JPH09298570A - Receiver - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] A receiver that performs stable synchronization and carrier recovery using a reference signal in a transmission path in which the received signal strength changes temporally due to rain attenuation or fading during mobile reception. On the other hand, in the conventional device, it takes a long time to initially capture the received signal, the frequency drift range that can be captured is narrow, and stable operation cannot be obtained at a low CN ratio. A reference signal in the intermediate frequency band, which has the same waveform as a reference signal sent from a transmission side, and a frequency converter 9 for frequency-converting the output of the reception antenna into a signal in the intermediate frequency band. , The intermediate frequency correlator 12 that correlates between the frequency converter output and the reference signal generator output, and the quadrature detection whose correlator output is supplied as the detected wave input. Vessel 14,
A phase-locked loop in which a voltage-controlled oscillator 15 and a frequency doubler 16 are connected and arranged in an annular shape is provided, and an output of the frequency converter 9 is output from an output side of the voltage-controlled oscillator 15 included in the phase-locked loop. The carrier wave for quadrature detection is reproduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a reference signal for stable transmission in a transmission line (regardless of modulation format) in which the received signal strength fluctuates with time due to rain attenuation or fading during mobile reception. It is possible to synchronize and reproduce the carrier wave, which in turn shortens the initial acquisition time,
The present invention relates to a receiving device capable of expanding a frequency drift range that can be captured.

[0002]

2. Description of the Related Art As an example of spread spectrum multiplexing of a PN signal to be transmitted as a reference signal, Hiroyuki Hamazumi,
Yasuhiro Ito, Hiroshi Miyazawa: "Adaptive weighted CDM transmission system for terrestrial digital television broadcasting", TV journal VOL.47. No.
10. pp.1367-1373 (1993).

As can be seen from these examples, conventionally, in a transmission line in which the received signal strength fluctuates with time due to rainfall attenuation, fading during mobile reception, etc., from the transmitting side by time division multiplexing or spread spectrum multiplexing. When stable synchronization and carrier recovery are performed using the transmitted reference signal, as shown in FIG. 4, a received signal is first detected and then a correlator is used for the transmitted reference signal and its own reference signal. There is a known method for obtaining correlation.

That is, in FIG. 4, the transmitted transmission signal is captured by the receiving antenna 1 and supplied to the frequency converter 2. A local oscillation signal is supplied from the oscillator 3 to the frequency converter 2 and outputs a signal in the intermediate frequency band. This output is quadrature detected by the quadrature detector 4 to obtain a demodulation output.

In this case, when the received signal strength temporally fluctuates due to rainfall attenuation or fading, it is necessary to supply the quadrature detector with the reference signal for demodulation and the reference signal in phase synchronization. . Therefore, in FIG. 4, a reference signal having the same waveform as that of the reference signal generated on the transmission side is generated by the reference signal generator 5 and supplied to the correlator 6 together with the demodulation output, so that the correlation between the two signals is generated. Take The correlation output is supplied to a voltage controlled oscillator (hereinafter referred to as VCO) 7 and generates a carrier wave as a reference signal of the quadrature detector 4. Here, the loop composed of the quadrature detector 4, the correlator 6 and the VCO 7 is a phase locked loop (hereinafter referred to as PLL).
Is composed.

[0006]

As described above, when the reference signal is subjected to correlation calculation on the receiving side, the conventional receiving apparatus as shown in FIG. 3 uses the correlator after detection, It is necessary to put a correlator, which is a large delay element, inside the PLL loop for carrier recovery,
Therefore, there is a problem that the initial acquisition of the PLL takes time and the frequency range that can be acquired is narrowed. On the other hand, since it is necessary to detect a signal before correlation calculation that is buried in noise, there is a problem that a detection error becomes large at a very low CN ratio and stable operation of the receiving device becomes difficult. .

It is an object of the present invention to provide a receiving apparatus of the type described above which makes it possible to significantly reduce the time required for the initial acquisition of a received signal, expand the range of frequency drift that can be acquired, and operate at a low CN ratio. To provide.

[0008]

To achieve the above object, in a conventional receiving apparatus, a correlation calculation is performed after detection (quadrature detection) of a received signal, and a correlator for performing the correlation calculation is a PLL. In the receiving apparatus of the present invention, the correlation calculation is performed before the detection and the correlator is P
The structure is arranged outside the loop of LL.

That is, the receiving apparatus of the present invention receives, on the transmitting side, a transmission signal which is transmitted by multiplexing a reference signal by time division multiplexing or spread spectrum multiplexing, and compares the received reference signal with its own reference signal. A receiver capable of shortening an initial acquisition time, expanding a frequency drift range that can be acquired, and operating at a low CN ratio by taking a correlation, the receiving device including a reception antenna and the reception antenna. A first frequency converter for frequency-converting an antenna output into a signal in the intermediate frequency band; a reference signal generator having the same waveform as the reference signal for generating a reference signal in the intermediate frequency band; and the frequency conversion Frequency correlator that correlates between the output of the reference signal and the output of the reference signal generator, a quadrature detector to which the output of the correlator is supplied as the detected input, a first voltage controlled oscillator and a frequency And a quadrature detection circuit for outputting the output of the first intermediate frequency converter from the output side of the first voltage controlled oscillator included in the phase locked loop. It is characterized in that the carrier wave for reproducing is reproduced.

Further, in the receiver of the present invention, in the phase locked loop, a sample hold circuit and a phase detector are further arranged in cascade between the quadrature detector and the first voltage controlled oscillator. In addition, the receiving device further includes an envelope detector for performing envelope detection of the output of the intermediate frequency correlator and using the detected output as a trigger signal of the sample hold circuit. It is characterized by including.

In the receiving apparatus of the present invention, the receiving apparatus further includes an FM demodulator for FM demodulating the output of the intermediate frequency correlator, and the FM demodulator and the first frequency converter. And a second voltage controlled oscillator arranged to generate a local oscillator signal of the frequency converter.

Further, the receiving apparatus of the present invention receives, on the transmitting side, a transmission signal which is transmitted by multiplexing a reference signal by time division multiplexing or spread spectrum multiplexing, and compares the received reference signal with its own reference signal. By taking the correlation,
What is claimed is: 1. A receiving device capable of shortening an initial acquisition time, expanding a frequency drift range that can be acquired, and operating at a low CN ratio, the receiving device including a reception antenna and an output of the reception antenna in an intermediate frequency band. Frequency converter for converting the frequency of the reference signal, a reference signal generator having the same waveform as the reference signal and generating a reference signal in the intermediate frequency band, the frequency converter output and the reference signal An intermediate frequency correlator that takes a correlation with the generator output, an envelope detector that performs an envelope detection of the intermediate frequency correlator output, and a difference device that takes a difference in time series with respect to the envelope detector output, At least a third voltage controlled oscillator controlled by the differencer output is provided, and a synchronous output is reproduced from the output side of the third voltage controlled oscillator.

In the receiving apparatus of the present invention, the reference signal generator is supplied with a baseband reference signal generator and an output of the reference signal generator to convert the output signal into an intermediate frequency band reference signal. And an intermediate frequency band modulator of (1).

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on embodiments of the present invention with reference to the accompanying drawings. A first embodiment of the receiving apparatus of the present invention is shown in a block diagram in FIG. In FIG. 1, 8 is a receiving antenna, 9 is a frequency converter, 10 is a VCO, 11 is an FM demodulator, 12 is an intermediate medium wave correlator, 13 is a reference signal generator, 14 is a quadrature converter, 1
5 is a VCO, 16 is a frequency doubler, and 17 is a quadrature detector.

The operation will be described below. A transmission signal in which a reference signal such as a frequency sweep signal (chirp), sinx / x, PN is time division multiplexed or spread spectrum multiplexed is
The output signal captured by the reception antenna 8 is converted into a signal in the intermediate frequency band by the frequency converter 9. A local signal from the VCO 10 is supplied to this frequency conversion circuit. A signal obtained by FM demodulating an output from an intermediate frequency correlator 12 described later by an FM demodulator 11 is supplied to the VCO 10, and the oscillation frequency is controlled.

On the other hand, the intermediate frequency correlator 12 such as a SAW convolver has the same waveform as the reference signal supplied from the reference signal generator 13 and multiplexed on the transmitting side, and is equal to the output frequency of the frequency converter 9. The reference signal in the intermediate frequency band and the output signal of the frequency converter 9 are supplied and the correlation between both signals is obtained. The output signal of the intermediate frequency correlator 12 is supplied to the quadrature detector 7 as a detected wave input signal. Since this signal has a frequency twice that of the intermediate frequency band signal, the output signal of the VCO 15 is output. Is supplied to the frequency doubler 16 and is supplied to the quadrature detector 14 as a reference signal for detection.

From the quadrature detector 14, the in-phase component (I :) detected for the above correlation (output of the intermediate frequency correlator 6) is detected.
cosφ) and the quadrature component (Q: sinφ), the phase φ is further calculated and output. This phase φ is the VCO of the next stage
15 and controls its oscillation frequency. VCO1
The oscillation output of 5 supplies the signal in the intermediate frequency band, which is the output of the frequency converter 9, to the quadrature detector 17 and is used as a reference signal for signal demodulation by quadrature detection. Also, V
The output of the CO 15 is also sent to the frequency doubler 16 to generate a reference signal for the quadrature detector 14.

In FIG. 1, the quadrature detector 14 and the VCO 1
5 and the frequency doubler 16 constitute a PLL circuit, and the phase φ becomes zero in a steady state by the correct operation of this loop. In this state, V
The CO 15 supplies the quadrature detector 17 to regenerate a carrier wave that is correctly synchronized for quadrature detection of the intermediate frequency band signal (output signal of the frequency converter 9). As a result, the quadrature detector 17 can obtain a stable demodulated output that has been quadrature detected using the correct carrier as a reference signal.

In the first embodiment of the present invention described above, the correlation calculation by the correlator 12 is performed before the detection of the signal in the intermediate frequency band by the quadrature detector 17, and the intermediate frequency correlator 12 performs the quadrature calculation. Note that it is located outside the PLL loop consisting of the detector 14, the VCO 15 and the frequency doubler. As a result, the time required for the initial acquisition of the received signal is significantly shortened, and the AFC
When combined with a circuit, the frequency drift range that can be captured can be expanded, and operation at a low C / N ratio can be enabled.

Next, a block diagram of a more practical circuit example including a circuit for reproducing not only a carrier wave but also a synchronizing signal necessary for processing a digital signal is shown as a second embodiment of the receiving apparatus of the present invention. As shown in FIG. 2, this will be described below. 2, the same parts as those in FIG. 1 are designated by the same reference numerals. Moreover, in FIG.
The signal waveform of the portion shown in (g) is shown with the time axis aligned with the signal waveform diagram of FIG.

Further, in FIG. 2, the intermediate frequency correlator 1
2, FM demodulator 11, VCO 10 and frequency converter 9
Since the route for tracing is already described in FIG. 2, its description is omitted here.

The intermediate frequency correlator 12 modulates the reference signal generated by the baseband reference signal generator 18 (see FIG. 4A) by the intermediate frequency band modulator 19 from the transmitting side. A signal modulated into an intermediate frequency band signal of the same modulation format as that of the format (see FIG. 4B), and a reception signal converted into an intermediate frequency band signal by the frequency converter 9 (see FIG. 4C). Acts to correlate with. The output of the intermediate frequency correlator 12 (see FIG. 4D) is
Since the frequency of the signal in the intermediate frequency band is doubled by taking the correlation with the received signal, the oscillation output generated by the VCO 15 is doubled in frequency by the frequency doubler 16 and supplied to the quadrature detector 14. Then, the output of the intermediate frequency correlator 12 is subjected to quadrature detection.

Both the in-phase (I) component and the quadrature (Q) component (see FIG. 4E), which are quadrature detection outputs, are both detected by the envelope detector 2.
The sampled and held I output cosφ by the sample and hold circuit 21 triggered by the output of the intermediate frequency correlator whose envelope is detected by 0.
And the Q output sin φ are used to detect the phase φ by the phase detector 22, and this is used as the control signal of the VCO 15. When this VCO 15 is correctly controlled, φ = 0 and a correct carrier wave is reproduced, so that quadrature detection is correctly performed.

On the other hand, the output of the intermediate frequency correlator is envelope-detected by the envelope detector 20, and the detected output becomes the clock timing itself. Further, this detection output (see FIG. 4 (f)) is time-series differentiated by the differentiator 23, and an S-curve signal suitable for signal control (FIG. 4 (g)).
(See) and control the VCO 24 to obtain a clean synchronous output as the VCO output signal.

Also in the second embodiment of the present invention described above, the correlation calculation is performed before detection of the received signal (received signal in the intermediate frequency band), and the intermediate frequency correlator is arranged outside the PLL loop. ing. Therefore, in this embodiment, it is clear that the same or more effects as those described in the first embodiment can be obtained, and in the present embodiment, the synchronous output can be obtained. This is a point not found in the first embodiment.

[0026]

As described above, according to the present invention,
When receiving a signal multiplexed with a reference signal and performing synchronization and carrier recovery, a correlation operation can be performed in the intermediate frequency band before detection by using an intermediate frequency correlator, and a PLL for carrier recovery can be used. Since the correlation calculation can be performed outside the loop, the time required for the initial acquisition can be significantly shortened, and the range of frequency drift that can be acquired can be expanded by using the AFC circuit together. Further, since the influence of the detection error due to the detection of the signal before the correlation calculation, which is buried in the noise, does not enter the loop of the PLL, the operation under the low CN ratio becomes possible. That is, it is possible to shorten the time required for the initial complement of the PLL, which could not be realized by the conventional method of performing the correlation calculation after detection, and to operate when there is a large amount of frequency drift or at a lower CN ratio.

As a preferred application example of the present invention, the receiving apparatus of the present invention relaxes requirements such as frequency drift for a receiver converter for digital satellite broadcasting which will be realized in the near future, and improves receiver reliability. It will be an extremely useful technology for improving

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of a receiving device of the present invention.

FIG. 2 is a block diagram showing a second embodiment of the receiving apparatus of the present invention.

FIG. 3 shows signal waveforms at respective portions in the receiver of the present invention shown in FIG.

FIG. 4 shows a block diagram of a conventional receiving device.

[Explanation of symbols]

 8 reception antenna 9 frequency converter 10 voltage controlled oscillator (VCO) 11 FM demodulator 12 intermediate frequency correlator 13 reference signal generator (intermediate frequency band) 14 quadrature detector 15 voltage controlled oscillator (VCO) 16 frequency doubler 17 Quadrature detector 18 Reference signal generator (baseband) 19 Intermediate frequency band modulator 20 Envelope detector 21 Sample hold circuit 22 Phase detector 23 Difference device 24 Voltage controlled oscillator (VCO)

Claims (5)

[Claims] 1. A transmission side receives a transmission signal transmitted by multiplexing a reference signal by time division multiplexing or spread spectrum multiplexing, and correlates the received reference signal with its own reference signal, What is claimed is: 1. A receiving device capable of shortening an initial acquisition time, expanding a frequency drift range that can be acquired, and operating at a low CN ratio, the receiving device including a receiving antenna and an output of the receiving antenna in an intermediate frequency band. A first frequency converter for performing frequency conversion into a signal, a reference signal generator having the same waveform as the reference signal, and generating a reference signal in the intermediate frequency band, the frequency converter output and the reference signal An intermediate frequency correlator that correlates with the output of the generator, a quadrature detector to which the correlator output is supplied as a detected wave input, a first voltage controlled oscillator and a frequency doubler are connected in a loop. And a phase-locked loop configured to regenerate a carrier wave for quadrature-detecting the output of the first intermediate frequency converter from the output side of the first voltage-controlled oscillator included in the phase-locked loop. A receiving device characterized in that 2. The receiving device according to claim 1, wherein the phase lock loop includes the quadrature detector and the first quadrature detector.
Further, a sample hold circuit and a phase detector that are sequentially arranged in series are inserted between the voltage controlled oscillator of the above, and the receiving device further detects the output of the intermediate frequency correlator by envelope detection. Then, the receiver includes an envelope detector for using the detected output as a trigger signal of the sample hold circuit. 3. The receiving device according to claim 1, wherein the receiving device further includes an FM demodulator for performing FM demodulation on the output of the intermediate frequency correlator, the FM demodulator and the first frequency converter. And a second voltage-controlled oscillator for generating a local oscillation signal of the frequency converter, the receiving device being interposed between the second voltage controlled oscillator and the second voltage controlled oscillator. 4. The transmitting side receives a transmission signal transmitted by multiplexing a reference signal by time division multiplexing or spread spectrum multiplexing, and correlates the received reference signal with its own reference signal, What is claimed is: 1. A receiving device capable of shortening an initial acquisition time, expanding a frequency drift range that can be acquired, and operating at a low CN ratio, the receiving device including a receiving antenna and an output of the receiving antenna in an intermediate frequency band. A first frequency converter for performing frequency conversion into a signal, a reference signal generator having the same waveform as the reference signal, and generating a reference signal in the intermediate frequency band, the frequency converter output and the reference signal An intermediate frequency correlator that correlates with the generator output, an envelope detector that envelope-detects the intermediate frequency correlator output, and a differencer that takes a time-series difference for the envelope detector output, A receiving apparatus comprising at least a third voltage controlled oscillator controlled by the differencer output, and reproducing a synchronous output from the output side of the third voltage controlled oscillator. 5. The receiving apparatus according to claim 1, wherein the reference signal generator is supplied with a baseband reference signal generator and an output of the reference signal generator. To a reference signal in the intermediate frequency band and an intermediate frequency band modulator.