Digital Dual-Channel K-Band Microwave Radiometer: Architecture and Measurement Results

This paper presents a digital dual-channel passive microwave radiometer operating in the K-band. The radiometer is based on commercial satellite communication low-noise block converters, which possess an analog bandwidth of 1 GHz. An external reference clock distribution is employed to ensure channel coherence. The digital design achieves a bandwidth of 614.4 MHz with a 14-bit ADC resolution. Up to 4 GB of complex valued dual-channel time domain data can be captured and stored. Power measurements can be performed using a field programmable gate array, ensuring real-time responsivity. Phase delay, correlation and sensitivity measurements were conducted with this setup and the results show good agreement with the expected theoretical outcomes.

I. Introduction

Passive microwave radiometers (PMR) have been used amongst others for many different applications like industrial process measurements [1], medical applications [2] and detection of forest fires [3]. With the improvement of analog-to-digital converters (ADCs), many analog blocks of a radiometer can be implemented in the digital domain with the typical advantages of digital processing like reconfigurability, stability and the possibility to perform more sophisticated signal processing algorithms. One example for such a digital radiometer was published in [4], which presents an IQ single channel digital radiometer used for spectrum sensing. In this paper, we introduce an IQ dual-channel digital radiometer with a bandwidth up to 614.4 MHz. In Section II we will discuss the hardware and software architecture of the digital radiometer and in Section III we will present phase delay, correlation and sensitivity measurements.