Single antenna for receipt of signals from multiple communications systems

A frequency isolation circuit for simultaneously receiving radio frequency signals in different first and second radio frequency bands, the first and second radio frequency band being L-band and the second radio frequency band being GPS navigation data radio frequency band, the circuit comprising:

• a directional coupler configured to direct a signal input at first port into one or more second ports;
• and
• one or more filters coupled to receive the output of each said second ports, said one or more filters being configured to reflect radio frequency energy in radio frequency bands other than the second GPS navigation data radio frequency band;
• said directional coupler further configured to direct said reflected radio frequency energy into another port of said directional coupler;
• and
• a filter coupled to said other port of said directional coupler, said filter configured to reflect radio frequency energy in radio frequency bands other than the first radio frequency L-band.

The frequency isolation circuit recited in claim 20, wherein:

• said coupling between said first port and said second port results in a loss of 3 dB with a 0 degree phase shift;
• said coupling between said first port and said third port results in a loss of 3 dB with a −90 degree phase shift;
• said coupling between said fourth port and said second port resulting in a loss of 3 dB with a −90 degree phase shift;
• said coupling between fourth port and said third port resulting in a loss of 3 dB with a 0 degree phase shift;
• said coupling between said second port and said first port resulting in a loss of 3 dB with a 0 degree phase shift;
• said coupling between said second port and said fourth port resulting in a loss of 3 dB with a −90 degree phase shift;
• said coupling between said third port and said fourth port resulting in a loss of 3 dB with a 0 degree phase shift;
• and
• said coupling between said third port and said first port resulting in a loss of 3 dB with a −90 degree phase shift.
• 22.The frequency isolation circuit recited in claim 21, further comprising a third band pass filter coupled to said fourth port of said directional coupler, said third band pass filter passing radio frequency energy in the first satellite telecommunications radio frequency band.