All-Digital RF $I/Q$ Modulator

A wideband 2 × 13-bit all-digital I/Q RFDAC

“…Note that the measurement results of Fig. 21(b)-(d) are obtained as follows [21]. The time-domain RF output signals are captured and saved.…”

“…As mentioned earlier, each orthogonal path generates more than 16 dBm of RF power at V. As a result, (8) where is a unitless function and depends only on the duty cycle , and thus, [21], [24]. Based on (8), the following equation is derived: (9) According to [21, eqs.…”

“…Generally, the desired determines the size and structure of the selected transformer, which subsequently determines the value of for a given value of the magnetic coupling factor . To conclude, the balun de-couples the drain dc condition from the load (elimination of ) and converts the differential signal to a single-ended output [21], [26]. Furthermore, the balun provides a dc bias path for the DRAC transistor switches (elimination of ) and transforms the 50-load to the desired impedance at the drain nodes of DRAC.…”

“…Moreover, a simple back-to-back inverter pair [see Fig. 10(a)] is employed for further phase alignment, which was not feasible in [21]. As a result, by exploiting smaller devices, faster rise/fall times are achievable.…”

“…For wide modulation bandwidths, due to their direct linear summation of the I and Q signals, and thus, the avoidance of the bandwidth expansion, Cartesian modulators prove to be a better choice than their polar or outphasing counterparts [19]- [21]. Reference [6] proposed a digitally controlled I/Q modulator that utilizes current sources to isolate the orthogonal I and Q paths.…”