Microstrip band-pass filter with −67 dB stop band up to 8.8 times the pass-band center frequency

Step-impedance resonators and step-impedance capacitor coupling pads are introduced to microstrip band-pass filters to suppress spurious stop-band responses up to the ninth order, thereby providing a very wide stop band. Combined with improvements in existing suppression techniques, the overall suppression in one of the filters, with 1 GHz center frequency and 42% bandwidth, is −54 dB, up to 8.9 GHz. By also using suitably placed resistors, spurious levels are now depressed to −67 dB up to 8.8 GHz, with only 0.03 dB extra pass-band loss.

Capacitor-Coupled ECG System for Wearable Equipment

A design of capacitor-coupled ECG test system is introduced here. The extremely weak ECG signal was picked up with capacitor coupling sensor, and was then buffered, filtered and magnified to fit the requirement of analog digital converter. The measured data was then converted and processed by a microcontroller. The ECG signal can be recovered and stored, analyzed by intelligent terminal. The test shows that this method is applicable and would be used widely.