JP3967929B2 - Automatic frequency controller - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an automatic frequency control apparatus that maintains a frequency of a local oscillation signal used for heterodyne detection or synchronous detection of a received wave in a wireless transmission system at a value suitable for the frequency deviation of the received wave.
[0002]
[Prior art]
In recent years, mobile communication systems have gained added value through the application of highly advanced digital transmission technology and information processing technology, and have rapidly become popular in response to improved price / performance ratio of terminals and market liberalization. I am doing.
Also, in the field of mobile communication services, various types of mobile communication systems are currently used under the participation and competition of multiple communication companies, and terminals (mobile stations) of these mobile communication systems are generally High performance and reliability are required along with low cost, small size, light weight and power saving.
[0003]
Therefore, in such a mobile communication system terminal, a heterodyne detection (including homodyne detection) of a received wave that has arrived from a radio base station or the like and a local oscillation signal used for synchronous detection are generally mounted on the radio base station. It is generated under automatic frequency control (AFC) that achieves the above-mentioned requirements at low cost and with high accuracy compared to a highly stable oscillator.
[0004]
FIG. 8 is a diagram illustrating a configuration example of a reception system of a terminal on which an AFC circuit is mounted.
In the figure, a reception wave arriving at an antenna (not shown) is input to the reception unit 51, and two A / D converters 51 i and 51 q are arranged at the final stage of the reception unit 51. At the outputs of these A / D converters 51i and 51q, two demodulated signals i and q which are generated by heterodyne detection of the received wave described above by the receiving unit 51 and which are orthogonal to each other are in a predetermined format. Output as a signal. These demodulated signals i and q are given to corresponding inputs of the frequency discriminator 52, and the output of the frequency discriminator 52 is generated from the local section of the receiving unit 51 via a loop filter (LPF) 53 and a voltage controlled oscillator (VCO). Connected to input.
[0005]
In the reception system having such a configuration, the frequency discriminator 52 obtains the above-described frequency deviation of the received wave as the rate of change per phase of the demodulated signals i and q in the signal space, and calculates the deviation in time series. In this order, error signals are output as instantaneous values (here, it is assumed that they are “voltage” for simplicity).
The loop filter 53 is a signal indicating a component other than an unnecessary noise component distributed in a high frequency among the components of such an error signal (hereinafter, an instantaneous value of the voltage of such a signal is referred to as a “control voltage”). The voltage controlled oscillator 54 sequentially updates the oscillation frequency in the direction in which the extracted component is compressed.
[0006]
Therefore, the receiving unit 51 is simpler in configuration and smaller in scale than a highly stable oscillator such as the frequency discriminator 52, the loop filter 53, and the voltage controlled oscillator 54, and is suitable for IC implementation and high-density mounting. The received wave can be detected stably and accurately in accordance with the local oscillation signal generated by the circuit.
[0007]
[Problems to be solved by the invention]
By the way, in the above-described receiving system, the level of the received wave arriving from the radio base station at the terminal equipped with the receiving system is greatly reduced due to shadowing or the like, and therefore the SN ratio can be significantly degraded. .
During the period in which such shadowing is occurring, the amplitude of the instantaneous value of the error signal described above changes randomly, and the average value of the amplitude is substantially “0”.
However, the demodulated signal includes not only an offset caused by deviations or fluctuations in characteristics of the A / D converters 51i, 51q and other characteristics (for example, change depending on environmental conditions such as temperature), but also A / D conversion. Since the quantization error generated in the above process is also superimposed, the average value of the amplitude is not actually “0”.
[0008]
That is, during the period in which shadowing occurs, the control voltage input to the voltage controlled oscillator 54 also shifts with time as shown in FIG. 9 (1), and such shadowing is eliminated. However, the deterioration of the S / N ratio of the demodulated signals i and q is not corrected until the time when the error generated in the frequency of the local signal is compressed with a predetermined accuracy in accordance with the above-described offset and quantization noise.
[0009]
Therefore, any wireless transmission path formed between the base station and the channel control is not always stably maintained, and there is a possibility that the call quality and the service quality are unnecessarily deteriorated.
An object of the present invention is to provide an automatic frequency control device that can flexibly adapt to fluctuations in the characteristics of a wireless transmission path and maintain high transmission quality without greatly changing the basic configuration.
[0010]
[Means for Solving the Problems]
FIG. 1 is a principle block diagram of the present invention.
In the first aspect of the invention, the frequency deviation measuring means 11 measures the frequency deviation of the received wave. The feedback control means 13 determines whether or not the deviation measured in this way belongs to a specified value range. Further, when the determination result is true, the feedback control means 13 negatively feeds back the deviation to the variable frequency oscillating means 12 that generates the local oscillation signal used for the heterodyne detection or the synchronous detection of the received wave described above. . However, when the determination result is false, the feedback control unit 13 keeps the oscillation frequency of the variable frequency oscillation unit 12 constant or suppresses the update of the oscillation frequency.
[0011]
That is, when the deviation of the frequency of the received wave actually measured by the frequency deviation measuring means 11 is large enough to make the above-mentioned determination result false, it is used for heterodyne detection or synchronous detection of the received wave. It is not applied to automatic frequency control of the frequency of power signal.
Therefore, as long as the free-running frequency of the variable frequency oscillating means 12 is equal to an appropriate value matched with the frequency of the received wave, or the oscillation frequency of the variable frequency oscillating means 12 is set separately to the appropriate value, the level of the received wave is Even in the case of a significant reduction in the primary, the accuracy of the heterodyne detection or the synchronous detection described above is maintained without unnecessary reduction.
[0012]
Also The period specifying unit 14 specifies a period from the start to the time when the oscillation frequency of the variable frequency oscillating unit 12 becomes a steady value. The feedback control means 13 negatively feeds back the deviation measured by the frequency deviation measuring means 11 to the variable frequency oscillating means 12 regardless of the result of the above-described determination during the period specified in this way.
[0013]
That is, the feedback control for maintaining the oscillation frequency of the variable frequency oscillating means 12 at a value suitable for the frequency of the received wave immediately shifts to the steady state without being hindered by the feedback control means 13 in the transient response process immediately after starting. To do.
Therefore, the responsiveness at the time of starting is maintained high without being lowered even if the feedback control means 13 is provided.
[0014]
Also The period specifying unit 14B specifies a period from the time when the oscillation frequency of the variable frequency oscillating unit 12 is switched to the time when the oscillation frequency becomes a steady value. The feedback control means 13 negatively feeds back the deviation measured by the frequency deviation measuring means 11 to the variable frequency oscillating means 12 regardless of the result of the above-described determination during the period specified in this way.
[0015]
That is, the feedback control for maintaining the oscillation frequency of the variable frequency oscillating means 12 at a value suitable for the frequency of the received wave is promptly performed without being interrupted by the feedback control means 13 even when the frequency of the received wave to be received is switched. To the steady state.
Therefore, the responsiveness to channel switching is maintained high without decreasing even if the feedback control means 13 is provided.
[0016]
In particular, Claim 1 The feedback control means 13 is a feedback in which the deviation measured by the frequency deviation measuring means 11 is applied to a period other than that period during the period specified by the period specifying means 14, 14A, 14B, 14C. Negative feedback to the variable frequency oscillating means 12 is performed at a feedback rate larger than the rate.
That is, the steady state of the feedback control that maintains the oscillation frequency of the variable frequency oscillating means 12 at a value suitable for the frequency of the received wave, both at the time of starting and when the frequency of the received wave to be received is switched. The transition to is quickly achieved as compared to the case where the above-described feedback rate is kept constant.
[0017]
Therefore, the responsiveness at the time of starting and / or channel switching is improved.
Also All or a part of the frequency deviation measuring means 11, the variable frequency oscillating means 12, the feedback control means 13, and the period specifying means 14, 14A, 14B, and 14C function in a form consistent with the channel control related to reception of the received wave. .
[0018]
That is, not only the configuration or characteristics of all or part of the frequency deviation measuring unit 11, the variable frequency oscillating unit 12, the feedback control unit 13, and the period specifying units 14, 14A, 14B, 14C, but also various zone configurations, channel arrangements, Flexible adaptation to frequency allocation, multiple access schemes, modulation schemes, etc. is possible.
Therefore, heterodyne detection and synchronous detection of a desired received wave can be achieved smoothly.
[0019]
The first related to the invention of claim 1 Technology Then, the above-mentioned specified value range is a deviation that can be measured by the frequency deviation measuring unit 11 in the process of steady automatic frequency control performed in cooperation with the frequency deviation measuring unit 11 and the feedback control unit 13. It is a range.
In other words, the frequency deviation of the received wave actually measured by the frequency deviation measuring means 11 is applied only to steady automatic frequency control of the frequency of the local signal to be used for heterodyne detection or synchronous detection of the received wave. Is done.
[0020]
Therefore, even when the level of the received wave is significantly reduced due to shadowing or channel switching, the accuracy of the above heterodyne detection or synchronous detection is maintained high without being unnecessarily reduced.
A second related to the invention of claim 1 Technology Then, the period specifying unit 14A specifies a period from the start to the time when the oscillation frequency of the variable frequency oscillating unit 12 is guaranteed to be a steady value. The feedback control means 13 negatively feeds back the deviation measured by the frequency deviation measuring means 11 to the variable frequency oscillating means 12 regardless of the result of the above-described determination during the period specified in this way.
[0021]
That is, the feedback control for maintaining the oscillation frequency of the variable frequency oscillation means 12 at a value suitable for the frequency of the received wave is performed in advance in the process of transient response immediately after the start. As long as given, it shifts to a steady state promptly without monitoring at that time.
Accordingly, the responsiveness at the time of starting is maintained high without complicating the configuration even if the feedback control means 13 is provided.
[0022]
A third related to the invention of claim 1 Technology Then, the period specifying unit 14C specifies a period from the time when the oscillation frequency of the variable frequency oscillating unit 12 is switched to the time when the oscillation frequency is guaranteed to be a steady value. The feedback control means 13 negatively feeds back the deviation measured by the frequency deviation measuring means 11 to the variable frequency oscillating means 12 regardless of the result of the above-described determination during the period specified in this way.
[0023]
That is, in the feedback control for maintaining the oscillation frequency of the variable frequency oscillating means 12 at a value suitable for the frequency of the received wave, in the process of transient response immediately after the channel switching, such channel switching at the above-mentioned time point is performed. As long as the relative time with respect to the point in time is given with high accuracy in advance, the state is promptly shifted to the steady state without being monitored.
[0024]
Accordingly, the responsiveness at the time of starting is maintained high without complicating the configuration even if the feedback control means 13 is provided.
The first related to the invention of claim 1 Technology Then, the feedback control unit 13 omits the above-described determination in the periods specified by the period specifying units 14, 14A, 14B, and 14C.
[0025]
That is, such determination is suspended until the feedback control for maintaining the oscillation frequency of the variable frequency oscillating means 12 at a value suitable for the frequency of the received wave shifts to a steady state.
Therefore, it is possible to reduce the power and processing amount required for the above-described determination, and it is possible to comprehensively reduce the cost and improve the reliability.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 2 is a diagram showing a first embodiment of the present invention.
In the present embodiment, the feedback control unit 21 is provided between the output of the frequency discriminator 52 and the loop filter 53.
FIG. 3 is a diagram (1) for explaining the operation of the first embodiment of the present invention.
FIG. 4 is a diagram (2) for explaining the operation of the first embodiment of the present invention.
[0027]
The operation of the first embodiment of the present invention will be described below with reference to FIGS.
The demodulated signals i and q output by the receiving unit 51 (A / D converters 51i and 51q) generally have an angular frequency ω of the received wave, an amplitude A in the baseband region of the received wave, and a time t. It is shown by the following formula (1).
i = A ^1/2 ・ Cos (ωt) (1)
q = A ^{1 /} 2 ・ sin (ωt) (2)
Further, the instantaneous value e of the error signal output by the frequency discriminator 52 is generally given by the following equation (3) indicating the amount of phase fluctuation per time T. Therefore, as shown in FIG. It is given as a sine function of the fluctuation amount ΔωT (= θ).
[0028]
e = A · sin (ΔωT) (3)
Therefore, in the state where the oscillation frequency of the voltage controlled oscillator 54 is maintained in an appropriate value range under the feedback control performed in cooperation with the frequency discriminator 52 and the loop filter 53, the absolute value of the instantaneous value e of the error signal is The amount of fluctuation of the phase of the local oscillation signal generated by the voltage controlled oscillator 54 for each symbol period (here, for the sake of simplicity, takes a value that is greater than or equal to “−Δθ” and less than or equal to “Δθ (> 0)”). Is assumed to be less than the absolute value of the value a given by the following equation (4).
[0029]
a = A · sin (Δθ) (4)
The feedback control unit 21 sets the threshold value x at which the following inequalities (5) and (6) are satisfied with respect to the value a represented by the above equation (4). ^- , X ⁺ Is given in advance.
x ^- <-A (5)
x ⁺ > A ... (6)
Further, the feedback control unit 21 performs the following process each time the frequency discriminator 52 gives the above-described instantaneous value e of the error signal in the symbol period.
[0030]
(1) The latest instantaneous value e and the above threshold x ^- , X ⁺ Whether or not the following inequality (7) holds is determined.
x ^- ≦ e ≦ x ⁺ … (7)
(2) If the result of this determination is true, the error signal output by the frequency discriminator 52 is passed to the loop filter 53 without any processing.
[0031]
(3) However, when the result of the determination is false, it is assumed that the instantaneous value is a constant value (here, “0” for simplicity) instead of such an error signal. ) Is provided to the loop filter 53 (hereinafter referred to as “alternative error signal”).
That is, the deviation of the control voltage applied to the voltage controlled oscillator 54 via the loop filter 53 is, for example, because the level of the received wave is significantly lowered due to the above-described shadowing, so that the above inequality (7) is established. Even if the absolute value of the instantaneous value e of the error signal is increased to such an extent that the time constant inherent in the loop filter 53 is sufficiently larger than the above-described symbol period, FIG. As shown, the oscillation frequency of the voltage controlled oscillator 54 is suppressed to a small value so that it does not fluctuate excessively.
[0032]
Therefore, according to the present embodiment, the heterodyne detection of the received wave can be stably and highly accurately performed during a period in which the loss of the propagation path of the received wave suddenly or drastically changes without significantly changing the configuration. Is called.
In the present embodiment, the threshold value x described above. ^- , X ⁺ As long as the above-mentioned inequalities (5) and (6) are satisfied, for example, when this embodiment is applied to a terminal of a mobile communication system, it is acceptable for the characteristics of the radio base station of the mobile communication system. It may be set to any value consistent with the maximum possible deviation, zone configuration of this mobile communication system, channel arrangement, multiple access scheme, modulation scheme, channel control scheme and other attributes.
[0033]
FIG. 5 is a diagram showing a second embodiment of the present invention.
In the present embodiment, a loop filter 31 is provided instead of the loop filter 53 described above, and a common contact of the switch 32 is connected to a control terminal of the loop filter 31. Coefficients α and β, which will be described later, are respectively given to one contact and the other contact of the switch 32, and the output of the feedback control unit 21 is connected to one contact of the switch 33 instead of the input of the loop filter 31. . The other contact and the common contact of the switch 33 are connected to the output of the frequency discriminator 52 and the input of the loop filter 31, respectively. The output of the timer 34 is connected to the control terminals of the switches 32 and 33.
[0034]
The operation of the second embodiment of the present invention will be described below with reference to FIG.
First, the operations of the receiving unit 51, the A / D converters 51i and 51q, the frequency discriminator 52, the feedback control unit 21, and the voltage controlled oscillator 54 are the same as those in the first embodiment described above. Here, the description is omitted.
At the start, the timer 34 gives a control signal having a predetermined logical value to the switches 32 and 33, and measures the time over an interval described later.
[0035]
On the other hand, the switch 32 provides the loop filter 31 with the coefficients α and β “in comparison with the loop filter 53 corresponding to the logical value of such a control signal and provided in the first embodiment. The loop filter 31 is given a coefficient α ”that satisfies both or one of the following conditions.
・ The gain of all or part of the passband increases (Figs. 6 (a) and (b)).
[0036]
・ The width of the passband increases (Fig. 6 (c)).
Further, the switch 33 connects the output of the frequency discriminator 52 to the input of the loop filter 31 in accordance with the logical value of the control signal described above.
Further, the above-described interval is “the period during which the output of the frequency discriminator 52 is directly connected to the input of the loop filter 31 and the coefficient α is given to the loop filter 31”, and the oscillation frequency of the voltage controlled oscillator 54 is desired. The time required to converge to the frequency of the local oscillation signal with a predetermined accuracy ”is set in advance.
[0037]
When the timer 32 completes timing over such an interval, the logic value of the control signal described above is inverted.
The switch 32 indicates that the loop filter 31 has the same filtering characteristics as the filtering characteristics of the loop filter 53 corresponding to the logical value of the control signal and provided in the first embodiment, among the coefficients α and β. A coefficient β ”set for the loop filter 31 is given.
[0038]
Further, the switch 33 connects the output of the feedback control unit 21 to the input of the loop filter 31 instead of the output of the frequency discriminator 52 according to the logical value of the control signal inverted in this way.
That is, at the time of starting, until the time equal to the above-described interval elapses, the output of the voltage controlled oscillator 54 reaches the control input of the voltage controlled oscillator 54 via the receiver 51, the frequency discriminator 52 and the loop filter 31. The feedback path does not include the feedback control unit 21, and the total gain of the feedback path is set to a value larger than the gain after the elapse of such time.
[0039]
Thus, according to the present embodiment, at the time of start-up, the frequency of the local oscillation signal supplied to the receiving unit 51 is such that the frequency of the local oscillation signal is “the frequency of the local oscillation signal adapted to the frequency of the desired reception wave”. Even if it is significantly different from the above, the feedback control unit 21 is varied without any involvement, and quickly converges to a “value adapted to the frequency of the desired received wave”.
[0040]
Therefore, even if the feedback control unit 21 is provided, an unnecessary increase in time required for automatic frequency control at the time of start-up is avoided, and the performance, transmission quality, and service quality of the receiving system and terminal to which the present invention is applied are reduced. Overall high.
In the present embodiment, the timer 34 measures the time over the aforementioned interval only at the time of starting, and updates the logical value of the control signal described above in synchronization with the start and end of the time measurement.
[0041]
However, such timekeeping and “processing in which the logical value of this control signal is updated in synchronization with the start and end of the timekeeping” are performed in synchronization with “channel switching performed under channel control”. Accordingly, flexible adaptation to various combinations of zone configurations, channel arrangements, frequency arrangements, multiple access schemes, and modulation schemes may be achieved.
[0042]
In the present embodiment, the above-described interval is given in advance as a predetermined constant.
However, the present invention is not limited to such a configuration. For example, the time point when the oscillation frequency of the voltage controlled oscillator 54 converges to “the frequency of a local oscillation signal adapted to a desired reception wave” (hereinafter referred to as “convergence time point”). )) Is detected separately, the above-mentioned timing is terminated at any one of the following times, thereby causing deviations in hardware characteristics, various zone configurations, channel arrangements, frequency arrangements, and multiple access methods. Flexible adaptation to modulation schemes and the like may be achieved.
[0043]
・ Convergence point
・ Time that is determined relative to the time of convergence and is consistent with predetermined channel control
・ Time that converges and the time that precedes the time series in the time that is equal to the interval mentioned above
Furthermore, in this embodiment, the feedback control unit 21 performs the above-described determination regardless of whether the output of the feedback control unit 21 is connected to the input of the loop filter 31 via the switch 33. .
[0044]
However, a period in which the output of the feedback control unit 21 is connected to the input of the loop filter 31 via the switch 33 is identified according to the logical value of the control signal described above, and the above-described determination is performed only during that period. For example, unnecessary power consumption may be avoided, or the amount of processing may be reduced.
Further, in each of the above-described embodiments, the frequency discriminator 52 obtains the frequency deviation of the received wave on the assumption that the amplitude components of all signal points that the received wave can take on a symbol basis are common.
[0045]
However, the present invention is not limited to a wireless transmission system to which such a signal point arrangement modulation method is applied. For example, there is a modulation method in which the amplitude components of individual signal points are not common, such as APSK and QAM. When applied, as shown in FIG. 7, the phase of each signal point (symbol) in the signal space (= tan ^-1 (q / i)) may be obtained by direct arithmetic operation, and a frequency discriminator for obtaining the frequency deviation of the received wave as the rate of change of the phase for each symbol period may be provided in place of the frequency discriminator 52 described above.
[0046]
Further, in each of the above-described embodiments, the reception wave to be heterodyne detected by the reception unit 51 and the frequency of the reception wave are given in advance, and a local oscillation signal having a frequency suitable for the frequency is generated by the voltage controlled oscillator 54. Yes.
However, the present invention is not limited to such a configuration. For example, the receiver 51, the frequency discriminator 52, the feedback controller 21, the loop filters 53 and 31, the voltage controlled oscillator 54, the timer 34, and the switches 32 and 33 are all included. Alternatively, a part of the operation and the operation mode may be determined under the initiative of predetermined channel control, so that flexible adaptation to various wireless transmission systems may be achieved.
[0047]
Moreover, in each embodiment mentioned above, the modulation system applied in the transmission end of the received wave which should be heterodyne detected by the receiving part is not specifically shown.
However, with regard to such a modulation method, in the present invention, any of a digital modulation method and an analog modulation method may be used as long as the discrimination of the frequency deviation of the received wave is achieved with a desired accuracy for each symbol. .
[0048]
Further, in each of the above-described embodiments, the present invention is applied to a reception system that is mounted on a terminal of a mobile communication system and that detects a received wave by heterodyne.
However, the present invention is not limited to the terminal of such a mobile communication system or the receiving system where heterodyne detection is performed, and the electric field strength and transmission quality of the received wave are significantly deteriorated due to the fluctuation of the transmission characteristic of the wireless transmission path. As long as there is a possibility of this, it can be applied to any wireless transmission system.
[0049]
In each of the above-described embodiments, the present invention is applied to automatic frequency control of a local oscillation signal used for heterodyne detection of a received wave.
However, the present invention is not limited to such automatic frequency control of a local oscillation signal, and for example, to automatic frequency control of a reference carrier used for synchronous detection of a received wave in a baseband region or a desired intermediate frequency region. The same applies.
[0050]
Furthermore, the present invention is not limited to the above-described embodiments, and various embodiments can be made within the scope of the present invention, and any improvements can be made to some or all of the components. Good.
Hereinafter, the configurations of the invention disclosed in each of the above-described embodiments are arranged hierarchically and multifacetedly and sequentially listed as additional items.
[0051]
(Supplementary note 1) Frequency deviation measuring means 11 for measuring the frequency deviation of the received wave;
It is determined whether or not the deviation measured by the frequency deviation measuring means 11 belongs to a specified value range, and when the determination result is true, the received wave is subjected to heterodyne detection or synchronous detection. The deviation is negatively fed back to the variable frequency oscillating means 12 that generates the local oscillation signal, and when the result of this determination is false, the oscillation frequency of the variable frequency oscillating means 12 is kept constant or the oscillation frequency is updated. Feedback control means 13 for suppressing
An automatic frequency control device comprising:
(Supplementary Note 2) In the automatic frequency control device according to Supplementary Note 1,
The prescribed value range is
This is a deviation value range that can be measured by the frequency deviation measuring means 11 in the process of steady automatic frequency control performed in cooperation with the frequency deviation measuring means 11 and the feedback control means 13.
An automatic frequency control device characterized by that.
[0052]
(Supplementary Note 3) In the automatic frequency control device according to Supplementary Note 1 or Supplementary Note 2,
A period specifying unit 14 for specifying a period from the start to the time when the oscillation frequency of the variable frequency oscillating unit 12 becomes a steady value;
The feedback control means 13
Regardless of the result of the determination, the deviation measured by the frequency deviation measuring means 11 is negatively fed back to the variable frequency oscillating means 12 during the period specified by the period specifying means 14.
An automatic frequency control device characterized by that.
(Supplementary Note 4) In the automatic frequency control device according to Supplementary Note 1 or Supplementary Note 2,
A period specifying means 14A for specifying a period from the start to the time when the oscillation frequency of the variable frequency oscillating means 12 is guaranteed to be a steady value;
The feedback control means 13
Regardless of the result of the determination, the deviation measured by the frequency deviation measuring means 11 is negatively fed back to the variable frequency oscillating means 12 during the period specified by the period specifying means 14A.
An automatic frequency control device characterized by that.
[0053]
(Supplementary Note 5) In the automatic frequency control device according to Supplementary Note 1 or Supplementary Note 2,
Period specifying means 14B for specifying a period from the time when the oscillation frequency of the variable frequency oscillation means 12 is switched to the time when the oscillation frequency becomes a steady value;
The feedback control means 13
Regardless of the result of the determination, the deviation measured by the frequency deviation measuring unit 11 is negatively fed back to the variable frequency oscillating unit 12 during the period specified by the period specifying unit 14B.
An automatic frequency control device characterized by that.
(Supplementary Note 6) In the automatic frequency control device according to Supplementary Note 1 or Supplementary Note 2,
A period specifying means 14C for specifying a period from the time when the oscillation frequency of the variable frequency oscillation means 12 is switched to the time when the oscillation frequency is guaranteed to be a steady value;
The feedback control means 13
During the period specified by the period specifying unit 14C, the deviation measured by the frequency deviation measuring unit 11 is negatively fed back to the variable frequency oscillating unit 12 regardless of the result of the determination.
An automatic frequency control device characterized by that.
[0054]
(Supplementary note 7) In the automatic frequency control device according to supplementary notes 3 to 6,
The feedback control means 13
The determination is omitted in the period specified by the period specifying means 14, 14A, 14B, 14C.
An automatic frequency control device characterized by that.
[0055]
(Appendix 8) In the automatic frequency control device according to any one of appendices 3 to 7,
The feedback control means 13
In the period specified by the period specifying means 14, 14A, 14B, 14C, the deviation measured by the frequency deviation measuring means 11 is used for the variable frequency oscillation with a feedback rate larger than a feedback rate applied to a period other than that period. Negative feedback to means 12
An automatic frequency control device characterized by that.
(Appendix 9) In the automatic frequency control device according to any one of appendices 1 to 8,
All or part of the frequency deviation measuring means 11, the variable frequency oscillating means 12, the feedback control means 13, and the period specifying means 14, 14A, 14B, 14C are:
Functions in a form consistent with channel control related to reception of the received wave
An automatic frequency control device characterized by that.
[0056]
【The invention's effect】
By the way, in the above-described invention according to the first aspect, even when the level of the received wave is significantly reduced temporarily, the accuracy of the heterodyne detection or the synchronous detection of the received wave is maintained without unnecessary reduction. Is done.
[0057]
In particular In addition, the responsiveness at the time of starting and / or channel switching is improved.
In addition, the first related to the invention of claim 1 Technology Then, even when the level of the received wave is significantly lowered due to shadowing or channel switching, the accuracy of the heterodyne detection or the synchronous detection of the received wave is maintained without unnecessary reduction.
[0058]
Furthermore, second and third related to the invention of claim 1 Technology Then, the responsiveness at the time of starting is maintained high without complicating the configuration.
Further, in the invention related to the invention described in claim 1, it is possible to reduce the electric power and the processing amount required for the above-described determination, and it is possible to comprehensively reduce the cost and improve the reliability.
[0059]
Therefore, in the radio transmission system to which these inventions are applied, the transmission quality and service quality can be increased at a low cost, and the flexibility and possibility of improving the performance and added value are ensured.
[Brief description of the drawings]
FIG. 1 is a principle block diagram of the present invention.
FIG. 2 is a diagram showing a first embodiment of the present invention.
FIG. 3 is a diagram (1) for explaining the operation of the first embodiment of the present invention;
FIG. 4 is a diagram (2) for explaining the operation of the first embodiment of the present invention.
FIG. 5 is a diagram showing a second embodiment of the present invention.
FIG. 6 is a diagram illustrating an aspect of characteristics of a loop filter in the present embodiment.
FIG. 7 is a diagram showing another configuration of the frequency discriminator.
FIG. 8 is a diagram illustrating a configuration example of a reception system of a terminal equipped with an AFC circuit.
FIG. 9 is a diagram illustrating a problem of a conventional example.
[Explanation of symbols]
11 Frequency deviation measuring means
12 Variable frequency oscillation means
13 Feedback control means
14, 14A, 14B, 14C Period specifying means
21 Feedback control unit
31, 53 Loop filter (LPF)
32, 33 switch
34 Timer
51 Receiver
51i, 51q A / D converter (A / D)
52 Frequency discriminator
54 Voltage controlled oscillator (VCO)

Claims (1)

A frequency deviation measuring means for measuring the deviation of the frequency of the received wave;
A station used to determine whether or not the deviation measured by the frequency deviation measuring means belongs to a specified value range, and when the determination result is true, the station is used for heterodyne detection or synchronous detection of the received wave The deviation is fed back to the variable frequency oscillating means for generating the oscillation signal, and when the determination result is false, the oscillation frequency of the variable frequency oscillating means is kept constant, or the feedback that suppresses the update of the oscillation frequency is performed. Control means ;
Period specifying means for specifying a period from the start to the time when the oscillation frequency of the variable frequency oscillating means becomes a steady value ,
The feedback control means includes
In the period specified by the period specifying means, the deviation measured by the frequency deviation measuring means is negatively fed back to the variable frequency oscillating means with a feedback rate larger than a feedback rate applied in a period other than the period. Automatic frequency control device.

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