Electronic circuit device

1. An electronic circuit device comprising:

a first pair transmission line comprising a power-supply line, a first ground line and a first insulating layer disposed between the power-supply line and the first ground line, a face of the power-supply line facing a face of the first ground line;

a driver transistor; and

a second pair transmission line comprising a signal line, a second ground line and a second insulating layer disposed between the signal line and the second ground line, a face of the signal line facing a face of the second ground line, and an output of the driver transistor being supplied to the signal line,

wherein the power-supply line is directly connected to a drain layer of the driver transistor and the first ground line is connected to a substrate of the driver transistor.

2. The electronic circuit device of claim 1 , wherein a wiring length of the second pair transmission line is longer than a quarter of a wave length of a harmonic of a tenfold frequency of an operational pulse frequency of the driver transistor.

3. The electronic circuit device of claim 1 or 2 , wherein the signal line is directly connected to a source layer of the driver transistor and the second ground line is directly connected to the substrate of the driver transistor.

4. The electronic circuit device of claim 3 , wherein a characteristic impedance of the first pair transmission line is equal to or greater than a characteristic impedance of the second pair transmission line.

5. The electronic circuit device of claim 1 , wherein the first ground line is connected to the second ground line through a low resistance layer formed in the substrate of the driver transistor.

6. An electronic circuit device comprising:

a main pair transmission line comprising a main power-supply line and a main ground line;

a plurality of branch pair transmission lines branching off from the main pair transmission line, each of the branch pair lines comprising a branch power-supply line and a branch ground line;

a driver transistor connected to each of the branch pair transmission lines;

another pair transmission line comprising a signal line and another ground line, an output of the driver transistor being supplied to the signal line; and

a receiver circuit receiving a signal transmitted from the another pair transmission line.

7. The electronic circuit device of claim 6 , wherein the device is configured so that following formula applies:

Z ops ≦Z opt /n ≦1.2 Z ops

where n denotes a number of the branch pair transmission lines, Z 0ps denotes a characteristic impedance of the main pair transmission line and Z 0pt denotes a characteristic impedance of the branch pair transmission lines.

8. The electronic circuit device of claim 6 , further comprising a wiring web structure connected between a group of the branch pair transmission lines and the main pair transmission line.

9. The electronic circuit device of claim 8 , wherein each path between the branch pair transmission line and the main pair transmission line in the wiring web structure has a same length.

10. The electronic circuit device of claim 6 , 7 , 8 or 9 , further comprising:

a plurality of bypass capacitors connected to a terminal portion of the main pair transmission line;

a supply-side pair transmission line connected to the terminal portion and comprising a supply-side power-supply line and a supply-side ground line;

a capacitor connected between the supply-side power-supply line and the supply-side ground line; and

a power-supply circuit connected to the supply-side pair transmission line.

11. The electronic circuit device of claim 6 , 7 , 8 or 9 , further comprising an attenuation circuit which comprises a pair of capacitors connected between the main power-supply line and the main ground line and a resistor connecting the pair of capacitors, and is disposed adjacent a branching point of the main pair transmission line.

12. The electronic circuit device of claim 11 , wherein the pair of capacitors has a total capacitance equal to or larger than 50 times as large a capacitance as the main pair transmission line of a same length as a length of the attenuation circuit along a longitudinal direction of the main pair transmission line.

13. The electronic circuit device of claim 6 , 7 , 8 or 9 , further comprising an attenuation circuit which comprises a pair of electrodes for capacitor formation disposed between the main power-supply line and the main ground line and a resistor connecting the pair of electrodes, and is disposed adjacent a branching point of the main pair transmission line.

14. The electronic circuit device of claim 13 , wherein a pair of capacitors each formed between the main pair transmission line and a corresponding electrode has a total capacitance equal to or larger than 50 times as large a capacitance as the main pair transmission line of a same length as a length of the attenuation circuit along a longitudinal direction of the main pair transmission line.

15. The electronic circuit device of claim 6 , 7 , 8 or 9 , further comprising:

a directional coupler comprising paired lines and disposed adjacent a branching point of the main pair transmission line; and

a terminating resistance connecting the paired lines.

16. The electronic circuit device of claim 15 , wherein a spacing between the main pair transmission line and the directional coupler is equal to or smaller than a thickness of a conductor forming the directional coupler.