Dual-mode radio architecture

• US 6,256,511 B1
• Filed: 04/22/1999
• Issued: 07/03/2001
• Est. Priority Date: 02/16/1996
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Brown, David Alan, Edwards, Fraser Murray, Nisbet, John Jackson, Ansorge, Christian
• Primary Examiner(s): Chang, Vivian
• Assistant Examiner(s): APPIAH, CHARLES NANA
• Application Number:
  US09/117,906
• Time in Patent Office: 803 Days
• Field of Search: 455/553, 455/552, 455/76, 455/118, 455/313, 455/314, 455/315, 455/84
• US Class Current: 455/552.1
• CPC Class Codes: H04B 1/005 adapting radio receivers, transmitters andtransceivers for operation on two or more bands, i.e. frequency ranges
• CPC Class Codes: H04B 1/0057 using diplexing or multiplexing filters for selecting the desired band
• CPC Class Codes: H04B 1/006 using switches for selecting the desired band H04B1/0057 takes precedence
• CPC Class Codes: H04B 1/406 with more than one transmission mode, e.g. analog and digital modes
• CPC Class Codes: H04B 1/52 Hybrid arrangements, i.e. arrangements for transition from single-path two-direction transmission to single-direction transmission on each of two paths or vice versa
• CPC Class Codes: H04B 1/56 with provision for simultaneous communication in two directions

Abstract

This invention relates to a radio transceiver operable in multiple modes. The transceiver is operable, in one embodiment, to communicate with digital and analogue modulation format cellular radio systems. The handset utilizes a novel frequency plan and architecture to enable a minimum level of complexity for dual-moe operation. The frequency plan preferably uses two local oscillators 1LO, 2LO to general all the required frequencies for both the digital and analogue modulation format transceivers, derived from a single reference crystal oscillator. A radio architecture is used to enable switchable dual-mode operation with maximum commonality of functional blocks to facilitate silicon integration.

Claims

1. A radio front end transceiver operable to receive and transmit radio signals in different frequency bands and modulation formats, the transceiver comprising:

(i) a first receive path arranged to receive signals of a first modulation format at a first radio frequency band;

(ii) a second receive path arranged to receive signals of a second different modulation format at a second different radio frequency band;

(iii) a first transmit path arranged to transmit signals of the first modulation format and first radio frequency band;

(iv) a second transmit path arranged to transmit signals of the second modulation format and second radio frequency band;

(v) circuitry for conversion between the respective radio frequency band and an intermediate frequency provided in each of the paths;

(vi) intermediate frequency circuitry for conversion between the respective intermediate frequency and baseband provided in each of the paths, wherein at least some of the intermediate frequency circuitry is common to both receive paths and at least some of the intermediate frequency circuitry is common to both transmit paths; and

wherein the intermediate frequencies are different for the different modulation formats;

said intermediate frequency circuitry comprising separate channel filters for the different modulation formats and wherein the transceiver further comprises;

(vii) a dual loop frequency synthesiser arranged to derive local oscillator frequency bands suitable for use by the intermediate frequency circuitry on each of the paths; and

wherein the transmit and receive local oscillator frequency bands are arranged to overlap, by switching intermediate frequencies, whereby the tuning range is limited.

2. A radio front end transceiver according to claim 1, wherein the single dual loop frequency synthesiser is further arranged to derive local oscillator requirements for use by the circuitry for converting the signals between the radio frequency bands and the intermediate frequency bands.

3. A radio front end transceiver according to claim 1 wherein a single first local oscillator is operable for the radio frequency to intermediate frequency conversion, the first local oscillator arranged to receive control signals relating to the input frequency band and modulation format and signals from a feedback loop incorporating a programmable divider.

4. A radio front end transceiver according to claim 3 wherein said dual loop frequency synthesiser comprises a first local loop which is arranged to derive the local oscillator frequency bands for the transmit and receive paths such that those bands overlap.

5. A radio front end transceiver according to a claim 1 wherein the transceiver comprises a single second local oscillator 2LO, wherein in the receive path, the required baseband frequency signals are obtained by mixing the intermediate frequency signals with signals derived from integer division of the second local oscillator output.

6. A radio front end transceiver according to claim 1 wherein two first local oscillators are operable for the radio frequency to intermediate frequency conversion, each first local oscillator receiving an input from the dual loop frequency synthesiser.

7. A radio front end transceiver according to any one of claims 1, 2, 5 and 6, wherein the transceiver is provided with a means to ascertain the frequency band and modulation format.

8. A mobile radio handset incorporating a radio front end transceiver in accordance with claim 1.

9. A method of operating a radio front end transceiver as claimed in claim 1 said method comprising the steps of:

(i) receiving radio signals;

(ii) converting the radio signals to signals at an intermediate frequency band;

(iii) converting the intermediate frequency band signals to baseband signals.

10. A method of operating a radio front end transceiver as claimed in claim 1 comprising the steps of:

(i) obtaining baseband signals;

(ii) converting the baseband signals to an intermediate frequency band; and

(iii) converting the intermediate frequency band signals to radio signals and transmitting the radio signals.

11. A dual mode radio transceiver comprising several circuits and operable according to two frequency band and modulation formats,

wherein, in a common first circuit, disparate radio air interface signals are downconverted, with a first local oscillator, and filtered with switched separate intermediate frequency filters, amplified and converted using a second local oscillator, to in-phase and quadrature baseband signals, wherein, in a second circuit, disparate baseband modulation format in-phase and quadrature signals are upconverted to their respective disparate radio air interface signals in a common circuit configured as a phase lock loop upconverting modulator, which uses the first local oscillator common to the first circuit and a frequency reference derived from the second local oscillator,

wherein, the frequency synthesis is arranged so that only two phase locked voltage controlled oscillators are required, and such that in the receive path intermediate frequency signals are mixed with signals derived from integer division of the second local oscillator output, the second local oscillator being itself phase locked to the frequency reference, and the first local oscillator frequencies all derived from the same frequency reference, with the higher frequency radio system local oscillator bands arranged to overlap, by switching intermediate frequencies, whereby the tuning range is limited.