JP5381268B2 - Receiving device, and receiving module and electronic device using the same - Google Patents

Description

The present invention relates to a receiving apparatus using a synthesizer having a feature in a charging / discharging method of a smoothing circuit for accumulating charges, a receiving module using the same, and an electronic apparatus.

  Hereinafter, for example, a conventional synthesizer that performs temperature compensation of a reference oscillator will be described with reference to FIG.

  FIG. 9 shows a block diagram of a synthesizer 100 that performs temperature compensation of a conventional reference oscillator. In the conventional synthesizer 100, the reference oscillation signal output from the reference oscillator 101 is frequency-divided by the first frequency divider 102 and then input to the comparator 103, and the output signal of the comparator 103 is further converted to a low-pass filter 104. Is stored as electric charge in a smoothing circuit comprising: Based on the voltage output from the smoothing circuit of the low-pass filter 104, the oscillator 105 outputs the oscillation signal as a local signal, and inputs the other output to the second frequency divider 106. The second frequency divider 106 divides the signal by the frequency division number designated by the control circuit 107 in accordance with the channel designation and outputs it to the comparator 103. The comparator 103 compares the input signal from the second frequency divider 106 with the input signal from the first frequency divider 102 as described above. The above is a general operation of the frequency synthesizer. In the synthesizer 100 shown in FIG. 9, the frequency dividing number of the second frequency divider 106 is further controlled by the temperature detected by the temperature detecting unit 108. Yes. Briefly describing the operation, the temperature detection unit 108 detects the ambient temperature, the A / D converter 109 converts the temperature into a digital signal, and a predetermined correction value is stored in advance from the memory 110 in which a correction value based on the temperature is stored. Is output to the control circuit 107, and the frequency dividing number of the second frequency divider 106 is changed.

  As for how to change the frequency dividing number, in the operation of the general frequency synthesizer, the charge accumulated in the smoothing circuit composed of the low-pass filter 104 is once returned to a preset value and then desired. The method of selecting the division ratio was taken.

  For example, Patent Document 1 is known as a prior art document related to the present invention.

Japanese Patent Laid-Open No. 3-209917

  However, when the control circuit 107 controls the second frequency divider 106 in response to the temperature change, the charge accumulated in the smoothing circuit composed of the low-pass filter 104 is returned to a preset value every time. Each time, the oscillation frequency of the oscillator 105 fluctuates greatly and the phase noise increases. As a result, in the receiving apparatus using the oscillation signal of the synthesizer 100 as a local signal, the C / N (Carrier / Noise) characteristics of the received signal are significantly deteriorated, and the reception quality is deteriorated.

  This is not a problem in a normal channel switching operation. This is because it is unlikely that the television can be viewed at the moment of channel switching, and image disturbance due to phase noise disturbance of several tens of milliseconds to several seconds is allowed.

  This is because channel switching is intentionally performed by the viewer, and it is known that the image is disturbed and not frequently.

  However, as in Patent Document 1, when the frequency division ratio is switched depending on the temperature, the frequency increases. In particular, when a vibrator having poor frequency temperature characteristics such as a MEMS vibrator made of silicon or the like is used, the switching frequency is increased, and the reception quality is significantly deteriorated.

Therefore, an object of the present invention is to provide a receiving apparatus using such a synthesizer with little phase noise degradation.

In order to achieve the above object, the control unit of the receiving apparatus of the present invention outputs the temperature detection unit that detects the temperature while holding the residual charge accumulated in the smoothing circuit of the loop filter that outputs the voltage to the oscillator. In this configuration, the frequency division ratio of the frequency divider is changed based on the signal.

With the above configuration, the synthesizer used in the receiving apparatus of the present invention maintains the residual charge accumulated in the smoothing circuit when the control unit controls the frequency divider in response to a temperature change, so that the oscillation frequency of the oscillator is large. Fluctuation can be suppressed, and thereby phase noise in the synthesizer can be reduced. As a result, in a receiving device that uses the oscillation signal of this synthesizer as a local signal, it is possible to suppress the deterioration of the C / N (Carrier / Noise) characteristics of the received signal.

Block diagram of the synthesizer of the present invention Block diagram of charge pump and loop filter in the embodiment of the present invention The figure which shows the relationship between the control voltage and oscillation frequency of the oscillator in this Embodiment (A) The figure which shows the oscillation frequency change at the time of the division ratio change of the synthesizer of this invention, (b) The figure which shows the oscillation frequency change at the time of the division ratio change of the conventional synthesizer (A) The figure which shows the C / N characteristic when the crystal oscillator is used, (b) The figure which shows the C / N characteristic when the MEMS oscillator is used Conceptual diagram of a TV receiving module using the synthesizer of the present invention Conceptual diagram of a TV receiving module using the synthesizer of the present invention Conceptual diagram of a TV receiving module using the synthesizer of the present invention Block diagram of a conventional synthesizer

(Embodiment 1)
Hereinafter, the synthesizer of the first embodiment will be described with reference to FIG. In FIG. 1, a synthesizer 1 includes an oscillator 5 that outputs an oscillation signal, a frequency divider 6 that divides the output signal of the oscillator 5 based on control from the control unit 7, and a second frequency divider from the reference oscillator 2. The comparator 4 that compares the reference oscillation signal output via the frequency divider 3 with the output signal from the frequency divider 6 and outputs a signal indicating the comparison result, and the comparison result output from the comparator 4 A charge pump 18 for converting a signal based on the current component into a current component, and a loop filter 17 for accumulating charges by the current output from the charge pump 18 and outputting a voltage based on the accumulated charges to the oscillator 5. The oscillator 5 described here is a VCO (Voltage Control Oscillator) whose frequency is swept by a DC voltage, and the oscillator 5 outputs from the loop filter 17. Determining the frequency of the oscillation signal based on the voltage. Here, the control unit 7 does not forcibly return the electric charge accumulated in the loop filter 17 to a preset value, and the division of the frequency divider 6 based on the output signal of the temperature detection unit 8 that detects the temperature. Change the circumference ratio.

  The synthesizer module according to the present embodiment includes a synthesizer 1 and a reference oscillator 2 composed of a vibrator composed of a MEMS (Micro Electro Mechanical Systems) element. The output signal is input to the comparator 4 via the second frequency divider 3. The receiving device 50 equipped with the synthesizer 1 includes the synthesizer 1 and a mixer 29 that converts the frequency of the received signal based on the oscillation signal from the synthesizer 1. Furthermore, an electronic device (not shown) on which the synthesizer 1 is mounted is connected to a signal processing unit (not shown) connected to the output side of the mixer 29 in the receiving device 50 and to the output side of this signal processing unit. A display unit (not shown).

Next, the frequency divider 6 will be described in detail. In FIG. 1, the frequency divider 6 is periodically divided based on control signals from the control unit 7 (integer frequency division number M (M is an integer) and fractional frequency division number N (N is an integer)). A variable frequency divider 15 that operates at a frequency division ratio “M” and a frequency division ratio “M + 1” is provided. The variable frequency divider 15 divides the oscillation signal fVCO from the oscillator 5 by a fraction or an integer determined according to the switching period between the frequency division ratios “M” and “M + 1”, and outputs a comparison frequency fcomp. . Further, the frequency divider 6 has a frequency division ratio “M” and a frequency division ratio “M + 1” based on the fractional frequency division number N which is a control signal from the control unit 7 and the reference signal fREF from the reference oscillator 2. An accumulator 9 for determining a switching cycle is provided. This accumulator 9 cumulatively adds the fractional frequency division number N in the period of fXTAL, and when the cumulative addition value exceeds the allowable holding amount 2 ⁿ (expressed as binary n bits), the overflow data value “1” is set. While outputting to the adder 14, the allowable addition amount ²ⁿ is subtracted from the cumulative addition value, and the same cumulative addition is continued again. Further, the frequency divider 6 adds the integer frequency division number M output from the control unit 7 and the overflow data value “0” or “1” output from the accumulator 9, and adds “M” or An adder 14 that outputs the value of “M + 1” to the variable frequency divider 15 is provided. That is, the frequency division ratio of the variable frequency divider 15 is “M + 1” only when the accumulator 9 outputs the overflow data “1”, and “M” otherwise.

  Hereinafter, a series of operations of the variable frequency divider 15 and the accumulator 9 will be described in further detail.

  The accumulator 9 outputs overflow data (Expression 1) times at an arbitrary specific time (1 / fXTAL) × α determined for convenience, and the variable frequency divider 15 at this time sets the frequency division ratio to “M + 1”.

  On the other hand, in the remaining time (Equation 2) when the accumulator 9 does not output overflow data, the variable frequency divider 15 sets the frequency division ratio to “M”.

As a result, the average frequency division ratio at the specific time (1 / fXTAL) × α, that is, the fractional frequency division ratio DIV1 is (Equation 3), and the integer frequency division number M output from the control unit 7 and the fractional frequency division number N and the allowable holding amount 2 ⁿ of the accumulator 9.

  Further, the relationship among the fractional frequency division ratio DIV1 of the frequency divider 6, the oscillation signal fVCO, and the comparison signal fcomp is expressed by (Equation 4).

  Here, in the first embodiment, the frequency divider 6 adds the overflow data “0” or “1” and the integer frequency division number M by the adder 14, and the addition result is supplied to the variable frequency divider 15. Although it is configured to input, the adder 14 is not necessarily required. That is, the frequency divider 6 is a variable frequency divider capable of performing different frequency division operations of “M” or “M + 1” by individually inputting the overflow data “0” or “1” and the integer frequency division number M. Even in the case of having the same, an equivalent operation can be realized.

  Next, operations of the charge pump 18 and the loop filter 17 in FIG. 1 will be described in detail. FIG. 2 shows the internal configuration of the charge pump 18 and the loop filter 17.

  The charge pump 18 has a current source 30 that can switch current input / output according to the comparison result from the comparator 4, and the current source 30 includes a comparison signal fcomp output from the comparator 4 and a reference signal fREF. Two control signals VCO_up and VCO_down corresponding to the phase relationship (frequency relationship) (VCO_up becomes “1” when fcomp <fREF and VCO_down becomes “1” when fcomp> fREF) are input, and each control signal is And two current input / output switches SW_fup31 and SW_fdown32 (SW_fup31 is turned on when a current is output, and SW_fdown32 is turned on when a current is input).

  Further, the current source 30 forcibly changes the current input / output switch SW_fup31 from VCO_up to a fixed value “0” that does not depend on the output of the phase shifter 4, and similarly forcibly changes SW_fdown32 from the switching signal VCO_down A reset unit 34 that switches to a fixed value “1” that does not depend on the output, and the reset unit 34 are controlled, and an AND logic output that inputs a channel switching signal and a reset signal from the control unit 7 is output to the reset unit 34. A reset control unit 35.

  The loop filter 17 includes a smoothing circuit that charges or discharges charges based on the current from the current source 30 and smoothes the changed potential, and outputs the smoothed potential to the oscillator 5. It is composed of a capacitive element and a resistive element.

  In the configuration of FIG. 2 as described above, the charge pump 18 is forced regardless of the normal operation mode in which current is dynamically input / output according to the comparison result from the comparator 4 and the comparison result from the comparator 4. It has a reset mode for controlling the current and controls the charge or discharge of the electric charge smoothed by the loop filter 17 to vary the oscillation frequency from the oscillator 5.

  Regarding the operation of FIG. 2, the normal operation mode will be described first. As an example, the oscillator 5 of the present embodiment operates in the relationship between the control voltage and the oscillation frequency shown in FIG. 3, that is, if the control voltage output from the loop filter 17 increases, the oscillation frequency from the oscillator 5 also increases. The relationship will be higher.

  In the normal operation mode, when the comparison result of the comparator 4 is fcomp <fREF (phase delay relationship of the comparison signal fcomp), the control signals input to the charge pump 18 are VCO_up = “1” and VCO_down = “0”. Therefore, the current input / output switch sets SW_fup31 = ON and SW_fdown32 = OFF, and outputs a current from the current source 30 to the smoothing circuit to increase the output potential to the oscillator 5 while charging the charge of the smoothing circuit. Thereby, the oscillation frequency from the oscillator 5 also fluctuates higher.

  Conversely, when the comparison result of the comparator 4 is fcomp> fREF (the phase advance relationship of the comparison signal fcomp), the control signals input to the charge pump 18 are VCO_up = “0” and VCO_down = “1”. The current input / output switches SW_fup31 = OFF and SW_fdown32 = ON, and the current is sucked into the current source 30 from the smoothing circuit, and the output potential to the oscillator 5 is lowered while discharging the charge of the smoothing circuit. As a result, the oscillation frequency from the oscillator 5 also fluctuates downward.

  Next, the reset mode will be described. In the reset mode, when both the channel switching signal from the control unit 7 and the reset signal are “1”, the AND logic unit output is “1”, and the current input / output switch is forcibly set to SW_fup31 = OFF and SW_fdown32 = It becomes ON. Therefore, regardless of the output of the comparator 4, current is sucked from the smoothing circuit into the current source 30, and the output potential to the oscillator 5 is lowered while discharging the charge of the smoothing circuit.

  In a generally known synthesizer, loop filter reset is a means commonly used to realize quick channel switching, in order to cause the oscillation frequency of the synthesizer to fluctuate greatly and to quickly converge to the oscillation frequency after channel switching. The residual charge stored in the loop filter is rapidly initialized to a predetermined value.

  From such a background, when changing the oscillation frequency, the conventional synthesizer resets the potential of the loop filter to a predetermined value and then changes it to a desired potential. As a result, it has been reduced that the channel switching time fluctuates greatly depending on the frequency before the channel switching. In addition, since channel switching greatly switches the frequency division ratio, it may cause malfunction of the circuit, but the problem is also reduced.

  The synthesizer of the present invention resets the loop filter when controlling the fluctuation of the oscillation frequency accompanying the temperature change of the reference oscillator 2 in FIG. 1 based on the output signal of the temperature detection unit 8 that detects the temperature of the reference oscillator 2. It is characterized by not performing. That is, the reset control unit 35 shown in FIG. 2 executes the reset mode and changes the oscillation frequency of the synthesizer only when the channel switching signal “1” (channel switching command of the receiving device) is received from the control unit 7. In other switching factors, the reset mode is not executed in switching of the oscillation frequency for correcting the continuous temperature change of the reference oscillator.

  With the above configuration, the synthesizer 1 of the present invention does not return the charge accumulated in the smoothing circuit of the loop filter 17 to a preset value when the control unit 7 controls the charge pump 18 in response to a temperature change. The oscillation frequency of the oscillator 5 can be suppressed from greatly fluctuating, and thereby the phase noise in the synthesizer 1 can be reduced. As a result, in the receiving device 50 using the oscillation signal of the synthesizer 1 as a local signal, it is possible to suppress the deterioration of the C / N (Carrier / Noise) characteristics of the received signal.

  In addition, malfunction of the circuit due to switching of the frequency division ratio can be avoided by switching the frequency division ratio before the frequency of the vibrator is greatly shifted. In particular, it is more preferable to switch the frequency division ratio at a timing at which the PLL can maintain the operating state within the lock range. Here, the lock range means that the phase difference of each input of the comparator 4 becomes 0 degree or 180 degrees, so that the frequency of the two signals does not match, but the above 0 degree, It indicates a range of cycle slip caused by determining that the phases coincide with each other at 180 degrees, that is, when the phase delay and advance are determined in reverse.

  In the case of changing the channel for switching the frequency of the received signal of the receiving device 50, the control unit 7 returns the charge accumulated in the smoothing circuit of the loop filter 17 to a preset value, and the frequency divider 6 divides the frequency. The ratio may be changed. That is, the frequency at which the control unit 7 controls the oscillation frequency in response to a channel change command from the user is much smaller than the frequency at which the frequency divider 6 is controlled to correct the oscillation frequency in response to a temperature change. Therefore, when receiving a channel change command from the user, the frequency with which the phase noise increases is also small, and since the television is not originally watched during channel switching, the phase noise is allowed to increase during this period. Is done.

  In this way, whether the charge accumulated in the smoothing circuit of the loop filter 17 is reset or not is classified according to the change factor of the oscillation frequency, thereby speeding up the channel switching operation and improving the phase noise in the temperature compensation operation. This can be realized and the total performance of the receiving apparatus can be improved.

  Further, during the period when the control unit 7 determines that the desired data is not received, the charge accumulated in the smoothing circuit of the loop filter 17 is returned to a preset value, and the frequency division ratio of the frequency divider 6 is changed. During the period when the control unit 7 determines that the desired data is received, the frequency dividing ratio of the frequency divider 6 is set without returning the charge accumulated in the smoothing circuit of the loop filter 17 to a preset value. It may be changed. The “period in which it is determined that desired data has not been received” is, for example, a guard interval period in which the receiving device 50 receives a guard signal.

  As a result, during the period in which the receiving device 50 is receiving the desired data signal, the control unit 7 does not return the charge accumulated in the smoothing circuit of the loop filter 17 to a preset value, and the frequency divider 6 Therefore, phase noise in the synthesizer can be appropriately reduced during a period in which a desired data signal is received.

  Further, in the reset mode of the present embodiment, it has been simply shown that the electric charge of the loop filter 17 is forcibly discharged. However, the present invention is not limited to discharging, and may be any purpose for resetting to a predetermined potential. In order to quickly discharge the electric charge, the current amount of the current source 30 is increased only in the reset mode, or the time constant of the loop filter is reduced. May be adopted.

  4 (a) and 4 (b) show how the oscillation frequency of the oscillator 5 changes with time when the frequency division ratio of the frequency divider 6 is changed. FIG. 4A shows the time change of the oscillation frequency of the synthesizer 1 of the present invention, and FIG. 4B shows the time change of the oscillation frequency of the conventional synthesizer.

  4A and 4B, the frequency division ratio of the frequency divider 6 is changed at time t1. After t1, a large frequency change is observed in FIG. This is because the frequency divider 6 is reset once. On the other hand, in FIG. 4A, a large frequency change is not observed after t1. This is because the frequency dividing ratio is smoothly changed because the frequency divider 6 did not reset. As a result, the synthesizer of the present invention can prevent the phase noise characteristics from being greatly deteriorated when the frequency division ratio is changed. Further, when used as a receiver, it is possible to prevent the deterioration of C / N, which is an index of reception performance.

  For reference, FIG. 5 shows a reception state of a one-segment television broadcast when the synthesizer of the present embodiment is used. 5A is a diagram when a crystal oscillator is used as a reference oscillator, and FIG. 5B is a result when a MEMS oscillator composed of a silicon resonator is used. Each shows the difference depending on the presence or absence of reset. Here, the crystal oscillator used this time does not use a TCXO (temperature-compensated crystal oscillator) or a crystal resonator whose cut angle is precisely defined, and uses a relatively inexpensively available crystal oscillator. Yes. The frequency temperature characteristic of this crystal is ± 100 ppm in the operating temperature range of −30 ° C. to 85 ° C. Although it is not an expensive crystal, it has relatively good temperature characteristics compared to other materials, so the control interval of the frequency divider 6 based on the detection result of the temperature detector 8 is more than that when a MEMS oscillator is used. Is also getting longer.

  First, FIG. 5A using quartz will be described. In the case where there is a reset, C / N, which is an index indicating the reception state, deteriorates at the reset timing after the temperature correction. Although the reset is instantaneous, the deterioration of C / N continues for a long time due to the system problem that it takes time to adjust the intermediate frequency shifted on the demodulation side. Yes. Without reset, almost good C / N performance is maintained.

  Secondly, the case where the MEMS oscillator of FIG. 5B is used will be described. Here, as described above, in the case of a silicon resonator, the frequency temperature characteristic is poor at 30 ppm / ° C., so the correction interval must be shortened, that is, the reset interval is short and frequent resets occur. . For example, in this embodiment, the correction interval is set to 50 msec. In FIG. 5B, the graph illustrating “with reset” indicates the C / N characteristic of the conventional synthesizer. In this graph, the temperature control is not started in the initial state, and the frequency is also in a relatively small fluctuation state, so that a relatively good C / N is obtained. However, immediately after that, it becomes necessary to change the frequency division ratio of the frequency divider 6 based on the detection result of the temperature detection unit 8, and once the frequency divider 6 is reset, the C / N characteristics are greatly deteriorated. I understand that. In addition, since the temperature control interval of the frequency divider 6 is as frequent as 50 msec, the next control time comes before the C / N characteristics recover, and the C / N characteristics are not good. Will end up. In such a state where the reset frequently occurs, the C / N does not recover to a good state, and the result is that the bad state is maintained. At this time, although the local frequency is set to a desired frequency, C / N deterioration is caused by frequent resetting. In a place where the reception power of the TV is high, there is a possibility that it can be received even in this state. It becomes. Note that the C / N value does not indicate a complete instantaneous value, but an average value for a certain period, so that the C / N value as in the “reset” graph of FIG. Is observed in a bad state with almost no fluctuation. This is because the aforementioned correction interval is short.

  On the other hand, the C / N characteristic of the synthesizer of the present invention is a graph of “no reset” in FIG. 5B, and almost no deterioration of the C / N characteristic is observed. From the above, it can be seen that the synthesizer of the present invention is particularly effective when a vibrator having a large frequency temperature characteristic such as a MEMS vibrator is used as a reference oscillator.

  In the case of a large frequency temperature characteristic such as a MEMS vibrator, the amount of change in the frequency division ratio of the second frequency divider can be kept small by reducing the temperature control interval. When resetting is not performed, it is possible to suppress a frequency error when changing the frequency division ratio.

  The time axis of FIG. 5A, which is an example of quartz, is the result of monitoring a shorter time width than FIG. 5B, which is an example of MEMS, in order to clearly show the deterioration of C / N. .

  Again, as can be seen from the above example, when the frequency divider 6 is controlled based on the detection result of the temperature detector 8, a large frequency change is not required as in the case of switching the reception channel. For this reason, even when the frequency divider 6 is not reset and the past cumulative addition value is held, the time until the desired frequency division ratio is reached is relatively short.

  As described above, by using the synthesizer of the present invention, it is possible to suppress C / N degradation when changing the frequency division ratio. For example, in the case of a television, continuous reception without interruption is possible. Further, even in the case of a mobile phone, it is not necessary to perform complicated control, and the system can be simplified.

  Conventionally, in the case of television channel switching, there is a grace period of several tens of msec to 1 sec to shift to the next channel, and C / N deterioration at the time of channel switching has not been a problem. This is because television reception during this grace period was unnecessary.

  In the case of a mobile phone, the signal is not always received. Therefore, it is possible to eliminate the influence on the reception characteristics due to the C / N degradation by switching the frequency division ratio in anticipation of the timing of not receiving. However, it is necessary to perform control for switching the frequency division ratio at a timing when the signal is not received. This increases the load on the system, complicates the system, and increases the manufacturing cost. By using the control method of the second frequency divider such as the synthesizer of the present invention, it is not necessary to consider the complicated control as described above.

  In this embodiment, the case where the reset is not completely performed has been described. However, if the reset process is performed during a period in which valid data, that is, data that does not directly contribute to the BER is transmitted, An effect relatively close to the effect described above can be obtained. For example, the period of a guard interval of an OFDM (Orthogonal Frequency Division Multiple) signal corresponds to this, and by performing a reset process using a part of this period, it is possible to minimize effective C / N degradation. Is possible.

  A TV reception module using the synthesizer of the present invention will be described with reference to FIG. In FIG. 6, the synthesizer of the present invention is collectively formed on the same semiconductor IC 19 including the temperature detector 8 and mounted on the base substrate 20. A MEMS vibrator 21 is used as a constituent element of the reference oscillator and is mounted on the base substrate 20. By using the MEMS vibrator 21 as a constituent element of the reference oscillator, the television receiving module can be downsized. For example, a crystal resonator requires a size of 2.5 × 2.0 mm, but a MEMS resonator can be configured with a size of 0.5 × 0.5 mm to 0.3 mm × 0.3 mm. Also, the height is less than half. In a small television receiving module mounted on a mobile phone, the size is as small as 9 × 9 mm to 8 × 8 mm, so this size effect is very large. The other components will be described. The base substrate 20 includes a first filter 24 to which a reception signal received by the antenna 23 is input, and an LNA (Low Noise Amplifier) 25 to which an output signal of the first filter 24 is input. The second filter 26 to which the output signal of the LNA 25 is input and the balun 27 to which the output signal of the second filter 26 is input are mounted. The output signal of the balun 27 is input to the semiconductor IC 19. In FIG. 6, the MEMS vibrator 21 is used. However, if it is not necessary to consider the effect of downsizing as described above, a quartz vibrator may be used, and vibration using other piezoelectric single crystals. A vibrator using a thin film such as a child, a ceramic vibrator, or an FBAR (Film Bulk Acoustic Resonator) may be used. In general, a vibration mode of a bulk wave is used for such a vibrator, but a SAW vibrator using a vibration mode of a surface acoustic wave may be used. The selection of these vibrators may be performed according to the intended use of the synthesizer of the present invention.

  An example in which the MEMS oscillator of FIG. 6 is formed in the semiconductor IC 19 is shown in FIGS. In FIG. 7, the MEMS vibrator 21 is taken into the IC. In FIG. 8, the LNA 25 described above is incorporated into the semiconductor IC 19 and the second filter 26 and the balun 27 are not required when configuring the IC.

  As described above, since the MEMS vibrator and the temperature sensor are built in the same IC chip, the temperature of the actual MEMS vibrator can be detected more accurately, and the adjustment accuracy of the oscillation frequency of the MEMS oscillator can be improved. Can be improved. For example, even when an abrupt temperature change occurs, temperature detection can be performed with almost no delay in temperature conduction, thereby preventing reception degradation. In particular, in the configuration of FIG. 8, since external components can also be formed in one semiconductor IC 19, it is possible to greatly reduce the size and improve the manufacturing efficiency.

  In the embodiment of the present invention described above, the output of the oscillator 5 is used as the output of the synthesizer 1. However, a frequency divider may be inserted after the oscillator 5 so as to be used as the output of the synthesizer 1. Thereby, the oscillation frequency of the oscillator 5 can be increased, and the size of the oscillator 5 can be reduced.

  In addition, examples of the temperature sensor referred to here include those using the temperature characteristic of the semiconductor charge transfer amount, and those using the characteristic that the resistance value changes with respect to the temperature called the thermistor. This is not a limitation. The point is that it only needs to detect the operating temperature of the vibrator constituting the reference oscillator, and the temperature may be detected indirectly without detecting the temperature directly.

The synthesizer used in the receiving apparatus of the present invention can maintain the phase noise of a synthesizer using a MEMS vibrator, for example, and therefore can be used in a receiving apparatus or an electronic apparatus having excellent reception characteristics.

DESCRIPTION OF SYMBOLS 1 Synthesizer 2 Reference oscillator 3 2nd frequency divider 4 Comparator 5 Oscillator 6 Frequency divider 7 Control part 8 Temperature detection part 9 Accumulator 14 Adder 15 Variable frequency divider 17 Loop filter 18 Charge pump 22 Synthesizer module 29 Mixer 30 Current Source 34 Reset Unit 35 Reset Control Unit 50 Receiver

Claims (8)

An oscillator that outputs an oscillation signal;
A frequency divider that divides the output signal of the oscillator based on control from a control unit;
A comparator that compares the reference oscillation signal output from the reference oscillator with the output signal from the frequency divider and outputs a signal indicating the comparison result;
A smoothing circuit that accumulates electric charges based on the comparison result output from the comparator and outputs a voltage to the oscillator;
The oscillator determines the frequency of the oscillation signal based on the voltage output from the smoothing circuit,
The control unit is a synthesizer that changes a frequency division ratio of the frequency divider based on an output signal of a temperature detection unit that detects temperature in a state where the residual charge accumulated in the smoothing circuit is held .
A receiving device comprising a mixer for converting a frequency of a received signal based on the oscillation signal from the synthesizer,
During the period when the control unit determines that the desired data has not been received, the residual charge accumulated in the smoothing circuit is initialized to a predetermined value, the frequency division ratio of the frequency divider is changed, and the control unit A receiving apparatus that changes a frequency dividing ratio of the frequency divider while retaining a residual charge accumulated in the smoothing circuit during a period when it is determined that desired data is received. A receiving device according to claim 1;
A reference oscillator composed of a vibrator composed of a MEMS element;
A receiving module in which an output signal of the reference oscillator is input to the comparator. The receiving module according to claim 2, wherein the receiving device and the vibrator are formed on the same semiconductor substrate. The receiving module according to claim 2, wherein the temperature detection unit is a temperature sensor. The receiving module according to claim 2, wherein the temperature detection unit indirectly detects a use temperature of a vibrator constituting the reference oscillator. 2. The switching unit according to claim 1, wherein when the frequency of the reception signal of the reception device is switched, the control unit initializes a residual charge accumulated in the smoothing circuit to a predetermined value and changes a frequency division ratio of the frequency divider. Receiver. The receiving apparatus according to claim 1, wherein the period during which the control unit determines that the desired data is not received is a guard interval period. A receiving device according to claim 1;
A signal processing unit connected to the output side of the mixer;
An electronic apparatus comprising: a display unit connected to an output side of the signal processing unit.

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