Forward and reverse test point circuit with switchable termination for use in an RF amplifier
A forward and reverse test point circuit with a switchable termination may be used to provide testing of forward and reverse RF signals in an RF amplifier before and/or after amplification. The switchable forward and reverse test point circuit includes at least one switchable termination circuit coupled between forward and reverse terminals of a directional coupler and at least one test point. During forward signal testing, the forward terminal is switched to the at least one test point and the reverse terminal is switched to a termination. During reverse signal testing, the reverse terminal is switched to the at least one test point and the forward terminal is switched to a termination. The RF amplifier including the switchable forward and reverse test point circuit may be used in a hybrid fiber-coaxial (HFC) network delivering CATV services and may be capable of amplifying RF signals up to 1.8 GHz.
1. A switchable forward and reverse test point circuit comprising:
a directional coupler configured to be coupled to an electrical path on which both forward and reverse RF signals travel, the directional coupler including a forward terminal configured to split off a portion of the forward RF signal and a reverse terminal configured to split off a portion of the reverse RF signal;
a test point configured to provide access to at least one of the forward and reverse signals via the forward and reverse terminals;
a switchable termination circuit coupled between the forward and reverse terminals of the directional coupler and the at least one test point, wherein the switchable termination circuit is configured, during forward signal testing, to switch the forward terminal to the test point and to switch the reverse terminal to a termination, and wherein the switchable termination circuit is configured, during reverse signal testing, to switch the reverse terminal to the test point and to switch the forward terminal to a termination; and
wherein the test point includes a single forward and reverse test point, and wherein the switchable termination circuit includes a self-terminating switch coupled between the reverse terminal and the forward terminal of the directional coupler and the single forward and reverse test point.
2. The switchable forward and reverse test point circuit of claim 1 , further including a forward attenuation and tilt network coupled between the forward terminal of the directional coupler and the self-terminating switch and a reverse attenuation and tilt network coupled between the reverse terminal of the directional coupler and the self-terminating switch.
3. The switchable forward and reverse test point circuit of claim 1 , further including an attenuation and tilt network coupled between the self-terminating switch and the single forward and reverse test point.
4. The switchable forward and reverse test point circuit of claim 1 , wherein the self-terminating switch includes a single pole double throw (SPDT) switch.
5. An RF amplifier for a communication system that transmits forward and reverse RF signals, the RF amplifier comprising:
a first port for receiving a forward signal and for outputting a reverse signal;
a second port for outputting the forward signal and for receiving the reverse signal;
a first diplex filter coupled to the first port for filtering signals at the first port to separate the forward signal for amplification;
a second diplex filter coupled to the second port for filtering signals at the second port to separate the reverse signal for amplification;
a first gain stage coupled between the first and second diplex filters for amplifying the forward signal;
a second gain stage coupled between the first and second diplex filters for amplifying the reverse signal;
at least one directional coupler coupled to at least one of the first port and the second port;
at least one switchable forward and reverse test point circuit coupled to forward and reverse terminals of the directional coupler, the switchable forward and reverse test point circuit comprising a test point and a switchable termination circuit configured to switch the forward and reverse terminals of the directional coupler between a termination and the test point; and
wherein the test point includes a single forward and reverse test point, and wherein the switchable termination circuit includes a self-terminating switch coupled between the reverse terminal and the forward terminal of the directional coupler and the single forward and reverse test point.
6. The RF amplifier of claim 5 , wherein the at least one directional coupler includes a first directional coupler coupled to the first port and a second directional coupler coupled to the second port, and wherein the at least one switchable forward and reverse test point circuit includes a first switchable forward and reverse test point circuit coupled to the forward and reverse terminals of the first coupler, and a second switchable forward and reverse test point circuit coupled to the forward and reverse terminals of the second coupler.
7. The RF amplifier of claim 5 , wherein the self-terminating switch includes a single pole double throw (SPDT) switch.
8. The RF amplifier of claim 5 , wherein switchable forward and reverse test point circuit further includes at least one attenuation and tilt network.
9. The RF amplifier of claim 5 , wherein the RF amplifier is configured to amplify forward RF signals at frequencies up to 1.8 GHz and to amplify reverse RF signals at frequencies up to 600 MHZ.