## 1 Introduction  
There has been an explosive growth of data capacity and data rate in fifth generation wireless networks (5G) [1]. The millimeter wave and terahertz frequency range has a large amount of unlicensed spectra, and this has gotten a lot of attention in wireless communication [2; 3].  
The millimeter wave and terahertz communication systems mainly include all-electronic and optoelectronic systems. The advantage of all-electronics systems is higher output power, but their data rate is lower [4; 5]. Most of the optoelectronic systems are based on uni-traveling carrier photodiode (UTC-PD), which can obtain a higher data rate [6; 7]. However, its system integration is poor due to its complicated optical equipment.  
A resonant tunneling diode (RTD) is a high speed solid-state device [8]. Recently, many literatures on short distance and high data rate wireless communication with RTD have been published [9; 10; 11; 12; 13]. In [9], wireless data transmission by direct amplitude shift keying was demonstrated by using an RTD oscillating at 542 GHz, with a data rate of 3 Gbps. In [10], a 9 Gbps on-off keying module system was achieved, and the RTDs were employed to be the transmitter and receiver by changing the bias voltage of the RTD. In [11], a wireless data transmission of 34 Gbit/s at 500 GHz range was proposed, where the output power was about 60 \(\mu\)W. To improve the RF output power, [PERSON] et al. designed an RTD pair configuration to obtain an increased negative differential conductance voltage span; the maximum RF output power was \(-1.76\) dBm at 24.1 GHz [12]. In the same year, [PERSON] et al. also proposed an improved RTD pair, and the maximum output power was 2 mW without any power amplifier at the oscillator frequency 84 GHz [13].  
However, the use of a probe station and DC bias lines reduce the flexibility of RTD chips, and the exposed RTD chips are susceptible to mechanical damage, which makes them difficult to apply in the communication system. In addition, to the best of our knowledge, there has been no literature on a packaged RTD due to the complicated packaged process, including DC bias, electrical signal connection, and efficient RF conversion.  
Most millimeter wave and terahertz devices are waveguide output. To enhance system integrity, it is necessary to package the RTD with a rectangular waveguide output. In this paper, an RTD with rectangular waveguide output for a W band communication system application is presented. First, a coplanar waveguide (CPW) transition to rectangular waveguide structure based on the E plane probe was designed to achieve the output signal of the RTD efficiently coupled into rectangular waveguide. Then, we designed the packaged RTD structure, and we fabricated and measured the performance of the packaged RTD. Measured results demonstrated that the oscillation frequency of the packaged RTD was from 88 to 92 GHz, and the maximum RF output power was \(-7\) dBm. Finally, to verify the wireless transmission capability of the packaged RTD, a highly integrated and high speed wireless communication system based on on-off keying (OOK) modulation with the RTD was built, and the date rate of 7 Gbps was realized.