JP2003028952A - Receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a PLL-type mounted on artificial-satellite receiver, in which the fluctuation in the delay time of a demodulating signal, as a distance measuring signal near a reception input threshold level, can be automatically compensated, when the distance of an artificial satellite is measured. SOLUTION: The receiver is constituted, in such a way that a phase shifter 10 used to compensate for the delay time of the demodulating signal is installed in the output part of the demodulating signal, and that the phase shifter is phase-controlled by an AGC voltage. That is to say, in a PLL-type receiver, calibration data on the cycle time of the demodulating signal is acquired near the reception input threshold level, the AGC voltage in the receiver is used as the phase control voltage of the phase shifter 10; and the phase shifter 10 is made operated to cancel the delay time of the demodulating signal near the input threshold level. Therefore, the delay time of the demodulating signal can be kept constant, even if it is near the input threshold level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver, and more particularly to a receiver having an automatic gain control (AGC) function, which receives and demodulates a ranging signal for ranging between a ground station and an artificial satellite. The present invention relates to a phase-locked loop type receiver for an artificial satellite or the like.

[0002]

2. Description of the Related Art In order to measure the distance between an artificial satellite and a ground station, a distance measuring signal is transmitted from the ground station using a PM modulation method or an FM modulation method, and the artificial satellite receives and demodulates the signal. After that, it modulates again and transmits to the ground station. Then, at the ground station, after receiving and demodulating this ranging signal, the phase difference between the transmitted ranging signal and the received ranging signal is detected,
It is designed to measure distance.

A conceptual diagram of such a distance measuring method is shown in FIG. In FIG. 5, the transmitter 51 of the ground station 50 modulates the uplink signal with the distance measurement signal 1 and transmits it to the artificial satellite 60. The artificial satellite 60 receives the uplink signal by the satellite receiver 61 and demodulates the ranging signal 2.
Next, the ranging signal 2 is re-modulated by the satellite-mounted transmitter 62 into a downlink signal and transmitted to the ground station 50. Ground station 50 receives the downlink signal at ground station receiver 52,
The ranging signal 3 is demodulated.

The ground station 50 measures the phase difference Δφ (degrees) between the distance measurement signal 1 and the distance measurement signal 3 to calculate the propagation delay time Δτ between the ground station 50 and the artificial satellite 60. You can learn from In the equation (1), f indicates the frequency of the distance measuring signal, and T indicates the period of the distance measuring signal.

Since Δτ in the equation (1) includes the propagation delay times of all the route parts shown in FIG. 5, the free space aliasing propagation delay time (τu) between the ground station 50 and the artificial satellite 60.
+ Τd) can be obtained from τu + τd = Δτ- (τ1 + τ2) (2). Where τu: Propagation delay time of ranging signal of uplink signal τd: Propagation delay time of ranging signal of downlink signal τ1: Propagation delay time calibration data of ranging signal at ground station τ2: Distance measurement at artificial satellite It is assumed that the signal is propagation delay time calibration data.

The free space propagation distance (one way) R between the ground station 50 and the artificial satellite 60, where C is the speed of light,
From the equations (1) and (2), R = (τu + τd) · C / 2 = {Δφ · T / 360− (τ1 + τ2)} · C / 2 (3) can be obtained.

Therefore, if a phase error occurs in the demodulated ranging signals of the artificial satellite and the ground station, an error will occur in τ1 and τ2, and the accuracy of the free space propagation distance R will deteriorate.
Therefore, the receiver that demodulates the ranging signal is required to have a small delay time variation of the demodulated signal.

FIG. 6 is a block diagram showing an example of a satellite receiver 61 in the artificial satellite 60 shown in FIG. In the figure, an example of a PLL type PM receiver is shown. A PLL circuit is configured by a detector 3, an LPF 7, and an oscillator 8, and a gain control type amplifier 1, a π / 2 phase shifter 4, and a detector 5 are shown. , LPF9 form an AGC circuit. Further, the wave detector 2 and the LPF 6 constitute a demodulation circuit. The above circuits are well known and will not be described here.

[0009]

In the PLL receiver shown in FIG. 6, the phase of the demodulated signal changes abruptly near the reception input threshold level. Therefore, in order to keep the delay time of the demodulated ranging signal constant even near the reception input threshold level, the ground station 5
At 0, it is necessary to read the AGC voltage of the satellite receiver 61 from the telemetry data from the artificial satellite 60 and correct the delay time of the demodulated signal, which is a disadvantage in that it takes time and effort at the ground station.

Furthermore, since such a conventional correction method is premised on the correction at the ground station, it is possible that the AGC voltage data of the satellite receiver cannot be properly acquired depending on the operating conditions of the ground station. In this case, the ground station cannot correct the delay time fluctuation of the distance measurement signal, which causes a problem that the distance measurement accuracy deteriorates.

It is an object of the present invention to provide a PLL type receiver capable of automatically compensating for a demodulation delay time variation of a demodulation signal of a ranging signal near a reception input threshold level.

[0012]

According to the present invention, there is provided a phase locked loop type receiver having an automatic gain control (AGC) function for receiving and demodulating a ranging signal. A receiver characterized by including phase control means for controlling the phase of the demodulated output of the distance measurement signal is obtained.

Further, the phase control means controls the phase so as to compensate for the phase fluctuation of the demodulation output near the threshold level of the reception input, and the distance measurement signal is PM or FM modulated. , PM or FM demodulation function. Further, the distance measurement signal is a signal for distance measurement between the ground station and the artificial satellite, and is characterized by being mounted on the artificial satellite.

The operation of the present invention will be described. A phase shifter for compensating the delay time of the demodulated signal is provided at the output portion of the demodulated signal, and the phase shifter is configured to control the phase by the AGC voltage.
That is, first, in the PLL type receiver, the calibration data of the demodulated signal delay time is acquired near the reception input threshold level, and then the AGC voltage of the receiver is used as the phase control voltage of the phase shifter, and the input The phase shifter is operated so as to cancel the demodulation signal delay time near the threshold level. Due to this, the demodulated signal delay time can be kept constant even near the input threshold level.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and the same portions as those in FIG. 6 are designated by the same reference numerals. The part different from the configuration of FIG. 6 is that the phase shifter 10 is inserted in the output part of the LPF 6 constituting the demodulation circuit, and the phase control of this phase shifter 10 is performed by the AGC voltage obtained by the AGC circuit. It was done like this. Other parts are the same as in FIG.

The PLL circuit is for synchronizing the reference signal (the output of the oscillator 8) with the carrier wave of the received input signal, and based on this reference signal, the received input signal is synchronously detected by the detector 2 and demodulated. It is like this. The AGC circuit is for keeping the level of the received input signal constant, and controls the reference signal by π / 2 phase shift by the π / 2 phase shifter 4, and the amplifier 1 for this phase shift control output and the received input signal. The signal that has passed through is multiplied by the detector 5 and the multiplication output is
The gain control of the gain control type amplifier 1 is performed by using the AGC voltage via 9

The present invention utilizes the fact that the reception input level can be known by this AGC voltage, and the phase of the demodulation output of the LPF 6 is compensated by the phase shifter 10 using this AGC voltage. Is. That is, this AGC voltage compensates for the delay time of the demodulated signal near the reception input threshold level to be constant.

FIG. 2 is a circuit diagram showing a specific example of the phase shifter 10 shown in FIG. 1, which includes resistors R1 to R3, an operational amplifier OP1, and
It is composed of a variable capacitance diode C1. When the control voltage to the variable capacitance diode C1 is changed, its capacitance value is changed and the time constant of C1 and R1 is changed, so that the phase of the output signal with respect to the input signal of the phase shifter can be controlled. .

With the phase of the phase shifter 10 of FIG. 1 fixed, the calibration data of the demodulation signal delay time with respect to the received input level is acquired as shown by the solid line in FIG. Next, near the reception input threshold level, the AGC voltage is used as the phase control voltage of the phase shifter 10 so as to cancel the demodulation signal delay time. As a result, FIG.
As shown by the dotted line in (1), the demodulation signal delay time can be compensated so as to be constant even near the reception input threshold level.

FIG. 4 is a block diagram of another embodiment of the present invention, in which the same parts as in FIG. 1 are designated by the same reference numerals. Although the example of FIG. 1 was for the PLL type PM receiver,
This example is a PLL type FM receiver. Also in this example, in order to control (compensate) the phase of the FM demodulated signal,
The phase shifter 10 is inserted and the phase shifter 10 is controlled by the AGC voltage.

In the figure, in the FM received signal, P
Since the output of the LPF 6 of the LL circuit becomes a demodulation signal, the detector 2, the LPF 6, and the oscillator 8 also serve as the PLL circuit and the demodulation circuit. The output of the amplifier 1 is detected by the non-coherent AGC circuit 11 and the detected level is used as the AGC voltage, thereby forming the AGC circuit. This AGC voltage is the control signal for the phase shifter 10, as in the previous embodiment shown in FIG. The non-coherent AGC circuit 11 is a simple and well-known diode detection type.

Also in this embodiment, as shown in FIG. 3, it is clear that the delay time of the demodulated signal can be kept constant near the input threshold level.

[0023]

As described above, according to the present invention, the delay of the demodulated signal is delayed by a simple structure in which the phase shifter additionally provided in the demodulated signal system of the satellite-mounted receiver is controlled by the AGC voltage. Since the time fluctuation is automatically compensated in the vicinity of the reception input threshold level, there is an effect that a PLL type receiver capable of keeping the delay time fluctuation of the demodulated signal constant can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an example of a phase shifter used in the present invention.

FIG. 3 is a diagram showing an example of improving delay time fluctuation of a demodulated signal by the PLL receiver of the present invention.

FIG. 4 is a block diagram showing the configuration of another embodiment of the present invention.

FIG. 5 is a schematic diagram showing a method for measuring the distance of an artificial satellite.

FIG. 6 is a diagram showing an example of a conventional PLL receiver.

[Explanation of symbols]

1 Gain control type amplifier 2,3,5 detector 4 π / 2 phase shifter 6,7,9 LPF 8 oscillators 10 Phase shifter 11 Non-coherent AGC circuit

Claims (4)

[Claims] 1. A phase locked loop receiver having an automatic gain control (AGC) function for receiving and demodulating a ranging signal, the demodulation output of the ranging signal using an AGC control voltage. A receiver including phase control means for performing phase control. 2. The phase control means controls the phase so as to compensate the phase fluctuation of the demodulation output near the threshold level of the reception input.
Receiver described in. 3. The receiver according to claim 1, wherein the distance measurement signal is PM or FM modulated and has a PM or FM demodulation function. 4. The range finding signal is a signal for range finding between a ground station and an artificial satellite, and is mounted on the artificial satellite. Receiver.