JPH09102752A - Tuner device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tuner device which has the phase noise characteristic that is improved over a wide range for the oscillation signals of local oscillator circuits. SOLUTION: A tuner device is provided with a local oscillator circuit 17 of a low oscillation frequency band and a local oscillator circuit 18 of a high oscillation frequency band. Then both circuits 17 and 18 are switched to each other based on a desired signal (channel selection signal), so that the oscillation sensitivity is kept almost at a low level against the control voltage regardless of the oscillation band. As a result, the almost fixed and satisfactory phase noise characteristic is secured in all oscillation bands. Furthermore, the tuning voltage of a variable tuning filter 3 is supplied independently of the control voltage of both circuits 17 and 18. As a result, the satisfactory tracking characteristic is secured for the filter 3 and both circuits 17 and 18 respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a terrestrial system, a satellite system,
The present invention relates to a tuner device that receives a digitally modulated high frequency signal broadcast in a CATV system.

[0002]

2. Description of the Related Art Currently, as domestic TV broadcasting, terrestrial TV broadcasting by an analog modulation system, 12 GHz band satellite broadcasting and the like are carried out. In the future, 12 GHz or 21
QPSK (Quadriph) by broadcasting satellite of GHz band
Digital TV broadcasting using the asase shift keying modulation scheme is also planned. TV like this
In the tuner section of the broadcast receiving apparatus, a variable tuning filter for removing an interfering wave and a local oscillation circuit for selecting a desired signal are used.

The configuration of a tuner section of a general satellite TV broadcast receiving apparatus is described in TV Technical Report, Vol. 17, N
o. 46, PP. 19-24 (Aug. 1993) "Development of Broadband Low Voltage Front End for Satellite Broadcasting". The variable tuning filter (tuning frequency f0) and the local oscillation circuit (oscillation frequency f1) are controlled by the control voltage from the PLL tuning circuit so that the relationship of f1−f0 = fi (fi: intermediate frequency) is maintained. Track.

The reception frequency range is as wide as about 1 GHz, and a wide band variable local oscillation circuit is constructed by a single circuit.
The modulation method of the received signal is an analog method, and the general P
Phase noise characteristics of LL control local oscillation circuit (for example, oscillation frequency fosc = 2 GHz, offset frequency 1 from fosc)
Phase noise at 0 KHz is about −65 dBc / Hz), and hardly affects the demodulation characteristics.

[0005]

By the way, in the TV broadcasting by the analog modulation system, the phase noise of the local oscillation circuit hardly affects the demodulation characteristics, but in the TV broadcasting by the digital modulation system which is scheduled to start in the future. Since the phase noise affects the demodulation characteristics, reducing the phase noise of the oscillation signal of the local oscillation circuit for tuning used in the tuner is an important issue.

The phase noise of the local oscillation circuit of the PLL control is the phase noise of the reference oscillator for phase comparison, the PLL
It is determined by the noise of the loop, the bandwidth of the PLL loop, the loop gain of the PLL loop, the oscillation sensitivity of the local oscillation circuit, and the like. Hereinafter, the phase noise will be briefly analyzed, and the effective means for reducing the phase noise will be considered.

FIG. 15 shows a general P used in a tuner.
The equivalent circuit of a LL channel selection circuit is shown. In FIG. 15, 10
1 is a local oscillator circuit, 103 is a frequency divider, 109 is a phase detector, 105 is a reference oscillator, 107 is a frequency divider, 113 is a noise generator, 115 is a loop amplifier, 117 is a loop filter.

The operation of the tuning circuit will be described below.
The local oscillation circuit 101 is a voltage control type oscillation circuit, and changes the load reactance value with a control voltage to perform frequency control. The frequency modulation sensitivity of the local oscillator circuit 101 is set to Δω (r
ad / sec / V), phase modulation sensitivity Δφ (rad /
V), these relationships can be expressed as Δω = dΔφ / dt or Δφ = Δω · t (...) (1) as in the following equation (1).

Now, the oscillation angular frequency of the local oscillator circuit is ω1
(Rad / sec), the control voltage is Vcon (v), and the phase is φ1, the oscillation signal 102 (fosc) is fosc = cos {(ω1 + Δω · Vcon) · t + φ1} = cos as shown in the following equation (2). It can be expressed as {(ω1 + dΔφ / dt · Vcon) · t + φ1} = cos {ω1 · t + (φ1 + Δφ · Vcon)} ... (2).

Here, the control voltage Vcon = 0 as an initial value.
Then, the equation (2) becomes the following equation (3). fosc = cos (ω1t + φ1) (3) Further, the oscillation signal fref of the reference oscillator 105 is fref = (1), where ω1 is the oscillation angular frequency and φ0 is the phase. cos (ω0 · t + φ0) ……………… (4).

The output signals of local oscillator circuit 101 and reference oscillator 105 are frequency-divided by frequency dividers 103 and 107, respectively, and phase-compared by phase comparator 109. Frequency divider 103
The output signal 104 (fosc) of (1 / N) is given by the following equation (5).
Given by fosc = cos (ω1t / N + φ1 / N) (5) Also, the output signal 108 (fre of the frequency divider 107 (1 / M)
f) is expressed by the following equation (6): fref = cos (ω0 · t / M + φ0 / M) ... (6)

Detection output signal 110 of the phase detector 109
(Vdet) is as follows. Vdet = fosc · fref = [cos {(ω0 / M + ω1 / N) · t + φ0 / M + φ1 / N} + cos {(ω0 / M−ω1 / N) · t + φ0 / M−φ1 / N}] ………… ( 7) Assuming that the first term of the equation (7) is deleted by the loop filter 117, Vdet = cos {(ω0 / M-ω1 / N) · t + φ0 / M-φ1 / N} ……………… (8)

The noise generated by the noise generator 113 is
(T) (noise component generated in the PLL loop), the loop gain of the loop amplifier 117 is k, and the transfer function of the loop filter is L, the control voltage (Vcon) applied to the local oscillation circuit 101 is expressed by the following equation (9). ) Is given. Vcon = K ・ L ・ cos {(ω0 / M-ω1 / N) ・ t + φ0 / M-φ1 / N} + K ・ L ・ n (t) ... (9) For simplicity, the frequency synchronization condition is now If it holds, the following expression (10) holds. ω0 / M−ω1 / N = 0 That is, ω1 = N / M · ω0 ………… (10) In the phase synchronization process, the phase of φ0 / M−φ1 / N is near π / 2. (9), the following equation (1)
As in 1), Vcon = K · L · {π / 2− (φ0 / M−φ1 / N)} + K · L · n (t) ... (11)

Further, from the expressions (2) and (11), the oscillation signal 102 (fosc) in the phase synchronization process becomes the following expression. fosc = A ・ cos [N / M ・ ω0 ・ t + {φ11 + Δφ ・ K ・ L ・ {π / 2- (φ0 / M-φ1 / N)} + K ・ L ・ n (t)}] ... (12) The phase synchronization condition is that the phase difference between the local oscillation signal output 104 after frequency division and the reference oscillation signal 108 after frequency division is π / 2. The phase synchronization condition is expressed by the following equation (13). As shown, [φ1 + Δφ · K · L · {π / 2− (φ0 / M−φ1 / N)} + K · L · n (t)}] / N−φ0 / M = π / 2 (13) ).

Next, phase noise will be considered. Since the FM-type phase noise is given by the time change of the phase, (1
Equation (3) is time-differentiated to obtain the phase noise component dφ1 / dt of the local oscillation signal 102 from the following equations (14) and (15). [Dφ1 / dt-Δφ ・ K ・ L ・ {1 / M ・ dφ0 / dt-1 / N ・ dφ1 / dt} + Δφ ・ K ・ L ・ dn (t) / dt = N / M ・ dφ0 / dt ... (14) By modifying the equation (14), dφ1 / dt = N / M · dφ0 / dt + {Δφ · K · L / (1 + Δφ · K · L / N)} · dn (t) / dt ... ( 15) is obtained.

The first term of the equation (15) is the reference oscillator 105.
Is a component multiplied by the ratio N / M of the frequency divider 103 and the frequency divider 107, and the second term is a component proportional to the noise generated in the PLL loop. Generally, the second term becomes dominant, so it is necessary to make the second term sufficiently small.

Normally, the frequency division ratio N is sufficiently large, so that the second
The coefficient of the term is given by Δφ · K · L. Therefore, the noise component generated in the PLL loop of the second term is the phase modulation sensitivity,
Proportional to the bandwidth of the loop gain filter, Δφ,
Phase noise can be reduced by reducing K and L.

Δφ · K · L is the total gain of the PLL loop, and is an amount that also affects the synchronization stability and the synchronization establishment time of the PLL loop. Therefore, it is necessary to reduce Δφ, K, and L taking these characteristics into consideration.

However, as shown in FIG. 16, the oscillation frequency characteristic of a general oscillation circuit used in a wide band receiver has a high oscillation sensitivity on the low control voltage side and, on the contrary, an oscillation sensitivity on the high control voltage side. Will be lower. Therefore, PLL
The total gain of the loop Δφ ・ K ・ L must be designed with reference to the side with low oscillation sensitivity, and the PLL with high oscillation sensitivity is used.
The total gain of the loop Δφ ・ K ・ L becomes too large, and
The characteristic deteriorates as shown by the phase noise characteristic of No. 7.

It is an object of the present invention to realize a tuner device in which the phase noise characteristic of the oscillation signal of the local oscillation circuit is improved over a wide band.

[0021]

[Means for Solving the Problems] Considering the above points,
In order to reduce the phase noise in the wide band receiver, the following three items can be considered. (1) In order to reduce the oscillation sensitivity and keep the oscillation sensitivity almost constant over the entire oscillation band, a plurality of local oscillation circuits are provided and switched and used. At this time, depending on the setting of the oscillation frequency of each local oscillation circuit, tracking with the single variable tuning filter cannot be achieved.Therefore, the tuning voltage of the variable tuning filter must be given independently of the control voltage of the local oscillation circuit. is there.

(2) The loop gain of the loop amplifier is switched between the high oscillation sensitivity side and the low oscillation sensitivity side of the local oscillation circuit.

(3) The bandwidth of the loop filter is switched between the high oscillation sensitivity side and the low oscillation sensitivity side of the local oscillation circuit.

By providing a plurality of local oscillators and switching between them, the oscillation sensitivity can be lowered and the oscillation sensitivity can be made substantially constant over the entire oscillation band. As a result, the total gain Δφ · K · L of the PLL loop can be set small, so that the phase noise characteristic can be improved over a wide band.

Further, by switching the loop gain of the loop amplifier or the bandwidth of the loop filter between the side having high oscillation sensitivity and the side having low oscillation sensitivity, the total gain Δφ of the PLL loop is obtained.
-Because K and L can be set small, it is possible to improve phase noise characteristics over a wide band. Therefore, the present invention is configured as follows to achieve the above object. The center frequency of the pass band is continuously variable according to the supplied tuning voltage, and the tuning signal that passes the tuning signal from the frequency band of the reception signal and the tuning signal that has passed the tuning filter are selected. A mixer circuit for selecting a signal, a plurality of local oscillation circuits that have different oscillation frequency bands and supply an oscillating signal to the mixer circuit, and a control voltage that is supplied to the plurality of local oscillation circuits to generate an oscillation signal. The phase-locking control circuit that controls the frequency and the tuning voltage that is supplied to the variable tuning filter according to the tuning signal are controlled, and the signal of the frequency band corresponding to the tuning signal is selected from the multiple local oscillation circuits. An operation control unit that selects a local oscillation circuit to oscillate and supplies an oscillation signal from the selected local oscillation circuit to the mixer circuit.

Preferably, in the above tuner device,
The plurality of local oscillation circuits oscillate signals of different frequencies with respect to the same control voltage from the phase synchronization control circuit, and part of continuous frequency bands overlap each other. Also,
Preferably, in the tuner device, the control voltage of the local oscillation circuit and the tuning voltage of the variable tuning filter are set independently.

Further, preferably, in the tuner device, the tuning voltage of the variable tuning filter is generated from the control voltage supplied to the plurality of local oscillation circuits. Further, preferably, in the tuner device, the plurality of local oscillation circuits output signals in different frequency bands in accordance with the control voltage from the phase synchronization control circuit, and some of continuous frequency bands are different from each other. The oscillation frequency is varied within the control voltage range, and part of the control voltage and part of the oscillation frequency overlap. Further, preferably, in the tuner device, the control voltage of the plurality of local oscillation circuits and the control voltage of the variable tuning filter are the same.

Further, the center frequency of the pass band is continuously variable according to the supplied tuning voltage, and the variable tuning filter for passing the tuning signal from the frequency band of the received signal and the variable tuning filter for passing the tuning signal are passed. A mixer circuit for selecting a tuning signal from a received signal, a local oscillation circuit for supplying an oscillating signal to the mixer circuit, and first and second loop amplifiers having mutually different gains are provided in the local oscillation circuit. A control voltage is supplied to control the frequency of the oscillation signal,
A phase synchronization control circuit that generates a tuning voltage to be supplied to the variable tuning filter based on the control voltage, and an operation control unit that switches the first and second loop amplifiers according to the tuning signal are provided.

Further, the center frequency of the pass band is continuously variable according to the supplied tuning voltage, and the variable tuning filter for passing the tuning signal from the frequency band of the received signal and the variable tuning filter for passing the tuning signal are passed. A mixer circuit for selecting a tuning signal from the received signal, a local oscillation circuit that supplies an oscillating signal to the mixer circuit, and a variable gain loop amplifier whose gain is variable, and the local oscillation circuit has a control voltage. To control the frequency of the oscillating signal and to generate the tuning voltage to be supplied to the variable tuning filter based on the control voltage, and the gain of the variable gain loop amplifier according to the tuning signal. And an operation control means for changing the operation.

In addition, the center frequency of the pass band is continuously variable according to the supplied tuning voltage, and the variable tuning filter that passes the tuning signal from the frequency band of the received signal and the variable tuning filter that passes the tuning signal are passed. A mixer circuit for selecting a tuning signal from a received signal, a local oscillation circuit for supplying an oscillating signal to the mixer circuit, and first and second loop filters having different bandwidths, respectively. A phase synchronization control circuit that supplies a control voltage to the circuit to control the frequency of the oscillation signal and that generates a tuning voltage to be supplied to the variable tuning filter based on the control voltage; And an operation control means for switching the second loop filter.

Further, the center frequency of the pass band is continuously variable according to the supplied tuning voltage, and the variable tuning filter for passing the tuning signal from the frequency band of the received signal and the variable tuning filter for passing the tuning signal are passed. It has a mixer circuit for selecting a tuning signal from the received signal, a local oscillation circuit that supplies an oscillating signal to the mixer circuit, and a bandwidth variable loop filter that can change its bandwidth, and controls the local oscillation circuit. A phase-locked control circuit that supplies a voltage to control the frequency of the oscillating signal, and that generates a tuning voltage to be supplied to the variable tuning filter based on the control voltage, and a bandwidth variable loop filter And operation control means for switching the bandwidth.

Preferably, in the above tuner device,
A quadrature detection circuit that quadrature-detects the output signal from the mixer circuit and outputs two signals of an in-phase component signal and a quadrature-component signal is provided. Preferably, in the tuner device, the tuning voltage of the variable tuning filter is generated from a control voltage supplied to a plurality of local oscillation circuits, and the phase synchronization control circuit includes a variable gain loop amplifier whose gain is variable. A control voltage is supplied to the local oscillation circuit to control the frequency of the oscillation signal, and the operation control means changes the gain of the variable gain loop amplifier according to the tuning signal.

Further, preferably, in the tuner device, the tuning voltage of the variable tuning filter is generated from a control voltage supplied to a plurality of local oscillation circuits, and the phase synchronization control circuit has a bandwidth capable of varying its bandwidth. The operation control means has a variable loop filter, and switches the bandwidth of the bandwidth variable loop filter according to the channel selection signal.

[0034]

1 is a schematic configuration diagram of a tuner device according to a first embodiment of the present invention. In the example of FIG. 1, a digitally modulated high frequency signal is received, detected, and converted into two orthogonal signals of an I (Inphase, in-phase component) signal and a Q (Quad phase, quadrature component) signal in a substantially baseband band. FIG. 3 is a block diagram of a quadrature detection tuner.

In FIG. 1, reference numeral 1 is a high-frequency signal input terminal, for example, 1.0 to 2.
A carrier wave signal of about 0 GHz is input to the input terminal 1. The input signal input from the input terminal 1 is amplified by the high frequency amplifier circuit 2, the interfering wave such as the image signal is removed by the variable tuning filter 3, and the desired signal (channel selection signal) is selected. The output signal of the variable tuning filter 3 is input to the mixer circuit 5 after gain control by the gain control amplifier circuit 4.

In the mixer circuit 5, the local oscillator circuits 17 and 18
The oscillation signal from either one of the two is mixed with the desired reception signal, and an intermediate frequency signal (hereinafter abbreviated as IF signal.
The signal is, for example, 479.5 in the case of a satellite broadcasting receiver.
MHz) and output. Local oscillation circuit 1
7 and 18 are switching signals 20 from the switching circuit 19.
Whichever is better, either one is selected.

The IF signal from the mixer circuit 5 is input to the quadrature detection unit 70 via the gain control amplifier circuit 6, the IF filter 7 and the IF amplifier circuit 8. The quadrature detection unit 70
The IF signal is quadrature-detected and I (In
phase) and Q (Quadphase) orthogonal 2
The mixer circuit 9 and 10 for converting into a signal, the oscillating circuit 11 for quadrature detection, the 90-degree phase shifter 12, and the baseband amplification circuits 13 and 14, and the output terminal 1 for I and Q signals
5 and 16 output I and Q signals, respectively. The I and Q signals output from the output terminals 15 and 16 are supplied to a digital demodulation circuit (not shown).

The operation of the PLL (phase control) channel selection circuit will be described in detail below. The local oscillator circuits 17 and 18 are
The frequency is controlled by the PLL synthesizer method described below. That is, the oscillation signals from the local oscillator circuits 17 and 18 are divided into 1 / n by the frequency divider 21 and 1 / n by the frequency divider 23.
The phase of the reference oscillation signal from the reference oscillator 22 divided into m is compared by the phase comparator 24. The error signal output from the phase comparator 24 passes through the loop amplifier 25, the control voltage generation circuit 47, and the loop filter 26, and then the local oscillation circuit 1
It is fed back to 7 and 18 to control the oscillation frequency.

The control voltage generating circuit 47 includes the loop amplifier 2
5 is a circuit for converting the error signal from 5 into a local oscillation circuit control voltage by using a fixed voltage for tuning (Vtmax, for example, 20V) applied from the terminal 32.
Generates control voltage up to ax. In this PLL synthesizer system, the frequency division ratio of the frequency dividers 21 and 23 is determined by the mixer circuit 5
Data 3 supplied from a microcomputer (operation control means) 29 according to a desired signal (channel selection signal) received by
Set by 0. And the set frequency divider 2
The frequency division ratio of 1 and 23 sets the oscillation frequency of the local oscillator circuits 17 and 18. Further, the switching circuit 19 selects the local oscillation circuit 17 or 18 by the data 30 from the microcomputer 29 according to the desired signal received by the mixer 5.

The respective oscillation bands and phase noises of the local oscillator circuits 17 and 18 will be described with reference to FIGS. 2 and 3. A general oscillation frequency characteristic of the wideband signal receiver is shown by a broken line in FIG. The oscillation frequency curve 48 shown by this broken line is obtained by using a single local oscillation circuit and controlling voltage 0
This is a characteristic when oscillating signals in the entire oscillation frequency band fosc0 to foscmax at ˜Vtmax.

In this case, the control voltage Vt changes from 0 to Vtmi.
The oscillation sensitivity is high up to d, and the oscillation sensitivity is low when the control voltage Vt is Vtmid or higher. Therefore, the phase noise is
As indicated by a broken line 51 in FIG. 3, the oscillation frequency f is
The phase noise characteristic is not good up to foscmid, and foscmax
The phase noise characteristic is improved as is approached.

Therefore, in the present invention, in order to obtain a good phase noise characteristic in the entire oscillation band, the characteristics of the oscillation frequency curves 49 and 50 shown by the solid lines in FIG. 2 are obtained by using the local oscillation circuits 17 and 18. To do. This is because when the local oscillation circuit 17 is selected by the switching circuit 19, the control voltage is 0 to Vtm.
When a local oscillation circuit 18 is selected by the switching circuit 19, an oscillation band on the low side of fosc0 to foscmid is obtained by ax, and an oscillation band on the high side of foscmid to foscmax is obtained with the control voltage 0 to Vtmax.

In this case, each local oscillator circuit 17,
By obtaining the oscillation signal using the entire range of the control voltage 0 to Vtmax as the control voltage of 18, the oscillation sensitivity can be kept low and kept substantially constant. Therefore, as the phase noise characteristic, a good characteristic that is substantially constant over the entire oscillation band can be obtained as shown by a curve 52 shown by a solid line in FIG.

In this example, it is assumed that the low frequency band and the high frequency band partially overlap. For example, fosc0 is 1.3 GHz, foscmid
Is 2 GHz and foscmax is 2.7 GHz, the lower frequency band fosc0 to foscmid is 1.3 GHz to 2.
1 GHz, the higher frequency band is 1.9 GHz to 2
7. GHz.

Next, the tuning voltage for controlling the tuning frequency of the variable tuning filter 3 will be described. The frequency of the desired signal received by the mixer circuit 5 is fin, the local oscillator circuits 17 and 1
8 is the oscillation frequency of fosc, and I is output from the mixer circuit 5.
When the frequency of the F signal is fif, the relationship of the following expression (16) is established. fosc = fin + fif (16) Therefore, the tuning frequency ftun of the variable tuning filter 3 (which is almost the same as the frequency fin of the desired signal) should be tracked so that the relationship between the oscillation frequency fosc and the equation (16) holds. It is necessary to use the control voltage of the local oscillation circuits 17 and 18 as the tuning voltage of the variable tuning filter 3 in a general receiving device.

However, in this example, the local oscillation circuit 1
Since 7 and 18 are switched and the entire range of the control voltage 0 to Vtmax is used for controlling the oscillation frequency of each local oscillation circuit, the local oscillation circuit 1 is included in the variable tuning filter 3.
In order to use the control voltages of 7 and 18 for tracking, it is necessary to provide two variable tuning filters 3 similarly to the local oscillation circuits 17 and 18 and switch them.

However, if two variable tuning filters are provided and they are switched, the configuration becomes complicated. Therefore, the tuning voltage of the variable tuning filter 3 is independent of the control voltage of the local oscillation circuits 17 and 18. It was configured to apply. That is, the data 30 from the microcomputer 29 is input to the tuning voltage generating circuit 31 according to the desired signal received by the mixer circuit 5, and the tuning voltage 33 from the fixed tuning voltage applied from the terminal 32 to the tuning voltage generating circuit 31. Is generated and applied to the variable tuning circuit 3 to control the tuning frequency ftun.

For example, the tuning voltage generating circuit 31 has a plurality of resistors connected in series to which a fixed voltage for tuning is supplied, a plurality of terminals for taking out a voltage between the plurality of resistors, and a plurality of terminals among the plurality of terminals. It is configured by a switch that selects one of them. Then, in accordance with the desired signal (channel selection signal), the switch is switched by the data 30 to generate an appropriate tuning voltage 33.

As described above, according to the first embodiment of the present invention, the local oscillator circuit 17 having a low oscillation frequency band and the local oscillator circuit 18 having a high oscillation frequency band are provided, and a desired signal (channel selection signal) is provided. These local oscillator circuits 17 and 1
By switching between No. 8 and No. 8, it is possible to set the oscillation sensitivity to the control voltage to be low and to keep it substantially constant regardless of the oscillation band. As a result, there is an effect that a good phase noise characteristic that is substantially constant over the entire oscillation band can be obtained.

The tuning voltage of the variable tuning filter 3 is
Since the control voltage of the local oscillation circuits 17 and 18 is applied independently, the variable tuning filter 3 and the local oscillation circuits 17 and 1 are supplied.
8 has the effect of obtaining good tracking characteristics.

FIG. 4 is a schematic configuration diagram of a tuner device according to a second embodiment of the present invention. In the second embodiment, the same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. In the second embodiment, the control voltage of the local oscillator circuits 17 and 18 is used as the tuning voltage of the variable tuning filter 3 in the first embodiment. That is, the data 30 from the microcomputer 29 according to the desired signal received by the mixer circuit 5
Are supplied to the tuning voltage generating circuit 28. And terminal 3
The tuning voltage 33 is generated from the fixed tuning voltage applied to the tuning voltage generating circuit 28 from 2 and the control voltage 27 of the local oscillation circuits 17 and 18. The generated tuning voltage 33 is applied to the variable tuning circuit 3, and the variable tuning circuit 3 controls the tuning frequency ftun according to the applied tuning voltage 33.

A circuit example of the tuning voltage generating circuit 28 is shown in FIG. In FIG. 5, a fixed tuning voltage 32 applied from a terminal 32 is supplied to a plurality of resistors 43, 44, 4 connected in series.
Divided by 5 and 46, midpoint (connection point between resistors 44 and 45)
A local oscillation circuit control voltage 27 is applied to the. Resistors 43 and 4
Terminal 56 and resistors 45 and 46 connected to the connection point with
The terminal 57 connected to the connection point with is used as a tuning voltage output terminal, and one of the output terminals 56 or 57 is selected according to the data 30 from the microcomputer 29 to be the tuning voltage 33 of the variable tuning filter 3.

When the local oscillator circuit 17 is selected, the terminal 57 is selected by the data 30 from the microcomputer 29, and when the local oscillator circuit 18 is selected,
The terminal 56 is selected by the data 30 from the microcomputer 29. The relationship between the control voltage 27 of the local oscillator circuits 17 and 18 and the filter tuning voltage 33 is shown in FIG. When the local oscillation circuit 17 is selected, a voltage having the characteristic indicated by the straight line 59 is output from the terminal 57, and when the local oscillation circuit 18 is selected, the voltage having the characteristic indicated by the straight line 58 is output from the terminal 56. With the tuning voltage generating circuit 28 shown in FIG. 5, the control voltage 27 is changed to the filter tuning voltage 3 with a simple configuration.
3 can be obtained.

As described above, according to the second embodiment of the present invention, the same effect as that of the first embodiment can be obtained. Further, according to the second embodiment, the tuning voltage 33 of the variable tuning filter 3 is configured to be generated by using the control voltage 27 of the local oscillation circuits 17 and 18, so that the tuning voltage generating circuit 28 is provided. In addition to being realized with a simple configuration, good tracking characteristics of the variable tuning filter 3 and the local oscillation circuits 17 and 18 can be obtained.

FIG. 7 is a schematic configuration diagram of a tuner device according to a third embodiment of the present invention. In the third embodiment, the same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. In the third embodiment, the oscillation bands of the local oscillation circuits 17 and 18 are different from those of the local oscillation circuits 17 and 18 in the first embodiment. Further, in the third embodiment, the control voltage of the local oscillation circuits 17 and 18 is used as it is as the tuning voltage of the variable tuning filter 3.
That is, the voltage from the control voltage generation circuit 47 is supplied to the oscillation circuits 17 and 18 via the loop filter 26 and also to the applied variable tuning filter 3.

As shown in FIG. 8, local oscillator circuits 17 and 1 are provided.
8 is used to obtain the characteristics of the oscillation frequency curves 53 and 54. This is because the switching circuit 19 uses the local oscillation circuit 1
When 7 is selected, the control voltage is 0 to Vtmid and fosc0 to
When the oscillating band of foscmid is obtained and the local oscillating circuit 18 is selected by the switching circuit 19, the control voltages Vtmid to Vtmax are obtained.
To obtain an oscillation band of foscmid to foscmax.

That is, the oscillation bands of the two local oscillation circuits 17 and 18 are set so as to increase substantially continuously with respect to the control voltage 27. By selecting the oscillation band in this way, the oscillation sensitivity can be lowered in a particularly low oscillation band, as compared with the case of oscillating with a single local oscillation circuit. Therefore, as shown by the solid line 55 in FIG. 9, a good phase noise characteristic that is substantially constant over the entire oscillation band can be obtained.

As described above, according to the third embodiment of the present invention, the oscillation bands of the local oscillation circuits 17 and 18 are switched so as to continuously and linearly increase with respect to the control voltage. By setting the oscillation sensitivity to the control voltage to be low, the oscillation sensitivity can be kept substantially constant regardless of the oscillation band. As a result, there is an effect that a good phase noise characteristic that is substantially constant over the entire oscillation band can be obtained.

Further, by switching the oscillation bands of the local oscillator circuits 17 and 18 so as to continuously increase with respect to the control voltage, the tuning voltage 33 of the tunable filter 3 remains the control voltage 27 of the local oscillator circuit. Can be supplied by using the tunable filter 3 and the local tuning circuits 17 and 18 and good tracking characteristics can be obtained.

FIG. 10 is a schematic configuration diagram of a tuner device according to a fourth embodiment of the present invention. In the fourth embodiment, the same components as those in the first embodiment are
The same reference numerals are given and the description is omitted. The fourth embodiment is intended to improve the phase noise characteristic of the local oscillation circuit by switching the loop gain of the PLL channel selection circuit.

That is, in the fourth embodiment, the PLL
In the tuning circuit, the oscillation signal from the single local oscillation circuit 34 is supplied to the mixer circuit 5 and the frequency divider 2
1 to the phase comparator 24. Further, the oscillation signal from the reference oscillator 22 is supplied to the phase comparison circuit 24 via the frequency divider 23 and is compared in phase with the oscillation signal from the frequency divider 21. Then, the error signal output from the phase comparator 24 is supplied to the two loop amplifiers 35 and 36 connected in parallel with each other.

These two loop amplifiers 35 and 36
Is selected by the switching circuit 37 based on the data 30 from the microcomputer 29 according to the desired signal. The output signals of the loop amplifiers 35 and 36 are
It is supplied to the control voltage generation circuit 47, and the output voltage from the control voltage generation circuit 47 is supplied to the local oscillation circuit 34 and the variable tuning filter 3 via the loop filter 26.

Since the local oscillation circuit 34 is composed of a single unit, the oscillation frequency characteristic has a high oscillation sensitivity to the control voltage on the low oscillation band side and an oscillation to the control voltage on the high oscillation band side as shown in FIG. The sensitivity is low.

Therefore, two loop amplifiers 35 and 36 are provided in the PLL loop, the switching circuit 37 is controlled by the data 30 from the microcomputer 29, and a loop with a low gain is obtained on the low oscillation band side where high oscillation sensitivity can be obtained. The amplifier 35 is selected, and the loop amplifier 36 having high gain is selected on the high oscillation band side where low oscillation sensitivity is obtained. In FIG. 11, the solid line 60 shows the phase noise characteristic of this embodiment. Since the low gain loop amplifier 35 is used in the low oscillation band, the phase noise characteristic is improved.

As described above, according to the fourth embodiment of the present invention, the loop amplifier 35 or 36 having the optimum gain can be selected according to the oscillation sensitivity of the local oscillation circuit 34, so that the entire oscillation band is Almost constant, good phase noise characteristics can be obtained.

FIG. 12 is a schematic configuration diagram of a tuner device according to a fifth embodiment of the present invention. In the fifth embodiment, those equivalent to the fourth embodiment are
The same reference numerals are given and the description is omitted. Like the fourth embodiment, the fifth embodiment is intended to improve the phase noise characteristic of the local oscillation circuit 34 by switching the loop gain of the PLL tuning circuit. In place of the two loop amplifiers 35 and 36, one variable gain amplifier 36A is provided.

Since the local oscillating circuit 34A is composed of a single unit, the oscillation frequency characteristic has a high oscillation sensitivity to the control voltage on the low oscillation band side and a high oscillation sensitivity to the control voltage on the high oscillation band side as shown in FIG. It's getting low.

Therefore, the loop amplifier 36 of the PLL loop
A is a variable gain amplifier, the switching circuit 37 is controlled by the data 30 from the microcomputer 29, and the gain of the loop amplifier 36A is set low on the low oscillation band side where high oscillation sensitivity is obtained, and low oscillation sensitivity is obtained. On the high oscillation band side, the gain of the loop amplifier 36A is set high.

The phase noise characteristic of the fifth embodiment is the same as the phase noise characteristic of the line 60 shown in FIG. Since the gain of the loop amplifier 36A is reduced in the low oscillation band, the phase noise characteristic is improved.

As described above, according to the fifth embodiment, the optimum gain of the loop amplifier can be selected according to the sensitivity of the oscillation of the local oscillation circuit. There is an effect that noise characteristics can be obtained.

FIG. 13 is a schematic configuration diagram of a tuner device according to a sixth embodiment of the present invention. In the sixth embodiment, the same components as those in the first embodiment are
The same reference numerals are given and the description is omitted. The sixth embodiment is intended to improve the phase noise characteristic of the local oscillation circuit by switching the bandwidth by switching the loop filter of the PLL channel selection circuit.

That is, in the sixth embodiment, the PLL
In the tuning circuit, the oscillation signal from the single local oscillation circuit 34 is supplied to the mixer circuit 5 and the frequency divider 2
1 to the phase comparator 24. Further, the oscillation signal from the reference oscillator 22 is supplied to the phase comparison circuit 24 via the frequency divider 23 and is compared in phase with the oscillation signal from the frequency divider 21. Then, the error signal output from the phase comparator 24 is supplied to the control voltage generation circuit 47 via the loop amplifier 25. The output voltage from the control voltage generation circuit 47 is supplied to the local oscillation circuit 34 and the variable tuning filter 3 via the two loop filters 39 and 40 connected in parallel with each other.

One of the loop filters 39 and 40 is selected by a switching signal from the switching circuit 41. The switching circuit 41 uses a desired signal (channel selection signal)
The loop filters 39 and 40 are switched based on the data 30 from the microcomputer 29 according to the above.

In the example of FIG. 13, since the local oscillator circuit 34 is composed of a single unit, the oscillation frequency characteristic has a high oscillation sensitivity to the control voltage on the low oscillation band side and a high oscillation band side as shown in FIG. Therefore, the oscillation sensitivity to the control voltage is low.

Therefore, two loop filters 39 and 40 are provided in the PLL loop, the switching circuit 41 is controlled by the data 30 from the microcomputer 29, and a loop having a narrow bandwidth on the low oscillation band side where high oscillation sensitivity can be obtained. The filter 39 is selected, and the loop filter 40 having a wide bandwidth is selected on the high oscillation band side where low oscillation sensitivity is obtained.

The phase noise characteristic in the sixth embodiment is the same as the phase noise characteristic of the line 60 shown in FIG. That is, since the narrow band loop filter is used in the low oscillation band, the phase noise characteristic is improved.

As described above, according to the sixth embodiment, the optimum loop filter band of the two loop filters can be selected according to the sensitivity of the oscillation of the local oscillator circuit. A stable and good phase noise characteristic is obtained over the range.

FIG. 14 is a schematic configuration diagram of a tuner device according to a seventh embodiment of the present invention. In the seventh embodiment, as for the equivalent to the sixth embodiment,
The same reference numerals are given and the description is omitted. Similar to the sixth embodiment, the seventh embodiment is intended to improve the phase noise characteristic of the local oscillation circuit by switching the loop filter bandwidth of the PLL tuning circuit.

However, in the seventh embodiment, the sixth
Two loop filters 39 and 40 in the embodiment of
Instead, a single variable loop filter 39A is arranged. The bandwidth of the loop filter 39A is switched by the switching signal of the switching circuit 41 according to the data 30 from the microcomputer 29.

Since the local oscillating circuit 34 is composed of a single unit, the oscillation frequency characteristic has a high oscillation sensitivity to the control voltage on the low oscillation band side and an oscillation sensitivity to the control voltage on the high oscillation band side as shown in FIG. Is low.

Therefore, the loop filter 3 of the PLL loop
9A is a variable bandwidth filter, the switching circuit 41 is controlled by the data 30 from the microcomputer 29, and the bandwidth of the loop filter 39A is set narrow on the low oscillation band side where high oscillation sensitivity is obtained, and low oscillation sensitivity is obtained. On the obtained high oscillation band side, the bandwidth of the loop filter 39A is set wide.

The phase noise characteristic of the seventh embodiment is the same as the phase noise characteristic of the line 60 shown in FIG. That is, since the narrow band loop filter is used in the low oscillation band, the phase noise characteristic is improved.

As described above, according to the seventh embodiment, the optimum band of the loop filter can be selected according to the sensitivity of the oscillation of the local oscillation circuit. Phase noise characteristics can be obtained.

As an eighth embodiment of the present invention, in the second embodiment shown in FIG. 4, the loop amplifier 25 is a variable amplifier like the variable amplifier 36A shown in FIG. The gain can be switched by the data 30 from the microcomputer 29 via the switching circuit. With this configuration, there is an effect that a phase noise characteristic equal to or higher than that of the second embodiment can be obtained.

Further, as a ninth embodiment of the present invention,
In the second embodiment shown in FIG. 4, the loop filter 26 is a variable loop filter similar to the variable loop filter 39A shown in FIG. 14, and the bandwidth of this variable loop filter is the data 3 from the microcomputer 29.
With 0, switching can be performed via a switching circuit. With this configuration, there is an effect that a phase noise characteristic equal to or higher than that of the second embodiment can be obtained.

In the above embodiment, the IF
Although the output signal from the amplifier circuit 8 is configured to be supplied to the quadrature detection unit 70, it is not quadrature detection but only simple detection.
It is also possible to execute and supply to the digital demodulation circuit in the subsequent stage. That is, the mixer circuit 9, the baseband amplifier circuit 13 and the output terminal 15 are omitted from the quadrature detector 70, and the output signal of the IF amplifier circuit 8 is passed through the mixer circuit 10, the baseband amplifier circuit 14 and the terminal 16. It is also possible to supply only the obtained signal to the digital demodulation circuit.

In addition, the above-mentioned examples of FIGS. 1, 4 and 7 are as follows.
This is an example in which two local oscillation circuits are provided, but three or more local oscillation circuits having different oscillation frequency bands are provided, an appropriate oscillation circuit is selected from these, and the output signal thereof is a mixer circuit. It is also possible to configure so as to supply five.

[0088]

Since the present invention is configured as described above, it has the following effects. By providing a plurality of local oscillators and switching between them, the oscillation sensitivity can be lowered and the oscillation sensitivity can be made substantially constant over the entire oscillation band. As a result, the total gain Δ of the PLL loop
Since φ · K · L can be set small, it is possible to realize a tuner device capable of improving phase noise characteristics over a wide band.

Also, by switching the loop gain of the loop amplifier or the bandwidth of the loop filter between the side with high oscillation sensitivity and the side with low oscillation sensitivity, the total gain Δφ of the PLL loop is obtained.
Since K and L can be set small, it is possible to realize a tuner device capable of improving phase noise characteristics over a wide band.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a tuner device according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram of a local oscillator circuit according to the first embodiment of the present invention.

FIG. 3 is a characteristic diagram of phase noise in the first embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a tuner device according to a second embodiment of the present invention.

FIG. 5 is a specific configuration diagram of a tuning voltage generating circuit according to a second embodiment of the present invention.

FIG. 6 is a tuning voltage characteristic diagram of a second embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of a tuner device according to a third embodiment of the present invention.

FIG. 8 is a characteristic diagram of a local oscillator circuit according to a third embodiment of the present invention.

FIG. 9 is a characteristic diagram of phase noise according to the third embodiment of the present invention.

FIG. 10 is a schematic configuration diagram of a tuner device according to a fourth embodiment of the present invention.

FIG. 11 is a characteristic diagram of phase noise according to the fourth embodiment of the present invention.

FIG. 12 is a schematic configuration diagram of a tuner device according to a fifth embodiment of the present invention.

FIG. 13 is a schematic configuration diagram of a tuner device according to a sixth embodiment of the present invention.

FIG. 14 is a schematic configuration diagram of a tuner device according to a seventh embodiment of the present invention.

FIG. 15 is a schematic configuration diagram of a conventional PLL channel selection circuit.

FIG. 16 is a graph showing an oscillation characteristic of a conventional PLL channel selection circuit.

FIG. 17 is a graph showing a phase noise characteristic of a conventional PLL channel selection circuit.

[Explanation of symbols]

 1 High-frequency signal input terminal 3 Variable tuning filter 5, 9, 10 Mixer circuit 11 Oscillation circuit 12 90 degree phase shifter 17, 18, 34 Local oscillation circuit 19 Switching circuit 21, 23 Divider 22 Reference oscillator 24 Phase comparator 25 , 35, 36 Loop amplifier 36A Variable gain loop amplifier 26, 39, 40 Loop filter 28, 31 Tuning voltage generation circuit 29 Microcomputer 37, 41 Switching circuit 39A Bandwidth variable loop filter 47 Control voltage generation circuit 70 Quadrature detection unit

Front page continuation (72) Inventor Masaki Noda 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi, Ltd. Multimedia system development headquarters

Claims (13)

[Claims] 1. A variable tuning filter, wherein a center frequency of a pass band is continuously variable according to a tuning voltage supplied, and a tuning signal is passed from a frequency band of a received signal, and the variable tuning filter is passed. A mixer circuit for selecting a tuning signal from the received signals, a plurality of local oscillation circuits that have different oscillation frequency bands and supply an oscillating signal to the mixer circuit, and control for these multiple local oscillation circuits A phase synchronization control circuit that supplies a voltage to control the frequency of the oscillating signal and a tuning voltage that is supplied to the variable tuning filter according to the tuning signal. Operation control means for selecting a local oscillation circuit that oscillates a signal in a frequency band corresponding to the local signal and supplying an oscillation signal from the selected local oscillation circuit to the mixer circuit; Tuner apparatus comprising: a. 2. The tuner device according to claim 1,
A tuner device in which a plurality of local oscillation circuits oscillate signals of different frequencies with respect to the same control voltage from the phase synchronization control circuit, and a part of continuous frequency bands overlap each other. 3. The tuner device according to claim 1 or 2, wherein the control voltage of the local oscillation circuit and the tuning voltage of the variable tuning filter are set independently. 4. The tuner device according to claim 1 or 2, wherein the tuning voltage of the variable tuning filter is generated from a control voltage supplied to the plurality of local oscillation circuits. 5. The tuner device according to claim 1,
The plurality of local oscillation circuits output signals in different frequency bands according to the control voltage from the phase synchronization control circuit, and some of the continuous frequency bands vary the oscillation frequency in different control voltage ranges, A tuner device characterized in that part of the control voltage and part of the oscillation frequency overlap. 6. The tuner device according to claim 1 or 5, wherein the control voltage of the plurality of local oscillation circuits and the control voltage of the variable tuning filter are the same. 7. A variable tuning filter having a center frequency of a pass band continuously variable in accordance with a supplied tuning voltage and passing a tuning signal from a frequency band of a received signal, and a variable tuning filter passing through the variable tuning filter. A mixer circuit for selecting a tuning signal from the received signal, a local oscillation circuit for supplying an oscillating signal to the mixer circuit, and first and second loop amplifiers having different gains from each other A phase synchronization control circuit that supplies a control voltage to the circuit to control the frequency of the oscillating signal and that generates a tuning voltage to be supplied to the variable tuning filter based on the control voltage, and, in accordance with a tuning signal, A tuner device comprising: an operation control unit that switches between a first loop amplifier and a second loop amplifier. 8. A variable tuning filter, wherein a center frequency of a pass band is continuously variable according to a supplied tuning voltage, and a tuning signal is passed from a frequency band of a received signal, and the variable tuning filter is passed. A mixer circuit for selecting a tuning signal from the received signal, a local oscillation circuit for supplying an oscillating signal to the mixer circuit, and a variable gain loop amplifier whose gain is variable, are provided in the local oscillation circuit. A phase synchronization control circuit that supplies a control voltage to control the frequency of the oscillation signal and generates a tuning voltage to be supplied to the variable tuning filter based on the control voltage, and the variable gain according to the tuning signal. A tuner device comprising: an operation control unit that changes a gain of a loop amplifier. 9. A variable tuning filter having a center frequency of a pass band continuously variable in accordance with a supplied tuning voltage and passing a tuning signal from a frequency band of a received signal; and a variable tuning filter passing through the variable tuning filter. A mixer circuit for selecting a tuning signal from the received signal, a local oscillating circuit for supplying an oscillating signal to the mixer circuit, and first and second loop filters each having a different bandwidth, A phase synchronization control circuit that supplies a control voltage to the local oscillation circuit to control the frequency of the oscillation signal, and that generates a tuning voltage to be supplied to the variable tuning filter based on the control voltage, and in accordance with the tuning signal. A tuner device comprising: an operation control unit that switches between the first and second loop filters. 10. A variable tuning filter, wherein a center frequency of a pass band is continuously variable according to a supplied tuning voltage, and a tuning signal is passed from a frequency band of a received signal, and the variable tuning filter is passed. A mixer circuit for selecting a tuning signal from the received signal, a local oscillation circuit for supplying an oscillating signal to the mixer circuit, and a bandwidth variable loop filter capable of varying the bandwidth thereof. To control the frequency of the oscillation signal by supplying a control voltage to the variable tuning filter and to generate a tuning voltage to be supplied to the variable tuning filter based on the control voltage. A tuner device comprising: an operation control unit that switches a bandwidth of a variable width loop filter. 11. The method of claim 1, 2, 3, 4, 5, 6, 7,
8. The tuner device according to 8, 9, or 10, further comprising a quadrature detection circuit that quadrature-detects an output signal from the mixer circuit and outputs two signals of an in-phase component signal and a quadrature component signal. 12. The tuner device according to claim 1, wherein the tuning voltage of the variable tuning filter is generated from a control voltage supplied to the plurality of local oscillation circuits, and the phase synchronization control circuit has a variable gain. And controlling the frequency of the oscillation signal by supplying a control voltage to the local oscillation circuit, and the operation control means changes the gain of the variable gain loop amplifier according to the tuning signal. A tuner device characterized by: 13. The tuner device according to claim 1, wherein the tuning voltage of the variable tuning filter is generated from a control voltage supplied to the plurality of local oscillation circuits, and the phase synchronization control circuit adjusts its bandwidth. A tuner apparatus having a variable bandwidth variable loop filter, wherein the operation control means switches the bandwidth of the variable bandwidth loop filter according to a channel selection signal.