WO1997005705A1

WO1997005705A1 - Amps a-band single superhet

Info

Publication number: WO1997005705A1
Application number: PCT/SE1996/000961
Authority: WO
Inventors: Lars Henrik Bergman
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 1995-07-26
Filing date: 1996-07-17
Publication date: 1997-02-13
Also published as: AU6474796A

Abstract

A wideband receiver is provided for fully covering a desired band with only one mixer and one local oscillator. The wideband receiver advantageously utilizes the inherent aliasing characteristics of the sampling process taking place in the analog-to-digital converter to achieve full coverage of the desired band. More particularly, the wideband receiver is directed to fully covering the A-band of the AMPS frequency plan by analog-to-digitally converting two separate parts of a spectrum input to the wideband receiver where said spectrum has a total bandwidth greater than the Nyquist frequency of the analog-to-digital converter without any individual frequency transposition of each spectra part before being input to the analog-to-digital converter. The analog-to-digital converter aliases the transposed desired separate frequency bands to fulfill the Nyquist criteria even when a sampling frequency of the analog-to-digital converter is less than twice the bandwidth of the spectrum. As a result, the wideband receiver minimizes the number of analog parts used so that the wideband receiver is smaller, consumes less power and has a higher manufacturing yield.

Description

AMPS A-BAND SINGLE SUPERHET BACKGROUND The present invention is directed to a wideband receiver for providing full coverage of a desired band by advantageously utilizing aliasing characteristics of the sampling process. More particularly, the present invention is directed to a device and method for a wideband single superheterodyne (superhet) receiver for full A-band coverage in the Advanced Mobile Phone Service (AMPS) frequency plan with only one mixer and one local oscillator.

Presently, base station receivers for AMPS and D- AMPS are usually designed as double superheterodyne receivers which perform an analog downconversion of each individual narrowband (approximately 30 kHz) channel to a fixed (common for all channels) intermediate frequency. In other words, the same fixed intermediate frequency is used irrespective of which channel the receiver is tuned to. Analog-to-digital conversion of each narrowband channel is then performed and subsequent signal processing is done digitally.

An example of a conventional double superheterodyne receiver system for n channels is illustrated in Figure 1. In Figure 1, desired bands are received by a first bandpass filter 10 which is connected to first pairs of first local oscillators 20ι_, 2O₂, ...20_nand first mixers 30ι, 30₂, ...30_nso that each received channel is converted to a common fixed intermediate frequency. A plurality of second bandpass filters 40]_, 40₂, ...40_nare connected to the first mixers 30^, 30₂, ...30_n, respectively for passing through narrowband channels of approximately 30 kHz. The outputs of the second bandpass filters 40ι, 40₂, ...40_nare connected to second pairs of second local oscillators 50ι_, 50₂, ...50_nand second mixers 60^, 6O₂, ...60_nfor performing an analog down conversion of each individual narrowband channel from the second bandpass filters 40χ, 40₂, ...40_n. The outputs of the second mixers 60^, 6O₂, ...60_nare connected to a plurality of third bandpass filters 10χ , IO2 , ...70_n. Analog-to-digital converters 80τ_, 8O₂, ...80_n perform analog-to-digital conversion of each narrowband channel and then signal processing is performed digitally by a plurality of digital signal processors 90ι, 90₂, • • .90_n.

It is also known to use a wideband receiver in which the whole frequency spectra allocated to the operator is downconverted to a suitable intermediate frequency interval and then converted from analog to digital. The selection of each narrowband channel and further processing is then done digitally. Figure 2 illustrates an example of this conventional wideband receiver where a signal is input to a first bandpass filter 15 and then downconverted to the intermediate frequency interval by a local oscillator 25 and a mixer 35. The output of the mixer 35 is input to a second bandpass filter 45 and then converted to a digital signal by the analog-to-digital converter 85. The output of the analog-to-digital converter 85 is input to a plurality of digital signal processors 95χ, 952, •••⁹⁵n for further processing.

In the application of wideband receivers to the AMPS frequency plan, certain difficulties exist which prevent sufficient resolution from being achieved for the required dynamic range of the wideband receiver. To better illustrate these problems, an overview of the AMPS frequency is provided below in Table 1. TABLE 1

A" 824-825 MHZ (1 MHZ bandwidth)

A 825-835 MHZ (10 MHz)

B 835-845 MHz (10 MHz)

A' 845-846.5 MHz (1.5 MHz)

B' 846.5-849 MHz (2.5 MHz)

As seen in Table 1, the full A- or B-band utilizes 12.5 MHz bandwidth each. Because of the distribution of the bands, a wideband receiver needs to cover 22.5 MHz bandwidth (824-846.5 MHz) for the full A-band and 14 MHz bandwidth for full B-band coverage (835-849 MHz) , respectively. Because only the A- and B-bands were originally allocated for mobile telephone use, the later addition of the extended bands A''-, A'- and B'-bands caused the differences in the bandwidth which are necessary for fully covering the A- and B-bands.

To achieve full B-band coverage in a wideband receiver, a sampling frequency of at least 28 MHz (2 x 14 MHz, which is the bandwidth for full B-band coverage) is needed. The 28 MHz sampling frequency is within the limits of the present technology for sufficient resolution to achieve the required dynamic range for the wideband receiver. However, to achieve full A-band coverage, a sampling frequency of more than 45 MHz (2 x 22.5 MHz, the bandwidth for full A-band coverage) is required. This sampling frequency is beyond the present technology for an analog-to-digital converter with sufficient resolution.

In order to overcome this problem of insufficient resolution, a wideband receiver as illustrated in Figure 3, for example, has been proposed. In the wideband receiver of Figure 3, a first bandpass filter 100 receives the A' '^'-, A'- and A-bands and is connected to a pair of first local oscillator 110 and a firεt mixer 120 which frequency transpose the A-, A'-, and A' '-bands to an intermediate frequency band. The output of the first mixer 120 is connected to second and third bandpass filters 130 and 131 for passing the A- and A' '-bands and the A'-band therethrough, respectively. The outputs of the second and third bandpass filters 130 and 131 are connected to pairs of second and third local oscillators 140 and 141 and second and third mixers 150 and 151. The outputs of the second and third mixers 150 and 151 are input to fourth and fifth bandpass filters 160 and 161, respectively. The frequency of the second local oscillator 140 and the frequency of the third local oscillator 141 are chosen so that the A''- and A-bands, and the A'-band, respectively, are transposed to a nearly continuous frequency band having a total bandwidth of less than approximately 15 MHz. As a result, the required sampling frequency becomes 30 MHz (2 x the total bandwidth of approximately 15 MHz) . The nearly continuous frequency band is input to an analog- to-digital converter 170. The output of the analog-to- digital converter 170 is input to a plurality of digital signal processors 180^, I8O2, ...180_n. The frequencies of the second and third local oscillators 140 and 141 must be chosen so that a sufficient guardband is provided which prevents the requirements on the anti-aliasing filters from being too stringent.

Figure 4 illustrates another proposed solution which provides a sufficient resolution for the required dynamic range of the wideband receiver. In Figure 4, a first bandpass filter 105 receives the A-, A'-, and A''- bands and passes these bands through to a pair of a local oscillator 115 and a first mixer 125. The transposed A- and A' '-bands are input to a second bandpass filter 135 and the transposed A'-band is input to a third bandpass filter 136. The outputs of the second and third bandpass filters 135 and 136 are input to second and third mixers 155 and 156 which are connected to a common local oscillator 145 so that Fj__n- Fχ.₀from one mixer and FL_O- Finfrom the other mixer are used. The outputs of the second and third mixers 155 and 156 are input to fourth and fifth bandpass filters 165 and 166 to provide a nearly continuous frequency band to an analog-to-digital converter 175. The output of the analog-to-digital converter 175 is input to a plurality of digital signal processors 185ι, 185₂,

...185_n. In this wideband receiver, one of the bands iε inverted, while the other band is non-inverted, but the inverted band iε corrected by the digital signal processors 185ι, 185₂, ...185_n. In both of the wideband receivers proposed in

Figures 3 and 4, a double superhet receiver is used with three mixers and at least two local oscillators. The embodiments of the present invention are directed to a wideband single superheterodyne receiver which fully covers a desired band with only one mixer and one local oscillator.

SUMMARY An object of the present invention is to provide a wideband receiver which fully covers a desired bandwidth of frequencies. More particularly, the present invention is directed to a wideband εuperheterodyne receiver for providing full coverage of the deεired band with only one mixer and one local oscillator. Another object of the preεent invention is to utilize an analog-to-digital converter which converts two separate parts of a spectrum, where said spectrum has a total bandwidth greater than the Nyquist frequency of the analog-to-digital converter, and to take advantage of the aliasing characteristics during the sampling proceεε in a positive manner εo that the wideband receiver provides full coverage of the desired band. A still further object of the preεent invention is to provide full A-band coverage of the AMPS frequency plan by a wideband receiver having only one mixer and one local oscillator.

These objects of the present invention are fulfilled by providing a wideband receiver for full coverage of a desired band comprising a local oεcillator operating at a tranεpoεing frequency, a mixer connected to εaid local oscillator for receiving predetermined frequency bands and transposing said predetermined frequency bands to transposed frequency bands in responεe to εaid tranεpoεing frequency, and an analog- to-digital converter operating at a εa pling frequency for aliasing down said transposed frequency bands to achieve full coverage of the desired band. By using the aliaεing characteristics of the analog-to-digital converter in a positive manner, the wideband receiver provideε full A-band coverage with only one mixer and one local oscillator. Thereby the analog parts of the wideband receiver are minimized so that the wideband receiver is εmaller in size, consumeε leεε power and haε a high manufacturing yield.

The objects of the present invention are also fulfilled by a method for providing full coverage of a desired band with a wideband receiver comprising the stepε of operating a local oεcillator at a transposing frequency, receiving predetermined frequency bandε with a mixer and transposing said predetermined frequency bands to transposed frequency bands in response to said tranεpoεing frequency, and aliasing down said transposed frequency bands by an analog-to-digital converter operating at a sampling frequency to achieve full coverage of the desired band. This method similarly utilizes the inherent aliasing characteriεtics of this sampling procesε taking place in the analog-to-digital converter εo that full coverage of a deεired band is provided with only one mixer and one local oscillator.

Further scope of applicability of the present invention will become apparent from the detail deεcription given hereinafter. However, it εhould be understood that the detailed description and specific examples, all indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to thoεe εkilled in the art from thiε detailed deεcription.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illuεtration only, and thuε are not limitative of the preεent invention, wherein:

Figure 1 illustrates a conventional receiver εystem for n narrowband channels where each channel is proceεsed in a double superheterodyne receiver which converts each narrowband channel;

Figure 2 illustrates a conventional wideband receiver which converts the whole frequency spectra and performs digital processing for n narrowband channels; Figure 3 illustrates a proposed wideband receiver having three mixers and three local oscillators, making it possible to convert two separate parts of a spectrum into a nearly continuous frequency band with a bandwidth less than the original spectrum bandwidth;

Figure 4 illustrates a proposed wideband receiver having three mixers and two local oscillators, making it possible to convert two separate parts of a spectrum into a nearly continuous frequency band with a bandwidth less than the original spectrum bandwidth;

Figure 5 illustrates a wideband receiver for an embodiment of the present invention; and

Figure 6 illuεtrateε an example of a frequency plan for the wideband receiver used in an embodiment of the present invention.

DETAILED DESCRIPTION Figure 5 illustrateε a wideband receiver for an embodiment of the preεent invention. In thiε embodiment, a wideband, εingle εuperheterodyne receiver is provided for full coverage of a deεired band with only one mixer and one local oscillator. In Figure 5, a εpectrum is input to a firεt bandpaεε filter 200 which paεses through desired frequency bands. The desired frequency bands pasεing through the first bandpass filter 200 are input to a mixer 220. The mixer 220 is connected to a local oscillator 210 which operates the mixer 220 at a transpoεing frequency. By operating the mixer 220 at the tranεpoεing frequency, tranεpoεed frequency bandε are outputted from the mixer 220. The output of the mixer 220 iε input to εecond and third bandpaεs filters 230 and 240 for pasεing the transposed frequency bands therethrough. The transposed frequency bands are input to an analog-to-digital converter 250 which converts the transposed frequency bands to digital εignalε.

In the εampling process, the analog-to-digital converter 250 operates at a predetermined εampling frequency which aliaεes down the transposed frequency bands to inverted and non-inverted frequency bands. The output of the analog-to-digital converter 250 is input to a plurality of digital signal processors 260^, 26O₂, ...260_nfor further procesεing of the frequency bandε. The digital signal procesεorε 260;j_, 26O₂, ...260_ncan eaεily proceεε the inverted frequency band aliaεed down by the analog-to-digital converter 250. For simplicity, only the parts that are essential for the understanding of the function are shown in the figures and mentioned in the description (the filters, mixers, local oscillators, analog-to-digital converters) . However, in the actual implementation of the wideband receiver, various additional circuitry as would be obvious to one of ordinary skill in the art is neceεsary to ensure that sufficient signal-to-noise ratios are achieved, such as different amplifiers for example.

In the present embodiment, aliasing, which is uεually thought of aε an undesired property, is used in a positive manner to make it posεible to deεign a wideband receiver for fully covering a deεired band in a εpectrum with only one mixer and one local oscillator. The analog input spectra consiεtε of two deεired partε with bandwidthε Bi and B₂ respectively, separated by a non-desired band with bandwidth G_a, where Bi + G_a + B₂ > f_Nyq,and where f yqiε the Nyquist frequency of the analog-to-digital converter 250. The aliasing is used to digitally transpoεe the part with the bandwidth B2 εo that the digital (after analog-to-digital converεion) spectra consistε of two deεired parts with bandwidths Bi and B2 respectively, now εeparated by a non-desired band with bandwidth G^, where Bi + G^ + B₂ < fNyq- ^BY advantageously utilizing the aliasing characteristicε of the analog-to-digital converter 250, a sampling frequency can be used that is within the known limitations for present analog-to-digital converters (approximately 39 MHz) . Thereby, even when the sampling frequency iε less than twice the bandwidth of the spectrum, the Nyquist criteria is fulfilled by advantageously utilizing the aliasing characteristics.

When the desired band coverage is for the A-band of the AMPS frequency plan, for example, the wideband single superheterodyne receiver operateε aε will be deεcribed aε followε with reference to Figure 6. Thiε example iε used to only illustrate the operation of the wideband receiver for the present embodiment and other considerations muεt be taken into account when actually deεigning the wideband receiver, such as sample frequency versus data rate, anti-aliaεing filter εtructureε, etc. , which are neglected in thiε example. The full A-band iε input to the firεt bandpaεε filter 200 for paεεing through the A"-, A-, and A'-bands which include the frequencies of 824-835 and 845-846.5 MHz. These frequency bands are then input to the mixer 220 which is operated by the local oscillator 210 at the tranεpoεing frequency of 803 MHz and tranεpoεeε the A''- and A-bands to between the frequencieε of fi and f2 (corresponding to 21 and 32 MHz) and the A'-band to between the frequencieε of f3 and f4 (which correεponds to 42 and 43.5 MHz) as illustrated in Figure 6. The second bandpasε filter 230 paεses through the A- and A' '-bandε between 21 and 32 MHz and the third bandpaεs filter 240 paεεes through A'-band frequencieε between 42 and 43.5 MHz. With a sampling frequency of f_s = 39 MHz for the analog-to-digital converter 250, the A'-band is aliased down to between 3 and 4.5 MHz (non-inverted) and the A''- and A-bands are aliased down to between 7 and 18 MHz, inverted. Although it iε theoretically poεεible to use a εampling frequency of approximately 33.5 MHz in this example, the sampling frequency should be higher, near the 39 MHz used in this example, for practical purposeε to provide a sufficient guardband. The theoretical minimum sampling frequency can be calculated as follows. By placing f_s between f2 and f3 so that f3 - f_s= f_s- f2 - (f4 - f3) [Equation 1] the "A'-band of the εpectrum is made to alias around f_s without overlapping the A''- and A-bands. The A''- and A-bands alias around f1 such that fi = f^2 [Equation 2]. Thereby, Equation 1 can be rewritten as 2f_s= f2 + f4 = f2 - f1 + f4 - f1 + 2fχ [Equation 3]. Because 2f1 = f_s according to Equation 2, the relation f_s = f2 - f1 + f4 - f1 = 11 MHz + 22.5 MHz = 33.5 MHz for this example. The aliased down A-band iε included within the frequencieε from 3 to 18 MHz with a guardband between 4.5 and 7 MHz. The A- and A' '-bandε are inverted while the A'-band iε non-inverted, but the A- and A' '-bandε are eaεily proceεsed by the digital signal processors 260ι, 26O2, ...260_nwhich receive the output from the analog-to-digital converter 250. By utilizing the inherent aliasing characteriεtics of the sampling process which takes place in the analog- to-digital converter 250, a wideband superheterodyne receiver is provided for full A-band coverage with only one mixer and one local oscillator. More generally, by advantageously uεing the aliaεing characteristicε, a wideband receiver may be deεigned for fully covering a deεired band with only one mixer and one local oεcillator. Aε a reεult, the analog partε of the wideband receiver are minimized εo that the wideband receiver iε εmaller, conεumes less power, has a higher manufacturing yield and haε a reduced manufacturing coεt.

The invention being thus deεcribed, it would be obviouε that the εame may be varied in many ways. Such variations are not to be regarded aε a departure from the spirit and εcope of the invention, and all εuch modification as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

Claims

CLAIMS:

1. A wideband receiver for providing full coverage of desired separate frequency bands in a εpectrum, compriεing: a local oεcillator operating at a transposing frequency; a mixer connected to said local oεcillator for receiving the spectrum and transpoεing the εpectrum to a tranεposed spectrum in responεe to εaid tranεpoεing frequency; and an analog-to-digital converter for aliaεing εaid tranεpoεed εpectrum of the deεired εeparate frequency bandε to fulfill the Nyquiεt criteria when a εampling frequency of said analog-to-digital converter is less than twice the bandwidth of the spectrum.

2. A wideband receiver according to claim 1, further comprising a firεt bandpass filter for receiving the spectrum having a plurality of frequency bands and paεsing through the desired separate frequency bands.

3. A wideband receiver according to claim 1, further comprising a plurality of second bandpass filters for passing through said transposed spectrum.

4. A wideband receiver according to claim 1, wherein the deεired εeparate frequency bands comprise A- , A'- and A"-bands of the full A-band for the AMPS frequency plan.

5. A wideband receiver according to claim 4, wherein said analog-to-digital converter aliases down εaid A- and A' '-bandε together in an inverted manner and aliases down said A'-band in a non-inverted manner.

6. A wideband receiver according to claim 5, further comprising a plurality of digital signal procesεors for inverting said A- and A' '-bands and processing said A-, A'- and A''-bands.

7. A wideband receiver according to claim 1, further comprising a plurality of digital signal procesεorε for processing said transpoεed εpectrum after being aliased down by said analog-to-digital converter.

8. A wideband receiver according to claim 1, wherein the desired separate frequency bands are allocated in the spectrum where εaid spectrum has a total bandwidth greater than the Nyquist frequency of said analog-to-digital converter and the wideband receiver is a wideband single superheterodyne receiver.

9. A wideband receiver comprising: a local oscillator operating at a transposing frequency; a mixer connected to said local oscillator for transposing a spectrum of first and εecond bandwidths to a transposed spectrum of εaid firεt and εecond bandwidths in response to said transposing frequency; and an analog to digital converter for aliasing said transposed spectrum of said first and second bandwidths to fulfill the Nyquist criteria when a sampling frequency of said analog-to-digital converter is lesε than twice the bandwidth of the εpectrum.

10. A wideband receiver according to claim 9, wherein εaid first bandwidth comprises A- and A' '-bands and said second bandwidth compriseε an A'-band to provide full A-band coverage of the AMPS frequency plan.

11. A wideband receiver according to claim 9, further compriεing: a first bandpass filter for passing through said spectrum of said first and εecond bandwidths to said mixer; and a second bandpasε filter for paεεing through εaid tranεposed spectrum of said first and second bandwidths from said mixer to said analog-to-digital converter.

12. A wideband receiver according to claim 9, wherein said analog-to-digital converter aliaεeε down εaid tranεpoεed εpectrum for εaid firεt bandwidth in an inverted manner and εaid tranεposed spectrum for said second bandwidth in a non-inverted manner.

13. A wideband receiver according to claim 9, further comprising a plurality of digital signal processorε for inverting said transposed spectrum for said firεt bandwidth and processing said tranεpoεed εpectrum for said first and second bandwidths.

14. A wideband receiver for providing full A-band coverage of the AMPS frequency plan, compriεing: a local oεcillator operating at a tranεpoεing frequency; a mixer connected to εaid local oεcillator for receiving a εpectrum of A-, A'- and A' '-bands for the A- band and transposing said spectrum for said A- and A"- bandε to a first transposed spectrum and said spectrum for said A'-band to a second transposed spectrum; and an analog-to-digital converter for aliasing said first and second transpoεed εpectru ε for fulfill the Nyquiεt criteria when a sampling frequency of said analog-to-digital converter is lesε than twice the bandwidth of εaid εpectrum.

15. A wideband receiver according to claim 14, wherein said analog-to-digital converter aliaseε down said first transposed spectrum to an inverted spectrum and said second transposed spectrum to a non-inverted spectrum.

16. A wideband receiver according to claim 14, further comprising: a first bandpass filter for passing through said spectrum of said A-, A'- and A' '-bandε to εaid mixer; a second bandpass filter for passing through said firεt transposed spectrum from said mixer to said analog-to-digital converter; and a third bandpaεε filter for passing through said second transpoεed εpectrum from εaid mixer to εaid analog-to-digital converter.

17. A method for providing full coverage of deεired separate frequency bands in a spectrum by a wideband receiver, comprising the stepε of:

(a) operating a local oεcillator at a tranεpoεing frequency;

(b) receiving the εpectrum and tranεpoεing the εpectrum to a tranεpoεed spectrum in reεponεe to said transposing frequency by a mixer; and

(c) aliasing said transposed spectrum of the deεired εeparate frequency bandε by an analog-to-digital converter to fulfill the Nyquist criteria when a sampling frequency of said analog-to-digital converter iε leεε than twice the bandwidth of the εpectrum.

18. A method according to claim 17, further compriεing the εtepε of:

(d) receiving the εpectrum having a plurality of frequency bands by a firεt bandpass filter and passing through the deεired εeparate frequency bandε to εaid mixer; and

(e) receiving said spectrum from said mixer by a second bandpass filter and passing through the desired separate frequency bands to said analog-to-digital converter.

19. A method according to claim 17, wherein the εpectrum comprises a first frequency band for A- and

A' '-bands and a second frequency band for an A'-band of the full A-band for the AMPS frequency plan.

20. A method according to claim 19, wherein said step (c) aliaεes down said first frequency band in an inverted manner and said second frequency band in a non- inverted manner.

21. A method according to claim 20, further comprising the steps of inverting said first frequency band and procesεing εaid first and second frequency bandε by a plurality of digital εignal proceεεorε.

22. A method for providing full coverage of deεired εeparate frequency bandε in a spectrum by a wideband receiver comprising the stepε of:

(a) operating a local oscillator at a transpoεing frequency;

(b) receiving the εpectrum of first and second bandwidths and transpoεing the εpectrum of εaid first and second bandwidths to a tranεpoεed εpectrum of said first and second bandwidthε in reεponse to said transposing frequency;

(c) aliasing said transposed spectrum of said firεt and second bandwidths by an analog-to-digital converter to fulfil the Nyquist criteria when a sampling frequency of said analog-to-digital converter is less than twice the bandwidth of the spectrum.

23. A method according to claim 22, wherein said firεt bandwidth compriεes A- and A' '-bands and said εecond bandwidth comprises an A' band to provide full A- band coverage of the AMPS frequency plan.

24. A method according to claim 22, further comprising the stepε of:

(d) receiving the εpectrum of εaid firεt and second bandwidths and pasεing through εaid first and second bandwidths to said mixer; and

(e) receiving said transposed spectrum of εaid firεt and εecond bandwidths from said mixer and paεεing through εaid tranεpoεed εpectrum of εaid firεt and εecond bandwidthε from εaid mixer to εaid analog-to- digital converter.

25. A method according to claim 22, wherein εaid εtep (c) aliases down said tranεposed spectrum for said firεt bandwidth in an inverted manner and aliases down said transpoεed εpectrum for εaid εecond bandwidth in a non-inverted manner.

26. A method according to claim 22, further compriεing the εtepε of inverting εaid transposed spectrum for said first bandwidth and proceεεing said transpoεed εpectrum for said first and second bandwidths by a plurality of digital signal processorε.

27. A method for providing full A-band coverage of the AMPS frequency plan by a wideband receiver compriεing the εtepε of: (a) operating a local oεcillator at a tranεpoεing frequency;

(b) receiving a spectrum of A-, A'- and A' '-bands of the A-band with a mixer and transpoεing εaid εpectrum for εaid A- and A' '-bandε to a first transposed spectrum and εaid εpectrum for εaid A'-band to a εecond transposed spectrum; and

(c) aliasing said first and second transposed spectrumε to fulfill the Nyquiεt criteria when a sampling frequency of said analog-to-digital converter is lesε than twice the bandwidth of εaid εpectrum.

28. A method according to claim 27, wherein εaid εtep (c) aliaεes down said first transpoεed spectrum to an inverted spectrum and said εecond tranεposed εpectrum to a non-inverted spectrum.

29. A method according to claim 27, further comprising the stepε of:

(d) receiving εaid εpectrum of εaid A-, A'- and

A' '-bandε by a firεt bandpaεε filter and paεεing through said spectrum of said A-, A'- and A' '-bands to said mixer;

(e) receiving εaid εpectrum of said A- and A''- bandε from εaid mixer by a εecond bandpaεε filter and paεεing through said first tranεposed spectrum to said analog-to-digital converter; and (f) receiving said εpectrum of εaid A'-band from εaid mixer by a third bandpass filter and pasεing through εaid εecond transposed spectrum to said analog- to-digital converter.