# US 6,724,828 B1 · Mobile switching between STTD and non-diversity mode > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,724,828 B1 - Document ID: US6724828B1 - Status: Granted - Kind: B1 - Application number: 09/303,018 - Filed: 1999-04-30 - Granted: 2004-04-20 - Earliest claimed: 1999-01-19 - Assignees: Texas Instruments Incorporated - Inventors: Anand G. Dabak - Web page: https://patentgrep.com/patent/US6724828B1 ## CPC - H04B 7/0669: {using different channel coding between antennas (space-time coding H04L1/0618)} - H04L 1/0001: {Systems modifying transmission characteristics according to link quality, e.g. power backoff (adaptive data allocation for multicarrier modulation H04L5/0044; controlling transmission power for radio systems H04W52/04)} - H04L 1/0618: {Space-time coding} - H04B 7/0689: {using different transmission schemes, at least one of them being a diversity transmission scheme} - H04L 1/0021: {in which the algorithm uses adaptive thresholds} - H04L 1/0025: {Transmission of mode-switching indication} - H04B: TRANSMISSION - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A communication circuit is designed with a detector circuit (720) coupled to receive a first signal. The detector circuit is arranged to produce a multipath signal corresponding to a number of paths of the first signal. A comparator circuit (726) is coupled to receive the multipath signal and a threshold signal. The comparator circuit is arranged to produce a diversity signal in response to a comparison of the multipath signal and the threshold signal. The diversity signal has a first logic state for enabling diversity and has a second logic state for disabling diversity. ## Claims ### Claim 1 A communication circuit, comprising: a detector circuit coupled to receive a first signal, the detector circuit arranged to produce a multipath signal corresponding to a number of paths of the first signal; and a comparator circuit coupled to receive the multipath signal and a threshold signal, the comparator circuit arranged to produce a diversity signal in response to a comparison of the multipath signal and the threshold signal, the diversity signal having a first logic state for enabling diversity and having a second logic state for disabling diversity. ### Claim 2 (depends on 1) A communication circuit as in claim 1, wherein the number of paths comprises multiple signal paths from a plurality of antennas of a base station. ### Claim 3 (depends on 1) A communication circuit as in claim 1, wherein the multipath signal further corresponds to an estimated gain of the first signal in response to at least one of transmit diversity and no transmit diversity. ### Claim 4 (depends on 1) A communication circuit as in claim 1, wherein the multipath signal further corresponds to received power of the first signal. ### Claim 5 (depends on 1) A communication circuit as in claim 1, wherein the threshold signal is programmable. ### Claim 6 (depends on 5) A communication circuit as in claim 5, wherein the threshold signal has a first value corresponding to the first logic state of the diversity signal and a second value corresponding to the second logic state of the diversity signal. ### Claim 7 (depends on 1) A communication circuit as in claim 1, wherein the first logic state of the diversity signal directs a base station to transmit from a plurality of antennas and wherein the second logic state of the diversity signal directs the base station to transmit from a single antenna. ### Claim 8 (depends on 1) A communication circuit as in claim 1, wherein the first logic state of the diversity signal directs a base station to transmit from a plurality of antennas and wherein the second logic state of the diversity signal directs the base station to transmit a same signal from a plurality of antennas. ### Claim 9 (depends on 1) A communication circuit as in claim 1, wherein the first logic state for enabling diversity comprises enabling STTD. ### Claim 10 A communication circuit coupled to receive a diversity signal, the communication circuit comprising: an encoder circuit coupled to receive a first signal, the encoder circuit arranged to produce a second signal comprising at least one of a complement and a conjugate of the first signal; and an output circuit arranged to produce the first signal and the second signal in response to a first logic state of the diversity signal, the output circuit arranged to produce the first signal and not produce the second signal in response to a second logic state of the diversity signal. ### Claim 11 (depends on 10) A communication circuit as in claim 10, further comprising a modulator circuit coupled to receive the first and second signals, the modulator circuit arranged to modulate each of the first and second signals with a channel orthogonalization code. ### Claim 12 (depends on 10) A communication circuit as in claim 10, wherein the diversity signal is received from a mobile transmitter. ### Claim 13 (depends on 10) A communication circuit as in claim 10, wherein first and second signals are STTD signals. ### Claim 14 (depends on 10) A communication circuit as in claim 10, wherein the output circuit comprises a transmit circuit, the transmit circuit arranged to produce the first signal from a first antenna and the second signal from a second antenna in response to the first logic state of the diversity signal, the transmit circuit arranged to produce the first signal from the first antenna and not produce the second signal from the second antenna in response to the second logic state of the diversity signal. ### Claim 15 (depends on 14) A communication circuit as in claim 14, wherein the transmit circuit produces the first signal from the second antenna when it does said not produce the second signal from the second antenna. ### Claim 16 (depends on 14) A communication circuit as in claim 14, wherein the transmit circuit does not produce a signal from the second antenna when it does said not produce the second signal from the second antenna. ### Claim 17 A method of switching between diversity and non-diversity modes in a communication circuit, comprising the steps of: receiving a first signal from a source external to the communication circuit; producing a multipath signal corresponding to a number of paths of the first signal from a plurality of transmit antennas at the source external; comparing the multipath signal to a threshold signal; producing a diversity signal having a first value when the multipath signal is greater than the threshold signal; and producing a diversity signal having a second value different from the first value when the multipath signal is less than the threshold signal. ### Claim 18 A method of switching between diversity and non-diversity modes in a communication circuit, comprising the steps of: receiving a first signal from a source external to the communication circuit; producing a multipath signal corresponding to a number of paths of the first signal from the source external; comparing the multipath signal to a threshold signal; producing a diversity signal having a first value when the multipath signal is greater than the threshold signal and transmitting the diversity signal to the source external; and producing a diversity signal having a second value different from the first value when the multipath signal is less than the threshold signal and transmitting the diversity signal to the source external.