JP2001036384A - Variable tuning filter, adjusting method therefor, receiving device and transmitting device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the variable turning filter of high central frequency accuracy and little gain deviation with an irreducibly minimum configuration and simple adjustment and a adjusting method therefor. SOLUTION: This filter 1 is provided with band pass filters 2 and 3 to change the tuning frequency corresponding to a control signal, a gain control means 4 for changing the gain corresponding to a control signal, a control signal generating means 7 for generating the control signals to be applied to the band pass filters 2 and 3 and the gain control means 4 and a storage means 8 for storing the control signals generated by the control signal generating means 7. Corresponding to the change in the tuning frequency of the band pass filters 2 and 3, the CPU 7 controls the center frequency of the band pass filters 2 and 3 and the gain of a variable gain amplifier via D/A converters 5 and 6 according to the control signals stored in the storage means 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tunable filter mainly used for a wide band receiver or a transmitter, and more particularly, to a center frequency accuracy is high and a gain deviation is small by a minimum necessary configuration and simple adjustment. The present invention relates to a tunable filter and a method for adjusting the tunable filter.

[0002]

2. Description of the Related Art Conventionally, a wide band receiver (for example, 50 MH)
As a configuration example of a TV receiver or a CATV receiver that receives a frequency of about z to 2000 MHz, for example, as shown in Japanese Patent Laid-Open No. 6-62330, a control voltage generated by a frequency synthesizer of a local oscillation unit is applied to a high frequency stage. There is known a configuration in which a control voltage of a tunable filter provided is provided so that a gradient of a change in a local oscillation frequency matches a gradient of a change in a tuning frequency of the tunable filter (direct tracking type).

In this type of receiver, for example, as disclosed in Japanese Patent Application Laid-Open No. 9-102752, the control voltage of the tunable filter is independent of the control voltage generated by the frequency synthesizer of the local oscillator. There is a known configuration (independent tracking type) that is configured to provide the information.

In this type of receiver, for example, as shown in Japanese Utility Model Application Laid-Open No. 3-32109, a control voltage generated by a frequency synthesizer of a local oscillator is used as a control voltage of a tunable filter with a specific gradient. (Conversion tracking type) is known which is configured to apply a converted voltage.

A tunable filter of this type is known as a module component (a tunable filter module). Also, equipped with a frequency synthesizer,
There is known a module component (synthesized tunable filter module) configured to apply a control voltage generated by a frequency synthesizer to a tunable filter.

A tunable filter used in this type of receiver or module includes, for example, a fixed inductor and a variable capacitance element (varactor diode) as disclosed in Japanese Patent Laid-Open No. 7-38384. Things (varactor tune filters) are known. This type of filter generally has a frequency variable range of 1 octave or more (for example, 200 to 400 MHz) using a varactor diode having a high capacitance change ratio.

A double tuning circuit is used as this type of variable tuning filter. As an example of this, for example, as shown in Japanese Utility Model Laid-Open No. 1-132118,
There has been proposed a filter (coupling degree control type varactor tune filter) capable of controlling the degree of coupling of a double tuning circuit.

[0008]

However, in the above-described conventional direct tracking receiver or synthesized tunable filter module, the gradient of the change in the local oscillation frequency and the gradient of the change in the tuning frequency of the tunable filter are reduced. Needed to match. For this reason, for example, it is necessary to perform rank selection in which the capacitance deviation of the variable capacitance element is specified to be narrow, or to adjust an adjustment element such as an inductor manually or mechanically in a production process.
There are problems such as deterioration of production yield and increase in adjustment locations.

In the conventional independent tracking type receiver or variable tuning filter module, the control voltage vs. tuning frequency characteristic of the variable tuning filter is stored in a control unit such as a CPU in advance, so that the conventional direct tracking type receiver or variable tuning filter module can be used. Could solve the problem of production. However, it is generally necessary to store the control voltage vs. tuning frequency characteristics of the tunable filter individually for each variable-capacitance element that is low-cost and has a large capacitance deviation, and to reduce the number of adjustment points such as inductors. There was a problem.

In the conventional conversion tracking type receiver or synthesized tunable filter module, the circuit for converting the control voltage generated by the frequency synthesizer into the control voltage of the tunable filter may be individually adjusted. Therefore, there is a problem that it is difficult to cope with a variable capacitance element having a large capacitance deviation and to reduce the number of adjustment portions such as inductors.

On the other hand, in the conventional varactor tuned filter, the reverse bias voltage vs. series resistance characteristic of the varactor diode, which is a variable capacitance element, the matching characteristic of the tuning circuit and the circuits before and after, and the change in the degree of coupling of the double tuning circuit, There is a problem that a large deviation in insertion loss occurs. Generally, when the control voltage is low (the tuning frequency is low), the insertion loss is large, and the control voltage is high (the tuning frequency is high).
In this case, the insertion loss is small, and the deviation is, for example, 1 to 5
It was about dB.

Further, in the above-mentioned conventional coupling degree control type varactor tune filter, although there is an effect of suppressing the change in the coupling degree, there is a problem that a large deviation of the insertion loss cannot be reduced. In addition, although the tracking problem of the conventional receiver can be improved to some extent by increasing the degree of coupling to widen the pass frequency band, there is a problem that the wideband operation deteriorates the interference characteristics.

The present invention has been made to solve the above-mentioned conventional problems, and provides a tunable filter having a high center frequency accuracy and a small gain deviation and a method of adjusting the tunable filter by using a minimum necessary configuration and simple adjustment. It is an object of the present invention to provide a receiving apparatus and a transmitting apparatus which do not require tracking adjustment and have a small gain deviation.

[0014]

In order to solve the above-mentioned conventional problems, a tunable filter according to the present invention comprises a band-pass filter for changing a tuning frequency, and a control signal generating means for generating a control signal to be supplied to a gain control means. And a storage means for storing the generated control signal, wherein the gain of the gain control means is changed according to the change of the tuning frequency of the band-pass filter.

The method for adjusting the tunable filter of the present invention is as follows.
In order to solve the above-mentioned conventional problems, a wideband noise source is connected to the input terminal of the tunable filter of the present invention, a frequency selective receiver is connected to the output terminal of the tunable filter of the present invention, and the detected frequency versus the detected output From the result of the above, determine the value of the control signal corresponding to the tuning frequency, or connect a standard signal generator to the input end of the tunable filter of the present invention, and connect the wideband level detector to the output of the tunable filter of the present invention. The control signal is connected to the end, and the value of the control signal corresponding to the tuning frequency is determined from the result of the detected frequency versus the detection output.

Also, the tunable filter of the present invention provides a first control signal from the frequency synthesizer to the band-pass filter, and a second control signal from the control signal generating means to the band-pass filter.
Control signal, the local oscillation output of the frequency synthesizer is applied to the input of the variable tuning filter, and the output level is detected by the wideband level detector, thereby self-adjusting the tuning frequency of the bandpass filter. is there.

Further, the tunable filter of the present invention includes a gain control means and a limiter connected to a local oscillation output of the frequency synthesizer, and detects an output level by a wideband level detector, thereby improving a frequency-gain characteristic. It is self-adjusting. Further, in the above variable tuning filter, a band rejection filter is used as a filter capable of changing a tuning frequency.

The receiving apparatus according to the present invention is configured using the tunable filter according to the embodiment of the present invention. Further, the transmission device of the present invention is configured using the tunable filter according to the embodiment of the present invention.

The tunable filter according to the first aspect of the present invention includes a band-pass filter for changing a tuning frequency, and gain control means for changing a gain. Correspondingly, the gain of the gain control means is changed, and has an effect that the gain deviation can be reduced by a minimum necessary configuration.

According to a second aspect of the present invention, there is provided a tunable filter comprising: a band-pass filter for changing a tuning frequency by a control signal; gain control means for changing a gain by a control signal; Control signal generating means for generating a control signal to be given to the control means,
A storage means for storing a control signal generated by the control signal generation means is provided, and has an effect that a gain deviation can be reduced by a minimum necessary configuration and simple adjustment.

According to a third aspect of the present invention, there is provided a method for adjusting a tunable filter according to the first or second aspect.
A method for adjusting a tunable filter according to claim 1, wherein a broadband noise source is connected to an input terminal, a frequency selective receiver is connected to an output terminal, and the frequency of the tunable filter detected by the frequency selective receiver is adjusted. The value of the control signal to be applied to the band-pass filter and the gain control means is determined in accordance with the frequency from the result of the detection output, and a tunable filter having a small gain deviation is manufactured by simple adjustment. It has the effect of being able to.

According to a fourth aspect of the present invention, there is provided a method for adjusting a tunable filter according to the first or second aspect.
An adjustment method for adjusting the tunable filter according to the above, wherein a standard signal generator is connected to an input terminal, a wideband level detector is connected to an output terminal, and the tunable filter detected by the wideband level detector is connected. The value of the control signal to be applied to the band-pass filter and the gain control means is determined in accordance with the frequency from the result of the frequency-to-detection output, and a tunable filter having a small gain deviation is manufactured by simple adjustment. Has the effect of being able to

A tunable filter according to a fifth aspect of the present invention is a band-pass filter that changes a tuning frequency by first and second control signals, and supplies a first control signal to the band-pass filter. A frequency synthesizer, control means for controlling the bandpass filter and the frequency synthesizer, second control signal generating means for generating a second control signal for changing a tuning frequency of the bandpass filter, and a wideband level detector A local oscillation output of the frequency synthesizer is input, and an output level is detected by the wideband level detector, whereby the tuning frequency of the bandpass filter is self-adjusted. And the simple adjustment makes it possible to increase the center frequency accuracy.

A tunable filter according to a sixth aspect of the present invention includes: a gain control means for changing a gain by a control signal; and a limiter connected to a local oscillation output of the frequency synthesizer. The output level is detected by the detector and the frequency-gain characteristics are self-adjusted.The center frequency accuracy can be increased by the minimum necessary configuration and simple adjustment, and the gain deviation can be reduced especially. Has an action.

The tunable filter according to the invention of claim 7 uses a band rejection filter as a filter for changing the tuning frequency. The center tunable filter has a minimum necessary configuration and simple adjustment. It has the effect of increasing accuracy.

A receiving apparatus according to an eighth aspect of the present invention includes the tunable filter according to the first, second, fifth, sixth or seventh aspect, or a tunable filter according to the third or fourth aspect. This method uses a filter adjustment method, and has an effect that it is possible to realize a receiver having a small interference frequency and a small frequency deviation in sensitivity with a minimum necessary configuration and simple adjustment.

According to a ninth aspect of the present invention, there is provided a receiving apparatus including the tunable filter according to the first, second, fifth, sixth or seventh aspect, or a tunable filter according to the third or fourth aspect. This method uses a filter adjustment method, and has an effect that a transmission device having a small spurious performance and a small frequency deviation of a transmission output can be realized by a minimum necessary configuration and simple adjustment.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 to 4 of the present invention will be described below in detail with reference to FIGS. (Embodiment 1) First, a tunable filter and an adjustment method thereof according to Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration of a tunable filter and an adjusting device thereof according to Embodiment 1 of the present invention. In FIG. 1, a tunable filter 1, a broadband noise source 11, a tuner 12, and a control unit 13 constitute an adjusting device for the tunable filter 1. The tunable filter 1 is composed of band-pass filters 2 and 3 and a tunable filter. A gain amplifier 4, D / A converters 5 and 6, a CPU 7,
Memory 8, control signals 9 and 10, and broadband noise source 11
, A tuner 12 and a control unit 13.

In FIG. 1, a tunable filter 1 is a filter capable of setting an accurate center frequency within a range of frequencies f1 to f2 according to an external frequency setting. Each of the band-pass filters 2 and 3 is composed of, for example, a tunable element and an inductor.
Can be changed by The range of the controllable center frequency is f1 to f2. The variable gain amplifier 4 as a gain control means is an amplifier capable of amplifying the band of the frequencies f1 to f2, and the gain thereof is controlled by the control signal
ＧGmax.

The D / A converters 5 and 6 operate to convert digital signals from the CPU 7 into control signals 9 and 10 which are analog voltages. The CPU 7 controls the operation of the tunable filter according to an external instruction. The memory 8 as a storage means is, for example, a rewritable EPROM.
And stores the value of the control signals 9 and 10 with respect to the frequency. The tunable filter 1 is composed of these components.
Is configured. The D / A converters 5 and 6 and the CPU
7 constitute control signal generating means.

The broadband noise source 11 is composed of, for example, a pure resistor and a wideband amplifier, and outputs a constant level of white noise in a frequency range of f1 to f2. The tuner 12 as a frequency selective receiver selectively receives a range of frequencies f1 to f2 and detects a reception level. The control unit 13 is a tuner 1
2 and the CPU 7 to control the tunable filter 1
Is a computer that makes adjustments.

Next, the operation of the tunable filter according to the first embodiment of the present invention will be described with reference to FIG. In the tunable filter 1 configured as described above, the signal input to the tunable filter 1
, And is amplified by the variable gain amplifier 4, and further band-limited by the band-pass filter 3 and output. The relationship between the center frequencies of the band-pass filters 2 and 3 and the control signal 9 (analog voltage) is represented by a voltage value versus frequency characteristic as a frequency value (absolute frequency value) at a prescribed voltage and a voltage-frequency slope (differential gain). expressed. Both the frequency absolute value and the differential gain have individual deviations,
When manufacturing the tunable filter 1, a manufacturing deviation occurs.

In the tunable filter according to the present invention, the absolute frequency value and the differential gain are checked in advance in the manufacturing process, and the values are stored in the memory 8. CP
U7 reads the frequency absolute value and differential gain of the bandpass filters 2 and 3 from the memory 8 according to the frequency setting from the outside, and accurately sets the center frequency of the bandpass filters 2 and 3 via the D / A converter 5. Works like that.

Here, the insertion loss of the band-pass filters 2 and 3 has a frequency deviation in the range from the frequency f1 to f2, and the insertion loss is generally lower on the low frequency (f1) side than on the high frequency (f2) side. large. For example, the insertion loss is f1
5 dB for f2 and 2 dB for f2. In this case, the total insertion loss of the bandpass filters 2 and 3 is 10
dB (f1) to 4 dB (f2).

The variable tuning filter according to the present invention operates such that the insertion loss deviation is checked in advance in the manufacturing process, and the variable gain amplifier 4 is controlled so as to correct the insertion loss. For example, assume that the maximum gain Gmax of the variable gain amplifier 4 is 20 dB and the minimum gain Gmin is 0 dB. The target value of the gain of the entire tunable filter according to the present invention is set to 5 dB. In this case, if the gain of the variable gain amplifier 4 is controlled to 15 dB at the frequency f1 and 9 dB at the frequency f2, the overall gain can be 5 dB at the frequencies f1 and f2. Also,
Even at a frequency between f1 and f2, a flat gain-frequency characteristic can be obtained by correcting the gain with sufficient frequency resolution.

Next, an adjustment method in the manufacturing process of the tunable filter according to the first embodiment of the present invention will be described with reference to FIG. First, a signal output from the broadband noise source 11 is added to an input, and the output is detected by the tuner 12. The control unit 13 changes the selected frequency of the tuner 12 between f1 and f2. At each frequency point, the control unit 13 issues a command to the CPU 7, changes the center frequency of the bandpass filters 2 and 3, and searches for the value of the control signal 9 that maximizes the detection level of the tuner 12. The value of the control signal 9 is stored in the memory 8.

Thereafter, the gain of the variable gain amplifier 4 is further controlled to search for a value of the control signal 10 such that the detection level in the tuner 12 becomes a prescribed value (a value that makes the overall gain 5 dB). The value of the control signal 10 is stored in the memory 8
To memorize. By performing such adjustment in the manufacturing process, the values of the control signals 9 and 10 corresponding to each frequency can be stored in the memory 8. As explained above,
One of the features of the tunable filter according to the present embodiment is that the gain deviation can be reduced by changing the center frequency of the band-pass filter and controlling the gain of the variable gain amplifier.

Another feature is that the set values for the frequencies of the band-pass filter and the variable gain amplifier are stored,
The point is that the gain deviation can be reduced by reading and setting it during operation. A feature of the adjustment method according to the present embodiment is that the gain of the variable gain amplifier can be adjusted simultaneously with the adjustment of the band-pass filter by inputting the wideband noise signal, selecting the frequency of the output with the tuner, and detecting the level. .

As is clear from the above description, according to the tunable filter and the adjusting method in the present embodiment,
A tunable filter having a small gain deviation can be manufactured by simple adjustment. The configuration of the band-pass filter and the insertion loss value are not limited to the description of the present embodiment, and the same effects can be obtained as long as the same operation is performed. Further, even if the variable gain amplifier is, for example, a variable attenuator, the same effect can be obtained.

(Embodiment 2) Next, referring to FIG.
A tunable filter and a method for adjusting the tunable filter according to Embodiment 2 of the present invention will be described. FIG. 2 is a block diagram showing a configuration of a tunable filter and an adjusting device thereof according to Embodiment 2 of the present invention. In FIG. 2, elements including the tunable filter 1 and denoted by the same reference numerals as those in FIG. 1 are the same and operate in the same manner.
Reference numeral 5 denotes a broadband level detector, which together with the control unit 13 constitutes an adjusting device for the tunable filter 1.

In FIG. 2, the tunable filter 1 is
Are the same as those shown in FIG. The signal generator 14 generates a signal of a stable frequency and level over a wide band, and the frequency and the output level are controlled by the control unit 13. The broadband level detector 15 is configured by, for example, a diode, and performs level detection over a wide band.
The output of the wideband level detector 15 is input to the control unit 13.

Next, with reference to FIG. 2, a description will be given of an adjustment method in a manufacturing process performed using the tunable filter adjustment apparatus according to the second embodiment of the present invention. This adjusting device applies the signal output from the signal generator 14 to the input of the tunable filter 1 and outputs the output to the wideband level detector 1.
5 is configured to detect.

The control section 13 changes the frequency of the signal generator 14 between f1 and f2. At each frequency point, the control unit 13 issues a command to the CPU 7, changes the center frequency of the bandpass filters 2 and 3, and searches for the value of the control signal 9 at which the detection level of the wideband level detector 15 is maximized. The value of the control signal 9 is stored in the memory 8. Thereafter, the gain of the variable gain amplifier 4 is further controlled to search for a value of the control signal 10 such that the detection level in the wideband level detector 15 becomes a specified value (a value that makes the overall gain 5 dB). The value of the control signal 10 is stored in the memory 8. By performing such adjustments in the manufacturing process,
The values of the control signals 9 and 10 corresponding to each frequency are stored in the memory 8
Can be stored.

As described above, the characteristic of the adjusting method according to the present embodiment is that a test signal of a specific frequency is input from a signal generator and the output is detected by a wide-band level detector, whereby a band-pass filter is provided. And that the gain of the variable gain amplifier can be adjusted simultaneously. As is clear from the above description, according to the adjustment method of the present embodiment, a tunable filter having a small gain deviation can be manufactured by simple adjustment.

(Embodiment 3) Next, referring to FIG.
A tunable filter according to Embodiment 3 of the present invention will be described. FIG. 3 is a block diagram showing a configuration of a tunable filter according to Embodiment 3 of the present invention. In FIG. 3, elements denoted by the same reference numerals as those in FIGS. 1 and 2 are the same and operate in the same manner, and the tunable filter according to the third embodiment includes a PLL unit 19 and a band-pass filter 23. , 24 as well as the CPU 7 as control means for controlling the variable gain amplifier 4, and the first and second control signals 16
And 17, a VCO 18, a PLL unit 19, a limiter amplifier 20, a high-frequency SW 21, a wide-band level detector 22, and band-pass filters 23 and 24. Further, the D / A converter 5 and the CPU 7 constitute a second control signal generating means.

In FIG. 3, the operating frequency ranges of the band-pass filters 23 and 24 and the variable gain amplifier 4 are f1 to f2.
It is. The center frequencies of the band-pass filters 23 and 24 are controlled by the first control signal 16 in the range of f1 to f2. The second control signal 17 is a control signal for fine adjustment of the center frequency, and its frequency-to-voltage differential sensitivity is, for example, about 1/10 of that of the first control signal 16. For example,
Assuming that f1 is 1400 MHz and f2 is 2000 MHz (that is, the variable range is 600 MHz), the second control signal 1
The frequency width finely adjusted by 7 is 60 MHz.

The VCO 18 and the PLL unit 19 constitute a PLL frequency synthesizer, and its frequency is set to a predetermined value between f1 and f2 by a command from the CPU (control means) 7. The first control signal 16 includes a VCO 18 and a PLL.
This is a tuning voltage of the PLL frequency synthesizer formed by the unit 19, and is a voltage corresponding to the oscillation frequency of the VCO 18. For example, the first control signal 16 is 1 V when the frequency of the VCO 18 is f1 (1400 MHz) and f2 (2000
MHz) at 15V.

Here, when the center frequency of the band-pass filters 23 and 24 is f1 when the first control voltage 16 is 1 V,
(1400 MHz) and f2 (200
0 MHz). The frequency-voltage characteristics at each frequency point are set so as to match the characteristics of the VCO 18 as much as possible. By doing so, the center frequency of the bandpass filters 23 and 24 is
Tracking is performed at the set frequency of the PLL frequency synthesizer composed of the VCO 18 and the PLL unit 19.

The limiter amplifier 20 amplifies the output signal of the VCO 18 to a certain level and outputs it to the high frequency SW 21.
The high-frequency SW 21 is a wide-band SW composed of, for example, a GaAs-MMIC, and selects either the input signal of the tunable filter 1 or the output of the limiter amplifier 20 and inputs the selected signal to the band-pass filter 23.

The wide-band level detector 22 is composed of, for example, a diode, and has a band-pass filter 24.
(That is, the output level of the tunable filter 1) is detected over a wide band. The level detection result is input to the CPU 7.

Next, the operation of the tunable filter according to the third embodiment of the present invention will be described with reference to FIG. In the tunable filter 1 configured as described above, the tunable filter 1 has two operation modes, a normal operation mode and a self-adjustment mode. These two operation modes are selected by applying a command to the CPU 7 by operation.
Is controlled by

First, in the self-adjustment mode, the CP
The high frequency SW 21 is switched to the limiter amplifier 20 by the command of U7.
Choose the side. Therefore, the output of the VCO 18 is amplified to a certain level by the limiter amplifier 20 and input to the band-pass filter 23. In this state, the CPU
7 instructs the PLL unit 19 to change the frequency of the VCO 18 from f1 to f2 sequentially with a certain frequency resolution. Further, at each frequency point, the output is detected by the wideband level detector 22. At this time, the band-pass filters 23 and 24 are adjusted so that the output becomes maximum, and the gain of the variable gain amplifier 4 is controlled so that the maximum output level becomes a predetermined value. These operations are referred to as f1 to f
The self-adjustment of the tunable filter 1 is completed by performing a sufficient frequency resolution between the two.

Here, the frequency of the VCO 18 and the center frequency of the band-pass filters 23 and 24 change (track) in an interlocking manner within the range of f1 to f2. However, generally, the frequency-voltage characteristics of the VCO 18 and the band-pass filters 23 and 24 have individual differences (variations).
Therefore, it is necessary to correct the frequency of the VCO 18 and the center frequencies of the bandpass filters 23 and 24 at the respective frequency points in the range of f1 to f2. In the present embodiment, this correction is performed by fine adjustment using the second control signal 17, and the tracking adjustment is performed by storing the correction value at each frequency point in the memory 8. That is, the CPU 7 controls the second control signal 17 via the D / A converter 5 so that the detection level of the wideband level detector 22 becomes maximum at each frequency point.
And the value of the second control signal 17 at the maximum level is stored in the memory 8.

The insertion loss of the bandpass filters 23 and 24 has a frequency deviation in the range from the frequency f1 to f2. In the present embodiment, the variable gain amplifier 4 is controlled so as to correct the insertion loss. That is, CPU
Numeral 7 controls the gain of the variable gain amplifier 4 via the D / A converter 6 and the control signal 10 so that the detection level of the wideband level detector 22 becomes a predetermined value at each frequency point of the tracking adjustment. The value of the control signal 10 at this time is stored in the memory 8. With the above operation, the self-adjustment ends.

Second, in the normal operation mode, the input of the tunable filter 1 is selected as the high frequency SW 21.
Here, the CPU 7 sets the frequency of the VCO 18 in response to an external frequency setting command, thereby setting the center frequency of the entire variable tuning filter. At this time, CP
U7 reads and sets the values of the second control signal 17 and the control signal 10 for each frequency point stored in the memory 8 in the self-adjustment mode.

In the above description, it is assumed that the filters 23 and 24 are band-pass filters. Here, for example, when 23 and 24 are band rejection filters,
Correction of the band rejection filter and self-adjustment so that the detection level of the wide band level detector 22 is minimized makes it possible to set an accurate center frequency (rejection frequency).

By the above operation, the tunable filter 1 is set to an accurate center frequency and a constant gain. Further, the above-mentioned frequency-voltage characteristics, insertion loss and gain are accompanied by changes in temperature and humidity and aging. However, the tunable filter 1 can always obtain an accurate center frequency and gain by regularly performing the above-described self-adjustment operation and updating the stored value of the memory 8 each time.

As described above, one of the features of the tunable filter in this embodiment is that the VCO in the self-adjustment mode is used as a means for tracking adjustment of the frequency setting of the PLL frequency synthesizer and the center frequency of the band-pass filter. The maximum level point is detected by using the output signal of (1), and the correction value of the band-pass filter at that time is stored.

Another feature of the tunable filter according to the present embodiment is that the VCO output is amplified to a constant level by a limiter amplifier, and the variable gain is adjusted by utilizing the constant level signal at the same time as tracking adjustment of the band-pass filter. The point is that the correction value of the amplifier is stored.

Another feature of the tunable filter according to the present embodiment is that the output signal of the VCO is used in the self-adjustment mode as a means for tracking adjustment of the frequency setting of the PLL frequency synthesizer and the center frequency of the band rejection filter. That is, the minimum level point is detected, and the correction value of the band rejection filter at that time is stored.

As is clear from the above description, according to the tunable filter of the present embodiment, the center frequency accuracy can be increased and the gain deviation can be reduced by the minimum necessary configuration and simple adjustment.

(Embodiment 4) Next, referring to FIG.
A receiving device including a tunable filter according to Embodiment 4 of the present invention will be described. FIG. 4 is a block diagram showing a configuration of a receiving apparatus according to Embodiment 4 of the present invention.
4, a receiving apparatus according to the fourth embodiment includes a mixer 25, a local oscillator 26, an intermediate frequency filter 2
7, the demodulation unit 28, the control unit 31, and the low noise amplifier 35
It is composed of

In FIG. 4, the tunable filter 1 is
Similar to the filters shown in FIGS. 1 to 3, the filter is capable of setting an accurate center frequency in a range of frequencies f1 to f2 in accordance with an external frequency setting (control signal 32). The center frequency of the tunable filter 1 is controlled by a control unit 31 via a control signal 32.
Is set from The gain of the tunable filter 1 is f
There is no deviation between 1 and f2 and 5 dB.

Here, for example, a description will be given on the assumption that the receiving frequency range of the receiving apparatus is f1 to f2, f1 is 1400 MHz, and f2 is 2000 MHz. The low noise amplifier 35
The input signal in the range from f1 to f2 is amplified with a gain of, for example, 20 dB. The amplified signal is band-limited by the tunable filter 1 and input to the mixer 25. The local oscillation unit 26 is configured as a frequency synthesizer including a VCO 29 and a PLL unit 30, and the oscillation frequency is set by a control unit 31 via a control signal 33.

Here, for example, the local oscillation unit 26 is set to fL1
As fL2, fL1 is set to 1600 MHz and fL2 is set to 2200 MHz. The control unit 31 sets f1 (14
00 MHz), the frequency of the local oscillator 26 is set to fL1 (1600 MHz) and the tunable filter 1
Is set to f1 (1400 MHz). Similarly, when f2 (2000 MHz) is received, the frequency of the local oscillation unit 26 is changed to fL2 (2200 MHz).
z), the center frequency of the tunable filter 1 is set to f2 (200
0 MHz). That is, the frequency of the local oscillator 26 is set to be 200 MHz higher than the center frequency of the tunable filter 1.
Set higher by z. As a result, the intermediate frequency output of the mixer 25 becomes 200 MHz.

The band limiting filter 27 is, for example, a SAW filter and is a narrow band filter having a bandwidth of several MHz. The band limiting filter 27 has a center frequency of 200
MHz, and the intermediate frequency output of the mixer 25 is band-limited and input to the demodulation unit 28.

In the receiving apparatus configured as described above, generally, it is necessary to perform tracking so that the frequency interval between the local oscillator 26 and the tunable filter 1 is always constant at 200 MHz. In a conventional receiving apparatus, it is general to perform more complicated tracking adjustment by using a variable capacitance element of the VCO 29 of the local oscillation unit 26 and a variable capacitance element of the variable tuning filter 1 having uniform characteristics. It was a target. Further, the gain deviation of the entire receiving apparatus is determined by a relatively large gain deviation of the tunable filter. Further, if the center frequency of the tunable filter fluctuates, the attenuation of the interference wave frequency outside the desired frequency is deteriorated, and the interference performance is deteriorated.

However, in the receiving apparatus according to the present embodiment, the center frequency of tunable filter 1 is accurately set by control unit 31 and the gain deviation is extremely small. This eliminates the need for complicated tracking adjustment, which was conventionally required, and makes it possible to minimize the gain deviation of the entire receiving apparatus. As a result, it is possible to reduce the interference performance and the frequency deviation of the sensitivity as a whole of the receiving apparatus.

Further, in the present embodiment, the receiving apparatus has been described as an example. However, by configuring the transmitting apparatus by using the tunable filter 1, the transmitting apparatus having a small spurious performance and a small frequency deviation of the transmission output. Can be realized.

As described above, the feature of the receiving apparatus and the transmitting apparatus according to the present embodiment is that a variable tuning filter capable of setting an accurate center frequency from the outside is provided, and the center frequency and the frequency of the local oscillator are controlled. By setting at predetermined intervals from the section, tracking adjustment becomes unnecessary, and the gain deviation can be reduced.

As is apparent from the above description, according to the receiving apparatus and the transmitting apparatus of the present embodiment, the tracking adjustment becomes unnecessary, and the interference performance, the sensitivity, the spurious performance, and the frequency deviation of the transmission output can be reduced. it can.

[0072]

As is apparent from the above description, the present invention is constructed as described above, and in particular, adjusts the center frequency of the band-pass filter in response to a change in the tuning frequency of the band-pass filter, and provides gain control means. By controlling the gain of the minimum required configuration and simple adjustment,
A tunable filter that can increase the center frequency accuracy and reduce the gain deviation can be obtained.

Further, the present invention is configured as described above. In particular, since the present invention is configured using the tunable filter according to the present invention, tracking adjustment is unnecessary,
A receiving device and a transmitting device that can reduce interference performance, sensitivity, spurious performance, and frequency deviation of transmission output can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a tunable filter and an adjusting device thereof according to Embodiment 1 of the present invention;

FIG. 2 is a block diagram showing a configuration of a tunable filter and an adjusting device thereof according to a second embodiment of the present invention;

FIG. 3 is a block diagram showing a configuration of a tunable filter according to Embodiment 3 of the present invention;

FIG. 4 is a block diagram showing a configuration of a receiving device according to a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Variable tuning filter 2, 3 Band-pass filter 4 Variable gain amplifier 5, 6 D / A converter 7 CPU 8 Memory 9, 10, 32, 33 Control signal 11 Broadband noise source 12 Tuner 13, 31 Control unit 14 Signal generator 15 Broadband level detector 16 First control signal 17 Second control signal 18, 29 VCO 19, 30 PLL section 20 Limiter amplifier 21 High frequency switch 22 Broadband level detector 23, 24 Bandpass filter 25 Mixer 26 Local oscillator 27 Intermediate frequency Filter 28 Demodulation unit 35 Low noise amplifier

Continued on the front page (72) Inventor Mitsuhiro Iwamoto 2-1-1, Hikosancho, Kanazawa-shi, Ishikawa Pref. Inside Matsushita Communication Kanazawa Research Laboratories Co., Ltd. (72) Inventor Makoto Doguchi 2-1-1, Hikosancho, Kanazawa-shi, Ishikawa No. 45 F-term in Matsushita Communication Kanazawa Laboratory (reference) 5K052 AA01 BB03 BB13 DD01 EE04 EE07 EE21 FF34 GG13 GG24 GG32 GG57 5K058 AA10 AA13 AA15 BA02 CA02 DA02 EA05 EA17 GA05 GA13 GA14 GA15

Claims (9)

[Claims] A band-pass filter for changing a tuning frequency; and gain control means for changing a gain, wherein a gain of the gain control means is changed in response to a change in a tuning frequency of the band-pass filter. Characteristic variable tuning filter. 2. A band-pass filter for changing a tuning frequency by a control signal, gain control means for changing a gain by a control signal, and control signal generating means for generating a control signal to be supplied to the band-pass filter and the gain control means. Storage means for storing a control signal generated by the control signal generation means. 3. A method for adjusting a tunable filter according to claim 1, wherein a wideband noise source is connected to an input terminal, a frequency selective receiver is connected to an output terminal,
Tunable tuning means for determining a value of a control signal to be applied to the band-pass filter and the gain control means in accordance with a frequency from a result of a frequency versus detection output of the tunable filter detected by the frequency selective receiver. How to adjust the filter. 4. An adjusting method for adjusting a tunable filter according to claim 1, wherein a standard signal generator is connected to an input terminal, and a broadband level detector is connected to an output terminal. A variable tuning filter for determining a value of a control signal to be supplied to the band pass filter and the gain control means in accordance with a frequency from a result of a frequency versus detection output of the variable tuning filter detected by a wide band level detector. Adjustment method. 5. A band-pass filter for changing a tuning frequency according to first and second control signals, a frequency synthesizer for providing a first control signal to the band-pass filter, and controlling the band-pass filter and the frequency synthesizer. A second control signal generating means for generating a second control signal for changing a tuning frequency of the band-pass filter, and a wideband level detector, and receiving a local oscillation output of the frequency synthesizer. A tunable filter, wherein an output level is detected by the broadband level detector, and a tuning frequency of the bandpass filter is adjusted by the output level. 6. A gain control means for changing a gain according to a control signal, and a limiter connected to a local oscillation output of the frequency synthesizer, wherein an output level is detected by the broadband level detector, and a frequency is determined by the output level. 6. The tunable filter according to claim 5, wherein the gain characteristic is self-adjusted. 7. A filter according to claim 1, wherein a band rejection filter is used as a filter for changing a tuning frequency.
7. The tunable filter according to 5 or 6. 8. A receiver comprising the tunable filter according to claim 1, 2, 5, 6, or 7, or using the tunable filter adjusting method according to claim 3. . 9. A transmission apparatus comprising the tunable filter according to claim 1, 2, 5, 6, or 7, or using the tunable filter adjustment method according to claim 3. .