JP3717856B2 - Frequency measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a frequency measurement device, and more particularly to a frequency measurement device for a carrier wave of a signal modulated by an N-value PSK (Phase Shift Keying) method (where N is a positive integer).
[0002]
[Prior art]
Conventionally, frequency measurement for a carrier wave of a signal modulated by an N-value PSK method has been performed in principle using a frequency measurement device having a configuration shown in FIG. The frequency measurement apparatus 500 having the configuration shown in FIG. 5 includes a quadrature detector 510, first and second low-pass filters (hereinafter referred to as LPFs) 521 and 522, a phase error detector 530, and a loop filter 540. , A synchronization establishment detection unit 550, an adder 560, a frequency counter 570, and a display unit 580.
[0003]
Here, the quadrature detector 510 further includes a voltage controlled oscillator (hereinafter referred to as a VCO) 511, a 90-degree phase shifter 512, and first and second mixers 513 and 514.
The VCO 511 reproduces the 0 degree phase carrier signal and outputs it to the 90 degree phase shifter 512 and the first mixer 513.
The 90-degree phase shifter 512 changes the phase of the 0-degree phase carrier signal output from the VCO 511 by 90 degrees and outputs it to the second mixer 514.
[0004]
The first mixer 513 synchronously detects an input signal modulated by the N-value PSK method using the 0-degree phase reproduction carrier signal output from the VCO 511, and synchronizes the I-axis component on the orthogonal coordinates ( Hereinafter, it is referred to as an I component signal) and is output to the first LPF 521.
Similarly, the second mixer 514 synchronously detects an input signal modulated by the N-value PSK method using the regenerated carrier signal output from the 90-degree phase shifter 512 and phase-shifted by 90 degrees, A Q axis component synchronous detection signal (hereinafter referred to as a Q component signal) on Cartesian coordinates is generated and output to the second LPF 522.
[0005]
The I component signal output from the first mixer 513 and the Q component signal output from the second mixer 514 include a signal component having a frequency twice the carrier frequency and a modulation component.
The first LPF 521 operates to pass the modulation component included in the I component signal, and outputs the modulation component to the phase error detector 530 and the synchronization establishment detection unit 550. Similarly, the second LPF 522 operates to pass the modulation component included in the Q component signal, and outputs the modulation component to the phase error detector 530 and the synchronization establishment detection unit 550.
[0006]
The phase error detector 530 generates a signal related to the phase difference between the input signal and the reproduced carrier signal based on the modulation component output from the first LPF 521 and the modulation component output from the second LPF 522, The data is output to the loop filter 540 and the synchronization establishment detection unit 550.
The loop filter 540 averages the signal related to the phase difference and outputs the averaged signal to the adder 560.
[0007]
The synchronization establishment detection unit 550 detects whether the carrier wave is correctly reproduced based on the output from the first LPF 521, the output from the second LPF 522, and the output from the phase error detector 530. If not correctly reproduced, a sawtooth wave is output so that the frequency of the VCO 511 is swept around the carrier frequency. When synchronization establishment is detected, the output voltage at that time is held and stopped.
[0008]
The adder 560 is a means for adding the signal output from the loop filter 540 and the signal output from the synchronization establishment detection unit 550 and outputting the result to the VCO 511.
The VCO 511 generates a signal having a frequency corresponding to the signal output from the adder 560 and is used for the synchronous detection.
[0009]
[Problems to be solved by the invention]
However, the conventional method has a problem that the scale of the frequency measuring device increases because complicated signal processing is required to detect synchronization establishment for measuring the carrier frequency.
[0010]
The present invention has been made to solve such a problem, and an object of the present invention is to provide a frequency measuring apparatus that does not require detection of establishment of synchronization and can reduce the scale of the apparatus.
[0013]
[Means for Solving the Problems]
In view of the above points, the invention according to claim 1 is an apparatus for measuring a carrier frequency of an input signal modulated by an N-value PSK system in which a positive integer is N, and the frequency of the input signal is set to a predetermined frequency. Frequency conversion means for generating a low frequency component signal obtained by lowering, an N multiplier for multiplying the frequency of the low frequency component signal by N times to generate an N multiplied signal, and N times multiplied A band-pass filter for extracting the signal component of the carrier frequency from the N-multiplied signal, waveform shaping means for converting the signal component of the carrier frequency multiplied by N times into a rectangular wave signal, An N frequency divider for dividing the signal by 1 / N, a counter for integrating the number of rectangular waves in a predetermined time in the rectangular wave signal divided by 1 / N, and the low frequency signal Reduce to produce component signal It has a constant frequency, a configuration in which an adder for adding the number of the rectangular wave in predetermined been accumulated time by the counter.
[0014]
With this configuration, the N-value PSK modulation signal is multiplied by N by an N multiplier and limited to the signal band of the measurement band by a band pass filter, so that complicated signal processing is not required for detection of establishment of synchronization for measuring the carrier frequency. Thus, a frequency measuring device capable of reducing the device scale can be realized.
[0015]
According to a second aspect of the present invention, in the first aspect , the N multiplier has a configuration including one or more distributors and one or more multipliers.
With this configuration, since the N multiplier can be configured by a known simple means, it is possible to realize a frequency measuring device capable of reducing the device scale.
[0016]
According to a third aspect of the present invention, in the first aspect , the N multiplier has a configuration having a non-linear means including a non-linear amplifier or a non-linear element.
With this configuration, since the N multiplier can be configured by a known simple means, it is possible to realize a frequency measuring device capable of reducing the device scale.
[0017]
According to a fourth aspect of the present invention, in the first aspect of the present invention, the predetermined frequency that the frequency converting unit lowers to generate the low frequency component signal is variable in the first aspect, and the frequency measuring device further includes the predetermined frequency. A low-frequency power detecting means for determining a frequency to be lowered in order to generate the low-frequency component signal by detecting the power of the low-frequency component signal while changing the frequency-converting means; When the frequency is determined by the detection means, the predetermined frequency is fixed to the determined frequency, and the frequency measuring device has a configuration for measuring the carrier frequency at the fixed predetermined frequency.
[0018]
With this configuration, the frequency measuring device according to claim 1 further generates a low-frequency component signal by detecting the power of the low-frequency component signal while changing a predetermined frequency to be lowered to generate the low-frequency component signal. Since the low frequency power detecting means for determining the frequency to be reduced is provided, it is possible to measure the frequency without knowing the frequency of the signal to be measured, and to realize a frequency measuring device capable of reducing the device scale be able to.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing a block configuration of a frequency measuring apparatus according to the first embodiment of the present invention. In FIG. 1, a frequency measuring apparatus 100 includes a frequency conversion unit 110, an N multiplier 120, a band pass filter (hereinafter referred to as BPF) 130, a PLL (Phase Locked Loop) 140, a waveform shaping unit 150, N A frequency divider 160, a counter 170, an adder 180, and a display unit 190 are included.
[0020]
Here, the frequency measurement apparatus 100 receives an N-value PSK modulated signal (referred to as an N-value PSK modulation signal) and inputs the carrier frequency (hereinafter referred to as f _c ) of the inputted N-value PSK modulation signal. ) Is a device for displaying.
The frequency conversion means 110 is a means for reducing the frequency band of the input N-level PSK modulation signal, and is a local oscillator 111, a mixer 112, and a low-pass filter (hereinafter referred to as LPF). ) 113.
[0021]
The local oscillator 111 is an oscillator for generating an analog signal having a predetermined frequency and outputting the analog signal to the mixer 112 and the adder 180. For convenience of explanation, hereinafter, the frequency of the analog signal generated by the local oscillator 111 is assumed to be _fl . The frequency f _l of the analog signal output by the local oscillator 111 in order to allow adjustment, may be variable.
The mixer 112 is means for receiving the N-level PSK modulation signal and the analog signal output from the local oscillator 111 as input, multiplying them, and outputting the result to the LPF 113. For convenience of description, the frequency of the N-PSK modulation signal in the following to f _m.
[0022]
Mixer 112 a result of the multiplication by, from the mixer 112, the frequency (f _m -f _l) signal (hereinafter, referred to as low-frequency component signal.) And the signal of frequency (f _m + f _l) (hereinafter, the high frequency component signal Is output.
The LPF 113 is a means for receiving the low frequency component signal and the high frequency component signal output from the mixer 112, removing the high frequency component signal, and outputting the low frequency component signal to the N multiplier 120.
[0023]
The N multiplier 120 is a means for receiving the low frequency component signal output from the LPF 113, multiplying the frequency of the low frequency component signal by N, and outputting the N multiplied signal to the BPF 130.
Here, as shown in FIG. 2, the N multiplier 120 is configured by combining a frequency divider 121 and a multiplier 122. The N multiplier 120 is configured to reduce nonlinear distortion generated by nonlinear means such as a nonlinear amplifier and a nonlinear element. An N-multiplied signal may be extracted from the signal it has. FIG. 2A shows an example of a triple multiplier, and FIG. 2B shows an example of a quadruple multiplier.
[0024]
The BPF 130 is a means for receiving a signal obtained by multiplying the frequency of the low frequency component signal by N, extracting a signal in a predetermined frequency band from the input signal, and outputting the signal to the PLL 140. Here, the predetermined bandwidth, of the frequency band of the N multiplying signal refers to a center frequency band in the vicinity of a frequency N (f _m -f _l).
[0025]
The PLL 140 is a unit that receives the signal output from the BPF 130 as an input, generates an analog signal synchronized with the signal output from the BPF 130 (hereinafter referred to as an analog synchronization signal), and outputs the analog signal to the waveform shaping unit 150.
[0026]
As described above, the low frequency component signal is extracted by the LPF 113, the low frequency component signal is multiplied by N by the N multiplier 120, and the signal near the center frequency of the frequency N (f _m −f _l ) is multiplied from the signal multiplied by N by the BPF 130. A band signal is extracted and synchronized with a signal in the vicinity of the center frequency of the frequency N (f _m −f _l ) by the PLL 140, whereby the oscillation frequency of the local oscillator 111 and the carrier frequency f _c of the N-value PSK modulation signal are obtained. The information regarding the difference of can be obtained.
[0027]
The waveform shaping means 150 receives the synchronization signal output by the sound pressure fluctuation detection means 140 as an input, converts the analog synchronization signal into a digital signal by shaping the waveform into a rectangular wave, and outputs the digital signal to the N divider 160. Means.
The N divider 160 receives the digital signal output from the waveform shaping means 150, divides the digital signal by 1 / N, and outputs the digital signal obtained by the division to the counter 170. Means. As a result, the number of pulses per unit time in the digital signal becomes (f _c −f _l ).
[0028]
The counter 170 receives the frequency-divided digital signal output from the N frequency divider 160, counts the number of pulses within a predetermined time in the frequency-divided digital signal, and outputs a signal corresponding to the counted number of pulses. This is means for outputting to the adder 180. Here, the predetermined time may be, for example, 1 second, but may be other time.
[0029]
The adder 180 receives an analog signal output from the local oscillator 111 and a signal corresponding to the number of pulses output from the counter 170, and extracts frequency information of the analog signal output from the local oscillator 111. Obtained by adding the number of pulses (f _c −f ₁ ) obtained based on the signal corresponding to the number of pulses and the frequency f _{1 of the} analog signal obtained based on the frequency information of the analog signal. This is a means for generating a signal corresponding to the obtained value (hereinafter referred to as an added value) f _c and outputting it to the display means 190.
[0030]
Display means 190 receives as input a signal corresponding to the addition value f _c output by the adder 180 is a means for displaying the added value f _c. Here, the display unit 190 can be replaced by another output unit.
In the above description, the PLL 140 is configured to be synchronized with the signal output by the BPF 130. However, if synchronization is not required, the PLL 140 can be omitted.
[0031]
The frequency measurement apparatus according to the first embodiment of the present invention converts a high frequency band signal into a low frequency band signal (also referred to as down-conversion) from the viewpoint of hardware simplification. In the first place, in the case of a low frequency band signal, such processing for down-conversion is not necessary. When down-conversion is not performed, the frequency conversion unit 110 and the adder 180 in the frequency measurement apparatus 100 can be omitted.
[0032]
As described above, the frequency measurement apparatus 100 according to the first embodiment of the present invention multiplies an N-value PSK modulation signal by N by an N multiplier, and limits it to the signal band of the measurement band by a bandpass filter. Therefore, it is possible to realize a frequency measuring apparatus that does not require complicated signal processing to detect the establishment of synchronization for measuring the carrier frequency, and can reduce the scale of the apparatus.
[0033]
FIG. 3 is a diagram showing a block configuration of a frequency measurement device according to the second embodiment of the present invention. The frequency measurement apparatus 300 according to the second embodiment of the present invention is a frequency measurement apparatus that enables frequency measurement when the measurement frequency band cannot be specified. As shown in FIG. 3, the frequency measurement device 300 has a configuration in which a low-frequency power detection unit 314 is added to the frequency measurement device 100 according to the first embodiment of the present invention.
[0034]
Of the constituent means constituting the frequency measuring apparatus 300 of the second embodiment of the present invention, the same processing as the constituent means of the frequency measuring apparatus 100 of the first embodiment of the present invention is performed. Are given the same reference numbers and their explanation is omitted.
Prior to describing the configuration means of the frequency measurement device 300, the principle of frequency measurement performed by the frequency measurement device 300 will be described.
[0035]
The N-value PSK modulated signal input to the frequency measuring device 300 has a frequency spectrum as shown in FIG. Further, the analog signal generated by the local oscillator 311 has a frequency spectrum as shown in FIG. When the mixer 112 multiplies the N-value PSK modulated signal having the spectrum shown in FIG. 4A and the analog signal having the frequency spectrum shown in FIG. 4B, the sum of the local oscillation frequencies (−f ₁ ) is calculated. component (-f _l ± f _c), sum and difference components of the local oscillator frequency _{(+ f l) (+ f} l ± f c) is generated. This situation is shown in FIG.
[0036]
Here, when the frequency of the analog signal oscillated by the local oscillator 311 is increased from 0 Hz, the frequency of the signal of the two difference components of the local oscillation frequency (hereinafter referred to as the difference component frequency) (−f _l + f _c ) , (−f ₁ −f _c ) approaches the frequency of 0 Hz (see FIG. 4D). If it can be detected that the difference component frequency has entered the frequency band of the LPF 113, the frequency can be measured using the means described in the first embodiment of the present invention.
[0037]
The low frequency power detection means 314 constituting the frequency measurement device 300 according to the second embodiment of the present invention is a means having such a function. This will be described below.
In the present embodiment, the local oscillator 311 is an oscillator for generating an analog signal having a predetermined frequency and outputting it to the mixer 112 and the adder 180. The frequency of the analog signal output by the local oscillator 111 may be variable. In the second embodiment of the present invention, the frequency of the analog signal output after the start of measurement is increased from around 0 Hz at a constant speed. When a control signal (to be described later) is received from the low frequency power detection means 314, the frequency is fixed at the time of receiving the control signal.
[0038]
The low frequency power detection means 314 receives the sum / difference component signal output from the mixer 112 as input, detects the power of the signal that falls within a predetermined frequency band of the input sum / difference component signal, and is detected. This is a means for outputting a predetermined control signal of the local oscillator 311 when the increase per unit time of the electric power becomes equal to or lower than a predetermined value after being increased above a predetermined value.
[0039]
Here, the frequency band of the predetermined width is a frequency band having a frequency band equal to or higher than the frequency band including the difference component frequency and not including the frequency band of the sum component signal. That is, when the difference component frequency band is in the vicinity of 0 Hz, it has a frequency band in which only the difference component signal can be detected. As the frequency band having the predetermined width, for example, the frequency band of the LPF 113 can be taken.
[0040]
By fixing the oscillation frequency of the local oscillator 111 as described above, the LPF 113 can selectively output only the difference component signal to the N multiplier 120 after the oscillation frequency of the local oscillator 111 is fixed. The frequency can be measured as described in the first embodiment of the present invention.
[0041]
As described above, the frequency measuring device according to the second embodiment of the present invention further changes the oscillation frequency of the local oscillator to the frequency measuring device according to the first embodiment of the present invention, thereby reducing the low frequency range. Since the power detection means detects that the frequency of the signal to be measured has entered the frequency band of the LPF, and a means for fixing the oscillation frequency of the local oscillator to the frequency at which the local oscillator has been detected, a signal to be measured is added. Therefore, it is possible to realize a frequency measuring apparatus that can measure the frequency without knowing the frequency of the apparatus and can reduce the scale of the apparatus.
[0042]
【The invention's effect】
As described above, the present invention can realize a frequency measurement device that does not require detection of establishment of synchronization and can reduce the device scale.
[Brief description of the drawings]
FIG. 1 is a diagram showing a block configuration of a frequency measurement device according to a first embodiment of the present invention.
FIG. 2 is a block configuration diagram showing a specific example of an N multiplier in the frequency measurement device according to the first embodiment of the present invention.
FIG. 3 is a diagram showing a block configuration of a frequency measurement device according to a second embodiment of the present invention.
FIG. 4 is a diagram for explaining an operation principle of a frequency measurement device according to a second embodiment of the present invention.
FIG. 5 is a diagram showing a block configuration of a conventional frequency measurement device.
[Explanation of symbols]
100, 300, 500 Frequency measuring device 110, 310 Frequency conversion means 111, 311 Local oscillator 112 Mixer 113 Low pass filter 120 N multiplier 121 N frequency divider 122 Multiplier 130 Band pass filter 140 PLL
150 Waveform shaping means 160 N frequency divider 170 Counter 180 Adder 190 Display means 314 Low frequency power detection means 510 Quadrature detector 511 Voltage controlled oscillator (VCO)
512 90 degree phase shifter 513 1st mixer 514 2nd mixer 521 1st LPF
522 Second LPF
530 Phase error detector 540 Loop filter 550 Synchronization establishment detection unit 560 Adder 570 Frequency counter 580 Display unit

Claims (4)

Frequency conversion for generating a low-frequency component signal obtained by reducing the frequency of an input signal by a predetermined frequency in an apparatus for measuring a carrier frequency of an input signal modulated by an N-value PSK method with a positive integer N Means for multiplying the frequency of the low frequency component signal by N times to generate an N multiplied signal, and for extracting the signal component of the carrier frequency multiplied by N times from the N multiplied signal. A band-pass filter, waveform shaping means for converting the signal component of the carrier frequency multiplied by N times into a rectangular wave signal, and an N divider for dividing the rectangular wave signal by 1 / N A counter that accumulates the number of rectangular waves within a predetermined time in the rectangular wave signal divided by 1 / N, a predetermined frequency that is decreased when generating the low-frequency component signal, and the counter Integrated Frequency measuring apparatus characterized by comprising an adder for adding the number of square wave within a predetermined time. 2. The frequency measuring apparatus according to claim 1, wherein the N multiplier includes one or more distributors and one or more multipliers. The frequency measuring apparatus according to claim 1, wherein the N multiplier includes a nonlinear means including a nonlinear amplifier or a nonlinear element. The predetermined frequency to be lowered by the frequency converting means to generate the low frequency component signal is variable, and the frequency measuring device further detects the power of the low frequency component signal while changing the predetermined frequency. A low-frequency power detecting means for determining a frequency to be lowered to generate a low-frequency component signal, wherein the frequency converting means is determined when the frequency is determined by the low-frequency power detecting means; 2. The frequency measuring apparatus according to claim 1, wherein the predetermined frequency is fixed to a frequency, and the frequency measuring apparatus measures a carrier frequency at the fixed predetermined frequency.

Images