One of these boards is included in the Hardware Kit with the GSPS ADC Reference Boards. Since the analog inputs to the ADC1xDxx00RB are differential and most signal sources are single-ended, these balun boards are generally used to achieve single-ended-to-differential conversion. In case both I- and Q-inputs are simultaneously driven with a similar signal, an additional balun board of the same type may be desired.
Incidentally, this balun board may also be used to do differential-to-single-ended conversion. For example, this balun board may be used when observing the DCLK+/- or RCOut+/- signal on a single-ended scope when exploring the AutoSync feature on the GSPS ADC Reference Boards.
The ADC-LD-BB uses the B0430J50100AHF from Anaren, which is designed for high-performance and low cost. Since the input impedance of the GSPS ADCs are 100Ω and the impedance of most signal generators are 50Ω, its 1:2 impedance ratio is very convenient. The 10pF capacitor at the input is recommended by Anaren for best performance. This balun is also a very good choice for driving the GSPS ADC sampling clock (CLK+/-).