JP4156183B2 - Angle demodulation apparatus, angle demodulation method, and recording medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an angle demodulation device and an angle demodulation method.
[0002]
[Prior art]
  Direct conversion is known as a technique for demodulating an FM (Frequency Modulation) modulation signal. An FM receiver using the direct conversion method has a configuration shown in FIG. 3, for example.
[0003]
  In the FM receiver shown in FIG. 3, the FM modulated signal received by the antenna 201 and amplified by the RF (Radio Frequency) amplifier 202 is supplied to the first mixers 204I and 204Q by the duplexer 203. . The FM modulated signal is mixed with a pair of first local oscillation signals having a phase difference of 90 degrees generated by the first local oscillator 214 and the phase shifter 208, and converted into a pair of baseband signals. The first local oscillation signal is set to the same frequency as the carrier frequency of the received signal.
[0004]
  The baseband signal has its harmonic components cut by LPF (Low Pass Filter) 205I and 205Q, amplified by AF (Audio Frequency) amplifiers 206I and 206Q, and then secondly mixed by second mixers 207I and 207Q. The local oscillator 215 and the phase shifter 209 are mixed with a pair of second local oscillation signals that are 90 degrees out of phase with each other. Signals obtained by mixing are added to each other by an adder 210, and thereby converted into a single intermediate frequency signal.
[0005]
  The intermediate frequency signal is supplied to an FM detector 213 via a BPF (Band Pass Filter) 211 and an IF (Intermediate Frequency) amplifier 212, and the FM detector 213 detects the intermediate frequency signal and is obtained by detection. Output an audio signal.
[0006]
  According to the direct conversion method, the configuration of an apparatus for demodulating an FM modulated signal can be simplified, and unlike superheterodyne, there is an advantage that there is no possibility of interference by a signal near the image frequency.
[0007]
[Problems to be solved by the invention]
  However, in the FM receiver having the above-described configuration shown in FIG. 3, when the second-order distortion of the interference wave or the second-order distortion of the first local oscillation signal occurs in the first mixer, these second-order distortions are generated. DC components included in the baseband signal. When the DC component mixed in the baseband signal is removed using an HPF (High Pass Filter), the FM modulated signal converted into the baseband signalmainSince the component is also removed, the FM modulated signal is not accurately demodulated.
[0008]
  As a technique for removing this DC component without impairing the accuracy of demodulation of the FM modulated signal, for example, the technique of US Pat. No. 4,944,025 is conceivable.
  The method of US Pat. No. 4,944,025 performs AFC (Automatic Frequency Control) for the first local oscillator using a voltage obtained by adding an offset voltage to a voltage obtained by detecting an intermediate frequency signal. Thus, the frequency of the first local oscillation signal is adjusted. By this method, the frequency of the first local oscillation signal can be set to a frequency that is offset by a predetermined amount from the carrier frequency of the FM modulation signal to be received. Therefore, it becomes possible to easily remove the direct current component from the baseband signal using HPF without losing accuracy.
[0009]
  However, according to this method, it is difficult to adjust a circuit for adding an offset voltage, and there is a problem that an amount of frequency offset becomes unstable. In addition, since the first and second local oscillators that generate signals of different frequencies independently from each other are used, the operation of the FM receiver is likely to be unstable, and the configuration of the FM receiver is complicated or large. As a result, higher prices were also invited.
[0010]
  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an angle demodulating device and an angle demodulating method which are easy to adjust with a simple configuration and perform a direct conversion method.
  Another object of the present invention is to provide an angle demodulating device and an angle demodulating method for generating a local oscillation signal based on a single reference oscillation signal and performing a direct conversion method.
[0011]
[Means for Solving the Problems]
  In order to achieve the above object, an angle demodulator according to a first aspect of the present invention provides:
  A first local oscillation signal and the first local oscillation signal;And 9A first oscillating unit that generates a first phase-shifted signal having a phase difference of 0 degrees;
  CornerThe angle modulation signal is input, the first local oscillation signal and the first phase shift signal are input from the first oscillation unit, and the angle modulation signal is input.AndThe first local oscillation signalAndFrequency out of productIs 0A first baseband signal composed of components excluding the componentAndThe first phase shift signalAndFrequency out of productIs 0A first mixing unit for generating a second baseband signal composed of components excluding the component
  Second local oscillation signal and the second local oscillation signalAnd 9A second oscillating unit that generates a second phase-shifted signal having a phase difference of 0 degrees;
  The first baseband signal is input from the first mixing unit, the second local oscillation signal and the second phase shift signal are input from the second oscillation unit, and the first baseband signal is input.AndThe second local oscillation signalAndAnd the second baseband signalAndSecond phase shift signalAndA second mixing unit for generating an intermediate frequency signal representing the sum or difference of the products of:
  A demodulator that generates an angle demodulated signal by inputting and demodulating the intermediate frequency signal from the second mixing unit;
  The second oscillation unit includes:
  A reference oscillator for generating a reference oscillation signal;
  By dividing the reference oscillation signal by a predetermined first dividing ratio, a difference or sum between a predetermined intermediate frequency and an offset frequency within a predetermined range is obtained.Etc.A frequency divider for generating the second local oscillation signal having a new frequency,
  The first oscillating unit receives the reference oscillation signal and generates a signal that converges to a frequency having a certain ratio to the frequency of the input reference oscillation signal, thereby generating the angle modulation signal.AroundSum or difference of wave number and offset frequencyEtc.A variable frequency oscillator for generating the first local oscillation signal having a new frequency,
  It is characterized by that.
[0012]
[0013]
  The reference oscillator receives the intermediate frequency signal and generates a signal that converges to a frequency having a certain ratio with respect to the carrier frequency of the input intermediate frequency signal, so that the frequency of the second local oscillation signal is A frequency control unit that generates the reference oscillation signal having a frequency multiplied by the value of the first frequency division ratio may be provided.Yes.
[0014]
  The frequency control unit may be, for example, an input intermediate frequency signal.AndThe frequency of the reference oscillation signal is based on a phase difference from a signal obtained by dividing the reference oscillation signal by a predetermined second frequency division ratio.Intermediate frequency signalA frequency of the reference oscillation signal is determined so as to converge to a value having a certain ratio with respect to a frequency of the first frequency, and the reference oscillation signal having the determined frequency is generated.of Phase Lock Loop SystemBy providing the control unit, the frequency of the reference oscillation signal may be converged to a value obtained by multiplying the sum of the intermediate frequency and the offset frequency by the first frequency division ratio.
[0015]
  The variable frequency oscillator, for example, divides a signal obtained by dividing the input reference oscillation signal by a predetermined third division ratio and the first local oscillation signal by a predetermined fourth division ratio. Based on the phase difference from the signal obtained in this manner, the frequency of the first local oscillation signal converges to a value having a certain ratio with respect to the frequency of the reference oscillation signal. Determining a frequency and generating a first local oscillation signal having the determined frequency;of Phase Lock Loop SystemBy providing the control unit, the frequency of the first local oscillation signal is changed to an angle modulated signal.AroundWhat is necessary is just to make it converge to the sum of a wave number and an offset frequency.
[0016]
  The magnitude of the offset frequency is preferably within 300 Hz.Yes.
[0017]
  An angle demodulation method according to the second aspect of the present invention is as follows:
  A first local oscillation signal and the first local oscillation signal;And 9Generating a first phase-shifted signal having a phase difference of 0 degrees;
  CornerThe angle modulation signal is input and the angle modulation signal is input.AndThe first local oscillation signalAndFrequency out of productIs 0A first baseband signal composed of components excluding the componentAndThe first phase shift signalAndFrequency out of productIs 0Generating a second baseband signal composed of components excluding the component
  Second local oscillation signal and the second local oscillation signalAnd 9Generating a second phase-shifted signal with a phase difference of 0 degrees,
  The first baseband signalAndThe second local oscillation signalAndAnd the second baseband signalAndSecond phase shift signalAndGenerate an intermediate frequency signal representing the sum or difference of the products of
  An angle demodulation method for generating an angle demodulated signal by detecting the intermediate frequency signal,
  The second local oscillation signal is a difference or sum of a predetermined intermediate frequency and an offset frequency within a predetermined range.Etc.Having a new frequency and generated by dividing the reference oscillation signal by a predetermined first division ratio,
  The first local oscillation signal is the angle modulation signal.AroundSum or difference of wave number and offset frequencyEtc.Generated by generating a signal that converges to a frequency having a certain ratio to the frequency of the reference oscillation signal.
  It is characterized by that.
[0018]
[0019]
  A computer-readable recording medium according to the third aspect of the present invention is
  Computer
  A first local oscillation signal and the first local oscillation signal;And 9A first oscillating unit that generates a first phase-shifted signal having a phase difference of 0 degrees;
  CornerThe angle modulation signal is input, the first local oscillation signal and the first phase shift signal are input from the first oscillation unit, and the angle modulation signal is input.AndThe first local oscillation signalAndFrequency out of productIs 0A first baseband signal composed of components excluding the componentAndThe first phase shift signalAndA first mixing unit that generates a second baseband signal composed of components excluding components having a frequency of 0 in the product of
  Second local oscillation signal and the second local oscillation signalAnd 9A second oscillating unit that generates a second phase-shifted signal having a phase difference of 0 degrees;
  The first baseband signal is input from the first mixing unit, the second local oscillation signal and the second phase shift signal are input from the second oscillation unit, and the first baseband signal is input.AndThe second local oscillation signalAndAnd the second baseband signalAndSecond phase shift signalAndA second mixing unit for generating an intermediate frequency signal representing the sum or difference of the products of:
  Function as a demodulator that generates an angle demodulated signal by demodulating the intermediate frequency signal from the second mixing unit;
  The second oscillation unit is
  A reference oscillator for generating a reference oscillation signal;
  By dividing the reference oscillation signal by a predetermined first dividing ratio, a difference or sum between a predetermined intermediate frequency and an offset frequency within a predetermined range is obtained.Etc.Function as a frequency divider to generate the second local oscillation signal having a correct frequency;
  The first oscillating unit receives the reference oscillation signal and generates a signal that converges to a frequency having a certain ratio with respect to the frequency of the input reference oscillation signal.AroundSum or difference of wave number and offset frequencyEtc.Functioning as a variable frequency oscillator that generates the first local oscillation signal having a new frequency;
  The program for recording is recorded.
[0020]
[0021]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, an angle demodulating apparatus and an angle demodulating method according to an embodiment of the present invention will be described using an FM (Frequency Modulation) receiver as an example.
[0022]
  FIG. 1 shows an example of the configuration of an FM receiver according to an embodiment of the present invention.
  As shown in the figure, this FM receiver includes an antenna 1, an RF (Radio Frequency) amplifier 2, a duplexer 3, mixers 4I, 4Q, 8I and 8Q, and an LPF (Low Pass Filter) 5I. And 5Q, AF (Audio Frequency) amplifiers 6I and 6Q, DC removing units 7I and 7Q, phase shifters 9 and 10, a local oscillator 11, an adder 12, and a BPF (Band Pass Filter). 13, an IF (Intermediate Frequency) amplifier 14, and an FM detector 15.
[0023]
  When a signal (RF signal) excited by the electromagnetic wave from the antenna 1 is supplied from the antenna 1, the RF amplifier 2 amplifies the signal supplied from the antenna 1 and supplies the amplified signal to the duplexer 3.
  The duplexer 3 supplies the RF signal supplied from the RF amplifier 2 to the mixers 4I and 4Q.
[0024]
  The mixers 4I and 4Q have substantially the same configuration. The mixer 4I generates a signal (I channel baseband signal) representing the product of an RF signal supplied from the duplexer 3 and a first local oscillation signal (described later) supplied from the local oscillator 11, and supplies it to the LPF 5I. Supply. The mixer 4Q generates a signal (Q channel baseband signal) representing a product of an RF signal supplied from the duplexer 3 and a first phase shift signal (described later) supplied from the phase shifter 9, and supplies the signal to the LPF 5Q. Supply.
[0025]
  The LPFs 5I and 5Q have substantially the same configuration. The LPFs 5I and 5Q filter the I channel baseband signal or the Q channel baseband signal supplied from the mixer 4I or 4Q. Specifically, the LPF 5I removes a frequency component that exceeds an upper limit of an AF signal band to be reproduced from the I channel baseband signal, and supplies the remaining frequency component to the AF amplifier 6I. The LPF 5Q removes the frequency component exceeding the upper limit of the band of the AF signal to be reproduced from the Q channel baseband signal and supplies the remaining frequency component to the AF amplifier 6Q.
[0026]
  The AF amplifiers 6I and 6Q have substantially the same configuration. The AF amplifier 6I amplifies the signal supplied from the LPF 5I and supplies it to the DC removal unit 7I. The AF amplifier 6Q amplifies the signal supplied from the LPF 5Q and supplies it to the DC removal unit 7Q.
[0027]
  The direct current removing units 7I and 7Q have substantially the same configuration, and for example, both are configured by a capacitor or HPF (High Pass Filter). The DC removing unit 7I removes a DC component from the signal supplied from the AF amplifier 6I and supplies the other components to the mixer 8I. The DC removing unit 7Q removes a DC component from the signal supplied from the AF amplifier 6Q, and supplies the other components to the mixer 8Q.
[0028]
  The mixers 8I and 8Q have substantially the same configuration. The mixer 8I has a frequency representing the product of a signal supplied from the direct current removing unit 7I and a second local oscillation signal (described later) supplied from the local oscillator 11, and the frequency is the sum of the frequencies of these two signals (or A signal representing a component substantially equal to (difference) is generated and supplied to the adder 12. The mixer 8Q has a frequency that is the sum of the frequencies of these two signals (or the signal representing the product of a signal supplied from the DC removal unit 7Q and a second phase-shifted signal supplied from the phase shifter 10). A signal representing a component substantially equal to (difference) is generated and supplied to the adder 12.
[0029]
  When the phase shifter 9 is supplied with the first local oscillation signal from the local oscillator 11, the phase shifter 9 generates a first phase shift signal that is a signal obtained by substantially delaying the phase of the first local oscillation signal by 90 degrees, Supply to mixer 4Q.
  When the phase shifter 10 is supplied with the second local oscillation signal from the local oscillator 11, the phase shifter 10 generates a second phase shift signal that is a signal obtained by substantially delaying the phase of the second local oscillation signal by 90 degrees. Supply to mixer 8Q.
[0030]
  The adder 12 generates a signal representing the sum of the signals supplied from the mixers 8I and 8Q and supplies the signal to the BPF 13.
  The BPF 13 filters the signal supplied from the adder 12. Specifically, the BPF 13 supplies the band component in the vicinity of a predetermined intermediate frequency to the IF amplifier 14 in the signal supplied from the adder 12 and substantially blocks the other components.
  The IF amplifier 14 amplifies the component (IF signal) supplied from the BPF 13 and supplies the amplified component to the FM detector 15 and the local oscillator 11.
[0031]
  The FM detector 15 includes a ratio detector, a quadrature demodulator circuit, other arbitrary FM detector circuits, an AF amplifier, a speaker, and the like, and converts the frequency shift of the signal supplied from the IF amplifier 14 into an amplitude. The FM signal is demodulated by IF, and the AF signal obtained by the demodulation is output as an output signal of the FM receiver and reproduced.
[0032]
  As shown in FIG. 2, the local oscillator 11 includes VCOs (Voltage Controlled Oscillators) 101 and 111, frequency dividers 102, 105, 106, 107, and 112, phase comparators 103 and 108, LPFs 104 and 109, A loop filter 110 is included.
[0033]
  The VCOs 101 and 111 generate an AC signal, and change the frequency of the AC signal generated by the VCO 101 and 111 by a change specified by the control signal supplied to the VCO. Note that both the VCOs 101 and 111 generate, for example, an AC signal having a free running frequency unique to itself when the control signal is not yet supplied to the VCO 101 and 111.
  The VCO 101 supplies the AC signal (reference oscillation signal) generated by itself to the frequency dividers 102, 105, and 107. The VCO 111 supplies the AC signal generated by itself to the frequency divider 112, and supplies this AC signal to the mixer 4I and the phase shifter 9 as a first local oscillation signal.
[0034]
  Each of the frequency dividers 102, 105, 106, 107, and 112 includes, for example, a flip-flop circuit and a counter circuit.
[0035]
  The frequency divider 102 divides the AC signal supplied from the VCO 101 by a frequency division ratio p (where p is a natural number) (that is, the frequency divider 102 synchronizes with the reference oscillation signal and the frequency of the reference oscillation signal). To generate an AC signal having a frequency substantially equal to 1 / p.
  Then, the frequency divider 102 supplies a signal obtained by frequency division by itself to the phase comparator 103.
[0036]
  The frequency divider 105 divides the AC signal supplied from the VCO 101 by a frequency division ratio q (where q is a natural number), and supplies the signal obtained by frequency division to the frequency divider 106.
  The frequency divider 106 divides the AC signal supplied from the frequency divider 105 by a frequency division ratio r (where r is a natural number), and the signal obtained by frequency division by itself is second local part. The oscillation signal is supplied to the mixer 8I and the phase shifter 10.
[0037]
  The frequency divider 107 divides the AC signal supplied from the VCO 101 by a frequency division ratio s (where s is a natural number), and supplies the signal obtained by frequency division to the phase comparator 108.
  The frequency divider 112 divides the AC signal supplied from the VCO 111 by a frequency division ratio t (where t is a natural number) and supplies the signal obtained by frequency division to the phase comparator 108. .
[0038]
  The phase comparator 103 isFor example,Multiplication timesRoad (mixer) etc.Composed ofA mixer-type analog phase comparator, etc.The control signal representing the phase difference between the AC signal supplied from the frequency divider 102 and the signal supplied from the IF amplifier 14 is generated, and the generated control signal is supplied to the LPF 104.
  The LPF 104 is included in the control signal supplied from the phase comparator 103.UnnecessaryThe control signal from which the component is removed and the harmonic component is substantially removed is supplied to the VCO 101.
[0039]
  The control signal output from the phase comparator 103 is a signal supplied from the IF amplifier 14.AndWhen the phase difference from the signal supplied from the frequency divider 102 is substantially zero, the change in frequency of the reference oscillation signal is designated as substantially zero (that is, the VCO 101 is actually generated) To keep the frequency of the AC signal that is present).
[0040]
  On the other hand, the signal supplied from the IF amplifier 14OfThe change indicated by the control signal output from the phase comparator 103 when the phase is ahead of the phase of the signal supplied from the frequency divider 102 is a positive value. That is, it is specified to increase the frequency of the reference oscillation signal. The signal supplied from the IF amplifier 14OfThe change indicated by the control signal output from the phase comparator 103 when the phase is behind the phase of the signal supplied from the frequency divider 102 is a negative value. That is, it is designated to decrease the frequency of the reference oscillation signal. However, the absolute value of the change specified by the control signal is the signal supplied from the IF amplifier 14 regardless of whether the value of the change is positive or negative.AndThe larger the phase difference from the signal supplied from the frequency divider 102, the larger the value.
  That is, the VCO 101, the frequency divider 102, the phase comparator 103, and the LPF 104 are the first to control the frequency of the reference oscillation signal.of Phase Lock Loop(PLL).
[0041]
  The phase comparator 108 is configured by a multiplication circuit or the like, generates a signal representing the phase difference between the two AC signals supplied from the frequency dividers 107 and 112 as a duty ratio of a rectangular wave, and generates the generated control signal. Supply to LPF109.
  The LPF 109 removes the harmonic component contained in the signal supplied from the phase comparator 108 and supplies the signal from which the harmonic component is substantially removed to the loop filter 110.
  The loop filter 110 is configured by an integration circuit or the like, generates a control signal having a level representing the duty ratio of the signal supplied from the LPF 109, and supplies the generated control signal to the VCO 111.
[0042]
  When the phase difference between the two signals supplied from the frequency dividers 107 and 112 is substantially zero, the signal output from the phase comparator 108 is a change in the frequency of the AC signal generated by the VCO 111 from the loop filter 110. A control signal designating the minute as substantially 0 is output.
[0043]
  On the other hand, the signal supplied from the frequency divider 112Place ofThe signal output from the phase comparator 108 when the phase is ahead of the phase of the signal supplied from the frequency divider 107 is such that the change indicated by the control signal output from the loop filter 110 has a negative value. It will be a thing. In addition, the signal supplied from the frequency divider 112 isOfThe signal output from the phase comparator 108 when the phase is delayed from the phase of the signal supplied from the frequency divider 107 is such that the change indicated by the control signal output from the loop filter 110 has a positive value. It will be a thing. However, regardless of whether the value of the change is positive or negative, the absolute value of the change specified by the control signal output from the loop filter 110 has a large phase difference between the two signals supplied from the frequency dividers 107 and 112. Make the value as large as possible.
  That is, the VCO 111, the frequency divider 107, the phase comparator 108, the LPF 109, and the loop filter 110 function as a second PLL that controls the frequency of the AC signal generated by the VCO 111.
[0044]
  Note that the values of the above-described frequency division ratios p, q, r, s, and t are:
(1) The frequency of the first local oscillation signal is converged to the sum (or difference) of the carrier frequency of the FM modulation signal to be received by the FM receiver and a predetermined offset frequency by the operation described later.
(2) The frequency of the second local oscillation signal converges to a difference (or sum) between a predetermined intermediate frequency and an offset frequency within the pass band of the BPF 13 by an operation described later,
(3) The frequency of the AC signal supplied from the frequency divider 102 to the phase comparator 103 converges to the above-described intermediate frequency by the operation described later.
  It is set to such a value.
[0045]
  And further
(4) The magnitude of the offset frequency is within 300 hertz,
  It is desirable. When the AF signal to be reproduced represents sound, the accuracy of the reproduced sound is not impaired even if a component of about 300 Hz or less is not reproduced. Therefore, in this case, the DC removal units 7I and 7Q that remove the DC component from the I channel baseband signal and the Q channel baseband signal do not remove only the DC component accurately, but only the components substantially below the offset frequency. Can be used without removing the accuracy of demodulation, and without the loss of I-channel baseband signals or Q-channel baseband signals.mainThe DC component of the second order distortion generated by the mixers 4I and 4Q can be removed without removing the component by mistake.
[0046]
  In other words, the values of the division ratios p, q, r, s, and t indicate the carrier frequency of the FM modulated signal to be received by this FM receiver as f.₀, The value at which the frequency of the first local oscillation signal converges is f₁, The value at which the frequency of the second local oscillation signal converges is f₂, The intermediate frequency is f_IFWhen the offset frequency is Δf, it is set to a value that substantially satisfies the relationship shown in Equations 1 to 3. Further, it is desirable that the relationship satisfying Equation 4 is satisfied.
[0047]
[Expression 1]
f₁= F₀± Δf
[Expression 2]
(F₁/ T) = f₂・ {(Q ・ r) / s}
[Equation 3]
f₂{(Q · r) / p} = (f₂± Δf) = f_IF
[Expression 4]
Δf ≦ 300 [Hz]
[0048]
  Specifically, for example, when the carrier frequency of the FM modulation signal to be received by this FM receiver is 470 MHz, the offset frequency is 72 Hz, and the intermediate frequency is 36.072149 kHz, the division ratio p, If the values of q, r, s, and t are 499, 250, 2, 360, and 37600 in this order, the relationships shown in Equations 1 to 4 are substantially satisfied.
  At this time, the frequency of the first local oscillation signal converges to about 470.000072 megahertz, the frequency of the second local oscillation signal converges to about 36.0000055 kilohertz, and the frequency divider 102 supplies the phase comparator 103. The frequency of the alternating current signal converges to about 36.072149 kilohertz.
[0049]
(Operation)
  Next, the operation of this FM receiver will be described.
  When the FM modulation signal to be received by the FM receiver induces an RF signal in the antenna 1, the RF amplifier 2 amplifies the RF signal and supplies the RF signal to the duplexer 3. The RF signal supplied from is supplied to the mixers 4I and 4Q.
  On the other hand, the mixer 4I is supplied with the first local oscillation signal generated by the VCO 111 of the local oscillator 11, and the mixer 4Q is a signal corresponding to a phase delayed substantially 90 degrees from the first local oscillation signal. A certain first phase shift signal is supplied from the phase shifter 9.
[0050]
  The frequency of the AC signal output from the VCO 111 is the frequency of the signal output from the frequency divider 107 (that is, 1 / s of the frequency of the reference oscillation signal), and the frequency of the signal output from the frequency divider 112 (that is, the VCO 111). It rises when it is higher than 1 / t of the frequency of the AC signal that it is actually generating, and falls when it is lower. Therefore, the frequency of the first local oscillation signal converges to a value t that is s minutes of the frequency of the AC signal output from the VCO 101.
[0051]
  The mixer 4I generates an I channel baseband signal. The I-channel baseband signal generated by the mixer 4I is filtered by the LPF 5I, amplified by the AF amplifier 6I, further subjected to DC component removal by the DC removal unit 7I, and then supplied to the mixer 8I.
  The mixer 4Q generates a Q channel baseband signal. The Q-channel baseband signal generated by the mixer 4Q is filtered by the LPF 5Q, amplified by the AF amplifier 6Q, further removed from the DC component by the DC removal unit 7Q, and then supplied to the mixer 8Q.
  FM modulation signal included in I channel baseband signal and Q channel baseband signalAroundThe wave number converges to a value substantially equal to the offset frequency.
[0052]
  On the other hand, the second local oscillation signal output from the frequency divider 106 of the local oscillator 11 is supplied to the mixer 8I, and the mixer 8Q corresponds to the phase of the second local oscillation signal substantially delayed by 90 degrees. A second phase shift signal that is a signal to be transmitted is supplied from the phase shifter 10.
[0053]
  The mixer 8I represents a component whose frequency is substantially equal to the sum (or difference) of the frequencies of these two signals, among the signals representing the product of the signal supplied from the direct current removing unit 7I and the second local oscillation signal. A signal is generated and supplied to the adder 12. The second local oscillation signal is obtained by dividing the reference oscillation signal by the frequency divider 105 by the frequency division ratio q and further by the frequency divider 106 by the frequency division ratio r.
  The mixer 8Q is a signal representing a component whose frequency is substantially equal to the sum (or difference) of the frequencies of the two signals out of the signal representing the product of the signal supplied from the DC removing unit 7Q and the second phase-shifted signal. Is supplied to the adder 12.
[0054]
  The adder 12 generates a signal that represents the sum of the signals supplied from the mixers 8I and 8Q. This signal is filtered by the BPF 13 to become an IF signal, and the IF signal is amplified by the IF amplifier 14.
  The IF signal amplified by the IF amplifier 14 is FM demodulated by the FM detector 15, and the AF signal obtained by the demodulation is output as an output signal of the FM receiver and reproduced.
[0055]
  On the other hand, the signal amplified by the IF amplifier 14 is also supplied to the phase comparator 103 of the local oscillator 11.
  The control signal output from the phase comparator 103 decreases the frequency of the reference oscillation signal when the frequency of the signal output from the frequency divider 102 (that is, 1 / p of the frequency of the reference oscillation signal) is higher than the intermediate frequency. To be When the frequency is lower than the intermediate frequency, the frequency of the reference oscillation signal is increased. Therefore, the frequency of the AC signal output from the VCO 101 converges to a value that is p times the intermediate frequency. The frequency of the second local oscillation signal converges to a value of 1 / (q · r) of the difference between the intermediate frequency and the offset frequency.
  And the FM modulation signal included in the IF signalAroundThe wave number converges to a value substantially equal to the sum (or difference) of the frequency of the second local oscillation signal and the offset frequency.
[0056]
  As a result of the operation described above, the FM modulated signal received by the FM receiver is demodulated, and the sound represented by the AF signal is reproduced.
  This FM receiver demodulates an FM modulated signal by a direct conversion method. The first and second local oscillation signals are both generated based on a single reference oscillation signal. Therefore, the configuration is simple. Further, the frequency of the reference oscillation signal converges to a value p times the intermediate frequency. Therefore, adjustment is also easy.
[0057]
  Note that the configuration of the FM receiver is not limited to that described above.
  For example, the duplexer 3 may include an A / D (Analog-to-Digital) converter, a DSP (Digital Signal Processor), and a CPU (Central Processing Unit). Further, the FM detector 15 may be composed of a DSP or CPU and a D / A (Digital-to-Analog) converter. And a part or all of the function of the other component of this FM receiver may be performed by DSP or CPU.
[0058]
  Further, the FM receiver does not need to acquire the FM modulated signal from the antenna 1, and may acquire the FM modulated signal from a wired line, for example. Further, the RF amplifier 2 can be omitted.
  The FM receiver may demodulate a PM (Phase Modulation) modulation signal. In this case, the FM detector 15 may include, for example, an integration circuit for integrating the AF signal obtained by FM demodulation of the IF signal.
[0059]
  Further, the values of the frequency division ratios p, q, r, s, and t are arbitrary as long as the above-described relationship is satisfied. Therefore, at least one of the frequency dividers 102, 105, 106, 107, and 112 may be such that the frequency division ratio can be changed. For example, if the frequency division ratio of the frequency divider 112 is variable, the FM receiver can change the carrier frequency of the FM modulation signal to be received.
[0060]
  Although the angle demodulating device and the angle demodulating method according to the present invention have been described above, the angle demodulating device according to the present invention can be realized by using a normal computer system without using a dedicated system. For example, by installing the program from a medium (floppy disk, CD-ROM, etc.) storing a program for executing the above-described operation in a personal computer equipped with an A / D converter and D / A converter, An FM receiver that executes the above-described processing can be configured.
[0061]
  Further, for example, the program may be posted on a bulletin board (BBS) of a communication network and distributed via the network. Distribution via a network may be performed by transmitting a modulated signal obtained by modulating a carrier wave with the program.
  The above-described processing can be executed by starting this program and executing it under the control of the OS in the same manner as other application programs.
[0062]
  When the OS shares a part of the processing, or when the OS constitutes a part of one component of the present invention, a program excluding the part is stored in the recording medium. May be. Also in this case, in the present invention, it is assumed that the recording medium stores a program for executing each function or step executed by the computer.
[0063]
【The invention's effect】
  As described above, according to the present invention, an angle demodulating apparatus and an angle demodulating method that can be easily adjusted with a simple configuration and perform a direct conversion method are realized.
  In addition, according to the present invention, an angle demodulating device and an angle demodulating method for generating a local oscillation signal based on a single reference oscillation signal and performing a direct conversion method are realized.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a basic configuration of an FM receiver according to an embodiment of the present invention.
2 is a block diagram showing a basic configuration of a local oscillator of the FM receiver of FIG. 1. FIG.
FIG. 3 is a block diagram showing a configuration of a conventional FM receiver.
[Explanation of symbols]
  1 Antenna
  2 RF amplifier
  3 duplexer
  4I, 4Q, 8I, 8Q mixer
  5I, 5Q, 104, 109 LPF
  6I, 6Q AF amplifier
  7I, 7Q DC removal section
  9, 10 Phase shifter
  11 Local oscillator
  101, 111 VCO
  102, 105, 106, 107, 112 Frequency divider
  103, 108 Phase comparator
  110 Loop filter
  12 Adder
  13 BPF
  14 IF amplifier
  15 FM detector

Claims (7)

First local oscillation signal, and a first oscillator for the first local oscillation signal 9 0 degree phase produces a different first phase signal,
Enter the angle modulation signal, the first to enter the more oscillation unit first local oscillation signal and the first phase-shift signal, the product of the said angle-modulated signal with said first local oscillation signal component frequency generates a first baseband signal comprising a component excluding the component is zero, except for the component frequency is 0 among the product of the angle modulation signal and the No. 1 Utsurishoshin of A first mixing unit for generating a second baseband signal comprising:
A second oscillation unit that generates a second local oscillation signal and a second phase-shifted signal that is 90 degrees out of phase with the second local oscillation signal;
The first baseband signal is input from the first mixing unit, the second local oscillation signal and the second phase shift signal are input from the second oscillation unit, and the first baseband signal is input. a second mixing unit for generating an intermediate frequency signal representative of the sum or difference of the product of the product and the second baseband signal and the No. 2 Utsurishoshin the No. and the second local oscillation signal,
A demodulator that generates an angle demodulated signal by inputting and demodulating the intermediate frequency signal from the second mixing unit;
The second oscillation unit includes:
A reference oscillator for generating a reference oscillation signal;
By dividing the reference oscillation signal at a predetermined first frequency dividing ratio of the second local oscillation signal having a constant correct frequency difference or sum of a predetermined intermediate frequency and the offset frequency in a predetermined range A frequency divider to generate,
The first oscillation unit inputs the reference oscillation signal, by generating a signal that converges to a frequency having a fixed ratio with respect to the frequency of the input reference oscillation signal, wherein the frequency of the angle modulated signal offset a variable frequency oscillator for generating said first local oscillation signal having a constant correct frequency to the sum or difference between the frequency,
An angle demodulator characterized by that. The reference oscillator receives the intermediate frequency signal and generates a signal that converges to a frequency having a certain ratio with respect to the carrier frequency of the input intermediate frequency signal, so that the frequency of the second local oscillation signal is A frequency control unit that generates the reference oscillation signal having a frequency multiplied by a value of the first frequency division ratio;
The angle demodulator according to claim 1. Wherein the frequency control unit, an intermediate frequency signal input, said reference oscillation signal based on the phase difference between the signal obtained by dividing a predetermined second frequency division ratio, the frequency of the reference oscillation signal is pre serial intermediate frequency signal to the frequency of determining the frequency of the reference oscillation signal so as to converge to a value having a fixed ratio, the first P hase Lock Loo for generating the reference oscillation signal having a determined frequency provided with a p control section,
The angle demodulator according to claim 2. The variable frequency oscillator divides a signal obtained by dividing the input reference oscillation signal by a predetermined third division ratio and the first local oscillation signal by a predetermined fourth division ratio. Based on the phase difference from the obtained signal, the frequency of the first local oscillation signal is adjusted so that the frequency of the first local oscillation signal converges to a value having a certain ratio to the frequency of the reference oscillation signal. determines and includes a second P hase Lock Loo p control section for generating said first local oscillation signal having a determined frequency,
The angle demodulator according to claim 1, 2 or 3. The magnitude of the offset frequency is within 300 hertz.
The angle demodulator according to any one of claims 1 to 4, wherein Generating a first local oscillation signal and a first phase-shifted signal that is 90 degrees out of phase with the first local oscillation signal;
Enter the angle modulation signal, generating a first baseband signal comprising a component having a frequency excluding the component which is 0 of the product of the angle modulation signal and the first local oscillation signal, said angle generating a second baseband signal comprising a component having a frequency excluding the component which is 0 of the product of the modulation signal and the No. 1 Utsurishoshin,
Generating a second local oscillation signal and a second phase-shifted signal that is 90 degrees out of phase with the second local oscillation signal;
Generating an intermediate frequency signal representative of the sum or difference of the product of the product and the second baseband signal and the No. 2 Utsurishoshin between the first baseband signal and the second local oscillation signal,
An angle demodulation method for generating an angle demodulated signal by detecting the intermediate frequency signal,
Said second local oscillator signal is one having an equal correct frequency difference or sum of a predetermined intermediate frequency and the offset frequency in a predetermined range, the reference oscillation signal at a predetermined first frequency dividing ratio of the frequency divider Is generated by
It said first local oscillation signal are those having an equal correct frequency to the sum or difference between the frequency and the offset frequency of the angle modulated signal, a frequency having a fixed ratio with respect to the frequency of the reference oscillation signal Generated by generating a converging signal,
An angle demodulation method characterized by the above. Computer
First local oscillation signal, and a first oscillator for the first local oscillation signal 9 0 degree phase produces a different first phase signal,
Enter the angle modulation signal, the first to enter the more oscillation unit first local oscillation signal and the first phase-shift signal, the product of the said angle-modulated signal with said first local oscillation signal component frequency generates a first baseband signal comprising a component excluding the component is zero, except for the component frequency is 0 among the product of the angle modulation signal and the No. 1 Utsurishoshin of A first mixing unit for generating a second baseband signal comprising:
A second oscillation unit that generates a second local oscillation signal and a second phase-shifted signal that is 90 degrees out of phase with the second local oscillation signal;
The first baseband signal is input from the first mixing unit, the second local oscillation signal and the second phase shift signal are input from the second oscillation unit, and the first baseband signal is input. a second mixing unit for generating an intermediate frequency signal representative of the sum or difference of products of the No. 2 Utsurishoshin a product and the second baseband signal with the second local oscillation signal with items,
Function as a demodulator that generates an angle demodulated signal by demodulating the intermediate frequency signal from the second mixing unit;
The second oscillation unit is
A reference oscillator for generating a reference oscillation signal;
By dividing the reference oscillation signal at a predetermined first frequency dividing ratio of the second local oscillation signal having a constant correct frequency difference or sum of a predetermined intermediate frequency and the offset frequency in a predetermined range Function as a divider to generate,
Wherein the first oscillating unit, and inputting the reference oscillation signal, by generating a signal that converges to a frequency having a fixed ratio with respect to the frequency of the input reference oscillation signal, wherein the frequency of the angle modulated signal offset to function as a variable frequency oscillator for generating said first local oscillation signal having a constant correct frequency to the sum or difference between the frequency,
A computer-readable recording medium on which a program for recording is recorded.

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