JPH01190013A - High frequency signal generator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a high frequency signal generating device capable of generating an ultra-wideband high frequency signal.

[Prior Art] Conventionally, when trying to obtain frequency response of electronic devices, microstrip lines, mounted components, etc. from low frequencies to approximately 100 GHz or more, the target frequency range is wide, so the oscillation frequency range of a sweep oscillator is Due to problems such as large attenuation and reflections at connections, there has been no good way to accurately measure frequency characteristics in one configuration.

[Problems to be Solved by the Invention] One possible solution to such difficulties is to increase the bandwidth of the connection section, but when using a connector, there is a bandwidth limitation. Currently, broadband connectors have 4
0 to 50 GHz is considered to be the limit. In addition, there were problems to be solved regarding the signal source, such as the fact that no single oscillator capable of generating frequencies from low to over 100 GHz has been found.

The present invention was devised to solve the above problems, and is capable of generating signals in a wide band from low frequencies to 100 GHz or more with a single device, and directly using the generated signals without passing through a connector. It is an object of the present invention to provide a high frequency signal generator that can be easily arranged.

[Means for Solving the Problems] A configuration of a high-frequency signal generating device of the present invention for achieving the above object includes a first light source and a second light source, and a combination of the first light source and the second light source. has a control device capable of changing the difference in oscillation wavelength of the light sources, combines the outputs of the first light source and the second light source via an optical coupler, and connects the combined output of the optical coupler to the dielectric substrate. The first light source and the first light source are irradiated onto a strip line consisting of two electrodes formed opposite to each other on the surface and a gap between the two electrodes formed of a photoconductive material, and are induced in the gap between the electrodes. 2
A beat signal obtained by heterodyne detection of the oscillation wave of the light source is obtained as an output signal from the strip line.

[Function] The present invention constitutes an ultra-high-speed photoconductive switch using a gap formed on a strip line, and in this switch, a coherent light wave from a first light source and a coherent light wave from a second light source are combined. The beat signal of is obtained as the output signal. By changing the wavelength difference of the light sources, the beat signal changes from a low frequency to an output signal of 100 GH2 or more. In addition, by using a minute strip line as the source of this output signal, it is possible to place the generated signal near the object to be measured, such as a minute ultra-high-speed device, and use it without attenuation. is possible.

[Example code] Embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

The oscillation angular frequencies of l and 2 are respectively ω1. ω,.

(ω, -ω1=Δω), the electric field strength of the oscillation wave is E, respectively.
, E, is a laser diode light source. In order to make the oscillation wavelengths of the light sources 1 and 2 highly stable, temperature control devices 3 and 4 are provided, each of which includes a Peltier element and a control power source. Further, the temperature control devices 3 and 4 are set so as to sweep the relative oscillation wavelength difference between the light sources 1 and 2 by changing the temperature of the laser diode using one of the temperature control devices 3 and 4. Note that as a method of changing the oscillation wavelength, a method of controlling the bias current of the laser diode may be used.

The outputs of light sources 1 and 2 are input to an optical coupler 6 via a single mode optical fiber 5. In the optical coupler 6, the light waves from the light source 1 and the light waves from the light source 2 are combined. In addition, if necessary, a part of the above-mentioned multiplexed wave is branched at a certain ratio, and one output is sent through the same single mode optical fiber 5 as the input side and the converging optical system 7 as a light beam spot B for photoconduction. sex switch (
8) (hereinafter referred to as an optical switch). Other outputs are either matched terminated or used as monitor outputs. Here, although there is no problem in principle if space propagation is performed without using a single mode optical fiber, input/output to each optical element becomes complicated due to optical mode matching. The light wave irradiated by the optical switch 8 is absorbed and simultaneously subjected to heterodyne detection and converted into optically excited carriers. In this case, in order to match the polarization planes of the oscillated waves of the light source 1.2 in the detection section, that is, the optical switch 8, and maximize the interference effect, a single mode fiber that maintains the polarization plane is used as the optical fiber 5. Alternatively, optical fiber 5
Although a normal single mode fiber is used, an optical polarization controller (not shown) may be inserted in the path of the optical fiber 5 to adjust the polarization plane.

The detected power 1 in the optical switch 8 has only an alternating current component of Δω, and has a light wave electric field E1. If the angle φ between the planes of polarization of Et is set, it can be expressed by the following equation. (Reference [1] S, Ka
wanishi and M, Saruwatari:
Electron, Lett.

vol, 22 (1986) pp, 337-338. )■
(Δω) = E+ ” + Et ” + 2cos
φE+EtCO8(Δωt)−(1) Accordingly, if the oscillation wavelength of the light source 1.2 is controlled and changed, this detection section will detect amplitudes E and E at the beat frequency f, (=Δω/2π).
It can be seen that a sinusoidal signal of variable frequency proportional to , is generated. That is, the door 9 optical switch 8 becomes a local high frequency signal generation source. According to the above-mentioned document [1], in a 1.3 μm band DF'B laser (distributed feedback laser), the temperature control method
Changes in Hz/°C can be achieved.

FIGS. 2(a) and 2(b) show an example of the structure of the optical switch 8, which is the main component of the present invention. Regarding the structure and characteristics of this optical switch, please refer to the literature [2], C, H, L
Edited by ee: Picogecond 0ptoelctr
onicDevices, Acaden+ic Pre
ss (1984) pp. 73-117. In FIG. 2(a), 9 is a dielectric substrate, 1
0.2 is the upper electrode, and 12 is the lower electrode. A gap 13 is provided between the opposing upper electrodes 10 and 11. Reference numeral 13 denotes a photoconductive gap in the surface portion of the dielectric substrate 9, and upon irradiation with the light beam B, the gap 13 is electrically short-circuited by generation of carriers therein. Therefore, hereinafter, the optical switch in the form of the gap 13 will be referred to as a gap type optical switch. In the structure of FIG. 2(a), the upper electrodes to, tt.

A strip line is formed by the dielectric 91L and the lower electrode 12, and as a result, electromagnetic waves induced by carriers propagate into the strip line.

Here, the dielectric substrate 9 is a substrate (SO9) in which a silicon thin film is formed on sapphire, and the surface of the gap 13 is damaged by oxygen ion implantation. As a result, the lifetime of photoexcited carriers is as short as sub-picoseconds, and high-speed response can be achieved. or,
It is also suitable that the surface including the gap 13 is made of amorphous silicon. In addition, a substrate using a compound semiconductor such as a gallium arsenide substrate, an indium phosphorous substrate doped with iron element, or a P-type germanium polycrystal is also suitable for the dielectric substrate 9.

FIG. 2(b) shows the shape of the pond in the gap type optical switch. 9, 10, 11.12 are shown in Figure 2 (a
), but 14
is a gap type optical switch made of a different material from the gap type optical switch 13 shown in FIG. 2(&). That is, a photoconductive switch is manufactured separately from the waveguide and installed at a desired location near the object to be measured. This configuration has the advantage of widening the range of objects to be measured and allowing selection and use of the optimal optical switch.

FIGS. 3(a) and 3(b) show a gap-type optical switch with a configuration different from that in FIG. 2, and its feature is that the gap between the electrodes 15 of a co-branched strip line is used as the optical switch part. This optical switch section is a point that can be continuously moved by moving the optical beam spot B along the strip line. That is, there are advantages such as the ability to evaluate the characteristics of a single strip line. this.

The configuration of the slide type switch is shown in the document [3] M, B,
Ketchen et al., Appl, Phys, Lett,
vol, 48 (1986) pp, 751-753. and literature [4] 11. J., Galla-gher et al., A.
ppt, phys, Lett, , Yol, 50 (19
G? ) pp, 350-352. It is described in

An application example of the signal generator of the above embodiment will be described.

As mentioned at the beginning, the present invention can be applied from low frequency to 100G.
It is an ultra-wideband signal generation system that extends over Hz,
The objects to be measured include the ultra-wideband strip line itself, ultra-high speed devices, and mounted components. FIG. 4 is an example of a measurement system in which the objects to be measured 16 are connected and an optical sampling detection system used for high-speed signal waveform measurement is applied to measure the transmission characteristics thereof. The light source 1.2, the optical coupler 6, and the optical switch 8 have the same functions and structures as in FIGS. 1 and 2. A part of the strip line 11 following the optical switch 8 is cut off in the middle, and a device as the object to be measured 16 is connected by a short wire bond or flip chip bond.
The other end of 1 is an electrically matched termination.
A gap-type optical switch 17 for signal detection similar to the optical switch 8 is formed in a direction perpendicular to the strip line 11 at a position after passing through the object to be measured 16 and immediately before the termination lla. The optical switch 17 receives an extremely short-time width optical pulse B from the detection light source 19.
' is irradiated, and the signal propagating through the strip line 11 is sampled by an extremely short-time switching function.

In this case, the light source 19 is in synchronous relationship with the light source 1.2 via the reference signal generator 18. As the light source 19, for example, a mode-locked and pulse-compressed dye laser is used. A short-pulsed laser diode light source is also compact and suitable if the optical switch is highly sensitive to that wavelength. The sampling signal is led to the outside via the electrode 20, processed by the signal processing system 21,
It is displayed on the display system 22. What is obtained in this way is a sine wave signal waveform of the beat frequency f, and by tracing the relative amplitude of this waveform with respect to the beat frequency f, the frequency characteristics of the object under test can be obtained. can. For synchronization and averaging processing of the signal processing system 21, an optical chopper 23 is used as necessary. As the gap-type optical switch 8 in FIG. 4, it is effective to use the covarna type slide switch shown in FIG. 3(a) (the same applies to FIG. 3(b)) as shown in FIG.

FIG. 6 is a diagram of another application example. This application example is for a device with a processing function such as a frequency divider as the device under test 24, and when the output frequency of the device under test 24 is in the range of 40 to 50 GHz or less. be.

In this case, a broadband connector 25 can be used at the output end, and the processed signal may be taken out to the outside through it.

In any of the above application examples, the signal generation source is formed by a minute strip line, so the ultra-wideband signal generation source can be used close to the object under test without attenuation and without going through a connector. It is characterized by the presence of

As described above, this embodiment solves the problem of preventing the attenuation of high-frequency signals at connection parts such as connectors by making the source of the signal in the micro form of a strip line. This allows the signal generation source to be installed near the object to be measured. Also, from low frequency to 100G
To solve the problem of performing broadband oscillation up to about Hz using a single signal source, we have developed an idea that uses a difference frequency signal (beat signal) obtained by heterodyne detection of an optical frequency obtained by combining two light waves. Specifically, by performing the detection function with a detection section that has the function of an extremely high-speed photoconductive gap switch, an extremely wide band can be achieved.
This realizes a variable signal generator.

Note that the present invention is not limited to the above embodiments,
It can be applied in various ways and can be implemented in various ways according to its main purpose.

[Effects of the Invention] As explained above, the present invention generates a coherent optical beat signal in an ultra-high-speed photoconductive gear-shaped switch and changes the wavelength, thereby achieving an advantage that could not be obtained conventionally. This device can provide an ultra-wideband signal generation source ranging from low frequencies to high frequencies exceeding 100 GHz.

Furthermore, the source of the signal can be placed locally at one end of a minute strip line. Therefore, by placing the signal generator near the object to be measured, such as a minute ultra-high-speed device or mounted component, The frequency characteristics of the object under test can be measured at once over an extremely wide band, which previously could not be measured or without a combination of different measurement methods, without directly attenuating the signal. It has the advantage of allowing precise evaluation. It is also extremely effective as a method for precisely measuring the frequency characteristics of the surface resistance of new and unknown materials, such as oxide superconducting materials, and clarifying their physical properties. be.

In the case of this measurement, since the loss is small, a signal with a frequency of 100G82 or higher is required, but such a wideband variable signal source cannot be obtained with other signal sources, and the effects of the present invention are extremely large.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIG. 2(a)
, (b) are diagrams showing the configuration of an optical switch which is the main component of the present invention, FIGS. 3(a) and (b) are diagrams showing other configurations of the gap type optical switch, and FIG. FIG. 5 is a diagram showing another configuration of the gap type optical switch in FIG. 4, and FIG. 6 is a diagram showing another example of application. 1.2...Light source, 5...Single mode optical fiber, 6
...Optical coupler, 7...Optical system, 8.13,14
゜17...Gap type optical switch (gap), 9.
...Dielectric substrate, 10, 11, 12, 15.20...
Electrode, 16.24... object to be measured. (G) (b) Figure 3 Figure 4

Claims (1)

[Claims] (1) It has a first light source and a second light source, and it has a control device that can change the difference in oscillation wavelength between the first light source and the second light source, and the first light source and the second light source The outputs of the two light sources are combined via an optical coupler, and the combined output of the optical coupler is applied to two electrodes formed facing the surface of the dielectric substrate, and a gap between the two electrodes formed of a photoconductive material. The first light source and the second light source are irradiated onto the strip line consisting of the first light source and the second light source, and
A high-frequency signal generating device characterized in that a beat signal obtained by heterodyne detection of an oscillation wave of a light source is obtained as an output signal from the strip line.