JPH05292000A - Method and device for abnormal detection for spread spectrum satellite signal receiver - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve the operational reliability of spread spectrum satellite signal receivers. A frequency conversion amplifier 4 is provided which converts a spread spectrum signal from an artificial satellite received by an antenna 1 and input through a coaxial cable 2 into an analog signal having a predetermined frequency and amplitude and outputting the analog signal. In the spread spectrum satellite signal receiving device, the output of the frequency conversion amplifier 4 is branched and input, and the signal level measuring circuit 5 that measures the amplitude thereof is compared with the amplitude of the measured analog signal and a predetermined amplitude range, An abnormality detection circuit 6 that outputs a signal indicating a normal state if the amplitude of the analog signal is within the above range and an abnormal state if outside the range is provided to detect an abnormality in each component or a connection state thereof. To do.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum satellite signal receiving apparatus for receiving radio waves transmitted from artificial satellites (hereinafter simply referred to as satellites) and performing required signal processing.

[0002]

2. Description of the Related Art An input section of a spread spectrum satellite signal receiving apparatus, that is, a down converter which is an analog circuit section, comprises at least an antenna and a frequency conversion amplifier.

The antenna is usually placed away from the frequency conversion amplifier in order to effectively receive the weak signal from the satellite. Therefore, if the coaxial cable that connects the two is long, its loss causes a signal-to-noise ratio (SN
Ratio). Therefore, conventionally, in this type of receiving device, the above-mentioned loss is compensated by integrating the low noise amplifier part of the frequency conversion amplifier as a preamplifier with the antenna. In this case, the coaxial cable plays a role of amplifying the satellite signal received by the antenna with the preamplifier and sending it to the frequency conversion amplifier, and also supplying the power for preamplifier from the frequency conversion amplifier to the preamplifier through the coaxial cable.

In addition, this kind of spread spectrum satellite signal receiving apparatus is usually provided with an abnormality diagnosing apparatus. This abnormality diagnosis device detects the current supplied from the frequency conversion amplifier to the preamplifier, and performs abnormality detection by a method of determining whether or not the detected current value is within a predetermined normal range. For example, when the current value is out of the normal range due to an excessive current or an excessive current, it is determined that there is a coaxial cable connection error or the like.

[0005]

However, in the conventional abnormality diagnosing device, since the abnormality is detected by detecting the current supplied to the preamplifier, the frequencies constituting the antenna, the preamplifier and the frequency conversion amplifier are detected. Abnormalities in the entire down converter such as the conversion circuit and amplification circuit cannot be detected. Therefore, there is a problem that the operation reliability of the spread spectrum satellite signal receiving apparatus having this is low.

The present invention has been made in view of the above problems, and an object thereof is to provide an abnormality detecting method capable of detecting an abnormality in the entire down converter.

Another object of the present invention is to provide a spread spectrum satellite signal receiving apparatus which detects an abnormality in the entire down converter and improves its operation reliability.

[0008]

According to the abnormality detecting method of the present invention, the step of measuring the amplitude of an analog signal output from a frequency conversion amplifier is compared with the amplitude of the measured signal and a predetermined amplitude range. And a means for outputting a signal according to the comparison result. If the amplitude of the analog signal is within a predetermined range, it indicates a normal state of the spread spectrum satellite signal receiving device, and if it is outside the range, it is in an abnormal state. It is characterized in that a signal representing is output.

The spread spectrum satellite signal receiving apparatus of the present invention includes an antenna for receiving a spread spectrum signal from an artificial satellite and an analog signal having a predetermined frequency and amplitude by inputting the signal received by this antenna through a cable. In a spread spectrum satellite signal receiving device having at least an input part thereof which has a frequency conversion amplifier for converting and outputting to a signal, a signal level measuring circuit for measuring the amplitude of an analog signal output from the frequency conversion amplifier,
The amplitude of the analog signal measured by this signal level measuring circuit is compared with a predetermined amplitude range, and as a result of the comparison, if the amplitude of the analog signal is within the range, it indicates a normal state, and if the amplitude is out of the range. If any, an abnormality detecting means for outputting a signal indicating an abnormal state is provided.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a preferred embodiment of a spread spectrum satellite signal receiving apparatus according to the present invention, a GPS (Global Positioning Sys) which is a position measuring system using satellites will be described below.
tem, Global Positioning System) receiver will be described with reference to the accompanying drawings.

FIG. 1 is a block diagram of the GPS receiver of this embodiment. 1 is an antenna, 2 is a preamplifier, 3 is a coaxial cable, 4 is a frequency conversion amplifier, 5 is a signal level measuring circuit, and 6 is an abnormality detecting circuit. Is. The frequency conversion amplifier 4 is
It comprises at least an RF (high frequency) filter 41, a frequency conversion circuit 42, a local oscillation circuit 43, an IF (intermediate frequency) amplification circuit 44, and a bandpass filter 45.

First, radio waves transmitted from GPS satellites will be described. There are a total of 24 GPS satellites when the system is completed, and 6 with an orbital altitude of about 20,000 [km].
It has been launched into two orbital planes. Here, of the radio waves transmitted from the GPS satellites, those in the L1 band, that is,
Bandwidth of about 2 [MHz] spectrum-spread with a pseudo noise code (PN code) with a chip rate of 1.023 [MHz] called C / A (Clear and Acquisition) code,
A radio wave having a center frequency of 1575.42 [MHz] will be described below as an example.

Radio waves in the L1 band transmitted from GPS satellites are received by an antenna 1 of the same type as an antenna installed in a moving body such as a ship or an automobile, and converted into an electric signal. Hereinafter, this is referred to as a GPS signal. The reception power of this GPS signal obtained from the antenna 1 is usually about -130 [d
Bm].

On the other hand, the total noise power of the receiver system includes the noise generated in the antenna 1 and the preamplifier 2, the coaxial cable 3,
It is a noise power obtained by converting the total noise generated in the frequency conversion amplifier 4 into the input of the preamplifier 2, and is about -110 [dBm] in the bandwidth 2 [MHz] of the GPS signal.
Therefore, the GPS signal-to-noise ratio (SN ratio) is -20 [d
B], and the GPS signal is input to the preamplifier 2 while being buried in the receiver system total noise. In other words, since the GPS signal is sufficiently smaller than the receiver system total noise and can be ignored, it can be considered that the power handled by the down converter is due to the receiver system total noise.

This is a feature of the down converter of the spread spectrum satellite signal receiving apparatus. The down converter frequency-converts and amplifies a weak signal buried in noise together with the receiver system total noise, and apparently handles noise power. It will be.

The role of the preamplifier 2 is to compensate for the loss of the coaxial cable 3 which leads its output to the frequency conversion amplifier 4 and prevent the noise figure of the down converter from deteriorating. If the amplification degree of the prep amplifier 2 is 30 [dB], both the GPS signal and noise are amplified by 30 [dB].

The coaxial cable 3 sends the output of the preamplifier 2 to the frequency conversion amplifier 4 with low loss, and also supplies the power from the frequency conversion amplifier 4 to the preamplifier 2.

The frequency conversion amplifier 4 eliminates out-of-band noise of the output power of the preamplifier 2 guided through the coaxial cable 3.
First, it is filtered by the RF filter 41, and then the frequency conversion circuit 4
In step 2, it is mixed with the local oscillation signal generated in the local oscillation circuit 43 and converted into an IF frequency of several MHz, for example 3 [MHz]. After that, the signal is further amplified to a predetermined level by the IF amplifier circuit 44, limited to a band of 2 [MHz] by a band pass filter 45 having a bandwidth of 2 [MHz], and then output to the signal level measuring circuit 5. This output is also output to a signal processing circuit (not shown). The overall amplification degree of the frequency conversion amplifier 4 is usually about 100 [dB].

The signal level measuring circuit 5 measures the total noise voltage of the receiver system amplified by the frequency conversion amplifier 4 and band-limited to 2 [MHz]. Usually, a logarithmic amplifier is used for the circuit 5 in order to widen the dynamic range.

FIG. 2 is a characteristic diagram of the signal level measuring circuit 5, showing an example of the relationship between the input voltage [dBm] of the frequency conversion amplifier 4 and the output voltage [V] of the signal level measuring circuit 5. For example, in this circuit 5, the input power is −
A voltage of about 1.2 [V] is output at a level below 100 [dBm], a voltage of about 4.8 [V] is output at a level of -40 [dBm] or higher, and an intermediate level is input. It outputs an analog voltage proportional to the power.

The abnormality detecting circuit 6 receives the output voltage of the signal level measuring circuit 5 as input, compares it with a predetermined normal voltage range, detects whether the down converter is normal or abnormal, and shows the result. Output a binary signal to the outside.

FIG. 3 is an explanatory diagram of an abnormality detecting method by the device having the above-mentioned configuration. In the down converter shown in FIG. 1, the relation between the loss of the coaxial cable 3 and the output voltage of the signal level measuring circuit 5 is the abnormality of the down converter. It shows how it changes depending on the state. In FIG. 3, when the down converter is normal, the antenna 1 and the preamplifier 2 are
If the connection with is poor, the preamplifier 2 and the coaxial cable 3
The case where the connection with is poor is also shown.

This embodiment will be described with reference to this figure as an example.
If the range in which the operation of the down converter is judged to be normal is set in advance to the range of 2.5 [V] to 3 [V], the abnormality detection circuit 6 is normal when the voltage of the signal level detection circuit 5 is within the above range. Then, as a detection output, a High signal, for example, a voltage signal of +5 [V] is output. On the other hand, the voltage of the signal level measuring circuit 5 is less than 2.5 [V], or 3
When it exceeds [V], it is determined to be abnormal, and a Low signal, for example, a voltage signal of 0 [V] is output as a detection output. Therefore, the down converter abnormality diagnosis can be performed by detecting these voltage signals.

As described above, in the present embodiment, not only the connection failure of the coaxial cable as in the conventional case but also the antenna 1 is used.
It is possible to detect the failure of the entire down converter including the connection failure between the preamplifier 2 and the preamplifier 2 and improve the reliability of the GPS receiver.

The abnormality detection circuit 6 may be constructed by hardware, or the same function may be realized by software.

[0026]

As described above in detail, in the abnormality detecting method of the present invention, the amplitude of the analog signal output from the frequency conversion amplifier is measured, and if the amplitude is within the predetermined range, the normal state is obtained. If the amplitude is out of the range, a signal indicating an abnormal state is output.Therefore, it is possible to detect an abnormality in the down converter as a whole, such as an abnormality in the antenna, preamplifier, or frequency conversion amplifier alone, or a connection failure between them. There is an effect that becomes possible.

Further, in the spread spectrum satellite signal receiving apparatus of the present invention, the circuit for realizing the above method is provided and it is possible to detect the abnormality of the entire down converter. Therefore, the operation reliability is remarkably improved as compared with the conventional apparatus. Has the effect of

[Brief description of drawings]

FIG. 1 is a configuration diagram of a down converter of a GPS receiver according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram of a signal level measuring circuit used in this embodiment.

FIG. 3 is an explanatory diagram of an abnormality detection method according to this embodiment.

[Explanation of symbols]

 1 Antenna 2 Preamplifier 3 Coaxial cable 4 Frequency conversion amplifier 5 Signal level measurement circuit 6 Abnormality detection circuit 41 RF filter 42 Frequency conversion circuit 43 Local oscillation circuit 44 IF amplification circuit 45 Band pass filter

Claims (2)

[Claims] 1. A frequency conversion amplifier for converting a spread spectrum signal from an artificial satellite received by an antenna and input via a cable into an analog signal having a predetermined frequency and amplitude and outputting the analog signal. A method for detecting an abnormality in a spread spectrum satellite signal receiving device, comprising: comparing the amplitude of the analog signal output from the frequency conversion amplifier with a predetermined amplitude range And a step of outputting a signal according to the result, wherein if the analog signal has an amplitude within a predetermined range, it indicates a normal state of the spread spectrum satellite signal receiving device, and if the amplitude is out of the range, it indicates an abnormal state. A method for detecting an abnormality in a spread spectrum satellite signal receiving device, characterized in that a signal indicating the above is output. 2. An antenna for receiving a spread spectrum signal from an artificial satellite, and a frequency conversion amplifier for inputting a signal received by this antenna through a cable, converting it into an analog signal of a predetermined frequency and amplitude, and outputting the analog signal. In a spread spectrum satellite signal receiving device having at least its input part, a signal level measuring circuit for measuring the amplitude of an analog signal output from the frequency conversion amplifier, and an analog signal measured by the signal level measuring circuit. Of the analog signal is compared with a predetermined amplitude range, and if the result of the comparison is that the amplitude of the analog signal is within the range, it indicates a normal state, and if the amplitude is out of the range, a signal indicating an abnormal state is output. A spread spectrum satellite signal receiving apparatus, characterized in that a detecting means is provided.