Beamforming in radio frequency communication systems using frequency division duplexing
Beamforming in radio frequency (RF) communication systems using frequency division duplexing (FDD) are provided. In certain embodiments, a front end system includes a first transmit path configured to process a first radio frequency transmit signal of a frequency band, the transmit path including a power amplifier and a transmit filter having a passband that passes an uplink frequency range of the frequency band, and a receive path configured to process a first radio frequency receive signal of the frequency band. The receive path includes a low noise amplifier, a switch, and a receive filter having a passband that passes a downlink frequency range of the frequency band, and the switch has a first state in which an input of the low noise amplifier is coupled to the receive filter and a second state in which an output of the power amplifier is coupled to the receive filter.
1 . A front end system for a mobile phone, the front end system comprising:
a first transmit path configured to process a first radio frequency transmit signal of a frequency band, the transmit path including a power amplifier configured to amplify the first radio frequency transmit signal to generate a first amplified radio frequency transmit signal and a transmit filter having a passband that passes an uplink frequency range of the frequency band; and
a receive path configured to process a first radio frequency receive signal of the frequency band, the receive path including a low noise amplifier, a switch, and a receive filter having a passband that passes a downlink frequency range of the frequency band, the switch having a first state in which an input of the low noise amplifier is coupled to the receive filter and a second state in which an output of the power amplifier is coupled to the receive filter, the receive filter providing the first amplified radio frequency transmit signal from the power amplifier to an antenna in the second state of the switch, the front end system operable in a frequency division duplexing mode in which the front end system simultaneously sends a transmit beam on the uplink frequency range of the frequency band and receives a receive beam on a downlink frequency range of the frequency band.
2 . The front end system of claim 1 further configured to set the switch in the second state to transmit the first amplified radio frequency transmit signal on the downlink frequency range to aid in acquiring the receive beam as part of beamforming the receive beam on the downlink frequency range in the frequency division duplexing mode.
3 . The front end system of claim 1 wherein the switch is a crossbar switch operable to couple the input of the low noise amplifier to the transmit filter in the second state.
4 . The front end system of claim 1 wherein the front end system is further operable in a first time division duplexing mode in which the transmit beam and the receive beam are sent on a first common frequency using time division duplexing, and a second time division duplexing mode in which the transmit beam and the receive beam are sent on a second common frequency using time division duplexing.
5 . The front end system of claim 4 wherein the first common frequency for time division duplexing is the uplink frequency range and the second common frequency is the downlink frequency range.
6 . The front end system of claim 1 further comprising a common antenna port connecting the transmit filter and the receive filter to the antenna.
7 . The front end system of claim 1 further comprising a first antenna port connected to the transmit filter and a second antenna port connected to the receive filter and the antenna.
8 . The front end system of claim 1 further comprising a transmit-path phase shifter along the transmit path and a receive-path phase shifter along the receive path.
9 . A mobile device comprising:
an antenna;
a transceiver configured to generate a plurality of radio frequency transmit signals including a first radio frequency transmit signal, and to receive a plurality of radio frequency receive signals including a first radio frequency receive signal; and
a front end system coupled to the transceiver and configured to provide beamforming in a frequency band using frequency division duplexing, the front end system including a first signal conditioning circuit including a transmit path configured to process the first radio frequency transmit signal and a receive path configured to process the first radio frequency receive signal, the receive path including a low noise amplifier, a switch, and a receive filter having a passband that passes a downlink frequency range of the frequency band, the transmit path including a power amplifier configured to amplify the first radio frequency transmit signal to generate a first amplified radio frequency transmit signal and a transmit filter having a passband that passes an uplink frequency range of the frequency band, the switch having a first state in which an input of the low noise amplifier is coupled to the receive filter and a second state in which an output of the power amplifier is coupled to the receive filter, the receive filter providing the first amplified radio frequency transmit signal from the power amplifier to the antenna in the second state of the switch, the front end system operable in a frequency division duplexing mode in which the front end system simultaneously sends a transmit beam on the uplink frequency range of the frequency band and receives a receive beam on a downlink frequency range of the frequency band.
10 . The mobile device of claim 9 wherein the transceiver is configured to set the switch in the second state to transmit the first amplified radio frequency transmit signal on the downlink frequency range to aid in acquiring the receive beam as part of beamforming the receive beam on the downlink frequency range in the frequency division duplexing mode.
11 . The mobile device of claim 9 wherein in the second state the power amplifier and the receive filter operate to transmit the first radio frequency transmit signal over the downlink frequency range.
12 . The mobile device of claim 11 in communication with a base station that calibrates the receive beam based on the transmission of the first radio frequency transmit signal over the downlink frequency range.
13 . The mobile device of claim 9 wherein the switch is a crossbar switch operable to couple the input of the low noise amplifier to the transmit filter in the second state.
14 . The mobile device of claim 9 wherein the front end system is further operable in a first time division duplexing mode in which the transmit beam and the receive beam are sent on a first common frequency using time division duplexing, and and a second time division duplexing mode in which the transmit beam and the receive beam are sent on a second common frequency using time division duplexing.
15 . The mobile device of claim 14 wherein the first common frequency for time division duplexing is the uplink frequency range and the second common frequency for time division duplexing is the downlink frequency range.
16 . The mobile device of claim 9 wherein the transceiver is configured to control the front end system to emulate the mobile phone as a base station communicating using frequency division duplexing in the frequency band.
17 . The mobile device of claim 9 wherein the transceiver is operable to control a gain setting and a phase setting for each of the transmit path and the receive path to control beamforming.
18 . A method of beamforming in a mobile phone, the method comprising:
forming a transmit beam, including processing a first radio frequency transmit signal of a frequency band using a transmit path through a first signal conditioning channel of a front end system, the transmit path including a power amplifier that amplifies the first radio frequency transmit signal to generate a first amplified radio frequency transmit signal and a transmit filter having a passband that passes an uplink frequency range of the frequency band;
forming a receive beam, including processing a first radio frequency receive signal of the frequency band using a receive path through a second signal conditioning channel of the front end system, the receive path including a low noise amplifier, a switch, and a receive filter having a passband that passes a downlink frequency range of the frequency band;
setting the switch in a first state in which an input of the low noise amplifier is coupled to the receive filter;
setting the switch in a second state in which an output of the power amplifier is coupled to the receive filter, the receive filter providing the first amplified radio frequency transmit signal from the power amplifier to an antenna in the second state of the switch; and
operating the front end system in a frequency division duplexing mode in which the front end system simultaneously sends the transmit beam on the uplink frequency range of the frequency band and receives the receive beam on a downlink frequency range of the frequency band.
19 . The method of claim 18 further comprising setting the switch in the second state to transmit the first amplified radio frequency transmit signal on the downlink frequency range to aid in acquiring the receive beam as part of beamforming the receive beam on the downlink frequency range in the frequency division duplexing mode.
20 . The method of claim 18 further comprising operating the front end system in a first time division duplexing mode in which the transmit beam and the receive beam are sent on a first common frequency using time division duplexing, and operating the front end system in a second time division duplexing mode in which the transmit beam and the receive beam are sent on a second common frequency using time division duplexing.