Programmable echo cancellation filter

The programmable echo cancellation filter as claimed in one of the preceding claims,

• wherein
• the controllable switches (66) are MOSFET transistors having controllable gate terminals.

The programmable echo cancellation filter as claimed in one of the preceding claims,

• wherein
• a capacitor (58) is provided, which is connected to a low-impedance node (61) of the echo cancellation filter (14).

The programmable echo cancellation filter as claimed in one of the preceding claims,

• wherein
• the controllable switches (66) of the first programmable resistor circuit (48) are connected to the signal input (38) of the operational amplifier (39) as virtual ground terminal.

The programmable echo cancellation filter as claimed in one of the preceding claims,

• wherein
• the controllable switches (66) of the second programmable resistor circuit (51) and the controllable switches (66) of the third programmable resistor circuit (55) are connected to the signal input (27) of an operational amplifier (28) of an automatic gain control circuit of the transceiver (1).

The programmable echo cancellation filter as claimed in one of the preceding claims,

• wherein
• the echo cancellation filter (14) is supplied with a low supply voltage.

The programmable echo cancellation filter as claimed in one of the preceding claims,

• wherein
• the echo cancellation filter (14) is of fully differential construction.

The programmable echo cancellation filter as claimed in one of the preceding claims,

• wherein
• the echo cancellation filter (14) is a first-order analog low-pass filter.

The programmable echo cancellation filter as claimed in one of the preceding claims,

• wherein
• the echo cancellation filter (14) is a higher-order analog low-pass filter.

The programmable echo cancellation filter as claimed in one of the preceding claims,

• wherein
• the signal input (13) of the echo cancellation filter (14) is connected to a signal matching circuit (11) for signal matching of the transmission signal.

The programmable echo cancellation filter as claimed in one of the preceding claims,

• wherein
• the signal output (15) of the echo cancellation filter (14) is connected to an automatic gain control circuit in the reception signal path of the transceiver (1).

The programmable echo cancellation filter as claimed in one of the preceding claims,

• wherein
• the resistors contained in the programmable resistor circuits (48, 51, 55) have weighted resistances.

The programmable echo cancellation filter as claimed in one of the preceding claims,

• wherein
• the gain (H1) of the echo cancellation filter (14) is adjustable in a frequency range lying below the first cut-off frequency (fU) and
• the gain (H2) of the echo cancellation filter (14) is adjustable in a frequency range lying above a second cut-off frequency (fo), by the control circuit (21).

The programmable echo cancellation filter as claimed in one of the preceding claims,

• wherein
• the two cut-off frequencies (fU, fo) of the echo cancellation filter (14) are adjustable by the control circuit (21).