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Direct-conversion transmitting circuit and integrated transmitting/receiving circuit

a transmission circuit and direct-conversion technology, applied in transmission, multiple carrier systems, amplitude to angle modulation conversion, etc., can solve the problem of cost reduction limit, achieve high performance, reduce the number of parts thereof, and restrict the effect of cost reduction

Inactive Publication Date: 2007-01-25
TANAKA SATOSHI +6
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The solution effectively suppresses noise in the receiving band without external filters, reducing component costs and complexity, while maintaining performance by using low-pass filters to damp wide-band noise generated by attenuators, thus achieving noise levels compliant with GSM specifications without the need for SAW filters.

Problems solved by technology

However, in the transmitter applying the offset PLL, there has been the limit of cost reduction because an external VCO with low noise is required.

Method used

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  • Direct-conversion transmitting circuit and integrated transmitting/receiving circuit
  • Direct-conversion transmitting circuit and integrated transmitting/receiving circuit
  • Direct-conversion transmitting circuit and integrated transmitting/receiving circuit

Examples

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first embodiment

[0034] A first embodiment of the present invention will be described with reference to FIGS. 1 to 8 and FIG. 19. In this embodiment, similarly to a conventional example, European cellular phone GSM (900 MHz band) and GSM1800 (1800 MHz band) are targeted as applications. Although there has already been given in the description of the conventional technique, a noise level from a transmitter within receiving band that the GSM specification should satisfy has been shown in FIG. 2. FIG. 3 shows conditions that the GSM1800 should satisfy. A transmission band (TX Band) 303 is within the range of 1710 to 1785 MHz, and a receiving band (RX Band) 304 is within a range of 1805 to 1880 MHz. Therefore, similarly to the case of the GSM, there is an interval of 20 MHz. It is required to suppress a noise of −71 dBm / 100 kHz (−121 dBm / Hz) or less in order to satisfy an allowed spur level 302 in receiving band relative to a maximum transmission power of 30 dBm in an output signal 301 of the GSM1800. T...

second embodiment

[0052] A second embodiment of the present invention will be described with reference to FIG. 9 and FIG. 10. In an example of the first embodiment described above, there is shown characteristics of the case where the first order filter is connected immediately before the mixer. Although it is desirable that the cutoff frequency is lowered to reduce noise in receiving band, such noise reduction is limited because the phase precision is affected by a group delay deviation which the filter has. Thus, in the present embodiment, an attempt is made to ensure damping quantity in receiving band and suppression of the group delay deviation in signal band by using a high order filter.

[0053]FIG. 9A shows respective amplitude characteristics of a first order low-pass filter 90a, a second order Butterworth filter 90b, and a third order Butterworth filter 90c. The characteristics of the first order low-pass filter in the cutoff frequency is 440 kHz, wherein the first order low-pass filter is set ...

third embodiment

[0057] A third embodiment of the present invention will be described with reference to FIG. 11. The same components as FIG. 1 are denoted by the same reference number as FIG. 1. The present embodiment relates to reduction of a carrier leak generated by an effect of a DC offset of a mixer circuit input in respective circuit constitutions of the first and second embodiments described above. In a direct-conversion transmitting circuit that is the present invention, since many circuits such as a filter, a attenuator and the like are connected to a mixer input, increase in a DC offset generated at a mixer input terminal is considered. As a countermeasure thereof, a circuit constitution of the present embodiment is proposed.

[0058] First, a mixer carrier leak will be described here. This mixer functions as a multiplier. As shown in formula (1), a modulation wave fc(t) is generated by multiplying a baseband input signal f(t) and a local signal cos(2πfc).

fc(t)=f(t)×cos(2πfc)   (1)

[0059] W...

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Abstract

A transmitter is provided which includes a transmitting circuit that does not require a high-performance low noise VCO restricting cost reduction thereof and that can reduce the number of parts without requiring an RF filter. A direct conversion that does not require a transmission VCO is applied to the transmitting circuit. In order to achieve noise reduction in a receiving band, low-pass filters are provided at IQ input sections of a modulator that converts IQ signals into RF signals. In comparison with a conventional transmitter using offset PLL, an external VCO required in addition to an RF integrated circuit, a power amplifier, and a front end circuit is reduced. Even in current transistor performance, by using a filter having rapid waveform characteristics such as a SAW more inexpensive than the VCO, or the like, it is possible to provide a GSM / GSM 1800 / GSM1900 triple band transmitter.

Description

[0001] This is a continuation application of U.S. application Ser. No. 10 / 073,029, filed Feb. 12, 2002, the entire disclosure of which is hereby incorporated by reference.BACKGROUND OF THE INVENTION [0002] The present invention relates to mobile communication equipment, and particularly to a direct-conversion transmitting circuit suitable for large scale integration and to an integrated transmitting / receiving circuit using the same. [0003] According to rapid spread of the mobile communication equipment, requests for miniaturization and lower cost thereof have increased. Because of this, it is expected to apply a voltage control type oscillator (VCO), or an integrated circuit whose filter number is reduced and whose integration is enhanced. What is given as one conventional example of transmitting equipment is “RF Circuits Technique of Dual-Band Transceiver IC for GSM and DCS1800 applications” published in pages 278 to 281 of manuscripts for IEEE 25th European Solid-State Circuits Co...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H04B1/04H01Q11/12H04L27/36H03C3/40H03D7/14H04B1/40
CPCH03C3/40H03D7/1433H03D7/145H03D2200/0047H03D2200/0025H03D2200/0033H03D2200/0043H03D7/1458
Inventor TANAKA, SATOSHITANABE, MASAMICHIOKUMA, YASUYUKIYAMAWAKI, TAIZOYAHAGI, KOICHIMATSUI, HIROAKIHENSHAW, ROBERT ASTLE
Owner TANAKA SATOSHI