A 434 MHz analog frontend for wakeup receivers based on a switched injection-triggered oscillator (SITO) designed in IHP SGB25V 250 nm BiCMOS technology is presented. On-off keying (OOK) demodulation is performed by evaluating the ramp-up time of a one-port oscillator. The oscillator drives a dual resonator consisting of an off-chip LC parallel tank in parallel to a surface acoustic wave (SAW) resonator. In conjunction with an antenna switch the SAW resonator alternatingly accumulates signal energy and emits it as a pulse to trigger the oscillator ramp-up. This results in a high measured input sensitivity of -91dBm (without coding) while delivering a narrow measured 3dB input filtering bandwidth of 166kHz due to the high quality factor of the SAW resonator. Bitwise duty cycling leads to an energy efficient receiver frontend with a low measured DC energy per bit of 175pJ. Data rate and DC power can be scaled over a wide range from 100bps at 17.5nW up to 15kbps at 2.6μW (all measured).