JPH11234047A - Frequency conversion method and device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] A frequency conversion circuit using an imageless mixer system, which automatically corrects a change in circuit operation due to a temperature change and always keeps a good image suppression ratio. SOLUTION: A correction amount for each temperature is prepared in a control circuit 6 in advance, and the correction amount is read out in accordance with a change of a temperature detected by a temperature detection circuit 7 from a reference value, and the correction amount is read out.
制 御 Control the phase shift amounts of the phase shifters 1 a and 1 b and the amplification degree of the amplifier 5. At the start of operation such as when the power is turned on, a learning signal whose frequency is known is input, and the initial values of the phase shift amount and the amplification degree are set so that the image suppression ratio detected by the image suppression ratio detection circuit 8 is maximized. Make settings.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency conversion method and apparatus, and more particularly, to a frequency conversion method in an imageless mixer system configured to suppress an image frequency component generated when two frequency components are mixed. And its device.

[0002]

2. Description of the Related Art Direct digital synthesizers (D
When the oscillatable frequency bandwidth is limited as in DS), the required frequency is often obtained by performing frequency conversion by mixing with the output carrier of a fixed local oscillator. However, an image signal having a frequency other than the required frequency also appears at the output of the frequency conversion (multiplication) circuit. There is a method called an imageless mixer for suppressing this image signal, and two methods are usually considered.

One of the methods will be described with reference to FIG. In FIG. 3, the input signal is Ai * cos (ωi * t) and the local oscillator 4
Is the output of Ao * cos (ωo * t), the output of the multiplier 2a is

## EQU1 ## I (t) = Ao * cos (ωo * t) * Ai * cos (ωi * t) = (1/2) * Ao * Ai * {cos (ωo + ωi) t + cos (ωo- ωi) t} On the other hand, the output Q (t) of the multiplier 2b is determined by the 90 ° phase shifters 1a and 1b so that the input signal and the output of the local oscillator are 9
Because the phase is shifted by 0 °

(2) Q (t) = Ao * cos (ωo * t-90 °) * Ai * cos (ωi * t-90 °) = (1/2) * Ao * Ai * {cos ((ωo + ωi ) t-180 °) + cos (ωo-ωi) t} = (1/2) * Ao * Ai * {-cos (ωo + ωi) t + cos (ωo-ωi) t} Therefore, when I (t) and Q (t) are added by the synthesizer 3, the output S (t) becomes

S (t) = I (t) + Q (t) = Ao * Ai * cos (ωo-ωi) t, the image component cos (ωo + ωi) t is removed, and the required cos (ωo-ωi ) It is understood that only the component of t is included. However, in order to realize this ideally, the amplification degrees (amplitude components) of the systems of I (t) and Q (t) are equal, and the phase shift amounts of the 90 ° phase shifters 1a and 1b are exactly 90 °. There is a need.

Another conventional method will be described with reference to FIG.
As in FIG. 3, the input signal is Ai * cos (ωi * t) and the local oscillator 4
Is the output of Ao * cos (ωo * t), the output of the multiplier 2a is

[Equation 4] Ao * cos (ωo * t) * Ai * cos (ωi * t) = (1/2) * Ao * Ai * {c
os (ωo + ωi) t + cos (ωo-ωi) t} The output of the multiplier 2b is

(Equation 5) Ao * cos (ωo * t-90 °) * Ai * cos (ωi * t) = (1/2) * Ao *
Ai * {cos ((ωo + ωi) t-90 °) + cos ((ωo-ωi) t-90 °)} where ωi> ωo, ωd = | ωi-ωo | (LPF) 15 removes the frequency component of ωo + ωi in (Equation 4), and the output I (t) is

## EQU6 ## I (t) = (1/2) * Ao * Ai * cos (ωi-ωo) t = (1/2) * Ao * Ai * cos (ωd * t) Similarly, the output of the low-pass filter (LPF) 14 removes the frequency component of ωo + ωi in (Equation 5),

(7) (1/2) * Ao * Ai * cos ((ωi−ωo) t + 90 °) = (1/2) * Ao * Ai * cos (ωd * t + 90 °) The output Q (t) of the 90 ° phase shifter 1b is

Q (t) = (1/2) * Ao * Ai * cos (ωd * t + 90 ° -90 °) = (1/2) * Ao * Ai * cos (ωd * t) The output S (t) of the vessel 3 is obtained from (Equation 6) and (Equation 8),

S (t) = I (t) + Q (t) = Ao * Ai * cos (ωd * t)

On the other hand, when ωi <ωo, a low-pass filter (LP
F) The output of 15 is given by the equation in the first half of (Equation 6).

## EQU10 ## I (t) = (1/2) * Ao * Ai * cos (ωi-ωo) t = (1/2) * Ao * Ai * cos (-ωd * t) = (1/2) * Ao * Ai * cos (ωd * t) gives the same result as (Equation 6), but the low-pass filter (LPF) 1
For the output of 4,

(Equation 11) (1/2) * Ao * Ai * cos ((ωi−ωo) * t + 90 °) = (1/2) * Ao * Ai * cos (−ωd * t + 90 °) = ( 1/2) * Ao * Ai * cos (ωd * t-90 °) Therefore, the output Q (t) of the 90 ° phase shifter 1b is

(Equation 12) Q (t) = (1/2) * Ao * Ai * cos (ωd * t-90 ° -90 °) = (− 1/2) * Ao * Ai * cos (ωd * t) , The output S (t) of the synthesizer 3 is (Equation 10), (Equation 12)
From

S (t) = (1/2) * Ao * Ai * cos (ωd * t) − (1/2) * Ao * Ai * cos (ωd * t) = 0. As can be seen from the above (Equation 9) and (Equation 13),
In the conventional circuit of FIG. 4, the output S (t) is obtained only when ωi> ωo. However, in the case of FIG. 4, as in FIG.
The amplification degree (amplitude component) of the system of I (t) and Q (t) is equal, and the phase shift amounts of the 90 ° phase shifters 1a and 1b are exactly 90 °.
Is also required in this case.

[0006]

Here, in FIG. 3, it is assumed that the amplification factors of the system of I (t) and Q (t) are equal, that is, the difference between the amplitude components is 0, and the phase shift is 90 °. Consider the image suppression ratio when there is only an error in the phase shift amount of the shifter and other circuits. The first term of the last expression of (Equation 1) is (1 /
2) Combine * Ao * Ai * cos (ωo + ωi) t and (-1/2) * Ao * Ai * cos (ωo + ωi) t which is the first term of the last expression of (Equation 2) When there is a phase error Δ 系 of the entire system, the image signal Im (t)
Is

## EQU14 ## Im (t) = (1/2) * Ao * Ai * cos (ωo + ωi) t− (1/2) * A
o * Ai * cos {(ωo + ωi) t ± ΔΘ}. From this equation, if the required image signal suppression ratio is 30 dB, ΔΘ corresponds to about ± 3 °. On the other hand, an analog type 90 that can perform phase control
° There is a phase shifter, the accuracy of which is about 0.1 °.
The image suppression ratio for a phase error of about 0.1 ° is 4
From about 0 to 50 dB, the above condition can be sufficiently satisfied. Also, as for the error of the amplitude component, assuming that the error of the phase is 0,
To make the image signal suppression ratio 30 dB, an amplitude error 1d
B, in which case an adjustable attenuator is available.

[0007] From the above, it is possible to adjust the amplitude and the phase error to satisfy the conditions of the conventional technique, but it is premised on manual correction. However, since the amplitude and phase errors fluctuate due to changes in temperature and the like, it is necessary to perform manual correction every time the temperature environment changes, which requires a corresponding amount of time and may satisfy the operating conditions depending on the conditions. There was a problem that it would not be possible.

An object of the present invention is to prevent the image suppression ratio from automatically deteriorating even if the phase and amplitude of the 90 ° phase shifter of the imageless mixer circuit and the amplifier circuit of the system change due to environmental conditions such as temperature. It is an object of the present invention to provide a frequency conversion method and a frequency conversion method which can be controlled as described above.

[0009]

In order to achieve the above object, the present invention multiplies an input high-frequency signal and a local oscillator output by a first multiplier to generate a first output. A signal obtained by shifting the high-frequency signal by 90 ° by a first 90 ° phase shifter and an output obtained by shifting the output of the local oscillator by 90 ° by a second 90 ° phase shifter are multiplied by a second multiplier. Second
And a frequency conversion method for generating a frequency conversion output from which an image component has been removed by combining the first output and the second output.
The output phase of one or both of the first and second 90 ° phase shifters and the output amplitude of the first or second multiplier are adjusted so that the image component is suppressed by the output of the temperature detection circuit. Provided is a frequency conversion method characterized by controlling.

Further, according to the present invention, a first digital signal having a frequency corresponding to an input frequency designation signal is generated by a DDS circuit, and a second digital signal orthogonal to the first digital signal is generated.
After generating a digital signal, the first and second digital signals are converted into analog signals to obtain first and second input signals,
The first input signal is multiplied by a local oscillator output by a first multiplier to generate a first output, and the second input signal and the output of the local oscillator are shifted by 90 ° by a 90 ° phase shifter. Multiplied by a second multiplier to generate a second output,
A frequency conversion method for generating a frequency conversion output from which an image component has been removed by combining the first output and the second output, wherein the phase of the second digital signal is shifted by 90 °. Output phase of the vessel, and the first
Alternatively, the output amplitude of the second multiplier is controlled by the output of the temperature detection circuit so that the image component is suppressed, and the phases and amplitudes of the first and second digital signals are added to the frequency designation signal. Accordingly, a frequency conversion method is provided in which the image component is controlled so as to be suppressed.

Further, according to the present invention, an input high-frequency signal and a local oscillator output are multiplied by a first multiplier to generate a first output.
The signal shifted by 0 ° and the output of the local oscillator are converted to a second 90
A second multiplier generates a second output by multiplying the output shifted by 90 ° by a phase shifter by a second multiplier, and removes an image component by combining the first output and the second output. A frequency conversion method for generating a converted frequency conversion output, the output phase of one or both of the first and second 90 ° phase shifters, and the output phase of the first or second multiplier A frequency conversion method characterized by controlling an output amplitude so that an image suppression ratio detected by an image suppression detection circuit is maximized.

Further, according to the present invention, a first digital signal having a frequency corresponding to an input frequency designation signal is generated by a DDS circuit, and a second digital signal orthogonal to the first digital signal is generated.
After generating a digital signal, the first and second digital signals are converted into analog signals to obtain first and second input signals,
The first input signal is multiplied by a local oscillator output by a first multiplier to generate a first output, and the second input signal and the output of the local oscillator are shifted by 90 ° by a 90 ° phase shifter. Multiplied by a second multiplier to generate a second output,
A frequency conversion method for generating a frequency conversion output from which an image component has been removed by combining the first output and the second output, the phase and amplitude of the first and second digital signals, An output phase of the 90 ° phase shifter,
And a frequency conversion method for controlling the output amplitude of the first or second multiplier so that the image suppression ratio detected by the image suppression detection circuit is maximized.

The present invention also provides a local oscillator, a first multiplier for multiplying an input high-frequency signal by the output of the local oscillator to generate a first output, A first 90 ° phase shifter for phase shifting, a second 90 ° phase shifter for phase shifting the output of the local oscillator by 90 °, and the first and second 90 ° phase shifters. A second multiplier for multiplying the output of the multiplier to generate a second output, and generating a frequency conversion output from which image components have been removed by combining the first output and the second output. , A temperature detection circuit, and an output of the temperature detection circuit, the output phase of one or both of the first and second 90 ° phase shifters, and the first or second A control circuit for controlling the output amplitude of the multiplier so that the image component is suppressed. If, to provide a frequency conversion device characterized by comprising a.

Further, the present invention provides a DDS circuit for generating a first digital signal having a frequency corresponding to an input frequency designating signal, and a DDS circuit for generating a second digital signal orthogonal to the first digital signal. A second digital signal generation circuit, an analogization circuit for converting the first and second digital signals into analog to generate first and second input signals, a local oscillator, the first input signal, and the local A first multiplier for multiplying the output of the oscillator to generate a first output, a 90 ° phase shifter for shifting the output of the local oscillator by 90 °, and the second input signal. 9 above
An image component has been removed by combining the first output and the second output with a second multiplier for multiplying the output of the 0 ° phase shifter to generate a second output. A synthesizer for generating a frequency conversion output, a temperature detection circuit, and an output of the temperature detection circuit, the phase of the second digital signal, the output phase of the 90 ° phase shifter, and the first or second phase shifter. A first control circuit for controlling the output amplitude of the second multiplier so that the image component is suppressed; and a phase and amplitude of the first and second digital signals in accordance with the frequency designation signal. , A second control circuit for controlling the image component to be suppressed.

The present invention also provides a local oscillator, a first multiplier for multiplying an input high-frequency signal by the output of the local oscillator to generate a first output, A first 90 ° phase shifter for phase shifting, a second 90 ° phase shifter for phase shifting the output of the local oscillator by 90 °, and the first and second 90 ° phase shifters. A second multiplier for multiplying the output of the multiplier to generate a second output, and generating a frequency conversion output from which image components have been removed by combining the first output and the second output. One of the first and second 90 ° phase shifters so that the image suppression ratio detected by the image suppression ratio detection circuit is maximized. Or both output phases and the first or second
And a control circuit for controlling the output amplitude of the multiplier.

Further, the present invention provides a DDS circuit for generating a first digital signal having a frequency corresponding to an input frequency designation signal, and a second digital signal for generating a second digital signal orthogonal to the first digital signal. A second digital signal generation circuit, an analogization circuit for converting the first and second digital signals into analog to generate first and second input signals, a local oscillator, the first input signal, and the local A first multiplier for multiplying the output of the oscillator to generate a first output, a 90 ° phase shifter for shifting the output of the local oscillator by 90 °, and the second input signal. An image component is removed by combining a second multiplier for generating a second output by multiplying the output of the 90 ° phase shifter and generating a second output. Generates frequency converted output And combiner fit, and image rejection ratio detection circuit, so that the image suppression ratio which is detected by the image rejection ratio detecting circuit is maximum, the first and second
A frequency converter comprising: a control circuit for controlling a phase and an amplitude of a digital signal, an output phase of the 90 ° phase shifter, and an output amplitude of the first or second multiplier. I will provide a.

[0017]

Embodiments of the present invention will be described below in detail. FIG. 1 is a block diagram showing a configuration example of a frequency conversion device according to the present invention. The conventional circuit shown in FIG. 3 includes an amplifier 5, a control circuit 6, a temperature detection circuit 7, and an image suppression ratio detection circuit 8 having a variable amplification factor. It has an added configuration.
However, it is assumed that both the 90 ° phase shifters 1a and 1b can variably control the phase shift amount.

In the configuration of FIG. 1, a high-frequency signal input from a frequency synthesizer or the like and a high-frequency signal from the local oscillator 4 are converted into Ai * cos (ωi * t) and Ao
* cos (ωo * t), the output Q (t) of the multiplier 2b is given by (Equation 2) if the phase shift amounts of the 90 ° phase shifters 1a and 1b are exactly 90 ° and there is no error. The output I (t) of the multiplier 2a is given by (Equation 1). Among them, the output Q of the multiplier 2b
(t) is input to an amplifier 5 having a variable amplification factor for adjusting the amplitude. Thus, the 90 ° phase shifters 1a and 1b are both adjusted to have a phase shift amount of exactly 90 °, and the amplification of the amplifier is adjusted so that the amplitudes of the two high-frequency signals to the combiner 3 are equal. If so, the same condition as that derived from (Equation 3) is satisfied, so the output of the synthesizer 3 is given by S (t) of (Equation 3), and the image component is completely removed. .

In the configuration shown in FIG. 1, an automatic control mechanism is provided so that the above operation is maintained even if the environment changes. That is, a temperature detecting circuit 7 is provided as a circuit for detecting an environmental change, and a temperature change from a predetermined reference temperature is detected and sent to the control circuit 6. In the control circuit 6, control signals for the 90 ° phase shifters 1a and 1b for correcting a phase error and an amplitude error with respect to a temperature change,
And a control signal for the amplifier 5 is measured and determined in advance, and this is stored in a memory such as a ROM (Read Only Memory). Then, the phase control signal corresponding to the input from the temperature detection circuit 7 is read out from the ROM and sent out to the 90 ° phase shifters 1b and 1a, and the amplitude control signal is sent out to the amplifier 5, respectively. Is corrected.
Thus, as described above, an output from which the image signal is sufficiently suppressed by the automatic control can always be obtained as the output of the synthesizer 3.

In the above description, the phase error is shifted by 90 °
a and the phase shift amount of the 90 ° phase shifter 1b are corrected by controlling the phase shift amount, and the amplitude error is corrected by controlling the amplification degree of the amplifier 5, but it is not always necessary to perform the correction at this position. Absent. Finally, since it is only necessary that the two input image signal components have exactly the same phase and the same amplitude in the synthesizer 3, control is performed by either the 90 ° phase shifter 1a or the 90 ° phase shifter 1b. Is sufficient, and the 90 ° phase shifter 1a and the 90 ° phase shifter 1b
In addition, a separate phase shifter for correction may be provided and controlled.
Further, it is also possible to install a correction phase shifter and an amplifier on the route of the in-phase component of the input high-frequency signal to control the phase and the amplitude.

There are several ways of controlling the output of the temperature detection circuit 7 and the control circuit 6. In the above description, the temperature change from the reference temperature is detected by the temperature detection circuit 7 and sent to the control circuit. In this case, the initial value of the phase and amplitude control and the correction value of the phase and amplitude per change in temperature are recorded in the memory of the control circuit. When the power is turned on, first, the phases of the 90 ° phase shifters 1b and 1a and the amplification degree of the amplifier 5 are controlled by initial values, and thereafter, the phase amount and the amplitude amount that fluctuate due to a temperature change are read from the memory and controlled. As another method, a method may be used in which the current temperature itself is detected by the temperature detection circuit 7 instead of the temperature change, and this is sent to the control circuit. In this case, the memory of the control circuit 6 stores 90 ° for each temperature.
The correction values for the phase shifter and the amplifier are recorded. Even when the power is turned on, the correction value corresponding to the detected temperature at that time is 90
° The phase of the phase shifters 1b and 1a and the amplification degree of the amplifier 5 are controlled.

Either method can correct a phase error and an amplitude error with respect to a change in temperature. However, in the case of the method in which the temperature change is sent from the temperature detection circuit 7 to the control circuit, the phase, such as when the power is turned on, is stored in the memory.
It is expected that the initial value of the amplitude control will fluctuate due to temperature and other factors. Also, in the case of a method of transmitting a signal corresponding to the current temperature from the temperature detection circuit 7, a temperature measurement error in the temperature detection circuit or a 90 ° phase shifter or an amplifier for the temperature stored in the memory. It is conceivable that the correction value fluctuates due to aging or the like.

In order to remove the fluctuation of the initial value, a learning (training) signal is used when the power is turned on or the like.
A method of setting an initial value is conceivable. That is, the image suppression ratio detection circuit 8 of FIG. 1 is provided for this purpose, and inputs a signal of a predetermined frequency as a training signal as an input high-frequency signal. The training signal is phase-shifted by the 90 ° phase shifter 1b, multiplied by the signal of the local oscillator by the multiplier 2b, sent to the synthesizer 3 via the amplifier 5, and directly multiplied by the multiplier 2a. Combined with the signal. The output of the combiner 3 is input to an image suppression ratio detection circuit 8, where the magnitude of the image signal and the required signal are measured, and the image suppression ratio is obtained. Since the frequency of the training signal is predetermined, the frequency of the image signal is also predetermined, and the measurement of the image suppression ratio is easy. The output of the image suppression ratio detection circuit 8 is sent to the control circuit 6, and the control circuit 6 shifts by 90 ° so that the output of the image suppression ratio detection circuit 8 becomes maximum (the ratio between the required signal and the image signal is maximum). The phasers 1b and 1a and the amplifier 5 are controlled. Since the training time is very short, it is assumed that there is no temperature change, and the signal of the temperature detection circuit 7 is ignored. By doing so, the initial value can be accurately set each time the apparatus is powered on. In addition, not only when the power is turned on, but also a method in which training is performed at regular intervals, or a switch is manually operated to set an initial value is also conceivable.

Next, a case where a direct digital synthesizer (DDS) is applied to the present invention will be described with reference to FIG. It is assumed that the DDS of FIG. 2 is used for a spread spectrum communication system of a frequency hopping system. Now, assuming that the frequency hopping pattern is a pattern whose frequency can be switched between f1, f2,..., A pattern signal designating the pattern is input to the memory 9 from the signal path 16 as an address signal. f2... are sequentially output and input to the DDS circuit 10, thereby
The S circuit 10 sequentially outputs carriers of frequencies f1, f2,. The DDS circuit 10 receives a frequency data, and each time a reference clock is inputted, a phase accumulator which uses the accumulated value as phase information of a waveform to be output, and a waveform data which receives an output of the phase accumulator. Is generated from a waveform data generation circuit that generates However, in a normal DDS circuit,
The output of the waveform data generation circuit is directly input to the D / A conversion circuit to be used as an analog carrier.
° is input to a phase and amplitude control circuit 11 composed of a phase shifter and an amplifier. The phase and amplitude control circuit 11 outputs a cos component shifted by -90 ° with respect to the input signal and a sin component having the same phase as the input signal. And the cos component of the analog signal
It is converted into a sin component and input to the multipliers 2b and 2a, respectively. The subsequent configuration is the same as that of FIG. A control signal from the control circuit 6 generated in accordance with the output of the temperature detection circuit 7 is sent to the 90 ° phase shifter 1a and the amplifier 5 to perform temperature correction in the same manner as described with reference to FIG. It is not necessary to correct this temperature change every time the frequency is switched as described later.

In the configuration of FIG. 2, when the bandwidth of the frequency pattern is wide, a phase deviation or an amplitude deviation occurs depending on the frequency. For this purpose, the pattern signal on the signal path 16 is input to the phase and amplitude control circuit 11, and the circuit 11
Correction data for correcting the phase deviation and the amplitude deviation for each of the hopping frequencies f1, f2,... Is prepared in advance, and is read out with the pattern signal to correct an error due to a frequency change. Also, the phase and amplitude control circuit 11
Also includes the function of the 90 ° phase shifter 1b in FIG.
The correction of the phase shift amount with respect to the temperature is performed by the output of the control circuit 6. The control of the amplitude error may be performed by both the phase and amplitude control circuit 11 and the amplifier 5.

In the configuration of FIG. 2, a method of setting an initial value in the case of controlling by a change in temperature and a variation of the set initial value due to a secular change or environmental change are similar to those described with reference to FIG. Needs to be corrected. To do this, see FIG.
As described above, the image suppression ratio detection circuit 8 is provided, and the training is performed when the power is turned on by the training signal. That is, the training frequency is written in the memory 9 and the training frequency is stored in the DDS circuit 1.
0 and used as an input high-frequency signal. The magnitude of the image signal included in the output of the combiner 3 is detected by the image suppression ratio detection circuit 8 and sent to the control circuit 6. In the control circuit 6, the phase and amplitude are controlled by the phase and amplitude control circuit 11, the 90 ° phase shifter 1a, and the amplifier 5, and the output of the image suppression ratio detection circuit 8 is controlled to be maximum. If a single frequency is set as the training signal, the frequency of the image signal is also a single frequency.
Is simple.

In FIGS. 1 and 2 described above, the case where the image suppression ratio detecting circuit 8 is used only at the time of training for setting initial values of the phase and the amplitude has been described. However, a method of always using the image suppression ratio detection circuit 8 is also conceivable. That is, instead of operating the image suppression ratio detection circuit 8 with the training signal at the time of turning on the power, the image suppression ratio detection circuit 8 is operated at the time of a normal input signal, and the image suppression ratio is always kept at the maximum. In this case, the temperature detection circuit 7 becomes unnecessary. When the input high-frequency signal is constant, the configuration of the image suppression ratio detection circuit 8 is simple. However, when the input high-frequency signal changes as shown in FIG. Since the frequency also changes, an image suppression ratio detection circuit having a function of detecting a changing image signal is required. This can be realized by measuring an input frequency value using a fast Fourier transform or the like, determining a frequency of an image signal corresponding to the input frequency value, and detecting a component of the image frequency by digital signal processing.

In the description of FIGS. 1 and 2, the 90 ° phase shifter 1a, the multipliers 2a and 2b, the amplifier 5, the synthesizer 3, and the low-pass filters 14 and 15 are of the analog processing type. This can be digitally processed. With digital processing, the image suppression ratio can be improved as compared with the analog processing type.

[0029]

As described above in detail, according to the present invention, in the frequency conversion method using the imageless mixer system, even after power-on, a certain period of time has passed since power-on, and temperature change and the like have occurred. Even if there is a change in the environment, the image signal can be significantly suppressed by controlling and correcting the phase error and the amplitude error caused by the change. Also, by combining with a direct digital synthesizer (DDS), 20-30
A frequency conversion circuit that compensates for the drawback of the DDS, which has a frequency band of about MHz, can be obtained. In particular, it is useful to use the present invention for a frequency hopping type synthesizer.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a frequency conversion device according to the present invention.

FIG. 2 is a block diagram showing another configuration example of the frequency conversion device according to the present invention.

FIG. 3 is a block diagram showing an example of a conventional imageless mixer circuit.

FIG. 4 is a block diagram showing another example of a conventional imageless mixer circuit.

[Explanation of symbols]

 1a, 1b 90 ° phase shifter 2a, 2b multiplier 3 synthesizer 4 local oscillator 5 amplifier 6 control circuit 7 temperature detector 8 image suppression ratio detection circuit 9 memory 10 DDS circuit 11 phase amplitude control circuit 12, 13 D / A Converter 14, 15 Low-pass filter 16 Signal path

Claims (10)

[Claims] 1. An input high-frequency signal and a local oscillator output are multiplied by a first multiplier to generate a first output, and the input high-frequency signal is phase-shifted by 90 ° by a first 90 ° phase shifter. A second multiplier generates a second output by multiplying a signal and an output obtained by shifting the output of the local oscillator by 90 ° by a second 90 ° phase shifter to generate a second output. A frequency conversion method for generating a frequency conversion output from which an image component has been removed by combining the output of the first and second 90 ° phase shifters. And controlling the output amplitude of the first or second multiplier such that the image component is suppressed by the output of a temperature detection circuit. 2. The frequency conversion method according to claim 1, wherein at power-on, an input high-frequency signal having a known frequency is input as a learning signal, and an image suppression ratio at that time is detected to detect the detected image suppression. A frequency conversion method, comprising: initializing the output phases of the first and second 90 ° phase shifters and the output amplitude of the first or second multiplier so that the ratio is maximized. 3. A first digital signal having a frequency corresponding to the input frequency designation signal is generated by a DDS circuit, and a second digital signal orthogonal to the first digital signal is generated. The digital signal is converted into an analog signal to form a first and a second input signal. The first input signal is multiplied by a local oscillator output by a first multiplier to generate a first output. The output of the local oscillator is shifted by 90 ° by a 90 ° phase shifter and multiplied by a second multiplier to generate a second output, and the first output and the second output are combined. A frequency conversion method for generating a frequency conversion output from which an image component has been removed, the phase of the second digital signal, the output phase of the 90 ° phase shifter, and the first or second multiplication. Output amplitude of the In accordance with the output of the detection circuit, the image component is controlled so as to be suppressed, and the phases and amplitudes of the first and second digital signals are changed in accordance with the frequency designation signal so that the image component is suppressed. A frequency conversion method characterized by controlling. 4. The frequency conversion method according to claim 3, wherein at power-on, the frequency designation signal is a learning signal for designating a predetermined frequency, and an image suppression ratio at that time is detected to detect the frequency. The output phase of the 90 ° phase shifter and the first phase shifter so that the obtained image suppression ratio is maximized.
Alternatively, an initial setting of an output amplitude of a second multiplier and phases and amplitudes of the first and second digital signals is performed. 5. An input high frequency signal and a local oscillator output are multiplied by a first multiplier to generate a first output, and the input high frequency signal is shifted by 90 ° by a first 90 ° phase shifter. A second multiplier generates a second output by multiplying a signal and an output obtained by shifting the output of the local oscillator by 90 ° by a second 90 ° phase shifter to generate a second output. A frequency conversion method for generating a frequency conversion output from which an image component has been removed by combining the output of the first and second 90 ° phase shifters. And controlling the output amplitude of the first or second multiplier so that the image suppression ratio detected by the image suppression detection circuit is maximized. 6. A first digital signal having a frequency corresponding to the input frequency designation signal is generated by a DDS circuit, and a second digital signal orthogonal to the first digital signal is generated. The digital signal is converted into an analog signal to form a first and a second input signal. The first input signal is multiplied by a local oscillator output by a first multiplier to generate a first output. The output of the local oscillator is shifted by 90 ° by a 90 ° phase shifter and multiplied by a second multiplier to generate a second output, and the first output and the second output are combined. A frequency conversion method for generating a frequency conversion output from which an image component has been removed, the phase and the amplitude of the first and second digital signals, the output phase of the 90 ° phase shifter, and the first Or the second multiplier Frequency conversion method characterized by the output amplitude, image rejection ratio detected by the image rejection detection circuit is controlled to be maximum. 7. A local oscillator, a first multiplier for multiplying an input high-frequency signal by an output of the local oscillator to generate a first output, and phase-shifting the input high-frequency signal by 90 °. First 90 for
A phase shifter; and a second 9 for phase shifting the output of the local oscillator by 90 °.
Multiplying the outputs of the first and second 90 ° phase shifters by a second
A second multiplier for generating an output of the first and second outputs; a synthesizer for generating a frequency conversion output from which an image component has been removed by combining the first output and the second output; And a first and second 9 by the output of the temperature detection circuit.
A control circuit for controlling the output phase of one or both of the 0 ° phase shifters and the output amplitude of the first or second multiplier so that the image component is suppressed. A frequency conversion device characterized by the above-mentioned. 8. A DDS circuit for generating a first digital signal having a frequency corresponding to an input frequency designation signal, and a second digital signal for generating a second digital signal orthogonal to the first digital signal. A generation circuit, and converting the first and second digital signals into analog
And an analog circuit for generating a second input signal; a local oscillator; and a first multiplier for generating a first output by multiplying the first input signal by an output of the local oscillator. A 90 ° phase shifter for shifting the output of the local oscillator by 90 °; and a second output for generating a second output by multiplying the second input signal by the output of the 90 ° phase shifter. A second multiplier, a synthesizer for generating a frequency conversion output from which an image component has been removed by combining the first output and the second output, a temperature detection circuit, and the temperature detection circuit To control the phase of the second digital signal, the output phase of the 90 ° phase shifter, and the output amplitude of the first or second multiplier so that the image component is suppressed. A first control circuit, and the first and second digital signals A second control circuit for controlling a phase and an amplitude of the signal in accordance with the frequency designation signal so that the image component is suppressed. 9. A local oscillator, a first multiplier for multiplying an input high-frequency signal by an output of the local oscillator to generate a first output, and phase-shifting the input high-frequency signal by 90 °. First 90 for
A phase shifter; and a second 9 for phase shifting the output of the local oscillator by 90 °.
Multiplying the outputs of the first and second 90 ° phase shifters by a second
A second multiplier for generating an output of the image processing apparatus; a synthesizer for generating a frequency conversion output from which an image component has been removed by synthesizing the first output and the second output; A ratio detection circuit, and the first and second 90 ° angles so that the image suppression ratio detected by the image suppression ratio detection circuit is maximized.
And a control circuit for controlling an output phase of one or both of the phase shifters and an output amplitude of the first or second multiplier. 10. A DDS circuit for generating a first digital signal having a frequency corresponding to an input frequency designation signal, and a second digital signal for generating a second digital signal orthogonal to the first digital signal A generation circuit, and converting the first and second digital signals into analog
And an analog circuit for generating a second input signal; a local oscillator; and a first multiplier for generating a first output by multiplying the first input signal by an output of the local oscillator. A 90 ° phase shifter for shifting the output of the local oscillator by 90 °; and a second output for generating a second output by multiplying the second input signal by the output of the 90 ° phase shifter. A second multiplier; a combiner for combining the first output and the second output to generate a frequency conversion output from which an image component has been removed; an image suppression ratio detection circuit; The phase and amplitude of the first and second digital signals, the output phase of the 90 ° phase shifter, and the first or second multiplication so that the image suppression ratio detected by the suppression ratio detection circuit is maximized. A control circuit for controlling the output amplitude of the vessel, A frequency conversion device comprising: