Oscillation device

Abstract

The present invention can reduce phase noise while characteristics of an oscillation device are addressed.　This oscillation device comprises: a field effect transistor that outputs an oscillation signal through the drain thereof; and a control unit that controls the oscillation amplitude of the oscillation signal on the basis of the source potential of the field effect transistor. The field effect transistor may operate as a negative resistor of an LC oscillator. In the case in which the field effect transistor is an N-channel field effect transistor, the control unit may control the oscillation amplitude in a direction in which the lower limit value of the oscillation amplitude approaches the source potential of the N-channel field effect transistor.

Description

Oscillator

[0001] The present technology relates to an oscillator device, and more particularly to an oscillator device capable of controlling oscillation amplitude.

[0002] Voltage-controlled oscillator circuits are known that can vary the oscillation frequency by applying an external voltage. For example, a voltage-controlled oscillator circuit has been proposed that outputs a control voltage to a bias current control circuit so that the difference between the maximum and minimum oscillation output values ​​is equal to a predetermined voltage (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2006-197571

[0004] However, in the above-mentioned conventional technology, the oscillation amplitude is controlled so as to be equal to the threshold voltage of the MOS transistor that outputs the oscillation signal, which may lead to an increase in phase noise depending on the characteristics and operating environment of the oscillator device.

[0005] This technology was developed in light of these circumstances, and aims to reduce phase noise while adapting to the characteristics of the oscillator device.

[0006] The present technology has been made to solve the above-mentioned problems, and a first aspect thereof is an oscillator device including a field-effect transistor that outputs an oscillation signal via a drain, and a control unit that controls the oscillation amplitude of the oscillation signal based on the source potential of the field-effect transistor. This provides an effect of reducing the second-order component based on the conversion of the second-order component of the fluctuation of the source potential of the transistor while outputting the oscillation signal via the drain of the field-effect transistor.

[0007] In the first aspect, the field effect transistor may operate as a negative resistance of an LC oscillator, thereby providing an effect of allowing oscillation to continue while compensating for attenuation due to parasitic resistance of the LC oscillator.

[0008] In addition, in the first aspect, when the field effect transistor is an N-channel field effect transistor, the control unit may control the oscillation amplitude in a direction such that the lower limit value of the oscillation amplitude approaches the source potential of the N-channel field effect transistor, thereby bringing about an effect that fluctuations in the source potential of the N-channel field effect transistor start abruptly.

[0009] In the first aspect, the control unit may control the oscillation amplitude so that a lower limit of the oscillation amplitude coincides with the source potential of the N-channel field-effect transistor, thereby minimizing the second-order component based on conversion of the second-order component of the fluctuation in the source potential of the N-channel field-effect transistor into a fourth-order component.

[0010] In the first aspect, the control unit may include a lower limit amplitude detection unit that detects a lower limit of the oscillation amplitude, and a comparison unit that compares the lower limit of the oscillation amplitude with the source potential of the N-channel field effect transistor, thereby providing an effect that the oscillation amplitude of the oscillation signal is controlled based on the source potential of the N-channel field effect transistor.

[0011] In a first aspect, the LC oscillator may include a first N-channel field effect transistor, a second N-channel field effect transistor cross-coupled to the first N-channel field effect transistor, a variable resistor or a variable current source having one end connected to a source of the first N-channel field effect transistor and a source of the second N-channel field effect transistor, a capacitor connected between a drain of the first N-channel field effect transistor and a drain of the second N-channel field effect transistor, and an inductor connected in parallel to the capacitor, and the control unit may control the variable resistor or the variable current source based on a comparison result by the comparison unit. This brings about an effect that the oscillation amplitude of the oscillation signal of the LC oscillator is controlled based on the source potential of the N-channel field effect transistor.

[0012] In a first aspect, the LC oscillator may include a first N-channel field effect transistor, a second N-channel field effect transistor cross-coupled to the first N-channel field effect transistor, a capacitor connected between a drain of the first N-channel field effect transistor and a drain of the second N-channel field effect transistor, an inductor connected in parallel with the capacitor, and a variable resistor or a variable current source having one end connected to a center tap of the inductor, and the control unit may control the variable resistor or the variable current source based on a comparison result by the comparison unit. This brings about an effect that the oscillation amplitude of the oscillation signal of the LC oscillator is controlled based on the source potential of the N-channel field effect transistor.

[0013] In addition, in the first aspect, when the field effect transistor is a P-channel field effect transistor, the control unit may control the oscillation amplitude in a direction such that the upper limit value of the oscillation amplitude approaches the source potential of the P-channel field effect transistor, thereby bringing about an effect that fluctuations in the source potential of the P-channel field effect transistor begin abruptly.

[0014] In the first aspect, the control unit may control the oscillation amplitude so that an upper limit of the oscillation amplitude coincides with the source potential of the P-channel field effect transistor, thereby minimizing the second-order component based on conversion of the second-order component of the fluctuation in the source potential of the P-channel field effect transistor into a fourth-order component.

[0015] In the first aspect, the control unit may include an upper limit amplitude detection unit that detects an upper limit of the oscillation amplitude, and a comparison unit that compares the upper limit of the oscillation amplitude with the source potential of the P-channel field effect transistor, thereby providing an effect that the oscillation amplitude of the oscillation signal is controlled based on the source potential of the P-channel field effect transistor.

[0016] In a first aspect, the LC oscillator may include a first P-channel field-effect transistor, a second P-channel field-effect transistor cross-coupled to the first P-channel field-effect transistor, a variable resistor or a variable current source having one end connected to a source of the first P-channel field-effect transistor and a source of the second P-channel field-effect transistor, a capacitor connected between a drain of the first P-channel field-effect transistor and a drain of the second P-channel field-effect transistor, and an inductor connected in parallel to the capacitor, and the control unit may control the variable resistor or the variable current source based on a comparison result by the comparison unit. This brings about an effect that the oscillation amplitude of the oscillation signal of the LC oscillator is controlled based on the source potential of the P-channel field-effect transistor.

[0017] In a first aspect, the LC oscillator may include a first P-channel field-effect transistor, a second P-channel field-effect transistor cross-coupled to the first P-channel field-effect transistor, a capacitor connected between the drain of the first P-channel field-effect transistor and the drain of the second P-channel field-effect transistor, an inductor connected in parallel with the capacitor, and a variable resistor or a variable current source having one end connected to a center tap of the inductor, and the control unit may control the variable resistor or the variable current source based on a comparison result by the comparison unit, thereby providing an effect that the oscillation amplitude of the oscillation signal of the LC oscillator is controlled based on the source potential of the P-channel field-effect transistor.

[0018] In the first aspect, the LC oscillator may further include a storage unit that stores a set value of the oscillation amplitude, and the control unit may control the oscillation amplitude of the oscillation signal based on the set value stored in the storage unit. This provides the effect of controlling the oscillation amplitude of the oscillation signal of the LC oscillator without requiring feedback control.

[0019] In the first aspect, the control unit may calibrate the oscillation amplitude based on a comparison result between the oscillation amplitude of the oscillation signal when the oscillation amplitude of the oscillation signal is controlled based on the set value of the oscillation amplitude and the source potential of the field-effect transistor, thereby optimizing the oscillation amplitude of the oscillation signal in accordance with the characteristics and operating environment of the oscillator device.

[0020] FIG. 1 is a diagram showing an example of the configuration of an oscillator device according to a first embodiment; FIG. 2 is a diagram showing an example of conversion from a second-order component to a fourth-order component of fluctuations in source potential of the oscillator device according to the first embodiment; FIG. 3 is a diagram showing an example of the relationship between amplitude and phase noise of the oscillator device according to the first embodiment; FIG. 4 is a diagram showing another example of the configuration of the oscillator device according to the first embodiment; FIG. 5 is a diagram showing yet another example of the configuration of the oscillator device according to the first embodiment; FIG. 6 is a diagram showing an example of the configuration of an amplitude lower limit value detection unit and a comparison unit according to the first embodiment; FIG. 7 is a diagram showing an example of the configuration of an oscillator device according to a second embodiment; FIG. 8 is a diagram showing an example of the configuration of an oscillator device according to a third embodiment; FIG. 9 is a diagram showing another example of the configuration of an oscillator device according to the third embodiment; FIG. 10 is a diagram showing an example of the configuration of an oscillator device according to a fourth embodiment; FIG. 11 is a diagram showing an example of the configuration of an oscillator device according to a fifth embodiment.

[0021] Hereinafter, modes for implementing the present technology (hereinafter referred to as embodiments) will be described. The description will be made in the following order: 1. First embodiment (an example of controlling the oscillation amplitude so that the lower limit of the oscillation amplitude coincides with the source potential of an N-channel field effect transistor that outputs an oscillation signal via the drain) 2. Second embodiment (an example of controlling the oscillation amplitude so that the upper limit of the oscillation amplitude coincides with the source potential of a P-channel field effect transistor that outputs an oscillation signal via the drain) 3. Third embodiment (an example of controlling the oscillation amplitude of an oscillation signal based on the source potential when an LC oscillator is configured using an N-channel field effect transistor and a P-channel field effect transistor) 4. Fourth embodiment (an example of controlling the oscillation amplitude so that the upper limit of the oscillation amplitude coincides with an adjusted value of the source potential of an N-channel field effect transistor that outputs an oscillation signal via the drain) 5. Fifth embodiment (an example of calibrating the oscillation amplitude based on a comparison result between the source potential of an N-channel field effect transistor that outputs an oscillation signal via the drain and the lower limit of the oscillation amplitude)

[0022] 1. First Embodiment FIG. 1 is a diagram showing an example of the configuration of an oscillation device according to a first embodiment.

[0023] In the figure, the oscillation device includes an LC oscillator 101 and a control unit 102. The control unit 102 is connected downstream of the LC oscillator 101 and is capable of feedback-controlling the LC oscillator 101. The LC oscillator 101 generates oscillation signals POS and NOS based on the resonant operation of a capacitor 131 and an inductor 141. The oscillation signals POS and NOS are differential output signals. The LC oscillator 101 includes N-channel field-effect transistors 111 and 121, a capacitor 131, an inductor 141, a variable resistor 151, and a resistor 161. Note that the resistor 161 is not necessary.

[0024] The N-channel field effect transistors 111 and 121 are cross-coupled to each other. The N-channel field effect transistors 111 and 121 can operate as negative resistance of the LC oscillator 101. In this case, the gate terminal of the N-channel field effect transistor 111 is connected to the drain of the N-channel field effect transistor 121. The gate terminal of the N-channel field effect transistor 121 is connected to the drain of the N-channel field effect transistor 111.

[0025] The sources of the N-channel field effect transistors 111 and 121 are connected to the ground potential via a variable resistor 151. An oscillation signal POS is output from the drain of the N-channel field effect transistor 111. An oscillation signal NOS is output from the drain of the N-channel field effect transistor 121. A capacitor 131 is connected between the drains of the N-channel field effect transistors 111 and 121. The capacitor 131 and an inductor 141 are connected in parallel with each other. A center tap of the inductor 141 is connected to the power supply potential via a resistor 161.

[0026] The control unit 102 controls the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 101 based on the source potential VSN of the N-channel field-effect transistors 111 and 121. At this time, the control unit 102 can control the oscillation amplitude in a direction such that the lower limit value LM of the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 101 approaches the source potential VSN of the N-channel field-effect transistors 111 and 121. For example, the control unit 102 may control the oscillation amplitude so that the lower limit value LM of the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 101 coincides with the source potential VSN of the N-channel field-effect transistors 111 and 121. The control unit 102 includes an amplitude lower limit detection unit 112 and a comparison unit 122.

[0027] The amplitude lower limit detector 112 detects the lower limit LM of the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 101 and outputs it to the comparator 122 .

[0028] The comparator 122 compares the lower limit LM of the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 101 with the source potential VSN of the N-channel field-effect transistors 111 and 121. The comparator 122 then controls the variable resistor 151 so that the lower limit LM of the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 101 approaches the source potential VSN of the N-channel field-effect transistors 111 and 121. For example, the comparator 122 may control the variable resistor 151 so that the lower limit LM of the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 101 matches the source potential VSN of the N-channel field-effect transistors 111 and 121. At this time, the source-drain voltage Vds of each N-channel field-effect transistor 111 and 121 becomes 0 V.

[0029] Here, it is assumed that the lower limit value LM of the oscillation amplitude of the oscillation signals POS and NOS approaches the source potential VSN of the N-channel field-effect transistors 111 and 121 based on the control of the variable resistor 151. At this time, the source potential VSN of the N-channel field-effect transistors 111 and 121 begins to fluctuate abruptly, and the second-order component of the fluctuation of the source potential VSN of the N-channel field-effect transistors 111 and 121 is converted into a fourth-order component. Then, the second-order component of the fluctuation of the source potential VSN is reduced based on the conversion from the second-order component to the fourth-order component. Here, the second-order component of the fluctuation of the source potential VSN is down-converted to phase noise. Therefore, by reducing the second-order component of the fluctuation of the source potential VSN, the phase noise of the LC oscillator 101 can be reduced. At this time, by matching the lower limit value LM of the oscillation amplitude of the oscillation signals POS and NOS with the source potential VSN of the N-channel field effect transistors 111 and 121, the second-order component of the fluctuation of the source potential VSN of the N-channel field effect transistors 111 and 121 can be minimized.

[0030] FIG. 2 is a diagram showing an example of conversion from a second-order component to a fourth-order component of the fluctuation in the source potential of the oscillator device according to the first embodiment.

[0031] In the figure, it is assumed that the lower limit LM of the oscillation amplitude of the oscillation signals POS and NOS is far from the source potential VSN of the N-channel field-effect transistors 111 and 121. At this time, fluctuations in the source potential VSN caused by the lower limit LM of the oscillation amplitude of the oscillation signals POS and NOS are suppressed. On the other hand, even if the lower limit LM of the oscillation amplitude of the oscillation signals POS and NOS is far from the source potential VSN of the N-channel field-effect transistors 111 and 121, fluctuations in the source potential VSN caused by the balanced state of the oscillation signals POS and NOS still occur. Therefore, the fluctuations in the source potential VSN are dominated by second-order components.

[0032] In FIG. 1B, it is assumed that the lower limit LM of the oscillation amplitude of the oscillation signals POS and NOS is equal to the source potential VSN of the N-channel field-effect transistors 111 and 121. At this time, fluctuations in the source potential VSN occur due to the lower limit LM of the oscillation amplitude of the oscillation signals POS and NOS. Furthermore, even if the lower limit LM of the oscillation amplitude of the oscillation signals POS and NOS is equal to the source potential VSN of the N-channel field-effect transistors 111 and 121, fluctuations in the source potential VSN occur due to the balanced state of the oscillation signals POS and NOS. Therefore, the second-order component of the fluctuation in the source potential VSN is converted into a fourth-order component, and the second-order component of the fluctuation in the source potential VSN is reduced.

[0033] 3 is a diagram showing an example of the relationship between amplitude and phase noise in the oscillation device according to the first embodiment, where "a" in the diagram shows an example of the relationship between amplitude and phase noise when the Q of the LC oscillator 101 is high, and "b" in the diagram shows an example of the relationship between amplitude and phase noise when the Q of the LC oscillator 101 is low.

[0034] In FIG. 10A, when the Q of the LC oscillator 101 is high, the phase noise can be minimized by setting the oscillation amplitude of the oscillation signals POS and NOS to point P1, which coincides with the threshold voltage Vth of the N-channel field-effect transistors 111 and 121.

[0035] In the diagram (b), when the Q of the LC oscillator 101 is low, phase noise can be minimized by setting the oscillation amplitude to point P2, where the lower limit LM of the oscillation amplitude of the oscillation signals POS and NOS coincides with the source potential VSN of the N-channel field-effect transistors 111 and 121. If the oscillation amplitude of the oscillation signals POS and NOS decreases from point P2, the second-order component of the fluctuation in the source potential VSN increases, causing a sudden increase in phase noise. Therefore, when the Q of the LC oscillator 101 is low, setting the oscillation amplitude of the oscillation signals POS and NOS to point P3, where the threshold voltage Vth of the N-channel field-effect transistors 111 and 121 coincides with the phase noise.

[0036] FIG. 4 is a diagram showing another example of the configuration of the oscillation device according to the first embodiment.

[0037] In the figure, this oscillator device includes an LC oscillator 103 instead of the LC oscillator 101 in Fig. 1. Other configurations of this oscillator device are the same as those of the oscillator device in Fig. 1.

[0038] The LC oscillator 103 includes a variable current source 153 and a current source 163 instead of the variable resistor 151 and resistor 161 in Fig. 1. Other configurations of the LC oscillator 103 are the same as those of the LC oscillator 101 in Fig. 1. Note that the current source 163 may be omitted.

[0039] The sources of the N-channel field effect transistors 111 and 121 are connected to the ground potential via a variable current source 153. The center tap of the inductor 141 is connected to the power supply potential via a current source 163.

[0040] Here, the comparison unit 122 controls the variable current source 153 so that the lower limit value LM of the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 103 approaches the source potential VSN of the N-channel field effect transistors 111 and 121. For example, the comparison unit 122 may control the variable current source 153 so that the lower limit value LM of the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 103 matches the source potential VSN of the N-channel field effect transistors 111 and 121.

[0041] FIG. 5 is a diagram showing yet another example of the configuration of the oscillation device according to the first embodiment.

[0042] In the figure, this oscillator device includes an LC oscillator 104 instead of the LC oscillator 101 in Fig. 1. Other configurations of this oscillator device are the same as those of the oscillator device in Fig. 1.

[0043] 1. The LC oscillator 104 includes a resistor 154 and a variable resistor 164 instead of the variable resistor 151 and the resistor 161 in FIG. 1. The rest of the configuration of the LC oscillator 104 is the same as the configuration of the LC oscillator 101 in FIG.

[0044] The sources of the N-channel field effect transistors 111 and 121 are connected to the ground potential via a resistor 154. The center tap of the inductor 141 is connected to the power supply potential via a variable resistor 164. The resistor 154 may be omitted.

[0045] Here, the comparison unit 122 controls the variable resistor 164 so that the lower limit value LM of the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 104 approaches the source potential VSN of the N-channel field effect transistors 111 and 121. For example, the comparison unit 122 may control the variable resistor 164 so that the lower limit value LM of the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 104 matches the source potential VSN of the N-channel field effect transistors 111 and 121.

[0046] FIG. 6 is a diagram showing yet another example of the configuration of the oscillation device according to the first embodiment.

[0047] In the figure, this oscillator device includes an LC oscillator 105 instead of the LC oscillator 101 in Fig. 1. Other configurations of this oscillator device are the same as those of the oscillator device in Fig. 1.

[0048] The LC oscillator 105 includes a current source 155 and a variable current source 165 instead of the variable resistor 151 and resistor 161 in Fig. 1. Other configurations of the LC oscillator 105 are the same as those of the LC oscillator 101 in Fig. 1. The current source 155 may be omitted.

[0049] The sources of the N-channel field effect transistors 111 and 121 are connected to the ground potential via a current source 155. The center tap of the inductor 141 is connected to the power supply potential via a variable current source 165.

[0050] Here, the comparison unit 122 controls the variable current source 165 so that the lower limit value LM of the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 105 approaches the source potential VSN of the N-channel field effect transistors 111 and 121. For example, the comparison unit 122 may control the variable current source 165 so that the lower limit value LM of the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 105 matches the source potential VSN of the N-channel field effect transistors 111 and 121.

[0051] FIG. 7 is a diagram illustrating an example of the configuration of the amplitude lower limit detector and the comparator according to the first embodiment.

[0052] 1, the LC oscillator 106 includes a variable capacitance 171 and an N-channel field effect transistor 172 instead of the capacitor 131 and the variable resistor 151 in FIG. The rest of the configuration of the LC oscillator 106 is the same as the configuration of the LC oscillator 101 in FIG.

[0053] The variable capacitor 171 is connected in parallel to the inductor 141. The sources of the N-channel field effect transistors 111 and 121 are connected to the ground potential VSS via an N-channel field effect transistor 172. The gate of the N-channel field effect transistor 172 is connected to the output of the comparator 191.

[0054] The amplitude lower limit detection unit 112 includes current sources 181 and 182 and P-channel field effect transistors 183 to 185. The sources of the P-channel field effect transistors 183 and 184 are connected to the power supply potential VDD via the current source 181. The sources of the P-channel field effect transistors 183 and 184 are connected to the non-inverting input terminal of a comparator 191. The drains of the P-channel field effect transistors 183 and 184 are connected to the ground potential VSS. The gate of the P-channel field effect transistor 183 receives an oscillation signal POS from the LC oscillator 106. The gate of the P-channel field effect transistor 184 receives an oscillation signal NOS from the LC oscillator 106. The source of the P-channel field effect transistor 185 is connected to the power supply potential VDD via the current source 182. The source of the P-channel field effect transistor 185 is connected to the inverting input terminal of the comparator 191. The drain of the P-channel field effect transistor 185 is connected to the ground potential VSS. The source potential VSN of the N-channel field effect transistors 111 and 121 is input to the gate of the P-channel field effect transistor 185.

[0055] Here, the P-channel field-effect transistors 183 and 184 can generate an output to the comparison unit 122 based on a source follower operation that is based on a differential input. Therefore, the output to the comparison unit 122 is rate-limited by the low amplitude of the oscillation signals POS and NOS, and the amplitude lower limit detection unit 112 can detect the lower limit LM of the oscillation amplitude of the oscillation signals POS and NOS. The P-channel field-effect transistor 185 can output the source potential VSN of the N-channel field-effect transistors 111 and 121 to the comparison unit 122 based on a source follower operation.

[0056] The comparison unit 122 includes a comparator 191. The comparator 191 compares the lower limit value LM of the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 106 with the source potential VSN of the N-channel field effect transistors 111 and 121, and controls the gate voltage of the N-channel field effect transistor 172 based on the comparison result.

[0057] Although Figure 7 shows an example of the configuration of the amplitude lower limit value detection unit 112 and the comparison unit 122, the amplitude lower limit value detection unit 112 and the comparison unit 122 are not necessarily limited to the configuration shown in Figure 7 and may have other configurations.

[0058] In this way, in the first embodiment described above, the oscillation amplitude is controlled so that the lower limit value LM of the oscillation amplitude of the oscillation signals POS and NOS coincides with the source potential VSN of the N-channel field effect transistors 111 and 121. This makes it possible to reduce the second-order component based on the conversion of the fluctuation in the source potential VSN of the N-channel field effect transistors 111 and 121 from a second-order component to a fourth-order component, thereby reducing the phase noise of the LC oscillator.

[0059] 2. Second Embodiment In the first embodiment described above, the oscillation amplitude is controlled so that the lower limit LM of the oscillation amplitude of the oscillation signals POS and NOS coincides with the source potential VSN of the N-channel field effect transistors 111 and 121. In this second embodiment, the oscillation amplitude is controlled so that the upper limit of the oscillation amplitude coincides with the source potential of the P-channel field effect transistor that outputs the oscillation signals POS and NOS via the drain.

[0060] FIG. 8 is a diagram illustrating an example of the configuration of an oscillation device according to the second embodiment.

[0061] In the figure, this oscillation device includes an LC oscillator 201 and a control unit 202. The control unit 202 is connected to the rear stage of the LC oscillator 201 and is capable of feedback controlling the LC oscillator 201. The LC oscillator 201 includes P-channel field effect transistors 211 and 212 instead of the N-channel field effect transistors 111 and 121 of the LC oscillator 101 in FIG.

[0062] The P-channel field effect transistors 211 and 212 are cross-coupled to each other. At this time, the gate terminal of the P-channel field effect transistor 211 is connected to the drain of the P-channel field effect transistor 212. The gate terminal of the P-channel field effect transistor 212 is connected to the drain of the P-channel field effect transistor 211.

[0063] The sources of the P-channel field effect transistors 211 and 212 are connected to a power supply potential via a resistor 161. An oscillation signal POS is output from the drain of the P-channel field effect transistor 211. An oscillation signal NOS is output from the drain of the P-channel field effect transistor 212. A capacitor 131 is connected between the drains of the P-channel field effect transistors 211 and 212. The center tap of the inductor 141 is connected to a ground potential via a variable resistor 151.

[0064] The control unit 202 controls the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 201 based on the source potential VSP of the P-channel field-effect transistors 211 and 212. At this time, the control unit 202 can control the oscillation amplitude in a direction such that the upper limit value UM of the oscillation amplitude of the oscillation signals POS and NOS approaches the source potential VSP of the P-channel field-effect transistors 211 and 212. For example, the control unit 202 may control the oscillation amplitude so that the upper limit value UM of the oscillation amplitude of the oscillation signals POS and NOS coincides with the source potential VSP of the P-channel field-effect transistors 211 and 212. The control unit 202 includes an amplitude upper limit detection unit 212 and a comparison unit 222.

[0065] The amplitude upper limit detector 212 detects the upper limit UM of the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 201 and outputs it to the comparator 222 .

[0066] The comparison unit 222 compares the upper limit value UM of the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 201 with the source potential VSP of the P-channel field effect transistors 211 and 212. The comparison unit 222 then controls the variable resistor 151 so that the upper limit value UM of the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 201 approaches the source potential VSP of the P-channel field effect transistors 211 and 212. For example, the comparison unit 222 may control the variable resistor 151 so that the upper limit value UM of the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 201 matches the source potential VSP of the P-channel field effect transistors 211 and 212.

[0067] In this way, in the second embodiment described above, the oscillation amplitude is controlled so that the upper limit value UM of the oscillation amplitude of the oscillation signals POS and NOS coincides with the source potential VSP of the P-channel field effect transistors 211 and 212. This makes it possible to reduce the second-order component based on the conversion of the fluctuation in the source potential VSP of the P-channel field effect transistors 211 and 212 from a second-order component to a fourth-order component, thereby reducing the phase noise of the LC oscillator 201.

[0068] In the second embodiment described above, an example was shown in which oscillation amplitude control was applied to the LC oscillator 201 in which P-channel field-effect transistors 211 and 212 were provided instead of the N-channel field-effect transistors 111 and 121 of the LC oscillator 101 in FIG. 1 . Alternatively, oscillation amplitude control may be applied to an LC oscillator in which P-channel field-effect transistors 211 and 212 were provided instead of the N-channel field-effect transistors 111 and 121 of the LC oscillator 103 in FIG. 4 . Alternatively, oscillation amplitude control may be applied to an LC oscillator in which P-channel field-effect transistors 211 and 212 were provided instead of the N-channel field-effect transistors 111 and 121 of the LC oscillator 104 in FIG. 5 . Alternatively, oscillation amplitude control may be applied to an LC oscillator in which P-channel field-effect transistors 211 and 212 were provided instead of the N-channel field-effect transistors 111 and 121 of the LC oscillator 105 in FIG. 6 .

[0069] 3. Third Embodiment In the first embodiment described above, the oscillation amplitude is controlled so that the lower limit value LM of the oscillation amplitude of the oscillation signals POS and NOS coincides with the source potential VSN of the N-channel field effect transistors 111 and 121. In this third embodiment, the oscillation amplitude of the oscillation signals POS and NOS is controlled based on the source potential when an LC oscillator is configured using the N-channel field effect transistors 111 and 121 and the P-channel field effect transistors 211 and 212.

[0070] FIG. 9 is a diagram illustrating an example of the configuration of an oscillation device according to the third embodiment.

[0071] In the figure, this oscillation device includes an LC oscillator 301 and a control unit 102. The control unit 102 is connected to the rear stage of the LC oscillator 301 and is capable of feedback controlling the LC oscillator 301. The LC oscillator 301 includes N-channel field effect transistors 111 and 121, P-channel field effect transistors 211 and 212, a capacitor 131, an inductor 141, a resistor 154, and a variable current source 165.

[0072] The N-channel field effect transistor 111 and the P-channel field effect transistor 211 are connected in series. The N-channel field effect transistor 121 and the P-channel field effect transistor 212 are connected in series. A capacitor 131 is connected between the drains of the N-channel field effect transistors 111 and 121. The gate terminal of the N-channel field effect transistor 111 is connected to the drain of the N-channel field effect transistor 121. The gate terminal of the N-channel field effect transistor 121 is connected to the drain of the N-channel field effect transistor 111. The sources of the N-channel field effect transistors 111 and 121 are connected to ground potential via a resistor 154. An oscillation signal POS is output from the drain of the N-channel field effect transistor 111. An oscillation signal NOS is output from the drain of the N-channel field effect transistor 121. The gate terminal of the P-channel field effect transistor 211 is connected to the drain of the P-channel field effect transistor 212. The gate terminal of the P-channel field effect transistor 212 is connected to the drain of the P-channel field effect transistor 211. The source of each of the P-channel field effect transistors 211 and 212 is connected to the power supply potential via a variable current source 165 .

[0073] Here, the comparison unit 122 controls the variable current source 165 so that the lower limit value LM of the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 301 approaches the source potential VSN of the N-channel field effect transistors 111 and 121. For example, the comparison unit 122 may control the variable current source 165 so that the lower limit value LM of the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 301 matches the source potential VSN of the N-channel field effect transistors 111 and 121.

[0074] FIG. 10 is a diagram showing another example of the configuration of the oscillation device according to the third embodiment.

[0075] In the figure, the oscillation device includes an LC oscillator 301 and a control unit 202. The control unit 202 is connected to the rear stage of the LC oscillator 301 and is capable of feedback controlling the LC oscillator 301.

[0076] Here, the comparison unit 222 controls the variable current source 165 so that the upper limit value UM of the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 301 approaches the source potential VSP of the P-channel field effect transistors 211 and 212. For example, the comparison unit 222 may control the variable current source 165 so that the upper limit value UM of the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 301 matches the source potential VSP of the P-channel field effect transistors 211 and 212.

[0077] As described above, in the third embodiment, the oscillation amplitude of the oscillation signals POS and NOS is controlled based on the source potential when the LC oscillator 301 is configured using the N-channel field effect transistors 111 and 121 and the P-channel field effect transistors 211 and 212. This makes it possible to reduce the second-order component based on the conversion from the second-order component of the fluctuation in the source potential VSN of the N-channel field effect transistors 111 and 121 or the fluctuation in the source potential VSP of the P-channel field effect transistors 211 and 212 to a fourth-order component, thereby reducing the phase noise of the LC oscillator 301.

[0078] In the third embodiment described above, an example has been shown in which variable current source 165 is controlled to control the oscillation amplitude of LC oscillator 301. Alternatively, a variable resistor may be provided instead of variable current source 165, and the oscillation amplitude of the LC oscillator may be controlled based on control of the variable resistor. Alternatively, instead of resistor 154 connected to the ground potential, a variable resistor or variable current source connected to the ground potential may be provided, and the oscillation amplitude of the LC oscillator may be controlled based on control of the variable resistor or variable current source connected to the ground potential.

[0079] 4. Fourth Embodiment In the first embodiment described above, the oscillation amplitude is controlled so that the lower limit LM of the oscillation amplitude of the oscillation signals POS and NOS matches the source potential VSN of the N-channel field effect transistors 111 and 121. In this fourth embodiment, the oscillation amplitude is controlled so that the lower limit LM of the oscillation amplitude of the oscillation signals POS and NOS matches the adjusted value of the source potential VSN of the N-channel field effect transistors 111 and 121.

[0080] FIG. 11 is a diagram illustrating an example of the configuration of an oscillation device according to the fourth embodiment.

[0081] In the figure, the oscillation device includes an LC oscillator 101 and a control unit 302. The control unit 302 is connected to the rear stage of the LC oscillator 101 and is capable of feedback controlling the LC oscillator 101.

[0082] The control unit 302 is the same as the control unit 102 of the first embodiment described above, except that an adjustment unit 312 is added. The other configuration of the control unit 302 is the same as the configuration of the control unit 102 of the first embodiment described above.

[0083] The adjustment unit 312 adjusts the value of the source potential VSN of the N-channel field effect transistors 111 and 121 and outputs it to the comparison unit 122. For example, the adjustment unit 312 may shift the value of the source potential VSN by α and output it to the comparison unit 122. In this case, the comparison unit 122 can control the variable resistor 151 so that the lower limit LM of the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 101 approaches the source potential VSN of the N-channel field effect transistors 111 and 121, even if it does not completely match the source potential VSN of the N-channel field effect transistors 111 and 121.

[0084] In this way, in the fourth embodiment described above, the oscillation amplitude is controlled so that the lower limit value LM of the oscillation amplitude of the oscillation signals POS and NOS coincides with the adjusted value of the source potential VSN of the N-channel field effect transistors 111 and 121. This makes it possible to reduce the phase noise of the LC oscillator 101 while expanding the control range of the oscillation amplitude of the LC oscillator 101.

[0085] In the above-described fourth embodiment, an example has been shown in which the control of oscillation amplitude based on the adjustment value of the source potential VSN is applied to the LC oscillator 101 of Fig. 1. In addition to this, the control of oscillation amplitude based on the adjustment value of the source potential VSN may be applied to the LC oscillator 103 of Fig. 4, the LC oscillator 104 of Fig. 5, or the LC oscillator 105 of Fig. 6. Alternatively, the control of oscillation amplitude based on the adjustment value of the source potential VSN may be applied to the LC oscillator 201 of Fig. 8 or the LC oscillator 301 of Fig. 9.

[0086] 5. Fifth Embodiment In the first embodiment described above, the oscillation amplitude is controlled so that the lower limit value LM of the oscillation amplitude of the oscillation signals POS and NOS coincides with the source potential VSN of the N-channel field effect transistors 111 and 121. In this fifth embodiment, the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 101 is calibrated based on the comparison result between the source potential VSN of the N-channel field effect transistors 111 and 121 and the lower limit value LM of the oscillation amplitude.

[0087] FIG. 12 is a diagram illustrating an example of the configuration of an oscillation device according to the fifth embodiment.

[0088] In the figure, the oscillation device includes an LC oscillator 101 and a control unit 502. The control unit 502 is connected to the subsequent stage of the LC oscillator 101 and can specify the amplitude of the LC oscillator 101.

[0089] The control unit 502 controls the oscillation amplitude of the oscillation signals POS and NOS based on the set value stored in the register 542. Here, the control unit 502 calibrates the oscillation amplitude based on the result of comparing the source potential VSN of the N-channel field effect transistors 111 and 121 with the lower limit LM of the oscillation amplitude when the oscillation amplitude is controlled based on the set value of the oscillation amplitude of the oscillation signals POS and NOS. The control unit 502 includes an amplitude lower limit detection unit 112, a comparison unit 522, a calibrator 532, and a register 542.

[0090] The comparator 522 compares the lower limit value LM of the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 101 with the source potential VSN of the N-channel field effect transistors 111 and 121 , and outputs the comparison result to the calibrator 532 .

[0091] The calibrator 532 sweeps the oscillation amplitude setting value stored in the register 542 and selects the oscillation amplitude setting value VN of the oscillation signals POS and NOS of the LC oscillator 101 based on the comparison result by the comparator 522 at that time. Then, when the calibrator 532 selects the oscillation amplitude setting value VN of the oscillation signals POS and NOS of the LC oscillator 101, it can stop the operation of the amplitude lower limit detector 112 and the comparator 522. The calibrator 532 can perform calibration when the LC oscillator 101 is started up or in response to temperature changes in the operating environment. At this time, the calibrator 532 may start calibration based on a start signal AK.

[0092] The register 542 stores a set value for the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 101. The register 542 can store multiple set values. The register 542 controls the variable resistor 151 based on the set value VN of the oscillation amplitude specified by the calibrator 532. The register 542 is an example of a storage unit described in the claims. Here, the method of controlling the variable resistor 151 based on the set value VN stored in the register 542 can eliminate the need for feedback control via the amplitude lower limit detection unit 112 and the comparison unit 522. Therefore, the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 101 can be controlled without requiring phase compensation of the feedback loop.

[0093] As described above, in the fifth embodiment, the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 101 is calibrated based on the comparison result between the source potential VSN of the N-channel field effect transistors 111 and 121 and the lower limit LM of the oscillation amplitude. This makes it possible to fix the set value VN used to control the oscillation amplitude of the oscillation signals POS and NOS of the LC oscillator 101, and also to reduce phase noise while responding to temperature changes in the startup of the LC oscillator 101 and the environment in which it is used.

[0094] In the above-described fifth embodiment, an example has been shown in which the calibration of the oscillation amplitude is applied to the LC oscillator 101 of Fig. 1. In addition to this, the calibration of the oscillation amplitude may be applied to the LC oscillator 103 of Fig. 4, the LC oscillator 104 of Fig. 5, or the LC oscillator 105 of Fig. 6. Alternatively, the calibration of the oscillation amplitude may be applied to the LC oscillator 201 of Fig. 8, or the LC oscillator 301 of Fig. 9.

[0095] Note that the above-described embodiment shows an example for realizing the present technology, and the matters in the embodiment and the matters specifying the invention in the claims correspond to each other. Similarly, the matters specifying the invention in the claims and the matters in the embodiment of the present technology with the same title correspond to each other. However, the present technology is not limited to the embodiment, and can be realized by applying various modifications to the embodiment within the scope of the gist. Furthermore, the effects described in this specification are merely examples and are not limited, and other effects may also be present.

[0096] The present technology may also be configured as follows: (1) An oscillator device comprising: a field-effect transistor that outputs an oscillation signal via a drain; and a control unit that controls the oscillation amplitude of the oscillation signal based on the source potential of the field-effect transistor. (2) The oscillator device according to (1), wherein the field-effect transistor operates as a negative resistance of an LC oscillator. (3) The oscillator device according to (1) or (2), wherein, when the field-effect transistor is an N-channel field-effect transistor, the control unit controls the oscillation amplitude such that the lower limit of the oscillation amplitude approaches the source potential of the N-channel field-effect transistor. (4) The oscillator device according to any of (1) to (3), wherein the control unit controls the oscillation amplitude so that the lower limit of the oscillation amplitude coincides with the source potential of the N-channel field-effect transistor. (5) The oscillator device according to (3) or (4), wherein the control unit comprises: an amplitude lower-limit detection unit that detects the lower limit of the oscillation amplitude; and a comparison unit that compares the lower limit of the oscillation amplitude with the source potential of the N-channel field-effect transistor. (6) The oscillation device according to (5), wherein the LC oscillator includes: a first N-channel field effect transistor; a second N-channel field effect transistor cross-coupled to the first N-channel field effect transistor; a variable resistor or a variable current source having one end connected to a source of the first N-channel field effect transistor and a source of the second N-channel field effect transistor; a capacitor connected between the drain of the first N-channel field effect transistor and the drain of the second N-channel field effect transistor; and an inductor connected in parallel to the capacitor; and the control unit controls the variable resistor or the variable current source based on a comparison result by the comparison unit.(7) The oscillation device according to (5), wherein the LC oscillator comprises: a first N-channel field effect transistor; a second N-channel field effect transistor cross-coupled to the first N-channel field effect transistor; a capacitor connected between a drain of the first N-channel field effect transistor and a drain of the second N-channel field effect transistor; an inductor connected in parallel to the capacitor; and a variable resistor or a variable current source having one end connected to a center tap of the inductor, wherein the control unit controls the variable resistor or the variable current source based on a comparison result by the comparison unit. (8) The oscillation device according to (1) or (2), wherein, when the field effect transistor is a P-channel field effect transistor, the control unit controls the oscillation amplitude in a direction such that an upper limit value of the oscillation amplitude approaches the source potential of the P-channel field effect transistor. (9) The oscillation device according to any of (1) to (3), wherein the control unit controls the oscillation amplitude so that the upper limit value of the oscillation amplitude coincides with the source potential of the P-channel field effect transistor. (10) The oscillator device according to (8) or (9), wherein the control unit comprises: an amplitude upper limit detection unit that detects an upper limit of the oscillation amplitude; and a comparison unit that compares the upper limit of the oscillation amplitude with the source potential of the P-channel field effect transistor. (11) The oscillator device according to (10), wherein the LC oscillator comprises: a first P-channel field effect transistor, a second P-channel field effect transistor cross-coupled to the first P-channel field effect transistor, a variable resistor or a variable current source having one end connected to a source of the first P-channel field effect transistor and a source of the second P-channel field effect transistor, a capacitor connected between the drain of the first P-channel field effect transistor and the drain of the second P-channel field effect transistor, and an inductor connected in parallel with the capacitor.(12) The oscillation device according to (10), wherein the LC oscillator comprises: a first P-channel field effect transistor; a second P-channel field effect transistor cross-coupled to the first P-channel field effect transistor; a capacitor connected between a drain of the first P-channel field effect transistor and a drain of the second P-channel field effect transistor; an inductor connected in parallel to the capacitor; and a variable resistor or a variable current source having one end connected to a center tap of the inductor, wherein the control unit controls the variable resistor or the variable current source based on a comparison result by the comparison unit. (13) The oscillation device according to any one of (1) to (12), further comprising: a memory unit that stores a set value of the oscillation amplitude, wherein the control unit controls the oscillation amplitude of the oscillation signal based on the set value stored in the memory unit. (14) The oscillation device according to (13), wherein the control unit calibrates the oscillation amplitude based on a comparison result between the oscillation amplitude of the oscillation signal when the oscillation amplitude of the oscillation signal is controlled based on the set value of the oscillation amplitude and a source potential of the field effect transistor.

[0097] REFERENCE SIGNS LIST 101 LC oscillator 111, 121 N-channel field effect transistor 131 Capacitor 141 Inductor 151 Variable resistor 161 Resistor 102 Control unit 112 Amplitude lower limit detection unit 122 Comparison unit

Claims

1. An oscillation device comprising a field effect transistor that outputs an oscillation signal via a drain, and a control unit that controls an oscillation amplitude of the oscillation signal based on a source potential of the field effect transistor.

2. The oscillation device according to claim 1, wherein the field effect transistor operates as a negative resistance of an LC oscillator.

3. The oscillation device according to claim 2, wherein the control unit controls the oscillation amplitude in a direction in which a lower limit value of the oscillation amplitude approaches the source potential of the N-channel field effect transistor when the field effect transistor is an N-channel field effect transistor.

4. The oscillation device according to claim 2, wherein the control unit controls the oscillation amplitude such that the lower limit value of the oscillation amplitude coincides with the source potential of the N-channel field effect transistor.

5. The oscillation device according to claim 3, wherein the control unit includes an amplitude lower limit value detection unit that detects a lower limit value of the oscillation amplitude, and a comparison unit that compares the lower limit value of the oscillation amplitude with the source potential of the N-channel field effect transistor.

6. The LC oscillator includes a first N-channel field effect transistor, a second N-channel field effect transistor cross-coupled to the first N-channel field effect transistor, a variable resistor or a variable current source having one end connected to the source of the first N-channel field effect transistor and the source of the second N-channel field effect transistor, a capacitor connected between the drain of the first N-channel field effect transistor and the drain of the second N-channel field effect transistor, and an inductor connected in parallel with the capacitor. The control unit controls the variable resistor or the variable current source based on a comparison result by the comparison unit. The oscillation device according to claim 5.

7. The LC oscillator includes a first N-channel field effect transistor, a second N-channel field effect transistor cross-coupled to the first N-channel field effect transistor, a capacitor connected between the drain of the first N-channel field effect transistor and the drain of the second N-channel field effect transistor, an inductor connected in parallel with the capacitor, and a variable resistor or variable current source having one end connected to an intermediate tap of the inductor. The control unit controls the variable resistor or the variable current source based on the comparison result by the comparison unit. The oscillation device according to claim 5.

8. When the field effect transistor is a P-channel field effect transistor, the control unit controls the oscillation amplitude in a direction approaching the source potential of the P-channel field effect transistor so that the upper limit value of the oscillation amplitude approaches the source potential of the P-channel field effect transistor. The oscillation device according to claim 2.

9. The control unit controls the oscillation amplitude so that the upper limit value of the oscillation amplitude coincides with the source potential of the P-channel field effect transistor. The oscillation device according to claim 2.

10. The control unit includes an amplitude upper limit value detection unit that detects the upper limit value of the oscillation amplitude, and a comparison unit that compares the upper limit value of the oscillation amplitude with the source potential of the P-channel field effect transistor. The oscillation device according to claim 8.

11. The LC oscillator includes a first P-channel field effect transistor, a second P-channel field effect transistor cross-coupled to the first P-channel field effect transistor, a variable resistor or variable current source having one end connected to the source of the first P-channel field effect transistor and the source of the second P-channel field effect transistor, a capacitor connected between the drain of the first P-channel field effect transistor and the drain of the second P-channel field effect transistor, and an inductor connected in parallel with the capacitor. The control unit controls the variable resistor or the variable current source based on the comparison result by the comparison unit. The oscillation device according to claim 5.

12. The LC oscillator includes a first P-channel field effect transistor, a second P-channel field effect transistor cross-coupled to the first P-channel field effect transistor, a capacitor connected between the drain of the first P-channel field effect transistor and the drain of the second P-channel field effect transistor, an inductor connected in parallel with the capacitor, and a variable resistor or variable current source having one end connected to an intermediate tap of the inductor. The control unit controls the variable resistor or the variable current source based on the comparison result by the comparison unit. The oscillation device according to claim 5.

13. The oscillation device according to claim 1, further comprising a storage unit that stores a set value of the oscillation amplitude, and the control unit controls the oscillation amplitude of the oscillation signal based on the set value stored in the storage unit.

14. The control unit calibrates the oscillation amplitude based on a comparison result between the oscillation amplitude of the oscillation signal when the control unit controls the oscillation amplitude of the oscillation signal based on the set value of the oscillation amplitude and the source potential of the field effect transistor. The oscillation device according to claim 13.

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