A 1 to 20 GHz Microwave Sampler

The 1 to 20 GHz sampler circuit described in this paper has many novel features, including a new wideband microstrip/slotline balun and a wideband active isolator to reduce LO to RF leakage. The signal to noise ratio over the RF bandwidth is greater than 20 dB with an input power level of -32 dBm, which is measured in an IF bandwidth of 175 MHz and includes the contribution from the IF amplifier. The sampler has an integrated impulse generator which requires a sinusoidal LO driver of only 20 dBm over the frequency band of 250 MHz to 350 MHz. The IF signal is in the band of 10 MHz to 175 MHz. The RF input VSWR is better than 2:1 up to 20 GHz. The LO to RE breakthrough is better than -58 dBm, when driven with a LO of +20 dBm. This unusually low leakage has been achieved by using an integrated active isolator circuit prior to the sampling circuit.