Cartoon to illustrate the geometry of a BLR offset from the BBH orbital plane as a possible interpretation for both the broad emission line profiles and periodicity of PG 1302-102 under the Doppler boosting scenario. The inclination angle of circumbinary BLR is ∼33°, with an opening angle of ∼43°. The BBH orbital plane (solid line) is misaligned from the middle plane of the BLR with an offset angle of ∼51°, which indicates a close to edge-on inclination.