40GHz-Band Direct Digital RF Modulator Using the 2nd Image Component of 1-Bit Delta-Sigma Modulated Signal

In this paper, we propose a 40GHz-band direct digital RF transmitter using the 2
^nd
image component of 1-bit band-pass delta-sigma (BP-DS) modulated signal for milimeter-wave applications. The proposed transmitter can directly generate RF signal at 40 GHz band from 1-bit BP-DS modulated signal whose bitrate is 32 Gbps which is lower than the RF signal. By using
$1V_{\text{pp}}/32$
Gbps 1-bit data stream, the 20Msps-QPSK (carrier frequcncy:
$f_{c}$
=40 GHz) can be extracted from its 2
^nd
image component at 3
^rd
Nyquist zone. From the measurement result, the output 20Msps-QPSK (
$f_{c}$
=40 GHz) signal has the output power of -30.6 dBm, ACLR of -33.5 dBc and EVM of 3.5 %.