HIGH-FREQUENCY SIGNAL RECEIVER

Abstract: A high-frequency signal receiver which lightens the burden of external equipment. In the receiver, one input-output terminal group is connected to the control terminal of a PLL circuit (31), the interface circuit (28e) of a demodulating section (28), and the control terminal of a decoding section (29) and the other input-output terminal group has a microcomputer (33) connected to the external equipment. The microcomputer (33) controls at least one of the PLL circuit (31), demodulating section (28), and decoding section (29) based on a signal inputted from the other input-output terminal group. Therefore, the burden of the external equipment can be lightened.

Description: TECHNICAL FIELD The present invention relates to a high frequency signal receiving apparatus for use as digital transmission apparatus. BACKGROUND ART A prior art high frequency signal receiving apparatus is described in the following with reference to drawing. A prior art high frequency signal receiving apparatus shown in Fig.4 comprises an input terminal 1 for receiving digital modulated high frequency signal, a high frequency amplifier 2 coupled to the input terminal1, a mixer 4 one input of which being coupled to output of the high frequency amplifier 2 while other input being coupled to output of a local oscillator 3, an I/Q detector 6 one input of which being coupled to output of the mixer 4 while other input being coupled to output of a local oscillator 5, an A/D converter 7 coupled to output of the I/Q detector 6, a demodulator 8a which being part of a digital signal demodulating section 8 and coupled to output of the A/D converter 7, a frequency error detector 8b provided within the demodulating section 8, a D/A converter 8d provided between the frequency error detector 8b and said local oscillator 5, a digital signal decoding section 9 coupled to output of said demodulator 8, an output terminal 10 coupled to output of the decoding section 9, a PLL circuit 11 coupled to said local oscillator 3, a PLL circuit control terminal 12 coupled to control input of the PLL circuit 11, a demodulating section control terminal 13 coupled to an interface circuit 8e which circuit being control input of said demodulating section 8, and a decoding section control terminal 14 coupled to control input of said decoding section 9. The operation of the above high frequency signal receiving apparatus is described in the following. A digital modulated high frequency signal inputted to input terminal 1 is amplified at high frequency amplifier 2, mixed at the mixer 4 with an output frequency from the local oscillator 3, and a desired high frequency signal is tuned. This is converted at A/D converter 7 into digital value after quadrature detection by I/Q detector 6, and delivered to demodulator 8a. In the demodulator 8a, digital signal is demodulated. An oscillation frequency of around 479.5MHz for the I/Q detection is obtained at local oscillator 5 by inputting the output of frequency error detector 8b to the local oscillator 5 after D/A conversion at D/A converter 8d. Thus the demodulating section 8 reduces the frequency error by the feedback, also reproduces clock in a clock recovery circuit 8c. The digital demodulation is performed accurately using the reproduced clock. Output of the demodulator 8a is delivered to output terminal 10 after undergoing error correction, etc. at decoding section 9. In the above described conventional structure, however, the PLL circuit control terminal 12, demodulating section control terminal 13 and decoding section control terminal 14 are connected respectively direct to outside equipments. For example, the PLL circuit control terminal 12 of PLL circuit 11 receives signal for tuning clock signal, data signal, in able signal, etc. direct from outside equipment. The PLL circuit 11 need to be provided with a one which is different depending on destination market. Demodulating section 8 needs to be provided with roll-off factor, data for specifying difference of tuner specification, frequency dividing rate, transmission rate, etc. through the demodulating section control terminal 13 in a format specific to the demodulating section 8. Decoding section 9 needs to be provided with specific information for error correction represented by, for example, Reed-Solomon, Viterbi decode, etc. through decoding section control terminal 14. As described above, the prior art constitution requires specific control for each of the terminals, such a control in an outside equipment is quite complicated, which may lead to a delayed processing in the main function of the outside equipment, posing a heavy burden on the outside equipment. DISCLOSURE OF THE INVENTION To address the problem, the present invention presents a high frequency signal receiving apparatus with which the burden of the outside equipment is alleviated. The invented high frequency signal receiving apparatus comprises a microcomputer, one group of input/output terminals of which being coupled to control terminal of PLL circuit, control terminal of demodulating section and control terminal of decoding section, while other group of input/output terminals to outside equipment; which microcomputer is controlled based on an oscillation frequency generated from a fixed oscillation element, at the same time, the microcomputer controls, based on a signal delivered from outside equipment inputted through said other group of input/output terminals, at least any one among said PLL circuit, said demodulating section and said decoding section. With the above described constitution, the burden of the outside equipment may be alleviated. BRIEF DESCRIPTION OF THE DRAWINGS Fig,1 is a block diagram of a high frequency signal receiving apparatus in accordance with an exemplary embodiment of the present invention. Fig.2 is a block diagram used for explaining the structure of bus line of Fig.1. Fig.3 shows a side view of the high frequency signal receiving apparatus of Fig.1. Fig.4 is a block diagram of a prior art high frequency signal receiving apparatus. BEST MODE FOR CARRYING OUT THE INVENTION A high frequency signal receiving apparatus in accordance with the present invention recited in Claim 1 comprises an input terminal for receiving digital modulated high frequency signal, a mixer one input of which being supplied with the signal inputted in the input terminal while other input being coupled to output of a local oscillator, a digital signal demodulating section to which the output of mixer being supplied, a digital signal decoding section to which the output of demodulating section being supplied, an output terminal coupled to the output of the decoding section, a PLL circuit coupled to said local oscillator, and a microcomputer, one group of input/output terminals of which being coupled to control terminal of said PLL circuit, control terminal of said demodulating section and control terminal of said decoding section, while other group of input/output terminals to outside equipment. The microcomputer is controlled based on an oscillation frequency generated from a fixed oscillation element, at the same time, the microcomputer controls, based on a signal delivered from outside equipment inputted through said other group of input/output terminals, at least any one among said PLL circuit, said demodulating section and said decoding section. As the apparatus is provided with a microcomputer having one group of input/output terminals which is coupled to control terminal of PLL circuit, control terminal of demodulating section and control terminal of decoding section, while other group of input/output terminals coupled to outside equipment, the outside equipment may simply issue a command to the microcomputer, and then the microcomputer controls said PLL circuit, said demodulating section, said decoding section based on the command delivered from the outside equipment. Therefore, the burden of outside equipment is significantly alleviated. The control line from outside equipment may be connected only with a microcomputer, which means a simplified connection work and an eliminated interference among control lines. Furthermore, designing of the outside equipment may turn out to be easy. An invented high frequency signal receiving apparatus recited in Claims 2, 8 and 14 uses a frequency of fixed oscillation element outputted from microcomputer as the reference oscillation frequency of PLL circuit. Thus a fixed oscillation element is shared in common by the microcomputer and the PLL circuit, which may contribute to making a high frequency signal receiving apparatus smaller and less expensive. An invented high frequency signal receiving apparatus recited in Claims 3, 9 and 15 comprises a microcomputer, within whose ROM a plurality of types of instruction information for at least any one of PLL circuit, demodulating section and decoding section are stored. Any desired information among the plurality of types of instruction information may be selected freely from the outside. So, one microcomputer may be used for different applications each having its own specification, for example, for reception of CATV broadcast, reception of BS broadcast, etc. This helps reduce the cost of microcomputer through volume production. In an invented high frequency signal receiving apparatus recited in Claims 4, 10 and 16, at least mixer and local oscillator are shielded from the other circuits. As the mixer and the local oscillator, both being the high frequency circuits, are shielded from the other circuits, there is least possibility of picking up digital noise. Also, there is least possibility for the local oscillator to affect outside equipment with the leaking oscillation frequency. In an invented high frequency signal receiving apparatus recited in Claims 5, 11 and 17, a mixer, a local oscillator and a PLL circuit are housed in a first metal case, while a demodulating section, a decoding section and a microcomputer are housed in a second metal case. Each of the first and the second cases forming an entity of independent function, therefore each of these may be sold or controlled separately. Furthermore, as the size of each case is smaller as compared with a single integrated case the freedom in mounting on a mother substrate may increase. In an invented high frequency signal receiving apparatus recited in Claims 6, 12 and 18, an outside equipment and a microcomputer communicate to each other confirming the exchange of signal after every one unit of information. As the microcomputer performs its operation confirming the exchange of signal with an outside equipment, an error-free control may be expected. Also, it is possible for an outside equipment to take an appropriate countermeasure when some failure is detected with the high frequency receiving apparatus. In an invented high frequency signal receiving apparatus recited in Claim 7, a first control line connecting a microcomputer with a PLL circuit is a connection line that is different from a second connection line connecting said microcomputer to a demodulating section or a decoding section. As the PLL circuit is separated from the demodulating section or the decoding section, the mutual interference may not take place, and a control signal for controlling the demodulating section or the decoding section may not be mixed into the PLL circuit, so no increase of phase noise of local oscillator. An invented high frequency signal receiving apparatus recited in Claim 13 comprises an I/Q detector provided between a mixer and a demodulating section, containing a second local oscillator. The second local oscillator is controlled by an error signal outputted from a frequency error detecting circuit provided within said demodulating section, and the microcomputer controls the demodulating section so as the output pulse counts of the second local oscillator reaches a certain predetermined number within a certain predetermined time span. As the oscillation frequency of second local oscillator is under surveilance of microcomputer, the accuracy is equal to that of a fixed oscillation element of the microcomputer. Therefore, with respect to drift by humidity in the second local oscillating section, the second local oscillator does not need to employ an expensive item such as dielectric resonator. This helps implement an inexpensive high frequency signal receiving apparatus. Now in the following, an embodiment according to the present invention is described referring to drawings. An invented high frequency signal receiving apparatus comprises, as shown in Fig.1, an input terminal 21 for receiving digital modulated high frequency signal, a high frequency amplifier 22 coupled to the input terminal 21, a mixer 24 one input of which being coupled to output of the high frequency amplifier 22 while other input being coupled to output of a local oscillator 23, an I/Q detector 26 one input of which being coupled to output of the mixer 24 while other input being coupled to output of a local oscillator 25, an A/D converter 27 coupled to output of the I/Q detector 26, a digital signal demodulating section 28 coupled to the output of A/D converter 27, a demodulator 28a and a frequency error detector 28bboth provided within the demodulating section 28, a D/A converter 28d provided between the frequency error detector 28b and the input of said local oscillator 25, a digital signal decoding section 29 coupled to output of said demodulating section 28, an output terminal 30 coupled to the output of decoding section 29, a PLL circuit 31 coupled to said local oscillator 23, a frequency divider 32 coupled to output of said local oscillator 25, a microcomputer 33 whose one group of input/output terminals is coupled to all of the following items, control terminal of said PLL circuit 31, the output of said frequency divider 32, an interface circuit 28e which works as the control terminal of demodulating section for controlling said demodulating section 28 and the control terminal of said demodulating section 28; and a control terminal 34 coupled to one of the other group of input/output terminals of the microcomputer 33. Numeral 28c represents a clock recovery circuit in demodulating section 28. The operation of the above high frequency signal receiving apparatus is described in the following. A digital modulated high frequency signal inputted to input terminal 21 is amplified at high frequency amplifier 22, mixed at the mixer 24 with an output frequency from the local oscillator 23, and a desired high frequency signal is tuned and outputted. This is converted at A/D converter 27 into digital value after quadrature detection by I/Q detector 26, and delivered to demodulator 28a of demodulating section 28. In the demodulator 28a, digital signal is demodulated. Local oscillator 25 yields an oscillation frequency of around 479.5MHz which is the centre frequency of IF signal for I/Q detection by inputting the output of frequency error detector 28b to the local oscillator 25 after D/A conversion at D/A converter 28d. The IF signal is described in detail hereunder. A signal from a low noise converter is delivered to input terminal 21 of high frequency signal receiving apparatus. When a high frequency signal transmitted from a broadcasting station passes through the low noise converter a small frequency error sometimes arises. Then the centre frequency of IF signal may not be exactly at 479.5MHz. So, the output of local oscillator 25 is watched in a reverse way via frequency divider 32, and microcomputer 33 controls the local oscillator 25 so as it generates an output frequency of 479.5MHz + a, making the output of frequency error detector 28b to be 0". The frequency shift at low noise converter is thus absorbed. In demodulating section 28, clock is reproduced at the clock recovery circuit 28c. The digital demodulation is performed precisely using the clock thus reproduced. Output of the demodulating section 28 undergoes error correction, etc. at decoding section 29, and is delivered as output through the output terminal 30. A control signal from an outside equipment is delivered through control terminal 34 to microcomputer 33. The microcomputer 33 reads the contents of control signal, and outputs control signal towards control terminal of PLL circuit 31, interface circuit 28e of demodulating section 28 and control terminal of decoding section 29 in order to control PLL circuit 31, demodulating section 28, decoding section 29 respectively. What is requested to the outside equipment is to deliver a control signal only to the microcomputer 33, which means a substantially reduced burden at the outside equipment. Further, control lines from the outside equipment are connected only to microcomputer 33,which means a simplified connection as well as a less mutual interference among the control lines. As described above, outside equipment is not requested to conduct different specific controls respectively, therefore the control in outside equipment may be simplified significantly, and burden in the outside equipment is alleviated; which results in an increased processing speed in the outside equipment. At the same time, designing of an outside equipment becomes easy with the high frequency signal receiving apparatus. The microcomputer 33 employs a quartz oscillator as the fixed oscillation element to obtain precise clock frequency. The microcomputer 33 which having a precise clock frequency watches the oscillation frequency of local oscillator 25 through frequency divider 32. The frequency drift of local oscillator 25 against temperature and humidity is equal to that of the quartz oscillator. Therefore, a precise oscillation frequency may be assured against the humidity drift, without using an expensive dielectric resonator. Although a common control line(bus line) 35 may be used for coupling the microcomputer 33 to demodulating section 28 or decoding section 29, as shown in Fig.2, it is preferred to use an independent control line for the control terminal of PLL circuit 31. This comes from a consideration to avoid the possibility of a digital signal which is irrelevant to the PLL circuit 31 comming into PLL circuit 31 or local oscillator 23, resulting in a deteriorated phase noise of local oscillator 23. shows that different modulation system or the error correction method is used depending on the type of broadcasting, CATV or BS, etc. Table 1. CATV broadcast BS broadcast Modulation system VSB. 64QAM 256QAM (needs switching) QPSK (no switching) Error correction Reed-Solomon Reed-Solomon Viterbi Decode Even when the demodulating section 28 and decoding section 29 change due to different specification, the microcomputer 33 works consistently to either specifications responding to signal from outside. The switching may be conducted by either providing a specific input terminal in the microcomputer33 and fixing the signal level of which terminal, or providing an instruction from the control terminal 34. By the above described way, a volume produced microcomputer 33 of a single model can meet various different specifications. The cost reduction may be expected through volume production of the microcomputer 33. An invented high frequency signal receiving apparatus as shown in Fig.3 is divided into two units, each having an approximately rectangular shape and is made of metal. In a first unit 41, high frequency amplifier 22, local oscillator 23, mixer 24, PLL circuit 31, I/Q detector 26, second local oscillator 25 and frequency divider 32 are mounted; while in a second unit 42, A/D conterter 27, demodulating section 28, decoding section 29 and microcomputer 33 are mounted. The first unit 41 is a portion of a high frequency circuit corresponding to so-called tuner, while the second unit 42contains demodulating section 28 and decoding section 29; all being digital circuits. Thus the first unit 41, or tuner, is shielded by a metal case, which means the tuner is least affected by mixing of unnecessary signal from outside, and hardly generate unnecessary electric wave to outside. Further, as each of the units has a specific function independent to each other, respective units may be manufactured, sold or controlled separately. The two units 41, 42 are connectable and detachable in the sides 41a, 42a, or may be coupled using a connector 43. Those units having no connector 43 may be coupled by inserting terminal 44 of first unit 41 and terminal 45 of second unit 42 in a mother printed circuit board. Communication between a high frequency signal receiving apparatus and an outside equipment is performed in the following manner. For transferring a command to a high frequency signal receiving apparatus, a start singal and then an address of the high frequency signal receiving apparatus are transmitted from outside equipment. Command word is transmitted upon receiving an affirmative response signal of the high frequency signal receiving apparatus. The command word comprises type of works and detailed content thereof. In any case, command words are sent one unit by one unit after receiving an affirmative response from the other party. For surveying the state of a high frequency signal receiving apparatus, a start signal and then an address of the high frequency signal receiving apparatus are transmitted from outside equipment. After an affirmative response signal of the high frequency signal receiving apparatus, content of register is transmitted showing a state of the high frequency signal receiving apparatus. Following an affirmative response from the outside equipment, the high frequency signal receiving apparatus transmits a parity signal. Because it proceeds to a next step only after receiving an affirmative response, the communication is performed in a sure and dependable way. When affirmative response is not available, the transmission is repeated automatically up to three times. In case no affirmative response is obtained, or there is no response after the automatic repetition of transmission, the transmittance is terminated after a certain predetermined time lapsed. Then, a new communication procedure has to be started, or an operator is notified for taking other different means. When communicating with an outside equipment, the clock of microcomputer 33 needs to be precise enough for synchronization with the outside equipment. In the present embodiment, a quartz oscillator is used. Some of the major command words are described in the following. In the case of channel selection, a channel frequency is transmitted following a command of channel selection. Then the microcomputer 33 sets PLL circuit 31's main counter value and swallow counter value so as to be able to receive the channel frequency. For setting a demodulation condition, a detailed content formed with three bytes is transmitted following a command of condition setting. The first byte specifies a roll-off factor and a codifying rate, the second byte a frequency dividing rate and a designation of tuner specification, the third byte a designation of transmitting rate. Other commands include reading out of a register which indicates the state of a high frequency signal receiving apparatus, reading out of an error register, etc. As described in the above, as the command system is unified, the high frequency signal receiving apparatus may be controlled easily by anybody. INDUSTRIAL APPLICABILITY The invented high frequency signal receiving apparatus comprises a microcomputer, one group of input/output terminals of which being coupled to control terminal of PLL circuit, control terminal of demodulating section and control terminal of decoding section, while other group of input/output terminals to outside equipment; which microcomputer is controlled based on an oscillation frequency generated from a fixed oscillation element, and at the same time, controls, based on a signal delivered from outside equipment inputted through said other group of input/ output terminals, at least any one among said PLL circuit, said demodulating section and said decoding section. As the apparatus is provided with a microcomputer, one group of whose input/output terminals being coupled to control terminal of PLL circuit, control terminal of demodulating section and control terminal of decoding section, while other group of input/output terminals to outside equipment, the outside equipment may simply issue an order to the microcomputer. Then, the microcomputer controls said PLL circuit, said demodulating section, said decoding section based on an instruction delivered from the outside equipment. Therefore, the burden of outside equipment is significantly alleviated. The control line from outside equipment is connected only with a microcomputer, which means a simplified connection work and an eliminated mutual interference among control lines. Furthermore, designing of the outside equipment may become easier. Explanation of The Notations in The Drawings 1 Input terminal 2 High frequency amplifier 3 Local oscillator 4 Mixer 5 Local oscillator 6 I/Q detector 7 A/D converter 8 Demodulating section 8a Demodulator 8b Frequency error detector 8c Clock recovery circuit 8d D/A converter 8e Interface circuit 9 Decoding section 10 Output terminal 11 PLL circuit 12 PLL circuit control terminal 13 Demodulating section control terminal 14 Decoding section control terminal 21 Input terminal 22 High frequency amplifier 23 Local oscillator 24 Mixer 25 Local oscillator 26 I/Q detector 27 A/D converter 28 Demodulating section 28a Demodulator 28b Frequency error detector 28c Clock recovery circuit 28d D/A converter 28e Interface circuit 29 Decoding section 30 Output terminal 31 PLL circuit 32 Frequency divider 33 Microcomputer 34 Control terminal 35 Control line(bus line) 41 First unit 41a Side 42 Second unit 42a Side 43 Connector 44 Terminal 45 Terminal

Claims: A high frequency signal receiving apparatus comprising: an input terminal (21) for receiving digital modulated high frequency signal, a mixer (24) of which one input is supplied with the signal inputted to the input terminal (21) while other input being coupled to output of a local oscillator (23), a digital signal demodulating section (28) to which the output of mixer (24) is supplied, a digital signal decoding section (29) coupled to the output of demodulating section (28), an output terminal (30) coupled to the output of decoding section (29), a PLL circuit (31) coupled to said local oscillator (23), and a microcomputer (33) whose one group of input/output terminals being coupled to control terminal of said PLL circuit (31), control terminal of said demodulating section (28) and control terminal of said decoding section (29), while other group of input/output terminals coupled to outside equipment; wherein the microcomputer (33) is controlled by an oscillation frequency generated from a fixed oscillation element, on the other hand, controls at least any one among said PLL circuit (31), said demodulating section (28) and said decoding section (29) based on a signal delivered from said outside equipment inputted through said other group of input/output terminals. The high frequency signal receiving apparatus recited in Claim 1, wherein a frequency of fixed oscillation element outputted from microcomputer (33) is used as reference oscillation frequency of PLL circuit (31). The high frequency signal receiving apparatus recited in Claim 1, wherein a microcomputer stores in its ROM a plurality of types of specifying information for at least any one of PLL circuit (31), demodulating section (28) and decoding section (29), which specifying information being subject to selection from outside. The high frequency signal receiving apparatus recited in Claim 1, wherein at least mixer (24) and local oscillator (23) are shielded from other circuits. The high frequency signal receiving apparatus recited in Claim 4, wherein mixer (24), local oscillator(23) and PLL circuit (31) are housed in a first metal case, while demodulating section (28), decoding section (29) and microcomputer (33) are housed in a second metal case. The high frequency signal receiving apparatus recited in Claim 1, wherein an outside equipment and a microcomputer (33) communicate each other by confirming the exchange of information after every one unit of information. A high frequency signal receiving apparatus as claimed in claim 1, wherein a first control line connecting said microcomputer (33) with PLL circuit (31) is a connection line that is different from a second connection line connecting said microcomputer (33) to demodulating section (28) or decoding section (29). The high frequency signal receiving apparatus recited in Claim 7, wherein a frequency of fixed oscillation element outputted from microcomputer (33) is used as reference oscillation frequency of PLL circuit (31). The high frequency signal receiving apparatus recited in Claim 7, wherein a microcomputer (33) stores in its ROM a plurality of types of specifying information for at least any one of PLL circuit (31), demodulating section (28) and decoding section (29), which specifying information being subject to selection from outside. The high frequency signal receiving apparatus recited in Claim 7, wherein at least mixer (24) and local oscillator (23) are shielded from other circuits. The high frequency signal receiving apparatus recited in Claim 10, wherein mixer (24), local oscillator (23) and PLL circuit (31) are housed in a first metal case, while demodulating section (28), decoding section (29) and microcomputer (33) are housed in a second metal case. The high frequency signal receiving apparatus recited in Claim 7, wherein an outside equipment and a microcomputer (33) communicate each other by confirming the exchange of information after every one unit of information. A high frequency signal receiving apparatus as claimed in claim 1, wherein an I/Q detector (26) including a second local oscillator (25) is provided between said mixer (24) and demodulating section (28), the second local oscillator being controlled by an error signal outputted from a frequency error detector (28b) of said demodulating section (28), and the microcomputer (33) controls the demodulating section (28) so as output pulse counts of the second local oscillator (25) reaches a predetermined number within a predetermined time. The high frequency signal receiving apparatus recited in Claim 13, wherein a frequency of fixed oscillation element outputted from microcomputer (33) is used as reference oscillation frequency of PLL circuit (31). The high frequency signal receiving apparatus recited in Claim 13, wherein a microcomputer stores in its ROM a plurality of types of specifying information for at least any one of PLL circuit (31), demodulating section (28) and decoding section (29), the specifying information being subject to selection from outside. The high frequency signal receiving apparatus recited in Claim 13, wherein at least mixer (24) and local oscillator (23) are shielded from other circuits. The high frequency signal receiving apparatus recited in Claim 16, wherein mixer (24), local oscillator (23) and PLL circuit (31) are housed in a first metal case, while demodulating section (28), decoding section (29) and microcomputer (33) are housed in a second metal case. The high frequency signal receiving apparatus recited in Claim 13, wherein an outside equipment and a microcomputer (33) communicate each other by confirming the exchange of information after every one unit of information.

Inventors: MISHIMA AKIRA, OZEKI HIROAKI, MISHIMA, AKIRA, OZEKI, HIROAKI
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1997
Main classification: H04B1
IPC codes: H03J7, H04B1, H03D3, H04L27