# Spintronic RF-Direct on-off Keying Modulation Using a Frequency Division Multiplex
## 5 Measurement Results  
Figure 10 shows the block diagram for the test and the measurement setup environment. To perform the test for wireless communication, the fabricated spintronics array transmitter is placed on a C-type magnetic closed circuit to apply a magnetic field around the DUT. Constant current is applied to the electromagnet by a precision current source, and a fringing field is generated depending on the current quantity. The direction of the magnetic field, rotation field angle, is also changed by manually making the C-type magnetic closed circuit rotate, as shown in Figure 10. Current quantities were supplied by changing the current corresponding to each STNO bonded to the 50 ohm line through the bias-tee, allowing the required magnetic field amplitude and phase to be obtained by limiting the current to protect the STNO. Figure 10 shows the spintronics array Tx bonded with STNOs structured in a 2 \(\times\) 4 array for transmitting multi-channel signals on the magnetic field generator. We selected two out of the eight STNOs and set the target frequency by controlling the magnitude of the magnetic field, the rotation field angle of the applied magnetic field to the STNO, and the current quantity based on STNO operation [22]. Figure 10 also shows a photo of the two channels receiver, each of which has an antenna, BEF, LNA, and detector, and the receivers are designed into the assigned frequency band excluding the antennas, which cover both channels. We situated an RF switch between the LNA and the detector to monitor the received signal at the assigned RF monitor port. The RF switch is controlled by a dip switch. Under these design boards, we carried out the test of wireless communication by the spintronic RF-direct OOK modulation using an FDM with two STNOs in the array. The receiver is located at a distance of 10 mm from the transmitter. Under these measurement conditions, we tested the operation of the transmission on two frequencies modulating OOK into one antenna. In Figure 10, red text indicates the equipment to adjust the frequency and amplitude for the two channel signals, black text is the measurement equipment for the communication test, and yellow text is the transmitter and receiver board designed with the STNO array. The test setup was supplied by the Korea Basic Science Institute (KBSI, Deajeon, Korea). The measurement results show that a data rate of up to 4 Mbps is obtained at array STNO, and the power consumption is under 3 mW per STNO at these measurement conditions. It is observed that 0.18 mW power consumption occurs at one STNO. The value of 0.9 nl/bit obtained from the power consumption result of spintronic modulated radio  
Figure 10: Measurement settings for two-channel receivers and spintronic RF-Direct On-Off keying modulation. (a) Block-diagram of the test setup, and (b) test environment picture. technology is not a remarkable achievement, as it uses commercial circuits supplied with 2 VDC. Nevertheless, this is the first successful trial of communication with spintronic technology in the array structure. Based on this transmission and reception result, the UART interface was used as a modulation input to obtain and transmit the serial signal wirelessly, and it was confirmed that the image was displayed successfully. In this experiment, the maximum transmission rate of UART was 115,200 bps. These circuits will be fabricated in the near future, together with a sub-10 nm scaled STNO array CMOS technology such as a magnetoresistive random-access memory (MRAM). The size and power consumption of the wireless technology of spintronic modulation consequently approach those of the core block, the STNO.