RF Chain-Free mmWave Transmission: Modeling and Experimental Verification

TL;DR

This paper explores a novel RF chain-free millimeter wave transmission method using time-modulated arrays, providing modeling, harmonic suppression techniques, and experimental validation at 25 GHz to enable secure, low-cost communication.

Contribution

It introduces a frequency analysis tool for time-modulated arrays with hardware impairments and demonstrates harmonic suppression and phase error reduction through experimental verification.

Findings

Phase error reduced by 32% using the proposed architecture.

Harmonics significantly suppressed by optimal sampling period.

Experimental validation conducted at 25 GHz confirming theoretical results.

Abstract

The utilization of millimeter wave frequency bands is expected to become prevalent in the following communication systems. However, generating and transmitting communication signals over these frequencies is not as straightforward as in sub-6 GHz frequencies due to complex transceiver structures. As an alternative to conventional transmitter architectures, this paper investigates the implementation of time-modulated arrays to effectively modulate and transmit high-quality communication signals at millimeter wave frequencies. By exploiting the array structures and analog beamformers, which are the fundamental components of millimeter wave transmitters, secure and low-cost transmission can be achieved. Though, harmonics of theoretically infinite bandwidth arise as a fundamental problem in this approach. Thus, this paper presents a frequency analysis tool for the time-modulated arrays with hardware impairments and shows how controlling the sampling period can reduce the harmonics. Furthermore, the derived results are experimentally verified at 25 GHz with two important remarks. First, the phase error of received signals can be reduced by 32% using the proposed architecture. Second, the harmonics can be significantly suppressed by the correct choice of sampling period for the given hardware.