A Multipurpose D-Band Vector Modulator for FMCW and PMCW Sensing Applications in 130 nm SiGe

The increased deployment of radar systems raises concerns about mutual interference among radar sensors sharing the same frequency band. Phase-modulated continuous wave (PMCW) techniques with orthogonal transmit codes can mitigate those problems. Moreover, many applications require 3-D detection, which needs either a steerable antenna beam (analog beamforming) or independent receive channels (digital beamforming). In this article, we present a
$\mathbf {125} \, \text {GHz}$
vector modulator (VM) that can either shift the phase for phased-array operation or can be turned off for time-division multiple-input multiple-output (MIMO) operation. Phase-shifting is possible using analog (slow but fine-stepped) and digital (fast but course-stepped) control signals. Also, both interfaces can be used simultaneously to create steerable PMCW beams. The VM was fabricated using the B11HFC technology from Infineon Technologies AG and consists of four compactly interconnected power amplifiers (PAs): Two are fed with an in-phase (
$\mathbf {I}$
) signal, and two are fed with a quadrature (
$\mathbf {Q}$
) signal. Within the PA pairs, the PAs are cross-connected to a common inductive load so the
$\mathbf {I}$
and
$\mathbf {Q}$
signals can be inverted, generating output phases between
$\mathbf {0}^{\circ} $
and
$\mathbf {360}^{\circ} $
.