Research

In the Frontier Integrated Systems Laboratory, we are studying integrated circuits operating at millimeter wave to terahertz.

Millimeter wave has been used as an ultra-high-speed wireless communication to the enabling technologies of the next-generation standard 5G of mobile phone technology. It is also used as a radar in order to protect the safety of the car

Terahertz, higher frequency than millimeter wave, is in the electromagnetic wave having an intermediate nature of light and radio waves. Since?its handling was difficult in technically, it was not so much used historically. However, it has become finally practical by recent advances in electronics.

On the other hand, since it still has high technical difficulty, the device cost was too high to take advantage of its excellent properties in a wide range of fields.

In order that people can utilize?infinitely spread applications in the terahertz region , we aim to put into practical use in the device using an cost-effective?silicon integrated circuit.

Research theme example

  1. Study of 300GHz band radio

Radio waves is a finite resource. In the IoT, things will also use the radio as well as the human. Therefore radio users will continue exploding. If you do nothing, the radio resources will be depleted. Therefore, the research to develop the radio wave resources are underway all over the world. In one of them, there are studies utilizing terahertz waves in radio. Terahertz wave is an electromagnetic wave between the light and radio waves. Terahertz wave was technically difficult to handle. There are a number of technical issues that must be overcome. While challenging the technical issues, we are studying the radio using the 300GHz band in the terahertz wave.

2. A study of the wide-band amplifier circuit

To achieve high-speed wireless communication, you will need an amplifier for amplifying the wide frequency band with more than 10GHz. Such an amplifier, you must have a flat frequency characteristics and low power operation. We studied the design method of such an amplifier.

3. A study of the low-noise oscillator

In order to exhibit a good performance in the high-frequency circuit, the phase noise of the oscillator must be low. Phase noise has been known to be worse in proportion to the square of the frequency. We study the design method of low phase noise oscillator at high frequencies, such as terahertz waves.

4. Study of ultra-wideband power

Impedance of the power supply is ideally zero. Therefore, decoupling capacitor with?low impedance at high frequencies is connected in the power supply . However, under the influence of the parasitic inductance and parasitic resistance, the impedance of the decoupling capacitor is actually will increase as the frequency increases. We have developed a decoupling device referred to as a zero ohm transmission line that indicates the low impedance up to more than 300GHz. We are studying?the ideal power source?at all frequencies .

5. A study of terahertz implementation

Even if the circuit operates properly, the circuit is not available in fact if you can not connect to an external device such as an antenna. Process for connecting the integrated circuit and other devices are called implementation. In terahertz, we are studying implement a CMOS integrated circuit with low insertion loss.

6. Study of terahertz layout

Even if the floor plans of houses are?the same, livability changes in different design. Similarly, even in the same circuit, performance changes in?different layout (drawing of an integrated circuit). Thus, by using an electromagnetic field simulation, we are studying the layout to maintain the high performance even at ultra-high frequency.

7. Study of communication system

To realize the communication system, it is necessary to estimate the performance required for each element prior to breakdown in the radio circuit. Simulation for estimating the performance is called a functional simulation. However, circuits in terahertz are often newly developed. Therefore, it is not possible to simulate the system while using the existing model. So, in parallel with the circuit design, we are building a model for functional simulation?before?estimating the final performance. We are studying how to efficiently perform functional simulation in the terahertz.

8. A study of the frequency multiplication

The upper limit of the frequency that can be realized by the oscillator alone will determined by the operating limit frequency of the transistor. In order to synthesize a higher frequency than it is, but you need to use the frequency multiplier, the efficiency of frequency multiplier used in the terahertz extremely low as 1% or less, not only would waste most of the energy , you can not generate the terahertz wave of high output. So, along with the increase the efficiency of the frequency multiplier, we are conducting research of the frequency multiplier that can achieve low noise.

9. A study of the device model

To design an integrated circuit is usually the device model to be used in the circuit simulation from a manufacturer of integrated circuit (called foundries) will be provided. If this device model is appropriate, the results of the circuit simulation shows the actual measurement and a good match, but I do not know anyone or model that fits with the measured result in the terahertz What thing of. So we not only show a linear characteristic is a good match of the necessary transistors for the amplification circuit, an oscillator, a mixer, a model study of showing measured and good agreement is also in the circuit that utilizes a non-linear characteristics of the transistor, such as multiplier conducted you have.

10. High-frequency measurement, study of evaluation

Measuring instrument and only there is a integrated circuit does not always make the right measurement. The first place is the correct measurement, but you’ll be the results close to the true value (referred to as the reference) is obtained, it will also be difficult to find a true value as the frequency increases. So we, appropriately select the reference, in devising a method for measuring and calibration method, we are conducting research of measurement techniques, such as seems to be close to the correct answer to see physically.