL. The pilot reception section PL consists of a phase detector 16 comparing the phase of an output of the phase locked oscillator 23 and the reception input and inputting its output to a VCO 19 via an amplifier 18 and of a mixer 17 mixing an output of a VCO 19 and an output of a reference oscillator 20 and outputting the result of mixture to the phase locked oscillator 23. The pilot reception section PL detects the frequency fluctuation at a satellite repeater and feeds back its output to the oscillator 4 so as to control the transmission frequency in a direction without any frequency fluctuation.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a pilot receiving device applied to a maritime satellite communications earth station.

Description of the Prior Art Conventionally, maritime satellite communications have adopted a narrowband QQpQ communication system, so fluctuations in the local frequency of the satellite repeater are large compared to the channel spacing, and some kind of frequency correction is required. Become. In particular, in communication from land to a ship station, in order to simplify the equipment of the ship station, a system is used in which frequency correction is performed at the shore station. As an example, a method as shown in FIG. 1 can be considered.

In FIG. 1, 1 is a modulator, 2 and 3 are mixers, 4,
5.6 is a phase synchronized oscillator, 7 and 8 are crystal oscillators, 9 is a power amplifier, 10 is a duplexer, 11 is a low noise amplifier, 12
is a mixer, 13 is a phase synchronized oscillator, 14 is a crystal oscillator,
15 is a demodulator, 16 is a phase detector, 17 is a mixer, 18
1 is a loop amplifier, 19 is a voltage controlled oscillator, + is a crystal oscillator, and 21 and ρ are phase-locked oscillators, respectively. fu
1 to n are transmission carrier waves, and fd1 to n are reception carrier waves. For example, in the Inmarsat γ stem, the channel spacing is 25 KHz, whereas the frequency fluctuation of the satellite repeater is about ±55 KHz at maximum. .

Next, the operation will be explained with reference to FIG. The IFF output of the modulator 1 is mixed with the output of the phase-locked oscillator 4 in the mixer 2, and then mixed with the output of the phase-locked oscillator 6 synchronized with the output of the crystal oscillator 8 in the mixer 3.
The frequency is converted to the GH2 band. This 60Hz band signal is
The signal is amplified by a power amplifier 9, passes through a duplexer 10, and is transmitted from the antenna to the satellite SAT. The output of the phase-locked oscillator 5 synchronized with the output of the crystal oscillator 7 is similarly frequency-converted to the 6 GHz band by the mixer 3, used as a pilot signal for frequency correction, and is used as a pilot signal for frequency correction. One wave (e.g. ful) is assigned to the satellite SAT
sent to.

These signals are received by the satellite EiAT at frequencies fd, ~n
(1,50H2 band) and the satellite EtA again.
It is transmitted from T to coast stations and ship stations. The signal received at the coast station is supplied to a low-noise amplifier 11 via a duplexer 10 and amplified, and then a crystal oscillator 1
The signal is mixed with the output of the phase-locked oscillator 13 synchronized with the output of the signal generator 4, frequency-converted to the F-band, and supplied to the demodulator 15. A part of the IF band doubled signal is supplied to a pilot receiving device for frequency correction (the part surrounded by a broken line), and is sent to a phase detector 1.
6, it is compared with the difference output of the mixer 17, and a DC voltage corresponding to the phase error is output. This DC voltage is applied to a voltage controlled oscillator 19 via a loop amplifier 18 for configuring a phase locked loop, and controls its output frequency.

The output of the voltage controlled oscillator 19 is multiplied by N by the phase synchronized oscillator 21 and supplied to the mixer 17 . The output of the crystal oscillator Zenmi is multiplied by M by the phase-locked oscillator n, mixed with the output of the phase-locked oscillator 21 in the mixer 17, and the difference frequency is supplied to the phase detector 16. A part of the output of the voltage controlled oscillator 19 is supplied as a reference signal to a phase synchronized oscillator 40 of the transmitting section.

Now, if the local frequency of the satellite repeater fluctuates by ΔF, all the signals of receiving frequencies fd+ to n will similarly fluctuate by ΔF, and therefore the received pilot wave (f(H) also fluctuates by ΔF).
The input frequency (referred to as fp) of the pilot receiving device also changes by ΔF. When the center frequency of the voltage controlled oscillator 19 is 61 and the output frequency of the crystal oscillator is fr, the following equation is obtained since the input frequencies of both the phase detectors 160 are equal in the phase synchronization state.

(a) When there is no frequency fluctuation frX M - fy X N = fp...
...... (]) (b) When the input frequency fp fluctuates by ΔF fr X M (fv+71) X N
= fp+ΔF-(2) where yl is the amount of correction from the center frequency fv of the voltage controlled oscillator 19.

Subtracting yl from the above equations (1) and (2), y1=-mutual ................................................................... (3
). Therefore, the input frequency f of the pilot receiver
When p changes by ΔF, the output frequency of the voltage controlled oscillator 19 decreases by ΔF/N. This voltage controlled oscillator 19
The output of phase-locked oscillator 4 is multiplied by N (phase-locked oscillator 2
1), the output frequency of the phase-locked oscillator 4 is lowered by ΔF. Therefore, modulator 1
The communication signal, which is the sum frequency of the phase-locked oscillator 4 and the phase synchronized oscillator 4, is transmitted to the satellite SAT with its frequency lowered by ΔF. This communication signal undergoes frequency fluctuation by ΔF at the satellite repeater, but at the receiving frequency (f(12-n)), the signals cancel each other out and always remain at a constant frequency.

On the other hand, the pilot frequency does not receive the above frequency correction because the signal is inserted at the output side of mixer 2.
The input frequency of the pilot receiver is as long as the local frequency of the satellite repeater is fluctuating.

It's always changing by that amount. In this way, the reception frequencies fd2 to fdn from the satellites excluding the pilot signals are always constant, so that the ship station can receive them without using a complicated AFO device. However, since this pilot receiving device uses two phase-locked oscillators in the microwave band, it has a drawback that the circuit is complicated and the shape is large.

Purpose of the Invention The present invention has been made based on the above considerations.
Therefore, an object of the present invention is to provide a new pilot receiving device that is simple, compact, and inexpensive to construct.

Structure of the Invention In order to achieve the above object, a pilot receiving device according to the present invention includes an output signal of a modulator in a first mixer.
After mixing with the output signal of the phase-locked oscillator and converting it to the first intermediate frequency, the output signal of the second phase-locked oscillator synchronized with the output of the first crystal oscillator is added as a pilot signal. In the mixer, the output signal of the third phase-locked oscillator synchronized with the output of the second crystal oscillator is mixed with the output signal of the third phase-locked oscillator, converted into a transmission frequency band signal, and then amplified with a power amplifier and supplied to the antenna. receives the received signal returned from the satellite repeater and amplifies it with a low-noise amplifier.
The third mixer mixes the output signal of the fourth phase synchronized oscillator synchronized with the output of the third crystal oscillator,
Satellite communication that converts the F-band signal and supplies it to the demodulator, extracts the received pilot signal from a part of the F-band signal, detects frequency fluctuations from the received pilot signal, and corrects the transmit frequency accordingly. At the earth station, a phase detector that compares the phase of the received pilot signal with the output of a phase-locked oscillator, a loop amplifier that amplifies the output voltage of the phase detector, and a voltage whose frequency is controlled by the output voltage of the loop amplifier. a controlled oscillator, a running mixer that mixes the output of the voltage controlled oscillator and the output of the crystal oscillator to obtain a difference frequency, and the phase synchronized oscillator for obtaining N-multiple waves synchronized with the output of the mixer. It is composed of:

3. Detailed Description of the Invention Next, a preferred embodiment of the present invention will be specifically described with reference to the drawings.

FIG. 2 is a block diagram showing an embodiment of a pilot receiving apparatus according to the present invention. In FIG. 2, the same parts as in FIG. 1 are given the same reference numerals, and the reference number n is I? This is a phase-locked oscillator.

The operation of the embodiment according to the present invention shown in FIG. 2 is as follows. Since everything other than the pilot receiving device (the part surrounded by the broken line) is the same as in FIG. 1, a description of its operation will be omitted. A part of the engineered F-band signal output from the mixer 12 is supplied to the pilot receiving device of the present invention, and the phase detector 16
It is compared with the output of the phase synchronized lifter O, and a DC voltage corresponding to the phase error is output. This DC voltage is applied to the voltage controlled oscillator 19 via another loop amplifier 18 that constitutes a phase locked loop, and controls its output frequency. The output of the voltage controlled oscillator 19 is mixed with the output of the crystal oscillator Yoshimi in the mixer 17, and the difference frequency is multiplied by N in the IP band phase synchronized oscillator Z and supplied to the phase detector 16. A part of the output of the voltage controlled oscillator 19 is supplied as a reference signal to the phase synchronized oscillator 4 of the transmitting section.

As in the case of Figure 1, the local frequency of the satellite repeater is ΔF
If the received pilot wave (f
al) also varies by ΔF, and as a result, the input frequency (denoted fp) of the pilot receiver also varies by ΔF. When the center frequency of the voltage controlled oscillator 19 is f's and the specific power frequency of the crystal oscillator is fr, the following equation is obtained since both input frequencies of the phase detector 16 are equal in the phase synchronization state.

(Q) When there is no frequency fluctuation (fr-fv) X N = fp Song...Song...=-(
4) (d) When fp fluctuates by ΔF (fr (fv +72)) X N = fp+Δ
I'-...-(5) However, y2 is the voltage controlled oscillator 19
is the amount of correction from the center frequency fv.

Subtracting y2 from equations (4) and (5).

ΔF 3'2=-7・・・・・・・・・・・・・・・・・・
(6) It is possible to obtain the same amount of correction as the conventional pilot receiver shown in FIG. 1. For this reason, as mentioned above, the satellite S
The reception frequencies fd2 to fdn from the AT can always be kept constant.

Effects of the Invention From the above, the present invention is more compact and inexpensive than conventional devices because it only requires one F-band phase-locked oscillator instead of two microwave-band phase-locked oscillators. It is effective as possible.

Also, in the above explanation, the transmission frequency is corrected by receiving the pilot wave transmitted from the own station, but if the pilot signal is stable enough, it is possible to receive the pilot signal transmitted from another station. Since it is possible to detect frequency fluctuations at the satellite repeater in exactly the same way, it goes without saying that it is possible to correct the transmission frequency of the own station.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a frequency control method using a conventional pilot receiving device, and FIG. 2 is a block diagram showing an embodiment using the pilot receiving device of the present invention. 1...Modulator, 2 and 3...Mixer, 4-6...
Phase synchronized oscillator, 7 and 8...Crystal oscillator, 9...
power amplifier, 10... duplexer, 11... low noise amplifier, 12... mixer, 13... phase synchronized oscillator, 1
4... Crystal oscillator, 15... Demodulator, 16... Phase detector, 17... Mixer, 18... Loop amplifier, 19... Voltage controlled oscillator, Adder... Crystal oscillator ,2
1 to 23... Phase-locked oscillator patent applicant NEC Corporation Representative Patent attorney Yutabe Kumagai NT Figure 1 NT Figure 2

Claims (1)

[Claims] After the output signal of the modulator is mixed with the output signal of the first phase-locked oscillator in a first mixer and converted to a first intermediate frequency, a second phase-locked signal synchronized with the output of the first crystal oscillator is generated. The output signal of the oscillator is added as a pilot signal, mixed in a second mixer with the output signal of a third phase-locked oscillator synchronized with the output of the second crystal oscillator, converted into a transmission frequency band signal, and then converted to a transmission frequency band signal. A fourth crystal oscillator synchronized with the output of the third crystal oscillator is amplified by a low-noise amplifier and amplified by a low-noise amplifier upon receiving the received signal reflected from the satellite repeater at the antenna. It is mixed with the output signal of the phase-locked oscillator, converted into a receiver F-band signal, and supplied to the demodulator, and a received pilot signal is extracted from a part of the receiver F-band signal, and the frequency fluctuation component is extracted from the received pilot signal. In a satellite communication earth station that detects and corrects the transmission frequency accordingly, a phase detector that compares the phase of the received pilot signal with the output of a phase synchronized oscillator, and a loop amplifier that amplifies the output voltage of the phase detector; a voltage controlled oscillator whose frequency is controlled by the output voltage of the loop amplifier; a mixer for mixing the output of the voltage controlled oscillator and the output of the crystal oscillator to obtain a difference frequency; and a mixer synchronized with the output of the mixer. A pilot receiving device comprising: the phase synchronized oscillator for obtaining N-multiplied waves.